PALEOZOIC SANDSTONE RECORD, SOUTHERN OZARK REGION: DEPOSITIONAL CHARACTER AND HISTORY

The Paleozoic record of the southern Ozark region, northern Arkansas, southern Missouri, and northeastern Oklahoma, accumulated on a gently sloping cratonic platform reflecting transgressive-regressive, epeiric seas that eroded, transported and reworked terrigenous clastic sediments. The southern Ozark record begins with the Upper Cambrian-Lower Ordovician, thickest interval, potentially >3000 ft of Lamotte Sandstone through the Everton Formation; the Middle Ordovician-Upper Silurian, possibly 900 ft represented by the St Peter Sandstone through the Lafferty Limestone; the Lower Devonian-Upper Mississippian, >1700 ft of Penters Chert through the Pitkin Limestone; the Lower-Middle Pennsylvanian portion, divided into the Hale-Atoka Formations, represents at least 1500 ft in the southern Ozarks. Sandstones are well developed, although carbonates, including dolomites, dominate parts of some intervals, e.g. Upper Cambrian, Lower Ordovician, and Silurian. The sandstones represent five related, but distinct, intervals beginning with the Upper Cambrian Lamotte Formation, arkose, typically with a basal conglomerate, derived from the Precambrian granite of the Ozark Dome core. Following carbonate deposition, sandstones of the Gasconade and Roubidoux Formations reflect reworking of the Lamotte interval producing subarkoses, sublitharenites, and finally quartzarenites. The second interval is the Lower Ordovician portion of the Sauk marking the greatest covering of the Laurasian craton by epeiric seas. Frequent transgressive and regressive reworking produced well rounded, well sorted, orthoquartzites. These supermature quartz sandstones extend to the Bachelor Sandstone, basal member of the St. Joe Formation, Lower Mississippian, in the Kaskaskia. The Batesville Sandstone, Upper Mississippian, is the next sandstone interval, and first cycle. First cycle sandstones characterize the remainder of the record in the southern Ozarks (lower Absaroka), that can be subdivided into three categories: sandstones with few metamorphic rock fragments (mrfs); sandstones with common mrfs comprising the Morrowan interval, basal Pennsylvanian; sandstones with abundant mrfs capping the record as the Atoka Formation, Atokan Series, Middle Pennsylvanian, and the thickest Paleozoic unit