Cambrian deposition in northwestern Africa: Relationship of Tamlelt massif (Moroccan‒Algerian border region) succession to the Moroccan Meseta

Abstract

The Tamlelt massif is physiographically grouped as a continuation of the easternmost High Atlas. However, re-examination of the Tamlelt's Cambrian litho- and biostratigraphy shows a depositional history that differs from that of the Souss Basin to the southwest (i.e., west-central High Atlas and eastern Anti-Atlas of Morocco). Our re-examination leads to recommendations on the local stratigraphic succession and nomenclature. Trilobites from the Al Hamrat Formation in the Tamlelt massif indicate late early Cambrian (upper Epoch 2) siliciclastics overlying shallow marine, carbonate-rich deposits (Jbel Menhouhou Formation) similar to and coeval with those of the distant western Anti-Atlas region but older than and lithologically distinct from fluviatile siliciclastics (Epoch 3) in the nearby eastern Anti-Atlas. The Jbel Menhouhou carbonates unconformably overlie probable terminal Proterozoic volcanics and clastics of the Bou Kaïs Formation (new) and are overlain by shales and arenites of the upper Kheneg El Kahal Group, which features a Cambrian Stage 4 regressive half-cycle. Regional differences in lithofacies disappear in the early Miaolingian with relatively monotonous, mudstone-rich facies in the Tamlelt massif area (Batene El Jdari Formation) comparable to those of the Jbel Wawrmast Formation of the west-central High Atlas and central‒eastern Anti-Atlas. Probable early late Cambrian brachiopods from siliciclastic rocks of the Tamlelt area indicate a later Cambrian depositional history similar to that of the Anti-Atlas and perhaps Moroccan Meseta. The distinctiveness of the upper lower Cambrian deposits of the Souss Basin from those of the Tamlelt massif apparently reflects a depositional framework independent from other regions of the Atlas ranges, and suggests the Tamlelt region was confluent with the Meseta basin to the northwest. Known trilobites permit precise age assignments through the Tamlelt succession and include species (or forms) which contribute to a refined correlation within West Gondwana and improve West Gondwana‒Baltica correlation. The new trilobite species Saukianda? (Saukianda?) dresnayi is proposed.