Mesozoic Paleogeography Objectives • Explain the breakup of Pangaea. • Distinguish between the different tectonic characteristics of the Mesozoic Orogenies. Vocabulary – Cordillera Mesozoic Paleogeography Mesozoic Paleogeography • The Mesozoic Era consisted of the Triassic, Jurassic, and Cretaceous periods. Mesozoic Paleogeography The Breakup of Pangaea • The breakup of Pangaea was an important event that occurred during the Mesozoic Era. – Extreme heat from within Earth beneath Pangaea caused the continent to expand, cracking and breaking apart the lithosphere by the Late Triassic. – As the landmasses spread apart, the ocean flooded the rift valleys resulting in the formation of new oceans, including the Atlantic. – Some of the spreading areas joined together to form a continuous rift system called the Mid-Atlantic Ridge. Mesozoic Paleogeography Active Tectonism in Western North America • Active subduction along the western coast of North America continued through the Middle Triassic. The Cordillera, which means ―mountain range‖ in Spanish, refers to the mountain ranges that formed by subduction in western North America during the Mesozoic. Mesozoic Paleogeography Active Tectonism in Western North America • Three major episodes of orogenies—mountain- building—occurred along the western margin of North America during the Mesozoic. – The oldest orogeny was characterized by a large number of igneous intrusions and the resulting batholiths. – Beginning in the Late Jurassic and continuing through the Late Cretaceous, the next orogeny was characterized by low-angle thrust faulting and folding. – Beginning in the Late Cretaceous and continuing into the Cenozoic, the third Mesozoic orogenic event was characterized by vertical uplifts. Mesozoic Paleogeography Seaways and Sand Dunes • Throughout the Early and Middle Triassic, the supercontinent Pangaea and a single global ocean defined Earth’s paleogeography. • The Triassic ended with a rapid drop in sea level that caused western North America to become much more arid and sandy. • Strong winds shaped the sand into dunes that are preserved in large-scale, cross-bedded sandstone deposits. Mesozoic Paleogeography Seaways and Sand Dunes • Sea level rose again in the Jurassic, and a shallow sea covered central North America. – Deposits of the Late Jurassic river systems are preserved today as multicolored sandstones, siltstones, and mudstones. – The ocean continued to rise onto North America during the Cretaceous Period, flooding the entire southeastern margin of North America. – As a result, a sea covered the interior of North America from Texas to Alaska. Mesozoic Paleogeography Section Assessment 1. What caused rifts to form in Pangaea? Extreme heat from within Earth beneath Pangaea caused the continent to expand. Mesozoic Paleogeography Section Assessment 2. What is the Cordillera? The cordillera refers to the mountain ranges that formed in western North America during the Middle Triassic. Mesozoic Paleogeography Section Assessment 3. Identify whether the following statements are true or false. true ______ The Mid-Atlantic Ridge is still active today. false ______ The Cretaceous Period came before the Triassic Period. false ______ The Triassic ended with a dramatic rise in sea level. true ______ A sea covered the interior of North America during the Cretaceous Period. Mesozoic Life Objectives • Discuss why many paleontologists theorize that birds are descended from dinosaurs. • Describe how paleontologists distinguish among reptile, dinosaur, and mammal fossils. • Explain the evidence indicating that a meteorite impact caused the Cretaceous-Paleogene mass extinction event. Vocabulary – modern fauna – Saurischian – angiosperm – ectotherm – dinosaur – endotherm – Ornithischian – iridium Mesozoic Life Mesozoic Life • The Mesozoic is commonly referred to as the Age of Reptiles. • The first mammals, birds, and flowering plants appeared during the Mesozoic. Modern fauna refers collectively to the new marine organisms which arose during the Mesozoic. Mesozoic Life Life in the Oceans • The base of the food chain that supported all the large animals consisted of tiny, ocean-dwelling organisms called phytoplankton. • Phytoplankton float near the surface of oceans and lakes and make their own food through the process of