Ancient marine carbonate sands

Caswell Bay, Gower, South Wales, UK


	Sedimentary structures

The image above shows a cross section, perpendicular to bedding. The coin is 27 mm in diameter.

Move your cursor over the image to see some of the sedimentary structures picked out.

These are trough cross beds of fairly small size (sets are on the order of 30 to 100 mm high)
they represent the downstream migration of 3-dimensional ripples or small dunes
migration occurred during the action of unidirectional currents
these bedforms indicate the lower flow regime
there is significant variation in current direction
- set A shows flow towards the right
- set B shows flow towards the left
this variation may be the result of the action of tidal currents