Historical geology and the past of the earth. Historical Geology: Fundamentals of Science, Founding Scientists, Review of Literature Historical Geology

The most ancient rocks exposed on the surface of the 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 it is often impossible to restore their original character. During numerous long stages of denudation, thick strata of these rocks were destroyed, and the remaining ones 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, while 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 the Hudson Bay. Although in places the Archean rocks are overlain by younger ones, they form the day surface in most of the territory of the Canadian Shield. The oldest known rocks in this area are represented by marbles, slates and crystalline schists interbedded with lavas. Initially, limestones and shales were deposited here, later sealed by lavas. Then these rocks experienced the impact of powerful tectonic movements, which were accompanied by large granite intrusions. Ultimately, the sedimentary rock strata underwent strong metamorphism. After a long period of denudation, these highly metamorphosed rocks were brought to the surface in places, but granites form the general background.

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. The younger rocks there are destroyed by denudation.
In Europe, Archean rocks are exposed on the territory of 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 found in the 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, some parts of the continents experienced subsidence and were flooded by shallow seas, and some low-lying basins began to be filled with continental deposits. In North America, the most significant exposures of Proterozoic rocks are found in four regions. The first of them is confined to the southern part of the Canadian Shield, where thick strata of shales and sandstones of the age under consideration are exposed around the lake. Upper and northeast of the lake. Huron. These rocks are of both marine and continental origin. Their distribution indicates that the position of the shallow seas changed significantly during the Proterozoic. In many places, marine and continental sediments are interbedded with thick lava sequences. At the end of sedimentation, tectonic movements of the earth's crust took place, the Proterozoic rocks underwent folding, and large mountain systems were formed. In the foothills east of the Appalachians, there are numerous outcrops of Proterozoic rocks. Initially, they were deposited in the form of layers of limestone and shale, and then during orogeny (mountain building) they metamorphosed and turned into marble, slate and crystalline schists. In the Grand Canyon area, a thick sequence of Proterozoic sandstones, shales, and limestones unconformably overlies Archean rocks. In the northern part of the Rocky Mountains, a sequence of Proterozoic limestones with a thickness of approx. 4600 m. Although the Proterozoic formations in these areas were affected by tectonic movements and were crumpled into folds and broken by faults, these movements were not intense enough and could not lead to rock metamorphism. 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 the northwest of Scotland, a thick stratum of Proterozoic sandstones overlies Archean granites and crystalline schists. Extensive outcrops of Proterozoic rocks are found in western China, central Australia, southern Africa, and central South America. In Australia, these rocks are represented by a thick sequence of non-metamorphosed sandstones and shales, while in eastern Brazil and southern Venezuela, they are strongly metamorphosed slates and crystalline schists.

Fossil blue-green algae Collenia are very widespread on all continents in non-metamorphosed limestones of the Proterozoic age, where a few fragments of shells of primitive mollusks have also been found. However, the remains of animals are very rare, and this indicates that most organisms were distinguished by a primitive structure and did not yet have hard shells that are preserved in a fossil state. Although traces of ice ages are recorded for the early stages of the history of the Earth, 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 inundated by shallow seas. As a result of the denudation of elevated areas, sedimentary material was carried by water flows into the geosyncline, where strata of Paleozoic sedimentary rocks with a thickness of more than 12 km accumulated. In North America, two large geosynclines formed at the beginning of the Paleozoic era. One of them, called the Appalachian, stretched from the northern part of the 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 with the Pacific, passing somewhat east of Alaska 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 partly 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 was deposited in geosynclines washed out from adjacent elevated regions.

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. There are also large outcrops of Paleozoic rocks in Siberia, China, and northern India. They are native to most parts 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 mainland 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 have occurred in Australia and central South America. The Cambrian was distinguished by rather calm tectonic settings.
In the deposits of this period, the first numerous fossils were preserved, indicating the development of life on Earth. Although no land plants or animals have been recorded, the shallow epicontinental seas and flooded geosynclines abounded with numerous invertebrates and aquatic plants. The most unusual and interesting animals of that time - trilobites (Fig. 11), a class of extinct primitive arthropods, 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 the main forms of invertebrate organisms were present in the Cambrian seas (with the exception of corals, bryozoans, and pelecypods).

At the end of the Cambrian, most of the land was uplifted and a brief marine regression took place.

Ordovician period

- the second period of the Paleozoic era (named after the Celtic tribe of the Ordovicians, who 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 the territory of North America was flooded by the sea, in which powerful strata of limestone and shale were deposited. The sea also covered significant 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, jawless (ostracoderms), were found, which lacked real jaws and paired limbs, and the front part of the body was covered with bone plates that formed a protective shell.

