301-3 Detrital Zircon U-Pb Geochronology of Mesoproterozoic Grenvillian Clastic Rocks, West Texas, U.S.A.: A Distinction from the Eastern U.S. Midcontinent

Session: Geochronology (Posters)

Presenting Author:

Authors:

Abstract:

Using U-Pb detrital zircon geochronology, we examine the exhumation history of the Grenville orogen from one of its few exposed foreland basin successions in west Texas. The Hazel Formation is a clastic succession north of the Grenville Front and is interpreted as a foreland basin deposit. The Hazel is exposed in the Van Horn Mountains, where trends of the Grenville Front (1035 Ma) deform it and the underlying Tumbledown and Allamoore Formation strata in a foreland fold-thrust belt. Geochronology of Hazel feldspathic litharenite (n = 906), provide the following constraints on Grenville exhumation into a southwestern Grenvillian foreland basin. (1) The maximum depositional age of Hazel is ~1035 Ma. (2) The Hazel was deposited nearly contemporaneously with the Middle Run Formation (~1015 Ma, n = 1813) in the buried midcontinent of Kentucky and Ohio. (3) Both Middle Run and Hazel reflect an actively unroofing Grenville orogen as represented by crustal components corresponding to Shawinigan, Elzevirian, and pre-Elzevirian phases of the Grenville Orogenic Cycle, with significant Granite-Rhyolite Province input. (4) The presence of only a minor Ottawan age component in the Hazel and Middle Run indicates that deeper Ottawan crust in the Grenville orogen had not yet been significantly exhumed by ca. 980 Ma. (5) The Hazel Formation contains abundant ages from the Midcontinent Rift (1100 Ma), Granite-Rhyolite (1350 – 1500 Ma), Yavapai-Mazatzal (1600 – 1700 Ma), Penokean (1880 Ma), and Superior (2600 – 2700 Ma) Provinces, bearing a striking resemblance to the Neoproterozoic Jacobsville Sandstone and equivalent sedimentary rocks near Lake Superior in Michigan. West Texas, like the buried midcontinent, constitutes a section of the Grenvillian clastic wedge that is more proximal to the Grenville Front than any other region of Laurentia. However, the Hazel is distinguished from the Middle Run by containing significantly more Paleoproterozoic and Archean detrital zircon, requiring greater cratonic (central Laurentia) input. This distinction possibly indicates an entirely different yet contemporaneous sedimentary system for the southwestern Grenvillian foreland than what is observed in the eastern midcontinent. We propose that the southwestern Grenvillian foreland was supported by both local southwest LIP/Llano Province sediment and a longitudinal fluvial system, transporting recycled sediment from north-central Laurentia (Jacobsville), along the Grenville Front, and depositing detritus in the region of present-day west Texas.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9949

© Copyright 2025 The Geological Society of America (GSA), all rights reserved.