GEOLOGY OF THE BIG FLAT AND BUFFALO CITY QUADRANGLES, OZARK PLATEAUS, NORTH-CENTRAL ARKANSAS

The Big Flat and Buffalo City quadrangles are located on the Salem and Springfield Plateau surfaces, on the southern edge of the Ozark Dome in north-central Arkansas. Approximately 22,500 acres of the Lower Buffalo Wilderness and 16,900 acres of the Leatherwood Wilderness are located within the quadrangles. Around 17 miles of the Buffalo National River and almost 14 miles of the White River meander throughout the quadrangles.

Approximately 1300 feet (396 meters) of Lower to Middle Ordovician, Mississippian, and Quaternary age strata is exposed in the area. The Lower to Middle Ordovician Cotter through St. Peter Formations comprise the surface rock over the majority of the area. Middle to Upper Ordovician Joachim, Plattin and Fernvale Limestones are locally present in steep drainages. The Osagean Boone Formation crops out on ridges throughout the area and its Kinderhookian to Osagean St. Joe Limestone Member is locally present at its base. The Chesterian Batesville Sandstone forms a small plateau around the community of Big Flat, Arkansas. Quaternary terrace and alluvium deposits are present in the valleys of the Buffalo River, White River and their tributaries. Two terrace levels are well developed along the Buffalo and White Rivers – a younger and medial. Very old terraces are located over 200 feet (61 meters) above the Buffalo and White Rivers.

Geologic mapping highlights recently mapped faults, karst features, and economic resources. Recent mapping discovered several small faults and monoclines that were previously un-documented. Karst features include paleokarst at the St. Peter/Everton unconformable contact and breccias within MVT deposits. Nearly all of the geologic formations are susceptible to karst formation and contain sinkholes, springs, or caves. Economic resources include crushed stone, sand, dimension stone, and manganese. This area was heavily prospected for zinc in the late 1800s and early 1900s.