EARTHSC 1122 Lecture Notes - Lecture 17: Ripple Marks, Sedimentary Structures, Caliche
4 Dec 2015
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What tools can we use to interpret depositional environments: fossils (body fossils, trace fossils, walters law, sediment type, sedimentary structures. Sedimentary structures: bedding: horizontal bedding, flat layers caused by short lapses in sedimentation or changes in grain size or composition, strata (laminae, bedding, thin-bedding, if preserved, is due to lack of extensive burrowing. Cross-bedding and ripple marks: cross-bedding, ripple marks, bedding planes rippled by currents, strata are inclined at different angles (caused by changes in current direction or strength). Types of ripple marks: asymmetric ripple marks, unidirectional current, environments: rivers, beaches, deserts, etc, symmetric ripple marks, bidirectional (oscillatory) currents, environments: tidal flats, ponds, etc. Graded bedding: vertical change from large to small grain size (due to one rapid depositional event, environments: floodplains (levees), continual rise (turbidites), etc. Mudcracks and raindrop impressions: mudcracks, polygonal structures caused by drying of mud, raindrop impressions, little craters caused by raindrops falling on wet mud, environments: wet/dry terrestrial settings.