Based on the paleomagnetic study of the rocks, it was established that during most of the Paleozoic, North America was located in the equatorial zone. Fossil organisms and widespread limestones of this time testify to the predominance of warm shallow seas in the Ordovician. Australia was located near the South Pole, and northwestern Africa - in the region of the pole itself, which is confirmed by the signs of widespread glaciation imprinted in the Ordovician rocks of Africa.

At the end of the Ordovician period, as a result of tectonic movements, the uplift of the continents and marine regression took place. In places, the original Cambrian and Ordovician rocks experienced a folding process that was accompanied by mountain growth. This oldest stage of orogeny is called the Caledonian folding.

Silurian.

For the first time, the rocks of this period were also studied in Wales (the name of the period comes from the Celtic Silur tribe that 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 ​​the seas decreased significantly, but in the Middle Silurian, they occupied almost 60% of its territory. A thick layer of marine limestones of the Niagara Formation was formed, which got its name from the Niagara Falls, the threshold of which it forms. In the late Silurian, the areas of the seas were greatly reduced. In a strip stretching from the modern state of Michigan to the central part of the state of New York, powerful salt-bearing layers accumulated.

In Europe and Asia, the Silurian seas were widespread and occupied almost the same territories as the Cambrian seas. The same isolated massifs remained unflooded as in the Cambrian, as well as large areas of northern China and Eastern Siberia. In Europe, thick limestone strata accumulated along the periphery of the southern tip of the Baltic Shield (at present they are partially flooded by the Baltic Sea). Small seas were common in eastern Australia, northern Africa and in the central regions of South America.

In the Silurian rocks, in general, the same main representatives of the organic world were found as in the Ordovician. Terrestrial plants did not yet appear in the Silurian. Among the invertebrates, corals have become much more abundant, as a result of which massive coral reefs have formed in many areas. Trilobites, so characteristic of the Cambrian and Ordovician rocks, are losing their dominant significance: they are becoming smaller both in quantitative and species terms. At the end of the Silurian, many large aquatic arthropods appeared, called eurypterids, or crustaceans.

The Silurian period in North America ended without major tectonic movements. However, in Western Europe at this time the Caledonian belt was formed. This mountain range stretched across Norway, Scotland and Ireland. Orogeny also took place 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 the rocks of this age were first studied. After a denudation break, separate areas of the continents again experienced subsidence and were flooded by shallow seas. In northern England and partly in Scotland, young Caledonians 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 ancient red sandstone formation is known for its well-preserved fossil fish. Southern England at that time was covered by the sea, in which thick layers of limestone were deposited. Significant territories in the north of Europe were then flooded by the seas, in which layers of shale and limestone 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 the European part of 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 has spread to some central and western regions. In addition, there was a narrow sublatitudinal trough in the Amazon. Devonian rocks are very widespread in North America. For most of this period, there were two major geosynclinal basins. In the Middle Devonian, marine transgression spread to the territory of the modern valley of the river. Mississippi, where a multi-layer limestone stratum has accumulated.

In the Upper Devonian, thick horizons of shales and sandstones formed in the eastern regions of North America. These clastic strata correspond to the stage of mountain building, which 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 present-day southeastern United States to southeastern Canada). This region was strongly uplifted, its northern part underwent folding, then extensive granite intrusions occurred there. These granites form 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 stratum of sandstones has accumulated to the west of the Appalachian geosyncline, the thickness of which in places exceeds 1500 m. They are widely represented in the area of ​​the Catskill Mountains, from which the name of the Catskill sandstones came from. On a smaller scale, mountain building at the same time manifested itself in some areas of Western Europe. Orogeny and tectonic uplifts of the earth's surface caused a marine regression at the end of the Devonian period.

The Devonian saw some important developments in the evolution of life on Earth. In many parts of the world, the first indisputable finds of terrestrial plants were discovered. For example, in the vicinity of Gilboa, New York, many species of ferns, including giant trees, have been 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 referred to as the "Age of the Fish" due to the lush flowering of this class of vertebrates. Although primitive jawless ones still existed, more advanced forms began to predominate. Shark-like fish reached a length of 6 m. At this time, lungfish appeared, in which the swim bladder was transformed into primitive lungs, which allowed them to exist for some time on land, as well as cross-finned and ray-finned. In the Upper Devonian, the first traces of terrestrial animals were found - large salamander-like amphibians called stegocephals. Skeletal features show that they evolved from lungfish by further improvement of the lungs and modification of the fins and their transformation into limbs.

Carboniferous period.

