Composition of sedimentary rocks from the Burun-Tas Formation, Bol'shoi Lyakhov Island (New Siberian Islands)

Graywackes and shales of the Bol'shoi Lyakhov Island originally attributed to Mesozoic were subsequently considered based on microfossils as Late Proterozoic in age. At present, these sediments in the greater part of the island are dated back to Permian based on palynological assemblages. In the examined area of the island, this siliciclastic complex is intensely deformed and tectonically juxtaposed with blocks of oceanic and island-arc rocks exhumed along the South Anyui suture. The complex is largely composed of turbidites with members displaying hummocky cross-stratification. Studied mineral and geochemical charac¬teristics of the rocks defined three provenances of clastic material: volcanic island arc, sedimentary cover and/or basement of an ancient platform, and exotic blocks of oceanic and island-arc rocks such as serpentinites and amphibolites. All rock associations represent elements of an orogenic structure that originated by collision of the New Siberian continental block with the Anyui-Svyatoi Nos island arc. Flyschoid sediments accumu¬lated in a foredeep in front of the latter structure in the course of collision. Late Jurassic volcanics belonging to the Anyui-Svyatoi Nos island arc determine the lower age limit of syncollision siliciclastic rocks. Presence of Late Jurassic zircons in sandstones of the flyschoid sequence in the Bol'shoi Lyakhov Island is confirmed by fission-track dating. The upper age limit is determined by Aptian-Albian postcollision granites and diorites intruding the siliciclastic complex. Consequently, the flyschoid sequence is within stratigraphic range from the terminal Late Jurassic to Neocomian. It appears that Permian age of sediments suggested earlier is based on redeposited organic remains. The same Late Jurassic-Neocomian age and lithology are characteristic of fossiliferous siliciclastic sequences of the Stolbovoi and Malyi Lyakhov islands, the New Siberian Archipelago, and of graywackes in the South Anyui area in the Chukchi Peninsula. All these sediments accumulated in a spacious foredeep that formed in the course the late Cimmerian orogeny along the southern margin of the Arctic conti¬nental block.

Distribution of benthos in late Quaternary turbidite layers of sediment cores from the North-West African continental margin

The CaCO3-contents and the fractions > 40 µm have been analysed from 5 kastenloten, one piston core and two kastengreifer taken between Senegal and Cape Verde Islands. Numerous benthonic and planktonic organisms and different terrigenous components have been distinguished. The four cores off Senegal reach middle Wuerm sediments; cores GIK12329-6 and TAG72-1 reach the V-zone and core GIK12331-4 the X-zone (Eem); the two kastengreifer contain sediments of Holocene age. Correlation of the cores has been made. Holocene sedimentation rates decrease from the shallow cores (6-11 cm/1000 years) to the deep-sea (1-2 cm/1000 years). The following climatic variations could be deduced from the sediments off the Senegal: during Holocene climate was in general as today, the Senegal river transporting fine grained material to the sea. The upper Wuerm was arid with no river influence but with red dune sand transported to the continental slope. During middle Wuerm the climate was humid again. The deep-sea cores have been influenced by eolian material from arid regions during glacial and interglacial periods, indicated by relatively high "Wuestenquarz-numbers". However, during Wuerm "Wuestenquarz-numbers" are higher than during Holocene and Eem, indicating that more intensely red coloured sediment was exposed to wind activity on the continent during this period. Varying amounts of terrigenous material and CaCO3-contents indicate varying wind strengths (lower in Holocene and Eem than during Wuerm). The boundary between humid and arid Wuerm climate was at approximately 20 °N. Influence of upwelling is difficult to establish in the sediments off Senegal, because river influence, while increasing fertility also dilutes the diatoms which are typical for upwelling. High amounts of organic carbon, low plankton/benthos ratios of foraminifers and low plankton foraminifer/radiolarian ratios in Holocene sections might be interpreted as influenced by upwelling. Turbidites occur in cores 72 and 31 and at the Holocene/Pleistocene boundary of core GIK12329-6. Their composition indicates provenance from the continental shelf of the Cape Verde Islands for core 31 and the continental shelf and slope off Senegal for core TAG72-1. Volcanic material, rare in the normal pelagic sediment of core GIK12331-4 is more frequent in the turbidites.

