Historical theology. Historical geology: basic science, founding scientists, literature review. Historical geology with basics of paleontology and astronomy
PREFACE................................................... ........................................................ ........................... 3
INTRODUCTION........................................................ ........................................................ ...................................... 4
PART I BASIC PRINCIPLES AND METHODS OF HISTORICAL GEOLOGY 7
CHAPTER 1. SUBJECT AND TASKS OF HISTORICAL GEOLOGY.................................... 7
CHAPTER 2. STRATIGRAPHY AND GEOCHRONOLOGY.................................................... ............ 14
2.1. TYPES OF STRATIGRAPHIC UNITS AND CRITERIA FOR THEIR IDENTIFICATION 16
2.2. RELATIVE GEOCHRONOLOGY.................................................... ............. 18
2.3. ABSOLUTE GEOCHRONOLOGY.................................................... .................... 36
2.4. INTERNATIONAL GEOCHRONOLOGICAL SCALE.............................................. 41
2.5. STANDARDS OF STRATIGRAPHIC UNITS.................................... 42
CHAPTER 3. BASIC METHODS OF HISTORICAL AND GEOLOGICAL ANALYSIS 47
3.1. FACIAL METHOD................................................... ........................................... 48
3.2. ANALYSIS OF PALEONTOLOGICAL MATERIAL (BIOFACIAL AND PALEOECOLOGICAL ANALYSIS)......................................................... ........................................................ ................................ 54
33. PALEOGEOGRAPHICAL METHODS.................................................................. .................... 57
3.4. FORMATIONAL ANALYSIS.................................................... .................................. 77
3.5. PALEOGEOGRAPHICAL MAPS.................................................................. .................... 79
PART II. ANCIENT HISTORY OF THE EARTH.................................................... ............... 82
CHAPTER 4. THE EMERGENCE OF THE EARTH AND PRE-ARCHEAN HISTORY.................................. 82
4.1. FORMATION OF THE SOLAR SYSTEM............................................................ ........ 82
4.2. FORMATION OF PLANETS, CONDENSATION AND ACCUMULATION OF INTERSTELLAR MATTER 84
4.3. PRE-ARCHEAN (HADEAN) STAGE OF EARTH DEVELOPMENT.................................... 86
CHAPTER 5. ARCHAEAN HISTORY.................................................... ........................................ 88
5.1. GENERAL DIVISION OF THE PRECAMBRIAN.................................................... ............... 88
5.2 EARLY ARCHEAN (4.0-3.5 billion years).................................... ................................... 90
5.3. MIDDLE AND LATE ARCHEAN (3.5-2.5 billion years)................................................. ....... 98
5.4. GEOLOGICAL SETTINGS IN THE ARCHEAN.................................................... ... 106
5.5. THE ORIGIN OF LIFE................................................... ........................................... 108
5.6. MINERALS................................................ ................................ 109
6.2. SEDIMENTATION ENVIRONMENT.................................................... ........................ 121
6.3. MINERALS................................................ ................................ 122
CHAPTER 7. LATE PROTEROZOIC.................................................... ................................... 123
7.1. STRATIGRAPHIC DIVISION AND STRATOTYPES.................................... 123
7.2. ORGANIC WORLD................................................... ............................................... 129
7.3. PALEOTECTONIC AND PALEOGEOGRAPHIC CONDITIONS.. 129
7.4. CLIMATIC ZONING................................................................. ............... 141
7. 5. MINERAL RESOURCES.................................................. ................................... 142
PART III PHANEOZOIC HISTORY OF THE EARTH.................................................... ......... 145
PALAEOZOIC................................................ ........................................................ ............. 145
CHAPTER 8. VENDIAN PERIOD.................................................... ............................................... 149
8.1 ABOUT THE POSITION OF THE VENDIAN SYSTEM IN THE GENERAL CHRONOSTRATIGRAPHIC SCALE 149
8.2. STRATOTYPES OF THE VENDIAN SYSTEM.................................................... .......... 150
8.3. ORGANIC WORLD................................................... ........................................... 155
8.4. PALEOTECTONIC AND PALEOGEOGRAPHIC CONDITIONS.. 156
8.5 CLIMATIC ZONING.................................................... ................. 162
CHAPTER 9. THE CAMBRIAN PERIOD.................................................... ................................... 166
9.1. STRATIGRAPHIC DIVISION AND STRATOTYPES.................................... 166
9.2. ORGANIC WORLD................................................... ........................................... 170
9.3. PALEOTECTONIC AND PALEOGEOGRAPHIC CONDITIONS.. 173
9.4: CLIMATIC AND BIOGEOGRAPHIC ZONING......... 180
9.5. MINERALS................................................ ................................ 185
CHAPTER 10. ORDOVICIAN PERIOD.................................................... ................................ 185
10.1. STRATIGRAPHIC DIVISION AND STRATOTYPES.................................. 186
10.2. ORGANIC WORLD................................................... ........................................ 187
103. PALEOTECTONIC AND PALEOGEOGRAPHIC CONDITIONS. 191
10.4. CLIMATIC AND BIOGEOGRAPHIC ZONING....... 201
10.5. MINERALS................................................ ........................... 204
CHAPTER 11. SILURIAN PERIOD.................................................... ................................ 205
11.1. STRATIGRAPHIC DIVISION AND STRATOTYPES.................................. 205
11.2. ORGANIC WORLD................................................... ........................................ 207
11.3. PALEOTECTONIC AND PALEOGEOGRAPHIC CONDITIONS 209
11.4. CLIMATIC AND BIOGEOGRAPHIC ZONING....... 216
11.5. MINERALS................................................ ........................... 219
CHAPTER 12. DEVONIAN PERIOD.................................................... ........................................... 219
12.1. STRATIGRAPHIC DIVISION AND STRATOTYPES.................................. 219
12.2. ORGANIC WORLD................................................... ........................................ 221
12.3. PALEOTECTONIC AND PALEOGEOGRAPHIC CONDITIONS 224
12.4. CLIMATIC AND BIOGEOGRAPHIC ZONING....... 236
12.5. MINERALS................................................ ........................... 239
CHAPTER 13. COAL PERIOD.................................................... ................. 240
13.3 STRATIGRAPHIC DIVISION AND STRATOTYPES.................................. 240
13.2. ORGANIC WORLD................................................... ........................................ 246
13.4. CLIMATIC AND BIOGEOGRAPHIC ZONING....... 263
135. MINERAL RESOURCES.................................................... ................................ 269
CHAPTER 14. PERMIC PERIOD.................................................... ........................................... 270
14.2. ORGANIC WORLD................................................... ........................................ 271
14.3. PALEOTECTONIC AND PALEOGEOGRAPHIC CONDITIONS 274
14.5. MINERALS................................................ ........................... 289
MESOZOIC ERA................................................... ........................................................ ................ 290
CHAPTER 15. TRIASSIC PERIOD.................................................... ........................................... 290
15.1. STRATIGRAPHIC DIVISION AND STRATOTYPES.................................. 290
15.2. ORGANIC WORLD................................................... ........................................ 292
15.3. PALEOTECTONIC AND PALEOGEOGRAPHIC CONDITIONS 294
15.4. CLIMATIC AND BIOGEOGRAPHIC ZONING....... 303
15.5. MINERALS................................................ ........................... 305
CHAPTER 16. JURASSIC PERIOD.................................................... ............................................... 307
16.1. STRATIGRAPHIC DIVISION AND STRATOTYPES.................................. 307
16.2. ORGANIC WORLD................................................... ........................................ 312
163. PALEOTECTONIC AND PALEOGEOGRAPHIC CONDITIONS. 315
16.4. CLIMATIC AND BIOGEOGRAPHIC ZONING....... 325
165. MINERAL RESOURCES.................................................... ................................ 331
CHAPTER 17. CRETACEUS .................................................. ............................................... 331
17.1. STRATIGRAPHIC DIVISION AND STRATOTYPES.................................. 332
17.2. ORGANIC WORLD................................................... ........................................ 335
17.3. PALEOTECTONIC AND PALEOGEOGRAPHIC CONDITIONS 341
17.4. EVOLUTION AND EXTINCTION OF FAUNA IN THE CRETACEUS......... 356
175. CLIMATIC AND BIOGEOGRAPHIC ZONING........ 358
17.6 MINERAL RESOURCES.................................................... ............................... 363
CENIOZOIC ERA................................................... ........................................................ ............. 364
18.2 ORGANIC WORLD.................................................... ........................................... 368
18.3. PALEOTECTONIC AND PALEOGEOGRAPHIC CONDITIONS 369
18.4. CLIMATIC AND BIOGEOGRAPHIC ZONING....... 383
18.5. MINERALS................................................ ............................... 388
CHAPTER 19. NEOGEN PERIOD.................................................... ................................... 389
19.1 STRATIGRAPHIC DIVISION AND STRATOTYPES.................................. 389
19.2. ORGANIC WORLD................................................... ........................................ 391
19.3. PALEOTECTONIC AND PALEOGEOGRAPHIC CONDITIONS 393
19.4. CLIMATIC AND BIOGEOGRAPHIC ZONING....... 407
19.5 MINERAL RESOURCES.................................................... ........................... 410
CHAPTER 20. QUATERARY (ANTHROPOGENIC) PERIOD.................................... 412
20.1. STRATIGRAPHIC DIVISION................................................................. .... 412
20.2. ORGANIC WORLD................................................... ........................................ 417
20.3. NATURAL CONDITIONS................................................... .................................... 420
20.4. MINERALS................................................ ........................... 427
CONCLUSION................................................. ........................................................ ........................... 428
LITERATURE................................................. ........................................................ ........................... 438
HISTORICAL GEOLOGY
Tutorial
PREFACE
Historical geology is one of the fundamental subjects of the training program for specialists in the field of "Geology". To effectively master the material, it is necessary to provide students with a sufficient amount of educational and methodological literature. Over the past decade and a half, leading teams in the country have published three well-known textbooks that are widely used in most universities. This is a textbook by the team of the Department of Historical and Dynamic Geology of the St. Petersburg State Mining Institute (now SPGU) “Historical Geology with the Fundamentals of Paleontology”, 1985. Authors - E.V. Vladimirskaya, A.Kh. Ka-garmanov, N.Ya. Spassky and others. In 1986, the textbook “Historical Geology” by G.I. Nemkov, E.S. was published. Levitsky, I.A. Grechishnikova, etc., prepared at the Department of Regional Geology and Paleontology of the Moscow Geological Prospecting Institute (now MGGA). In 1997, MSU scientists published the textbook “Historical Geology”; authors - V.E. Khain, N.V. Koronovsky and N.A. Yasamanov. All these textbooks were used in the preparation of this manual on historical geology. Let us also mention “Historical Geology with the Fundamentals of Paleontology,” published in 1998 (author - M.D. Parfenova). The manual was prepared at the Department of General and Historical Geology of Tomsk Polytechnic University. However, the shortage of textbooks for this course has not been eliminated, since the first two textbooks were published quite a long time ago, and the last two have a small circulation and have already become a bibliographic rarity. There was a need to prepare a new textbook that would be accessible to our students and take into account original Siberian material.
It is also necessary to emphasize the following circumstance. Well-known textbooks on historical geology interpret the development of the Earth differently and pay unequal attention to the issues of new global tectonics. If in the textbooks of E.V. Vladimirskaya et al. (1985), G.I. Nemkov et al. (1986) the issues of lithospheric plate tectonics are almost not considered or occupy a very modest place, then the latest textbook by V.E. Khain, N. V. Koronovsky and N.A. Yasamanov (1997) is entirely based on this concept.
