Paleogeography 1 Geography of the past 2 Ancient environment reconstructed from geologic evidence using the concept of actualism a Paleoenvironmental reconstruction i Dinosaur habitat 1 Mainly aquatic 2 Terrestrial terrestrial strata 3 Sediment properties a Gravel sand and mud size sediments b Rounding of grains i Angular volcanic eruption ii Sub rounded iii Rounded river c Poorly sorted well sorted 4 Paleoenvironmental reconstruction a Sediment structures i Ripples shapes and orientation ii Mud cracks arid environment iii Cross beds ripples changed direction iv Graded bedding courser grains at bottom get smaller as you go up v Rhythmic layering seasonal deposition b Biota fossils 5 To identify sediment environment a Sediment property sediment deposition b Geologic location PT setting c Climate precipitation d Transport agent water wind ice e Biotic organisms and processes 6 Glaciers a Boulders pebbles sand mud b Not well sorted c varves striation tills moraine outwash dropstones 7 Lake 8 Desert a Fine grain b Well sorted c Varves freshwater biota a Sand b Well sorted c Troff crossbeds mudcracks absence of vegetation 9 Marine delta 10 Lagoons a Sand can be larger finer as you go out b Well sorted a Mud silt b Well sorted c Mudcracks rhythmic bedding 11 Deep marine a Sand mud silt b Well sorted c Ripples biota turbitity currents 12 River a Sand mud silt pebbles boulders b Varies c Levees channels ripples crossbedding 13 Meandering River a Course channel sedimaent b Point bar sands c Floodplain muds d The lateral shifting environments produces a verticle sequence that changes from course to fine sediment associated with adjacent environments e Curvature Walther s Law 1 When depositional environments migrate laterally sediment of one environment come to lie on top of sediment of an adjacent environment 2 Meandering river 3 What verticle sequence is likely to occur if a barrier island migrates landward a Bottom small grains sand mud organic b Top well sorted sand 4 Moves seaward a Sand mud organic on top of well sorted sand
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