(Table 1) Summary of general lithology in IODP Exp302 cores

The Cenozoic ice-rafted debris (IRD) history of the central Arctic is reconstructed utilizing the terrigenous coarse sand fraction in IODP 302 cores from 0 to 273 meters composite depth. This Holocene - middle Eocene quantitative record of terrigenous sand accumulation on the Lomonosov Ridge, along with qualitative information on grain texture and composition, confirms the interpretation that ice initiation (sea ice and glacial ice) occurred ~46 Ma in the Arctic, and provides a long-term pattern of Arctic ice expansion and decay since the middle Eocene. IRD mass accumulation rates range from 0 to 0.13 g/cm2/ka in the middle Eocene and from 0 to 0.36 g/cm2/ka in the Neogene. IRD mass accumulation rate (MAR) maxima in the Miocene and Pliocene cooccur with either glacial initiation or intensification in the sub-Arctic. The 46.25 Ma IRD onset in the central Arctic slightly precedes the earliest evidence of ice in the Antarctic, and compares in timing with a >1000 ppm decrease in atmospheric concentrations of CO2. The decline of pCO2 in the middle Eocene may have driven both poles across the temperature threshold that enabled the nucleation of glaciers on land and partial freezing of the surface Arctic Ocean, especially during times of low insolation.

Foraminifer counts in core JM01-1199, and review of radiocarbon ages in the Norwegian-Barents Sea-Svalbard margin

We compare six high-resolution Holocene, sediment cores along a S-N transect on the Norwegian-Svalbard continental margin from ca 60°N to 77.4°N, northern North Atlantic. Planktonic foraminifera in the cores were investigated to show the changes in upper surface and subsurface water mass distribution and properties, including summer sea-surface temperatures (SST). The cores are located below the axis of the Norwegian Current and the West Spitsbergen Current, which today transport warm Atlantic Water to the Arctic. Sediment accumulation rates are generally high at all the core sites, allowing for a temporal resolution of 10-102 years. SST is reconstructed using different types of transfer functions, resulting in very similar SST trends, with deviations of no more than +- 1.0/1.5 °C. A transfer function based on the maximum likelihood statistical approach is found to be most relevant. The reconstruction documents an abrupt change in planktonic foraminiferal faunal composition and an associated warming at the Younger Dryas-Preboreal transition. The earliest part of the Holocene was characterized by large temperature variability, including the Preboreal Oscillations and the 8.2 k event. In general, the early Holocene was characterized by SSTs similar to those of today in the south and warmer than today in the north, and a smaller S-N temperature gradient (0.23 °C/°N) compared to the present temperature gradient (0.46 °C/°N). The southern proxy records (60-69°N) were more strongly influenced by slightly cooler subsurface water probably due to the seasonality of the orbital forcing and increased stratification due to freshening. The northern records (72-77.4°N) display a millennial-scale change associated with reduced insolation and a gradual weakening of the North Atlantic thermohaline circulation (THC). The observed northwards amplification of the early Holocene warming is comparable to the pattern of recent global warming and future climate modelling, which predicts greater warming at higher latitudes. The overall trend during mid and late Holocene was a cooling in the north, stable or weak warming in the south, and a maximum S-N SST gradient of ca 0.7 °C/°N at 5000 cal. years BP. Superimposed on this trend were several abrupt temperature shifts. Four of these shifts, dated to 9000-8000, 5500-3000 and 1000 and ~400 cal. years BP, appear to be global, as they correlate with periods of global climate change. In general, there is a good correlation between the northern North Atlantic temperature records and climate records from Norway and Svalbard.

Sedimentological and clay mineralogical analysis of ODP sites in the central Fram Strait

This study presents the results of high-resolution sedimentological and clay mineralogical investigations on sediments from ODP Sites 908A and 909AlC located in the central Fram Strait. The objective was to reconstruct the paleoclimate and paleoceanography of the high northern latitudes since the middle Miocene. The sediments are characterised in particular by a distinctive input of ice-rafted material, which most probably occurs since 6 Ma and very likely since 15 Ma. A change in the source area at 1 1.2 Ma is clearly marked by variations within clay mineral composition and increasing accumulation rates. This is interpreted as a result of an increase in water mass exchange through the Fram Strait. A further period of increasing exchange between 4-3 Ma is identified by granulometric investigations and points to a synchronous intensification of deep water production in the North Atlantic during this time interval. A comparison of the components of coarse and clay fraction clearly shows that both are not delivered by the Same transport process. The input of the clay fraction can be related to transport mechanisms through sea ice and glaciers and very likely also through oceanic currents. A reconstruction of source areas for clay minerals is possible only with some restrictions. High smectite contents in middle and late Miocene sediments indicate a background signal produced by soil formation together with sediment input, possibly originating from the Greenland- Scotland Ridge. The applicability of clay mineral distribution as a climate proxy for the high northern latitudes can be confirmed. Based on a comparison of sediments from Site 909C, characterised by the smectite/illite and chlorite ratio, with regional and global climatic records (oxygen isotopes), a middle Miocene cooling phase between 14.8-14.6 Ma can be proposed. A further cooling phase between 10-9 Ma clearly shows similarities in its Progress toward drastic decrease in carbonate sedimentation and preservation in the eastern equatorial Pacific. The modification in sea water and atmosphere chemistry may represent a possible link due to the built-up of equatorial carbonate platforms. Between 4.8-4.6 Ma clay mineral distribution indicates a distinct cooling trend in the Fram Strait region. This is not accompanied by relevant glaciation, which would otherwise be indicated by the coarse fraction. The intensification of glaciation in the northern hemisphere is distinctly documented by a rapid increase of illite and chlorite starting from 3.3 Ma, which corresponds to oxygen isotope data trends from North Atlantic.

Planktonic foraminifera of the Mediterranean Sea

A high-resolution biochronology is presented for the Late Quaternary of the central Mediterranean. In the Late Pleistocene-Holocene successions three assemblage zones are distinguished on the basis of frequency patterns of planktic foraminifera. The age of these zones is determined by Accelerator Mass Spectrometry (AMS)14C dating. The zonal boundaries are dated at 12,700 yr B.P. (the end of Termination Ia) and 9600 yr B.P. (the start of Termination Ib), respectively. The AMS dates show that major changes in the planktic and benthic realms occurred synchronously over wide areas, although records of individual species may show important regional differences. In the studied areas, resedimentation processes revealed by anomalous successions of14C dates, play a far more important role than indicated by the sedimentological and micropaleontological data. Possibly these processes contribute to the very high accumulation rates in the glacial Zone III. Although the AMS technique has increased the accuracy of14C-measurements, admixture of older carbonate may still lead to substantial age differences between areas with different sedimentary regimes.