Spectacular examples of rapid (1 k.y. to 1 m.y.) perturbations of the global carbon cycle and extreme changes in Earth's climate occurred during the Cretaceous and Paleogene periods (e.g., Cretaceous oceanic anoxic events [OAEs] and the Paleocene/Eocene Thermal Maximum [PETM]) (Erbacher et al., 2003; Zachos et al., 2001, 2006; Wilson et al., 2002). In many cases, these events were accompanied by widespread extinction of marine and terrestrial biota (e.g., Coxall et al., 2006). Many questions remain, however, about the underlying causes and effects of these critical events in Earth history. High-resolution paleoceanographic records from ocean drill sites, particularly from tropical regions that are important in driving global ocean-atmospheric circulation, help address these gaps in understanding.
Demerara Rise is a submarine plateau that is an apparent extension of the continental margin north of Suriname and French Guyana, South America, located in the tropics just north of the Equator between 8° and 10°N latitude and 52° and 56°W longitude (Fig. F1). The rise stretches ~380 km along the South American coast and is ~220 km wide from the shelf break to the northeastern escarpment, where water depths increase from 1000 to >4500 m (Fig. F1). Its geographic and tectonic position makes it an ideal location to investigate late-stage Atlantic rifting and opening of the Atlantic Gateway in the mid- to Late Cretaceous. The outer Demerara Rise is known to contain shallowly buried and expanded sections of Cretaceous- and Paleogene-age sediments (Hayes, Pimm, et al., 1972; Erbacher, Mosher, Malone, et al., 2004). Ocean Drilling Program (ODP) Leg 207 focused on sampling these Cretaceous and Paleogene deep-sea sediments at the northwestern extent of the rise (~9°N, in 1800–3400 m water depth) (Fig. F1). During the leg, continuous records of the PETM, Cretaceous/Paleogene (K/P) boundary, and OAEs were successfully recovered.