In the authors' opinion, it is necessary to be critical of the mobilism hypothesis, since many factual data cannot be contained within the framework of plate tectonics alone. The concept of lithospheric plates faces particular difficulties in relation to the Paleozoic and Precambrian stages of earth history. The main contradiction is the deep roots of the continents, which do not allow them to move freely along the asthenospheric layer, as well as the presence of ring structures and the absence of large accumulations of sedimentary material in subduction zones. In our opinion, the use of the pulsation hypothesis, which is based on alternating epochs of compression and expansion of the Earth due to cosmic reasons, is justified. Apparently, epochs of expansion are associated with the appearance of rift zones and the divergence of continents. After the works of V.A. Obruchev and M.A. Usov, these ideas have been especially actively developed in recent years by E.E. Milanovsky and his supporters; these ideas are given priority in this tutorial. The concept of new historical geology, apparently, should take into account only limited spreading during the pulsating development of the Earth, the cyclicity and evolution of all geological processes, including the evolution of the organic world observed on paleontological material.
The proposed textbook has a volume comparable to the textbooks mentioned above and covers all sections of the course provided for by the program. One of the innovations in this textbook is the combination of information on the paleogeography of different periods of the Phanerozoic with the most characteristic sections, which also show the distribution of fossil remains. The well-known schemes of N.M. Strakhov, supplemented by the authors, are taken as the basis for paleogeographic reconstructions. These generalized diagrams are presented in color for the first time, which should significantly enhance the perception of the material presented. Along with these schemes, which do not take into account the concept of new global tectonics, the textbook contains platetectonic reconstructions of ancient continents, which we borrowed from the book by J. Monroe & R. Wicander, 1994. Tables of characteristic organisms of various systems are compiled following the example of those from the textbook by G. I. Nemkova et al. (1986), supplemented with Siberian material and to the maximum; are close to the collections available at the Department of Paleontology and Historical Geology of Tomsk State University.
The contents of the textbook were discussed with colleagues at the Department of Paleontology and Historical Geology of TSU. The authors are grateful to Associate Professor N.I. Savina for her help in editing the textbook, Professor of TSU A.I. Rodygin and Associate Professor G.M. Tatyanin for valuable advice when reading a number of chapters, as well as Associate Professor of Moscow State University D.I. Panov, who made important critical comments, which made it possible to improve the content and structure of the textbook. We express our gratitude to the head of the department of the Ministry of Natural Resources of Russia, Honored Geologist of Russia L.V. Oganesyan and the General Director of Geoinformmark CJSC G.M. Geisherik for their assistance in the publication of the textbook for the 300th 1st edition of the Mining and Geological Service of Russia. We thank V.A. Konovalova, T.N. Afanasyeva and E.S. Ab-durakhmanova, who participated in the computer typing, as well as all the people who contributed to the publication of this work.
INTRODUCTION
Historical geology- a synthetic discipline that integrates data from many other geological sciences. Subject The study of historical geology is the Earth, more precisely, its upper solid shell - the earth's crust. Target historical geology - identifying the processes that occurred in the earth's crust during geological time, elucidating the patterns of its development, recreating with the greatest completeness pictures of the evolution of the biosphere in past geological eras of our planet.
The main documents by which the geological history of the development of the region is reconstructed are rocks and the fossil organic remains contained in them, collected by geologists during field work. Information about geological phenomena and episodes that occurred in the geological past is based on these materials. A comprehensive study of rock samples in laboratories, restoration of the appearance of animals and plants, their way of life and interaction with the environment. Allows us to decipher certain geological events that took place and reconstruct the physical and geographical conditions that existed on the earth's surface in past geological eras.
Historical geology solves the following basic tasks:
1. Study of the occurrence of rock layers, restoration of the chronological sequence
The details of their education, determination of relative age. Rocks that make up the earth's crust
were formed not immediately, but in some sequence; and in the same period of time
In different parts of the earth's surface, various compositions and origins arose.
breeds This task is to study the composition, place and time of formation of rock layers, and
also identifying their relationships and comparing (correlation) with each other is decided by the
logical discipline stratigraphy(from Latin stratum - layer and Greek grapho - write).
At the same time, stratigraphy largely uses data from lithology, paleontology,
structural geology, relative and absolute geochronology.
2. Analysis of the formation and development of life on Earth is the prerogative paleontology. Sections pa
Leontology: paleofaunistics And paleofloristics study the totality accordingly
species and plants that lived at a certain time in different climatic conditions, as well as about
origin and development of faunas and floras over time. Chapter paleobiogeography naturally reveals
the spatial as well as temporal distribution of fossil animals and plants.
3. Restoration of the physical and geographical conditions of the earth’s surface of the geological
past, in particular, the distribution of land and sea, relief of land and the World Ocean, depths, salt
ity, temperature, density, dynamics of sea basins, climate, biological and geochemistry
chemical conditions is one of the most difficult problems in historical geology. She is the main one
task of science paleogeography, which in the last century emerged from historical geology into
an independent branch of scientific knowledge. Paleogeographical research is impossible
led without studying the material composition, structural and textural structure of sedimentary mountains
new breeds.
4. Reconstruction of the history of tectonic movements. Multi-age and multi-scale
traces of tectonic movements in the form of disturbances in the primary occurrence of rock layers and
geological bodies are observed everywhere on the earth's surface. Definition of time
manifestations, nature, magnitude and direction of certain tectonic movements deals with regional geotectonics, and studies the history of the development of various structural elements of individual areas and the entire earth’s crust historical geotectonics.
5. Reconstruction and explanation of the history of volcanism, plutonism and metamorphism. At the core
research lies in determining the relative and absolute age of volcanogenic-sedimentary -
igneous, igneous and metamorphic rocks, as well as the establishment of the primary nature after
days. After this, areas of volcanic activity are identified, the area is identified and reconstructed
The effects of volcanism and plutonism determine the geochemical features of mantle flows.
These are the tasks geochemistry And petrology.
6. Identifying patterns of distribution of minerals in the earth’s crust - this task
helps solve the geology section the doctrine of minerals.
7. Establishment of the structure and patterns of development of the earth's crust. This is one of the most important
problems of historical geology, which cannot be solved without using knowledge from many
disciplines and areas of geosciences. This problem can be solved primarily by regional
naya geology, regional And historical geotectonics, geochemistry, space geology, geophysics
zika, petrology and other sciences.
Historical geology, based on generalization, analysis of various facts, and documentary material, recreates fragments of the evolution of the earth's crust and pictures of the geological past. This, in fact, is its main task.
Historical geology uses mainly data on the geological structure of land, which occupies only one third of the earth's surface. The rapid development of marine geology over the past two decades has given us new information on the geology of the bottom of seas and oceans; these materials help to reconstruct only the relatively recent history of the development of the oceanic crust. The patterns revealed in this case can hardly be interpolated to more distant geological zones and eras (Precambrian, Paleozoic). Restoring the geological history of the Earth in its entirety using the entire set of both previous and new methods and patterns is the task of researchers of the coming 21st century.
Knowledge of historical geology is necessary when studying regional geology, which considers the geological structure of individual regions of the Earth as a result of their geological history. At the same time, generalization and analysis of regional geological data make it possible to reconstruct the history of the Earth as a whole and identify patterns of its development in past geological eras.
Historical geology as a science arose at the turn of the 18th and 19th centuries. However, humanity has long been interested in the origin of rocks and the fossils they contain, and the ways in which the earth’s surface was transformed. There are many interesting geological observations and ideas in the works of scientists of Ancient Egypt, Greece, Rome, India and China on these problems, but they were not given much importance until the Renaissance.
In 1669, the Danish naturalist Niels Stensen (1638-1686), who worked in Italy and was known in scientific circles as Nicholas Stenon, formulated six basic rules (postulates) of stratigraphy.
1. The layers of the Earth are the result of sedimentation in water.
2. The layer containing the fragments of another layer was formed after it.
3. Every layer was deposited later than the layer on which it lies, and earlier than the one that precedes it
covers.
5. The layer must have an indefinite extent and can be traced across
any valley.
6. The layer was first deposited horizontally; if it is tilted, then it has experienced some kind of bending. If another layer rests on inclined layers, then their bending occurred before the deposition of this second layer.
In these basic provisions of Stenon we see, first of all, the beginning of such sciences as stratigraphy and tectonics,
In the middle of the 18th century. The works of J. Buffon and I. Kant appeared, in which, on the basis of cosmogonic ideas, ideas were expressed about the variability and development of the Earth's history.
The most correct explanation of geological phenomena was given in the works of the brilliant Russian scientist M.V. Lomonosov (1711-1765). He divided geological processes into internal and external and assigned the leading role to internal causes in the formation of mountains and depressions. M.V. Lomonosov was actually the first to apply the principle of actualism. He clearly pointed out that the study of modern geological processes allows us to understand the past of the Earth. Referring to the conditions for the formation of sedimentary rocks, in his work “On the Layers of the Earth” (1763) he wrote: “... these different kinds of matter lying one on top of the other (which are called flats) show that they did not occur at the same time; however, together have undergone... general and specific changes. The sandy layers were formerly the bottom of the sea or a great river."
Historical geology arose in the second half of the 18th century. and formed a single whole with stratigraphy. However, stratigraphic studies were rare and fragmented. A great contribution to the development of this science was made by the Italian scientist D. Arduino, who in 1760 created the first scheme for dividing rocks by age. Thanks to the research of German geologists, especially A. Werner (1750-1817), a regional stratigraphic scheme of Central Germany was developed and, on its basis, the geological history of the development of Europe was reconstructed.
By the end of the 18th century. A lot of geological information has accumulated, but a reliable method has not yet been found for determining the synchronicity and coeval age of sediments and, consequently, the processes that caused them. Therefore, a historical systematization of the collected information was impossible. This key was the paleontological (biostratigraphic) method, the founder of which was the English engineer W. Smith (1769-1839). True, his predecessor, the French abbot Giraud Soulavi, back in 1779 established a consistent succession of complexes of fossil organisms in the section of sedimentary strata of Southern France and came to the conclusion that the chronological order of the eras of dominance of various complexes of marine animals corresponds to the sequence of occurrence and relative age of the mountain layers hosting this fauna breeds However, the practical importance of fossil organisms for the division and correlation of sedimentary strata was shown by W. Smith, who compiled the first scale of the vertical sequence of sedimentary rocks in England based on the biostratigraphic method.
The founders of the paleontological method, along with W. Smith, are the French scientists J. Cuvier (1769-1832) and A. Brongniard (1801-1876). Carrying out geological research at the same time, but independently of each other, they came to the same conclusions related to the sequence of occurrence of the layers and the remains of fossil fauna contained in them, which made it possible to compile the first stratigraphic columns, sections and geological maps of a number of regions of England and France. Based on the paleontological method, in the 19th century most of the currently known geological systems were identified and geological maps were compiled. The discovery of a new method contributed to the rapid development of historical geology and marked the beginning of the “stratigraphic” stage in the development of this science. For 20 years of the 19th century. (:1822-1841), called by B.S. Sokolov the “heroic era” in the development of geology, almost all the main divisions of the general stratigraphic scale were established, which made it possible to systematize extensive geological material in chronological sequence. However, these achievements were marked by the dominance of the ideas of catastrophism, divine acts of Creation, which explained the change in the complexes of animals and plants in a vertical section.
The major French scientist J. Cuvier was not only one of the founders of the paleontological method, but also the author of the theory of catastrophes, which at one time enjoyed wide popularity. Based on geological observations, he showed that some groups of organisms died out over geological time, but new ones took their place. His followers J. Agassiz (1807-1873), A. d'Orbigny (1802-1857), L. Elie de Beaumont (1798-1874) and others began to explain not only the extinction of organisms, but also many other events on the earth's surface by catastrophes In their opinion, any changes in the occurrence of rocks, relief, changes in landscapes or habitat conditions, as well as the extinction of organisms were the results of various-scale catastrophic phenomena that occurred on the earth's surface.Later, the theory of catastrophes was sharply criticized by the outstanding scientists of the 19th century, J. Lamarck ( 1744-1829), Charles Lyell (1797-1875), Charles Darwin (1809-1882). The French naturalist J. Lamarck created the doctrine of the evolution of the organic world and for the first time proclaimed it a universal law of living nature. The English geologist Charles Lyell in his work "Fundamentals of Geology" argued that major changes on Earth occurred not as a result of destructive catastrophes, but as a result of slow, long-term geological processes. Knowledge of the history of the Earth Charles Lyell proposed starting with the study of modern geological processes, believing that they are "the key to knowledge geological processes of the past." This position of Charles Lyell was later called the “principle of actualism.”
