Discussion on Hundru fall as a knick point, Iharkhand, India

Subarnarekha River lies in the vicinity to the Ranchi mega lineament zone of Jharkhand State. This river links the Tamar Porapahar shear zone and North Singhbhum shear zone. The Hundru falls is the sudden and abrupt drop of elevation (longitudinal profile) of upstream of river Subarnarekha. The basic aim of this paper is to assess the Hundru falls as a perfect citation of an upstream knick point in Indian context. This paper covers the knick point formation of upstream of the Subarnarekha river. This upper catchment is more diversified in the terms of metamorphic and igneous rocks. This zone has crossed a long path with diversified lithospheric adjustment with epirogenic upliftment.

Groundwater seepage landscapes from local or distal sources in experiments and on Mars

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.

The upper cenozoic evolution of the Duero and Ebro fluvial systems (N-Spain): part I. paleogeography; part II. geomorphology

Lack of age dates in the terrigenous Cenozoic sediments of the Duero and the Ebro sedimentary basins has complicated tecto-stratic correlation across the two basins. We tentatively synthesize a range of existing studies and new data to construct a rough general paleogeography throughout Upper Cenozoic times. The more extensive erosion of the Ebro has been previously attributed to the earlier moment of opening. We tentatively analyse lithostratic data to conclude that the lower knick-point and different lithologies have also contributed to the deeper erosion in the Ebro Basin. We conclude from lithostratic data and field evidence that the W half of the Rioja was part of the Duero in earlier times and that the escarpment retreated westward through the Rioja in four subsequent episodes of erosion. The tilt of the NW Duero is a consequence of isostatic rebound to this erosion.