EARTH238 Lecture Notes - Lecture 2: Isocline, Turbidity Current, Bouma Sequence
30 Aug 2016
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*refer to notebook for any diagrams associated with this lecture. Primary structures: original features of sedimentary/igneous rocks before they are deformed, non-tectonic, useful as markers (important in understanding geologic history of outcrops) *bedding is the best marker because it is planar and horizontal. Primary beds show folding nicely (isocline two sides parallel: younging indicators. Direction in which the rocks become younger/ direction to the depositional tops of the bed. Direction of reversal indicates some folding occurred (think of sheet of paper flat to folded: terms: bedding, stratigraphic facing, younging direction, graded bedding. Systematic variation in grain size within a bed (coarse grain base, fine grained top) This is due to change in the energy of the water carrying the sediment, as energy lowers bigger clasts settle first followed by smaller clasts. Shelf-edge failure, sediment at the corners of slopes fail due to seismicity or floods results in a large wave of sediment flowing down to a basin floor.