A crushing blow to catastrophism was dealt by the appearance of Charles Darwin's On the Origin of Species by Means of Natural Selection (1859). His conclusions about the importance of natural selection in the evolution of the organic world strengthened the role of fossil organic remains as documents of the history of life and as the basis for the chronological division of rock layers. Charles Darwin's ideas about the incompleteness of the geological and paleontological record were also of great importance in the development of historical geology. The appearance of the works of Charles Darwin provided great support to the teachings of evolutionists, since they proved that the organic world is transformed through slow evolutionary changes.
According to V.M. Podobina and G.M. Tatyanin (Evolution.., 1997), in the history of the Earth, under the influence of predominantly cosmic and tectonic factors, a gradual complication of the biota is observed with periodic disruption of its balance and uniform development. Since the time of J. Cuvier, researchers have repeatedly noted how some organisms at certain intervals gave way in ecosystems to other, more progressive forms. However, the development of such ideas on a scientific basis became possible only in the 20th century, with the accumulation of information about the organic world of past geological eras. The geochronological factor (geological time) in this case becomes one of the leading ones. The discontinuous nature of the continuous development of biota is an integral part of the global process of evolution of organisms and is determined, as studies by many scientists have shown, by the revolution of the Earth together with the Solar system around the center of the Galaxy, the passage of various sectors of the galactic orbit and other “cosmic” reasons, their interaction with the internal energy of the Earth .
In complexly organized forms with sexual differentiation, cyclical development is observed (formation, development and extinction), and such organisms are more susceptible to extinction during natural disasters. Progressive (mainstream) evolution, in the opinion of V.M. Podobina and G.M. Tatyanin (1997), is apparently due, in addition to natural selection according to Charles Darwin, to the influence of so-called “catalysts” (active zones, rifts, etc. .d.), which contributed to the accelerated mutation process and rapid development of organisms that entered these zones during migration.
Studying Phanerozoic foraminifera, as well as taking into account the development of other organisms according to published works, V.M. Podobina and G.M. Tatyanin suggest that the following main factors influenced the evolution of biota:
1. Cosmic (circulation of the Earth together with the Solar system around the center of the Galaxy,
change in solar radiation, fall of asteroids, meteorites, change in eccentricity
the Earth's orbital system, the Earth's rotation axis, etc.).
2. Tectonic (orogenesis, rifting, formation of deep-sea trenches, subsidence,
uplifts, etc.).
3. Geochronological (geological time).
The following two factors are interrelated with the first two factors:
4. Paleogeographical (ecosystem rearrangements: abiotic and biotic changes
nia, the relationship of organisms).
5. Temperature (climatic and vertical zoning: temperature decrease towards
poles and with depth, an increase in certain places in temperature associated with endogenous
processes).
6. Migration factor (of great importance in the Mesozoic and, especially, the Cenozoic).
During geological time, the influence of these factors on the evolution of organisms was unequal. As indicated, the action of the first and, as a consequence, the second factors prevailed in the first and subsequent stages of biota development, then the influence of geochronological and other factors began. The sixth factor became especially noticeable with the appearance of actively or passively moving nektonic, planktonic and some benthic organisms as a result of the emergence of more diverse climatic and other environments, which led to the accelerated evolution of certain groups of these organisms.
The rate of evolution of representatives of the biota therefore did not remain constant. Based on the study of some orders of foraminifera, three main groups have been identified according to the rate of evolution, which can be traced among other organic forms:
1) accelerated evolution (plankton, nekton and partially mobile benthos); 2) moderate evolution (mobile benthos); 3) slow evolution (slowly moving and sessile benthos). Within each group, in turn, based on the rate of evolution, subordinate subgroups can be distinguished, differing in certain features.
One of the catastrophic extinctions of organisms at the Cretaceous-Paleogene boundary affected, as is known, the most specialized forms, which were largely in the third stage of development (extinction). These are mainly globotruncans (foraminifera), ammonites, belemnites, dinosaurs, etc. According to the speed of evolution, they belong to the first group. Most organisms of the second and mainly third groups passed this milestone without noticeable changes.
Simultaneously with the development of historical geology at the end of the 18th century. There was an idea about the existence of a more diverse geological science, which began to be called “geognosy”. In terms of content, geognosy corresponded to geoscience, since it examined the state of all known shells of the Earth. As G.P. Leonov noted (1980), by the beginning of the 19th century. Two significantly different directions in the study of the Earth were determined: geological and geognostic. The geological direction focused its attention on the study of the upper sedimentary layer of the earth's crust, and its structure and development was considered mainly from a historical point of view; geognostic - with its research it covered the entire planet and included in the objects of study not only the earth's crust, but also all other shells of the Earth. This, in turn, forced geologists not only to consider the Earth from a historical perspective, but also to focus their attention on determining the composition of geospheres, the emergence and development of geological processes. Therefore, over time, the historical direction of research gradually began to recede into the background.
By the middle of the 19th century. These include the first attempts to reconstruct the physical and geographical conditions of individual geological epochs both for large areas of land (G.A. Trautschold, J. Dana, V.O. Kovalevsky) and for the entire globe (J. Marcoux). These works marked the "pa-
leogeographical" stage in the development of historical geology. Of great importance for the formation of paleogeography was the introduction in 1838 by A. Gressley (1814-1865) of the concept of facies, the essence of which is that rocks of the same age can have different compositions, structures. » shape and texture, reflecting the conditions of their formation.
In 1859, the idea of geosynclines arose in North America (J. Hall), and at the end of the 19th century, the outstanding Russian geologist A.P. Karpinsky, in his works revealing the patterns of geological development of the European part of Russia, laid the foundations for the doctrine of platforms The idea of geosynclines and platforms as the most important elements of the structure of the earth's crust took shape in the form of a coherent theory in the work of the French scientist E. Hauge "Geosynclines and continental areas" (1900) and became the most important generalization of the geological history of the earth's crust.
Russian geological science owes the wide dissemination and development of these ideas to A.A. Borisyak, who, following E. Og, began to consider historical geology as the history of the development of geosynclines and platforms. The ideas of A.A. Borisyak underlie many areas of modern historical geology. In the 20s, A.A. Borisyak’s student D.V. Nalivkin laid the foundations for the doctrine of facies; somewhat later, in the works of R.F. Hecker, B.P. Markovsky and other researchers, a “paleoecological” direction in the study of the relationships between organisms and the environment in the past began to take shape.
Soon after the work of E. Og, the German geophysicist A. Wegener formulated in its most complete form the hypothesis of continental drift (the hypothesis of mobilism). After a period of oblivion, starting in the 60s of the 20th century, this idea was revived on a new factual basis as the hypothesis of neomobilism (new global tectonics, or lithospheric plate tectonics). A. Holmes, G. Hess, R. Dietz, F. Wayne, D. Matthews, D. Wilson, Z. Le Pi+shon and many other researchers made a great contribution to the development of this concept.
The 20-40s were a time of widespread development of regional geological research, on the basis of which large general reports were created on the territory of Europe (S.N. Bubnov), Siberia (V.A. Obruchev), the USSR (A.D. Arkhangelsky). The implementation of these works was facilitated by the ideas about folding phases put forward by the outstanding German tectonist G. Stille. Based on a generalization of the enormous factual material on stratigraphy, paleogeography, magmatism and tectonics, the main patterns of the geological development of the Earth are formulated in the works of foreign (L. Kober, G. Stille) and domestic (A.D. Arkhangelsky, D.V. Nalivkishch N.M. Strakhov, N.S. Shatsky and others) scientists.
If the end of the XIX - 60s of the XX century. can be identified as a “tectonic” stage in the development of historical geology, then the modern stage is characterized by the synthesis of refined data on the geology of the continents, the analysis of the ever-increasing flow of information on the geology of the ocean floor, work to create a complete picture of the geological history of the Earth, to identify the patterns of this history and explaining their causal relationship. At the same time, science relies not only on old, constantly improving research methods, but also on new methods: absolute geochronology, geochemical, geophysical, paleomagnetic, deep and ultra-deep drilling.
Along with scientific research, already at the beginning of the 20th century. Leading professors began to teach courses in historical geology in higher educational institutions - initially in St. Petersburg, then in other cities of Russia.
At the first stage of teaching, translated textbooks were used, for example, M. Neymayr’s two-volume “History of the Earth” (1897-1898) edited by A.A. Inostrantsev. Later, textbooks written by Russian scientists appeared. At the Imperial St. Petersburg University, Professor A.A. Inostrantsev (1903, volume II) first gave a course of lectures on historical geology. Along with the description of geological sections of other countries of the world, A.A. Foreigners
The geological characteristics of individual regions of Russia are given. He gives especially detailed information on the Quaternary system, the study of which until that time had received insufficient attention.
In 1910-1911 At the St. Petersburg Mining Institute, F.N. Chernyshev gave a course of lectures on historical geology, which took into account his many years of research on individual regions of Russia.
As already indicated, A.A. Borisyak’s ideas underlie paleogeographical reconstructions and the associated consistent change in physiographic settings. Subsequently, the doctrine of facies, developed by D.V. Nalivkin, also contributed to the development of historical geological research and enrichment of the university course in historical geology. D.V. Nalivkin, in addition, introduced information about magmatism and minerals into the course of historical geology in 1932. In the 40s, B.S. Sokolov gave this course of lectures at Leningrad State University, supplementing the characteristics of the periods with the paleogeographical features of the continents. At the same time, textbooks on historical geology by G.F. Mirchinok, A.N. Mazarovich, M.K. Korovin and others were published. The two-volume edition “Fundamentals of Historical Geology” by N.M. Strakhov (1948) was the main textbook for about thirty years at this rate, and its paleogeographical schemes have not lost their significance to the present day.
“Fundamentals of the History of the Earth, or an Introduction to Historical Geology” by the American researcher W. Stokes (W. Stokes, 1960) gives an idea of the unified history of the earth’s crust and its organic world based on the integration of local events in both space and time.
One of the fundamental ones is the textbook by G.P. Leonov (1980), in which historical geology is considered as a branch of science that illuminates the patterns of development of the earth’s crust and the Earth as a whole.
A major event in research in historical geology was the International Scientific and Methodological Conference, organized by the Department of Historical and Dynamic Geology (head of the department, Professor A.Kh. Kagarmanov) at the St. Petersburg Mining Institute (Technical University) (April 20-21, 1999) and dedicated to the 110th anniversary of the birth of the outstanding scientist academician D.V. Nalivkin. This conference contributed to the development of the concept of this textbook, provided an opportunity to rethink the accumulated new theoretical material and significantly improve its demonstration part.
In recent years, the main courses in historical geology have been textbooks edited by Professor A.Kh. Kagarmanov (1985), Professor G.I. Nemkov (1986) and Academician V.E. Khain (1997).
Prospects for the development of historical geology are associated with the creation of a coherent theory of the development of the earth's crust, summarizing all the latest information recently obtained by geophysics, geochemistry, petrology, paleontology and other sciences. It is necessary to correctly reflect the relationship between vertical and horizontal movements of the earth's crust. The basis for these generalizations may no longer be mobilism, which is unable to explain the accumulated facts that contradict it, but, for example, a pulsation concept based on the ideas of cyclicity and directionality of geological processes, currently being developed by Academician E.E. Milanovsky and others researchers.
