The Lower Cretaceous fossils and those determined simply as Cretaceous are from siltstone of the belt along the upper Holokuk River and at the northeast foot of the Kiokluk Mountains. ....Collection 19731 was taken from nearly flat lying calcareous siltstone and silty limestone, less than half a mile southeast of exposures of the Kuskokwim group near the mouth of Girl Creek, and are bordered on the southeast by a shear zone believed to be that of a large fault.