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- 1. Geological Time Scale Geological Time Scale R.V.Gireesh
- 2. Geologic time scale A systematic and chronological organization of ti l t d t th hi t f th E th d time related to the history of the Earth and universe used by scientists (geologists, paleontologists, astronomers) to describe the timing and relationships between events that g p have occurred during the history of the Earth
- 3. KEY CONCEPT The geologic time scale divides Earth’s g g history based on major past events.
- 4. What is the Earth’s time scale? What is the Earth’s time scale? The The Geological time scale Geological time scale is a record of the is a record of the life forms and geological events in Earth’s life forms and geological events in Earth’s g g g g history. history. Scientists developed the time scale by studying Scientists developed the time scale by studying Scientists developed the time scale by studying Scientists developed the time scale by studying rock layers and fossils rock layers and fossils world wide. world wide. Radioactive dating Radioactive dating helped determine the helped determine the absolute divisions in the time scale. absolute divisions in the time scale. absolute divisions in the time scale. absolute divisions in the time scale.
- 5. Geologic time scale Time Time- -line of Earth’s history line of Earth’s history Breaks down Earth’s history into units of time Breaks down Earth’s history into units of time y y
- 6. The Earth solidified and became a planet about 4.6 billion years ago billion years ago. Geologist have subdivided this 4.6 billion years into Eons, Eras, and Periods. These divisions are based upon major trends in the These divisions are based upon major trends in the evolution of life on earth according to fossil records. In particular, the boundaries between the geologic eras represent times where mass extinctions have occurred.
- 7. Geologic Time d d d h l i d l i h i fi In order to understand how geologists deal with time we first need to understand the concepts of relative age and absolute age. Relative age : Relative means that we can determine if hi i h ld h hi l something is younger than or older than something else. Relative time does not tell how old something is, all we know is th f t the sequence of events. For example: Granite in this area is older than the Basalt. Absolute age: Absolute age means that we can more or less precisely assign a number (in years minutes seconds or some precisely assign a number (in years, minutes, seconds, or some other units of time) to the amount of time that has passed. Thus we can say how old something is. y g For example: The sandstone is 2300 million years old.
- 8. Eras Eras are the are the largest unit largest unit of time of time. . g g Paleozoic Paleozoic Mesozoic Mesozoic Mesozoic Mesozoic Cenozoic Cenozoic Eras Eras are divided into smaller parts called are divided into smaller parts called periods periods. . Eras Eras are divided into smaller parts called are divided into smaller parts called periods periods. . P i d P i d h di id d i ll h di id d i ll Periods Periods are then divided into even smaller parts are then divided into even smaller parts called called epochs epochs. . Epochs Epochs are then divided into even smaller parts are then divided into even smaller parts Epochs Epochs are then divided into even smaller parts are then divided into even smaller parts called called Age. Age.
- 9. Lithostratigraphy Lithostratigraphy Biostratigraphy Biostratigraphy Supergroup Supergroup Lithostratigraphy Lithostratigraphy Biostratigraphy Biostratigraphy Biozone Biozone A bl Z A bl Z Group Group Formation Formation Assemblage Zone Assemblage Zone Range Range- -Zone Zone Formation Formation Member Member B d B d Acme Acme- -Zone Zone Interval Interval- -Zone Zone Bed Bed Interval Interval Zone Zone
