Marginal Deep

a crustal depression formed at the boundary between a geosyncline (geosynclinal system) and a platform in the late stage of development of the geosyncline, when orogeny occurs in its interior areas. Marginal deeps are usually filled with sediments of predominantly lagoon and Molasse formations, layers of which are dislocated in the form of folded blocks and diapir domes. Deposits of coal, oil, and natural gas are associated with marginal deeps.