Middle and Late Devonian paleogeography of the eastern Anti-Atlas (Morocco)

Jobst Wendt

doi:10.1007/s00531-021-02028-6

Abstract

The eastern Anti-Atlas of Morocco represents one of the most completely exposed and perfectly documented biostratigraphic records of the entire Devonian worldwide. Paleogeographically it is clearly differentiated into shallow basins, pelagic platforms, and land areas which are newly defined and illustrated, one from the top of the Middle Devonian, the other from the middle Famennian as two of the most characteristic intervals. The dominant paleogeographic feature is the T-shaped Tafilalt Platform which, in spite of common unconformities and hiatuses, provides the best-documented biostratigraphic record through the entire Devonian. The westernmost termination of this platform was emerged during most of the Devonian (and locally even earlier) and became only flooded again by the Tournaisian transgression. In contrast to previous interpretations, this area is considered as autochthonous. In the Mader Basin subsidence was up to one hundred times higher with respect to the adjacent platforms, but water depth during the Middle Devonian to middle Famennian interval generally remained above storm-wave base. Devonian rocks are only patchily and incompletely preserved on the Mader Platform, which can be considered as an intermittently flooded peninsula connected to the Lower Paleozoic farther west. The major paleotectonic element of the entire area is the Great Anti-Atlas Fault, a sinistral strike-slip fault, which sharply confines the above-mentioned realms in the south.

Highlights

The Anti-Atlas is an approximately 800 km long mountain range in southern Morocco which extends from the Algerian/Moroccan border in the east until the Atlantic Ocean in the west
Emphasis is laid on a critical evaluation of all available biostratigraphic and sedimentologic data to obtain the most reliable survey of the driving forces, which have essentially influenced the depositional pattern in the eastern Anti-Atlas
The southern margin of the Mader Basin is represented by the W–E striking Great Anti-Atlas Fault, which can be approximately located near the occurrence of three, small lower Givetian (Lower varcus Zone) crinoid mud mounds south of Jebel Zireg (Kaufmann 1998)

Summary

Introduction

The Anti-Atlas is an approximately 800 km long mountain range in southern Morocco which extends from the Algerian/Moroccan border in the east until the Atlantic Ocean in the west. The most fundamental work on the Devonian, was achieved by Henri Hollard (1922–1980) since the late 1950s He died too early to summarize the incredible amount of his observations in an overall outline of the Devonian sedimentary realms of which only a posthumous summary was published (Hollard 1981). Since an almost unmanageable amount of new biostratigraphic data has been accumulated, of which the reference list represents only an incomplete survey In this context, the very active working groups of R. For a better understanding of the paleogeographic outlines of the eastern Anti-Atlas during the Devonian, a rigorous consideration of sedimentologic nature is highly desirable for future prospective work in this area

Materials and methods

Conclusions