Focus on Sedimentary Environments

Ancient marine carbonate sands

Caswell Bay, Gower, South Wales, UK

	Thin section in plane-polarized light. Scale bar is in mm. Arrow shows way up.

Grain size and sorting

Describe the texture of the sample, then check your answers below:

Identify the predominant grain size(s) at point A:

granules
very coarse sand
coarse sand
medium sand
fine sand
very fine sand
silt and clay

Identify the predominant grain size(s) at point B:

granules
very coarse sand
coarse sand
medium sand
fine sand
very fine sand
silt and clay

Identify the predominant grain size(s) at point C:

granules
very coarse sand
coarse sand
medium sand
fine sand
very fine sand
silt and clay

Describe the sorting seen in the sample:

very well sorted
well sorted
moderately well sorted
moderately sorted
poorly sorted
very poorly sorted

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