Geochemistry of Pliocene-Pleistocene volcanic sands of ODP Site 136-842

Several distinct, thin (2-7 cm), volcanic sand layers ("ashes") were recovered in the upper portions of Holes 842A and 842B. These holes were drilled 320 km west of the island of Hawaii on the outer side of the arch that surrounds the southern end of the Hawaiian chain. These layers are Pliocene to Pleistocene in age, graded, and contain fresh glass and mineral fragments (mainly olivine, plagioclase, and clinopyroxene) and tests of Pleistocene to Eocene radiolarians. The glass fragments are weakly vesicular and blocky to platy in shape. The glass and olivine fragments from individual layers have large ranges in composition (i.e, larger than expected for a single eruption). These features are inconsistent with an explosive eruption origin for the sands. The only other viable mechanism for transporting these sands hundreds of kilometers from their probable source, the Hawaiian Islands, is turbidity currents. These currents were probably related to several of the giant debris slides that were identified from Gloria sidescan images around the islands. These currents would have run over the ~500-m-high Hawaiian Arch on their way to Site 842. This indicates that the turbidity currents were at least 325 m thick. Paleomagnetic and biostratigraphic data allow the ages of the sands to be constrained and, thus, related to particular Hawaiian debris flows. These correlations were checked by comparing the compositions of the glasses from the sands with those of glasses and rocks from islands with debris flows directed toward Site 842. Good correlations were found for the 110-ka slide from Mauna Loa and the ~1.4-Ma slide from Lanai. The correlation with Kauai is poor, probably because the data base for that volcano is small. The low to moderate sulfur content of the sand glasses indicates that they were derived from moderately to strongly degassed lavas (shallow marine or subaerially erupted), which correlates well with the location of the landslide scars on the flanks of the Hawaiian volcanoes. The glass sands may have been formed by brecciation during the landslide events or spallation and granulation as lava erupted into shallow water.

Tab.1: Tabulation of pinguin population within the Antarctic Peninsula region

Six species of penguins breed on the Antarctic continent, the Antarctic Peninsula, the South Shetland and South Orkney Islands. Their breeding populations within the Antarctic Peninsula, and the South Orkney and South Shetland Is., and estimates of global populations are given. Typical breeding seasons are also presented, but it must be noted that these will vary inter-annually and intra-annually under the influence of factors such as sea-ice extent and ENSO (interannual) and the location of each breeding colony (southerly localities will be later than northerly localities, as their breeding season is "compressed" within the shorter summer). Their foraging strategies (categorized as near-shore or offshore) and typical durations of foraging trips are also tabulated. As with breeding season events, foraging behaviour will vary intra-seasonally and inter-seasonally (in terms of dive duration, dive depth, foraging location, etc). The distribution of known penguin breeding colonies is circum-continental, with Emperor and Adelie penguins predominant on approximately 75 % of the coast, with two major concentrations in the Ross Sea and in Prydz Bay. The third concentration is in the Antarctic Peninsula region, where some of the largest penguin colonies are present. All six species breed within the area (predominantly Chinstrap Penguins), and the Peninsula region has a greater diversity than the remainder ofthe Antarctic with respect to penguins. The distribution at sea of nonbreeding penguins is less cIear. Non-breeding individuals of all six species move throughout the Southern Ocean, and in many cases, to areas well north of the winter pack-ice zone. However, it is not possible to estimate densities of penguins at sea as there are no estimates of non-breeding penguin populations the extent of their travels.

Isotope ratios of sediments from DSDP Hole 47-397 (Table 1)

We report the Sr, Nd and Pb isotopic compositions (1) of 66 lava flows and dikes spanning the circa 15 Myr subaerial volcanic history of Gran Canaria and (2) of five Miocene through Cretaceous sediment samples from DSDP site 397, located 100 km south of Gran Canaria. The isotope ratios of the Gran Canaria samples vary for 87Sr/86Sr: 0.70302-0.70346, for 143Nd/144Nd: 0.51275-0.51298, and for 206Pb/204Pb: 18.76-20.01. The Miocene and the Pliocene-Recent volcanics form distinct trends on isotope correlation diagrams. The most SiO2-undersaturated volcanics from each group have the least radiogenic Sr and most radiogenic Pb, whereas evolved volcanics from each group have the most radiogenic Sr and least radiogenic Pb. In the Pliocene-Recent group, the most undersaturated basalts also have the most radiogenic Nd, and the evolved volcanics have the least radiogenic Nd. The most SiO2-saturated basalts have intermediate compositions within each age group. Although the two age groups have overlapping Sr and Nd isotope ratios, the Pliocene-Recent volcanics have less radiogenic Pb than the Miocene volcanics. At least four components are required to explain the isotope systematics of Gran Canaria by mixing. There is no evidence for crustal contamination in any of the volcanics. The most undersaturated Miocene volcanics fall within the field for the two youngest and westernmost Canary Islands in all isotope correlation diagrams and thus appear to have the most plume-like (high 238U/204Pb) HIMU-like composition. During the Pliocene-Recent epochs, the plume was located to the west of Gran Canaria. The isotopic composition of the most undersaturated Pliocene-Recent volcanics may reflect entrainment of asthenospheric material (with a depleted mantle (DM)-like composition), as plume material was transported through the upper asthenosphere to the base of the lithosphere beneath Gran Canaria. The shift in isotopic composition with increasing SiO2-saturation in the basalts and degree of differentiation for all volcanics is interpreted to reflect assimilation of enriched mantle (EM1 and EM2) in the lithosphere beneath Gran Canaria. This enriched mantle may have been derived from the continental lithospheric mantle beneath the West African Craton by thermal erosion or delamination during rifting of Pangaea. This study suggests that the enriched mantle components (EM1 and EM2) may be stored in the shallow mantle, whereas the HIMU component may have a deeper origin.

