Maastrichtian foraminiferal and paleoceanographic changes on Milankovitch timescales

Milankovitch-scale alternations in Maastrichtian hemipelagic strata from Oc ean Drilling Program Hole 1050C (Blake Nose) provide a natural experiment o f paleoceanography and foraminiferal paleoecology in a tropical/subtropical greenhouse ocean. Cycles are 30-50 cm thick and thought to reflect the sim ilar to 21 kyr precessional cycle. High planktic delta O-18 values are corr elated with high planktic but low benthic delta C-13 values, indicating tha t cooler and/or more saline surface waters were associated with higher prod uctivity. High-productivity intervals are also characterized by high Ca con centrations; enrichment in feldspar and kaolinite; and high relative abunda nce of Heterohelix spp., Globigerinelloides spp., and Laeviheterohelix glab rans, Conversely, low-productivity intervals have low planktic delta O-18 v alues; high Fe and Ti concentrations; enrichment in quartz, illite, and chl orite; and relative increases in Globotruncana spp, and Pseudoguembelina sp p. Potential forcing mechanisms for observed covariation include cyclic var iation in water column stratification, variation in continental nutrient fl uxes, and changes in the intensity of upwelling.