Site 999 is on the Kogi Rise, located ~1000 m above the turbidite-laden floor of the Colombian Basin (Fig. 1). A 1066-m-thick continuous and apparently complete upper Maastrichtian-Pleistocene section was recovered. This section consists dominantly of pelagic sediments and sedimentary rocks with variable amounts of clays and volcanic ash (Fig. 2). The investigated interval at Site 999 ranges from 250 to 640 mbsf, spanning from the upper Oligocene through the base of the upper Miocene (Fig. 2). This interval comprises different lithostratigraphic units (Units II, III, and IV) (see Fig. 2) determined on board ship on the basis of sedimentologic criteria, magnetic susceptibility, color reflectance, and carbonate content (Sigurdsson, Leckie, Acton, et al., 1997).
Site 1000 is located in Pedro Channel, one of a series of channels that dissects the carbonate banks defining the Nicaraguan Rise (Fig. 1). A continuous, fairly homogeneous lower Miocene to Holocene section (696 m thick) was recovered, which consists dominantly of periplatform sediments and sedimentary rocks, interbedded with volcanic ash layers and intervals of redeposited pelagic and neritic carbonates from the adjacent shallow carbonate banks (Fig. 3). The interval spanning from the lower Miocene through the base of the upper Miocene (Fig. 3), ranging from 300 to 696 mbsf (the bottom of the recovered section), comprises different lithostratigraphic subunits (Subunits IC, ID, IIA, and IIB) (see Fig. 3) determined on board ship on the basis of sedimentologic criteria, magnetic susceptibility, color reflectance, and carbonate content (Sigurdsson, Leckie, Acton, et al., 1997). The investigated interval at Site 1000 ranges from 370 to 696 mbsf.