Demerara Rise is a projection of the continental margin off the northeast coast of Surinam and French Guiana, South America, in depths deeper than 700 m. Ocean Drilling Program (ODP) Leg 207 employed coring in multiple holes at each site to obtain continuous records of the expanded sections of Albian–Oligocene strata (Erbacher, Mosher, Malone, et al., 2004) (Fig. F1). Sites 1257–1261 recovered nearly 5000 m of sediment along a depth transect at 1900–3100 meters below seafloor (mbsf). In addition to high-resolution records of the Late Cretaceous Ocean Anoxic Events, Paleocene/Eocene Thermal Maximum, and Eocene/Oligocene boundary, several stratigraphic intervals were characterized by cyclic sedimentation that appear to be responses to Milankovitch orbital cycles. These cyclic intervals were the focus of our detailed magnetostratigraphic studies.
The generalized stratigraphy across the Demerara Rise consists of four main units:
Magnetostratigraphy with constraints from biostratigraphy provides a chronostratigraphic framework in deep-sea sediments for paleoceanographic studies, including stable isotope trends and developing a high-resolution cyclostratigraphy tuned to orbital cycles. The primary goal of our paleomagnetic study was to establish a high-resolution magnetostratigraphy spanning the Late Cretaceous–Eocene at all Leg 207 sites with particular emphasis on continuous splices of cyclic sediments.
Note: for clarity in discussing calibrated chronostratigraphy vs. relative stratigraphic positions, we capitalize the official international subdivisions of epochs (e.g., Middle Eocene subepoch spans the Bartonian and Lutetian stages; Early Eocene subepoch is the Ypresian stage, etc.) The term "Lower" Eocene indicates the associated rock record that corresponds to the Early Eocene. Terms in lower case ("upper Eocene," "lower Lower Eocene," etc.). indicate only a relative position within the recovered strata of that international epoch or subepoch.