One of the most important tasks of historical geology - identifying the patterns of distribution of minerals - is complicated by the polygenicity and polychronic nature of mineralization. Of great interest are the recent data of plume tectonics (superplumes, etc.) and the opened prospects for constructing the concept of ore formation, oil and gas formation on a new basis.
The search for new traces of life in the Precambrian and Late Proterozoic can provide interesting results and complement our understanding of the earliest stages of the development of the biosphere and the earth’s crust.
BASIC CONCEPTS AND METHODS OF HISTORICAL GEOLOGY
To successfully solve the assigned problems, historical geology must have a set of methods. Based on the complex, synthetic nature of historical geology, it uses at its service the methods of all the geological sciences listed in the introduction, as well as the methods of biology, physics, chemistry, astronomy, mathematics, computer science, etc.
Let's consider the methods of historical geology.
Chapter 1. Historical geology - as a science
Precambrian Paleozoic fossil geosynclinal
Historical geology includes a number of sections. Stratigraphy is the study of the composition, location and time of formation of rock layers and their correlation. Paleogeography examines climate, topography, the development of ancient seas, rivers, lakes, etc. in past geological epochs. Geotectonics deals with determining the time, nature, and magnitude of tectonic movements. Petrology reconstructs the time and conditions for the formation of igneous rocks. Thus, historical geology is closely related to almost all areas of geological knowledge.
One of the most important problems of geology is the problem of determining the geological time of formation of sedimentary rocks. The formation of geological rocks in the Phanerozoic was accompanied by increasing biological activity, so paleobiology is of great importance in geological research. For geologists, an important point is that evolutionary changes in organisms and the emergence of new species occur within a certain period of geological time. The principle of final succession postulates that the same organisms are common in the ocean at the same time. It follows from this that a geologist, having determined a set of fossil remains in a rock, can find rocks that formed at the same time.
The boundaries of evolutionary transformations are the boundaries of the geological time of formation of sedimentary horizons. The faster or shorter this interval, the greater the opportunity for more detailed stratigraphic divisions of strata. Thus, the problem of determining the age of sedimentary strata is solved. Another important task is to determine living conditions. Therefore, it is so important to determine the changes that the habitat imposed on organisms, knowing which we can determine the conditions for the formation of precipitation.
The "geological column" and its interpretation by creationists and uniformitarians
Geology, or earth science, is the scientific discipline that has been most successfully used by skeptics to discredit the Bible. The study of the structure of the Earth, especially the rocks that form the upper part of the Earth's crust...
Until the 19th century, the topic of “man and nature” was studied almost exclusively within the framework of philosophy. The relevant facts were not systematized. No classification of forms of human impact on nature has been carried out...
Geological human activity and its consequences
“Thought is not a form of energy,” wrote V.I. Vernadsky. “How can it change material processes?” Indeed, technogenesis acts as a geological force that sets in motion gigantic masses of matter...
Geoecological problems of the state and functioning of the ecosystem of the Krasnodar reservoir
In October 1973, the first notes about the grandiose construction of the largest reservoir in the Kuban, the Krasnodar reservoir, appeared in Krasnodar newspapers. It was built by order of the Council of Ministers of the USSR...
Earth science as science
Soil science is the science of soil, its creation (genesis), nature, storage, power, patterns of geographical expansion, relationships with the surrounding environment, the role of nature, roads and methods of its reclamation...
Petrography of igneous and metamorphic rocks
Petrography is a science of the geological cycle, the purpose of which is a comprehensive study of rocks, including their origin. It should be noted that, at its core, petrography should deal with all types of rocks...
Soils of the Gatchina district of the Leningrad region
For the most part, the Gatchina region lies on the Ordovician limestone plateau. This is a relatively elevated plain with a slight slope in the southern and southeastern directions, composed of Ordovician limestones...
Combined ore development project
Development of the Lebedinskoye mining deposit
The Lebedinskoye field is confined to the central part of the northeastern strip of the Kursk magnetic anomaly, passing in the southern part of the Central Russian Upland along the watershed of the Dnieper (in the west) and Don (in the east) rivers...
Historical geology is a complex science that studies the development of the planet and the earth's crust and the sequence of geological events.
Research in the disciplines of the geological cycle is carried out in a historical context. Each of the sciences examines the development and sequence of the objects and phenomena being studied. In addition, in geology there are a number of disciplines involved in the study of general geological history. These include historical geology.
Story
Knowledge about the geological history of the Earth has been accumulated since ancient times within a single geological direction. However, the prerequisites for the formation of historical geology arose only in the 19th century, when J. Cuvier, W. Smith, and A. Brongniart obtained conclusions about the sequence of changes in horizons with organic remains. This served as the basis for paleontological method, one of the main ones in this discipline.
Its emergence as an independent science occurred in the 19th century. and included two stages, distinguished on the basis of the theoretical principles used. Thus, in the first half of the century, the development of this discipline was influenced by the theory of catastrophes developed by A. d'Orbigny and J. Cuvier, and in the second half it was replaced by the ideas of evolutionary development of Charles Darwin, J. Lamarck and Charles Lyell.
In addition, in accordance with the order of formation of related disciplines that prevailed in the development of historical geology, this process until the middle of the 20th century. are divided into three stages: stratigraphic, paleogeographic, tectonic. At the beginning of the century, stratigraphy was formed: they created the structure of the stratigraphic scale, developed a scale for Europe, and chronologically systematized the geological material. In the middle of the century, the formation of paleogeography began thanks to the reconstruction of physiographic conditions by J. Dan and V.O. Kovalevsky and the introduction of A. Gressley the concept of “facies”. A little later, the doctrine of geosynclines began to emerge, and by the end of the century - the doctrine of platforms, which form the basis of tectonics. Then the modern stage began.
Historical geology itself took shape in the second half of the 19th century. At the same time, the main directions of research were formulated.
Historical geology has made significant contributions to the development of geological knowledge. Thus, within the framework of this science, the laws of development of geological processes (the formation of continents, the emergence and transformation of platforms and geosynclines, changes in the nature of magmatism, etc.) were clarified, and the general direction of the evolution of the planet and the earth’s crust was predicted.
Modern science
Now historical geology includes two directions:
- Study of geological history in the context of tectonics, paleogeography, stratigraphy
- Creation of a general historical and geological picture with the establishment of patterns and their relationships.
Thus, this science includes geochronology, paleotectonics, paleogeography, stratigraphy.
Currently, the field of study of historical geology includes several subjects. These include the age of rocks (the chronological sequence of their formation and position in the section, as well as organic remains, the history of the development of organisms), physical and geographical conditions (position of land and ocean, climate, relief in different periods of geological history), tectonic setting and magmatism ( development of the earth's crust, formation and development of dislocations: uplifts, folds, troughs, faults, etc.), the relationship of geological processes, the natural association of deposits with magmatic bodies, geological complexes and structures.
Thus, the main goal of historical geology is to reconstruct the sequence of geological processes in the interior and on the surface of the planet.
Together with other geological disciplines, historical geology forms the basis of general geology, studying the laws of the development of the Earth. In addition, this science has applied significance, which consists in the use of its data to create a scientific basis for the search and exploration of minerals by clarifying the conditions of their genesis and the laws of the location of deposits.
This discipline is associated with all geological sciences, since the consideration of subjects of study in this area takes place in a historical context. In addition, historical geology uses data, conclusions and methods from many of them: stratigraphy, lithology, paleontology, petrology, tectonics, geochemistry, regional geology, paleogeography, geophysics. Historical geology is closest to other historical and geological disciplines, such as stratigraphy and paleontology. Moreover, the first of them is sometimes considered a branch of historical geology. Stratigraphy, including biostratigraphy, forms the basis of the science under consideration, establishing the sequence of formation of rocks, and developing a geochronological system that provides interaction with geochronology. Through biostratigraphy, a connection is formed between historical geology and paleontology. Recreation of physical and geographical conditions based on the data obtained relates to paleogeography. The study of the development of the earth's crust and the sequence of processes occurring in it falls within the scope of tectonics. The study of the history of the processes of magmatism, metamorphism, and volcanism connects historical geology with petrography.
Subject, tasks, methods
The subject of historical geology is rocks and organic remains, on the basis of which the sequence of geological processes is determined.
The objectives of this science include the reconstruction and systematization of the stages of development of the earth's crust and biosphere, clarification of the laws and driving forces of these processes. This involves calculating the age of rocks, recreating tectonic structures and movements, volcanism, metamorphism, plutonism, and physical and geographical conditions of the past.
Stratigraphy is used to determine the duration and sequence of geological processes. Facies settings are reconstructed mainly through the study of rocks and organic remains within the framework of petrology and paleontology. Tectonics deals with elucidating the sequence of tectonic movements, using unconformities, breaks in sedimentation, disjunctives, and plicative deformations. To establish the laws of the structure and evolution of the earth's crust, data from geotectonics, geophysics, and regional geology are used.
Historical geology, as mentioned above, applies the methods of other geological disciplines:
- Biostratigraphy(evolutionary, guiding fossils, paleoecological, quantitative correlation methods),
- Geological(lithological, mineralogical-petrographic, structural, ecostratigraphic, rhythmostratigraphic, climatostratigraphic),
- Geophysical(magnetostratigraphic, seismostratigraphic),
- Absolute geochronology(uranium-thorium-lead, lead, rubidium-strontium, potassium-argon, samarium-neodymium, radiocarbon, fission tracks),
- Historical-geological(facies, formation analyses).
In addition to the above-mentioned applied methods, this science uses general theoretical ones, such as dialectical and actualistic.
Education and work
Historical geology is studied within the framework of geological specialties, since it forms the basis of this field of knowledge. It is rarely found as a separate specialty.
The labor sphere is determined by the focus of the specialty and the choice of the graduate, since many geological specialties allow you to work in several professions. Mostly, such specialists work in production and the scientific and educational sphere. As for people specialized specifically in historical geology, they work mainly in science and education.
Conclusion
Historical geology is one of the main disciplines of the geological cycle. It is interconnected with other sciences through the use of their data and methods and the formation of a historical and geological basis for their research. In addition, it is used for searching for deposits. Despite the absence of such a profession, knowledge in this area is used in all branches of geology.
The most ancient rocks exposed on the surface of continents were formed in the Archean era. Recognition of these rocks is difficult, since their outcrops are dispersed and in most cases are covered by thick strata of younger rocks. Where these rocks are exposed, they are so metamorphosed that their original character often cannot be restored. During numerous long stages of denudation, thick strata of these rocks were destroyed, and those that survived contain very few fossil organisms and therefore their correlation is difficult or even impossible. It is interesting to note that the oldest known Archean rocks are probably highly metamorphosed sedimentary rocks, and the older rocks overlain by them were melted and destroyed by numerous igneous intrusions. Therefore, traces of the primary earth's crust have not yet been discovered.
There are two large areas of outcrops of Archean rocks in North America. The first of these, the Canadian Shield, is located in central Canada on both sides of Hudson Bay. Although in some places the Archean rocks are overlain by younger ones, in most of the territory of the Canadian Shield they make up the surface. The oldest rocks known in this area are marbles, slates and crystalline schists, interbedded with lavas. Initially, limestone and shales were deposited here, subsequently sealed by lavas. Then these rocks were exposed to powerful tectonic movements, which were accompanied by large granite intrusions. Ultimately, the sedimentary rocks underwent severe metamorphism. After a long period of denudation, these highly metamorphosed rocks were brought to the surface in places, but the general background is granites.
Outcrops of Archean rocks are also found in the Rocky Mountains, where they form the crests of many ridges and individual peaks, such as Pikes Peak. Younger rocks there have been destroyed by denudation.
In Europe, Archean rocks are exposed in the Baltic Shield within Norway, Sweden, Finland and Russia. They are represented by granites and highly metamorphosed sedimentary rocks. Similar outcrops of Archean rocks are found in the south and southeast of Siberia, China, western Australia, Africa and northeast South America. The oldest traces of the vital activity of bacteria and colonies of unicellular blue-green algae Collenia were discovered in Archean rocks of southern Africa (Zimbabwe) and the province of Ontario (Canada).
