Groundwater seepage landscapes from local or distal sources in experiments and on Mars
Abstract
Theater-headed valleys can form due to groundwater sapping, but these valleys could also be the result of knick-point (waterfall) erosion generated by overland flow. This morphological ambiguity hampers the interpretation of such valleys on Mars, especially due to insufficient knowledge of material properties, but the climate implications are quite different. Instead of single-valley morphology, metrics of the entire landscape may provide diagnostic insight in the formative hydrological conditions. However, flow patterns and the resulting landscapes are different for different sources of groundwater and poorly understood. We aim to increase our understanding of the formation of the entire landscapes by sapping from different sources of groundwater and to provide a framework of landscape metrics of such systems to aid interpretation of such landscapes. We study sapping from local and distal sources of groundwater in sandbox experiments and combine our results with previous experiments. Key results are that groundwater piracy acts on distally-fed valleys, which results in a sparsely dissected landscape of many small and a few large valleys while locally-fed valleys result in a densely dissected landscape. In addition, distally-fed valleys grow into the direction of the groundwater source while locally-fed channels grow in a broad range of directions and have a strong tendency to bifurcate, particularly on flat horizontal surfaces. As an example, we apply these results to two Martian cases. The valleys of Louros Valles show properties of sapping by a local source and Nirgal Vallis shows evidence of a distal source, which is likely groundwater from Tharsis.
- Publication:
-
Earth Surface Dynamics Discussions
- Pub Date:
- February 2015
- DOI:
- 10.5194/esurfd-3-129-2015
- Bibcode:
- 2015ESuDD...3..129M