After a 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 maritime conditions, was formerly called the Mississippian due to the thick limestone stratum that formed within the modern valley of the river. Mississippi, and now it is attributed to the lower section of the Carboniferous.

In Europe, during the entire Carboniferous period, the territories of England, Belgium and northern France were mostly flooded by the sea, in which powerful 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 of continental origin and contain many fossils of terrestrial plants, as well as contain coal-bearing seams. Since the Lower Carboniferous formations are poorly represented in Africa, Australia, and South America, it can be assumed that these territories were predominantly in subaerial conditions. In addition, there is evidence of widespread continental glaciation there.

In North America, the Appalachian geosyncline was bounded 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 mainland. In the area of ​​the Mississippi Valley, a multi-layered stratum of limestones and shales accumulated. One of these horizons, the so-called. Indiana 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 was widely manifested in Europe. Mountain ranges stretched from southern Ireland through southern England and northern France to southern Germany. This stage of orogeny is called the Hercynian, or Varisian. 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 the glaciation 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-like ferns, the flora was replenished with tree-like club mosses and calamites (tree-like arthropods of the horsetail class). Invertebrates were mainly represented by the same forms as in the Devonian. In the Mississippian time, sea lilies became more common - benthic animals similar in shape to a flower. Among fossil vertebrates, shark-like fishes 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 much wider distribution of continental sediments, the seas occupied smaller spaces. Northwestern Europe was in subaerial conditions for most of this time. The vast epicontinental Ural Sea spread widely in northern and central Russia, and a large geosyncline extended through southern Europe and southern Asia (the modern Alps, the Caucasus and the Himalayas are located along its axis). This trough, called the geosyncline, or sea, Tethys, existed for a number of subsequent geological periods.

On the territory of England, Belgium and Germany stretched lowlands. Here, as a result of small oscillatory movements of the earth's crust, an alternation of marine and continental settings occurred. When the sea receded, low-lying swampy landscapes formed with forests of tree ferns, tree clubs and calamites. With the advancing of the seas, sedimentary formations blocked the forests, compacting the woody residues, which turned into peat, and then into coal. In the Late Carboniferous, glaciation spread on 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 the early Pennsylvanian time in North America, the Appalachian geosyncline closed, lost its connection with the World Ocean, and terrigenous sandstones accumulated in the eastern and central regions of the United States. In the middle and end of this period, the interior of North America (as well as in Western Europe) was dominated by lowlands. Here, shallow seas periodically gave way to marshes, in which powerful peat deposits accumulated, subsequently transformed into large coal basins that stretch from Pennsylvania to eastern Kansas. Some of the western regions of North America were inundated by the sea during most of this period. Layers of limestones, shales and sandstones were deposited there.

The wide distribution of subaerial environments greatly contributed to the evolution of terrestrial plants and animals. Giant forests of tree ferns and club mosses covered the vast swampy lowlands. These forests abounded with insects and arachnids. One of the insect species, the largest in geological history, was similar to a modern dragonfly, but had a wingspan of approx. 75 cm. Significantly greater species diversity was achieved by stegocephals. Some exceeded 3 m in length. In North America alone, more than 90 species of these giant amphibians, resembling salamanders, were found in the swamp deposits of the Pennsylvanian time. In the same rocks, the remains of the most ancient reptiles were found. However, due to the fragmentary nature of the finds, it is difficult to form a complete picture of the morphology of these animals. Probably, these primitive forms were 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. The shallow sea periodically covered some areas of England, northern France and southern Germany, where layered strata of marine and continental sediments accumulated - sandstones, limestones, shale and rock salt. The Tethys Sea existed for most of the period, and a thick limestone stratum was formed in the region of northern India and the modern Himalayas. Thick Permian deposits are found in eastern and central Australia and on the islands of South and Southeast Asia. They are widely distributed 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 water-glacial sands. In Central and South Africa, these rocks begin a thick sequence of continental deposits, known as the Karoo series.

In North America, the Permian seas occupied a smaller area compared to previous periods of the Paleozoic. The main transgression spread from the western part of the Gulf of Mexico to the north through the territory of Mexico and penetrated into the southern regions of the central part of the United States. The center of this epicontinental sea was located within the modern state of New Mexico, where a thick series of limestones of the Capiten series was formed. Thanks to the activity of groundwater, these limestones acquired a honeycomb structure, which is especially pronounced in the famous Carlsbad Caves (New Mexico, USA). To the east, in Kansas and Oklahoma, coastal red shale facies were deposited. At the end of the Permian, when the area occupied by the sea was significantly reduced, powerful saline and gypsum-bearing strata formed.