Proterozoic era.
At the beginning of the Proterozoic, after a long period of denudation, the land was largely destroyed, certain parts of the continents were submerged and were flooded by shallow seas, and some low-lying basins began to be filled with continental sediments. In North America, the most significant exposures of Proterozoic rocks are found in four areas. The first of them is confined to the southern part of the Canadian Shield, where thick layers of shales and sandstones of the considered age are exposed around Lake. Upper and northeast of the lake. Huron. These rocks are of both marine and continental origin. Their distribution indicates that the position of shallow seas changed significantly throughout the Proterozoic. In many places, marine and continental sediments are interbedded with thick lava strata. At the end of sedimentation, tectonic movements of the earth's crust occurred, Proterozoic rocks underwent folding and large mountain systems were formed. In the foothills east of the Appalachians there are numerous outcrops of Proterozoic rocks. They were originally deposited as layers of limestone and shale, and then during orogenesis (mountain building) they metamorphosed into marble, slate and crystalline schist. In the Grand Canyon region, a thick sequence of Proterozoic sandstones, shales and limestones unconformably overlie Archean rocks. In the northern Rocky Mountains, a sequence of Proterozoic limestones with a thickness of ca. 4600 m. Although the Proterozoic formations in these areas were affected by tectonic movements and were folded and broken by faults, these movements were not intense enough and could not lead to metamorphism of the rocks. Therefore, the original sedimentary textures were preserved there.
In Europe, there are significant outcrops of Proterozoic rocks within the Baltic Shield. They are represented by highly metamorphosed marbles and slates. In northwestern Scotland, a thick sequence of Proterozoic sandstones overlies Archean granites and crystalline schists. Extensive outcrops of Proterozoic rocks occur in western China, central Australia, southern Africa and central South America. In Australia, these rocks are represented by a thick sequence of unmetamorphosed sandstones and shales, and in eastern Brazil and southern Venezuela - highly metamorphosed slate and crystalline shales.
Fossil blue-green algae Collenia are very widespread on all continents in unmetamorphosed limestones of Proterozoic age, where a few fragments of shells of primitive mollusks were also found. However, the remains of animals are very rare, and this indicates that most organisms had a primitive structure and did not yet have hard shells, which are preserved in the fossil state. Although traces of ice ages are recorded for the early stages of Earth's history, extensive glaciation, which had an almost global distribution, is noted only at the very end of the Proterozoic.
Palaeozoic.
After the land experienced a long period of denudation at the end of the Proterozoic, some of its territories experienced subsidence and were flooded by shallow seas. As a result of denudation of elevated areas, sedimentary material was carried by water flows into geosynclines, where strata of Paleozoic sedimentary rocks more than 12 km thick accumulated. In North America, at the beginning of the Paleozoic era, two large geosynclines formed. One of them, called the Appalachian, stretches from the North Atlantic Ocean through southeastern Canada and further south to the Gulf of Mexico along the axis of the modern Appalachians. Another geosyncline connected the Arctic Ocean to the Pacific Ocean, passing slightly east of Alaska to the south through eastern British Columbia and western Alberta, then through eastern Nevada, western Utah and southern California. Thus North America was divided into three parts. In certain periods of the Paleozoic, its central regions were partially flooded and both geosynclines were connected by shallow seas. In other periods, as a result of isostatic uplifts of land or fluctuations in the level of the World Ocean, marine regressions occurred, and then terrigenous material washed away from adjacent elevated areas was deposited in geosynclines.
In the Paleozoic, similar conditions existed on other continents. In Europe, huge seas periodically flooded the British Isles, the territories of Norway, Germany, France, Belgium and Spain, as well as a vast area of the East European Plain from the Baltic Sea to the Ural Mountains. Large outcrops of Paleozoic rocks are also found in Siberia, China and northern India. They are indigenous to most areas of eastern Australia, northern Africa, and northern and central South America.
The Paleozoic era is divided into six periods of unequal duration, alternating with short-term stages of isostatic uplifts or marine regressions, during which sedimentation did not occur within the continents.
Cambrian period
- the earliest period of the Paleozoic era, named after the Latin name for Wales (Cumbria), where rocks of this age were first studied. In North America, in the Cambrian, both geosynclines were flooded, and in the second half of the Cambrian, the central part of the continent occupied such a low position that both troughs were connected by a shallow sea and layers of sandstones, shales and limestones accumulated there. A major marine transgression was taking place in Europe and Asia. These parts of the world were largely flooded. The exceptions were three large isolated landmasses (the Baltic Shield, the Arabian Peninsula and southern India) and a number of small isolated landmasses in southern Europe and southern Asia. Smaller marine transgressions occurred in Australia and central South America. The Cambrian was characterized by rather calm tectonic conditions.
The deposits of this period preserved the first numerous fossils indicating the development of life on Earth. Although no terrestrial plants or animals were recorded, the shallow epicontinental seas and submerged geosynclines were rich in numerous invertebrate animals and aquatic plants. The most unusual and interesting animals of that time were trilobites (Fig. 11), a class of extinct primitive arthropods, which were widespread in the Cambrian seas. Their calcareous-chitinous shells have been found in rocks of this age on all continents. In addition, there were many types of brachiopods, molluscs, and other invertebrates. Thus, all major forms of invertebrate organisms (with the exception of corals, bryozoans and pelecypods) were present in the Cambrian seas.
At the end of the Cambrian period, most of the land was uplifted and there was a short-term marine regression.
Ordovician period
- the second period of the Paleozoic era (named after the Celtic Ordovician tribe that inhabited the territory of Wales). During this period, the continents again experienced subsidence, as a result of which geosynclines and low-lying basins turned into shallow seas. At the end of the Ordovician ca. 70% of North America was flooded by the sea, in which thick layers of limestone and shales were deposited. The sea also covered large areas of Europe and Asia, partly Australia and the central regions of South America.
All Cambrian invertebrates continued to evolve into the Ordovician. In addition, corals, pelecypods (bivalves), bryozoans and the first vertebrates appeared. In Colorado, in Ordovician sandstones, fragments of the most primitive vertebrates were discovered - jawless (ostracoderms), which lacked real jaws and paired limbs, and the front part of the body was covered with bony plates that formed a protective shell.
Based on paleomagnetic studies of rocks, it has been established that throughout most of the Paleozoic, North America was located in the equatorial zone. Fossil organisms and widespread limestones from this time indicate the dominance of warm, shallow seas in the Ordovician. Australia was located near the South Pole, and northwestern Africa was located in the region of the pole itself, which is confirmed by signs of widespread glaciation imprinted in the Ordovician rocks of Africa.
At the end of the Ordovician period, as a result of tectonic movements, continental uplift and marine regression occurred. In some places, the native Cambrian and Ordovician rocks experienced a process of folding, which was accompanied by the growth of mountains. This ancient stage of orogenesis is called the Caledonian folding.
Silurian.
For the first time, rocks of this period were also studied in Wales (the name of the period comes from the Celtic tribe of Silures who inhabited this region).
After the tectonic uplifts that marked the end of the Ordovician period, a denudation stage began, and then at the beginning of the Silurian the continents again experienced subsidence, and the seas flooded the low-lying areas. In North America, in the Early Silurian the area of seas decreased significantly, but in the Middle Silurian they occupied almost 60% of its territory. A thick sequence of marine limestones of the Niagara formation was formed, which received its name from the Niagara Falls, the threshold of which it forms. In the Late Silurian, the areas of the seas were greatly reduced. Thick salt-bearing strata accumulated in a strip stretching from modern Michigan to central New York.
In Europe and Asia, the Silurian seas were widespread and occupied almost the same territories as the Cambrian seas. The same isolated massifs as in the Cambrian, as well as significant areas of northern China and Eastern Siberia, remained unflooded. In Europe, thick limestone strata accumulated along the periphery of the southern tip of the Baltic Shield (currently they are partially submerged by the Baltic Sea). Small seas were common in eastern Australia, northern Africa and central South America.
In the Silurian rocks, in general, the same basic representatives of the organic world were found as in the Ordovician. Land plants had not yet appeared in the Silurian. Among invertebrates, corals have become much more abundant, as a result of whose vital activity massive coral reefs have formed in many areas. Trilobites, so characteristic of Cambrian and Ordovician rocks, are losing their dominant significance: they are becoming smaller both in quantity and in species. At the end of the Silurian, many large aquatic arthropods called eurypterids, or crustaceans, appeared.
The Silurian period in North America ended without major tectonic movements. However, in Western Europe at this time the Caledonian belt formed. This mountain range extended across Norway, Scotland and Ireland. Orogenesis also occurred in northern Siberia, as a result of which its territory was raised so high that it was never flooded again.
Devonian
named after the county of Devon in England, where rocks of this age were first studied. After the denudation break, certain areas of the continents again experienced subsidence and were flooded by shallow seas. In northern England and partly in Scotland, young Caledonides prevented the penetration of the sea. However, their destruction led to the accumulation of thick strata of terrigenous sandstones in the valleys of foothill rivers. This formation of ancient red sandstones is known for its well-preserved fossil fish. Southern England at this time was covered by a sea in which thick layers of limestone were deposited. Large areas in northern Europe were then flooded by seas in which layers of clayey shales and limestones accumulated. When the Rhine cut into these strata in the area of the Eifel massif, picturesque cliffs were formed that rise along the banks of the valley.
The Devonian seas covered many areas of European Russia, southern Siberia and southern China. A vast sea basin flooded central and western Australia. This area has not been covered by the sea since the Cambrian period. In South America, marine transgression extended to some central and western areas. In addition, there was a narrow sublatitudinal trough in the Amazon. Devonian breeds are very widespread in North America. During most of this period, two major geosynclinal basins existed. In the Middle Devonian, marine transgression spread to the territory of the modern river valley. Mississippi, where a multi-layered strata of limestone has accumulated.
In the Upper Devonian, thick horizons of shale and sandstone formed in the eastern regions of North America. These clastic sequences correspond to a stage of mountain building that began at the end of the Middle Devonian and continued until the end of this period. The mountains extended along the eastern flank of the Appalachian geosyncline (from the modern southeastern United States to southeastern Canada). This region was greatly uplifted, its northern part underwent folding, and then extensive granite intrusions occurred there. These granites are used to make up the White Mountains in New Hampshire, Stone Mountain in Georgia, and a number of other mountain structures. Upper Devonian, so-called The Acadian mountains were reworked by denudation processes. As a result, a layered sequence of sandstones has accumulated to the west of the Appalachian geosyncline, the thickness of which in some places exceeds 1500 m. They are widely represented in the region of the Catskill Mountains, hence the name Catskill sandstones. At the same time, mountain building appeared on a smaller scale in some areas of Western Europe. Orogenesis and tectonic uplift of the earth's surface caused marine regression at the end of the Devonian period.
During the Devonian, some important events occurred in the evolution of life on Earth. The first undisputed discoveries of land plants were made in many areas of the globe. For example, in the vicinity of Gilboa (New York), many species of ferns, including giant trees, were found.
Among the invertebrates, sponges, corals, bryozoans, brachiopods and mollusks were widespread (Fig. 12). There were several types of trilobites, although their numbers and species diversity were significantly reduced compared to the Silurian. The Devonian is often called the “age of fish” due to the magnificent flowering of this class of vertebrates. Although primitive jawless animals still existed, more advanced forms began to predominate. Shark-like fish reached a length of 6 m. At this time, lungfishes appeared, in which the swim bladder was transformed into primitive lungs, which allowed them to exist for some time on land, as well as lobe-finned and ray-finned fish. In the Upper Devonian, the first traces of land animals were discovered - large salamander-like amphibians called stegocephalians. Their skeletal features show that they evolved from lungfishes by further improving their lungs and modifying their fins into limbs.
Carboniferous period.
