Geochemistry on manganese nodules from Timor

Fossil Mn nodules of Cretaceous age from western Timor exhibit chemical, structural and radioisotope compositions consistent with their being of deep-sea origin. These nodules show characteristics similar to nodules now found at depths of 3,500-5,000 m in the Pacific and Indian Oceans. Slight differences in the fine structure and chemistry of these nodules and modern deep-sea nodules are attributed to diagenetic alteration after uplift of enclosing sediments.

Calcite accumulation in the eastern equatorial Pacific

The eastern equatorial Pacific (EEP) is an important center of biological productivity, generating significant organic carbon and calcite fluxes to the deep ocean. We reconstructed paleocalcite flux for the past 30,000 years in four cores collected beneath the equatorial upwelling and the South Equatorial Current (SEC) by measuring ex230Th-normalized calcite accumulation rates corrected for dissolution with a newly developed proxy for "fraction of calcite preserved". This method produced very similar results at the four sites and revealed that the export flux of calcite was 30-50% lower during the LGM compared to the Holocene. The internal consistency of these results supports our interpretation, which is also in agreement with emerging data indicating lower glacial productivity in the EEP, possibly as a result of lower nutrient supply from the southern ocean via the Equatorial Undercurrent. However, these findings contradict previous interpretations based on mass accumulation rates (MAR) of biogenic material in the sediment of the EEP, which have been taken as reflecting higher glacial productivity due to stronger wind-driven upwelling.

Radioisotopes and He accumulation in deep sea sediments of the Ontong Java Plateau

The accumulation of extraterrestrial 3He, a tracer for interplanetary dust particles (IDPs), in sediments from the Ontong Java Plateau (OJP; western equatorial Pacific Ocean) has been shown previously to exhibit a regular cyclicity during the late Pleistocene, with a period of ~100 ka. Those results have been interpreted to reflect periodic variability in the global accretion of IDPs that, in turn, has been linked to changes in the inclination of Earth's orbit with respect to the invariable plane of the solar system. Here we show that the accumulation in OJP sediments of authigenic 230Th, produced by radioactive decay of 234U in seawater, exhibits a 100-ka cyclicity similar in phase and amplitude to that evident in the 3He record. We interpret the similar patterns of 230Th and 3He accumulation to reflect a common origin within the ocean-climate system. Comparing spatial and temporal patterns of sediment accumulation against regional patterns of biological productivity and against the well-established pattern of CaCO3 dissolution in the deep Pacific Ocean leads to the further conclusion that a common 100-ka cycle in accumulation of biogenic, authigenic and extraterrestrial constituents in OJP sediments reflects the influence of climate-related changes in sediment focusing, rather than changes in the rate of production or supply of sedimentary constituents.

(Table 2) Uranium series results of Villars Cave stalagmite Vil-stm14

We present a new high resolution speleothem stable isotope record from the Villars Cave (SW-France) that covers part of marine isotope stage (MIS) 3. The Vil14 stalagmite grew between ~52 and 29 ka. The d13C profile is used as a palaeoclimate proxy and clearly shows the interstadial substages 13, 12 and 11. The new results complement and corroborate previously published stalagmite records Vil9 and Vil27 from the same site. The Vil14 stalagmite chronology is based on 12 Th-U dating by MC-ICP-MS and 3 by TIMS. A correction for detrital contamination was done using the 230Th/232Th activity ratio measured on clay collected in Villars Cave. The Vil14 results reveal that the onset of Dansgaard-Oeschger (DO) events 13 and 12 occurred at ~49.8 ka and ~47.8 ka, respectively. Within uncertainties, this is coherent with the latest NorthGRIP time scale (GICC05-60 ka) and with speleothem records from Central Alps. Our data show an abrupt d13C increase at the end of DO events 14 to 12 which coincides with a petrographical discontinuity probably due to a rapid cooling. As observed for Vil9 and Vil27, Vil14 growth significantly slowed down after ~ 42 ka and finally stopped ~ 29 ka ago where the d13C increase suggests a strong climate deterioration that coincides with both North Atlantic sea level and sea surface temperature drop.