UTILIZING REMOTE GEOLOGIC MAPPING TO ANALYZE STRATIGRAPHIC VARIATION IN THE TRIASSIC ISCHIGUALASTO FORMATION, SAN JUAN PROVINCE, ARGENTINA

Recently developed software and high resolution imagery has made it increasingly possible to derive stratigraphic and structural information remotely. This study explores the viability of such application in the Triassic Ischigualasto basin of northwest Argentina. While much of the work on the Ischigualasto Formation has focused on its abundant paleontological content, other recent research has involved investigating the structural controls on fluvial-channel and overbank deposition and the morphology of paleosols preserved in this ancient continental rift basin. These studies have equated observed changes in fluvial channel/overbank architecture and paleosol morphology with spatial/temporal changes in rates of basin accommodation development due to structural controls (Currie et al., 2009; Colombi et al., 2017). Field observations in 2019 brought these interpretations into question; there was not enough stratigraphic information (i.e. stratigraphic unit thickness measurements) to determine the true controls on sediment deposition.

Using a geologic map created in ArcGIS and a 5m resolution Digital Surface Model (DSM), along-strike stratigraphic-thickness change within the NW trending Ischigualasto Formation was discerned using the Geologic Map Data Extractor (GMDE) computer application (Allmendinger, 2020). Twenty three sections were measured across an along-strike distance of 50 km. Thicknesses increased from ~220 m in the southeast part of the study area to ~870 m in the northwest. These results are similar to published sections from the same area and are in accord with previous interpretations that the observed/calculated stratigraphic thickness changes in the Ischigualasto Formation were primarily controlled by along-strike increases in displacement on the basin-bounding Valle Fértil normal fault during the time of deposition. The methods used in this study can be applied globally to aid in field reconnaissance and computing unit thicknesses on a large scale.