After some break, the continents again experienced subsidence and their low-lying areas turned into shallow seas. Thus began the Carboniferous period, which got its name from the widespread occurrence of coal deposits in both Europe and North America. In America, its early stage, characterized by marine conditions, was previously called Mississippian due to the thick layer of limestone that formed within the modern valley of the river. Mississippian, and is now attributed to the lower Carboniferous period.
In Europe, throughout the Carboniferous period, the territories of England, Belgium and northern France were mostly flooded by the sea, in which thick limestone horizons were formed. Some areas of southern Europe and southern Asia were also flooded, where thick layers of shales and sandstones were deposited. Some of these horizons are continental in origin and contain many fossil remains of terrestrial plants and also host coal-bearing strata. Since Lower Carboniferous formations are poorly represented in Africa, Australia and South America, it can be assumed that these territories were located predominantly in subaerial conditions. In addition, there is evidence of widespread continental glaciation there.
In North America, the Appalachian geosyncline was limited from the north by the Acadian Mountains, and from the south, from the Gulf of Mexico, it was penetrated by the Mississippi Sea, which also flooded the Mississippi Valley. Small sea basins occupied some areas in the west of the continent. In the Mississippi Valley region, a multilayered sequence of limestone and shale accumulated. One of these horizons, the so-called Indian limestone, or spergenite, is a good building material. It was used in the construction of many government buildings in Washington.
At the end of the Carboniferous period, mountain building became widespread in Europe. Chains of mountains stretched from southern Ireland through southern England and northern France into southern Germany. This stage of orogenesis is called Hercynian or Variscian. In North America, local uplifts occurred at the end of the Mississippian period. These tectonic movements were accompanied by marine regression, the development of which was also facilitated by glaciations of the southern continents.
In general, the organic world of the Lower Carboniferous (or Mississippian) time was the same as in the Devonian. However, in addition to a greater variety of types of tree ferns, the flora was replenished with tree mosses and calamites (tree-like arthropods of the horsetail class). Invertebrates were mainly represented by the same forms as in the Devonian. During Mississippian times, sea lilies, bottom-dwelling animals similar in shape to a flower, became more common. Among the fossil vertebrates, shark-like fish and stegocephalians are numerous.
At the beginning of the Late Carboniferous (Pennsylvanian in North America), conditions on the continents began to change rapidly. As follows from the significantly wider distribution of continental sediments, the seas occupied smaller spaces. Northwestern Europe spent most of this time in subaerial conditions. The vast epicontinental Ural Sea extended widely across northern and central Russia, and a major geosyncline extended across southern Europe and southern Asia (the modern Alps, Caucasus, and Himalayas lie along its axis). This trough, called the Tethys geosyncline, or sea, existed over a number of subsequent geological periods.
Lowlands stretched across England, Belgium and Germany. Here, as a result of small oscillatory movements of the earth's crust, an alternation of marine and continental environments occurred. As the sea receded, low-lying swampy landscapes with forests of tree ferns, tree mosses and calamites formed. As the seas advanced, sediments covered the forests, compacting woody remains, which turned into peat and then coal. In Late Carboniferous times, cover glaciation spread across the continents of the Southern Hemisphere. In South America, as a result of marine transgression penetrating from the west, most of the territory of modern Bolivia and Peru was flooded.
In early Pennsylvanian time in North America, the Appalachian geosyncline closed, lost contact with the World Ocean, and terrigenous sandstones accumulated in the eastern and central regions of the United States. During the middle and end of this period, the interior of North America (as well as Western Europe) was dominated by lowlands. Here, shallow seas periodically gave way to swamps that accumulated thick peat deposits that later transformed into large coal basins that stretch from Pennsylvania to eastern Kansas. Parts of western North America were flooded by sea during much of this period. Layers of limestone, shale and sandstone were deposited there.
The widespread occurrence of subaerial environments greatly contributed to the evolution of terrestrial plants and animals. Gigantic forests of tree ferns and club mosses covered the vast swampy lowlands. These forests abounded in insects and arachnids. One species of insect, the largest in geological history, was similar to the modern dragonfly, but had a wingspan of approx. 75 cm. Stegocephalians reached significantly greater species diversity. Some exceeded 3 m in length. In North America alone, more than 90 species of these giant amphibians, which were similar to salamanders, were discovered in swamp sediments of the Pennsylvanian period. The remains of ancient reptiles were found in these same rocks. However, due to the fragmentary nature of the finds, it is difficult to get a complete picture of the morphology of these animals. These primitive forms were probably similar to alligators.
Permian period.
Changes in natural conditions, which began in the Late Carboniferous, became even more pronounced in the Permian period, which ended the Paleozoic era. Its name comes from the Perm region in Russia. At the beginning of this period, the sea occupied the Ural geosyncline - a trough that followed the strike of the modern Ural Mountains. A shallow sea periodically covered parts of England, northern France and southern Germany, where layered strata of marine and continental sediments - sandstones, limestones, shales and rock salt - accumulated. The Tethys Sea existed for most of the period, and a thick sequence of limestones formed in the area of northern India and the modern Himalayas. Thick Permian deposits are present in eastern and central Australia and on the islands of South and Southeast Asia. They are widespread in Brazil, Bolivia and Argentina, as well as in southern Africa.
Many Permian formations in northern India, Australia, Africa and South America are of continental origin. They are represented by compacted glacial deposits, as well as widespread fluvio-glacial sands. In Central and Southern Africa, these rocks begin a thick sequence of continental sediments known as the Karoo Series.
In North America, the Permian seas occupied a smaller area compared to previous Paleozoic periods. The main transgression spread from the western Gulf of Mexico north through Mexico and into the south-central United States. The center of this epicontinental sea was located within the modern state of New Mexico, where a thick sequence of Capitanian limestones formed. Thanks to the activity of groundwater, these limestones acquired a honeycomb structure, especially pronounced in the famous Carlsbad Caverns (New Mexico, USA). Farther east, coastal red shale facies were deposited in Kansas and Oklahoma. At the end of the Permian, when the area occupied by the sea was significantly reduced, thick salt-bearing and gypsum-bearing strata were formed.
At the end of the Paleozoic era, partly in the Carboniferous and partly in the Permian, orogenesis began in many areas. Thick sedimentary rocks of the Appalachian geosyncline were folded and broken by faults. As a result, the Appalachian Mountains were formed. This stage of mountain building in Europe and Asia is called Hercynian or Variscian, and in North America - Appalachian.
The flora of the Permian period was the same as in the second half of the Carboniferous. However, the plants were smaller and not as numerous. This indicates that the Permian climate became colder and drier. The invertebrate animals of the Permian were inherited from the previous period. A great leap occurred in the evolution of vertebrates (Fig. 13). On all continents, continental sediments of Permian age contain numerous remains of reptiles, reaching a length of 3 m. All of these ancestors of Mesozoic dinosaurs were distinguished by a primitive structure and looked like lizards or alligators, but sometimes had unusual features, for example, a high sail-shaped fin extending from the neck to the tail along the back, in Dimetrodon. Stegocephalians were still numerous.
At the end of the Permian period, mountain building, which manifested itself in many areas of the globe against the background of the general uplift of continents, led to such significant changes in the environment that many characteristic representatives of the Paleozoic fauna began to die out. The Permian period was the final stage of the existence of many invertebrates, especially trilobites.
Mesozoic era,
divided into three periods, it differed from the Paleozoic in the predominance of continental settings over marine ones, as well as the composition of flora and fauna. Land plants, many groups of invertebrates, and especially vertebrates have adapted to new environments and undergone significant changes.
Triassic
opens the Mesozoic era. Its name comes from the Greek. trias (trinity) in connection with the clear three-membered structure of the sediment strata of this period in northern Germany. Red sandstones lie at the base of the sequence, limestones in the middle, and red sandstones and shales at the top. During the Triassic, large areas of Europe and Asia were occupied by lakes and shallow seas. The epicontinental sea covered Western Europe, and its coastline can be traced to England. The above-mentioned stratotype sediments accumulated in this sea basin. The sandstones occurring in the lower and upper parts of the sequence are partly of continental origin. Another Triassic sea basin penetrated into the territory of northern Russia and spread south along the Ural trough. The huge Tethys Sea then covered approximately the same territory as in the Late Carboniferous and Permian times. In this sea, a thick layer of dolomitic limestone has accumulated, which composes the Dolomites of northern Italy. In south-central Africa, most of the upper sequence of the continental Karoo Series is Triassic in age. These horizons are known for the abundance of fossil remains of reptiles. At the end of the Triassic, covers of silts and sands of continental origin formed on the territory of Colombia, Venezuela and Argentina. The reptiles found in these layers show striking similarities to the fauna of the Karoo series of southern Africa.
In North America, Triassic rocks are not as widespread as in Europe and Asia. The products of the destruction of the Appalachians - red continental sands and clays - accumulated in depressions located east of these mountains and experienced subsidence. These deposits, interbedded with lava horizons and sheet intrusions, are broken by faults and dip to the east. In the Newark Basin in New Jersey and the Connecticut River Valley, they correspond to bedrock of the Newark series. Shallow seas occupied some western areas of North America, where limestones and shales accumulated. Continental sandstones and Triassic shales emerge along the sides of the Grand Canyon (Arizona).
The organic world in the Triassic period was significantly different than in the Permian period. This time is characterized by an abundance of large coniferous trees, the remains of which are often found in Triassic continental deposits. The shales of the Chinle Formation in northern Arizona are loaded with fossilized tree trunks. Weathering of the shale has exposed them and now forms a stone forest. Cycads (or cycadophytes), plants with thin or barrel-shaped trunks and dissected leaves hanging from the top, like those of palm trees, have become widespread. Some cycad species also exist in modern tropical areas. Of the invertebrates, the most common were mollusks, among which ammonites predominated (Fig. 14), which had a vague resemblance to modern nautiluses (or boats) and a multi-chambered shell. There were many species of bivalves. Significant progress has occurred in the evolution of vertebrates. Although stegocephalians were still quite common, reptiles began to predominate, among which many unusual groups appeared (for example, phytosaurs, whose body shape was like that of modern crocodiles, and whose jaws were narrow and long with sharp conical teeth). In the Triassic, true dinosaurs first appeared, evolutionarily more advanced than their primitive ancestors. Their limbs were directed downward, rather than outward (like crocodiles), which allowed them to move like mammals and support their bodies above the ground. Dinosaurs walked on their hind legs, maintaining balance with the help of a long tail (like a kangaroo), and were distinguished by their small stature - from 30 cm to 2.5 m. Some reptiles adapted to life in the marine environment, for example, ichthyosaurs, whose body resembled a shark, and the limbs were transformed into something between flippers and fins, and plesiosaurs, whose torso became flattened, the neck elongated, and the limbs turned into flippers. Both of these groups of animals became more numerous in later stages of the Mesozoic era.
Jurassic period
got its name from the Jura Mountains (in northwestern Switzerland), composed of multi-layered strata of limestone, shales and sandstones. One of the largest marine transgressions in Western Europe occurred in the Jurassic. A huge epicontinental sea extended over most of England, France, Germany and penetrated into some western regions of European Russia. In Germany there are numerous outcrops of Upper Jurassic lagoonal fine-grained limestones in which unusual fossils have been discovered. In Bavaria, in the famous town of Solenhofen, remains of winged reptiles and both of the known species of the first birds were found.
The Tethys Sea extended from the Atlantic through the southern part of the Iberian Peninsula along the Mediterranean Sea and through South and Southeast Asia to the Pacific Ocean. Most of northern Asia during this period was located above sea level, although epicontinental seas penetrated into Siberia from the north. Continental sediments of Jurassic age are known in southern Siberia and northern China.
Small epicontinental seas occupied limited areas along the coast of western Australia. In the interior of Australia there are outcrops of Jurassic continental sediments. Most of Africa during the Jurassic period was located above sea level. The exception was its northern outskirts, which were flooded by the Tethys Sea. In South America, an elongated narrow sea filled a geosyncline located approximately on the site of the modern Andes.
