PARTHENON SANDSTONE: A PROMINENT NEW MEMBER OF THE MORROWAN BLOYD FORMATION, PENNSYLVANIAN OF NORTH-CENTRAL ARKANSAS

The Bloyd Formation in northwestern Arkansas is a succession of limestone siltstone and shale units in the type area of Washington County that accumulated in shallow marine and non marine environments during late Morrowan time. East of Washington County a fine to medium grained fluvial sandstone is present in the middle of the formation. The sandstone, a lateral equivalent of the non marine Woolsey Member of Washington County, ranges in thickness from 3-40 meters and extends at least 120 kilometers eastward from the Washington-Madison county line. The unit is characterized by well rounded granule to pebble size grains of quartz and multiple sets of cross-strata. The tabular sets are up to 3 meters in thickness. The sandstone unit has been the topic of numerous theses by University of Arkansas students and has been informally called the middle Bloyd sandstone since the 1970s. The unit has never been formally named.

Recent STATEMAP mapping by the Arkansas Geological Survey has delineated this unit on nineteen 7.5 minute quadrangle maps. The USGS has positioned the unit on an additional 6 quadrangle maps, all in north-central Arkansas east of Washington County. Because the unit is frequently studied for sedimentological reasons and is a target for natural gas exploration in the Arkoma basin south of the outcrop area, we will propose the name Parthenon Sandstone Member after the community of Parthenon on the Parthenon Quadrangle in Newton County, where its distribution and boundaries are clearly delineated and where a type section will be designated.