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Earth History, Ch. 161 Reminders Lab exam next Tuesday –Open lab today and Monday.

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Presentation on theme: "Earth History, Ch. 161 Reminders Lab exam next Tuesday –Open lab today and Monday."— Presentation transcript:

1 Earth History, Ch. 161 Reminders Lab exam next Tuesday –Open lab today and Monday

2 Earth History, Ch. 162 Early Mesozoic Era Jurassic System Triassic System Late Early Middle Late 142 206 251 Jurassic System named in early 1900’s for classic exposures in the Alps. Triassic System named in 1834 by von Alberti in Germany. Triassic is bounded by mass extinc- tions above and below.

3 Earth History, Ch. 163 Early Mesozoic marine life End-Permian mass extinction wiped out: –Corals, fusulinids, blastoids, trilobites, most crinoids, most brachiopods, most bryozoans Paleozoic invertebrate faunas were dominated by sessile, filter-feeding organisms End-Permian mass extinction caused a complete reorganization of marine communities

4 Earth History, Ch. 164 Sepkoski’s three faunas (marine invertebrates) mostly sessile filter-feeders mostly active grazers and carnivores

5 Earth History, Ch. 165 Triassic hexacorals Hexacorals probably are not related to Paleozoic corals, but evolved indepently from sea anemonies. Explosive adaptive radiation started in late Triassic time.

6 Earth History, Ch. 166 Pelagic organisms Calcareous nannoplankton Ammonoids and belemnoid

7 Earth History, Ch. 167 Early Mesozoic marine vertebrates Swimming reptiles diversified in Triassic time –Nothosaurs (seal-like) –Placodonts (turtle-like) –Plesiosaurs (giant “Nessie-like”, up to 40 feet long) –Ichthyosaurs (dolphin-like) –Crocodiles

8 Earth History, Ch. 168 Nothosaur

9 Earth History, Ch. 169 Placodont

10 Earth History, Ch. 1610 Plesiosaurs

11 Earth History, Ch. 1611 Ichthyosaur

12 Earth History, Ch. 1612 Early Mesozoic terrestrial animals Therapsids (primitive synapsids) barely survived end-Permian mass extinction –Then gave rise to true mammals in late Triassic time Earliest mammals were small and inconspicuous –No larger than a house cat

13 Earth History, Ch. 1613

14 Earth History, Ch. 1614 Origin of the dinosaurs Thecodonts were small early Triassic reptiles that gave rise to earliest dinosaurs Early dinosaurs were small, but by end of Triassic some reached up to 20 feet in length By early Jurassic time, many kinds of huge dinosaurs existed

15 Earth History, Ch. 1615 Thecodonts and early mammal

16 Earth History, Ch. 1616

17 Earth History, Ch. 1617 Allosaurus (Jurassic)

18 Earth History, Ch. 1618 thecodont

19 Earth History, Ch. 1619 Dinosaur pelvises Saurischian pelvisOrnithischian pelvis

20 Earth History, Ch. 1620 Saurischian pelvis Ornithischian pelvis

21 Earth History, Ch. 1621 Saurischian pelvis and legs (compared with modern bird)

22 Earth History, Ch. 1622 Jurassic dinosaurs Morrison Formation (extends from Montana to New Mexico) has best assemblage of Jurassic dinosaurs in world Dinosaur “Bone Wars” –Cope vs. Marsh feud –Gun battles and railroad cars full of bones!!

23 Earth History, Ch. 1623 “Bone Wars”

24 Earth History, Ch. 1624 Morrison Formation

25 Earth History, Ch. 1625 Earliest vertebrate flight Pterosaurs (late Triassic reptiles) were earliest flying vertebrates Probably clumsy upon take-off and landing, but well suited for soaring through the air

26 Earth History, Ch. 1626 Earliest birds First true birds appeared in late Jurassic time (evolved from saurischian dinosaurs)

27 Earth History, Ch. 1627 Archaeopteryx from Solnhofen Limestone (Germany)

28 Earth History, Ch. 1628 World’s smallest dinosaur

29 Earth History, Ch. 1629 Today’s outline Early stages in break-up of Pangaea Early Mesozoic geology of eastern and western North America

