Stratigraphic expression of Middle and Late Cambrian sea-level changes: Examples from Antarctica and the Great Basin, United States of America

At least three episodes of eustatic fluctuation profoundly influenced sedimentation during Cambrian time: initial sea-level rise of the Sauk Sequence during the Early Cambrian, sea-level fall and subsequent rise during the Middle Cambrian Sauk I-Sauk II (Hawke Bay) event, and the Late Cambrian Sauk II-Sauk III sea-level fall and rise. This dissertation documents evidence for the Sauk I-Sauk II event on Antarctica and the Sauk II-Sauk III changes on North America.; In Antarctica, the Middle Cambrian Nelson Limestone records a rise of sea level that broadly coincides with the later part of the Sauk II transgression of North America. Three depositional sequences in the formation chronicle smaller scale sea-level fluctuations. The lower sequence is bounded below by angular unconformity, and upward, strata include as many as 72 m of terrigenous valley-fill, indicating that at least locally baselevel rose minimally 72 m prior to deposition of marine sediments.; In western North America, during the Sauk II-Sauk III interval, at least two eustatic falls, one during Prehousia chron and the other in early Elvinia chron can be documented. These falls exposed cratonic areas subaerially, and facilitated transport of fine-grained siliciclastic sediment onto the miogeoclinal carbonate platform. In the miogeoclinal record, these influxes of shale suppressed carbonate productivity, while rapid subsidence outstripped the rate of sea-level fall. Consequently, at these stratigraphic levels, strata show deepening that correlates with hiatus on the craton. One interval of subaerially exposed subtidal carbonates in the Wah Wah Mountains and southern House Range indicates relative sea-level fall during early Elvinia chron that seemingly is correlated with the Sauk II-Sauk III unconformity. The mechanisms that generated sea-level fluctuations remain unknown, but a shift from non-cyclic to cyclic sedimention during late Elvinia chron suggests that a transition from predominantly greenhouse to icehouse, glacial-interglacial, conditions may have occurred.