At the end of the Paleozoic era, partly in the Carboniferous and partly in the Permian, orogeny began in many areas. Thick strata of sedimentary rocks of the Appalachian geosyncline were crumpled into folds 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 Varisian, 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 climate of the Permian period became colder and drier. The invertebrates of the Permian were inherited from the previous period. A great leap has taken place in the evolution of vertebrates (Fig. 13). On all continents, Permian continental deposits contain numerous remains of reptiles, reaching a length of 3 m. All these ancestors of the Mesozoic dinosaurs were distinguished by a primitive structure and outwardly looked like lizards or alligators, but sometimes had unusual features, for example, a high sail-like fin, stretching from neck to tail along the back, in Dimetrodon. Stegocephalians were still numerous.

At the end of the Permian period, mountain building, which manifested itself in many regions of the globe against the background of a general uplift of the 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 in the existence of many invertebrates, especially trilobites.

mesozoic era,

subdivided into three periods, differed from the Paleozoic in the predominance of continental settings over marine ones, as well as in the composition of flora and fauna. Terrestrial plants, many groups of invertebrates, and especially vertebrates, have adapted to new environments and have undergone significant changes.

Triassic

opens the Mesozoic era. Its name comes from the Greek. trias (trinity) in connection with a clear three-membered structure of the stratum of deposits of this period in northern Germany. Red-colored sandstones occur at the base of the sequence, limestones in the middle, and red-colored 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 the territory of England. The aforementioned stratotype sediments accumulated in this marine basin. The sandstones occurring in the lower and upper parts of the sequence are partly of continental origin. Another Triassic marine basin penetrated the territory of northern Russia and spread to the south along the Ural trough. The huge Tethys Sea then covered approximately the same territory as in the Late Carboniferous and Permian times. A thick layer of dolomitic limestones has accumulated in this sea, which form the Dolomites of northern Italy. In south-central Africa, most of the upper sequence of the Karoo continental series is of Triassic age. These horizons are known for the abundance of reptile fossils. At the end of the Triassic, covers of silts and sands of continental genesis formed on the territory of Colombia, Venezuela and Argentina. The reptiles found in these layers show a striking resemblance to the fauna of the Karoo series in southern Africa.

In North America, Triassic rocks are not as widespread as in Europe and Asia. The destruction products of the Appalachians - red-colored continental sands and clays - accumulated in depressions located to the east of these mountains and experienced subsidence. These deposits, interbedded with lava horizons and sheet intrusions, are fractured and dip to the east. In the Newark Basin in New Jersey and the Connecticut River Valley, they correspond to bedrocks of the Newark series. Shallow seas occupied some of the western regions of North America, where limestone and shale accumulated. Continental sandstones and shales of the Triassic emerge along the sides of the Grand Canyon (in Arizona).

The organic world in the Triassic period was essentially 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. Shales of the Chinle Formation in northern Arizona are saturated with silicified tree trunks. As a result of the weathering of the shales, they were exposed and now form a stone forest. Cycads (or cycadophytes), plants with thin or barrel-shaped trunks and leaves hanging from the crown dissected, like those of palm trees, were widely developed. Some species of cycads also exist in modern tropical regions. Of the invertebrates, the most common were mollusks, among which ammonites predominated (Fig. 14), which had a distant resemblance to modern nautiluses (or boats) and a multi-chambered shell. There were many types of bivalves. Significant progress has taken place 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 the jaws are narrow and long with sharp conical teeth). In the Triassic, real dinosaurs first appeared, evolutionarily more advanced than their primitive ancestors. Their limbs were directed downwards, and not to the sides (as in crocodiles), which allowed them to move like mammals and keep their bodies above the ground. Dinosaurs moved on their hind legs, maintaining balance with the help of a long tail (like a kangaroo), and differed in small growth - from 30 cm to 2.5 m. Some reptiles adapted to life in the marine environment, for example, ichthyosaurs, whose body looked like a shark, and the limbs transformed into something between flippers and fins, and plesiosaurs, whose body became flattened, the neck was extended lass, 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 a multi-layered stratum of limestone, shale and sandstone. The Jurassic saw one of the largest marine transgressions in Western Europe. The huge epicontinental sea spread over most of England, France, Germany and penetrated into some western regions of European Russia. Numerous outcrops of Upper Jurassic lagoonal fine-grained limestones are known in Germany, in which unusual fossils have been found. In Bavaria, in the famous town of Solenhofen, the remains of winged reptiles and both of the known species of the first birds were found.

The Tethys Sea stretched 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 the epicontinental seas penetrated into Siberia from the north. Jurassic continental deposits 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 deposits. Most of Africa during the Jurassic was above sea level. The exception was its northern margin, which was flooded by the Tethys Sea. In South America, an elongated narrow sea filled a geosyncline located approximately at the site of the modern Andes.

