Relative abundance of pennate diatoms Thalassionema spp. and Thalassiothrix spp. im Upper Miocene-Lower Pliocene bulk sediment at ODP Hole 145-886B, North Pacific (Table 1)

Rapidly deposited Thalassionema-Thalassiothrti pennate diatom oozes previously have been described in Upper Miocene-Lower Pliocene sediment beneath the frontal boundary of the eastern equatorial Pacific. Here we document a new occurrence of Thalassionema-Thalassiothrix ooze in Upper Miocene-Lower Pliocene sediment beneath the frontal boundary of the subarctic North Pacific. The ooze is a 6 m interval of siliceous sediment at Ocean Drilling Program (ODP) sites 885/886 that was rapidly deposited between approximately 5.0 and 5.9 Ma. Bulk sediment in this interval may contain greater than 85% pennate diatom tests. There are also abundant laminae and pockets that are composed entirely of Thalassionema and Thalassiothrix diatoms. The presence of a rapidly deposited ooze dominated by pennate diatoms indicates unusual past conditions in the overlying surface waters. Time coincident deposition of such oozes at two distinct frontal boundary locations of the Pacific suggests that the unusual surface water conditions were causally linked to large-scale oceanographic change. This same oceanographic change most likely involved (1) addition of nutrients to the ocean, or (2) redistribution of nutrients within the ocean. The occurrence and origin of pennate diatom oozes may be a key component to an integrative understanding of late Neogene paleoceanography and biogeochemical cycling.

Grain counts and relative abundances of volcaniclastic sands and sandstones of ODP Leg 180 sites

Modal analysis of middle Miocene to Pleistocene volcaniclastic sands and sandstones recovered from Sites 1108, 1109, 1118, 1112, 1115, 1116, and 1114 within the Woodlark Basin during Leg 180 of the Ocean Drilling Program indicates a complex source history for sand-sized detritus deposited within the basin. Volcaniclastic detritus (i.e., feldspar, ferromagnesian minerals, and volcanic rock fragments) varies substantially throughout the Woodlark Basin. Miocene sandstones of the inferred Trobriand forearc succession contain mafic and subordinate silicic volcanic grains, probably derived from the contemporary Trobriand arc. During the late Miocene, the Trobriand outerarc/forearc (including Paleogene ophiolitic rocks) was subaerially exposed and eroded, yielding sandstones of dominantly mafic composition. Rift-related extension during the late Miocene-late Pliocene led to a transition from terrestrial to neritic and finally bathyal deposition. The sandstones deposited during this period are composed dominantly of silicic volcanic detritus, probably derived from the Amphlett Islands and surrounding areas where volcanic rocks of Pliocene-Pleistocene age occur. During this time terrigenous and metamorphic detritus derived from the Papua New Guinea mainland reached the single turbiditic Woodlark rift basin (or several subbasins) as fine-grained sediments. At Sites 1108, 1109, 1118, 1116, and 1114, serpentinite and metamorphic grains (schist and gneiss) appear as detritus in sandstones younger than ~3 Ma. This is thought to reflect a major pulse of rifting that resulted in the deepening of the Woodlark rift basin and the prevention of terrigenous and metamorphic detritus from reaching the northern rift margin (Site 1115). The Paleogene Papuan ophiolite belt and the Owen Stanley metamorphics were unroofed as the southern margin of the rift was exhumed (e.g., Moresby Seamount) and, in places, subaerially exposed (e.g., D'Entrecasteaux Islands and onshore Cape Vogel Basin), resulting in new and more proximal sources of metamorphic, igneous, and ophiolitic detritus. Continued emergence of the Moresby Seamount during the late Pliocene-early Pleistocene bounded by a major inclined fault scarp yielded talus deposits of similar composition to the above sandstones. Upper Pliocene-Pleistocene sandstones were deposited at bathyal depths by turbidity currents and as subordinate air-fall ash. Silicic glassy (high-K calc-alkaline) volcanic fragments, probably derived from volcanic centers located in Dawson and Moresby Straits, dominated these sandstones.

Relative abundances of planktonic foraminifera from surface sediments of the Drake Passage, Southern Ocean (Table 1)

Based on a qualitative and quantitative evaluation of Recent sediments samples (top 3 cm of cores as well as Petersen grab samples) from the Drake Passage, between South America and Antarctica, the distribution of planktonic foraminifera and their relation to oceanographic conditions was investigated. The Antarctic Convergence - the northern limit of the cold Antarctic Surface Water - is shown to be of major importance in controlling the distributional pattern of planktonic species as well as their total numbers. South of the convergence, Globigerina pachyderma is usually the only species found in the sediment. It occurs with abundances not greater than 6000 per gram dry sediment, and at most stations less than 100 specimens per gram of dry sediment were recovered. At a number of deep-sea stations below 3700 m depth approx. no planktonic foraminifera were found at all. It is most probable, that at least some of these stations are located below the limit of CaCO3 dissolution. North of the Antarctic Convergence planktonic foraminiferal numbers are much higher and range from 1800 to 120000 per gram of dry sediment. Eight species are the major constituents of the population: Globigerina pachyderma, Globigerina bulloides, Globogerina quinqueloba, Globigerina inflata, Globorotalia truncatolinoides, Globorotalia scitula, Globigerinita glutinata and Globigerinita uvula. The widespread occurrence of Globorotalia truncatulinoides, which in the northern hemisphere is usually a subtropical form, is especially noteworthy. Another Globigerina, morphologically similar to G. pachyderma, has been recognized frequently north of the Antarctic Convergence. Globigerina megastoma which has its type area in the Drake Passage, has been found only rarely. Orbulina universa occurs in samples from the areas of higher water temperature around the South American Continent. Globigerina pachyderma is predominantly sinistrally coiled throughout the area investigated, but a slight increase in the percentage of dextrally coiled specimens may be noticed with increasing water temperature, i.e. from south to north.

The relative strength of nurture and nature.

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Index of the relative importance of fuel efficiency (IFE) in the motor vehicle market. Final report.

National Highway Traffic Safety Administration, Office of Research and Development, Washington, D.C.