30 Earth History, Ch. 1630 Permian Pangaea Tethys Ocean

31 Earth History, Ch. 1631 Early stages in the break-up of Pangaea Westward expansion of Tethys seaway 1.Rifting between northern Africa and southern Europe (Triassic time) 2.Rifting between North America and South America, and between North America and Africa (Jurassic time) Incipient rift basins were periodically flooded by shallow seas –Evaporite deposition in proto-Mediterranean, proto- Gulf of Mexico, proto-South Atlantic

32 Earth History, Ch. 1632 Rift/Drift Sequence of events Break-up of a continent follows a predictable sequence of events –Rifting, accompanied by block-faulting, volcanism, non-marine sedimentation –Flooding by shallow marine waters (with periodic evaporation) –Establishment of fully marine conditions

33 Earth History, Ch. 1633

34 Earth History, Ch. 1634 Modern analog East Africa rift valley and Red Sea area is a modern example of continental break-up

35 Earth History, Ch. 1635 Break-up of Pangaea 12 43

36 Earth History, Ch. 1636 Triassic

37 Earth History, Ch. 1637 Early Jurassic

38 Earth History, Ch. 1638 Middle Jurassic

39 Earth History, Ch. 1639 Late Jurassic

40 Earth History, Ch. 1640

41 Earth History, Ch. 1641 Early Mesozoic evaporite basins

42 Earth History, Ch. 1642 Jurassic evaporites in Gulf of Mexico “Louann Salt” underlies almost entire floor of Gulf of Mexico Under burial conditions, evaporite rocks behave like ductile plastics—they flow Salt domes and salt rafts create spectacular traps for hydrocarbons

43 Earth History, Ch. 1643 Gulf of Mexico Salt domes

44 Earth History, Ch. 1644 Eastern U.S. rift basins Appalachian Mountains were eroding during early Triassic time Rifting (break-up of Pangaea) reached eastern North America by late Triassic-early Jurassic time Normal faults (extensional) created deep basins that received thick deposits of non-marine sediments –Newark Supergroup: 6 km thick

45 Earth History, Ch. 1645 Late Triassic– Early Jurassic rift basins

46 Earth History, Ch. 1646 Newark Basin Tr-Jr non-marine eroded Appalachians Mafic intrusives (dikes and sills)

47 Earth History, Ch. 1647 Palisades sill (across Hudson River from New York City)

48 Earth History, Ch. 1648 Triassic

49 Earth History, Ch. 1649 Early Jurassic

50 Earth History, Ch. 1650 Middle Jurassic

51 Earth History, Ch. 1651 Late Jurassic

52 Earth History, Ch. 1652 Western U.S. accreted terranes Continental growth by accretion began in Paleozoic time –Antler orogeny (Devonian-Mississippian) –Klamath island arc Accretion of microplates and island arc terranes continued throughout Mesozoic time

53 Earth History, Ch. 1653 Sonoma Orogeny Early Triassic accretion of Golconda arc and Sonomia microcontinent to western North America –Present-day western Nevada, northern California, southeastern Oregon

54 Earth History, Ch. 1654 Sonoma orogeny

55 Earth History, Ch. 1655 Western accreted terranes Early Triassic (Sonoma)

56 Earth History, Ch. 1656 Nevadan Orogeny: Continued accretion Beginning in middle Triassic time, and continuing through late Jurassic time, exotic terranes repeatedly were accreted to western North America Franciscan and Great Valley sequences (California) Stikine terrane et al. (Canada–Alaska)

57 Earth History, Ch. 1657 Western accreted terranes Late Jurassic (Nevadan)

58 Earth History, Ch. 1658 Early Mesozoic of Iowa No Triassic rocks in Iowa (surface or subsurface) Jurassic rocks crop out in vicinity of Ft. Dodge (Webster County) –Ft. Dodge Formation is gypsum deposit (evaporite) –Iowa is 2 nd largest gypsum producing state in U.S. (1.65 million tons/year) –Same age as dinosaur-bearing Morrison Formation to the west

59 Earth History, Ch. 1659

60 Earth History, Ch. 1660 early Late Jurassic

61 Earth History, Ch. 1661 Ft. Dodge Formation

62 Earth History, Ch. 1662 Jurassic rocks of midcontinent

63 Earth History, Ch. 1663 Cardiff Giant

64 Earth History, Ch. 1664 Cardiff Giant Man-like figure carved from Ft. Dodge gypsum 10’ 4.5” long, 3’ wide, 2990 pounds Cooked up as a hoax in 1866 by George Hull (visiting his sister in Ackley, Iowa) Now preserved in Cooperstown, New York


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