Demerara Rise occupied a key paleogeographic position for examining paleoceanographic evolution during the late Campanian–Maastrichtian, a 5- to 10-m.y. interval of climate moderation at the end of ~40 m.y. of Cretaceous greenhouse climate. Demerara Rise was located at tropical latitudes, and neither Maastrichtian tropical temperatures nor tropical temperature trends are well constrained (e.g., D'Hondt and Arthur, 1996; MacLeod and Huber, 2001; Pearson et al., 2001). Demerara Rise is also in the North Atlantic, which appears to have experienced regional warming (Wolfe and Upchurch, 1987; Corfield and Norris, 1996; Barrera and Savin, 1999; Frank and Arthur, 1999; MacLeod et al., 2005) at the same time as widespread and well-documented cooling at mid- to high latitudes (e.g., Douglas and Savin, 1975; Barrera et al., 1987; Spicer and Parrish, 1990; Huber and Watkins, 1992; Huber et al., 1995; Barrera and Savin, 1999; Francis and Poole, 2002; Lees, 2002). Finally, Demerara Rise is near the tropical Atlantic gateway, and changes in patterns of ocean circulation, including the nature of flow between the North and South Atlantic, have been invoked to explain Maastrichtian climate evolution (e.g., Barrera and Savin, 1999; Frank and Arthur, 1999; MacLeod and Huber, 2001; D'Hondt and Arthur, 2002; Frank et al., 2005; MacLeod et al., 2005).
The upper Campanian–Maastrichtian was recovered in multiple holes in each of the five sites drilled on Demerara Rise during Ocean Drilling Program (ODP) Leg 207. Unfortunately, foraminiferal preservation was variable throughout the interval. Test morphology is generally well preserved with hollow foraminifers found throughout, but sparry calcite is common within otherwise well-preserved specimens. In addition, well-formed, sand-sized "cockscomb" marcasite is present in many washes. That is, at least two diagenetic phases are common in these samples, and quality of isotopic preservation is a significant concern for any paleoceanographic study of samples from these cores. To provide initial constraints on the relative importance of primary paleoceanographic conditions and diagenetic overprinting in the Demerara record, bulk carbonate 
13C and 18O values were measured from upper Campanian and Maastrichtian samples. Values observed are not prohibitively unreasonable; however, scatter within trends in any section and lack of congruence in trends among correlative samples across sites argue that diagenetic overprinting will complicate any Campanian–Maastrichtian stable isotopic studies of Demerara Rise samples.
