Abstract
Numerous graben features transect the Tempe Terra plateau in the northeastern Tharsis Rise, Mars, making it one of the most heavily structured regions of Tharsis. The origin of the complex fault geometries, generated over three distinct stages of tectonic activity, is poorly understood. This work distinguishes between Tempe Terra structures of local and regional origin, to isolate regional deformation patterns related to the general development of the Tharsis Rise from the patterns due to effects of local stress mechanisms. Comparison of structural observations to predicted deformation patterns from different drivers of graben formation in the Martian crust demonstrates the important role of magmatic activity at a variety of scales in driving tectonism in Tempe Terra. Noachian (Stage 1) faulting resulted from local magmatic underplating and associated heating and uplift, which formed part of an incipient stage of widespread Tharsis volcanism that predated development of the main Tharsis Rise. Early Hesperian (Stage 2) faults reflect the interaction of regional stresses from growth of Tharsis with magmatic activity highly localized along the Tharsis Montes Axial Trend—a linear volcanotectonic trendline including the alignment of the Tharsis Montes volcanoes. Early–Late Hesperian (Stage 3) faulting resulted from a series of dyke swarms from a Tharsis-centered plume, which propagated in a regional stress field generated by growth of the Tharsis Rise. As only Stage 2 NNE faults and Stage 3 ENE faults are linked to regional, Tharsis-related stresses, other observed Tempe Terra fault trends can be excluded when evaluating models of Tharsis's tectonic evolution.
Key Points
The 3 stages of Tempe Terra's tectonic activity have different origins, with local and regional scale magmatic sources driving deformation
Magmatectonic activity began in Tempe Terra prior to development of the Tharsis Rise topographic bulge and associated major volcanoes
Only 2 Tempe Terra fault trends (NNE and ENE), both Hesperian age, represent stresses related to the growth of the Tharsis Rise
Plain Language Summary
Tharsis is the largest volcanic province on Mars and its formation was a major driver of the deformation we see at the surface. Tectonic structures that record this deformation are therefore used to understand how and when Tharsis formed. However, local structural patterns may obscure regional trends associated with Tharsis-forming stresses, complicating our ability to assess models for how Tharsis developed. As such, distinguishing between faults with local and regional origins is essential. We study the Tempe Terra region in northeastern Tharsis to determine the origin of the region's extensive faulting, generated over three stages of tectonic activity. By comparing surface observations to expected evidence of different sources of stress, such as uplift from local volcanoes or dyke intrusion, we found that each stage of tectonic activity had a different origin. A combination of local (from within Tempe Terra) and regional (from Tharsis) magmatic sources drove deformation, and tectonic activity began before the main structures and volcanoes of Tharsis had developed. Only two fault trends in Tempe Terra can be linked to regional stresses related to the growth of Tharsis: NNE-trending and ENE-trending faults. Isolating these regional trends provides clearer criteria for assessing models of Tharsis development in the future.
CORE (COnnecting REpositories)
CORE (COnnecting REpositories)