Revised Cenozoic hiatus database

The differential effects of climate change, sea level, and water mass circulation on deposition/erosion of marine sediments can be constrained from the distribution of unconformities in the world's oceans. I identified temporal and depth patterns of hiatuses ("hiatus events") from a large and chronologically well constrained stratigraphic database of deep-sea sediments. The Paleogene is characterized by few, several million year long hiatuses. The most significant Cenozoic hiatus event spans most of the Paleocene. The Neogene is characterized by short, frequent hiatus events nearly synchronous in shallow and deep water sediments. Epoch boundaries are characterized by peaks in deep water hiatuses possibly caused by an increased circulation of corrosive bottom water and sediment dissolution. The Plio-Pleistocene is characterized by a gradual decrease in the frequency of hiatuses. Future studies will focus on the regional significance of the hiatus events and their possible causes.

Petrology, geochemistry and K-Ar Age determination of De Gerlache Seamount basalts

The De Gerlache Seamounts are two topographic highs in the Bellingshausen Sea, southeastern Pacific. Petrological and geochemical studies together with K-Ar age determinations were carried out on four dredged basalt samples collected during a RV Polarstern expedition (ANT-XII/4) in 1995. Minor and trace element composition suggest alkaline basalt compositions. Compared to alkaline basalts of adjacent West Antarctica (the Jones Mountains) and of Peter I Island, the samples have lower mg-numbers, lower Ni and Cr contents and lower high field-strength elements (HFSE)/Nb and large-ion lithophile elements (LILE)/HFSE ratios. Three of the four samples have low K, Rb, and Cs concentrations relative to alkaline basalts. The K-depletion and other elemental concentrations may be explained by 1.1% melting of amphibole bearing mantle material. Additionally, low Rb and Ba values suggest low concentrations of these elements in the mantle source. K-Ar age determinations yield Miocene ages (20-23 Ma) that are similar in age to other alkaline basalts of West Antarctica (Thurston Island, the Jones Mountains, Antarctic Peninsula) and the suggested timing of onset of Peter I Island volcanism (~10-20 Ma). The occurrence of the DGS and Peter I Island volcanism along an older but reactivated tectonic lineation suggests that the extrusions exploited a zone of pre-existing lithospheric weakness. The alkaline nature and age of the DGS basalts support the assumption of plume activity in the Bellingshausen Sea.

Results of analyses of unmelted meteoritic debris collected from Eltanin ejecta in three sediment core from POLARSTERN cruise ANT-XII/4

A total of 1.7 g of unmelted meteorite particles have been recovered from FS Polarstern piston cores collected on expedition ANT XII/4 that contain ejecta from the Eltanin impact event. Most of the mass (1.2 g) is a large, single specimen that is a polymict breccia, similar in mineralogy and chemistry to howardites or the silicate fraction of mesosiderites. Most of the remaining mass is in several large individual pieces (20-75mg each) that are polymict breccias, fragments dominated by pyroxene, and an igneous rock fragment. The latter has highly fractionated REE, similar to those reported in mafic clasts from mesosiderites. Other types of specimens identified include fragments dominated by maskelynite or olivine. These pieces of the projectile probably survived impact by being blown off the back surface of the Eltanin asteroid during its impact into the Bellingshausen Sea.

Beryllium-10, mineralogy and grain size distribution of DSDP Hole 68-502B (Table 1)

We present a high-resolution 10Be profile from deep sea sediments (sampled from Hole 502B in the Caribbean sea) that strongly resembles the 10Be record in ice core profiles, particularly the Vostok core from Antarctica. This high-resolution profile revealed occurrences of enhanced 10Be concentrations at about 23-24, 37-39 and 60-65 ka. The excellent match between these peaks appearing in a georeservoir profile other than in polar ice, strengthens the implications that can be inferred from 10Be and provide global markers for chronological correlation of climatic events. The position at low latitude of the studied sediment section is, unlike the case with the high latitude polar regions, excellent for exposing causes of modulation in 10Be production. We interpret the source of the pattern and enhancements, particularly the 37-39 ka peak, of 10Be to be global and do not strictly relate to climatic conditions and/or production rates specific to the polar regions.