In North America, the Jurassic seas occupied very limited areas in the west of the continent. Thick strata of continental sandstones and capping shales accumulated in the Colorado Plateau region, especially north and east of the Grand Canyon. Sandstones were formed from sands that made up the desert dune landscapes of the basins. As a result of weathering processes, sandstones have acquired unusual shapes (such as the picturesque pointed peaks in Zion National Park or Rainbow Bridge National Monument, which is an arch rising 94 m above the canyon floor with a span of 85 m; these attractions are located in Utah). The Morrison Shale deposits are famous for the discovery of 69 species of dinosaur fossils. Fine sediments in this area probably accumulated in swampy lowland conditions.
The flora of the Jurassic period was in general terms similar to that existing in the Triassic. The flora was dominated by cycad and coniferous tree species. For the first time, ginkgos appeared - gymnosperms, broad-leaved woody plants with leaves that fall in autumn (probably a link between gymnosperms and angiosperms). The only species of this family - ginkgo biloba - has survived to the present day and is considered the most ancient representative of the trees, truly a living fossil.
The Jurassic invertebrate fauna is very similar to the Triassic. However, reef-building corals became more numerous, and sea urchins and mollusks became widespread. Many bivalves related to modern oysters appeared. Ammonites were still numerous.
Vertebrates were represented mainly by reptiles, since stegocephalians became extinct at the end of the Triassic. Dinosaurs have reached the culmination of their development. Herbivorous forms such as Apatosaurus and Diplodocus began to move on four limbs; many had long necks and tails. These animals acquired gigantic sizes (up to 27 m in length), and some weighed up to 40 tons. Some representatives of smaller herbivorous dinosaurs, such as stegosaurs, developed a protective shell consisting of plates and spines. Carnivorous dinosaurs, in particular allosaurs, developed large heads with powerful jaws and sharp teeth; they reached a length of 11 m and moved on two limbs. Other groups of reptiles were also very numerous. Plesiosaurs and ichthyosaurs lived in the Jurassic seas. For the first time, flying reptiles appeared - pterosaurs, which developed membranous wings, like bats, and their mass decreased due to tubular bones.
The appearance of birds in the Jurassic is an important stage in the development of the animal world. Two bird skeletons and feather imprints were discovered in the lagoonal limestones of Solenhofen. However, these primitive birds still had many features in common with reptiles, including sharp, conical teeth and long tails.
The Jurassic period ended with intense folding, which resulted in the formation of the Sierra Nevada Mountains in the western United States, which extended further north into modern western Canada. Subsequently, the southern part of this folded belt again experienced uplift, which predetermined the structure of modern mountains. On other continents, manifestations of orogenesis in the Jurassic were insignificant.
Cretaceous period.
At this time, thick layered strata of soft, weakly compacted white limestone—chalk—accumulated, from which the period got its name. For the first time, such layers were studied in outcrops along the shores of the Pas-de-Calais Strait near Dover (Great Britain) and Calais (France). In other parts of the world, sediments of this age are also called Cretaceous, although other types of rocks are also found there.
During the Cretaceous period, marine transgressions covered large parts of Europe and Asia. In central Europe, the seas filled two sublatitudinal geosynclinal troughs. One of them was located within southeastern England, northern Germany, Poland and western regions of Russia and in the extreme east reached the submeridional Ural trough. Another geosyncline, Tethys, maintained its previous strike in southern Europe and northern Africa and connected with the southern tip of the Ural trough. Further, the Tethys Sea continued in South Asia and east of the Indian Shield it connected with the Indian Ocean. With the exception of the northern and eastern margins, the territory of Asia was not flooded by the sea throughout the entire Cretaceous period, so continental deposits of this time are widespread there. Thick layers of Cretaceous limestone are present in many areas of Western Europe. In the northern regions of Africa, where the Tethys Sea entered, large strata of sandstones accumulated. The sands of the Sahara Desert were formed mainly due to the products of their destruction. Australia was covered by Cretaceous epicontinental seas. In South America, during most of the Cretaceous period, the Andean trough was flooded by the sea. To the east, terrigenous silts and sands with numerous remains of dinosaurs were deposited over a large area of Brazil.
In North America, marginal seas occupied the coastal plains of the Atlantic Ocean and the Gulf of Mexico, where sands, clays and cretaceous limestones accumulated. Another marginal sea was located on the western coast of the mainland within California and reached the southern foot of the revived Sierra Nevada mountains. However, the most recent major marine transgression occurred in western central North America. At this time, a vast geosynclinal trough of the Rocky Mountains formed, and a huge sea spread from the Gulf of Mexico through the modern Great Plains and Rocky Mountains north (west of the Canadian Shield) all the way to the Arctic Ocean. During this transgression, a thick layered sequence of sandstones, limestones and shales was deposited.
At the end of the Cretaceous period, intense orogeny occurred in South and North America and East Asia. In South America, sedimentary rocks accumulated in the Andean geosyncline over several periods were compacted and folded, leading to the formation of the Andes. Similarly, in North America, the Rocky Mountains formed at the site of a geosyncline. Volcanic activity has increased in many areas of the world. Lava flows covered the entire southern part of the Hindustan Peninsula (thus forming the vast Deccan Plateau), and small outpourings of lava took place in Arabia and East Africa. All continents experienced significant uplifts, and regression of all geosynclinal, epicontinental and marginal seas occurred.
The Cretaceous period was marked by several major events in the development of the organic world. The first flowering plants appeared. Their fossil remains are represented by leaves and wood of species, many of which still grow today (for example, willow, oak, maple and elm). The Cretaceous invertebrate fauna is generally similar to the Jurassic. Among vertebrates, the species diversity of reptiles reached a culmination. There were three main groups of dinosaurs. Carnivores with well-developed massive hind limbs were represented by tyrannosaurs, which reached 14 m in length and 5 m in height. A group of bipedal herbivorous dinosaurs (or trachodonts) with wide flattened jaws, reminiscent of a duck's beak, developed. Numerous skeletons of these animals are found in the Cretaceous continental deposits of North America. The third group includes horned dinosaurs with a developed bony shield that protected the head and neck. A typical representative of this group is Triceratops with a short nasal and two long supraorbital horns.
Plesiosaurs and ichthyosaurs lived in the Cretaceous seas, and sea lizards called mosasaurs with an elongated body and relatively small flipper-like limbs appeared. Pterosaurs (flying lizards) lost their teeth and moved better in air space than their Jurassic ancestors. One type of pterosaur, the pteranodon, had a wingspan of up to 8 m.
There are two known species of birds of the Cretaceous period that retained some morphological features of reptiles, for example, conical teeth located in the alveoli. One of them, hesperornis (a diving bird), has adapted to life in the sea.
Although transitional forms more similar to reptiles than to mammals have been known since the Triassic and Jurassic, numerous remains of true mammals were first discovered in continental Upper Cretaceous sediments. The primitive mammals of the Cretaceous period were small in size and somewhat reminiscent of modern shrews.
Widespread mountain building processes on Earth and tectonic uplifts of continents at the end of the Cretaceous period led to such significant changes in nature and climate that many plants and animals became extinct. Among the invertebrates, the ammonites that dominated the Mesozoic seas disappeared, and among the vertebrates, all dinosaurs, ichthyosaurs, plesiosaurs, mosasaurs and pterosaurs disappeared.
Cenozoic era,
covering the last 65 million years, is divided into Tertiary (in Russia it is customary to distinguish two periods - Paleogene and Neogene) and Quaternary periods. Although the latter was of short duration (age estimates of its lower limit range from 1 to 2.8 million years), it played a great role in the history of the Earth, since repeated continental glaciations and the appearance of humans are associated with it.
Tertiary period.
At this time, many areas of Europe, Asia and North Africa were covered by shallow epicontinental and deep geosynclinal seas. At the beginning of this period (in the Neogene), the sea occupied southeastern England, northwestern France and Belgium, and a thick layer of sands and clays accumulated there. The Tethys Sea still existed, stretching from the Atlantic to the Indian Ocean. Its waters flooded the Iberian and Apennine peninsulas, the northern regions of Africa, southwest Asia and the north of Hindustan. Thick limestone horizons were deposited in this basin. Much of northern Egypt is composed of nummulitic limestones, which were used as building material in the construction of the pyramids.
At this time, almost all of southeast Asia was occupied by marine basins and a small epicontinental sea extended to the southeast of Australia. Tertiary marine basins covered the northern and southern ends of South America, and the epicontinental sea penetrated into eastern Colombia, northern Venezuela, and southern Patagonia. Thick strata of continental sands and silts accumulated in the Amazon basin.
The marginal seas were located on the site of the modern Coastal Plains adjacent to the Atlantic Ocean and the Gulf of Mexico, as well as along the western coast of North America. Thick strata of continental sedimentary rocks, formed as a result of denudation of the revived Rocky Mountains, accumulated on the Great Plains and in the intermountain basins.
In many areas of the globe, active orogenesis occurred in the middle of the Tertiary period. The Alps, Carpathians and Caucasus formed in Europe. In North America, during the final stages of the Tertiary period, the Coast Ranges (within the modern states of California and Oregon) and the Cascade Mountains (within Oregon and Washington) were formed.
The Tertiary period was marked by significant progress in the development of the organic world. Modern plants arose back in the Cretaceous period. Most tertiary invertebrates were directly inherited from Cretaceous forms. Modern bony fish have become more numerous, and the number and species diversity of amphibians and reptiles have decreased. There was a leap in the development of mammals. From primitive forms similar to shrews and first appearing in the Cretaceous period, many forms originate, dating back to the beginning of the Tertiary period. The most ancient fossil remains of horses and elephants were found in the Lower Tertiary rocks. Carnivores and even-toed ungulates appeared.
The species diversity of animals increased greatly, but many of them became extinct by the end of the Tertiary period, while others (like some Mesozoic reptiles) returned to a marine lifestyle, such as cetaceans and porpoises, whose fins are transformed limbs. Bats were able to fly thanks to a membrane connecting their long fingers. Dinosaurs, which went extinct at the end of the Mesozoic, gave way to mammals, which became the dominant class of animals on land at the beginning of the Tertiary period.
Quaternary period
divided into Eopleistocene, Pleistocene and Holocene. The latter began just 10,000 years ago. The modern relief and landscapes of the Earth were mainly formed in the Quaternary period.
Mountain building, which occurred at the end of the Tertiary period, predetermined a significant rise of continents and regression of the seas. The Quaternary period was marked by a significant cooling of the climate and the widespread development of glaciation in Antarctica, Greenland, Europe and North America. In Europe, the center of glaciation was the Baltic Shield, from where the ice sheet extended to southern England, central Germany and the central regions of Eastern Europe. In Siberia, cover glaciation was smaller, mainly limited to foothill areas. In North America, ice sheets covered a vast area, including most of Canada and the northern United States as far south as Illinois. In the Southern Hemisphere, the Quaternary ice sheet is characteristic not only of Antarctica, but also of Patagonia. In addition, mountain glaciation was widespread on all continents.
In the Pleistocene, there are four main stages of intensified glaciation, alternating with interglacial periods, during which natural conditions were close to modern or even warmer. The last ice cover in Europe and North America reached its greatest extent 18–20 thousand years ago and finally melted at the beginning of the Holocene.
During the Quaternary period, many tertiary forms of animals became extinct and new ones appeared, adapted to colder conditions. Of particular note are the mammoth and woolly rhinoceros, which inhabited the northern regions in the Pleistocene. In the more southern regions of the Northern Hemisphere, mastodons, saber-toothed tigers, etc. were found. When the ice sheets melted, representatives of the Pleistocene fauna died out and modern animals took their place. Primitive people, in particular Neanderthals, probably existed already during the last interglacial, but modern humans - Homo sapiens - appeared only in the last glacial epoch of the Pleistocene, and in the Holocene settled throughout the globe.
