NO5101 : Cross-bedding in Carboniferous Sandstone

taken 9 years ago, near to St Monans, Fife, Great Britain

Cross-bedding in Carboniferous Sandstone
Cross-bedding in Carboniferous Sandstone
This is a detail of the outcrop NO5101 : Below the Doocot. 2 coin for scale.

This was formed by a current flowing from right to left. It carried sand along with it, and the sand cascaded in miniature landslides down the sloping faces of previous ripples in the stream bed, laying don a succession of thin layers sloping at about 20 to the horizontal.

Look carefully at the left end of these sloping layers, and you can see that each one peters out asymptotically on top of the bed below.

Then look at the right end of the same layers, and you will see that they have been sharply cut off by the bottom of the next bed above as the stream has brought down a further load of sand and deposited it as the next bed up the sequence.

This is a classic example of cross-bedding, and you can see that by examining the detail of rocks like these, geologists can tell which way a stream was flowing many millions of years ago, and whether the rocks are still the 'right' way up or have been turned upside down by later tectonic movements.

The rocks here have been tilted, but not overturned, and the tilt is probably the result of volcanic intrusion.
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NO5101, 87 images   (more nearby search)
Photographer
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Date Taken
Sunday, 24 June, 2012   (more nearby)
Submitted
Wednesday, 27 June, 2012
Geographical Context
Geological interest 
Subject Location
OSGB36: geotagged! NO 5193 0119 [10m precision]
WGS84: 56:12.0523N 2:46.5809W
Camera Location
OSGB36: geotagged! NO 5193 0119
View Direction
NORTH (about 0 degrees)
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Cross-Bedding 

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