(Table 2) Hydrogen sulphide and methane content, and loss on ignition in sediments obtained in the Gotland Deep, Baltic Sea

The distribution of methane and hydrogen sulfide concentrations in sediments of various basins of the Baltic Sea was investigated during 4 cruises in 1995 and 1996. Significant differences in the concentrations of both compounds were recorded between the basins and also between different areas within the Gotland Deep. High-methane sediments with distinctly increasing concentrations from the surface to deeper layers were distinguished from low-methane sediments without a clear gradient. Methane concentrations exhibited a fair correlation with the sediment accumulation rate, determined by measuring the total thickness of the post-Ancylus Holocene sequence on echosounding profiles in the Gotland Deep. Only weak correlations were observed with the content of organic matter in the surface layers of the sediments. Hydrogen sulfide concentrations in the sediments showed a positive correlation with methane concentrations, but, in contrast to methane concentrations, were strongly influenced by the transition from oxic to anoxic conditions in the water column between 1995 and 1996. Sediments in the deepest part of the Gotland Basin (>237 m water depth), covering an area of approximately 35 km**2, were characterized by especially high accumulation rates (>70 cm/ka) and high methane and hydrogen sulfide contents. Concentrations of these compounds decreased rapidly towards the slope of the basin.

Element abundances, loss on ignition, total analyzed abundances, CIA values, and Al-oxide/Ti-oxide ratios of sediment core CRP-2A (Table1)

The CRP-2/2A core, drilled in western McMurdo Sound in October and November 1998, penetrated 624 m of Quaternary. Pliocene, lower Miocene, and Oligocene glacigenic sediments. The palaeoclimatic record of CRP-2/2A is examined using major element analyses of bulk core samples of fine grained sediments (mudstones and siltstones) and the Chemical Index of Alteration (CIA) of Nesbitt & Young (1982). The CIA is calculated from the relative abundances of AI, K, Ca, and Na oxides, and its magnitude increases as the effects of chemical weathering increase. However, changes in sediment provenance can also affect the CIA, and provenance changes are recorded by shifts in the Al2O3/TiO2 ratios and the Nb contents of these CRP-2/2A mudstones. Relatively low CIA values (40-50) occur throughout the CRP-2/2A sequence, whereas the Al2O3/TiO2 ratio decreases upsection. The major provenance change is an abrupt onset of McMurdo Volcanic Group detritus at ~300 mbsf and is best characterized by a rapid increase in Nb content in the sediments. This provenance shift is not evident in the CIA record, suggesting that a contribution from the Ferrar Dolerite to the older sediments was replaced by an input of McMurdo Volcanic Group material in the younger sediments. If this is true, then the relatively uniform CIA values indicate relatively consistent palaeoweathering intensities throughout the Oligocene and early Miocene in the areas that supplied sediment to CRP-2/2A.