EARTH SCIENCE geology, the environment, and the universe 2008 (24)

BIG Idea Complex life developed and diversified during the three eras of the Phanerozoic as the continents moved into their present positions (tl)John Koivula/Photo Researchers, Inc., (c)Breck P Kent/Animals Animals, (bkgd)David Wall/Lonely Planet The Paleozoic, Mesozoic, and Cenozoic Eras Insects trapped in amber Magnification: 5× 23.1 The Paleozoic Era MAIN Idea Life increased in complexity during the Paleozoic while the continents collided to form Pangaea 23.2 The Mesozoic Era MAIN Idea Reptiles became the dominant terrestrial animals in the Mesozoic while Pangaea broke apart 23.3 The Cenozoic Era MAIN Idea Mammals became the dominant terrestrial animals in the Cenozoic while the continents assumed their present forms GeoFacts • Relatives of New Zealand’s Kauri trees first appeared in the Jurassic, nearly 200 mya • When injured, Kauri trees secrete resin, which hardens into amber • Cell structures of insects trapped in amber can be preserved for millions of years 646 Amber Start-Up Activities Life-Forms of the Paleozoic Make a Foldable to compare the life-forms of the early, middle, and late Paleozoic LAUNCH Lab How is oil stored in rocks? Many sedimentary rocks contain oil and water How are these materials stored in sedimentary rocks? Fold a sheet of paper to the margin line STEP STEP Fold the sheet into thirds STEP Cut along the fold lines of the top flap to make three tabs Label the tabs Early Paleozoic, Middle Paleozoic, and Late Paleozoic Procedure Read and complete the lab safety form Place an unglazed brick or sandstone sample on your table Sketch and label a magnified cross section of the brick or sandstone before you add the oil or water Using a dropper, slowly squeeze three to five drops per of water or oil onto the brick or sandstone for 10 Revise your sketch to show the view after you added the oil or water Analysis Infer Observe the brick or sandstone sample Where did the water or oil go? Compare and contrast the appearance of the brick before and after the oil or water was added Conclude how rocks in nature store oil and water FOLDABLES Use this Foldable with Sections 23.1, 23.2, and 23.3 As you read, use your Foldable to describe the life-forms present, including the names of specific plants and animals Visit glencoe.com to study entire chapters online; explore • Interactive Time Lines • Interactive Figures • Interactive Tables animations: access Web Links for more information, projects, and activities; review content with the Interactive Tutor and take Self-Check Quizzes Chapter 23 • The Paleozoic, Section 1Mesozoic, • XXXXXXXXXXXXXXXXXX and Cenozoic Eras 647 Doug Martin Section The Paleozoic Era Objectives ◗ Define the term passive margin ◗ Explain how transgressions and regressions indicate sea-level changes ◗ Discuss the tectonic forces that shaped Laurentia during the Paleozoic ◗ Summarize the changes in Paleozoic life-forms MAIN Idea Life increased in complexity during the Paleozoic while the continents collided to form Pangaea Real-World Reading Link Have you noticed that some things seem to hap- pen all at once? For instance, you might notice that everyone at school is suddenly talking about a certain music group that just yesterday was unknown In a similar way, there suddenly appeared in the Paleozoic rock record an entire collection of new, complex life-forms Review Vocabulary Paleozoic Paleogeography evaporite: a sediment deposit that has crystallized out of water supersaturated with dissolved minerals The geologic activity of the three eras of the Phanerozoic Eon are well represented in the rock record By studying this record, geologists can reconstruct estimates of landscapes that have long since disappeared The ancient geographic setting of an area is called its paleogeography (pay lee oh jee AH gruh fee) The paleogeography of the Paleozoic Era — the first era of the Phanerozoic — is defined by the breakup of the supercontinent Rodinia As this breakup proceeded, multicellular life evolved with increasing complexity, as illustrated in Figure 23.1 New Vocabulary paleogeography passive margin transgression regression Cambrian explosion Passive margins Recall from Chapter 22 that the ancient North American continent of Laurentia split off from Rodinia by the early Paleozoic Laurentia was located near the equator and was surrounded by ocean In addition, it was almost completely covered by a shallow, tropical sea Throughout the Cambrian, there was no tectonic activity on Laurentia so no mountain ranges formed The edge of a continent is called a margin When there is no tectonic activity along a margin, it is called a passive margin During the Cambrian, Laurentia was completely surrounded by passive margins — there was no tectonic activity along its edges ■ Figure 23.1 Life-forms became more complex during the seven periods of the Paleozoic Paleozoic Era mya 542 488.3 443.7 416 359.2 299 251 Period Cambrian Ordovician Silurian Devonian Carboniferous Permian Primitive fishes appear Plants colonize land Insects and amphibians appear Seed plants dominate land Reptiles become dominant Major biological events Cambrian explosion occurs 648 Chapter 23 • The Paleozoic, Mesozoic, and Cenozoic Eras Original shoreline position Limestone Beach sand becomes sandstone Clay-rich sediment becomes shale CaCO3-rich sediment becomes limestone Shale Sandstone Figure 23.2 A vertical sequence of sandstone-shale-limestone in the rock record indicates that an ancient shoreline moved inland as sea level rose This inland movement is called a transgression ■ Sea Level Changes in the Rock Record Rock sequences preserved in passive margins tell paleogeographers a great deal about ancient shorelines These sequences are useful in charting the rise and fall of sea level To understand this, it is first necessary to understand how sediment is deposited on a shoreline Shoreline deposition Ocean tides wash small grains of sand and sediment ashore to make beaches Tides also deposit offshore sediment the size of clay particles (