Plio-Pleistocene Geology

Transcription

1 UNIVERSITY OF SOUTH ALABAMA GY 112: Earth History Plio-Pleistocene Geology Instructor: Dr. Douglas W. Haywick

2 Last Time A) Cenozoic Tectonics Western North American tectonic provinces Plateaus and canyons

3 Cenozoic Tectonic Events Final breakup of Gondwanna (Australia separated from Antarctica in the Latest Paleocene earliest Eocene epochs) India began to collide with Asia forming the Himalayan Mountain Range (Oligocene to Recent) Africa started to shift northward, gradually sliding under Europe and uplifting the Alps (Oligocene to Recent) Continued westward movement of North America and South America formed an on again off again land bridge between the two continents. This gave rise to some interesting animal exchanges (see evolutionary events below). North American orogenies become dominated by strike-slip faulting and uplift. Mountain building in the northern part of the Cordilleran mountains (mostly Canada) slows down stop during the Oligocene. Activity shifts to the southern part of the mountain chain (Colorado, Nevada etc.). Major late Tertiary flood basalt eruptions occur in Oregon and Washington state. Hot spot volcanism occurs in the area of Yellowstone (Pliocene to present). Composite volcanic eruptions (some incredibly explosive) periodically occurred and still do (e.g., Mt St Helen s).

4 Tectonic Events Cordilleran region Laramide orogeny New tectonic style

5 Cenozoic Tectonics Eocene Tectonic elements:

6 Cenozoic Tectonics Miocene Tectonic elements:

7 Cenozoic Tectonics Modern Tectonic elements:

8 Cenozoic Tectonics As North America drifts to the WNW, we eventually run over the leading edge of the East Pacific Rise Eocene

9 Cenozoic Tectonics As North America drifts to the WNW, we eventually run over the leading edge of the East Pacific Rise Oligocene

10 Cenozoic Tectonics Uplift As North America drifts to the WNW, we eventually run over the leading edge of the East Pacific Rise And uplift now affects the SW Today

11 Cenozoic Tectonics Key tectonic elements: 1) Farallon Plate (east of East Pacific Rise; east drift) 2) Pacific Plate (west of East Pacific Rise; west drift)

12 Cenozoic Tectonics Key tectonic elements: 1) Farallon Plate (east of East Pacific Rise; east drift) 2) Pacific Plate (west of East Pacific Rise; west drift) 3) Juan de Fuca Plate (east of East Pacific Rise; east drift) 4) Cocos Plate (east of East Pacific Rise; east drift)

13 Today s Agenda A) Finish off Cenozoic Tectonics B) Cenozoic temperature and sea level shifts C) Plio-Pleistocene Glaciations (Milankovitch Orbital Variations) D) Sea level changes in our own back yard Web notes 37

14 Cenozoic Tectonics Key tectonic style: simple uplift Laramide Orogeny

15 Cenozoic Tectonics One explanation for the uplift and high heat flow is shown here... low thrust angle shifts heat/magma generation eastward.

16 Cenozoic Tectonics One explanation for the uplift and high heat flow is shown here Another consideration is that we have increased convection associated with the East Pacific Rise that we ran over starting 20 million years ago

17 Cenozoic Tectonics Several important basins and tectonic provinces are recognized in the western USA

18 Cenozoic Tectonics Important Basins 1) Green River Basin 2) Uinta Basin 3) Washakie/Sandwash Basins 4) Piceance Creek Basin

19 Cenozoic Tectonics

20 Cenozoic Tectonics Important Basins 1) Green River Basin 2) Uinta Basin 3) Washakie/Sandwash Basins 4) Piceance Creek Basin All are rich in oil shale

