Layered mantling deposits in northeast Arabia Terra, Mars: Noachian‐Hesperian sedimentation, erosion, and terrain inversion

Abstract

[1] Thick, layered mantling deposits of different ages occur in several nonpolar regions of Mars and are thought to represent volcanic ash and/or climate-related ice-dust deposition. One such deposit is a layered mantling unit that unconformably blanketed highlands terrain in northeast Arabia Terra during the Late Noachian and/or earliest Hesperian. Shortly thereafter, by the mid-Hesperian, this deposit was substantially eroded; on the basis of its superposed crater population, it appears to have subsequently retained its approximate morphology and distribution in the $3.5 Gyr since. When the erosion occurred, in the Early Hesperian, the mantling unit was more resistant in some areas than its surroundings, resulting in inversion of relief: craters were transformed into highstanding buttes, and valleys were transformed into isolated ridges. On the basis of the scale of the observed inversion of relief, the magnitude of erosion in northeast Arabia Terra was substantial, up to hundreds of meters. We have used newly available data to assess the nature of the mantling material and probable mechanisms for its deposition and removal. We find that (1) the mantle unit is layered at scales of meters to tens of meters; (2) the deposit has a median thickness of $60 m, and the thickness of the deposit was locally controlled by the topography at the time of its deposition; (3) the mantling unit thins toward the south; and (4) characteristics of the mantling unit, such as its induration, as well as observed pits and fractures, suggest that volatiles may have been incorporated into the mantling unit either during or following its emplacement. Taken together, our observations lead us to favor models for the deposition of the mantling unit involving airfall of dust or ash. Either climate-driven dust deposition or plinian volcanic eruptions from the nearby Syrtis Major volcanic province are plausible candidate models for the emplacement of the unit in time and space.

Friable Layered Deposits

“…4), exhumed and ▶ inverted craters, and ▶ inverted valleys (Schultz and Lutz 1988;Fassett and Head 2007;Zabrusky et al 2012). In some areas, the friable layered deposits appear to have been preferentially deposited or preserved in preexisting depressions such as crater floors (Fassett and Head 2007). Outliers of the friable layered deposits suggest that deposits were once covering a much larger region (Schultz and Lutz 1988;Harrison et al 2010).…”

“…Additional landforms found in association with friable layered deposits are exposed ▶ pedestal craters (Fig. 4), exhumed and ▶ inverted craters, and ▶ inverted valleys (Schultz and Lutz 1988;Fassett and Head 2007;Zabrusky et al 2012). In some areas, the friable layered deposits appear to have been preferentially deposited or preserved in preexisting depressions such as crater floors (Fassett and Head 2007).…”

“…Meter-scale layering (e.g., Fassett and Head 2007;Fig. 3a) is exposed in some, but not all, friable layered deposit outcrops.…”

Preservation of Late Amazonian Mars ice and water-related deposits in a unique crater environment in Noachis Terra: Age relationships between lobate debris tongues and gullies

“…If volatiles were present within the sedimentary unit, as has been suggested for similar deposits in other martian craters (e.g. Schultz and Lutz, 1988;Fassett and Head, 2007), the release of these volatiles could have accounted for the loss of material required to form the valleys systems and central depression as suggested by Schultz and Glicken (1979). Slumping, and rock falls along the edge of the valley flanks would over time cause a widening of the valleys, and appears to be continuing into the present.…”

Identifying Evidence for Explosive Volcanism on Mars Through Geomorphologic and Thermophysical Observations

“…Other studies suggest the source of these layered deposits may originate from explosive volcanism, such as volcanic ash fall (e.g., Fassett & Head, 2007;Hynek et al, 2003;Michalski & Bleacher, 2013;Moore, 1990;Scott & Tanaka, 1986). Of these works, Michalski and Bleacher (2013) suggest the source of the layered deposits resulted from explosive volcanic calderas within the Arabia Terra region (Figure 3.2).…”