A STRUCTURAL AND GEOLOGIC HISTORY OF BATHYS PLANUM, MARS, INCLUDING POSSIBLE PRE-THARSIS TECTONISM

Preliminary geologic and paleotectonic mapping at a 1:1M scale has been completed using Esri’s ArcGIS Pro. The map area, unofficially known as Bathys Planum, is located between 240° - 250° E, 29° - 40° S. CTX and HRSC are overlaid and coregistered onto a THEMIS daytime IR mosaic basemap for context. This mapping investigation has produced several observations discussed below.

This map region appears to contain evidence of basement structural control, which influences the formation and morphology of younger, Tharsis-associated graben; i.e., older structures control the formation of younger structures at their intersections. For example, in many locations within Bathys Planum, the younger Tharsis-associated graben take a zig-zag pattern as they intersect the more ancient pre-Tharsis basement structures. A high concentration of these fractures exhibit a curvilinear pattern concentric about a locality in the south-central portion of the map region. This pattern may mark the surface expression of an unexposed igneous intrusion, possibly representing a tectonic center preceding Tharsis-driven tectonism.

Other notable geologic activity includes the development of large promontories, scattered throughout the region. These very large, distinct mountains have been interpreted to be volcanic in origin, and may represent pre-Tharsis volcanism. One large mountain, in particular, contains several large and deep collapse pits, possibly calderas. Some of these pits are relatively pristine with very little infill, suggesting relatively recent geologic activity (Hesperian/Amazonian).

Some of the more intriguing observations for this region are the landscapes that indicate terrain softening, differential erosion, and possible magma-water-ice interactions. An example of the latter is a candidate Martian tuya (38°36'17.29"S, 119°16'58.43"W) which compares with an Icelandic tuya (64°47'7.11"N, 17°12'20.17"W). Such features suggest long-term, water-ice enrichment as well as the emplacement of lavas into ice (e.g., glaciers, ablating ice cores, frozen seas or lakes).