Proposed Origin of the Burns Formation (Meridiani Planum, Mars) by Erosion, Reworking, and Diagenetic Alteration of a Grasberg-like Precursor
Journal Article
; The sulfate-rich sandstones of the Burns formation investigated by the; Opportunity rover on Meridiani Planum, Mars, are directly underlain by; the fine-grained sedimentary rocks of the Grasberg formation. It was; recently shown that, except for differing amounts of MgO and; SO; 3; , the Burns and Grasberg rocks have nearly identical; chemical compositions, suggesting both units are genetically related.; Here, quantitative models demonstrate that the chemical composition of; the Burns formation can be accurately reproduced by addition of MgO and; SO; 3; to a Grasberg-like precursor, along with small; amounts of Ni. Based on this result, a new scenario is proposed for the; origin of the Burns formation: (1) deposition of fine-grained airfall; deposits with composition similar to the Grasberg rocks; (2) induration; of the deposits, resulting in materials that closely resemble the; current Grasberg formation in composition and texture; (3) erosion into; sand-sized particles, which are then reworked by eolian and fluvial; processes to form the bedding features observed in the Burns rocks; (4); infiltration of the deposits by one or more generations of groundwater,; resulting in diagenetic alteration that included local element; redistribution, dissolution/recrystallization of minerals, cementation,; and formation of hematite spherules; (5) evaporation of groundwater at; some point during diagenesis enriched the Burns sediments in MgO and; SO; 3; , with greater amounts accumulated closer to the; surface. This scenario fully accounts for the chemical composition of; the Burns sandstones as well as their sedimentary and diagenetic; features, while invoking only a known sediment source and; sedimentary/diagenetic processes widely observed on Mars.;
