281-5 Searching for Mars’s Ancient Tephra: Alteration Mineral Sequences as a Window into Pre-Amazonian Volcanism

Session: Petrology, Volcanology, and Mantle Plumes across the Solar System, Part II

Presenting Author:

Authors:

Abstract:

Studies of alteration minerals on Mars have provided key insights into its climatic and atmospheric evolution. These minerals are also commonly present in volcanic terrains on Earth, enabling connections between volcanic eruption styles and resulting mineral diversity.

Several locations throughout Arabia Terra, Mars, including the Mawrth Vallis region, contain clay minerals that are either constant with or diagnostic of a volcanic tephra protolith. Clay bearing deposits range in thickness from 200 m to just over a kilometer. Localized alterations of hydrated sulfates also exist among the clay bearing deposits. Analysis of data from the Mars reconnaissance orbiter (MRO), specifically a combination CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) data, HiRISE (High Resolution Imaging Science Experiment), and CTX (Context Camera), was used identify and characterize several individual observations of layered deposits exposed in cliff faces. We will discuss work to identify regional trends observed in clay and other hydrated mineral deposits, along with several emplacement hypothesis our team is considering, including emplacement by caldera forming eruptions.

Valles Marineris likely contains a stratigraphic record that includes alteration products of eruption material from the Tharsis volcanic province e.g. clays and hydrated sulfates). The Tharsis volcanic province is dominated by effusive volcanic landforms typified by innumerable lava flows, lava channels, and large shield volcanoes. Evidence of explosive volcanism has also been observed at the summit of large shields, west of Tharsis as the Medusa Fossae Formation, and within Valles Marineris. With higher resolution data from CTX, HiRISE, and CRISM, it is now possible to probe exposures within the walls of Valles Marineris for layered deposits of altered minerals that may represent explosive volcanic deposits. The stratigraphic relationship of such deposits with respect to effusive deposits provide a relative geologic sequence for the Tharsis volcanic province and evidence for the relative importance of effusive vs explosive styles of eruption over the history of the region. Furthermore, spatial variability in deposit thickness and/or composition may point to a particular source region within Tharsis or, potentially, multiple sources. Understanding the relative abundances of effusive vs explosive deposits over time within Valles Marineris provides constraints on the early volcanic history of Mars and the expected range of resulting compositions. We will discuss preliminary findings from this work.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-7253

© Copyright 2025 The Geological Society of America (GSA), all rights reserved.