onlap

[ on-lap, awn- ]
/ ˈɒnˌlæp, ˈɔn- /

noun Geology.

the advance of a sea beyond its former shore.
the layer or layers of sedimentary rock formed on a sea floor as a result of this advance.
Compare offlap.

Origin of onlap

First recorded in 1945–50; on + lap3