geosyncline

noun Geology.

1. a portion of the earth’s crust subjected to downward warping during a large span of geologic time; a geosynclinal fold.

noun

1. a broad elongated depression in the earth’s crust containing great thicknesses of sediment

1. A usually elongate, basinlike depression along the edge of a continent, in which a thick sequence of sediments and volcanic deposits has accumulated.