21 D1. Advances in Geomorphology and Quaternary Geology (Posters)

Sunday, 15 October 2023
8:00 AM - 5:30 PM
Hall B

RELATIONSHIP BETWEEN DRAINAGE BASIN ASYMMETRY INDICES AND BEDROCK DIP IN AREAS WITH RESISTANT ROCK AND GENTLY DIPPING STRATA

Paper number: 21-15
Program: Technical Sessions
Time: 8:00 AM – 5:30 PM

Authors

Abstract

Asymmetry of drainage basins can reveal important geologic information. The formation of an asymmetric drainage basin requires the migration of the river channel from the drainage basin's center and the degree and direction of asymmetry reflect the fluvial, geologic, or tectonic process driving river migration. In locations with homogeneous and unconsolidated strata, random river migration is prevalent, resulting in symmetric floodplain erosion governed by fluvio-climatic processes. Tectonics is a well-known external element that influences preferred river migration, with rivers shifting in the direction of active tectonic tilt. River migration is also influenced by the dip and hardness of the bedrock. This favored river migration is referred to as a monoclinal shift, and the degree of migration is determined by bedrock dip and rock hardness. We investigated drainage basin asymmetry data from the Cumberland Plateau to see if there is a systematic difference in the degree of asymmetries with different degrees of bedrock dip and resistant rock hardness. The Relative River Migration metric (RRI) is a new geomorphological index that we developed to study the ratio of vertical incision to lateral displacement in basins with bedrock floors. The data suggests that as the bedrock becomes steeper, vertical incision prevails over lateral displacement. We discovered that when the resistant rock's hardness increases, lateral shift takes precedence over incision. In basins with resistive beds and gently to moderately dipping strata, we identified a statistically significant empirical relationship between RRI value and bedrock dip and hardness. Using remotely derived indices such as T value and RRI, we may understand the underlying bedrock structure in such basins, thus highlighting the geomorphological and structural significance of this technique.

Geological Society of America Abstracts with Programs. Vol. 55, No. 6

doi: 10.1130/abs/2023AM-390751

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