Middle Darriwilian Small Stromatolite Bioherms and Spheroids (Oncoids) From the Moyero River Section (Siberian Platform)

The article presents results of studies of the stromatolites from Middle Ordovician deposits of the Moyero River section (Siberian platform). It demonstrates that despite the growing dominance of skeletal metazoans against the backdrop of Great Ordovician Biodiversification Event (GOBE) in Siberian Platform reef systems, microbial communities remained integral components of reef formation from the Middle Ordovician onward. These communities functioned both as crucial auxiliary elements and as sole framework builders. Stromatolites are associated with bioherms dominated by skeletal metazoan reef-builders (Angarella sp., Moyeronia sp., tabulate coral, Cryptolichenaria miranda, and stromatoporoid, Priscastroma gemina). This indicates that in some parts of the platform, due to regional peculiarities, microbial communities not only retained their role in Middle Ordovician reef systems, but also formed bioherms without symbiosis with other reef builders. Microbial communities form two distinct stromatolite types: less numerous spheroidal forms (SS and SS-I) and more prevalent stromatolite bioherms (SS → LH). The persistence of microbial influence in this region is attributed to specific depositional environment conditions. Due to their morphology and diagenetic alterations, these stromatolites have a potential for hydrocarbon reservoir formation. The study highlights that while contemporary reef zones in the Ordovician of West Taimyr are prospective yet poorly understood reservoirs, the Moyero River organogenic build-ups serve as valuable geological models. Further research into their structure, texture, and genesis is essential to refine predictions for Ordovician reservoir distribution. These findings emphasize the need to consider stromatolites as significant targets in reservoir exploration.