Mollusca

The surf clams Mesodesma mactroides Reeve, 1854 and Donax hanleyanus Philippi, 1847 are the two dominating species in macrobenthic communities of sandy beaches off northern Argentina, with the latter now surpassing M. mactroides populations in abundance and biomass. Before stock decimation caused by exploitation (during the 1940s and 1950s) and mass mortality events (1995, 1999 and 2007) M. mactroides was the prominent primary consumer in the intertidal ecosystem and an important economic resource in Argentina. Since D.

Fifteen surface sediment samples from the Pakistan shelf and upper continental slope and a Late Quaternary high-sedimentation rate core (573 m water depth, Pakistan continental margin) have been analysed to improve the understanding of the factors influencing pteropod preservation. The aragonite compensation depth (ACD) is located at 250-400 m water depth, which corroborates previous observations of a very shallow ACD in the northern Arabian Sea. With the exception of the Hab transect off Karachi, the ACD coincides with the upper boundary of the OMZ located at 250 m water depth.

Bivalve shells from the CRP-l drillhole, Cape Roberts (Victoria Land Basin), have been analysed for their stable isotope composition to obtain information on Antarctic coastal palaeoceanography during the middle Pleistocene and early Miocene. Shells from a middle Pleistocene carbonate-rich unit (lithostratigraphic Unit 3.1; 33.82-3 1.89 metres below sea floor) have d180 values between +3.64 and +4.56 per mil PDB and d13C between +0.85 and + 1.09 per mil PDB. Oxygen isotopic compositions are close to or at equilibrium conditions with scawater at a temperature in the range of c.

In order to better understand Late Quaternary pelagic aragonite preservation in the western Arabian Sea we have investigated a high-resolution sediment core 905 off Somalia. Pteropod preservation is enhanced in times of reduced monsoon-driven productivity, indicated by low amounts of Corg and low barium to aluminium (Ba/Al) ratios. All periods corresponding to Heinrich events in the North Atlantic are represented by maxima in shell preservation of the common pteropod Limacina inflata (LDX values <2, except for H5-equivalent with a poorer shell preservation, LDX >2.66).

Surface samples and nine cores from the western Baltic Sea and marginal water bodies were investigated for clay mineral composition. The clay mineral assemblages of recent sediments are rather homogeneous. Variations result mainly from the erosion of different glacial source deposits. High percentages of illite and low kaolinite/chlorite and quartz/feldspar ratios are characteristic for this glacial source. Advection of kaolinite-rich suspensions from the North Sea is believed to account for higher kaolinite/chlorite ratios in the Mecklenburg Bight.

Inoceramus is an epibenthic bivalve which lived in a wide variety of paleoenvironments encompassing a broad range of paleodepths. A survey of all Cretaceous sediments from Deep Sea Drilling Project legs 1-69 and 75 revealed over 500 Inoceramus specimens at twenty sites. Of these, 47 well-preserved Late Cretaceous specimens from the South Atlantic, Pacific and Indian Oceans were analyzed for oxygen and carbon isotopes. The specimens exhibit small internal isotopic variability and oxygen isotopic paleotemperatures that are consistent with a deep-sea habitat.

87Sr/86Sr data of belemnites are presented from a Middle Jurassic-Early Cretaceous succession from the Falkland Plateau (Deep Sea Drilling Project Sites 511 and 330) that was deposited in a periodically anoxic, semi-enclosed shallow water basin. Diagenetically screened strontium-isotope values of 0.706789 rise to 0.707044 before increasing sharply to 0.707428 in the uppermost part of the sampled succession.

We present a revised 87Sr/86Sr-curve for marine-Sr in the interval 2.5-4.5 Ma using analysis of Orbulina universa from the Middle Pliocene type section in Sicily (Punta Piccola section) and a mixed assemblage of planktonic foraminifera from ODP Site 758A and B. The new calibration is used, together with new 87Sr/86Sr analysis of pectenid calcite from Cockburn Island, Antarctica, to confirm an age of 4.7 Ma for the pectenids of the Cockburn Island Formation (formerly the Pecten Conglomerate), a unit important in marking a period of warmth and possible glacial retreat in Antarctica.

The surf clams Mesodesma mactroides Reeve, 1854 and Donax hanleyanus Philippi, 1847 are the two dominating species in macrobenthic communities of sandy beaches off northern Argentina, with the latter now surpassing M. mactroides populations in abundance and biomass. Before stock decimation caused by exploitation (during the 1940s and 1950s) and mass mortality events (1995, 1999 and 2007) M. mactroides was the prominent primary consumer in the intertidal ecosystem and an important economic resource in Argentina. Since D.

Applying the alkenone method, we estimated sea-surface temperatures (SSTs) for the past 33 kyr in two marine sediment cores recovered from the continental slope off mid-latitude Chile. The SST record shows an increase of 6.7?C from the last ice age (LIA) to the Holocene climatic optimum, while the temperature contrast between LIA and modern temperatures is only about 3.4?C. The timing and magnitude of the last deglacial warming in the ocean correspond to those observed in South American continental records.