Radiocarbon dates and dinoflagellate cysts of sediment core DP30PC

To obtain insight into character and potential forcing of short-term climatic and oceanographic variability in the southern Italian region during the "Roman Classical Period" (60 BC-AD 200), climatic and environmental reconstructions based on a dinoflagelate cyst record from a well dated site in the Gulf of Taranto located at the distal end of the Po-river discharge plume have been established with high temporal resolution. Short-term fluctuations in accumulation rates of the Adriatic Surface Water species Lingulodinium machaerophorum, the freshwater algae Concentricystes and species resistant to aerobic degradation indicate that fluctuations in the trophic state of the upper waters are related to river discharge of northern and eastern Italian rivers which in turn are strongly related to precipitation in Italy. The dinoflagellate cyst association indicates that local sea surface temperatures which in this region are strongly linked to local air temperatures were slightly higher than today. We reconstruct that sea surface temperatures have been relatively high and stable between 60 BC-AD 90 and show a decreasing trend after AD 90. Fluctuations in temperature and river discharge rates have a strong cyclic character with main cyclicities of 7-8 and 11 years. We argue that these cycles are related to variations of the North Atlantic Oscillation climate mode. A strong correlation is observed with global variation in Delta14C anomalies suggesting that solar variability might be one of the major forcings of the regional climate. Apart from cyclic climate variability we observed a good correlation between non-cyclic temperature drops and global volcanic activity indicating that the latter forms an additional major forcing factor of the southern Italian climate during the Roman Classical Period.

Investigation of Quaternary foraminifera in sediment core CRP-1 from the Ross Sea, Antarctica

Foraminifera are examined in twenty-six samples from a 44 metre succession of Quaternary glacial sediments recovered from the CRP-1 drillhole on Roberts Ridge, southwestern Ross Sea, Antarctica. In situ marine assemblages were documented in at least three of the six lithostratigraphic units, and it is likely that the remaining three interbedded diamicton units are also marine in origin. Peak foraminiferal diversities are documented in Unit 3.1 (73 species) and Unit 2.2 (32 species). Calcareous benthics dominate the assemblages, but may be accompanied by abundant occurrences of the planktonic Neogloboquadrina pachyderma. Low diversity agglutinated faunas appear in the uppermost strata of Units 4.1 and 2.2. A close relationship between lithofacics and foraminiferal biofacies points to marine environments that alternated between proximity to and distance from active glaciers and iceshelf fronts, with associated variations in salinity, sea-surface ice cover and the levels of rainout from debris-laden ice.

Chronostratigraphy of sediment core CRP-3 from the Ross Sea, Antarctica

An 823 m thick glaciomarine Cenozoic section sitting unconformably on the Lower Devonian Beacon Supergroup was recovered in CRP-3. This paper reviews the chronostratigraphical constraints for the Cenozoic section. Between 3 and 480.27 mbsf 23 unconformity bounded cycles of sediment were recorded. Each unconformity is thought to represent a hiatus of uncertain duration. Four magnetozones have been recognised from the Cenozoic section. The record is complex with several 'tiny wiggles'' recorded throughout. Biostratigraphical or Sr ages, which could be used to link these magnetozones to the magnetic polarity time scale are restricted to the upper 190 m of sediment. Two diatom datums (Cavitatus jouseanus at 48.9 mbsf and Rhizosolenica antarctica at 68.60 mbsf), together with five Sr-isotope dates derived from molluscan fragments taken from between 10.88 and 190.29 mbsf indicate an early Oligocene (c. 31 Ma) age for this interval. The appearance of a new species of the bivalve ?Adamussium at about 325 mbsf, suggests that the Oligocene age can be extended down to this level. This confirms that the dominantly reversed magnetozone (RI), recorded down to about 340 mbsf, is Chron C12r. The ages imply high sedimentation rates and only minimal time gaps at the sequence boundaries. Below 340 mbsf there are no independent datums to guide the correlation of the magnetozones to the magnetic polarity time scale. However, the absence of in situ dinocysts attributable to Transantarctic Flora, if not a result of environmental control, limits the age of the base of the hole to between c. 33.5 and 35 Ma.