Abstract
AbstractOn Mars, basins formed by tectonic processes are rare and mostly have unconstrained subsidence histories. One method for understanding this record of subsidence is through associated alluvial fans, which are sourced from uplifted areas and accumulate in downthrown basins. The source, morphology, and superposition of fan deposits can be used to reconstruct fault kinematics, the relative timing of accommodation space formation, and, in turn, the influence tectonic processes had on Martian fan formation. Here we use high-resolution orbital data sets to characterize sediment fan deposits associated with syn-tectonic sedimentation in two regions of the Valles Marineris canyons: Coprates Chasma and Juventae Chasma. These deposits comprise sediment fans on the current canyon floor and low-gradient surfaces perched several kilometers above the canyon floor. We interpret the low-gradient surfaces as remnant sediment fan deposits, which originally formed at the former canyon floor and have since been offset due to normal faulting. The preservation of vertically offset generations of sediment fan deposits supports a progressive, basinward migration of fault activity into the original hanging wall or repeat activity along a fault zone. Each episode of faulting was followed by a basinward shift in drainages, which led to fault-scarp degradation and formation of a new generation of fans. Multiple episodes of syn-tectonic sedimentation occurred during the evolution of the basins, with fluvial activity sporadically active. Our results demonstrate, for the first time on Mars, that depositional cyclicity was linked to tectonic deformation, possibly representative of regional processes throughout Valles Marineris.
Highlights
Alluvial fans are abundant on Mars, and most are considered to postdate the period of global fluvial activity at the Noachian-Hesperian boundary (3.7 Ga; Fassett and Head, 2008), instead forming later during the drier Hesperian and Amazonian eras (
Alluvial fans in Valles Marineris, which may have been deposited into active tectonic basins, provide an ideal location for exploring the role of tectonic processes on Martian fan formation and the relative timing of syn-depositional fault activity
We document the impact of faulting on alluvial fan systems at two sites in Valles Marineris, southeastern Coprates Chasma and Juventae Chasma, focusing on the relative timing of sedimentation and normal faulting
Summary
Alluvial fans are abundant on Mars, and most are considered to postdate the period of global fluvial activity at the Noachian-Hesperian boundary (3.7 Ga; Fassett and Head, 2008), instead forming later during the drier Hesperian and Amazonian eras (
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