Faulted Limestone Block Dredged from Blake Escarpment
An in-place limestone block dredged from the upper part of the Blake escarpment (1630 to 2000 m) has two distinct shear planes at an acute angle with well-developed slickensides. The orientation of the slickenside grooves parallel to bedding defined by miliolid foraminifera and lips on the slickenside surface indicate that strike-slip displacement, probably right-lateral, was involved in the faulting. Paleontological and outcrop depth evidence suggest a Late Cretaceous (Cenomanian-Campanian ?) age for the dredged boulder. This faulting of Cretaceous strata at the Blake escarpment is believed to be associated with the Great Abaco fault, a presumed extension from transform faulting along a fracture zone of the Mid-Atlantic Ridge.