Fluvial Bedrock Incision Research Articles

Relative rates of fluvial bedrock incision on Titan and Earth

Observations of likely fluvial channels on the surface of Titan, along with Titan's geologically youthful surface, motivate this study of comparative fluvial erosion rates on Titan and the Earth. The roles of bedload abrasion, suspended load abrasion, plucking, and cavitation are considered. Despite orders of magnitude differences in some of the physical parameters that control fluvial incision on Titan and the Earth, incision rates on Titan are likely to be similar to terrestrial rates, given similar conditions of slope, discharge, and sediment supply.

Fluvial bedrock incision in the active mountain belt of Taiwan from in situ‐produced cosmogenic nuclides

AbstractThe concentration of cosmogenic nuclides in rocks exposed at the Earth's surface is proportional to the total duration of their exposure. This is the basis for bedrock surface exposure dating and has been used to constrain valley lowering rates in the Taroko gorge, eastern Central Range, Taiwan. Taroko gorge contains a uniquely complete geomorphic record of fluvial valley lowering: continuous, fluvially sculpted surfaces are present in the lower 200 m of this marble gorge. Assuming no post‐fluvial erosion of the gorge wall, the concentration of in situ‐produced cosmogenic 36Cl measured in gorge wall marbles reveals exposure ages from 0·2 ka in the active channel to 6·5 ka at 165 m above the present river. These ages imply an average fluvial incision rate of 26 ± 3 mm a−1 throughout the middle and late Holocene. Taking into account lateral gorge wall retreat after initial thalweg lowering would give rise to calculated older exposure ages. Without considering gorge wall retreat, our estimates therefore represent maximum incision rates. Estimated maximum Holocene incision rates are higher than the long‐term exhumation rates derived from fission track dating. The long‐term gorge development governed by tectonic uplift is superimposed by short‐term variations in incision rates caused by climatic or regional tectonic changes. Copyright © 2005 John Wiley & Sons, Ltd.

Climate-driven bedrock incision in an active mountain belt.

Measurements of fluvial bedrock incision were made with submillimeter precision in the East Central Range of Taiwan, where long-term exhumation rates and precipitation-driven river discharge are independently known. They indicate that valley lowering is driven by relatively frequent flows of moderate intensity, abrasion by suspended sediment is an important fluvial wear process, and channel bed geometry and the presence of widely spaced planes of weakness in the rock mass influence erosion rate and style.