Abstract
AbstractGorgonum Chaos is part of the Eridania paleolake in Terra Sirenum and displays a number of prominent light‐toned morphological features that bear a record of the regional climatic conditions throughout most of Martian history. Based on an intergrated analysis of orbital data, we mapped a 1,500 km2 area in the southeast of Gorgonum Chaos. Morphologic, spectroscopic, and stratigraphic analyses were used to determine age and composition of the main geological units in the area. We identified four major geological units with decreasing content of hydrated minerals from the oldest to the youngest units, which were completely free of hydrated minerals. In the study area, phyllosilicate‐rich Noachian units compose the majority of the basin floor. Deposits enriched with evaporites were formed around the Noachian/Hesperian transition and erosion created prominent inverted morphologies. Loess‐like material without significant amounts of hydrated minerals was deposited until the late Hesperian. The youngest unit is an Amazonian layer free of hydrated minerals that originated from volcanic activities. This succession of minerals reflects the transition from more humid climatic conditions with the ability to sustain liquid water on the planet's surface during the Noachian to the hyper‐arid Amazonian environment we observe currently on Mars.
Highlights
IntroductionA transition from humid to arid climates most likely has been accompanied by a shift from chemical alkaline and neutral, clay forming environments to acidic, sulfate forming conditions (e.g., Bibring et al, 2006; Chaves et al, 2018; Hurowitz et al, 2010; Kaplan et al, 2016; Peretyazhko et al, 2017)
We identified four major geological units with decreasing content of hydrated minerals from the oldest to the youngest units, which were completely free of hydrated minerals
The bowl-shaped morphology of Gorgonum Chaos (Wendt et al, 2013) with its generally flat surface indicates a uniform deposition of unit Late Noachian: Light-Toned Polygonized Unit (lNlp), which conforms with the slope of the basin floor
Summary
A transition from humid to arid climates most likely has been accompanied by a shift from chemical alkaline and neutral, clay forming environments to acidic, sulfate forming conditions (e.g., Bibring et al, 2006; Chaves et al, 2018; Hurowitz et al, 2010; Kaplan et al, 2016; Peretyazhko et al, 2017). This environmental transition should be reflected in the composition and in the stratigraphy of geological units.
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