In North America, the Jurassic seas occupied very limited territories in the west of the mainland. Thick strata of continental sandstones and overlying shales have accumulated in the area of ​​the Colorado Plateau, especially to the north and east of the Grand Canyon. Sandstones were formed from the sands that made up the desert dune landscapes of the basins. As a result of weathering processes, sandstones have acquired unusual shapes (for example, the picturesque pointed peaks in Zion National Park or the Rainbow Bridge National Monument, which is an arch towering 94 m above the canyon floor with a span of 85 m; these attractions are located in Utah). The shale deposits of the Morrison Formation are famous for the finds of 69 species of fossil dinosaurs. Finely dispersed sediments in this region probably accumulated in the conditions of a swampy lowland.

The flora of the Jurassic period was in general similar to that which existed in the Triassic. The flora was dominated by cycads and conifers. For the first time, Ginkgoaceae appeared - gymnosperms of broad-leaved woody plants with foliage falling in autumn (probably this is a link between gymnosperms and angiosperms). The only species of this family - ginkgo biloba - has survived to this day and is considered the most ancient representative of woody, truly living fossils.

The Jurassic fauna of invertebrates is very similar to the Triassic. However, reef-building corals became more numerous, and sea urchins and mollusks became widespread. Many bivalve mollusks related to modern oysters appeared. There were still numerous ammonites.

Vertebrates were predominantly reptiles, since the stegocephalians became extinct at the end of the Triassic. Dinosaurs have reached the climax of their development. Such herbivorous forms as apatosaurs and diplodocus began to move on four limbs; many had long necks and tails. These animals acquired gigantic dimensions (up to 27 m in length), and some weighed up to 40 tons. Individual representatives of smaller herbivorous dinosaurs, such as stegosaurs, developed a protective shell consisting of plates and spikes. Carnivorous dinosaurs, in particular allosaurs, developed large heads with powerful jaws and sharp teeth, they reached 11 m in length 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, in which membranous wings developed, like those of 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 impressions have been found 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 that formed the Sierra Nevada mountains in the western United States, which extended further north into present-day 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 orogeny in the Jurassic were insignificant.

Cretaceous period.

At this time, powerful layered strata of soft, weakly compacted white limestone, chalk, from which the name of the period originated, accumulated. For the first time, such layers were studied in outcrops along the banks of the Pas de Calais near Dover (Great Britain) and Calais (France). In other parts of the world, deposits of the corresponding age are also called Cretaceous, although other types of rocks are also found there.
During the Cretaceous, marine transgressions covered large parts of Europe and Asia. In central Europe, the seas flooded two sublatitudinal geosynclinal troughs. One of them was located within southeastern England, northern Germany, Poland, and western regions of Russia, and reached the submeridional Ural trough in the extreme east. Another geosyncline, Tethys, retained its former 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, connected with the Indian Ocean. With the exception of the northern and eastern margins, the territory of Asia during the entire Cretaceous period was not flooded by the sea, therefore continental deposits of this time are widespread there. Thick layers of Cretaceous limestones are present in many parts 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 with chalk epicontinental seas. In South America, during most of the Cretaceous period, the Andean trough was flooded by the sea. To the east of it, in a large area of ​​Brazil, terrigenous silts and sands with numerous remains of dinosaurs were deposited.

In North America, the marginal seas occupied the coastal plains of the Atlantic Ocean and the Gulf of Mexico, where sands, clays, and chalk limestones accumulated. Another marginal sea was located on the western coast of the mainland within California and reached the southern foothills of the revived Sierra Nevada mountains. However, the last largest marine transgression covered the western regions of the central part of North America. At this time, a vast geosynclinal trough of the Rocky Mountains was 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) up to the Arctic Ocean. During this transgression, a thick layered sequence of sandstones, limestones, and shales was deposited.

At the end of the Cretaceous, intensive orogeny took place in South and North America and East Asia. In South America, sedimentary rocks accumulated in the Andean geosyncline over several periods were compacted and crumpled into folds, resulting in the formation of the Andes. Similarly, in North America, the Rocky Mountains formed at the site of the geosyncline. Volcanic activity has intensified in many parts of the world. Lava flows covered the entire southern part of the Hindustan Peninsula (thus the vast Deccan Plateau was formed), and small outpourings of lava took place in Arabia and East Africa. All continents experienced significant uplifts, and all geosynclinal, epicontinental, and marginal seas regressed.

