Bedforms and Cross-Stratification Produced by Currents

Bedforms are structures that are moulded on beds where deposition is taking place. Current-produced bedforms are diverse, and are useful indicators of depositional processes. Most bedforms migrate over the sediment surface. As a result, sediments deposited by bedforms typically show cross-stratification. The selection shown here includes both views of bedforms, and views of cross-stratification in strata deposited in bedforms.

linguoid ripples

Current-generated linguoid ripples, Kennetcook River, Nova Scotia, Canada

 

straight ripples

Straight-crested current ripples, Cambrian sandstone, Moraine Lake, Alberta

climbing ripple cross-lamination

Cross-lamination produced by current ripples, Quaternary fluvioglacial sands, Lothian, Scotland. The cross-lamination here includes both 'normal' (non-climbing) cross-sets and climbing-ripple cross-lamination.

dunes

Lunate (crescent-shaped) dunes in sand and gravel, Kennetcook River.

dune

Straight-crested dunes, also known as sand waves. Kennetcook River estuary, Nova Scotia

trough cross-bed Tough cross-bed, characteristic of deposition in lunate dunes. Wolfville Formation (Triassic), Nova Scotia

trough cross-bed

Tabular cross-beds, Goldenville Formation, Guysboro County NS.

trough cross-bed

Tabular cross-bedding produced by eolian dunes, Wolfville Formation, Red Head NS (Photo © David R. Brown)

Antidunes

Antidunes beneath fast-flowing stream, Kennetcook River. Flow is from left to right, but antidunes were visibly migrating slowly from right to left.