INVESTIGATION OF LAMINATED PEORIA LOESS AS AN ANALOG FOR MARTIAN DUST DEPOSITION

Studies of the exposed rock record at Mount Sharp within Gale crater, Mars have led to multiple hypotheses about the ancient environments preserved there. In particular two lasting hypotheses, one including fluvio-lacustrine deposition and and another consisting largely of dry, aeolian deposition, first arose prior to landing from orbital observations and remain unresolved despite research performed on the surface with the Mars Science Laboratory (MSL) Curiosity rover. Both hypotheses are backed by independent studies of the environment at Mount Sharp. Addressing this important question is directly related to Curiosity’s mission goals and has large implications on the scope and longevity of potentially habitable environments that may have existed at Gale in the geologic past. Sedimentologically, the stratigraphy at Mount Sharp primarily consists of a fine-grained laminated facies. Although this facies is typically attributed to sediment fallout within a lacustrine setting, there are rare occurrences of laminated aeolian loess deposits in terrestrial settings. This fine-grained laminated loess facies, is potentially very important for interpreting the rock record on Mars, which is an inherently drier and dustier environment than Earth, both at Gale crater and elsewhere. We pursue these questions by exploring the occurrence of laminated terrestrial loess in the mid-continent United States as a potential analogue for Martian dust. This approach involved a field campaign to various outcrops of Quaternary Peoria Loess to further document the geographic extent of the planar laminated facies and collect epoxy peel samples that that preserve the weakly lithified stratification. With data primarily collected from the Bignell Hill and Moran Canyon exposures, we report on physical and sedimentological attributes leading to laminar deposition of loess and highlight potential factors leading to accumulation of laminar sediments, along with their relevance to Mars.