- 10. Chronostratigraphy Chronostratigraphy Geochronology Geochronology Chronostratigraphy Chronostratigraphy (Time (Time- -rock) rock) Geochronology Geochronology (Absolute time) (Absolute time) Eonothem Eonothem Erathem Erathem Eon Eon Era Era Erathem Erathem System System S i S i Period Period Epoch Epoch Series Series Stage Stage Epoch Epoch Age Age Chronozone Chronozone Chron Chron
- 12. Eon Era Period Quaternary Cenozoic Neogene Paleogene Cretaceous Phanerozoic Mesozoic Cretaceous Jurassic Triassic (542 my – recent) Permian Period Carboniferous Period: Palaeozoic Devonian Period Silurian Period Ordovician Period Cambrian Period Precambrian Proterozoic (2500 – 542 my) Neoproterozoic, Mesoproterozoic, Paleoproterozoic Archean Neoarchean Mesoarchean Precambrian Archean (4000 – 2500my) Neoarchean, Mesoarchean, Paleoarchean, Eoarchean Hadean (~4600 – 4000 my)
- 13. Precambrian Precambrian Precambrian Precambrian Earliest span of time in Earth’s history. Earliest span of time in Earth’s history. No life for a long time and then No life for a long time and then very very simple simple life appears. life appears. E l lif i fl d b l d E l lif i fl d b l d Early life influenced by volcanoes and Early life influenced by volcanoes and mountain building mountain building
- 14. Paleozoic Era Paleozoic Era Paleozoic Era Paleozoic Era Took place after Precambrian. Took place after Precambrian. E l i b d hibi E l i b d hibi Early invertebrates and amphibians, Early invertebrates and amphibians, “Age of Fishes” “Age of Fishes” Age of Fishes . Age of Fishes . Tropical climates allowed growth of new species Tropical climates allowed growth of new species Tropical climates allowed growth of new species Tropical climates allowed growth of new species Mass extinction at end most marine invertebrates Mass extinction at end most marine invertebrates disappeared. disappeared.
- 15. Mesozoic Era Mesozoic Era Mesozoic Era Mesozoic Era Took place after Paleozoic Era. Took place after Paleozoic Era. Reptiles, small mammals, and small birds. Reptiles, small mammals, and small birds. “A f R til ” “A f R til ” di t di t “Age of Reptiles” “Age of Reptiles” - -dinosaurs, etc dinosaurs, etc Late mass extinction by asteroid or climate Late mass extinction by asteroid or climate Late mass extinction by asteroid or climate Late mass extinction by asteroid or climate change that caused dinosaurs to go extinct. change that caused dinosaurs to go extinct.
- 19. Cenozoic Era Cenozoic Era Cenozoic Era Cenozoic Era The Era we are currently in!!! The Era we are currently in!!! Mammals, flowering plants, humans. Mammals, flowering plants, humans. “Age of Mammals” “Age of Mammals” W ill h h di i b ld h b W ill h h di i b ld h b We still have much diversity but could there be a We still have much diversity but could there be a mass extinction to come??? mass extinction to come???
- 21. GEOLOGIC TIME SCALE MYA ERA PERIOD EPOCH LIFE 0 01 Holocene -Mastadons become extinct Human culture flourishes 0.01 Quaternary Holocene -Human culture flourishes -Accelerating extinction of many species 1.8 Pleistocene -Modern humans develop Cenozoic “Age of Mammals” 5.3 Pliocene Hominids develop 23.8 Miocene Horses, mastadons, mammoths, tigers, and camels Tertiary 33.7 Oligocene Cats, dogs, and apes appear 54.8 Eocene -Grass spreads widely -Diverse array of animals develop, including whales, hi d l h t rhinos, and elephants 65.0 Paleocene -First horses appear (size of a cat) -Tropical plants dominate -T-Rex develops but number of dinosaur species 144 Mesozoic “Age of Reptiles” Cretaceous decline -Snakes appear and first primates appear -Angiosperms appear 206 Jurassic -First birds appear Reptiles 206 Jurassic -Golden age of dinosaurs 248 Triassic First dinosaurs, mammals, crinoids, and modern echinoids appear 290 Permian -90% of Earth’s species become extinct, including trilobites, blastoids, fish and amphibians because of heavy volcanism.