photosynthesis. Mesozoic Life Life in the Oceans Reef Builders Arise Again – Modern corals had evolved by the end of the Triassic. – A new group of clams called rudists developed the ability to build reefs during the Cretaceous. – Rudists built very porous reefs that today contain some of the largest Cretaceous oil deposits in areas such as west Texas. Mesozoic Life Life in the Oceans Important Index Fossils – Ammonites are related to modern nautiluses, octopuses, and squids. – Ammonites were abundant and diverse throughout the Late Paleozoic and Mesozoic, and their abundance indicates that they were very successful predators. – Swimming reptiles such as ichthyosaurs, plesiosaurs, and mosasaurs ruled the Mesozoic oceans during the Cretaceous. Mesozoic Life Life on the Land • During the Mesozoic the large, temperate coal swamps dried up, and the climate gradually warmed, dramatically changing life on land. • Paleobotanists call the Mesozoic the Age of Cycads. • Cycads are seed plants that do not have true flowers. Mesozoic Life Life on the Land Angiosperms Evolve – Angiosperms, which are seed-bearing plants that have flowers, evolved during the Cretaceous. – Before the Cretaceous, there were no flowers. – By the end of the Cretaceous, the land was covered with flowering trees, shrubs, and vines. Mesozoic Life Life on the Land Early Mammals – Small, primitive mammals evolved during the Late Triassic. – The structure of the lower jaw, middle ear, and teeth can be used to identify fossils of mammals. – A reptile has one ear bone and multiple lower jawbones, whereas a mammal has one lower jawbone and three ear bones. – Mammals have differentiated teeth while reptiles generally have only one kind of tooth. Mesozoic Life Life on the Land Flying Reptiles – Pterosaurs were flying reptiles that dominated the air during the Mesozoic. – Pterosaurs had light, hollow bones, like modern birds. – The modification that allowed them to fly was the growth of a membrane from a greatly lengthened fourth finger. – Two groups of reptiles that arose during the Mesozoic and still exist are the crocodiles and turtles. Mesozoic Life Dinosaurs Rule the Land Dinosaurs were a group of reptiles that developed an upright posture about 228 million years ago. • Dinosaurs came in all sizes, from the very small to the extraordinarily large, and all were terrestrial. • Although the largest dinosaurs were most likely slow and plodding animals, many of them were quick and agile. Mesozoic Life Dinosaurs Rule the Land Mesozoic Life Dinosaurs Rule the Land Dinosaur Hips – Two major groups of dinosaurs are recognized based on their hip structure: Ornithischia and Saurischia. – In ornithischian, or ―bird hipped‖ dinosaurs, the ischium and pubis were parallel to one another, similar to modern birds. Mesozoic Life Dinosaurs Rule the Land Dinosaur Hips – In Saurischian, or ―lizard hipped‖ dinosaurs, the ischium and pubis were at an angle to one another, similar to the orientation observed in modern lizards. – Scientists hypothesize that birds are actually descended from the Saurischia. Mesozoic Life Dinosaurs Rule the Land Dinosaur Hips – There were five different groups of ornithischian dinosaurs: stegosaurs, ankylosaurs, pachycephalosaurs, ceratopsians, and ornithopods. • All ornithischian dinosaurs were plant eaters, also called herbivores. – There were two different groups of saurischian dinosaurs: sauropods and theropods. • The sauropods were all quadrupedal, herbivores, and some grew to enormous sizes. • All theropods were bipedal and carnivores. Mesozoic Life Dinosaurs Rule the Land Dinosaurs to Birds? – The idea that birds are related to dinosaurs stems from the amazing similarities between theropods and the oldest known bird, Archaeopteryx. – Fossils of feather impressions and a wishbone provide clear evidence that Archaeopteryx was definitely a bird, even though it did have teeth and a theropod-like skeleton. Mesozoic Life Dinosaurs Rule the Land Ectotherm or Endotherm? – All living reptiles are ectotherms, meaning that their body temperatures vary in response to external temperatures. – All living mammals and birds are endotherms, meaning that they maintain relatively constant body temperatures, regardless of external temperatures. – At least some groups of dinosaurs may have been endotherms. but this