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 species, many of which are still growing today (for example, willow, oak, maple and elm). The Cretaceous fauna of invertebrates is generally similar to that of the Jurassic. Among vertebrates, the culmination of the species diversity of reptiles has come. 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 resembling 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 bone shield that protected the head and neck. A typical representative of this group is a Triceratops with a short nasal and two long supraocular horns.

Plesiosaurs and ichthyosaurs lived in the Cretaceous seas, and mosasaur sea lizards with an elongated body and relatively small flipper-like limbs appeared. Pterosaurs (flying lizards) lost their teeth and moved better in the air than their Jurassic ancestors. In one of the species of pterosaurs - Pteranodon - the wingspan reached 8 m.

Two species of birds of the Cretaceous period are known that have retained some morphological features of reptiles, for example, conical teeth placed in the alveoli. One of them - hesperornis (diving bird) - has adapted to life in the sea.

Although transitional forms more similar to reptiles than mammals have been known since the Triassic and Jurassic, for the first time numerous remains of true mammals were found in continental Upper Cretaceous deposits. The primitive mammals of the Cretaceous period were small and somewhat reminiscent of modern shrews.

The processes of mountain building and the tectonic uplift of the continents at the end of the Cretaceous period, which were widely developed on Earth, led to such significant changes in nature and climate that many plants and animals died out. The ammonites that dominated the Mesozoic seas disappeared from invertebrates, and all dinosaurs, ichthyosaurs, plesiosaurs, mosasaurs and pterosaurs disappeared from vertebrates.

cenozoic era,

covering the last 65 million years, is divided into the Tertiary (in Russia it is customary to distinguish two periods - the Paleogene and the Neogene) and the Quaternary periods. Although the latter was notable for its 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 man are associated with it.

Tertiary period.

At that time, many areas of Europe, Asia, and North Africa were covered with shallow epicontinental and deep-water 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 continued to exist, stretching from the Atlantic to the Indian Ocean. Its waters flooded the Iberian and Apennine peninsulas, the northern regions of Africa, southwestern Asia and the north of Hindustan. Thick limestone horizons were deposited in this basin. Most of northern Egypt is composed of nummulite limestone, which was used as a 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 into southeast Australia. Tertiary marine basins covered the northern and southern extremities of South America, and the epicontinental sea penetrated into the territory of 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 the denudation of the revived Rocky Mountains, accumulated on the Great Plains and in intermountain depressions.

Active orogeny took place in many regions of the globe in the middle of the Tertiary period. In Europe, the Alps, Carpathians and the Caucasus were formed. In North America, the final stages of the Tertiary formed the Coast Ranges (within the present-day states of California and Oregon) and the Cascade Mountains (within Oregon and Washington).

The Tertiary period was marked by significant progress in the development of the organic world. Modern plants originated in the Cretaceous period. Most Tertiary invertebrates were directly inherited from Cretaceous forms. Modern bony fishes have become more numerous, the abundance and species diversity of amphibians and reptiles have decreased. There was a leap in the development of mammals. From primitive shrew-like forms that first appeared in the Cretaceous period, many forms date back to the beginning of the Tertiary period. The oldest fossil remains of horses and elephants have been found in Lower Tertiary rocks. Carnivorous and artiodactyl animals appeared.

The species diversity of animals increased greatly, but many of them died out by the end of the Tertiary period, while others (like some Mesozoic reptiles) returned to the marine lifestyle, such as cetaceans and porpoises, in which the fins are transformed limbs. Bats were able to fly thanks to the membrane that connects their long fingers. Dinosaurs, which became extinct at the end of the Mesozoic, gave way to mammals, which became the dominant animal class on land at the beginning of the Tertiary period.

Quaternary period

subdivided into Eopleistocene, Pleistocene and Holocene. The latter began only 10,000 years ago. The modern relief and landscapes of the Earth basically took shape in the Quaternary period.

Mountain building, which took place at the end of the Tertiary period, predetermined the significant uplift of the continents and the regression of the seas. The Quaternary period was marked by a significant cooling of the climate and the widespread development of ice sheets 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, ice cover was smaller, mainly limited to foothill areas. In North America, the ice sheets covered a vast area, including most of Canada and the northern parts of the United States as far as southern 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, four main stages of glaciation activation are distinguished, alternating with interglacials, during which natural conditions were close to modern or even warmer. The last ice sheet in Europe and North America reached its largest size 18–20 thousand years ago and finally melted at the beginning of the Holocene.