- 22. 320 Carbo Pennsylvania n -Reptiles develop from amphibians -Flying insects appear oniferous 354 Mississippia n -First seed plants appear -Sea life flourishes including coral, brachiopods, blastoids, and bryozoa 417 Devonian -Dominant animals: fish -Amphibians, evergreens and ferns appear 443 Sil i Fi t l d l t d l d i l f ll Paleozoic “Age of Invertebrates” 443 Silurian First land plants appear and land animals follow 490 Ordovician -First animals with bones appear -Dominant animals: marine invertebrates including corals and trilobites and trilobites -Explosion of life -All existing phyla came into being here 540 Cambrian g p y g -Life forms in warm seas as oxygen levels rose enough to support life -Dominant animals: trilobites and brachiopods 4600 Precambrian (Hadean Archean and Proterozoic Ages) No life possible as the Earth initially forms 4.6 billion years ago. Simple, single-celled forms of life appear 3.8 billion years ago. They will become more complex and successful over (Hadean, Archean, and Proterozoic Ages) g y p the next 3 billion years: Prokaryotes then Eukaryotes Cyanobacteria begins producing free oxygen (photosynthesis)
- 24. “Humans” Most recent “Ice Age” Major Mass Humans arrive Age of Major Mass Extinction Major Mass Extinction g Dinosaurs Age of Coal Formation Extinction Age of Fishes Th G l i Ti S l Th G l i Ti S l First multi- celled The Geologic Time Scale The Geologic Time Scale Origin of the Earth 4.55 Billion years celled organisms
- 25. Capitalisation Geological and Cultural Time >Names of geological eons, eras, periods, and cultural periods are capitalized (but not the words, eon, era, and period). Phanerozoic eon Mesozoic era = Mesozoic Era x Jurassic period The Neolithic period The Neolithic period The Stone age g Similarly, pre- Jurassic or post- Jurassic, but Precambrian
- 26. Eons: Precambrian: Earliest span of time Phanerozoic: Everything since y g Eras: Paleozoic Periods: C b Paleozoic Mesozoic Cenozoic Cambrian Ordovician Silurian D i Paleozoic Devonian Carboniferous (Missipp. & Pennsylvanian) P i Epochs: Paleozoic “Age of Invertebrates” Permian Triassic Jurassic Cretaceous poc s: Paleocene Eocene Oligocene Mesozoic “Age of Reptiles” Cretaceous Paleogene Neogene Quaternary g Miocene Pliocene g p Cenozoic “Age of Quaternary Pleistocene Holocene W li i i th Ph i E C i E Q t g Mammals” We are living in the Phanerozoic Eon, Cenozoic Era, Quaternary Period, Holocene Epoch……..BUT
- 27. The Earth Through Time Standard 8-2.5: Illustrate the vast diversity of life that has been present on Earth over time by using the geologic time scale. Standard 8 2.5: Illustrate the vast diversity of life that has been present on Earth over time by using the geologic time scale. No life possible as the Earth initially forms 4.6 The Proterozoic: billion years ago. Simple, single-celled forms of life appear 3.8 billion years ago, becoming more complex and successful over the next 3 billion years: Prokaryotes then Eukaryotes Cyanobacteria begins producing free oxygen (photosynthesis) Land masses gather to make up a continent called “Rodinia” Cambrian: Explosion of life Explosion of life All existing phyla come into being at this time Life forms in warm seas as oxygen levels rise enough to support life Dominant animals: Marine invertebrates Dominant animals: Marine invertebrates (trilobites and brachiopods) Supercontinent Gondwana forms near the South Pole (note position of present-day Florida) PaleoMaps used with permission from Christopher Scotese and are under copyright of C.R. Scotese, 2002 27 19 Table of Contents
- 28. Ordovician: The 1st animals with bones appear, though dominant animals are still trilobites brachiopods dominant animals are still trilobites, brachiopods and corals The beginning of the construction of South Carolina A very cold time in Earth’s history: there was a great extinction due to ice caps in present-day Africa G d l Four main continents: Gondwana, Baltica, Siberia and Laurentia Silurian: First land plants appear and land animals follow Laurentia collides with Baltica and closes Iapetus Sea. Coral reefs expand and land plants begin to Coral reefs expand and land plants begin to colonize barren land. First millipede fossils and sea scorpions (Euryptides) found in this period PaleoMaps used with permission from Christopher Scotese and are under copyright of C.R. Scotese, 2002 28 20 Table of Contents
