Source-to-Sink

Abstract

Eolian dune fields on Earth and Mars evolve as complex systems within a set of boundary conditions. A source-to-sink comparison indicates that although differences exist in sediment production and transport, the systems largely converge at the dune-flow and pattern-development levels, but again differ in modes of accumulation and preservation. On Earth, where winds frequently exceed threshold speeds, dune fields are sourced primarily through deflation of subaqueous deposits as these sediments become available for transport. Limited weathering, widespread permafrost, and the lowdensity atmosphere on Mars imply that sediment production, sediment availability, and sand-transporting winds are all episodic. Possible sediment sources include relict sediments from the wetter Noachian; slow physical weathering in a cold, water-limited environment; and episodic sediment production associated with climatic cycles, outflow events, and impacts. Similarities in dune morphology, secondary airflow patterns over the dunes, and pattern evolution through dune interactions imply that dune stratification and bounding surfaces on Mars are comparable to those on Earth, an observation supported by outcrops of the Burns formation. The accumulation of eolian deposits occurs on Earth through the dynamics of dry, wet, and stabilizing eolian systems. Dry-system accumulation by flow deceleration into topographic basins has occurred throughout Martian history, whereas wetsystem accumulation with a rising capillary fringe is restricted to Noachian times. The greatest difference in accumulation occurs with stabilizing systems, as manifested by the north polar Planum Boreum cavi unit, where accumulation has occurred through stabilization by permafrost development. Preservation of eolian accumulations on Earth typically occurs by sediment burial within subsiding basins or a relative rise of the water table or sea level. Preservation on Mars, measured as the generation of a stratigraphic record and not time, has an Earth analog with infill of impact-created and other basins, but differs with the cavi unit, where preservation is by burial beneath layered ice with a climatic driver.

Planum Boreum basal unit topography, Mars: Irregularities and insights from SHARAD

“…As there exists correlation between a unique subsurface topography and modern topography, we hypothesize that the same wind-influenced parameters for ice deposition have been ongoing since the end of rupes unit erosion. This is supported by the extensive geological evidence for aeolian influence in the cavi [Herkenhoff et al, 2007;Kocurek and Ewing, 2012]. Further climate modeling, more sophisticated than the simple mesoscale simulation presented in this paper, will be needed to test this hypothesis.…”

Compositional Variations in Sands of the Bagnold Dunes at Gale Crater, Mars, From Visible-Shortwave Infrared Spectroscopy and Comparison to Ground-Truth From the Curiosity Rover

“…In addition to sorting, efficient surface weathering can select for the most prevalent and resistant minerals on Earth, such as quartz and potassium feldspar, which make up most of Earth's aeolian sandstones. On Mars, however, the formation of aeolian sand and the accumulation and preservation of aeolian sandstones is relatively poorly understood [e.g., Kocurek and Ewing, 2012], but our results suggest that primary variations of~7 wt % in SiO 2 and~20 wt % in FeO tot + MgO may arise over a length scale of a few kilometers only from sorting of basaltic sand and/or mixing well-sorted sand with local sediment sources. If the Bagnold Dunes of Gale crater are representative of the sediments forming aeolian sandstones on Mars, Martian aeolian sandstones may be more poorly sorted and compositionally diverse than terrestrial aeolian sandstones.…”

Sedimentary processes of the Bagnold Dunes: Implications for the eolian rock record of Mars

“…Stratification interpreted as eolian in origin has been identified in the rock records of Earth and Mars [e.g., Brookfield, 1977;Grotzinger et al, 2005;Herkenhoff et al, 2007;Grotzinger et al, 2015]. The ubiquity of eolian bed forms in the solar system highlights the robust selforganizing nature of the eolian surface sediment transport system within a wide range of planetary boundary conditions [Kocurek and Ewing, 2016a].…”