ASSESSING EOLIAN INFLUX TO AN ARID MIDDLE PENNSYLVANIAN CARBONATE RAMP, KANANASKIS FORMATION, ALBERTA: IMPLICATIONS FOR CLIMATIC INFLUENCES ON GLACIAL CYCLES

The Kananaskis Formation of the Western Canada Sedimentary Basin is Moscovian (Middle Pennsylvanian) in age, and consists of a cyclic mixed carbonate-siliciclastic succession, deposited on a ramp at a subtropical (25-30°) paleolatitude of northwestern Pangea. This investigation focuses on a 33 m section exposed within the Kananaskis Valley (southwestern Alberta). Three cycles occur, averaging ~10 m each and typically defined by three primary lithofacies (base to top): (1) thin, dark clastic mudstone with local nautiloids (2) silty dolomitic mudstone, and (3) well-sorted dolomitic sandstone with rare trough and common planar stratification. The latter two facies are unfossiliferous. The thin basal mudstone is inferred to record the deepest water facies, whereas the dolomitic carbonate mudstone and dolomitic sandstone are inferred to record probable shoreface to foreshore environments in a restricted shallow ramp setting. These cycles are interpreted as glacioeustatic in origin, associated with the glacial-interglacial cycles of the late Paleozoic. In addition to changes in deposition induced by eustasy, the nature and style of clastic sediment input recorded in each cycle may reflect glacial-interglacial climate fluctuations. We are testing the hypothesis that the clastic detritus within these cycles records eolian input caused by changes in aridity, as the carbonate ramp formed isolated from fluviodeltaic feeders. We are addressing this partly through analysis of the amount and grain size of the silicate mineral fraction (detrital residue), conducted on a decimeter scale through the cycles, coupled with geochemical analysis to infer provenance of the clastic detritus. Preliminary results indicate that clastic content and grain size increase toward the tops of each cycle. The results of this study will aid efforts to better understand possible arid-climate cycles.