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• Overlapping crater populations constrain the total era of martian valley formation. • Martian valleys may have formed intermittently over hundreds of millions of years. • Long-term erosion rates would have been similar to the modern Atacama Desert. A number of studies have constrained the cessation of martian valley network activity to around the Noachian-Hesperian boundary, but the total time period over which these features formed remains poorly constrained. Most attempts to ascertain valley network formative timescales rely on an intermittency factor that varies widely for terrestrial rivers and is unknown for Mars. In this contribution, superposition relationships are used to identify crater populations that pre- and postdate valley network incision, resulting in maximum cumulative valley formation times of ∼108 years. These timescales correspond with long-term erosion rates of ∼0.25 m/Myr, similar to those calculated for the Middle to Late Noachian as well as the central Atacama Desert since the Late Miocene. Assuming sediment transport rates previously calculated for other martian valley networks, this implies a minimum fluvial intermittency of ∼10−5, several orders of magnitude lower than modern day Earth rivers but similar to values independently calculated for some martian fluvial deposits. This low intermittency suggests that martian valley incision may have been significantly hindered by erosion into existing bedrock or by boulder armoring of the valley floor. Alternatively, unlike river valleys on Earth, runoff events driving martian valley network activity may have been non-seasonal, Milankovitch-like cycles, with long eras of quiescence between periods of intensified fluvial activity. [ABSTRACT FROM AUTHOR]

This study examines the role of topography as a dynamic boundary condition that limits the efficiency of fluvial erosion in the post-glacial Teton Range landscape. The volume of sediment currently stored in two major catchments was estimated using high-resolution LiDAR and geometric reconstructions of depth to bedrock. Seismic reflection data in Moran Bay reveals post-glacial sediment preserved behind a submerged moraine, which isolates the bay from the larger Jackson Lake depocenter. The volume of post-glacial sediment stored in the canyons and bay totals 173.82 ± 19.5336.0 (×10−3 km3), which translates to a catchment-wide sediment production rate of 0.17 ± 0.02 mm/yr. The rock-equivalent sediment volume in Moran Bay is 4.4 ± 0.9 (×10−3 km3), only ∼2.6% of the total post-glacial volume. While the estimated sediment production rate in the canyons is similar to the uplift rate, the denudation rate derived from Moran Bay sediment is 0.004 ± 0.001 mm/yr, implying highly inefficient post-glacial sediment transport. The fluvial system has been disequilibrated by glacial erosion such that interglacial valley profiles lack the steepness needed to transport sediment, delaying sediment evacuation until the next glacial advance, or until uplift sufficiently steepens the fluvial system so that it regains efficiency. Furthermore, colluvial production rates in the deglaciated valleys are close to long-term denudation and uplift rates, suggesting that once topography has been equilibrated to glacial erosion processes, subsequent glaciers do not need to produce much bedrock erosion, but mainly sweep out accumulated sediment to maintain equilibrium. • Sediment budget quantified for two catchments in the Teton Range, Wyoming. • Flattened post-glacial topography limits efficient fluvial erosion. • Sediment transport delayed until next glacial advance or uplift steepens system. • Colluvial production rates are close to long-term denudation and uplift rates. • Subsequent glaciers may not need to produce much bedrock erosion. [ABSTRACT FROM AUTHOR]