Sediment Source of Lower Miocene Strata in the Gulf of Mexico Basin: Insight From Detrital Zircon U–Pb Geochronology and (U–Th)/He Thermochronology

Abstract

Detrital U–Pb geochronology has become one of the most widely used tools for provenance analyses elucidating sediment source, sediment routing, drainage basin evolution, and characterization of source terranes. However, detrital zircon U–Pb geochronology has inherent limitations to resolve sediment provenance precisely, because single U–Pb dating reveals little information about tectonic exhumation events that ultimately control basin evolution and sediment dispersal. Investigations of large passive margin basins, such as the Gulf of Mexico Basin, that have received sediment from multiple terranes with indistinguishable crystallization ages or sedimentary strata, require additional information to constrain provenance interpretation. In this study, combined U–Pb and (U–Th)/He analyses on single zircon grains from the Lower Miocene sandstones in the northern Gulf of Mexico Basin reveal a complicated history of sediment source evolution. Single U–Pb age data indicate that most sediment sources came from five major crystalline terranes, including the Yavapai–Mazatzal (1800–1600 Ma), Mid–continent Granite–Rhyolite (1500–1300 Ma), Grenville (1300–950 Ma), Appalachian–Ouachita (500–260 Ma), and Western Cordillera Arc (<250 Ma) terranes. A few zircons are from Pan–African (700–500 Ma) and Canadian Shield (>1800 Ma) terranes. Zircon (U–Th)/He analyses document multiple cooling events from major U–Pb components, including Grenville (1300–950 Ma), Appalachian–Ouachita (500–300 Ma), Ancestral Rockies (~310 Ma), Pangea rifting (250–150 Ma), Sevier–Nevadan (170–80 Ma) and Laramide (80–40 Ma) tectonism and mid–Cenozoic volcanism (40–24 Ma). The revealed cooling ages coupled with crystallization age provide dual constraints for sediment provenance interpretation, and thus we can differentiate volcanic and plutonic zircon source, as well as multi–recycled sedimentary sources (e.g., Grenville zircons). This double dating method allows much greater understanding of the complex sediment source for large passive margin basins such as the Gulf of Mexico Basin.

AAPG Datapages/Search and Discovery Article #90291 ©2017 AAPG Annual Convention and Exhibition, Houston, Texas, April 2-5, 2017