Lower Silurian conodonts from the Shine Jinst region, southwestern Mongolia

Abstract

Lower Silurian conodonts were recovered from carbonate beds in the upper Zalaa and lower Sharchuluut formations at Yamaan Us in the Shine Jinst region, Gobi-Altai Zone, of southwestern Mongolia. Conodonts are described from the Zalaa Formation for the first time; key taxa recovered include Distomodus kentuckyensis Branson, 1947, Ozarkodina hassi (Pollock, Rexroad, and, Pranognathus siluricus , and Pseudolonchodina expansa (Armstrong, 1990). These species constrain the onset of the Silurian carbonate platform, upper Zalaa to lower Sharchuluut formations, to the Pranognathus tenuis Zone, middle Aeronian. The presence of a cosmopolitan conodont fauna places these strata from the Gobi-Altai Zone in a basin-shelf marine setting with connection and circulation to the open ocean during the Llandovery.

Continuous record of Upper Ordovician (Katian) to lower Silurian (Telychian) global δ13C excursions in the Williston Basin

“…pirata, and the upper Guernsey Fm. has a sparse fauna indicative of the Psuedolonchodina expansa-D. staurognathoides zones that includes Psuedolonchodina expansa, which ranges from the uppermostRhuddanian to the mid-Telychian(Danielsen & Over, 2016). The sparse fauna prevents a higher resolution zone assignment within the most recent Silurian global conodont zonal scheme(Melchin et al, 2020).…”