Paper No. 256-9
Presentation Time: 3:50 PM
DEPOSITIONAL BUILD-AND-FILL WITHIN THE ZARAH SUBGROUP (UPPER PENNSYLVANIAN, MISSOURIAN STAGE) OF MIAMI COUNTY, KANSAS: INTEGRATED LITHOSTRATIGRAPHY, BIOSTRATIGRAPHY, δ13CCARB CHEMOSTRATIGRAPHY, AND GEOPHYSICAL WELL-LOG DATA
Surface and subsurface analysis of units within the Zarah Subgroup of Miami County reveal extensive distal-delta lobe development with variable thicknesses up to 16.5 meters of the Liberty Memorial Shale Formation, and 17.1 meters and 31.7 meters respectively of the Island Creek and middle Farley shale members. The relief developed by these near-shore deposits promoted the aggradation and progradation of photic-zone algal mounds with thicknesses of greater than 14.6 meters on and around bathymetric highs, resulting in a dynamic interplay between carbonate build-up, and siliciclastic infilling, modulated by glacioeustatic sea level rise and fall. This dynamic system has been described as “build-and-fill” and is applied to the Zarah Subgroup as a means of predicting algal mound development and distribution. This high-resolution study is presented here in a sequence-stratigraphic framework, and improves upon past interpretations of the mound-bank paleotopography and our understanding of the Missourian depositional systems within the study area. This study also provides the first whole-rock carbonate carbon isotope δ13Ccarb chemostratigraphic data from Missourian rocks in this region, which show elevated δ13C values in association with carbonate and core shale lithologies with shifts of up to +6.0‰ (total change) for δ13C. These data show a similar pattern to that observed in the Permian of south-central Kansas, and has been attributed to glacial-interglacial cyclicity during the Late Paleozoic Ice Age. This study also provides updated conodont biostratigraphic information for the Kansas City Group.