GSA Connects 2022 meeting in Denver, Colorado

Paper No. 191-6
Presentation Time: 2:50 PM


LOUGHNEY, Katharine and HOLLAND, Steven M., Department of Geology, University of Georgia, 210 Field Street, Athens, GA 30602

As a common tectonic setting for nonmarine systems, extensional basins preserve extensive fossil records. Although individual basins may have complex histories, extensional basins tend to display similar trends in accommodation and sedimentation that make facies development predictable. Despite these similarities, spatial variations in accommodation and sedimentation across extensional basins mean that footwall and hangingwall stratigraphy should differ, causing their facies stacking patterns to be out of phase. Biotic trends and fossil preservation are therefore predicted to differ greatly across extensional basins, hindering stratigraphic and biostratigraphic correlations. Using basin simulations in R, we evaluated how temporal and spatial changes in accommodation and sedimentation influence the distribution of high- and low- accommodation systems tracts (HAST, LAST), biotic trends, and the preservation of the fossil record of nonmarine extensional basins. Simulations included cases of constant, increasing, and decreasing accommodation and sedimentation, and combinations thereof.

Trends in architecture, species diversity, and elevation in relation to accommodation emerge across the basin simulations. Footwall architecture is overall HAST-like, whereas hangingwall architecture is LAST-like updip, becoming increasingly HAST-like downdip. Species diversity and occurrences also decrease downdip (with decreasing accommodation) on the footwall and increase downdip (with increasing accommodation) on the hangingwall. Overall diversity of the footwall is nearly twice as high as hangingwall diversity, and footwall occurrences are four times greater than hangingwall occurrences. Accommodation and sedimentation are linked to elevation trends in basin simulations, which likely contribute to spatial differences in diversity. On the footwall, elevation represented in stratigraphic columns tends to decrease with time, whereas on the hangingwall, elevation increases with time. The total span of elevations preserved in footwall records is greater than the hangingwall and may contribute to higher species diversity on the footwall.