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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 67 (1983)

Issue: 3. (March)

First Page: 537

Last Page: 537

Title: A Synthesis of Marine Geological/Geophysical Data for Ocean Margin Drilling on Continental Margin of Morocco: ABSTRACT

Author(s): Philip D. Rabinowitz, Dennis E. Hayes, Karl Hinz

Article Type: Meeting abstract


The continental margin of Morocco represents the conjugate segment to the North American margin south of Nova Scotia. The total sedimentary cover in the continental margin province is considerably thinner off Morocco than it is off the east coast of North America. Further, selected portions of the Morocco continental margin have undergone major tectonics, either exposing or bringing near the surface older elements of the stratigraphic section. Thus, scientific objectives requiring sampling of the earliest drift phase sediments, the oldest oceanic crust, and the basement rocks in the ocean-continental transition zone can be more easily addressed off Morocco than off North America.

We have recently compiled a synthesis of marine geological/geophysical data for the offshore regions bordering the continental margin of Morocco. The synthesis was undertaken in order to evaluate future scientific deep-sea drill sites. The final product of the synthesis is a set of maps on Mercator projection for the area 29° to 35°N, 5° to 22°W. The maps include: bathymetry contours, free-air gravity anomaly contours, total intensity magnetic anomalies plotted normal to the ship's tracks, seismic velocity crustal structure, reflection time to basement, blue reflector (upper Jurassic) and red reflector (upper Cretaceous), isopach (in seconds of two-way reflection time) of sea floor to basement, sea floor to blue reflector, sea floor to red reflector, and blue refle tor to red reflector, locations of surface sediment samples, hazards, and tectonics. In addition, seismic crustal sections from the nearshore across the disturbed piercement structure province to the deep ocean floor have been compiled.

Our synthesis reveals that the continental margin of Morocco consists of several unique segments. A dominant structural unit is the NNE-SSW-trending zone of salt diapirs and piercement structures observed on the continental shelf and slope. The salt is presumed to be of Late Triassic to Early Jurassic age. A prominent magnetic anomaly which may represent a magnetic edge effect anomaly can be traced along most of the western boundary of the Moroccan diapiric zone. On the conjugate continental margin south of Nova Scotia, a diapir zone is also observed. The seaward edges of the Moroccan and eastern North American diapiric zones match very well in pre-drift reconstructions, thus suggesting that before the separation of the African and North American plates a single evaporite basin existe . The magnetic and seismic data suggest that the seaward boundaries of the piercement fields mark the likely boundary between oceanic and continental basement.

The westernmost portion of the synthesis area is characterized by the well-defined Mesozoic sequence of magnetic anomalies from M0 (^cong 108 m.y.B.P.) to M25 (^cong 152 m.y.B.P.). These anomalies are situated on seismically observed oceanic crust formed by sea-floor-spreading processes. Between the seaward edge of the diapiric zone and magnetic anomaly M25 we observe a broad structural arch beneath which our single-channel seismic records in general fail to resolve the underlying basement. This is the region of the Jurassic magnetic quiet zone.

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Copyright 1997 American Association of Petroleum Geologists