New Mexico Geological Society Annual Spring Meeting — Abstracts

We catalogued the geomorphic attributes and general surface and subsurface characteristics of small-scale wet patches throughout central Wright Valley, Antarctica using a 100 m tape to measure the spatial dimensions of five discontinuous wet patches along the eastern third of the South Bull alluvial fan (77.515° S, 161.915° E) in December 2024. Measured wet patch lengths ranged from 17 m to 58 m and maximum patch widths ranged from just under 6 m to approximately 15 m. Wet patch area calculations were not performed due to the non-uniform lateral dimensions of each wet patch. Other discontinuous wet patches were visible along the fan and were visually deemed to be of similar dimensions to those catalogued here. Similarly, continuous water tracks were observed in the central and western portion of the South Bull alluvial fan, albeit not quantified for this study. All wet patches measured had similar albedos, darkening the sediment which they overprinted. Surface pavement size along this transect graded from sand-sized towards cobble-sized as one ascended nearer to the fan apex.

Additionally, pits ~10 cm in depth were dug near each of the wet patches studied; subsurface grain size within these pits varied from sand to coarse gravel. Subsurface moisture content was deemed to be comparable to surface moisture levels at a first-order level— those pits dug within areas visually dampened on the surface (i.e., dug within a wet patch) were similarly dampened in much of the near-subsurface, while those dug in drier portions of the fan away from wet patches had likewise drier subsurface sediment. Sediment samples were collected within each pit for future laboratory-based sediment and salt content analyses. Research into the degree to which these South Bull wet patches change spatially over both seasonal and annual timescales, as well as how their spatial extent, sedimentology, and subsurface moisture characteristics compare to other wet patches observed in-situ at the Doran (Taylor Valley), Denton (Wright Valley), and Harker (Victoria Valley) alluvial fans will further help to contextualize these polar desert surface features. Furthering this understanding of aqueous processes in an otherwise arid environment will likewise aid in the understanding of water resource management practices in dry climates, including in the desert southwest of the United States.