Resultant Deformation of Sediments from Possible Seismic Events in the Pampa de Tepuel Formation during the Carboniferous (Patagonia, Argentina).

MCNALL, NATALIE, B.; ISBELL, JOHN; IVES, ELIZABETH; PAGANI MARÍA A; TABOADA, ARTURO CÉSAR

Esquel

Simposio; VII Simposio del Paleozoico Superior de Argentina; 2018

Deformation and deposition of sedimentary materials resulting from seismicity remainpoorly understood despite their importance in identifying areas and times of intense tectonicactivity in and adjacent to sedimentary basins. Such strata are often misidentified as the result ofrapid deposition, and in a polar environment, could be misidentified as a result of glacialtectonism. Therefore, identification of deformational structures is essential in making accuratedeterminations of seismic events. Direct objectives of this study are to continue determiningmacroscopic deformation features characteristics that resulted from earthquake inducedliquefaction of sedimentary deposits, thus furthering our understanding of when and whereseismic activity occurred in deep time. The Pampa de Tepuel Formation in Tepuel-Genoa Basin(Patagonia, Argentina), of Carboniferous age strata, is composed of fine-grained shelf sandstoneand mudrocks deposited on a marine shelf-slope edge. The section contains mass transportdeposits and an abundance of m-scale deformation structures. The mass transport depositsinclude slides and slumps of shelf sands that slid down the basin slope away from the shelfedge. Contained within these deposits, and within deposits on the shelf, are abundant loadstructures and dewatering features (pipes, sheets, and diapirs) of various sizes which aresuggestive of liquefaction and deformation of sediment before lithification, and before they sliddown the slope away from the shelf edge. Comparisons of these features to strata fromMississippian age deposits in Kentucky, U.S.A. that were previously interpreted as seismitessuggest that seismic activity may have influenced the sedimentation in the Pampa de TepuelFormation.Sedimentology