Widespread loess-like deposit in the Martian northern lowlands identifies Middle Amazonian climate change

Geology
By: , and 

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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.

Additional publication details

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