269-7 Preliminary Geologic Mapping of the Mahuea Tholus Quadrangle (V-49), Venus: Stratigraphic Relationships and Implications for Global Surface Evolution

Session: Planetary Geologic Mapping Across the Solar System (Posters)

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Abstract:

The Mahuea Tholus quadrangle (V-49) is a geologically significant unpublished area on Venus that hosts diverse tectonic structures, volcanic features, resurfacing units, and a rift zone. Geologic mapping using Magellan SAR data reveals a stratigraphically complex terrain southeast of the rift, characterized by overlapping radar-bright lava flows, tessera remnants, lineated plains, channels, coronae, and tectonic fabrics. This study examines the geologic history of V-49 to better situate it within global stratigraphic models and assess the role of regional versus global resurfacing processes.

The Mahuea Tholus volcanic center is characterized by a low-relief edifice surrounded by overlapping radar-bright flow lobes. These flows vary in texture and radar brightness, suggesting differences in composition, surface roughness, or flow inflation. The lack of associated lava channels and the morphologic similarity of some flows to inflated or evolved lava types suggest that Mahuea Tholus may represent a rare candidate for non-basaltic volcanism on Venus. Although recent work suggests the flows are mafic, the edifice and flows aren’t spatially linked to large-scale radial fractures, further supporting the interpretation of localized, potentially silica-rich eruptions. These flows uniformly embay older plains, and some earlier-emplaced flows are crosscut by wrinkle ridges, indicating episodic eruptions over time.

Two large patches of tessera terrain, Urd and Nortia Tesserae, are among the oldest units in the quadrangle. These exposures preserve a high degree of deformation, including folding, orthogonal fracture sets, and pervasive textural fabrics crosscut by younger material. The tesserae are partially embayed by multiple units, including regional plains, densely lineated plains, and small volcanic edifices and flows, indicating a complex and multi-stage resurfacing history. The presence of broad warping in the underlying terrain suggests an earlier phase of crustal deformation that either predates or formed contemporaneously with deformation of Urd Tessera. Post-tectonic overprinting includes regional NW-trending lineaments and wrinkle ridges. Relationships record a prolonged sequence of tectonic and volcanic events with no single dominant resurfacing phase.

These stratigraphic relationships are not easily reconciled with a globally synchronized resurfacing model, instead supporting a non-directional evolution model, in which resurfacing and deformation are spatially heterogeneous and temporally disjointed. Continued mapping will constrain the sequence and styles of volcanism, test hypotheses about evolved lava emplacement, and contribute to surface composition interpretations for radar and spectral datasets from upcoming missions.

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

doi: 10.1130/abs/2025AM-9789

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