19 Depositional systems and resource distribution in eastern and southern North America: from orogens to coastal plains

We welcome studies related to the sourcing, dispersal, and deposition of clastic sediments from the hinterlands to the coast, including the provenance, paleogeography, sedimentology, and economic significance of these deposits.

Tuesday, 10 March 2026
8:30 AM - 11:30 AM
RCC, 105

Downstream Evolution of Detrital Zircon Signatures and Heavy Mineral Ratios in the Roanoke River, SE USA

Paper number: 19-4
Program: Technical Sessions
Time: 9:20 AM – 9:35 AM

Authors

Abstract

The course of the Roanoke River traverses multiple Appalachian physiographic provinces, from the Valley and Ridge, through the Blue Ridge and Piedmont, to the Atlantic Coastal Plain. The river’s catchment area therefore encompasses a broad range of rock types and depositional, emplacement, and crystallization ages. Here, we examine how the regional geology is reflected in the sediment bedload of the present-day Roanoke River through a two-fold study of provenance indicators. By analyzing both the ages of detrital zircons (DZ) and the ratios of sand-sized heavy mineral (HM) grains present within modern fluvial deposits, we aim to assess how these data sets differ in their ability to record various aspects of the surrounding bedrock (e.g., rock type, erodibility, zircon fertility), and how geographic and anthropogenic factors influence sediment composition. Our results show that DZ geochronology and HM content are decoupled, with age populations evolving downstream in response to tributary inputs, changes in bedrock composition, and possibly river impoundments. HM content, in contrast, is more variable, changing significantly between individual samples tens of kilometers apart but still showing an overall downstream evolution in dominant grain mineralogy, from oxides (hematite and ilmenite) in Valley and Ridge and western Blue Ridge headwaters, to amphibole- and epidote-dominated assemblages in the eastern Blue Ridge and Piedmont, to epidote, amphibole, and staurolite/kyanite assemblages in the lower Coastal Plain (CP). Such data are useful in predicting the occurrence and composition of detrital heavy mineral deposits, which are mined commercially within the study area from Pliocene CP units. Additionally, a better understanding of the intra-river variation in DZ signatures helps improve interpretations of provenance and paleogeographic reconstruction in sedimentary deposits preserved deeper in the geologic record.

Geological Society of America Abstracts with Programs. Vol. 58, No. 1

doi: 10.1130/abs/2026SE-411769

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