hypothesis is still controversial. Mesozoic Life Mass Extinctions • A major mass extinction event ended the Mesozoic. • Most major groups of organisms were devastated, and all known species of dinosaurs, pterosaurs, ammonites, mosasaurs, and plesiosaurs became extinct. • Geologists theorize that a large meteorite slammed into the Yucatan Peninsula. Mesozoic Life Mass Extinctions The circular shape and underlying layer of iridium-rich rock provides evidence of a meteorite impact. It was named the Chicxulub crater after a nearby village. Mesozoic Life Mass Extinctions Iridium is a metal that is rare in rocks at Earth’s surface but is relatively common in meteorites and asteroids. – Iridium is found in Cretaceous-Paleogene boundary sites worldwide, providing evidence of a major impact. – A buried crater in the Gulf of Mexico contains iridium, which has a radiometrically dated age of approximately 65 million years. – Volcanism can also release high levels of iridium. Mesozoic Life Mass Extinctions • Most scientists agree that both a large meteorite impact and massive volcanism occurred at the end of the Cretaceous. • The extraordinary stress that the impact added to an already stressed ecosystem likely caused the climax of the Cretaceous-Paleogene mass extinction. Mesozoic Life Section Assessment 1. Match the following terms with their definitions. ___ angiosperm D A. a metal that is relatively common in meteorites and asteroids ___ ectotherm C B. animals that have relatively ___ endotherm B constant body temperatures, ___ iridium A regardless of outside temperatures C. animals that have body temperatures that vary in response to outside temperatures D. seed-bearing plants that have flowers Mesozoic Life Section Assessment 2. What were the movement and diet characteristics of theropods? Theropods were bipedal carnivores. Mesozoic Life Section Assessment 3. Identify whether the following statements are true or false. true ______ It is hypothesized that birds descended from the Saurischia. false ______ All living reptiles are endotherms. true ______ Dinosaurs are the only reptiles to have developed an upright posture. true ______ Crocodiles and turtles arose during the Mesozoic. Cenozoic Paleogeography Objectives • Describe the type of tectonism that characterized the Cenozoic orogeny. • Understand the extent of glaciation that occurred in North America. Vocabulary – Basin and Range Province – Tethys Sea Cenozoic Paleogeography Cenozoic Paleogeography • The Cenozoic Era encompasses approximately the last 66 million years of Earth’s history to the present. Cenozoic Paleogeography Cenozoic Paleogeography The Ice Ages – The warm climate began to deteriorate during the Middle-to-Late Eocene, possibly due to a change in ocean circulation. – When Antarctica and Australia were connected, a current of warm water from the north moderated the temperature of Antarctica. Cenozoic Paleogeography Cenozoic Paleogeography The Ice Ages – When Antarctica was isolated over the south pole, a cold current began to flow around Antarctica, and glaciers began to form. – The climate began to warm again during the Early Miocene. – The glaciers on Antarctica began to melt, and the sea rose onto the margin of North America. – Glaciers returned to Antarctica during the Middle and Late Miocene, setting the stage for the ice ages of the Late Pliocene and the Pleistocene. Cenozoic Paleogeography Cenozoic Paleogeography The Ice Ages – During the Late Pliocene through the Pleistocene, the northern hemisphere experienced extensive glaciation, or an ice age. • Glaciers from the arctic advanced and retreated in at least four stages over North America. • The paths of the Ohio River and the Missouri River roughly mark the southernmost point to which glaciers advanced in North America. Cenozoic Paleogeography Tectonic Events • Western North America had been tectonically active throughout the Cenozoic. – The orogenic events that occurred at the end of the Mesozoic formed the Rocky Mountains. – The basins in Wyoming that filled with huge, swampy river deposits provided an ideal environment for the accumulation of vast amounts of coal. – The coal there is especially valuable because it has a very low sulfur content, and thus, it burns cleanly. Cenozoic Paleogeography Tectonic Events Subduction in the West – The Cascade Mountains are the result of the subduction of an oceanic plate beneath the western coast of North America at the end of the Eocene. – During the Miocene, the North American Plate was forced over the East Pacific Rise resulting in the creation of the San Andreas Fault. – The Basin and Range Province is a series of mountains that trend north-to-slightly-northeast, are separated by long, linear valleys, and extend from Nevada and western Utah to north-central Mexico. Cenozoic Paleogeography Tectonic Events Subduction in the West – Extensional tectonism pulled the crust apart, causing large blocks of the crust to drop down along normal faults to form the basins, leaving other blocks at higher elevations to form the mountain ranges. – This extension is still occurring today. Cenozoic Paleogeography Tectonic Events Hot Spots in the West – Hot spots are mantle plumes that rise to Earth’s surface. – Some of the hot spots that occur in the western United States are related to the continuing subduction along the western coast of North America. – The land that makes up Yellowstone National Park is situated on a hot spot that has been active since the Early Cenozoic. Cenozoic Paleogeography Tectonic Events Continental Collisions – While the final breakup of Pangaea occurred during the Cenozoic, plate tectonics also brought continents together during this time. • The Himalayan Mountains formed when India traveled north and collided with the southern margin of Asia. • Africa collided with the connected landmass of Europe and Asia, or Eurasia, forming the Alps. • The Tethys Sea was a narrow sea that separated the two continents before Africa collided with Eurasia. Cenozoic Paleogeography Tectonic Events The Tethys Sea had a strong, westward-flowing current that transported organisms across long distances. Cretaceous-aged fossils from the Tethys Sea are found as far west as the Hawaiian Islands. Cenozoic Paleogeography Section Assessment 1. What was the extent of the North American glaciers of the Late Pliocene through the Pleistocene? The Ohio and Missouri Rivers roughly form the southern boundary of the glaciation. Cenozoic Paleogeography Section Assessment 2. Why is the coal found in Wyoming especially valuable? The coal in Wyoming is especially valuable because it has a very low sulfur content, and thus, it burns cleanly. Cenozoic Paleogeography Section Assessment 3. Identify whether the following statements are true or false. true ______ Yellowstone National Park sits on top of a geologically active hot spot. false ______ The mountains in the Basin and Range Province were caused by uplift. false ______ The Himalayan Mountains were formed through a continental-oceanic collision. true ______ The Mediterranean Sea will likely become narrower over the next 50 million years. Cenozoic Life Objectives • Describe the landscape of the Oligocene in Central North America. • Discuss the changes in animals in North America during the Cenozoic. • Identify the characteristics of primates. • Explain what separates hominids from the other hominoids. Vocabulary – primate – hominid – hominoid – Homo sapiens Cenozoic Life Cenozoic Life • The modern marine fauna, including clams, snails, sea urchins, crustaceans, bony fishes, and sharks, survived the Cretaceous mass extinction to populate the modern oceans. • Whales and dolphins evolved during the Cenozoic as completely aquatic mammals. • Walruses and sea lions returned to the oceans but remain partly terrestrial today. Cenozoic Life Life on Land • Most of the currently living groups of mammals had evolved by the Eocene. • Forests dominated North America during the Paleocene and Eocene, giving way to open land as the climate cooled during the Late Eocene. • Grasses, which were important to many large mammals, appeared during the Eocene. • The resulting savannas supported a large diversity of mammals, most of which are members of groups living today. Cenozoic Life Life on Land Pleistocene Mammals – As the Pliocene ice age began, the great savannas were replaced by more arid land. – The change in climate caused many of the savanna mammals to become extinct. – A new group of animals, such as the woolly mammoth, dire wolf, and sabre-toothed cat, evolved and populated the land. Cenozoic Life Primates and Humans • The scarcity of