INSIGHTS INTO EARLY PENNSYLVANIAN SEDIMENT ROUTING FROM DETRITAL ZIRCON U-PB AND HF ISOTOPIC DATA, DEEPWATER OUACHITA BASIN

The Paleozoic Appalachian orogeny resulted in large-scale reorganization of Laurentian river systems and sediment routing. Several detrital zircon (DZ) studies document the arrival of Appalachian-derived age populations beginning in the Carboniferous in western North America, including in the Grand Canyon, the ancestral Rocky Mountains in Colorado, and the Bighorn basin of Wyoming, and inferred large-scale east-to-west sediment transfer. However, there are numerous topographic obstacles to an east-to-west flowing fluvial system, including several north-south trending paleovalleys and the Ouachita deepwater sink. Source-to-sink analyses of these paleovalleys from source terrains to deepwater deposits will test this continental-scale fluvial system hypothesis and refine the character of late Paleozoic Laurentian sediment routing.

The provenance of the deepwater Jackfork Group and Johns Valley Shale (Morrowan) in Arkansas has been debated for several decades. Sediment source areas to the north (craton), south (oceanic or continental arc), and east (Appalachian orogeny) have all been proposed in varying proportions. Preliminary results of this study indicate a primary Appalachian provenance. Jackfork Group DZ samples from DeGray Lake Spillway and Jackfork Group and Johns Valley Shale samples from south of Kirby yielded abundant ca. 1.25-0.95 Ga (Grenville Province-age), ca. 500-400 Ma (Appalachian Province-age), ca. 1.55-1.30 Ga (Midcontinent Province-age), and ca. 1.80-1.60 Ga (Yavapai-Mazatzal Province-age) grains. Low abundance DZ populations were observed ca. 2.7 Ga and ca. 600 Ma.