Limestone rolls in western Kentucky
Parallel sets of rolls hundreds of feet in length and a few feet to 20 feet in width were encountered in the Peabody Camp Mine No. 11 in Union County. The rolls occurred above the Herrin (W. Ky. No. 11) coal where the coal was directly overlain by the Brereton (Providence) Limestone (Mathis, 1982; Nelson, 1983). These rolls had straight orientations in map view and paralleled narrow trends of thickness change in the underlying coal (Mathis, 1983). In some other Herrin coal mines, limestone rolls are associated with clay veins and small offset clay-vein faults. Trends of the clay veins and axis of the limestone roof roll are generally similar.
The roof of the Herrin coal also may contain large, irregular-shaped, downward-projecting masses of limestone termed “limestone bosses.” These are explained in the section on concretions.