Preliminary Results from DSDP Leg 79 Seaward of the Mazagan Plateau off Central Morocco

Abstract

The region of the Mazagan Plateau (Figure 1) offers unique access for Glomar Challenger to document the Jurassic environment of rifting and the early subsidence history of a segment of passive margin bordering the proto-Atlantic. The edge of the Upper Jurassic carbonate platform bulges seaward here from its normal position beneath the present Moroccan continental shelf, and crops out along a spectacular escarpment that falls about 1 km to a broad slope leading to the abyssal sea floor (Figures 2 and 7). The escarpment reveals a section of Mesozoic strata, near the base of which Oxfordian algal limestone has been dredged. With a series of holes drilled near the escarpment, we planned to piece together a composite section that would record the sequence of depo- sitional environments and subsidence history of this thick carbonate platform, including the timing of platform drowing and the installation of pelagic conditions. The results of drilling here bear strongly on the early evolution of the deeply buried conjugate margin on the North American side.