Focus on Sedimentary Environments

A large saline lake

The Great Salt Lake, Utah, USA

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beach sand sample
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full-size image
Beach sediment from southern Great Salt Lake. Scale in mm.
thumbnails

Sediment texture

Look closely at the large image of the sediment. You should be able to distinguish two types of sand, each with a distinct size and grain shape. Describe the grain size and grain shape of each, then check your answers below. Further information on these and other sediment properties.

The finer size fraction

Identify the predominant grain size(s) in the finer sand size of the sample:
granules
very coarse sand
coarse sand
medium sand
fine sand
very fine sand
silt and clay
Now identify the dominant grain shape(s) in the smaller size fraction:

equant (cubic or spherical)
oblate (disc-shaped)
bladed
prolate (rod or roller shaped)
How would you describe the rounding of this sample (more than one answer may be correct)?
very angular
angular
subangular
subrounded
rounded
well rounded
We shall look more closely at the nature and origin of these grains in later images.

 

The coarser size fraction

Identify the predominant grain size(s) in the coarser size fraction:
granules
very coarse sand
coarse sand
medium sand
fine sand
very fine sand
silt and clay

Now identify the dominant grain shape(s) in the coarser size fraction:

equant (cubic or spherical)
oblate (disc-shaped)
bladed
prolate (rod or roller shaped)

What are these coarser grains likely to be?

 

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