Sedimentology of various cores from the West Antarctic continental margin

Three megascopic and disseminated tephra layers (which we refer to as layers A, B, and C) occur in late Quaternary glaciomarine sediments deposited on the West Antarctic continental margin. The stratigraphical positions of the distal tephra layers in 28 of the 32 studied sediment cores suggest their deposition during latest Marine Isotopic Stage (MIS) 6 and MIS 5. One prominent tephra layer (layer B), which was deposited subsequent to the penultimate deglaciation (Termination II), is present in almost all of the cores. Geochemical analyses carried out on the glass shards of the layers reveal a uniform trachytic composition and indicate Marie Byrd Land (MBL), West Antarctica, as the common volcanic source. The geochemical composition of the marine tephra is compared to that of ash layers of similar age described from Mount Moulton and Mount Takahe in MBL and from ice cores drilled at Dome Fuji, Vostok and EPICA Dome C in East Antarctica. The three tephra layers in the marine sediments are chemically indistinguishable. Also five englacial ash layers from Mt. Moulton, which originated from highly explosive Plinian eruptions of the Mt. Berlin volcano in MBL between 142 ka and 92 ka ago, are chemically very similar, as are two tephra layers erupted from Mt. Takahe at ca. 102 ka and ca. 93 ka. Statistical analysis of the chemical composition of the glass shards indicates that the youngest tephra (layer A) in the marine cores matches the ash layer erupted from Mt. Berlin at 92 ka, which was previously correlated with tephra layers in the EPICA Dome C and the Dome Fuji ice cores. A tephra erupted from Mt. Berlin at 136 ka seems to correspond to a tephra layer deposited at 1733 m in the EPICA Dome C ice core. Additionally, the oldest tephra (layer C) in the marine sediments resembles an ash layer deposited at Vostok around 142 ka, but statistical evidence for the validity of this correlation is inconclusive. Although our results underscore the potential of tephrostratigraphy for correlating terrestrial and marine palaeoclimate archives, our study also reveals limitations of this technique, which may result in the miscorrelation of tephra. Such pitfalls comprise failure to recognise the occurrence of various tephra layers in marine sediment cores, 'swamping' of records with chemically indistinguishable tephra from a single volcanic source, and exclusive use of 'geochemical fingerprinting' for correlating ash layers.

Calcium carbonate global LGM Burial rate data

Global databases of calcium carbonate concentrations and mass accumulation rates in Holocene and last glacial maximum sediments were used to estimate the deep-sea sedimentary calcium carbonate burial rate during these two time intervals. Sparse calcite mass accumulation rate data were extrapolated across regions of varying calcium carbonate concentration using a gridded map of calcium carbonate concentrations and the assumption that accumulation of noncarbonate material is uncorrelated with calcite concentration within some geographical region. Mean noncarbonate accumulation rates were estimated within each of nine regions, determined by the distribution and nature of the accumulation rate data. For core-top sediments the regions of reasonable data coverage encompass 67% of the high-calcite (>75%) sediments globally, and within these regions we estimate an accumulation rate of 55.9 ± 3.6 x 10**11 mol/yr. The same regions cover 48% of glacial high-CaCO3 sediments (the smaller fraction is due to a shift of calcite deposition to the poorly sampled South Pacific) and total 44.1 ± 6.0 x 10**11 mol/yr. Projecting both estimates to 100 % coverage yields accumulation estimates of 8.3 x 10**12 mol/yr today and 9.2 x 10**12 mol/yr during glacial time. This is little better than a guess given the incomplete data coverage, but it suggests that glacial deep sea calcite burial rate was probably not considerably faster than today in spite of a presumed decrease in shallow water burial during glacial time.

