Mesozoic Earth History

Transcription

1 Mesozoic Earth History The Mesozoic Era MYA Breakup of Pangea Changes in air and oceanic currents Evolution of new terrestrial and marine life Opening of the Atlantic Ocean Basin Rocky Mountains Salt deposits Batholiths with ore deposits 1

2 Breakup of Pangea Rifting between Laurasia and Gondwanda Triassic Rifting of North America from South America Late Triassic Jurassic Australia/Antarctica separate from South America/Africa Late Triassic-Jurassic India separates from Gondwana Late Triassic-Jurassic 2

3 Breakup of Pangea - continued South America separates from Africa Jurassic - Cretaceous Australia and Antarctica split Cretaceous India travels to Equator - Cretaceous Greenland becomes independent landmass Cretaceous - Cenozoic 3

4 Evaporite Deposits form in early Mesozoic Narrow basins Near Equator High heat flow Oceans and Seaways Tethys Ocean begins to close in Jurassic continues through Cretaceous Atlantic Ocean opens - Cretaceous 4

5 Effects of Pangea Breakup on Global Climate Patterns Pangea was mostly arid Large continental land mass Surrounded by mountain ranges Evidence = evaporites, sand dunes and red beds Some humid regions in Triassic; Evidence= coal deposits High latitudes like Scottish peat bogs Some humid regions around Tethys seaway as it opened (warm, monsoons) 5

6 Permian Guadalupe Mountains / Permian Guadalupe Mtns 6

7 Triassic Marginal Marine Coal 7

8 Effects of Pangea Breakup on Global Climate Patterns and Ocean Circulation Temperature gradient Difference in temperature between poles and tropics Affects speed of atmospheric and oceanic circulation (steeper gradient, faster circulation) Oceans absorb 90% sun s heat; continents only 50% or less Ocean dominated = warmer Effects of Pangea Breakup on Global Climate Patterns and Ocean Circulation Steeper thermal gradient as continents moved northward Oceans and atmosphere accelerated circulation Seasonality increases on land Warm water from Tethys circulation kept climate equable worldwide through Cretaceous In general, circulation patterns more complex as Mesozoic progressed. 8

9 Mesozoic History of North America Early Triassic Same as Permian connected to Pangea East Appalacian Mountain Belt West Cordilleran mobile belt Suturing of volcanic island arc Sonoma orogeny Late Triassic Jurassic N. America begins to separate from Africa Fault block and igneous activity in Appalacians N. America separates from South America Gulf of Mexico fills with evaporites Major Mountain building resulting in Sierra Nevada and Rocky Mountains Cordilleran orogeny 9

10 Mesozoic History of North America Cretaceous rise of sea level Marine deposition over most of N. American Cordilleran Absaroka Sequence; Zuni Sequence Regional Mesozoic History Eastern North America Early Triassic Uplifted Appalacians erode to low hills Late Triassic uplift and fault block basins from rifting (breakup of Pangea) Deposition in non-marine basins of Newark Group many dinosaur footprints Igneous activity lava flows and intrusions Palasades sill Jurassic and Early Cretaceous Erosion Cretaceous Re-elevation of Appalacians; creation of Atlantic Coastal plain sediments 10

11 Association of Rifting with Normal Faults 11

12 Palasades Sill 12

13 Regional Mesozoic History Gulf Coastal Region Late Triassic-Early Jurassic Gulf began as N. America separated from S. America Shallow, restricted basin Filled with evaporites Later associated with petroleum accumulation Late Jurassic normal marine Transgression and regression Deep sedimentary pile Cretaceous seaway to Arctic Ocean Extensive reefs composed of bivalve, rudists became reservoirs for oil 13

14 Regional Mesozoic History Western Region Permian-Triassic Western island arc formed Subduction of oceanic plate beneath island arc Thrusting of Island arc eastward against craton = Sonoma Orogeny Suturing of island arc terrane to western edge of N. America 14

15 Regional Mesozoic History Western Region Late Triassic Subduction Zone to the west where N. America overrides Farallon Plate Middle to Late Jurassic Two subduction zones dipping in opposite directions N. America overrides Farallon Plate eliminating the westward subduction zone 15

16 Regional Mesozoic History Western Region Late Jurassic Cenozoic Franciscan Complex Chaotic mixture of rock types Represent continental shelf, slope, deep-sea environment rocks all brought together in a trench, partly subducted, then squeezed against N. America Great Valley Group Sedimentary rocks of the Continental shelf, slope collecting at same time as Franciscan Now in thrust fault relationship with Franciscan Franciscan Formation/Group 16

17 Great Valley Group Thin turbidites of Great Valley Group 17

18 Regional Mesozoic History Western Region Orogenies of the Western Region Nevadan Granitic masses beneath N. America became the batholiths of the Sierra Nevada, Southern California, Idaho, and Coast Range Contemporaneous with Franciscan/Great Valley Change from high angle to low angle subduction moved plutonism and volcanism to the east 18

19 Orogenies of the Western Region Sevier Orogeny Numerous overlapping thrust faults Moved blocks of older strata over younger Mountains of Montana to Western Canada Laramide Orogeny Developed east of the Sevier Rocky Mountains mostly Cenozoic Mesozoic Sedimentation Triassic of the western continental shelf Shallow marine sandstone, shale and limestone Regression to erosion and red beds Moenkopi Formation tracks and fossil amphibians and reptiles Shinarump conglomerate Chinle Formation petrified forest and fossil amphibians, phytosaurs, small dinosaurs 19

20 Mesozoic Sedimentation Jurassic Cross-bedded sandstones from dunes Wingate Sandstone Navajo Sandstone prominent Sundance Sea produced Sundance Formation Mountain building shed sediments eastward and Sundance Sea northward Morrison Formation - Dinosaurs Mesozoic Sedimentation Cretaceous Early to mid-cretaceous transgression led to mid continental seaway Black Shales Sevier orogenic belt fed sediments to interior As regression took place coal bodies formed 20

21 Accretion of Terranes Terranes Small accreted lithospheric blocks that are clearly of foreign origin Differ from surrounding blocks and cratons Fossil content Structural trends Stratigraphy Paleomagnetic properties Almost certainly of foreign origin carried for many miles as continental or other plate fragments Terranes Composed of Volcanic island arcs Oceanic ridge fragments (ophiolites) Seamounts Hot spot tracks Fragments of continents Examples Wrangellia terranes (continent) Klamath Mountains (island arc) 21

22 Mesozoic Mineral Resources Coal Rocky Mtns. Petroleum of Persian Gulf and Gulf of Mexico Uranium of Mid Continent N. America Diamonds of S. Africa Gold of the Mother Lode Copper of N. and S. America 22