Examples of cross bedding characteristic of sands deposited in shallow water with fluctuating currents. Sand at the leading edge of a growing delta is deposited in layers tangential to the bottom surface. Should subsequent erosion remove part of the deposit, any later layers will cover the truncated layers. The resulting cross bedding shows that the sand was deposited in shallow water; it also tells us whether the block of stone is "right-way up" or whether it has been turned upside down.

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Red sandstone:
Peddie
High Street
Red sandstone:
High Street at
Methven Street
Grey sandstone:
Sheriff Court
Grey sandstone:
City Hall S. side
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Coarse sandstone:
Railway Station
Platform 5
Red Sandstone:
Dumfries
Right-way up
Red Sandstone:
Dumfries
Upside down!

In a desert, wind blows the sand grains up the gentle windward slope of the dunes. Reaching the crest the grains avalanche down the steep lee slope. As a result the dunes migrate downwind. Wind sorts desert sand more efficiently than water currents do in rivers or marine deposits. The layers of sand in a dune sand are finer than the stratification of sand deposited in water. Erosion and slumping of the fine layers can also result in cross bedding.

A good example is seen in the blocks used for new pillars constructed to support the flood gate at the SE corner of the North Inch. Click on this thumbnail picture to display a larger image.

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cross bedding