GEOL 256 Lecture 23: Clastic Sedimentary Systems 23
13 Nov 2020
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Document Summary
Clastic sedimentary rocks hold clues to tectonic processes at their sources. Composition of clast tells history of source rock. Provenance - reconstruction of the source(s) of sediments in a rock, including the plate tectonic setting. Poorly sorted, more diverse clast composition and size. This is why the river meanders in the direction of flow. Sequence of sediments that is indicative of a meandering river. Grain size decreases from bottom to top. Long = hundreds of miles between source mountains and delta. Granites and gneisses will always be arkosic. Refers to distance from the source to the deposition point. Young active orogeny / arc lithic source continent edge, mafic / intermediate igneous and lower-grade metamorphic. More lithics - often dark mafic material and rock fragments. Active orogeny / arc source continent edge, mafic igneous and low-grade metamorphic. Continent edge: mixed young igneous and metamorphic. Gravel beach - sediment isn"t traveling far enough to erode. Coastal orogeny sediments - short clastic system.