fossils is a difficult problem to overcome in studies of the origin of humans and our relationship to other primates. • The discovery of a single new fossil can dramatically change our understanding. Cenozoic Life Primates and Humans Primates – Primates are distinguished from other mammals by a grasping hand with an opposable thumb and two eyes directed forward that result in stereoscopic vision. – Other primate characteristics include smaller, fewer, and less-specialized teeth than other mammals and a relatively large brain. Cenozoic Life Primates and Humans Primates – Hominoids are a primate group that includes hominids and the great apes. – Hominids, the group of hominoids that includes Homo sapiens, are differentiated from other hominoids by being bipedal with an upright posture, having larger brains, smaller canine teeth, and smaller faces than other hominoids, and through the use of sophisticated tools due to greater manual dexterity. Cenozoic Life Primates and Humans The Rise of Homo Sapiens – Homo sapiens is the species to which humans belong. – In the 1850s, a fossilized Neanderthal skull was discovered in Neander Tal near Dusseldorf, Germany. – Most fossil evidence indicates that Neanderthals were most likely a side branch of H. sapiens and not direct ancestors of modern humans. – The Neanderthals were hunters that inhabited Europe and the Near East approximately 200 000 to 30 000 years ago. Cenozoic Life Primates and Humans The Rise of Homo Sapiens – Neanderthals had heavier brows, mouths that projected forward, receding chins, more massive, muscular bodies, and slightly larger brains than modern humans do. – A characteristic of Neanderthals (top) is a gap that occurs between the rear teeth and the jaw bone. Modern humans (bottom) do not possess this gap. Cenozoic Life Primates and Humans The Rise of Homo Sapiens – There is evidence that Neanderthals buried their dead and placed items such as tools in their graves. – The fossil skeleton of Australopithecus afarensis provides evidence that bipedal, upright-walking hominids existed at least 3.5 million years ago. – Compared to the rest of the fossil record, there are relatively few hominid fossils. Cenozoic Life Section Assessment 1. Match the following terms with their definitions. ___ primate C A. a group of bipedal primates ___ hominoids D with upright posture that use sophisticated tools ___ hominids A B. the process of collecting ___ Homo sapiens B data about Earth from far above Earth’s surface C. the species to which humans belong D. a primate group that includes the great apes Cenozoic Life Section Assessment 2. What type of land animals dominated the Eocene? What allowed them to evolve? Large mammals evolved and dominated the Eocene as grasslands, or savannas, became common. Cenozoic Life Section Assessment 3. Identify whether the following statements are true or false. false ______ Modern humans descended from Neanderthals. false ______ Bipedal, upright-walking hominids existed at least 8.5 million years ago. true ______ Neanderthals had slightly larger brains than modern humans. true ______ Most of the modern marine fauna survived the Cretaceous mass extinction. Chapter Resources Menu Study Guide Section 24.1 Section 24.2 Section 24.3 Section 24.4 Chapter Assessment Image Bank Section 24.1 Study Guide Section 24.1 Main Ideas • Geologists hypothesize that Pangaea broke apart as heat built up beneath it. Expansion occurred and ultimately resulted in the rifting apart of Pangaea. • The first orogeny is characterized by igneous intrusions, whereas the second orogeny is characterized by thrust faulting and folding. Section 24.2 Study Guide Section 24.2 Main Ideas • The modern marine fauna include crabs, lobsters, shrimps, sponges, sea urchins, modern corals, snails, and clams. The major vertebrate groups of the modern fauna include bony fishes, sharks, aquatic reptiles, and aquatic mammals. • The oceans contained vast numbers of ammonites that are now index fossils. The most common land plants were cycads, and the dominant land animals were dinosaurs. • An upright posture distinguishes dinosaurs from other reptiles. Section 24.3 Study Guide Section 24.3 Main Ideas • The Cenozoic tectonism is characterized by vertical normal faulting. • During the Pleistocene, glaciers extended as far south as