Paleozoic sediment dispersal before and during the collision between Laurentia and Gondwana in the Fort Worth Basin, USA

Abstract

We report detrital zircon U-Pb ages in the Fort Worth Basin (southern USA) aimed at understanding sediment dispersal patterns on the southern margin of Laurentia before and during the Laurentia-Gondwana collision. The ages from two Cambrian fluvial-marginal marine sandstone and six Pennsylvanian deltaic-fluvial sandstone samples span from Archean to early Paleozoic time. In the Cambrian sandstones, 80% of zircons are of Mesoproterozoic age (1.451-1.325 Ga) and 18% are of Grenvillian age. The high abundance of the Mesoproterozoic population suggests that the grains were dispersed by a local river draining the midcontinent granite-rhyolite province located in the Texas Arch to the northwest of the Fort Worth Basin. In the Pennsylvanian sandstones, 26% of zircons are of Archean-early Mesoproterozoic age, 47% are of Grenvillian age, 15% are of Neoproterozoic-earliest Paleozoic age (800-500 Ma), and 10% are of early Paleozoic age (500-318 Ma), indicating a different dispersal pattern during the Pennsylvanian relative to the Cambrian. Compared to other early Paleozoic detrital zircon records on the southern margin of Laurentia, our Pennsylvanian sandstones have a distinct age peak at ca. 650-550 Ma, which we interpreted to be a result of transport by local rivers draining a peri-Gondwana terrane, most likely the Sabine terrane in the Ouachita orogen. The high abundance of Grenvillian zircons reflects either direct transport from the Appalachians by an axial river or recycling from Mississippian-Pennsylvanian sedimentary rocks incorporated in the Ouachita orogenic front. The similarity of detrital zircon age distributions in the Fort Worth Basin, the Arkoma Basin, and the southern Appalachian forelands seems to favor sediment dispersal by a major river with headwaters in the southern Appalachians.