Carbonate content of sediment core CRP-1 (Table 1)

Determinations of total carbonate content yield additional information, in the context of integrated investigations, thus enabling or enhancing the interpretation and characterisation of the depositional environment, the processes of sedimentation and the diagenesis of sediments. In the case of drillcores, they help us to discern vertical gradations of facies sequences that have repeating patterns or show changes through time. This report presents initial results of carbonate investigations on a total of 32 bulk samples from the Quaternary and Miocene strata of the CRP-1 borehole, which reached a final depth of 147.69 metres below sea floor (mbsf). Fifteen out of a total of 18 lithostratigraphic units in the core were sampled (Tab. 1). Fourteen samples (24.85-43.85 mbsf) belong to the Quaternary, whereas 18 samples (44.53-146.51 mbsf) originate from the Miocene strata. The sampling intervals varied from 1-5 m for the Quaternary, and 1-15 m for the Miocene. All the samples originated from sections of core representing not more than 1 cm thickness.

Cooperative mining series. Bulletin [1]-33.

No. 33 is the final no. of this series.

Long chain alkyl diol distribution in Arabian Sea surface sediments

Oxygen exposure has a large impact on lipid biomarker preservation in surface sediments and may affect the application of organic proxies used for reconstructing past environmental conditions. To determine its effect on long chain alkyl diol and keto-ol based proxies, the distributions of these lipids was studied in nine surface sediments from the Murray Ridge in the Arabian Sea obtained from varying water depths (900 to 3000 m) but in close lateral proximity and, therefore, likely receiving a similar particle flux. Due to substantial differences in bottom water oxygen concentration (<3 to 77 µmol/L) and sedimentation rate, substantial differences exist in the time the biomarker lipids are exposed to oxygen in the sediment. Long chain alkyl diol and keto-ol concentrations in the surface sediments (0-0.5 cm) decreased progressively with increasing oxygen exposure time, suggesting increased oxic degradation. The 1,15-keto-ol/diol ratio (DOXI) increased slightly with oxygen exposure time as diols had apparently slightly higher degradation rates than keto-ols. The ratio of 1,14- vs. 1,13- or 1,15-diols, used as upwelling proxies, did not show substantial changes. However, the C30 1,15-diol exhibited a slightly higher degradation rate than C28 and C30 1,13-diols, and thus the Long chain Diol Index (LDI), used as sea surface temperature proxy, showed a negative correlation with the maximum residence time in the oxic zone of the sediment, resulting in ca. 2-3.5 °C change, when translated to temperature. The UK'37 index did not show significant changes with increasing oxygen exposure. This suggests that oxic degradation may affect temperature reconstructions using the LDI in oxic settings and where oxygen concentrations have varied substantially over time.