T2 Non-Perennial Streams and the Fluvial System

Sunday, 9 October 2022
8:00 AM - 12:00 PM
406

ESTIMATING THE AGE OF ABANDONED ALLUVIAL SURFACES USING MORPHOLOGIC DATING OF GULLY INCISION

Paper number: T2-5
Program: Technical Sessions
Time: 8:55 AM – 9:10 AM

Authors

Abstract

The age of abandoned alluvial surfaces is a key component in quantifying processes of landscape evolution, tectonic activity, and paleo-climate. However, the dating of such landforms is often limited by restricted resources, field accessibility, dating material availability, and analytical complexities in dating techniques. To help address these limitations, we propose a new and complementary approach for dating abandoned alluvial surfaces that is based on calculating the incision duration of gullies on such landforms using a landscape evolution model. This approach uses high-resolution topographic data to (1) calibrate the parameters of a landscape evolution model for gully incision into a surface with an a-priori known age; (2) apply the calibrated model to compute the duration of incision required to form observed gully profiles on nearby alluvial surfaces with unknown ages. This approach was tested on a set of previously dated late - mid Pleistocene alluvial terraces in the hyper-arid Negev desert (southern Israel). Model parameters calibrated for gullies incised into a previously dated 70 ka surface were within the typical range reported elsewhere for arid regions. Modeled incision durations for gullies on nearby late Pleistocene (34 and 70 ka) terraces were within 10% of their independently obtained surface-ages. In contrast, modeled incision duration for gullies on an older surface previously dated to 230-539 ka, were grossly underestimated at <120 ka, an underestimation that is associated with documented temporal changes in tectonic/climatic boundary conditions that violate the assumptions that underlie the proposed approach. Accordingly, we propose morphologic dating of gully incision as a new and effective approach for constraining the age of alluvial surfaces and that as with other surface dating approaches – the validity of ages obtained hinges on the validity of the underlying assumptions and geologic framework employed

Geological Society of America Abstracts with Programs. Vol. 54, No. 6

doi: 10.1130/abs/2022AM-380969

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