Variance Components of Cross-Bedding Direction in Some Basal Pennsylvanian Sandstones of the Eastern Interior Basin: Geological Application

Dip direction of torrential cross-bedding is a vectorial property providing a rapid measure of the local direction of sediment transport. Over 500 measurements in the basal Pennsylvanian Caseyville and Mansfield sandstones of southern Illinois and Indiana were taken, to explore its possibilities and limitations as a measure of direction of regional sediment transport. The analysis of variance helped interpret the pattern of variability, indicate the reliability of averages, and improve the efficiency of sampling effort. The host topography of the Mississippian-Pennsylvanian unconformity exercised a strong control on the basal cross-bedding direction. Averages of many measurements along 260 miles of outcrop, however, accurately indicate a southwesterly direction of sediment transport for the Caseyville and a southerly direction for the Mansfield. The importance of a northerly source is suggested but would have to be evaluated by petrologic study.