- 29. Devonian (Age of the Fish) Pre-Pangea forms. Dominant animal: fish Oceans still freshwater and fish migrate from southern hemisphere to North America North America. Present-day Arctic Canada was at the equator and hardwoods began to grow. Amphibians, evergreens and ferns appear Mississippian: appear The Acadian Orogeny, leading to S.C. metamorphism PaleoMaps used with permission from Christopher Scotese and are under i h f C S Mississippian: First seed plants appear Much of North America is covered by shallow seas and sea life flourishes (bryoza brachipods copyright of C.R. Scotese, 2002 life flourishes (bryoza, brachipods, blastoids) Pennsylvanian: Pennsylvanian: Modern North America begins to form Ice covers the southern h i h d l hemisphere and coal swamps formed along equator. Lizards and winged insects first appear. 29 21 Table of Contents
- 30. Permian: Last period of the Paleozoic p Pangea forms. Reptiles spread across continents. The Appalachians rise pp 90% of Earth’s species become extinct due to volcanism in Siberia. This marks the end of trilobites, ammonoids blastoids and most ammonoids, blastoids, and most fish. Triassic: First dinosaurs appear First mammals small rodents appear First mammals- small rodents appear Life and fauna re-diversify Rocky Mountains form. First turtle fossil from this period Pangea breaks apart PaleoMaps used with permission from Christopher Scotese and are under copyright of C.R. Scotese, 2002 22 Table of Contents
- 31. Jurassic: Pangea still breaking apart Pangea still breaking apart Dinosaurs flourish “Golden age of dinosaurs” First birds appear First birds appear North America continues to rotate away from Africa Cretaceous: T-Rex develops First snakes and primates appear Deciduous trees and grasses common fl l First flowering plants Mass extinction marks the end of the Mesozoic Era, with the demise of dinoaurs and 25% of all marine of dinoaurs and 25% of all marine life. PaleoMaps used with permission from Christopher Scotese and are under copyright of C.R. Scotese, 2002 31 Table of Contents
- 32. Tertiary: First horses appear and tropical First horses appear and tropical plants dominate (Paleocene) Grasses spread and whales, rhinos, elephants and other large mammals develop. Sea level rises and limestone deposits form in S.C. (Eocene) Dogs cats and apes appear Dogs, cats, and apes appear (Oligocene) Horses, mastadons, camels, and tigers roam free in S.C. (Miocene) Hominids develop and the Grand Canyon forms (Pliocene) Quaternary: Modern humans develop and ice sheets are predominant- Ice age sheets are predominant Ice age (Pleistocene) Holocene Humans flourish (Holocene) PaleoMaps used with permission from Christopher Scotese and are under copyright of C.R. Scotese, 2002 32 Table of Contents
- 33. Eons Eons These are the longest periods of time within the These are the longest periods of time within the history of the Earth, which are now commonly di id d i h h h divided into three eons: the Archaean Eon up to 2.5 Ga, the Proterozoic Eon from 2.5 Ga to 542 Ma (together these constitute the Precambrian), and the Phanerozoic Eon from 542Ma up to the and the Phanerozoic Eon from 542Ma up to the present.
- 34. Eras Eras are the three time divisions of the Phanerozoic: the Palaeozoic Era up to 251 Ma the Phanerozoic: the Palaeozoic Era up to 251 Ma, the Mesozoic Era from then until 65.5Ma and finally the Cenozoic Era up to the present the Cenozoic Era up to the present. Precambrian eras have also been defined, for example dividing the Proterozoic into the p g Palaeoproterozoic, the Mesoproterozoic and the Neoproterozoic. Neoproterozoic.
- 35. P i d /S t Periods/Systems The basic unit of geological time is the period and these are the most commonly used terms when y referring to Earth history. The Mesozoic Era, for example is divided into three periods the Triassic example, is divided into three periods, the Triassic Period, the Jurassic Period and the Cretaceous P i d Th t t i d f th k Period. The term system is used for the rocks deposited in this time, e.g. the Jurassic System.
