2015 GSA Annual Meeting in Baltimore, Maryland, USA (1-4 November 2015)

Paper No. 229-6
Presentation Time: 9:00 AM-6:30 PM


BROPHY, Shannon K.1, GARB, Matthew P.1, NAUJOKAITYTE, Jone1, ROVELLI, Remy1, BAYON, Richard1, LARINA, Ekaterina1 and LANDMAN, Neil H.2, (1)Earth and Environmental Sciences, Brooklyn College, 2900 Bedford Ave, Brooklyn, NY 11210, (2)Division of Paleontology, American Museum of Natural History, Central Park West at 79th St, New York, NY 10024, skbrophy94@aol.com

Evidence for the Cretaceous-Paleogene (K/Pg) bolide impact is present throughout exposures in west-central Alabama. Moscow Landing, (Merengo County Al), and Mussel Creek (Butler County Al), contain well exposed sections of Upper Cretaceous and Lower Paleogene strata. Both of these localities exhibit multiple channel cuts at the boundary which have previously been interpreted to represent either low stand or tsunami related deposits. At Moscow Landing, approximately 3 meters of Upper Maastrichtian Prairie Bluff Chalk (PBC) are exposed and unconformably overlain by the Danian Clayton Fm.. The PBC is a highly bioturbated, fossiliferous marly-chalk. There are multiple channel cuts at the base of the Clayton scoured into the underlying PBC chalk. These channels contain reworked, imbricated Cretaceous fossils, and rip ups from the underlying PBC that range in size from pebbles to boulders. Channel matrix consists of medium to coarse grained quartz sand. The base of the channels exhibit a sharp contact between the PBC and the Clayton sand beds. Sediment samples were taken from a 3m section from the top of the PBC up through the channel cuts at 10cm intervals. Sieving analysis shows a general fining up sequence with multiple rip up horizons, a comparable trend to modern day tsunami deposits. Mussel Creek is located approximately 95 miles southeast of Moscow Landing. As in Moscow Landing, the carbonate rich, highly bioturbated PBC is overlain by siliciclastic sand filled channel cuts of the basal Clayton Fm. Sediment samples were collected at 5cm intervals and sieved for sediment analysis. The channels are composed of micaceous, lignitic, quartz rich sand with twice as much mud content than Moscow Landing. Bedding features include parallel to low angle cross laminations. High concentrations of organic matter are evident. This suggests deposition in a low energy environment, most likely tidally influenced estuarine like environment. Based upon sedimentological evidence from both localities, channels at Moscow Landing appear to have been deposited during an extremely high energy event, most likely a tsunami following the bolide impact while channels at Mussel Creek likely represents a tidally influenced environment during early stages of a transgressive systems tract.