ALBERT

Description: This report presents mineralogic and geochemical data from Ocean Drilling Program Leg 182 Site 1128 in the Great Australian Bight. Clay mineralogy is dominated by mixed-layer illite-smectite, followed by minor amounts of kaolinite and illite, with intervals of pure smectite. Carbonate mineralogy is exclusively low-Mg calcite, except for one interval of dolomite in lower Oligocene sediments. Carbonate increases significantly in upper Eocene sediments, decreases through the lower Oligocene, then increases again in the Neogene. Quartz is present as a minor component that covaries inversely with carbonate. High-resolution sampling associated with Chron 13 normal (early Oligocene) reveals high-frequency (~23 k.y.) fluctuations in clay mineralogy and carbonate abundance and a positive oxygen and carbon isotope excursion (in bulk carbonates) related to Antarctic glaciation.

Description: We investigated surface and deep ocean variability in the subpolar North Atlantic from 1000 to 500 thousand years ago (ka) based on two Ocean Drilling Program (ODP) sites, Feni drift site 980 (55°29'N, 14°42'W) and Bjorn drift site 984 (61°25'N, 24°04'W). Benthic foraminiferal stable isotope data, planktic foraminiferal faunas, ice-rafted debris data, and faunally based sea-surface temperature estimates help test the hypothesis that oceanographic changes in the North Atlantic region were associated with the onset of the 100-kyr world during the mid-Pleistocene revolution. Based on percentage of Neogloboquadrina pachyderma (s) records from both sites, surface waters during interglacials and glacials were cooler in the mid-Pleistocene than during marine isotope stages (MIS) 5 and 6. In particular, interglaciations at Bjorn drift site 984 were significantly cooler. Faunal evidence suggests that the interglacial Arctic front shifted from a position between the two sites to a position northwest of Bjorn drift site 984 after ca. 610 ka. As during the late Pleistocene, we find faunal evidence for lagging surface warmth at most of the glacial initiations during the mid-Pleistocene. Each initiation is associated with high benthic d13C values that are maintained into the succeeding glaciation, which we term “lagging NADW production.” These findings indicate that lagging warmth and lagging NADW production are robust features of the regional climate system that persist in the middle to late Pleistocene.

Description: During Ocean Drilling Program (ODP) Leg 162, five sites were drilled in the subpolar North Atlantic (Sites 980-984), three sites in the Nordic Seas (Sites 985-987), and two holes at Iceland Sea Site 907 (first drilled during ODP Leg 151). Carbonate sediments at the subpolar sites have generally common to abundant and well-preserved planktonic foraminifers, especially at Feni Drift Sites 980/981 and Rockall Plateau Site 982. Gardar Drift Site 983 and Bjorn Drift Site 984 featured greater concentrations of clay material and ice-rafted debris, diluting carbonate material in some intervals (particularly before ~1.8 Ma at Site 984). Nordic Seas Sites 907 and 985-987 feature generally rare to common and moderately well-preserved planktonic foraminifers only within the past 1 m.y., although Pliocene taxa are sparsely recorded at Site 986 on the Svalbard margin. Planktonic foraminifer datum levels are located to the section level where possible for the subpolar North Atlantic sites. Comparison to an integrated magnetostratigraphy and calcareous nannofossil stratigraphy shows that several datum levels are synchronous to within 5% of their published ages. In particular, the start of the Neogloboquadrina pachyderma (sinistral) Acme Zone (1.8 Ma), the first occurrence (FO) of Globorotalia inflata (2.09 Ma), the last occurrence (LO) of Globorotalia cf. crassula (3.3 Ma), and the FO of Globorotalia puncticulata (4.5 Ma) are judged synchronous in eastern sections of the subpolar North Atlantic. The LO of Neogloboquadrina atlantica (sinistral) occurs ~100-200 k.y. later relative to its mid-latitude North Atlantic age (2.41 Ma).