- 36. Epochs/Series Epochs/Series are the major divisions of periods: some have names For example : Early Cretaceous and Late Cretaceous). y )
- 37. Ages/Stages The smallest commonly used divisions of geological time are ages, and the h i hi i l i h Th i ll f illi i chronostratigraphic equivalent is the stage. They are typically a few million years in duration. For example, the Oligocene Epoch is divided into the Rupelian and Chattian Ages (the Rupelian and Chattian Stages of the Oligocene Series of rocks). Chrons are short periods of time that are sometimes determined from palaeomagnetic information but these periods of time that are sometimes determined from palaeomagnetic information, but these units do not have widespread usage outside of magnetostratigraphy (21.4). The Quaternary can be divided into short time units of only thousands to tens of thousands of years using a range of techniques available for dating the recent past such as marine isotope stages a range of techniques available for dating the recent past, such as marine isotope stages (21.5).
- 38. Extra slides Extra slides Extra slides Extra slides
- 40. Geologic Time Highlights of Biological Evolution About 4.5 billion years ago Formation of Earth within the Solar System About 4 billion years ago Evidence of earliest cell based life of Earth (prokaryotes)...? years ago (prokaryotes)...? About 3 billion Evidence of photosynthesis and first eukaryotic cells bl f b d i i years ago capable of oxygen based respiration
- 41. Geologic Time Highlights of Biological Evolution Worldwide deposition of banded iron formations About 3.0 to 1.8 billion years ago Worldwide deposition of banded iron formations fundamental to the gradual conversion of Earth atmosphere from CO2 to free oxygen, allowing development of an billion years ago ozone layer to protect earth from deadly solar ultraviolet radiation About 1.8 billion years ago Sexual reproduction fully established in eukaryotes About 1 billion li id f l i ll l i ( ) About 1 billion years ago Earliest evidence of multi-cellular organisms (metazoans).
- 42. Geologic Time Highlights of Biological Evolution CAMBRIAN Beginning of the Cambrian Period and "radiation of species" in part, because many organisms began to develop h d k l l i l f d f i d f i l Beginning about 570 million years ago hard skeletal material as part of defensive and functional body plans. Hard body parts are (shells and exoskeletons) were selectively preserved (and therefore easier to find as ago were selectively preserved (and therefore easier to find as fossils) in Cambrian and younger sedimentary rocks.
- 43. Geologic Time Highlights of Biological Evolution Cambrian Period (542-488my) *By the end of the Cambrian Period several groups of invertebrates were well established in shallow marine environments, perhaps most notably were trilobites, brachiopods, crinoids, bryozoans, sponges, and gastropods are locally common (542 488my) fossils preserved in Cambrian sedimentary rocks. Ordovician Trilobites no longer dominated the fossil record, but other life forms began to dominate the shallow marine environment. Corals (unrelated to modern varieties), crinoids, cephalopods, Period (488-443my) ( ) p p brachiopods, bryozoans and other fossils with calcareous skeletons dominate the fossil record (because of their ability to survived burial and fossilization processes). Rare early examples of fish and land plants have been discovered in Ordovician age sedimentary rocks. Silurian Period Few rocks of Silurian age are preserved in North America's fossil record (New York and Michigan are notable exceptions). The fossil record shows that the Silurian world was dominated by marine i t b t b t th fi t fi hlik (443-416my) invertebrates, but the first fishlike chordates appear. Land plants began to flourish, allowing the first animals to emerge onto dry land (including insects and scorpions). O l d f i l l d d d d h l d ll i h Devonian Period On land, frees poring vascular plants adapted and spread across the landscape, allowing the first forests to cover the continents. By the middle of the Devonian several groups of plants had evolved leaves and true roots, and by the end of the period the first seed bearing plants appeared. Terrestrial arthropods began to flourish. In the marine world, early rayfinned, Period (416-359my) appeared. Terrestrial arthropods began to flourish. In the marine world, early rayfinned, Lobefinned bony fish, and sharks appear in the fossil record. The first ammonoid mollusks appeared. Holdover families of marine invertebrates from earlier times persisted, including trilobites, brachiopods, cephalopods, and reefforming corals remained common.