the courses of the Ohio and Missouri Rivers. Section 24.4 Study Guide Section 24.4 Main Ideas • Large mammals evolved to feed on the abundant grasslands that developed during the Cenozoic. As the ice ages approached, many of the mammals that lived on these grasslands became extinct and were replaced by large mammals that were adapted to the cold and arid land south of the glaciers. • Primates are mammals that developed specialized traits, including a grasping hand with an opposable thumb, stereoscopic vision, smaller, fewer, and less-specialized teeth, and a relatively large brain. Chapter Assessment Multiple Choice 1. How many episodes of orogenies did the western margin of North America experience during the Mesozoic? a. one c. three b. two d. four The three episodes of orogenies along the western margin of North America during the Mesozoic resulted in a tremendous number of igneous intrusions, low-angle thrust faulting, and vertical uplifts. Chapter Assessment Multiple Choice 2. What organism was the base of the marine food chain during the Mesozoic? a. phytoplankton c. coral b. trilobites d. sponges Phytoplankton are tiny, ocean-dwelling organisms that float near the surface of the oceans and make their own food through photosynthesis. They are still the base of the marine food chain today. Chapter Assessment Multiple Choice 3. All ornithischian dinosaurs were ____. a. carnivores c. endotherms b. herbivores d. ―lizard hipped‖ There were five different groups of ornithischian dinosaurs: stegosaurs, ankylosaurs, pachycephalosaurs, ceratopsians, and ornithopods. They were ―bird-hipped‖ even though modern birds probably descended from saurischian, or ―lizard hipped‖ dinosaurs. It is possible that some were endotherms, but it is not widely accepted that all were. Chapter Assessment Multiple Choice 4. Which of the following is a modern remnant of the Tethyan Sea? a. Arctic Ocean c. North Sea b. Baltic Sea d. Mediterranean Sea The Tethyan Sea separated Eurasia from Africa. As Europe and Africa continue to collide, the Mediterranean Sea will become narrower over time as the two continents move toward each other. Chapter Assessment Multiple Choice 5. All hominids are ____. a. bipedal c. herbivores b. carnivores d. Neanderthals The most recognizable feature that differentiates hominids from other hominoids is that they are bipedal. They have an upright posture resulting from the modification of the hipbone and they walk on two legs. Homo sapiens are hominids. Chapter Assessment Short Answer 6. What event led to the mass extinction that ended the Mesozoic? It is generally accepted that a large meteorite impact and massive volcanism occurred at the end of the Cretaceous. In the midst of a stressful time of climatic cooling, changing plant populations and a gradual decline in dinosaur diversity and abundance, the impact of a large meteorite likely caused the climax of the Cretaceous-Paleogene mass extinction. Chapter Assessment Short Answer 7. How were Neanderthals different from modern humans? Neanderthals had heavier brows, mouths that projected forward, receding chins, more massive, muscular bodies, and slightly larger brains than modern humans do. They also had a gap between their rear teeth and their jaw bone. Chapter Assessment True or False 8. Identify whether the following statements are true or false. ______ The Basin and Range Province formed through false compressional tectonism. ______ Mammals have two sets of teeth whereas true reptiles continuously replace older teeth. ______ Ginkgoes are an example of an angiosperm. false ______ Ammonites are important Mesozoic index fossils. true ______ Iridium is not common in rocks at Earth’s surface. true ______ All hominoids are bipedal with an false upright posture. Image Bank Chapter 24 Images Image Bank Chapter 24 Images Image Bank Chapter 24 Images To navigate within this Interactive Chalkboard product: Click the Forward button to go to the next slide. Click the Previous button to return to the previous slide. Click the Chapter Resources button to go to the Chapter Resources slide where you can access resources such as assessment questions that are available for the chapter. Click the Menu button to close the chapter presentation and return to the Main Menu. 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