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GSA Connects 2022 meeting in Denver, Colorado

Paper No. 2-4
Presentation Time: 8:55 AM

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


SHMILOVITZ, Yuval, The Fredy & Nadine Herrmann Institute of Earth Sciences, The Hebrew University of Jerusalem, Jerusalem, 9190401, Israel; Geological Survey of Israel, 32 Yesha'yahu Leibowitz St., Jerusalem, 9371234, Israel, SHELEF, Eitan, Department of Geology and Environmental Science, University of Pittsburgh, 4107 O'Hara St., Pittsburgh, PA 15260, WIELER, Nimrod, Geological Survey of Israel, 32 Yesha'yahu Leibowitz St., Jerusalem, 9371234, Israel, ZHANG, Huiping, State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing, 100029, China and MUSHKIN, Amit, Geological Survey of Israel, 30 Malkhe Israel St., Jerusalem, 95501, Israel

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

Session No. 2

T8. Non-Perennial Streams and the Fluvial System
Sunday, 9 October 2022: 8:00 AM-12:00 PM
406 (Colorado Convention Center)
Geological Society of America Abstracts with Programs. Vol 54, No. 5
doi: 10.1130/abs/2022AM-380969
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