(Table 1) Abundance of shocked quartz in K/T boundary sediments from DSDP Site 91-596

Sediments from the Cretaceous/Tertiary (K/T) boundary at Deep Sea Drilling Project Site 596 record accumulation of pelagic clays at about lat 45°S,in the center of the ancestral South Pacific. The K/T boundary in this region is characterized by oxidized, thoroughly bioturbated sediments containing large amounts of Ir and relict high-pressure and high-temperature mineral phases. The net Ir fluence (320 ng/cm**2) is among the largest on Earth, and the number of shocked quartz grains >30 µm in size (~1800/cm**2) exceeds that in all localities outside of North America.

Age, pollen and spores of ODP Site 175-1082

The present-day condition of bipolar glaciation characterized by rapid and large climate fluctuations began at the end of the Pliocene with the intensification of the Northern Hemisphere continental glaciations. The global cooling steps of the late Pliocene have been documented in numerous studies of Ocean Drilling Program (ODP) sites from the Northern Hemisphere. However, the interactions between oceans and between land and ocean during these cooling steps are poorly known. In particular, data from the Southern Hemisphere are lacking. Therefore I investigated the pollen of ODP Site 1082 in the southeast Atlantic Ocean in order to obtain a high-resolution record of vegetation change in Namibia between 3.4 and 1.8 Ma. Four phases of vegetation development are inferred that are connected to global climate change. (1) Before 3 Ma, extensive, rather open grass-rich savannahs with mopane trees existed in Namibia, but the extension of desert and semidesert vegetation was still restricted. (2) Increase of winter rainfall dependent Renosterveld-like vegetation occurred between 3.1 and 2.2 Ma connected to strong advection of polar waters along the Namibian coast and a northward shift of the Polar Front Zone in the Southern Ocean. (3) Climatically induced fluctuations became stronger between 2.7 and 2.2 Ma and semiarid areas extended during glacial periods probably as the result of an increased pole-equator thermal gradient and consequently globally enhanced atmospheric circulation. (4) Aridification and climatic variability further increased after 2.2 Ma, when the Polar Front Zone migrated southward and the influence of Atlantic moisture brought by the westerlies to southern Africa declined. It is concluded that the positions of the frontal systems in the Southern Ocean which determine the locations of the high-pressure cells over the South Atlantic and the southern Indian Ocean have a strong influence on the climate of southern Africa in contrast to the climate of northwest and central Africa, which is dominated by the Saharan low-pressure cell.

Results of a sediment profile and water analyses from Lake Hancza in northeastern Poland

We investigated the sedimentary record of Lake Hancza (northeastern Poland) using a multi-proxy approach, focusing on early to mid-Holocene climatic and environmental changes. AMS 14C dating of terrestrial macrofossils and sedimentation rate estimates from occasional varve thickness measurements were used to establish a chronology. The onset of the Holocene at c. 11600 cal. a BP is marked by the decline of Lateglacial shrub vegetation and a shift from clastic-detrital deposition to an autochthonous sedimentation dominated by biochemical calcite precipitation. Between 10000 and 9000 cal. a BP, a further environmental and climatic improvement is indicated by the spread of deciduous forests, an increase in lake organic matter and a 1.7% rise in the oxygen isotope ratios of both endogenic calcite and ostracod valves. Rising d18O values were probably caused by a combination of hydrological and climatic factors. The persistence of relatively cold and dry climate conditions in northeastern Poland during the first one and a half millennia of the Holocene could be related to a regional eastern European atmospheric circulation pattern. Prevailing anticyclonic circulation linked to a high-pressure cell above the retreating Scandinavian Ice Sheet might have blocked the influence of warm and moist Westerlies and attenuated the early Holocene climatic amelioration in the Lake Hancza region until the final decay of the ice sheet.

(Table 1) Physical properties of ODP Site 129-801

Compressional wave velocities and densities were measured for 6 basalt samples from ODP Hole 801B and 16 samples from ODP Hole 801C, a site that represents the first drilling of Jurassic-age crustal rocks in the Pacific basin. Incremental measurements, taken to a total pressure of 200 MPa, show a systematic decrease in velocity with increasing porosity and a related increase with increasing wet-bulk density. A comparison of the plot of porosity vs. compressional wave velocity with the theoretical equation from Wyllie et al. (1958) suggests this equation is inappropriate for oceanic basalts because of mineral alteration in high porosity samples. Also of interest is the dramatic change in velocity across a hydrothermal boundary. Basalts below this hydrothermal layer have a mean velocity of 6.05 km/s at 60 MPa while those above show a mean velocity of 4.55 km/s at 60 MPa. The low velocity values of the basalts above the hydrothermal deposit may be attributed to the higher porosity and composition observed in these rocks; the higher porosity is possibly the result of increased exposure to circulating seawater.

(Table 1) Mineral composition of ODP Hole 125-778A

The high-pressure, low-temperature metamorphic rocks known as blueschists have long been considered to form in subduction zones, where the descent of a relatively cold slab leads to the occurrence of unusually low temperatures at mantle pressures. Until now, however, the link between blueschist-facies rocks and subduction zones has been indirect, relying on a spatial association of blueschists with old subduction complexes, and estimates of the geothermal gradients likely to exist in subduction zones. Here we strengthen this link, by reporting the discovery of blueschist-facies minerals (lawsonite, aragonite, sodic pyroxene and blue amphibole) in clasts from a serpentinite seamount in the forearc of the active Mariana subduction zone. The metamorphic conditions estimated from the mineral compositions are 150-250 °C and 5-6 kbar (16-20 km depth). The rocks must have been entrained in rising serpentine mud diapirs, and extruded from mud volcanoes onto the sea floor. Further study of these rocks may provide new insight into the tectonics of trench-forearc systems, and in particular, the processes by which blueschist-facies clasts come to be associated with forearc sediments in ancient subduction complexes.