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Combined single-grain (U-Th)/He and U/Pb dating of detrital zircons from the Navajo Sandstone, Utah

Date

2003

Authors

Rahl, Jeffrey
Reiners, Peter
Campbell, Ian
Nicolescu, Stefan
Allen, Charlotte M

Journal Title

Journal ISSN

Volume Title

Publisher

Geological Society of America Inc

Abstract

Radioisotopic dating of detrital minerals in sedimentary rocks can constrain sediment sources (provenance), elucidate episodes and rates of ancient orogenesis, and give information on paleogeography and sediment-dispersal patterns. Previous approaches have been restricted to the application of a single technique, such as U/Pb or fission-track dating, to detrital grains. These methods provide crystallization and cooling ages, respectively, of sediment sources (terranes). However, evidence for source regions from a single technique can be ambiguous because candidate source terranes often have similar ages for a given radioisotopic system. This ambiguity can be avoided by applying multiple radioisotopic systems to individual detrital grains. Here we present a method for measuring both (U-Th)/He and U/Pb ages of single crystals of detrital zircon, providing both formation and cooling ages (through ∼ 180 °C). We applied this technique to zircons from the Lower Jurassic Navajo Sandstone, which represents one of the largest erg deposits in the geologic record. A large fraction of these zircons was derived from crust that formed between 1200 and 950 Ma, but cooled below ∼ 180 °C ca. 500-250 Ma. This history is characteristic of Grenvillian-age crust involved in Appalachian orogenesis (and subsequent rifting) in eastern North America. Our finding requires the existence of a transcontinental sediment-dispersal system capable of moving a large volume of detritus westward (modern coordinates) throughout the late Paleozoic and early Mesozoic.

Description

Keywords

Keywords: Orogenesis; Radioisotopes; Sedimentary rocks; Sediments; Single crystals; Geochronology; crystallization; dating method; detrital deposit; geochronology; Jurassic; provenance; sandstone; zircon; United States (U-Th)He; Geochronology; Navajo Sandstone; U/Pb; Zircon

Citation

Source

Geology

Type

Journal article

Book Title

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Access Statement

License Rights

DOI

10.1130/G19653.1

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