ng are moderately fossiliferous. The M-P GSSP is defined at the evolutionary first appearance of the phosphatic microfossil Declinognathodus noduliferus (Animalia, Chordata, Conodonta, Conodonti, Ozarkodinida, Idiognathodontidae).
Above: James St. John (kneeling) pointing to the official Mississippian-Pennsylvanian GSSP, accompanied by geologists Matt Saltzman (standing in foreground) & Mats Eriksson, Katie Tierney, Amanda Cavin, and Seth Young (background).
EAST OF THE NARROWS
Above: Looking ~E. The lower Bird Spring Formation (Morrowan Stage, Lower Pennsylvanian), as exposed in Arrow Canyon, a little east of the Narrows. The sometimes-cherty limestone beds here are dipping eastward.
Above: Looking ~W. These are eastward-dipping limestones of the Bird Spring Formation, which is still Pennsylvanian in age here.
Above: Looking ~WNW. Upper Pennsylvanian limestone beds of the Bird Spring Formation, dipping eastward.
Above: Looking ~N. Fossiliferous limestones of the upper Bird Spring Formation. The Pennsylvanian-Permian boundary occurs about midway through the section shown in this photo. The most obvious fossils in the limestones here are fusulinid foraminifera.
Above: Looking ~E. Eastward-dipping limestones of the Bird Spring Formation, which is Lower Permian here.