A lacustrine paleoenvironment recorded at Vera Rubin ridge, Gale crater:
Overview of the sedimentology and stratigraphy observed by the Mars
Science Laboratory Curiosity rover
Abstract
For ~ 500 sols, the Mars Science Laboratory team
explored Vera Rubin ridge (VRR), a topographic feature on the northwest
slope of Aeolis Mons. Here we review the sedimentary facies and
stratigraphy observed during sols 1800-2300, covering more than 100 m of
stratigraphic thickness. Curiosity’s traverse includes two transects
across the ridge, which enables studies of lateral variability over a
distance of ~ 300 m. Three informally named
stratigraphic members of the Murray formation are described: Blunts
Point, Pettegrove Point, and Jura, with the latter two forming the
ridge. The Blunts Point member, exposed just below the ridge, is
characterized by a recessive, fine-grained facies that exhibits
extensive planar lamination and is crosscut by abundant curviplanar
veins. The Pettegrove Point member is more resistant, fine-grained,
thinly planar laminated, and contains a higher abundance of diagenetic
concretions. Conformable above the Pettegrove Point member is the Jura
member, which is also fine-grained and parallel stratified, but is
marked by a distinct step in topography which coincides with meter-scale
inclined strata, a thinly and thickly laminated facies, and occasional
crystal molds. All members record low-energy lacustrine deposition,
consistent with prior observations of the Murray formation. Uncommon
outcrops of low-angle stratification suggest possible subaqueous
currents, and steeply inclined beds may be the result of slumping.
Collectively, the rocks exposed at VRR provide additional evidence for a
long-lived lacustrine environment (in excess of 10^6 years via
comparison to terrestrial records of sedimentation), which extends our
understanding of the duration of habitable conditions in Gale crater.