Literature:
Strakhov N.M. Types of lithogenesis and their evolution in the history of the Earth. M., 1965
Allison A., Palmer D. Geology. The Science of an Ever-Changing Earth. M., 1984
Existed at different times in geological history.
tectonic situation and the nature of the past, the development of the earth's crust, the history of the origin and development - uplifts, troughs, folds, faults and other tectonic elements.
Historical geology is one of the major branches of geological sciences, which examines the geological past of the Earth in chronological order. Since the earth's crust is still accessible to geological observations, consideration of various natural phenomena and processes extends to the earth's crust. The formation of the Earth's crust is determined by a variety of factors, the leading ones being time, physiographic conditions and tectonics. Therefore, to restore the history of the earth’s crust, the following tasks are solved:
Determining the age of rocks.
Restoration of the physical and geographical conditions of the earth's surface of the past.
Reconstruction of tectonic movements and various tectonic structures
Determination of the structure and patterns of development of the earth's crust
1. Includes the study of the composition, place and time of formation of rock layers and their correlation. It is solved by the branch of historical geology - stratigraphy.
2. Considers climate, relief, development of ancient seas, rivers, lakes, etc. in past geological epochs. All these questions are considered by paleogeography.
3. Tectonic movements change the primary occurrence of rocks. They occur as a result of horizontal or vertical movements of individual blocks of the earth's crust. Geotectonics deals with determining the time, nature, and magnitude of tectonic movements. Tectonic movements are accompanied by the manifestation of magmatic activity. Petrology reconstructs the time and conditions for the formation of igneous rocks.
4. Solved on the basis of analysis and synthesis of the results of solving the first three problems.
All main tasks are closely interconnected and are solved in parallel using various methods.
As a science, historical geology began to take shape at the turn of the 18th-19th centuries, when W. Smith in England, and J. Cuvier and A. Brongniard in France came to the same conclusions about the successive change of layers and the remains of fossil organisms located in them. Based on the biostratigraphic method, the first stratigraphic columns, sections reflecting the vertical sequence of sedimentary rocks, were compiled. The discovery of this method marked the beginning of the stratigraphic stage in the development of historical geology. During the first half of the 19th century, almost all the main divisions of the stratigraphic scale were established, the geological material was systematized in chronological sequence, and a stratigraphic column was developed for all of Europe. During this period, the idea of catastrophism dominated in geology, which connected all the changes occurring on Earth (changes in the occurrence of strata, the formation of mountains, the extinction of some types of organisms and the emergence of new ones, etc.) with major disasters.
The idea of catastrophes is replaced by the doctrine of evolution, which considers all changes on Earth as the result of very slow and long-term geological processes. The founders of the doctrine are J. Lamarck, C. Lyell, C. Darwin.
By the middle of the 19th century. These include the first attempts to reconstruct physical and geographical conditions for individual geological epochs for large land areas. These works, carried out by scientists J. Dana, V.O. Kovalevsky and others, laid the foundation for the paleogeographical stage in the development of historical geology. The introduction of the concept of facies by the scientist A. Gressley in 1838 played a major role in the development of paleogeography. Its essence lies in the fact that rocks of the same age can have different compositions, reflecting the conditions of their formation.
In the second half of the 19th century. The idea of geosynclines as extended troughs filled with thick layers of sedimentary rocks is emerging. And by the end of the century A.P. Karpinsky lays the foundations of the doctrine of platforms.
The idea of platforms and geosynclines as the main elements of the structure of the Earth's crust gives rise to the third “tectonic” stage in the development of historical geology. It was first outlined in the works of the scientist E. Og “Geosynclines and Continental Areas.” In Russia, the concept of geosynclines was introduced by F.Yu. Levinson-Lessing at the beginning of the 20th century.
Thus, we see that until the mid-20th century. historical geology developed with the predominance of one scientific direction. At the present stage, historical geology is developing in two directions. The first direction is a detailed study of the geological history of the Earth in the field of stratigraphy, paleogeography and tectonics. At the same time, old research methods are being improved and new ones are being used, such as: deep and ultra-deep drilling, geophysical, paleomagnetic; space sensing, absolute geochronology, etc.
The second direction is work to create a holistic picture of the geological history of the earth’s crust, identify patterns of development and establish a causal relationship between them.
1. The method of ribbon clays is based on the phenomenon of changes in the composition of sediments that are deposited in a calm water basin during seasonal climate change. In 1 year, 2 layers are formed. In the autumn-winter season, a layer of clay rocks is deposited, and in the spring-summer season, a layer of sandy rocks is formed. Knowing the number of such pairs of layers, one can determine how many years it took for the entire thickness to form.
2.Methods of nuclear geochronology
These methods rely on the phenomenon of radioactive decay of elements. The rate of this decay is constant and does not depend on any conditions occurring on Earth. During radioactive decay, the mass of radioactive isotopes changes and the decay products - radiogenic stable isotopes - accumulate. Knowing the half-life of a radioactive isotope, you can determine the age of the mineral containing it. To do this, you need to determine the relationship between the content of the radioactive substance and its decay product in the mineral.
In nuclear geochronology the main ones are:
Lead method - the process of decay of 235U, 238U, 232Th into isotopes 207Pb and 206Pb, 208Pb is used. The minerals used are monazite, orthite, zircon and uraninite. Half-life ~4.5 billion years.
Potassium-argon - during the decay of K, the isotopes 40K (11%) turn into argon 40Ar, and the rest into the isotope 40Ca. Since K is present in rock-forming minerals (feldspars, micas, pyroxenes and amphiboles), the method is widely used. Half-life ~1.3 billion. years.
Rubidium-strontium - the isotope of rubidium 87Rb is used to form the isotope of strontium 87Sr (the minerals used are mica containing rubidium). Due to its long half-life (49.9 billion years), it is used for the most ancient rocks of the earth's crust.
Radiocarbon - used in archaeology, anthropology and the youngest sediments of the Earth's crust. The radioactive carbon isotope 14C is formed by the reaction of cosmic particles with nitrogen 14N and accumulates in plants. After their death, carbon 14C decays, and the rate of decay determines the time of death of the organisms and the age of the host rocks (half-life 5.7 thousand years).
The disadvantages of all these methods include:
low accuracy of determinations (an error of 3-5% gives a deviation of 10-15 million years, which does not allow the development of fractional stratification).
distortion of results due to metamorphism, when a new mineral is formed, similar to the mineral of the parent rock. For example, sericite-muscovite.
Nevertheless, nuclear methods have a great future, since equipment is constantly being improved, allowing more reliable results to be obtained. Thanks to these methods, it was established that the age of the Earth's crust exceeds 4.6 billion years, whereas before the use of these methods it was estimated only at tens and hundreds of millions of years.
Relative geochronology determines the age of rocks and the sequence of their formation by stratigraphic methods, and the section of geology that studies the relationships of rocks in time and space is called stratigraphy (from Latin stratum-layer + Greek grapho).
biostratigraphic or paleontological,
not paleontological.
Paleontological methods (biostratigraphy)
The method is based on determining the species composition of fossil remains of ancient organisms and the idea of the evolutionary development of the organic world, according to which ancient deposits contain the remains of simple organisms, and younger ones contain organisms of complex structure. This feature is used to determine the age of rocks.
For geologists, an important point is that evolutionary changes in organisms and the emergence of new species occur over a certain period of time. The boundaries of evolutionary transformations are the boundaries of the geological time of accumulation of sedimentary layers and horizons.
The method of determining the relative age of layers using leading fossils is called the leading fossil method. According to this method, layers that contain similar guiding forms are coeval. This method became the first paleontological method for determining the age of rocks. On its basis, the stratigraphy of many regions was developed.
To avoid mistakes, along with this method, the method of paleontological complexes is used. In this case, the entire complex of extinct organisms found in the studied strata is used. In this case, the following can be distinguished:
1-fossil forms that lived in only one layer; 2-forms that first appeared in the layer under study and pass into the overlying one (the lower boundary of the layer is drawn); 3-forms passing from the lower layer and ending their existence in the studied layer (surviving forms); 4-forms that lived in the lower or upper layer, but were not found in the studied layer (upper and lower boundaries of the layer).
Non-paleontological methods
The main ones are divided into:
lithological
structural-tectonic
geophysical
Lithological methods for separating strata are based on differences in individual layers that make up the strata under study in color, material composition (mineralogical and petrographic), and textural features. Among the layers and units in the section, there are those that differ sharply in these properties. Such layers and units are easily identified in adjacent outcrops and can be traced over long distances. They are called the marking horizon. The method of dividing sedimentary strata into individual units and layers is called the marking horizon method. For certain regions or age intervals, the marker horizon can be interlayers of limestone, siliceous shales, conglomerates, etc.
The mineralogical-petrographic method is used when there is no marker horizon and the sedimentary strata is quite uniform in lithological composition; then, to compare individual layers in the section and their relative age, they rely on the mineralogical-petrographic features of individual layers. For example, minerals such as rutile, garnet, zircon were identified in several layers of sandstone and their % content was determined. Based on the quantitative ratio of these minerals, the thickness is divided into separate layers or horizons. The same operation is carried out in an adjacent section, and then the results are compared with each other and the layers in the section are correlated. The method is labor-intensive - it is necessary to select and analyze a large number of samples. At the same time, the method is applicable for small areas.
Structural-tectonic method - it is based on the idea of the existence of breaks in sedimentation in large areas of the earth's crust. Breaks in sedimentation occur when the area of the sea basin where sediment accumulated becomes elevated and the formation of sediments stops there for this period. In subsequent geological times, this area may begin to sink again, again becoming a sea basin in which new sedimentary strata accumulate. The boundary between the strata is a surface of unconformity. Using such surfaces, the sedimentary sequence is divided into units and compared in adjacent sections. Sequences contained between identical unconformity surfaces are considered to be of the same age. In contrast to the lithological method, the structural-tectonic method is used to compare large stratigraphic units in strata.
A special case of the structural-tectonic method is the method of rhythmostratigraphy. In this case, the sedimentary section is divided into units that were formed in the basin during alternating subsidence and uplift of the sedimentation surface, which was accompanied by the advance and retreat of the sea. This alternation was reflected in the sedimentary strata as a sequential change of horizons of deep-water rocks to shallow-water ones and vice versa. If such a sequential change of horizons is observed repeatedly in a section, then each of them is distinguished into a rhythm. And according to such rhythms, stratigraphic sections within one sedimentation basin are compared. This method is widely used to correlate sections of thick coal-bearing strata.
The process of formation of igneous bodies is accompanied by their intrusion into the sedimentary strata of rocks. Therefore, the basis for determining their age is the study of the relationships between the igneous and vein bodies and the sedimentary rock units that they intersected and whose age is established.
Geophysical methods are based on comparing rocks by physical properties. In their geological essence, geophysical methods are close to the mineralogical-petrographic method, since in this case, individual horizons are identified, their physical parameters are compared, and sections are correlated using them. Geophysical methods are not independent in nature, but are used in combination with other methods.
The considered methods of absolute and relative geochronology made it possible to determine the age and sequence of formation of rocks, as well as to establish the periodicity of geological phenomena and identify stages in the long history of the Earth. During each stage, rock strata accumulated successively, and this accumulation occurred over a certain period of time. Therefore, any geochronological classification contains double information and combines two scales - stratigraphic and geochronological. The stratigraphic scale reflects the sequence of accumulation of strata, and the geochronological scale reflects the time period corresponding to this process.
Based on a large amount of data from various regions and continents, the International Geochronological Scale, common to the earth’s crust, was created, reflecting the sequence of time divisions during which certain complexes of sediments were formed and the evolution of the organic world.
In stratigraphy, units are considered from large to small:
eonothema - group - system - department - tier. They correspond
eon - era - period - epoch - century
