(Table 1) K and Ar content, and age determination of ODP Holes 126-792E and 126-793B

Results of conventional K-Ar dating on five samples from two sites from the Izu-Bonin forearc are presented. Two samples recovered from a volcanic edifice and overlying sediments drilled on the western side of the forearc basin (Site 792) indicate a basement age of 34 Ma. This is consistent with early Oligocene biostratigraphic ages from the overlying sediments. Three samples from the basement of Hole 793B at the center of the basin are not analytically distinguishable, with a best age of 27.1 +/- 0.6 Ma. This is slightly younger than the 30-33 Ma biostratigraphic and magnetostratigraphic estimates from the overlying sediments, suggesting that alteration processes have lowered the apparent K-Ar ages. These ages suggest that syn-rift volcanism occurred in a forearc location during the middle Oligocene.

Stable isotope record, Mg/Ca ratios and age model of St. Stephens Quarry, Alabama

In the largest global cooling event of the Cenozoic Era, between 33.8 and 33.5 Myr ago, warm, high-CO2 conditions gave way to the variable 'icehouse' climates that prevail today. Despite intense study, the history of cooling versus ice-sheet growth and sea-level fall reconstructed from oxygen isotope values in marine sediments at the transition has not been resolved. Here, we analyse oxygen isotopes and Mg/Ca ratios of benthic foraminifera, and integrate the results with the stratigraphic record of sea-level change across the Eocene-Oligocene transition from a continental-shelf site at Saint Stephens Quarry, Alabama. Comparisons with deep-sea (Sites 522 (South Atlantic) and 1218 (Pacific)) d18O and Mg/Ca records enable us to reconstruct temperature, ice-volume and sea-level changes across the climate transition. Our records show that the transition occurred in at least three distinct steps, with an increasing influence of ice volume on the oxygen isotope record as the transition progressed. By the early Oligocene, ice sheets were ~25% larger than present. This growth was associated with a relative sea-level decrease of approximately 105 m, which equates to a 67 m eustatic fall.

Age determination of sediment cores from the western Svalbard margin

The deglaciation of the continental shelf to the west of Spitsbergen and the main fjord, Isfjorden, is discussed based on sub-bottom seismic records and sediment cores. The sea floor on the shelf to the west of Isfjorden is underlain by less than 2 m of glaciomarine sediments over a firm diamicton interpreted as till. In central Isfjorden up to 10 m of deglaciation sediments were recorded, whereas in cores from the innermost tributary, Billefjorden, less than a meter of ice proximal sediments was recognized between the till and the 'normal' Holocene marine sediments. We conclude that the Barents Sea Ice Sheet terminated along the shelf break during the Late Weichselian glacial maximum. Radiocarbon dates from the glaciomarine sediments above the till indicate a stepwise deglaciation. Apparently the ice front retreated from the outermost shelf around 14.8 ka. A dramatic increase in the flux of line-grained glaciomarine sediments around 13 ka is assumed to reflect increased melting and/or current activity due to a climatic warming. This second stage of deglaciation was interrupted by a glacial readvance culminating on the mid-shelf area shortly after 12.4 ka. The glacial readvance, which is correlated with a simultaneous readvance of the Fennoscandian ice sheet along the western coast of Norway, is attributed to the so-called 'Older Dryas' cooling event in the North Atlantic region. Following this glacial readvance the outer part of Isfjorden became rapidly deglaciated around 12.3 ka. During the Younger Dryas the inner fjord branches were occupied by large outlet glaciers and possibly the ice front terminated far out in the main fjord. The remnants of the Barents Sea Ice Sheet melted quickly away as a response to the Holocene warming around 10 ka.

