GEOL 106 Lecture 1 February, 2010 Test WEDNESDAY Formation of Earth, Dating, fundamentals of Sedimentary rocks Vail Sealevel Curve Relative variations of sea level Low in ice ages (water stored in glaciers ON contitnents, lower sealevel), high in warm periods. Eustatic sealevel ? sea level about equal on all continents simultaneously Sealevel & Tecton ics ? rates of ocean crust production correlate pos. with sealevels high sealevel caused by high level of volcanic activity ? CO2 released by volcanism Cyclical Ice / Green House Sequence Units: - basis for cycles of sediment deposition Unconformity-bound units reflected in geologic record (at shoreline) Caused by Transgressions / Regressions of ocean Transgressions ? shoreline, deposition moves inland Regressions ? shoreline, deposition move outward Marine Transgression: - shoreline migrates inland Marine deposits overly continental deposits sand (sandstone) facies at shoreline, mud (shale) facies offshore, carbonate (limestone) far oldest stone of EACH BAND is on seaward side, bands incline T-R Cycles: rising or falling sealevel land sinks or rises shoreline are filled in with sediment deposits Sedimentary cycles with v ertical trend of: change in water depth change in sediment type Unconformities: - gaps in the rock record Disconformity ? surface created by erosion or non-deposition Nonconformity ? sediments overlie igneous/metamorphic rocks Angular unconformity ? sediments overlie tilted strata Unconformities in Grand Canyon diagram, vertical timescale Facies ? lateral changes of sediment type, deposited at same time, DIFFERENT depositional environ. predictable patterns along gradients: elevation-depth, climate gradient
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