Benthic foraminifera and stable isotope record of ODP Leg 182 sites

Cores from Sites 1129, 1131, and 1132 (Ocean Drilling Program (ODP) Leg 182) on the uppermost slope at the edge of the continental shelf in the Great Australian Bight reveal the existence of upper Pleistocene bryozoan reef mounds, previously only detected on seismic lines. Benthic foraminiferal oxygen isotope data for the last 450,000 years indicate that bryozoan reef mounds predominantly accumulated during periods of lower sea level and colder climate since stage 8 at Sites 1129 and 1132 and since stage 4 at the deeper Site 1131. During glacials and interstadials (stages 2-8) the combination of lowered sea level, increased upwelling, and absence of the Leeuwin Current probably led to an enhanced carbon flux at the seafloor that favored prolific bryozoan growth and mound formation at Site 1132. At Site 1129, higher temperatures and downwelling appear to have inhibited the full development of bryozoan mounds during stages 2-4. During that time, favorable hydrographic conditions for the growth of bryozoan mounds shifted downslope from Site 1129 to Site 1131. Superimposed on these glacial-interglacial fluctuations is a distinct long-term paleoceanographic change. Prior to stage 8, benthic foraminiferal assemblages indicate low carbon flux to the seafloor, and bryozoan mounds, although present closer inshore, did not accumulate significantly at Sites 1129 and 1132, even during glacials. Our results show that the interplay of sea level change (eustatic and local, linked to platform progradation), glacial-interglacial carbon flux fluctuations (linked to local hydrographic variations), and possibly long-term climatic change strongly influenced the evolution of the Great Australian Bight carbonate margin during the late Pleistocene.

Upper Cretaceous agglutinated foraminifers from the western Pacific Ocean

Abyssal agglutinated foraminifers allow biostratigraphic correlation of Upper Cretaceous brown zeolitic claystones in Deep Sea Drilling Project Holes 196A and 198A and Ocean Drilling Program Holes 800A and 801 A. Three agglutinated foraminiferal zones subdivide the strata overlying the Campanian to Cenomanian cherts. The lower zone is characterized by Hormosina gigantea, which is a Campanian zonal marker in the North Atlantic Ocean and western Tethys. A major correlation level, which was observed in all holes studied, is based on the acme of evolute Haplophragmoides spp. This acme zone was observed in Sample 129-801A-6R-CC, about 9 m above the first occurrence of H. gigantea in Sample 129-801A-7R-1, 62-67 cm (approximately middle Campanian). The uppermost zone is characterized by dominant Paratrochamminoides spp. and in some instances common Bolivinopsis parvissimus (late Campanian to Maestrichtian). The available biostratigraphic data for the Upper Cretaceous of Sites 196, 198, 800, and 801 are correlated with the biochronologic framework of the North Atlantic, western Mediterranean, and Carpathians. Additionally, we use quantitative estimates of the diversity and abundance of agglutinated foraminiferal species to monitor general faunal trends with time in the western Pacific.