Swath sonar bathymetry during POLARSTERN cruise ANT-XVI/4 (PS53) with links to multibeam raw data files

Multibeam data were collected without operator supervision on R/V Polarstern cruise ANT-XVI/4 along track lines of 6385 NM total length. Data were achieved during transits and stationary work on the route from Cape Town to Bremerhaven via the Cape Verde Islands and the Canary Islands. The multibeam sonar system Hydrosweep DS-2 was operated using 59 beams and 90° aperture angle. The quality of data might be reduced during bad weather periods or adverse sea ice conditions. The dataset contains raw data that are not processed and thus may contain errors and blunders in depth and position.

Mineralogy of ODP Site 105-645

Cores from the upper 70 meters below seafloor (mbsf) (upper Pleistocene) at Ocean Drilling Program (ODP) Site 645 in Baffin Bay show dramatic meter-scale changes in color and mineralogy. Below this interval, mineralogical changes are more gradual to the top of the Miocene at about 550 mbsf. The Pliocene-Pleistocene section can be divided into five facies: Facies 1 - massive, poorly sorted, gravel-bearing muds; Facies 2 - gray silty clays and silty muds; Facies 3 - laminated detricarbonate silty muds; Facies 4 - silty sand and sandy silt; and Facies 5 - poorly sorted muddy sands and silty muds. Facies 4 and 5 are restricted to the Pliocene section below depths of about 275 mbsf. The mineralogical/color cycles in the upper 70 mbsf are the result of alternations between Facies 2 and three lithotypes of Facies 1: lithotype A - tan-colored, carbonate-rich, gravel-bearing mud; lithotype B - weak, red-colored, gravel-bearing mud rich in sedimentary rock fragments; and lithotype C - gray, gravel-bearing mud. A fourth lithotype, D, is restricted to depths of 168-275 mbsf and is dark gray, carbonate-poor, gravel-bearing mud. We believe that all lithotypes of Facies 1 and the sand and gravel fractions of Facies 2 and 3 were deposited by ice rafting. Depositional processes for Facies 4 and 5 probably include ice rafting and bottom- and turbidity-current transport. Data from petrographic analyses of light and heavy sand-sized grains and X-ray analyses of silt- and clay-size fractions suggest that tan-colored sediments (lithotype A of Facies 1; Facies 3) were derived mainly from Paleozoic carbonates of Ellesmere, Devon, and northern Baffin islands. Weak red sediments (lithotype B) contain significant red sedimentary clasts, reworked quartzarenite grains and clasts, and rounded colorless garnets, all derived from Proterozoic sequences of the Borden and Thule basins, and from minor Mesozoic red beds. Other sediments in the upper 335 mbsf at Site 645 contain detritus from a heterogeneous mixture of sources, including Precambrian shield terranes around Baffin Bay. Sediments from 335 to 550 mbsf (Facies 5) are rich in friable sedimentary clasts and detrital micas and contain glauconite and, in a few samples, reworked diatoms. These components suggest derivation from poorly consolidated Mesozoic-Tertiary sediments in coastal outcrops and beneath the modern shelves of northeastern Baffin Island and western Greenland. For the upper Pleistocene section (about 0-100 mbsf), marked mineralogical cyclicity is attributed to fluctuating glacial margins, calving rates, and iceberg melting rates, particularly around the northern end of Baffin Bay. Tan-colored, carbonate-rich units were derived at times of maximum advance of glaciers on Ellesmere and Devon islands, during relatively warm intervals induced by incursion of warm Atlantic surface water into the bay. At the beginning of these warmer episodes, most icebergs were contributed by glaciers near sea level around the Arctic channels, which resulted in deposition of weak red, ice-rafted units rich in Proterozoic sedimentary clasts.