Age determination of ODP Hole 145-887

Atmospheric carbon dioxide concentrations were significantly lower during glacial periods than during intervening interglacial periods, but the mechanisms responsible for this difference remain uncertain. Many recent explanations call on greater carbon storage in a poorly ventilated deep ocean during glacial periods (Trancois et al., 1997, doi:10.1038/40073; Toggweiler, 1999, doi:10.1029/1999PA900033; Stephens and Keeling, 2000, doi:10.1038/35004556; Marchitto et al., 2007, doi:10.1126/science.1138679; Sigman and Boyle, 2000, doi:10.1038/35038000), but direct evidence regarding the ventilation and respired carbon content of the glacial deep ocean is sparse and often equivocal (Broecker et al., 2004, doi:10.1126/science.1102293). Here we present sedimentary geochemical records from sites spanning the deep subarctic Pacific that -together with previously published results (Keigwin, 1998, doi:10.1029/98PA00874)- show that a poorly ventilated water mass containing a high concentration of respired carbon dioxide occupied the North Pacific abyss during the Last Glacial Maximum. Despite an inferred increase in deep Southern Ocean ventilation during the first step of the deglaciation (18,000-15,000 years ago) (Marchitto et al., 2007, doi:10.1126/science.1138679; Monnin et al., 2001, doi:10.1126/science.291.5501.112), we find no evidence for improved ventilation in the abyssal subarctic Pacific until a rapid transition ~14,600 years ago: this change was accompanied by an acceleration of export production from the surface waters above but only a small increase in atmospheric carbon dioxide concentration (Monnin et al., 2001, doi:10.1126/science.291.5501.112). We speculate that these changes were mechanistically linked to a roughly coeval increase in deep water formation in the North Atlantic (Robinson et al., 2005, doi:10.1126/science.1114832; Skinner nd Shackleton, 2004, doi:10.1029/2003PA000983; McManus et al., 2004, doi:10.1038/nature02494), which flushed respired carbon dioxide from northern abyssal waters, but also increased the supply of nutrients to the upper ocean, leading to greater carbon dioxide sequestration at mid-depths and stalling the rise of atmospheric carbon dioxide concentrations. Our findings are qualitatively consistent with hypotheses invoking a deglacial flushing of respired carbon dioxide from an isolated, deep ocean reservoir periods (Trancois et al., 1997, doi:10.1038/40073; Toggweiler, 1999, doi:10.1029/1999PA900033; Stephens and Keeling, 2000, doi:10.1038/35004556; Marchitto et al., 2007, doi:10.1126/science.1138679; Sigman and Boyle, 2000, doi:10.1038/35038000; Boyle, 1988, doi:10.1038/331055a0), but suggest that the reservoir may have been released in stages, as vigorous deep water ventilation switched between North Atlantic and Southern Ocean source regions.

Age determination of equatorial Pacific sediments

Radiocarbon age differences for pairs of coexisting late glacial age benthic and planktic foraminifera shells handpicked from 10 sediment samples from a core from a depth of 2.8 km in the western equatorial Pacific are not significantly different from that of 1600 years calculated from measurements on prenuclear seawater. This places a lower limit on the depth of the interface for the hypothetical radiocarbon-depleted glacial age seawater reservoir required to explain the 190 per mil drop in the 14C/C for atmospheric CO2, which occurred during the mystery interval (17.5 to 14.5 calendar years ago). These measurements restrict the volume of this reservoir to be no more than 35% that of the ocean. Further, 14C measurements on a single Last Glacial Maximum age sample from a central equatorial Pacific core from a depth of 4.4 km water fail to reveal evidence for the required 5- to 7-kyr age difference between benthic and planktic foraminifera shells if the isolated reservoir occupied only one third of the ocean. Nor does the 13C record for benthic forams from this abyssal core yield any evidence for the excess respiration CO2 expected to be produced during thousands of years of isolation. Nor, as indicated by the presence of benthic foraminifera, was the dissolved oxygen used up in this abyssal water.

(Table 1) Luminescence age determination of sediments from the Arkhangelsk area

The Arkhangelsk area lies in the region that was reached by the northeastern flank of the Scandinavian ice sheet during the last glaciation. Investigations of Late Pleistocene sediments show interglacial terrestrial and marine conditions with sea level up to 52 m above the present level. An unconformity in the stratigraphy suggests a hiatus representing the Early Valdaian (Weichselian) and the beginning of the Middle Valdaian. This unconformity could be related to a low base level and isostatic depression of the area north of Arkhangelsk, either caused by ice masses advancing from the Kara and Barents ice sheets and/or to Scandinavian ice over the Kola Peninsula. During Middle Valdaian, from c. 66 ka BP, until the advance of the Late Valdaian glacier, c. 17-16 ka BP, peat formation, and northward fluvial sedimentation occurred coexisting with permafrost conditions in a later phase. Before the glacier advance, the base level rose and thick vertical accumulations of fluvial sediments were formed. Associated with this glacier advance from the north-northwest, ice damming occurred. Fluvial drainage was opposite to the present drainage pattern and deposition appeared in glaciolacustrine ponds in the area outside the limit of the glaciation. After the deglaciation that started c. 15 ka BP, permafrost conditions and downwasting of buried stagnant glacier ice prevailed until at least 10.7 ka BP.