Geochemistry of the early Cambrian succession in the western Anti-Atlas, Morocco: implications on provenance and paleoredox conditions

The Igoudine and Amouslek formations (Terreneuvian-Cambrian Epoch 2 boundary) in the western Anti-Atlas of Morocco record the replacement of stromatolite-dominated microbial consortia by thrombolite-metazoan consortia. Carbonate and calcareous shales of both forma -tions have been analyzed for major, trace, and rare earth elements to study their geochemical characteristics and evaluate the provenance of the terrigenous fraction and paleoredox conditions. Discrimination diagrams for the source rocks based on major elements and selected trace elements indicate that the terrigenous fractions of the sediments were likely derived from predominantly felsic rocks, and the source rocks have been identified to be the Paleo prote - rozoic-Neoproterozoic granites and metasediments of the Kerdous inlier. Paleoredox proxies such as U/Al, V/Al and Mo/Al suggest that the Igoudine and Amouslek formations were deposited in the oxic environment. Our data show that the local water column was prevailingly oxidized before, during and after the transition from the microbial consortium (stromatolite-dominated biota) to the thrombolite-archaeocyathan consortium and shelly metazoans within the studied interval. This implies that the seawater redox status was not driving this change in these biological communities.

Automated summary

The Igoudine and Amouslek formations in the western Anti-Atlas of Morocco provide insights into the replacement of microbial consortia and the paleoredox conditions during the Terreneuvian-Cambrian Epoch 2 boundary. Geochemical analysis suggests that the terrigenous fraction in these formations likely originated from felsic rocks and the sediments were deposited in an oxic environment. The transition from stromatolite-dominated biota to thrombolite-archaeocyathan consortium and shelly metazoans was not driven by seawater redox status.