ERSC 4P10 Lecture Notes - Lecture 2: Cross-Bedding, Cobequid Bay, Bedform
22 Jan 2016
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Document Summary
The form of cross-stratification depends on the geometry of the dunes. Planar cross-bedding within dunes (you should know the flow directions by now) Sets of planar tabular cross-beds interbedded with horizontally bedded sands. Trough shapes are visible on the vertical section oriented perpendicular to the flow direction. Due to deposition in the trough scours as the bedform migrates. Plan view of trough-crossbedding from the whirlpool sandstone (silurian; southern ontario: upper plane bed horizontal lamination. More-or-less horiozontal laminae extending in all directions in outcrop. Textural laminae: less than a millimetre thick laminae that fine or coarsen upwards. Heavy mineral sheets: one to several grains thick laminae that are enriched in opaque heavy minerals. Horizontal lamination formed on an upper plane bed in cobequid bay, nova scotia. Laminae are visible when enriched with opaque heavy minerals (heavy mineral sheets). Notably dark layers may be due to as little as a few percent opaque minerals in the laminae.
