24_G435.pps 1 The Earth Through Geologic Time

24_G435.pps 2 Is the Present ALWAYS the Key to the Past? Uniformitarianism –processes (physical, chemical, and biological) in the geological past are similar to today Catastrophism –periodic catastrophic (high energy/short duration) events dominate the geological record Punctuated Uniformitarianism –Short lived high magnitude events leave a comparable record(in terms of the proportions of the geological record) compared to slow, persistent, low energy events.

24_G435.pps 3 Important Episodic Events Earthquakes Volcanic eruptions Storms Jokulhlaups –Outburst floods in glacial terranes Submarine slumps

24_G435.pps 4 Uniformity? of Physical, Chemical, and Biological Processes Through Earth History Biosphere changes –Carbonate Bioclasts Sediment particles a result of biological processes and organic evolution –Changes in Vegetation –Atmosphere composition and Atmospheric Circulation

24_G435.pps 5 Carbonate Sedimentation –> 1 Ga only cyanobacteria, stromatolitescyanobacteria –Global O 2 pollution event –<1 Ga metazoans (multicellular organisms) –<600 Ga reefs formed by varying dominant species –<~200Ma Planktonic, calcareous organism (Foraminifers, Coccoliths) Calcareous, pelagic ooze

24_G435.pps 6 Reef Forming Organisms –Carbonate buildups with a rigid (intergrown) framework

24_G435.pps 7 Changes in Vegetation –>400 Ma no land plants –>~100 Ma no angiosperms (plants with only minimal root systems) –>~30 Ma no grasses Strong influence on: –physical and chemical weathering –terrestrial sedimentation aeolian and fluvial depositional systems

24_G435.pps 8 Atmosphere and Atmospheric Circulation Early Atmosphere –N 2 & CO 2 dominated (volcanic emanations) Advent of life and evolution of Photosynthesis –~2000 Ma Production of O 2 Stage is set for heterotropy (non-photosynthesizing organisms) –>~2000 Ma BIF (Banded Iron Formation) chert +/- Fe+3

24_G435.pps 9 Cause/Effect of Atmospheric Composition and Circulation Biological activity – CO 2 /O 2 –Photosynthesis/respiration through time Weathering –Urey equation gas + rock - > foram + diatom CO 2 + CaSiO 3 -> CaCO 3 + SiO 2 Continent and Topographic Configuration Polar Ice Cap advance/ retreat & atmospheric circulation (AP driven circulation cells)

24_G435.pps 10 Cause/Effect of Atmospheric Composition and Circulation Ocean Circulation –Effectiveness of CO 2 solution in the deep ocean Green House Effect: –Green House/Ice House conditions

24_G435.pps 11 Plate Tectonics/ Ocean Circulation/ Eustacy/Paleoclimates Intimately related and fundamental to the sedimentary record in Sedimentary Basins –Anorogenic Areas (little/slow) tectonism--> Climate and Eustacy dominant on sedimentation Chemical vs Physical weathering dominates vegetation influences weathering (climate factors) Eustacy dominates creation of accommodation space –Orogenic Areas (rapid tectonism): Sedimentation strongly influenced by tectonism depositional systems with high relief physical weathering dominates accommodation space mostly influenced by tectonics

24_G435.pps 12 Plate Tectonics/ Ocean Circulation/ Eustacy/Paleoclimates Late Cretaceous Changes in Plate Configuration, Topography and Bathymetry (Hypsography), and Paleoclimates 1. High sea floor spreading rates/greater total length of MOR 6. Lesser production of terrigenous clastics 2. Elevated eustatic sea level7. Less atmospheric CO 2 sequestered in weathering (CO 2 emissions from volcanism) 3. Globally subdued topography (fewer convergent plate boundaries) 8. Warmer Climate/ocean (5-10 o C > than today); Diminished/slowed thermohaline circulation 4. Greater % of Earth surface is ocean9. Less atmospheric CO 2 sequestered in the deep ocean 5. Areally extensive epicratonic seas and greater production of carbonate sediments 10. Change in the position of the CCD; etc

24_G435.pps 13 Climate Forcing Factors Amount and distribution of solar radiation Milankovitch Cycles –Orbital eccentricity (shape of Earth orbital path) –Rotational axis obliquity (axis tilt) –Rotational axis precession (axis wobble)