Offlap

offlap

[′ȯf‚lap]
(geology)
The successive lateral contraction extent of strata (in an upward sequence) due to their deposition in a shrinking sea or on the margin of a rising landmass. Also known as regressive overlap.

Offlap

 

(also regressive offlap), the deposit of strata of sedimentary rock as a result of regression of the sea. In cross section, an offlap is characterized by an alternation, from the bottom to the top, of fine detrital rocks (clays) and increasingly coarse-grained rocks (aleurites, sands, and gravels). There is a decrease in the area occupied by rocks of marine origin. The arrangement of the layers is used to reconstruct the geological history of ancient sea basins and the history of vertical movements of the earth’s crust.

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Over-lain by a red bed of the Gercus Fm, the Beciraman represents a marine offlap corresponding to continental beds related to extensive uplifts to the north and east.
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This drop in sea level within Hudson Bay and James Bay will lead to an offlap of water and an outward migration of shorelines.
Post-glacial isostatic adjustment and global warming in subarctic Canada: implications for islands of the James Bay region

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