GEOLOGIC MAP OF THE MURRAY QUADRANGLE ADJACENT TO BUFFALO NATIONAL RIVER, NORTHERN ARKANSAS

USGS Scientific Investigations Map 3360 summarizes the geology of the Murray quadrangle in the Ozark Plateaus region of northern Arkansas. Buffalo National River, a park that encompasses the Buffalo River and adjacent lands, is present at the northwestern edge of the quadrangle. Geologically, the area is on the southern flank of the Ozark dome in the foreland of the Ouachita orogenic belt. Deep valleys of the Buffalo River and Little Buffalo River and their tributaries expose an approximately 500-m-thick sequence of Ordovician, Mississippian, and Pennsylvanian carbonate and clastic sedimentary rocks that have been mildly deformed by a series of faults and folds. Over 1000 GPS-located field sites provide control to evaluate stratigraphic and structural features within the quadrangle, including the following: (1) a truncation of older strata below a regional unconformity at the base of Pennsylvanian strata, with the thickness of Upper Mississippian Pitkin Limestone thinning northward from greater than 60 m to zero beneath the surface; (2) two northeast-trending fault and fold zones having down-to-southeast offset, as demonstrated by structure contours constructed from 234 control sites -- paleostress inversions for spatially associated faults demonstrate that these structural zones mostly accommodated north-south extension during late Paleozoic flexure of the southern Laurentian margin; (3) abundant karst features (caves, springs, losing streams, sinkholes) that are common in limestones of the Mississippian Boone Formation and Pitkin Limestone as well as interbedded limestone intervals of the Prairie Grove Member of the Lower Pennsylvanian Hale Formation; and (4) numerous large Quaternary landslide and debris flow deposits, sourced from Upper Mississippian and Pennsylvanian sandstone and shales, some deposits which extend far downslope and impact modern river and stream drainages.