Maastrichtian and uppermost Campanian strata are represented by over 200 m of chalk on the central and western parts of Blake Nose. In Leg 171B Hole 1050C, the chalk displays a prominent color cycle that has been related to the orbital precession cycle by MacLeod and Huber (2001) and MacLeod et al. (in press a). These authors also found that planktonic and benthic foraminifers record the cycle in both their abundance and stable isotope signature, suggesting that the color cycles reflect changes in oceanic production and carbonate deposition. Self-Trail (2001) has correlated these strata to onshore wells to revise the calcareous nannoplankton biostratigraphic zonation of the upper Maastrichtian. Stratigraphic studies of onshore boreholes will permit other studies of onshore-offshore evolution of deposition along the Atlantic coastal plain (Edwards et al., 1999).
The Maastrichtian section on Blake Nose is disturbed, particularly near its base, by pervasive plastic deformation that suggests large-scale gravity sliding of partly consolidated chalk. Klaus et al. (2000) proposed using seismic and coring evidence and that the Maastrichtian sequence was slumped at the Cretaceous/Paleogene boundary in association with the magnitude 13 Richter scale earthquake produced by the Chicxulub impact event. Norris et al. (2000) and Norris and Firth (in press) arrived at a similar conclusion and showed that sediment slumped off the Blake Nose was deposited in an extensive blanket of turbidites covering much of the deep western North Atlantic. ODP and Deep Sea Drilling Project sites on the New Jersey margin, the Bermuda Rise, and the Iberian Abyssal Plain all show evidence of mass wasting associated with the Cretaceous/Paleogene (K/P) boundary (Norris and Firth, in press). Max et al. (1999) used seismic evidence from Blake Nose to suggest that K/P boundary mass wasting may have vented gas hydrate reservoirs along the North Atlantic margin and added to the ecological catastrophe produced by the impact event.
The impact ejecta blanket was recovered in three holes at ODP Site 1049 (Klaus et al., 2000). Geochemical studies of the ejecta have confirmed that its chemistry is consistent with an origin as tektites that have been subsequently altered to clay minerals (Speed and Kroon, Chap. 4, this volume; Martinez-Ruiz et al., 2001a, 2001b). Smit (1999) showed that the size and composition of tektites in the ODP 1049 ejecta bed are characteristic of proximal ejecta deposits found elsewhere around the Caribbean and North America. The presence of small chips of metamorphic rocks, shallow-water limestone, dolomite, and shocked quartz are also consistent with derivation of the ejecta from the Chicxulub Crater (e.g., Norris et al., 1999). Recently, Norris et al. (1999), MacLeod et al. (in press a) and Huber et al. (in press) have shown that the geochemistry, biostratigraphic distribution, and size distribution of Cretaceous foraminifers found above the ejecta bed suggest that most Cretaceous planktonic foraminifer taxa became extinct during the K/P mass extinction. For example, MacLeod et al. (in press b) found that there is a small but detectable offset in the Sr isotope ratios of Cretaceous planktonic foraminifers and those characteristic of the earliest Danian that suggests that few Cretaceous species survived the boundary.