TERMINAL EDIACARAN MICROFOSSILS FROM THE UPPER HUQF SUPERGROUP IN OMAN

The Huqf Supergroup in the Sultanate of Oman is one of the best preserved and most continuous successions of the upper Neoproterozoic to lower Cambrian. It consists of, in stratigraphically ascending order, the Abu Mahara, Nafun, and Ara groups. The Huqf Supergroup was deposited between ~720 and 520 Ma. Geochronometric data indicate that the Ediacaran-Cambrian boundary lies in the Ara Group. Previous studies have recovered terminal Ediacaran shelly fossils Cloudina and Namacalathus from shallow-water carbonate facies of the Ara Group. However, there have yet to be any reports of microfossils from deep-water sediment, hampering our understanding of biostratigraphic correlation between different facies of the upper Huqf Supergroup and paleoecological distribution of terminal Ediacaran organisms in Oman. To fill this knowledge gap, we sampled a black chert unit of the lower Fara Formation for paleontological analysis. The samples were taken from Wadi Bani Awf in the Jabal Akhdar region in northern Oman. The sampled unit is interpreted to have been deposited in a deep-water offshore environment, sits below a volcaniclastic unit dated at 547.23±0.28/0.36/0.96 Ma, and is correlated with either the uppermost Nafun Group or the lowest Ara Group. Fifty-two thin sections have been prepared from these samples. The thin sections were examined under a transmitted light microscope and microfossils were photographed and then analyzed using the software ImageJ for morphological quantification. The microfossil assemblage of the lower Fara Formation is depauperate in diversity, consisting of simple forms (such as Cyanonema, Oscillatoriopsis, Obruchevella, and Siphonophycus) that are conventionally interpreted as cyanobacterial filaments, as well as rare spheroidal and coccoidal microfossils. Overall, the lower Fara microfossil assemblage is consistent with a terminal Ediacaran age. Future research should focus on resolving the provenance of the Fara filamentous cyanobacteria in order to determine whether they were planktonic organisms or transported from shallow waters, ultimately constraining the deep-water chert of the Fara Group was deposited in the photic zone.