- 44. Geologic Time Highlights of Biological Evolution Carbo (3 In this period great quantities of coal are preserved in rocks of these time. Amphibians became the dominant land vertebrates. Descendent from oniferous 359-299m Amphibians became the dominant land vertebrates. Descendent from amphibian ancestors, reptiles evolved and became the first terrestrial vertebrates. With the abundance of vegetation on land, arthropods flourish, including species of insects that are much larger than any found on Earth s Period my) including species of insects that are much larger than any found on Earth today. Toward the end of the Carboniferous, glaciation cycles caused repetitious rise and fall in sea levels The last period of the Paleozoic Era was a time of colossal changes. All the continents of the world combined to form the supercontinent of Pangaea. In Permia (299-2 p g the fossil record, a group of tetrapods (four legged animals with backbones) called amniotes appeared that have a terrestrially adapted eggs. All modern land species are descendant from a common ancestral group of an Period 251my) All modern land species are descendant from a common ancestral group of amniotes. During the Permian, the expansive forests that existed during the Carboniferous disappeared, and vast desert regions covered the continental interior Reptiles adapted and flourished in the more arid environment The interior. Reptiles adapted and flourished in the more arid environment. The end of the Permian Period (and Paleozoic Era) is marked by the greatest mass extinction in Earth history.
- 45. Cambrian Period
- 46. co o y e e ed o s e ge o ep es. Following the great extinction event at the end of the Permian Period, life on Earth gradually reestablished itself both on land and in the oceans T i i Earth gradually reestablished itself both on land and in the oceans. On land, reptilian therapsids and archosaurs became the dominant vertebrates. N l d i h iddl l T i i P i d i l di h fi Triassic Period (251- New groups evolved in the middle to late Triassic Period including the first dinosaurs, mammals, and flying vertebrates (pterosaurs) but these families did not flourish until another global extinction event at the close of Triassic ti (251 199my) time. During the middle Triassic, the supercontinent of Pangaea began to rift apart into separate landmasses, Laurasia to the north and Gondwana to the south. With the breakup of Pangaea, terrestrial climates gradually change from mostly hot and dry to more humid condition. Another mass extinction in the fossil record marks the end of the Triassic Period. The cause of the mass extinction at the end of Triassic is still unclear, but evidence shows that it was rapid and massive amounts of volcanism was taking place with the ongoing breakup of Pangaea. Jurassic Period (199 145 ) g p g g p g With other life forms out of the way, dinosaurs adapted and diversified into a wide variety of groups. Although pterosaurs were the dominant flying vertebrates during the Jurassic (199-145my) Periods, the first birds appeared having evolved from a branch of theropod dinosaurs. Small mammals appear in the fossil record during the Jurassic, but remained
- 47. Mesozoic Era—the era between the Paleozoic and Cenozoic eras, comprising the Triassic, Jurassic, and Cretaceous periods; commonly f d h "A f R il " referred to as the "Age of Reptiles." During the Cretaceous Period the Earth was relatively warm compared to the g y p world today. There were no glaciers on the planet and sea level was as much as 200 feet higher that today. C higher that today. The dinosaurs that survived into the Cretaceous Period diversified and evolved into many unusual forms. L i til ll d M th d i t i i th Cretaceous Period (145- Large marine reptiles called Mosasaurs were the dominant organism in the ocean. Cretaceous gets its name for "Creta"—latin for the word chalk. The shallow ( 65my) warm seas of the Cretaceous Period were locations where the calcareous skeletal remains of planktonic organisms called coccoliths accumulated, forming great accumulations of chalk. In many places in the equatorial realm oyster like organism called rudists form great reefs. Flowering plants also first appear in the fossil record, birds and mammals g p pp , existed in Cretaceous time but were insignificant compared to flying nonavian pterosaurs
- 48. Review the Cretaceous Review the Cretaceous- -Tertiary boundary Tertiary boundary The Cretaceous – Tertiary boundary is one of the most investigated mass extinction event. It is has been well investigated partly because it is the youngest of the large extinctions that t t ll h d th t f lif th totally changed the nature of life on earth. The "K/T event" is believe to have been caused by a massive asteroid impact. What is known is that all species of dinosaurs on land, and marine reptiles and ammonites in the p , p marine realm vanished. The asteroid impact and following shock waves, monstrous tsunamis, firestorms, ash and gas clouds and following global winter like condition caused ecosystem collapse in both gas clouds, and following global winter like condition caused ecosystem collapse in both the food web of the oceans and on land. All species that exist today are descendent of the few species that survived the global catastrophe... small mammals, birds, invertebrates, reptiles, amphibians, fish and other surviving groups had evolutionary advantages that allowed them to survive. With the dinosaurs, pterosaurs, large swimming reptiles and other large animals of the Cretaceous Period out of the way, the surviving species proliferated and moved into empty and new niches that allowed them to prosper and diversify.