In the Quaternary period, many tertiary forms of animals died out and new ones appeared, adapted to colder conditions. Of particular note are the mammoth and the 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 already existed during the last interglacial, but a modern type of man - a reasonable man (Homo sapiens) - appeared only in the last ice age 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 the Ever-Changing Earth. M., 1984

HISTORICAL GEOLOGY, a science that studies the history and regularities of the geological development of the Earth from the moment of its formation. The global tasks of historical geology are the identification and systematization of the natural stages in the development of the earth's crust, the earth as a whole and the organic world of the geological past, the elucidation of the general patterns of the geological development of the earth and the processes that transform it. Among the particular tasks are: determining the age of rocks, reconstructing the physiographic (landscape-climatic) conditions of the earth's surface of the past, paleotectonic and paleogeodynamic conditions, studying the history of geological processes (volcanism, plutonism and metamorphism), tectonic movements and deformations, patterns of development of the structure of the earth's crust and the lithosphere as a whole. To solve these problems, data and methods of stratigraphy and geochronology, paleogeography, historical geotectonics and historical geodynamics are used. In addition, historical geology is also related to regional geology, paleontology, lithology, mineralogy, petrology, geochemistry, geophysics and other sciences and uses their methods. Among the main ones: methods for determining the relative and isotopic (absolute) geological age of rocks, the actualistic method in combination with facies analysis, methods for analyzing facies, thickness and volume of deposits, formational and lithodynamic complexes, breaks and unconformities; paleomagnetic, seismostratigraphic, etc.

As a complex science, covering all aspects of the geological history of the Earth, historical geology developed in the process of formation of stratigraphy, paleogeography, geotectonics and geology in general (see historical essays of the relevant articles). Modern historical geology, along with the solution of retrospective problems of restoring the geological past of the Earth, sets the task of predicting its future changes. The applied significance of historical geology is determined by the use of established patterns in the history of the formation of the earth's crust to create a theoretical basis for the rational search for mineral deposits contained in it.

The most important problems of historical geology are regularly discussed at the sessions of the International Geological Congress, in Russia - at the annual tectonic, stratigraphic and lithological meetings.

Lit .: Leonov G.P. Historical geology: Fundamentals and methods: Precambrian. M., 1980; Reed G., Watson J. History of the Earth. L., 1981. [T. 1-2]; Windley B. F. The evolving continents. 3rd ed. Chichester; N.Y., 1995; Koponovsky N. V., Khain V. E., Yasamanov N. A. Historical geology. 2nd ed. M., 2006.

HISTORICAL GEOLOGY (a. historic geology; n. historische Geologie; f. geologie historique; i. geology historica) is a science that studies the history and patterns of the geological development of the Earth.

The main areas of study of historical geology: the age of geological bodies, the physical and geographical conditions of the earth's surface in the geological past, tectonic movements and the history of the development of the structure of the earth's crust, the history of volcanism and deep magmatism, the history of the organic world, the relationship of geological processes.

Historical geology arose at the beginning of the 19th century on the basis of the use of the paleontological method (English scientist, French - J. Cuvier). In the first half of the 19th century, the formation of historical geology took place under the influence of the metaphysical theory of catastrophes (J. Cuvier, the French scientist A. d'Orbigny, and others). In the second half of the 19th century, the ideas of the evolutionary development of the Earth (the English scientists C. Lyell and C. Darwin) acquired great importance in historical geology, under the influence of which the main directions of research took shape.

The beginning of the development of historical geology in Russia dates back to the 2nd half of the 19th century and is associated with the names of S. N. Nikitin, N. I. Andrusov, A. A. Inostrantsev, and others. In the development of historical geology in the 1920s, it is associated with the names of A. D. Arkhangelsky, A. A. (I. Vernadsky A. P. Vinogradov). A new promising direction is formational, taking large categories of mineral masses (geological formations) and tectonic structures as a specific subject of study. Modern historical geology, together with other geological sciences, forms the basis of geology proper (general geology), investigating the temporal patterns of the earth's historical development. The applied value of historical geology is determined by the use of its data for understanding the conditions of the genesis of minerals and the patterns of their distribution, which creates a scientific basis for the search and exploration of the latter (see.

Questions of historical geology are being developed at the All-Union Research Geological Institute named after V.I. A.P. Karpinsky in Leningrad, at the Faculty of Geology of Moscow State University (Department of Historical and Regional Geology).

Historical geology - the science of the laws of development of the earth's crust - operates with a number of historical and geological methods. The most important task of historical geology is to establish the relative and absolute age of deposits. The method of actualism serves as the basis for the reconstruction of the physical-geographical and tectonic settings of the geological past.

