Stable oxygen isotopic composition: Use in determining ages of Bahama escarpment deep-marine calcite spars and implications for timing of erosion

Abstract

Stable oxygen isotopic compositions of deep-marine calcite spars contained in Early and middle Cretaceous, bank-interior limestones exposed erosionally on the Bahama escarpment suggest that these spars are Late Cretaceous to Miocene in age, two-thirds of the spars being middle Eocene or older in age. The Eocene and older spars are identical to pelagic and fore-reef strata unconformably overlying truncated bank-interior carbonates exposed on the Bahama escarpment. Spars contained in limestones taken from the northwest Bahama escarpment are nearly all (20 of 22 analyses) Late Cretaceous (Campanian and Maastrichtian) to middle Eocene in age. Most (12 of 20 analyses) spars from southeast Bahama escarpment limestones are late Eocene or younger in age. Thus, isotopic data are consistent with the initiation of erosion of the Bahama escarpment in the Late Cretaceous and its continuation until the middle of the Eocene. In addition, these data suggest that erosion of the southeast Bahama escarpment continued into, or was renewed during, the late Eocene and possibly the Oligocene-Miocene. Continued, or renewed, erosion of the southeast Bahama escarpment probably reflects tectonic interaction with the Caribbean-North American plate boundary along the Puerto Rico trench, or the flow of Antarctic Bottom Water only at the base of the southeast escarpment.