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.

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

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.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.