Detrital zircon geochronology, provenance, and reservoir properties of the upper and lower Morrow sandstones, Anadarko Basin, U.S.A.

Deposition during Pennsylvanian Morrowan time (323.3 Mya to 298.9 Mya) was influenced by both regional tectonics and eustatic sea level changes. In the Midcontinent region, Morrowan deposition was dominantly siliciclastic, resulting in shale and sandstone, with lesser amounts of conglomerate. This study presents 570 new detrital zircon U-Pb absolute radiometric dates and 62 new eHf(t) measurements for the Morrowan sandstone from wells drilled on the northern shelf of the Anadarko basin in Oklahoma and southwestern Kansas, respectively. Analyses herein refines provenance and evolution of source areas during Morrowan time, improves our understanding of the relationship between provenance, detrital composition and sediment distribution, and allows inferences about the relationship between Morrowan dispersal systems and reservoir distribution. The U-Pb radioactive dates of the ablated zircons indicate the lower Morrow and upper Morrow detrital grains are strikingly different, representing distinct populations and different provenances, and supports the extension of a NE-SW transcontinental sediment dispersal system to the southern Midcontinent during Morrowan time. Calculations from the three measured Pb-U isotopic ratios: ²⁰⁶Pb/²³⁸U, ²⁰⁶Pb/²⁰⁷Pb, and ²⁰⁷Pb/²³⁵U indicate the lower Morrow sandstone in Woodward County, Oklahoma has a more varied set of potential sources for detrital zircons including dominant Grenville and Paleozoic Appalachian, moderate Paleoproterozoic Yavapai-Mazatzal and Mesoproterozoic Granite-Rhyolite Terranes and minor age peaks and sources in Superior and Wyoming cratons and the Trans-Hudson and Penokean orogenic belts provenances. In contrast, the age distribution for detrital zircons in the upper Morrow sandstone from Morton County, Kansas is restricted to two relatively narrow intervals that indicate only two major sources: Granite-Rhyolite terranes, and Yavapai-Mazatzal/Central Plains province. Lower Morrow sandstones are more quartz dominated, plot mostly as quartz arenites and sublitharenites, and contain detrital limestone fragments, suggesting marine influence. Upper Morrow sandstones contain abundant granitic rock fragments and feldspars and plot mostly litharenites and sublitharenites, suggesting a strong fluvial influence and an important inland granitic sediment source.