Mapping of the Eltanin impact area in the South-East Pacific

Two Polarstern expeditions were conducted in 1995 (ANT-XII/4) and 2001 (ANT-XVIII/5a) to the Bellingshausen Sea and Amundsen Sea and the suspected Eltanin meteorite impact in the SE-Pacific. A survey of the sediment distribution and its acoustic structure along the cruise track was performed. The seafloor topography was sampled using the multibeam sonar system Hydrosweep DS2 which operates on a frequency of 15.5 kHz. The resulting AWI Bathymetric Chart of the Eltanin Meteorite Impact Area is based on a Digital Terrain Model of this area. The mapping was performed using ArcGIS. The Eltanin impact area which covers the 4.100 m high Freden Seamount is visualized by one overview sheet of the scale 1:200,000 and four 1:100,000 subsheets.

Distribution of planktonic foraminifera in DSDP Hole 31-296 (Table III)

Late Neogene planktonic foraminiferal biostratigraphy of DSDP Site 296, Leg 31, reveals this site as an ideal reference section for correlation of Blow's low-latitude zonation with the mid-latitude zonation for temperate faunal assemblages developed in this paper and earlier for DSDP Site 310, Leg 31 (Keller). Abundance of temperate species of Globorotalia (G. inflata, G. puncticulata, G. crassaformis, G. conomiozea) permit correlation with the zonal subdivision developed at Site 310 based on these species. Evolutionary changes within the Globorotalia inflata group also appear to be consistent biostratigraphie markers in mid latitudes; a primitive variety of this species first appears at about 3.3-3.1 Ma, G. inflata praeinflata appears at about 2.6 Ma, and the modern form appears at about 2.2-2.1 Ma. Quantitative analyses of planktonic foraminifera at DSDP Site 296 reveal an inversely reciprocal frequency oscillation between species of Globorotalia and the Globigerina-Globigerinita group. Cool climatic periods are characterized by high frequencies in the Globigerina-Globigerinita group and low frequencies in the Globorotalia group, whereas warm intervals are marked by high frequencies in the Globorotalia group and low frequencies in the Globigerina-Globigerinita group. Five cool paleoclimatic events can be recognized between early Pliocene and late Pleistocene: 4.4 Ma, 3.2-3.1 Ma, 2.4-2.2 Ma, 1.2 Ma, and 0.7 Ma. These paleoclimatic/paleoceanographic events have also been recognized in planktonic foraminifera of the Central and Northeast Pacific DSDP Sites 310 and 173 and also correlate to cold events recognized in oxygen isotope measurements of DSDP Site 310 and in equatorial Pacific cores.

At surface behaviour of juvenile and female southern elephant seals from King George Island from expeditions JUB1996 and JUB1997

Between December 1996 and February 1997, weaned pups and postmoult female southern elephant seals (Mirounga leonina) were fitted with satellite transmitters at King George Island (South Shetlands). Of the nine adult females tracked for more than two months, three stayed in a localized area between the South Shetlands and the South Orkneys. The other six females travelled southwest along the coast of the Antarctic Peninsula up to the Bellingshausen Sea. Two of them then moved far northeast and hauled out on South Georgia in October. One female was last located north of the South Shetlands in March 1998. In total, eight females were again sighted on King George Island and six of the transmitters removed. The tracks of the weaners contrasted with those of the adults. In January, five juveniles left King George Island for the Pacific sector ranging about four weeks in the open sea west of the De Gerlache Seamounts. Three of them returned to the tip of the Antarctic Peninsula in June, of which one was last located on the Patagonian Shelf in November 1997. A computer animation was developed to visualize the animal movements in relation to the extent and concentration of sea ice. The juveniles avoided sea ice while the adults did not. The latter displayed behavioural differences in using the pack ice habitat during winter. Some females adjusted their movement patterns to the pulsating sea ice fringe in far-distant foraging areas while others ranged in closed pack ice of up to 100 %. The feeding grounds of adult female elephant seals are more closely associated with the pack ice zone than previously assumed.