Widespread loess-like deposit in the Martian northern lowlands identifies Middle Amazonian climate change
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Abstract
Consistently mappable units critical to distinguishing the style and interplay of geologic processes through time are sparse in the Martian lowlands. This study identifies a previously unmapped Middle Amazonian (ca. 1 Ga) unit (Middle Amazonian lowland unit, mAl) that postdates the Late Hesperian and Early Amazonian lowland plains by >2 b.y. The unit is regionally defined by subtle marginal scarps and slopes, has a mean thickness of 32 m, and extends >3.1 × 106 km2 between lat 35°N and 80°N. Pedestal-type craterforms and nested, arcuate ridges (thumbprint terrain) tend to occur adjacent to unit mAl outcrops, suggesting that current outcrops are vestiges of a more extensive deposit that previously covered ∼16 × 106 km2. Exposed layers, surface pits, and the draping of subjacent landforms allude to a sedimentary origin, perhaps as a loess-like deposit emplaced rhythmically through atmospheric fallout. We propose that unit mAl accumulated coevally with, and at the expense of, the erosion of the north polar basal units, identifying a major episode of Middle Amazonian climate-driven sedimentation in the lowlands. This work links ancient sedimentary processes to climate change that occurred well before those implied by current orbital and spin axis models.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Widespread loess-like deposit in the Martian northern lowlands identifies Middle Amazonian climate change |
| Series title | Geology |
| DOI | 10.1130/G33513.1 |
| Volume | 40 |
| Issue | 12 |
| Year Published | 2014 |
| Language | English |
| Publisher | Geological Society of America |
| Contributing office(s) | Astrogeology Science Center |
| Description | 4 p. |
| First page | 1127 |
| Last page | 1130 |
| Online Only (Y/N) | N |
| Additional Online Files (Y/N) | N |
| Google Analytic Metrics | Metrics page |