Paleomagnetic studies of the early carboniferous St. Joe Limestone, Arkansas

The Kinderhookian (early Tournaisian) St. Joe Limestone was sampled at two quarries in the Ozark Plateau. A total of 110 oriented core samples were collected from brick red to gray crinoidal limestone and mudstone at approximately 20‐cm stratigraphic intervals. All samples were reversely magnetized. A selection procedure based upon directional stability of demagnetized vectors restricts the stable data population to 39 and 43 samples at each site with paleomagnetic pole positions of 46.2°W longitude, 37.0°S latitude, α95 = 1.67, κ = 189; and 50.7°W longitude, 40.6°S latitude, α95 = 1.48, κ = 218, respectively. These results from ‘cratonic’ North America are the first from early Carboniferous rocks and delimit a period of active apparent polar wander to the latest Devonian and earliest Carboniferous. The relative motion involved a clockwise rotation of the plate. This was immediately followed by a quasi‐static period during the Carboniferous. However, beginning in the latest Carboniferous the North American plate rotated counterclockwise with a large northerly component of motion about a tectonic rotational point at 62°N, 150°E.