In the history of the development of the Earth and the Earth's crust, several major stages are distinguished, which are not equal in their significance: 1 - the stage of accretion of the substance of the gas and dust nebula; 2 - pregeological stage; 3 - Precambrian (4.0-3.5 - 1 billion years ago); in the Phanerozoic, the following are distinguished: 4 - Early Paleozoic (Caledonian); 5 - Late Paleozoic (Hercynian); 6 - Mesozoic (Cimmerian) and 7 - Mesozoic-Cenozoic (Alpine) stages, which began and ended in different regions of the Earth at the same time. The beginning of the stages was characterized by the opening of basins with oceanic-type crust, and the end by the convergence of lithospheric plates and the formation of mountain-fold belts.

Chapter 18

Historical geology is part of geology - the science of the Earth, but geology itself does not cover all the problems related to our planet, and some of them are also considered by geography, meteorology, oceanology, geodesy, hydrogeology, soil science and other sciences. A geologist deals with natural documents - rocks, remains of fauna and flora, which, having formed hundreds of millions of years ago, retain their features, which make it possible to restore the conditions for the accumulation of matter in ancient times. An important circumstance is the sequence of formation of rock strata with organic remains contained in them, which makes it possible for us to trace the evolution of the organic world and sedimentation from ancient times to the present day.

In the process of formation, rocks were subjected to powerful deformations; various intrusive bodies were introduced into them: plunging to great depths and warming up, the rocks experienced metamorphism; finally, as it turned out in recent decades, the continents, the lithospheric plates did not remain in one place, but moved over long distances, both in latitude and longitude, and, moreover, rotated; oceanic expanses then expanded, then narrowed, the continents closed. Historical geology just clarifies the patterns of development of the earth's crust, the knowledge of which allows you to correctly predict the search for mineral deposits. Historical geology deals with various aspects of geology and operates with a number of historical and geological methods, while at the same time remaining closely related to other geological sciences: paleontology, geotectonics, petrography, sedimentology, regional geology, etc.

When analyzing rocks, and most often rock strata, special attention is paid to the relationship of layers and their packs within strata, because the nature of the occurrence of young layers on older ones can tell a lot about tectonic movements, their type, sign and other factors. Elucidation of the role of tectonic movements in the history of the geological development of any region is extremely large. Various sedimentary rocks are formed in different physical and geographical settings: on land, in the sea, in the oceans, in the coastal or, conversely, deep-sea zone, in hot or cold climates, under conditions of ice sheets, during powerful volcanic eruptions, etc. All such environments are characterized only by their inherent vegetation and fauna. From the point of view of restoring paleogeographical conditions, this and many other data are of great value.

Historical geology is designed to reveal the conditions of sedimentation in the past, to reconstruct the paleoclimate, to decipher tectonic movements and to establish what the land relief was like at that time, to show the evolution of sea and lake reservoirs and river systems. Against this background, another important task of historical geology appears: the establishment of patterns of development of the organic world, which depends on the composition of the atmosphere and the nature of the hydrosphere, as well as on the relationship between representatives of various groups of fauna and flora. Consequently, historical geology deals with a wide range of questions, and its immediate task is to generalize various geological materials.

Historical geology as a scientific direction arose at the end of the 18th century, when the English scientist William Smith developed a paleontological method with which it became possible to identify the sequence of geological events in time. The paleontological method spread very quickly, and the first geological sections became the result - stratigraphic columns, geological systems were distinguished, etc. Historical geology, being at first descriptive, subsequently increasingly assumed the functions of establishing the general patterns of the geological development of regions. In the 30s of the XIX century. the outstanding work of the English scientist C. Lyell "Fundamentals of Geology" appeared, in which the geological processes of the past were considered from an actualistic position and, in contrast to the French scientist J. Cuvier, changes on Earth were explained not by catastrophic events, but by slow, very long processes of evolution, in particular the organic world.

At the end of the XIX century. the accumulated material reached such a level that it became possible to make major generalizations, which was done by Neimair for the Jurassic period and by the Austrian geologist E. Suess for the entire globe in his famous work The Face of the Earth. Another outstanding geologist A.P. Karpinsky at the end of the 19th century. generalized the available data on the geology of European Russia and revealed the nature of oscillatory tectonic movements. For the first time, paleogeographic maps were presented in his work.

At the beginning of the XX century. generalizing works on the history of the development of geosynclinal belts appear, belonging to the French geologist E. Og, German scientists G. Stille, S. Bubnov, Soviet geologists A.D. Arkhangelsky, N.S. Shatsky, D.V. Nalivkin, N.M. Strakhov, P.I. Stepanov, I.M. Gubkin and many others. Historical geology is the basis of all major summary works on regional geology and today it is essential for setting up exploration and survey work, since a reliably deciphered history of the geological development of the area is the basis for all subsequent research.