(Table 2) Stratigraphic marker taxa in ODP Hole 162-985A sediments

The rich and diverse dinocyst assemblages in Cores 162-985A-32X through 62X confirm the importance of these microfossils in unraveling the evolution of the Norwegian Sea. Cosmopolitan taxa, with well-documented stratigraphic ranges in northwest Europe, indicate the following ages: Sections 162-985A-62X-1 through 51X-2, Rupelian (early Oligocene); 50X-5, Oligocene, possibly Chattian; 48X-6, Aquitanian? (early Miocene); 48X-4 through 37X-5, Aquitanian (early Miocene); and 36X-5 through 32X-1, Burdigalian (early Miocene). This stratigraphic interpretation suggests that a major hiatus, which can be correlated with an apparently coeval hiatus at Site 643, occurs within the Chattian at Site 985. Several endemic dinocyst taxa with unusual morphology and restricted stratigraphic occurrences are present in Hole 985A and other Norwegian Sea sites, especially Site 643. By using Hole 985A data for control, the Oligocene-Miocene sediments can be correlated with some degree of confidence in the Norwegian Basin.

(Table 2) Revised stacked record on magnetic susceptibility of ODP Site 162-984 sediments

Magnetic field and susceptibility data were collected using the geological high-resolution magnetometer tool string (GHMT) at three sites during Ocean Drilling Program Leg 162. Postcruise processing of the magnetic field data yielded a polarity stratigraphy for Holes 986C and 987E. A magnetic susceptibility record was measured at Hole 984B. Detailed analysis of the core and log susceptibility records at Hole 984B yielded an empirical tool resolution of the susceptibility measurement tool (SUMT) of 53 cm. At Site 984, where sedimentation rates were typically >10 cm/k.y., this gave a resolution of at least ~5000 yr. This data report summarizes the GHMT postcruise processing, method of interpretation, and analysis of the SUMT resolution.

Stable isotope analysis and temperature reconstruction data from DSDP Hole 94-609B and ODP Hole 162-984B

The Greenland ice sheet is accepted as a key factor controlling the Quaternary glacial scenario. However, the origin and mechanisms of major Arctic glaciation starting at 3.15 Ma and culminating at 2.74 Ma are still controversial. For this phase of intense cooling Ravelo et al. proposed a complex gradual forcing mechanism. In contrast, our new submillennial-scale paleoceanographic records from the Pliocene North Atlantic suggest a far more precise timing and forcing for the initiation of northern hemisphere glaciation (NHG), since it was linked to a 2-3 °C surface water warming during warm stages from 2.95 to 2.82 Ma. These records support previous models, claiming that the final closure of the Panama Isthmus (3.0- ~2.5 Ma induced an increased poleward salt and heat transport. Associated strengthening of North Atlantic Thermohaline Circulation and in turn, an intensified moisture supply to northern high latitudes resulted in the build-up of NHG, finally culminating in the great, irreversible climate crash at marine isotope stage G6 (2.74 Ma). In summary, there was a two-step threshold mechanism that marked the onset of NHG with glacial-to-interglacial cycles quasi-persistent until today.

Revised depth scale, splice tie points and chron boundaries of ODP Hole 151-907A and Site 162-907

The magnetic polarity stratigraphy at Site 907 obtained from the shipboard pass-through magnetometer and from discrete samples is readily interpretable back to the onset of the Gilbert Chron (5.89 Ma). From this level to the base of the section at ~14 Ma, the interpretation is corroborated by silicoflagellate datums with predictable correlation to polarity chrons. The resulting magnetostratigraphic interpretation differs from those proposed in the Leg 151 (Hole 907A) and 162 (Holes 907B and 907C) Initial Reports volumes. An important hiatus in the 7-10 Ma interval at Site 907 caused sedimentation to slow or cease for ~2.7 m.y. We have revised the shipboard correlation among the three holes at Site 907, resulting in a new composite section splice and recalculation of composite depths. For Site 985, magnetostratigraphic interpretation is possible down to ~150 meters below seafloor (mbsf) (C3An/C3Ar) at ~6 Ma. There are no useful biostratigraphic datums from Site 985 to support this interpretation; however, the interpretation is supported by the correlation of Sites 985 and 907 using natural gamma data from the shipboard multisensor track. Below ~150 mbsf at Site 985, drilling-related deformation at the onset of extended core barrel drilling precluded magnetostratigraphic interpretation.

(Figure 2) Organic carbon content, stable isotope ratios, TEX86 index and sea surface temperature reconstruction for the early Aptian of ODP Hole 198-1207B

The Cretaceous has long been recognized as a time when greenhouse conditions were fueled by elevated atmospheric CO2 and accompanied by perturbations of the global carbon cycle described as oceanic anoxic events (OAEs). Yet, the magnitude and frequency of temperature change during this interval of warm and equable climate are poorly constrained. Here we present a high-resolution record of sea-surface temperatures (SSTs) reconstructed using the TEX86 paleothermometer for a sequence of early Aptian organic-rich sediments deposited during the first Cretaceous OAE (OAE1a) at Shatsky Rise in the tropical Pacific. SSTs range from ~30 to ~36 °C and include two prominent cooling episodes of ~4 °C. The cooler temperatures reflect significant temperature instability in the tropics likely triggered by changes in carbon cycling induced by enhanced burial of organic matter. SST instability recorded during the early Aptian in the Pacific is comparable to that reported for the late Albian-early Cenomanian in the Atlantic, suggesting that such climate perturbations may have recurred during the Cretaceous with concomitant consequences for biota and the marine environment.