21 Cenozoic Tectonics Important Tectonic Provinces

22 Cenozoic Tectonics 1) Basin and Range

23 Cenozoic Tectonics 1) Basin and Range 2) Colorado Plateau

24 Cenozoic Tectonics 1) Basin and Range 2) Colorado Plateau 3) Columbia River Plateau

25 Cenozoic Tectonics 1) Basin and Range 2) Colorado Plateau 3) Columbia River Plateau 4) Rio Grande Rift

26 Cenozoic Tectonics 1) Basin and Range 2) Colorado Plateau 3) Columbia River Plateau Basin and Range

27 Cenozoic Tectonics Basin and Range: Uplifted deformed strata

28 Cenozoic Tectonics 1) Basin and Range 2) Colorado Plateau 3) Columbia River Plateau Colorado Plateau

29 Cenozoic Tectonics Colorado Plateau: Uplifted undeformed strata

30 Cenozoic Tectonics Miocene Columbia Plateau basalts Up to 5 km thick

31 Cenozoic Tectonics Columbia River Plateau: Basalt lava flow covered terrain

32 Cenozoic Tectonics Rio Grande Rift: Uplifted rifting strata

33 Cenozoic Tectonics Rio Grande Rift: Uplifted rifting strata

34 Cenozoic Tectonics Other interesting Cenozoic (Recent) Tectonics: 1) Yellowstone

35 Cenozoic Tectonics Other interesting Cenozoic (Recent) Tectonics: 1) Yellowstone 2) Crater Lake

36 Cenozoic Tectonics Other interesting Cenozoic (Recent) Tectonics: 1) Yellowstone 2) Crater Lake 3) Composite Volcanoes

37 Cenozoic Tectonics

38 Plio-Pleistocene Is most notable for rapid, short duration shifts in temperature and ice volume.

39 Plio-Pleistocene Is most notable for rapid, short duration shifts in temperature and ice volume.

40 Plio-Pleistocene Is most notable for rapid, short duration shifts in temperature and ice volume. Why?

41 Plio-Pleistocene Glaciations started around 5 million years ago. Isthmus of Panama Emplaced M years ago Started modern circulation Gulf stream carries salty Atlantic north Cools, sinks Oceanic conveyor belt High latitudes cool

42 Milankovitch Cycles Three major changes in Earth s orbit are linked to glacial oscillations Eccentricity Obliquity Precession

43 Milankovitch Cycles When taken together, the 3 cycles are capable of dropping temperatures globally

44 Milankovitch Cycles When taken together, the 3 cycles are capable of dropping temperatures globally. These cycles have been confirmed via stable isotope analysis of deep sea foraminifera (ice volume).

45 Paleoclimate Phases We now recognize two major Earth climatic phases 1) Greenhouse Earth (no continental glaciers present) 2) Icehouse Earth (continental glaciers present)

46 Paleoclimate Phases Icehouse Earths fluctuate between 2 stages: a) Glacial stage (18 KA) b) Interglacial stage (Today)

47 The Present Ice House Earth Glacial/ interglacial stage Name of stage Time frame interglacial Holocene 0-10 KA glacial Wisconsinian KA interglacial Sangamon KA glacial Illinoisan KA interglacial Yarmouth KA glacial Kansan KA interglacial Aftonian KA glacial Nebraskan > 500 KA

48 The Ice Age Glacial Maximum Extent of continental glaciation Several lines of evidence 1) Erratic boulders

49 The Ice Age 2) Glacial till and basins associated with glaciation 3) Depression of the land Hudson Bay

50 The Ice Age Lowering of sea level Exposed continental shelves

51 The Ice Age Migration of species Mammals crossed Bering Strait on land corridors Vegetation changed in response to global changes

52 The Ice Age Ocean circulation changed during glaciation Glacier in NJ Tundra in Washington, D.C.

53 The Ice Age Great lakes Last glacial maximum 35,000-10,000 years ago Wisconsin Stage Remained when ice sheets melted back

54 The Ice Age Climate impacts were felt globally Steepened temperature gradients Increased aridity Exception: Great Basin Lakes Great Salt Lake

55 The Ice Age Climate impacts were felt globally Sahara expanded Rain forests restricted Isolated gorilla species

56 End of the Ice Age Glaciers began to retreat around 15,000 years ago Waters drained to lakes Sea level rose Tundra shifted northward Deciduous trees migrated northward

57 Transgression Sea Level Lagoonal complexes transgress over coastal plain sediments Regression High sediment supply is causing coast to move offshore Texas

58 In southern Alabama, regressions caused the shoreline to shift 100 miles south. Base level of rivers dropped by 300 feet. Sea Level The Mobile River carved a canyon, the remnants of which are still exposed along the Eastern Shore

59 In southern Alabama, regressions caused the shoreline to shift 100 miles south. Base level of rivers dropped by 300 feet. Sea Level The Mobile River carved a canyon, the remnants of which are still exposed along the Eastern Shore

60 The End

61 Today s Homework 1. Time Chart 3 due Thursday April 30 th 2. Lab exams for Haywick s classes tomorrow Next Time 1. Review Session

62 GY 112: Earth History Lectures 37: Plio-Pleistocene Instructor: Dr. Doug Haywick This is a free open access lecture, but not for commercial purposes. For personal use only.