- 49. Cenozoic Era - Known as the "Age of Mammals" Quate Holocene End of the ice age to the present. Includes a 400 footrise in sea level and the rise of human civilizations ernary ( my) Pleistocene Time period of major ice ages where continental glacier advance and retreated, covering much of northern North America and Europe during cold periods. Modern human species appears in the fossil record. Many (2.5 – Pleistocene cold periods. Modern human species appears in the fossil record. Many species of large land mammals went extinct at the end of the Pleistocene Epoch. Ne Global climates cooled and became dryer with the onset of glaciation cycles. Most families of animals and plants found in the world had ancestral forms during the Pliocene including humans. Greenland's ice eogene (2 Pliocene sheet starts to form. South America and North America became linked at the Isthmus of Panama, allowing the cross migration of many species between continents; but also shutting off the migration of i f h A l i h P ifi Th ki d f 23-2.5 m species from the Atlantic to the Pacific oceans. The same kind of interactions took place when Africa collided with Europe. Animals and plants of the Miocene Epoch are approaching modern life my) Miocene forms in diversity. Earth was warmer with expanded tropical realms compared to the modern world. The Himalayan Mountains begin to rise as the Indian continental landmass began to collide with Asia.
- 50. Cenozoic Era - Known as the "Age of Mammals" The Oligocene was a time of transition when older life forms were replace with life forms that dominate the world today. The warmer, more tropical Oligocene w e o s do e e wo d od y. T e w e , o e op c environments of the Eocene Epoch gave way to dryer landscapes dominated by grasslands, whereas broadleaf forests became more restricted to the equatorial realm. Paleog q "Modern" forms of mammals appear and diversify in the fossil record gene (65 Eocene pp y during the Eocene Epoch. The Eocene was a warm period with an expanded tropical realm. The end of the Eocene period is marked by a mass extinction that may have involved asteroid collisions in Siberia and in -23 my) y the vicinity of Chesapeake Bay. Paleocene The mass extinction at the end of the Cretaceous Period left many of the niches filled by dinosaurs and large swimming empty. Mammals with placental type live birth appear. Shallow seas of the Cretaceous period p p pp p withdrew or were gradually replaced by lakes. In North America, the Rocky Mountains began to rise.
- 51. Stratigraphic terminology Stratigraphic terminology – – deals with the deals with the unit unit- -term used in stratigraphic term used in stratigraphic unit unit term used in stratigraphic term used in stratigraphic classification, such as formation, stage, classification, such as formation, stage, biozone. It can be either formal or biozone. It can be either formal or informal. informal. informal. informal. ► ► Formal: Formal: are defined and named according are defined and named according bli h d i ll d bli h d i ll d to an established or conventionally agreed to an established or conventionally agreed scheme of classification. e.g.. The scheme of classification. e.g.. The Vanivilas Vanivilas F Formation, the Cretaceous ormation, the Cretaceous S System. The initial letter of a named formal ystem. The initial letter of a named formal unit term is capitalized. unit term is capitalized. ► ► Informal: Informal: are only as ordinary nouns are only as ordinary nouns without the necessarily being named and without the necessarily being named and without it being a part of a specific scheme without it being a part of a specific scheme without it being a part of a specific scheme without it being a part of a specific scheme of stratigraphic classification. e.g. of stratigraphic classification. e.g. Ingaldhal Ingaldhal f formation, oyster ormation, oyster z zone. The one. The initial letter of an informal unit initial letter of an informal unit term is term is initial letter of an informal unit initial letter of an informal unit- -term is term is printed in lower case. printed in lower case.