T163 Advances and Applications of Thermochronology in Tectonic, Magmatic, Basin, and Geomorphic Studies (Posters)

Tuesday, 11 October 2022
9:00 AM - 1:00 PM
Exhibit Hall F

A NEW MODERN RIVER DETRITAL RECORD OF SOUTHERN APPALACHIAN GEO- AND THERMOCHRONOLOGICAL EVENTS: IMPLICATIONS FOR TECTONICS AND SEDIMENTARY PROVENANCE

Paper number: T163-18
Program: Technical Sessions
Time: 9:00 AM – 1:00 PM

Authors

Abstract

Geo- and thermochronology data from the southern Appalachian Mountains are sparse compared to the northern U.S. extent of the range, and as a result, the provenance signature has largely been inferred from Paleozoic foreland basin proxies. In this study, we survey the Appalachian orogenic belt using detrital zircon (DZ) and detrital apatite (DA) U-Pb and low-temperature fission track (FT) double dates from the sediment of eighteen modern rivers. Sand was collected from fourteen east- and four west-flowing rivers, upstream of the Atlantic and Gulf Coastal Plain. The contiguous river catchments span ~1800 km from New York to Alabama and in total cover ~78% of the presently exposed southern Appalachian hinterland (Piedmont and Blue Ridge) and foreland basin (Valley-and-Ridge and Appalachian Plateau). DZ U-Pb ages (n=1600) match bedrock map distributions, with Grenville-age zircon dominant in southwestern and northern rivers but relatively rare in eastern rivers. Conversely, Paleozoic Taconic-, Alleghanian-, and Acadian-age zircon are most abundant east of the drainage divide. Whereas zircon is subject to recycling from multiple orogenies, DA U-Pb ages (n=1125) record cooling through mid-crustal temperatures (375–570°C) and thus serve as indicators of recent orogenic provenance. Dominant DA U-Pb age components include 1) post-Grenville (ca. 800–950 Ma) ages restricted to Appalachian foreland basin sediments; and 2) ubiquitous Paleozoic ages with a broad 250–350 Ma mode, which likely represent peak crustal thickening and exhumation during magma-poor late-stages of the Grenville and Paleozoic orogenies, respectively. DZ FT cooling ages (n=1600) are variable, with unique Precambrian (>800 Ma) components in western rivers, Cenozoic (ca. 21–66 Ma) age components in eastern rivers, and common major components between 200–500 Ma. DA FT age components (n=1543) range from 45–615 Ma, with the majority of ages between 105–175 Ma. FT trends indicate that significant exhumation occurred in the southern Appalachians during the Jurassic–Cretaceous post-orogenic breakup of the Gondwana-Laurasia margin, followed by periods of Cenozoic rejuvenation. In aggregate, these data record the spatial extents of geo-thermochronologic events and refine the provenance signature of the southern Appalachian orogenic belt.

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

doi: 10.1130/abs/2022AM-379584

© Copyright 2022 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.