CORRELATING THE SAUK II-III UNCONFORMITY AND ITS OFFSHORE CORRELATIVE CONFORMITY, GREAT BASIN, USA

The Sauk II-III sequence boundary has been known for decades but few investigations have focused on details of surfaces and depositional packages within this interval. The peak of Steptoean Positive Isotopic Carbon Event (SPICE event) roughly coincides with the Paibian Dunderburgia or lower Elvinia trilobite zones. The Dunderbugia zone unconformity is best defined from Wyoming, while the lower Elvinia zone unconformity, the focus of this study, is known from western Utah. The Elvinia zone unconformity is characterized as a disturbed carbonate interval in the Corset Spring Shale and Steamboat Pass shale in western Utah. This Elvinia zone unconformity can be traced throughout the House Range, indicating missing time in the rock record. It is characterized by paleokarst pockets with internal sediment fills, sediment-filled fractures, small faults, and offset erosional surfaces. This disrupted interval also features upright, dipping and overturned second-generation flat-pebble conglomerate clasts up to 45 cm in length, disturbed thrombolite beds, and a rare local hardground on a thrombolite. This interval is significant because it is near the peak of the SPICE event and the base of the Jiangshanian stage. A correlative conformable interval is present in the Dunderburg Shale of eastern Nevada. Gamma-ray profiles and samples for isotopic analysis were collected from measured and described stratigraphic sections that contain the unconformity as well as the interval of correlative conformity. These data can help us to understand differences between the deep and shallow-water sections as well as bring insights into the peak of the SPICE event and its relationship to the base of the Jiangshanian stage.