LAMINATED MUDSTONES IN THE CLAY-SULFATE TRANSITION INTERVAL AT MT. SHARP -SIMILARITIES TO EVAPORITIC MUDSTONES FROM PAHRUMP HILLS AND POSSIBLE IMPLICATIONS
Résumé
Mudstone-rich lacustrine strata at Gale Crater, Mars, dominate the Mt. Sharp sedimentary succession. The Gale crater strata provide the oppor-tunity to test hypotheses regarding past climate shifts early in the planets history [1, 2], a key motivator for selecting Gale Crater as a landing site for the Curiosity rover.
At the base of the Mt. Sharp succession, at Pahrump Hills, mudstones with sedimentary features and geo-chemical attributes occur that suggest that these rocks accumulated in an underfilled lake basin. Lake waters were saline to hypersaline, and lake levels, shorelines, and salinities fluctuated greatly at various temporal scales [3, 4, 5].
Laminated mudstones, characterized by alternating softer and harder (cemented) layers and apparent evaporite pseudomorphs [4, 5] associated with the lat-ter, dominate the Pahrump succession. They show multiple textural similarities to evaporitic lacustrine strata on Earth [3]. Although indications of evaporitic conditions have been reported from higher in the sec-tion [6], laminated evaporitic mudstones of the type seen at Pahrump Hills were not been observed for the next 400 m of Mt. Sharp stratigraphy since leaving Pahrump Hills.
During the recent ascent from the clay trough to-wards the Sulfate bearing unit, rocks resembling the Pahrump Hills evaporitic mudstones were again en-countered at elevations above -4030 m. Examples of these laminated mudstones are compared to textural equivalents from Pahrump Hills.
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