Distribution of siphonophores in the upwelling area off NW Africa

Using a Bongo-Net equipped with a multiple coded closing device, the vertical distribution of siphonophores has been observed in 100 m depth intervals at 13 stations off Cap Mirik (19°N) (from 0-500 m depth). This distributional pattern of the 15 siphonophores species found is discussed in relationship to the hydrography of this upwelling region. The following main features have been observed in comparision with the warmer oceanic water offshore: (1) a lower diversity, (2) a shallower distribution of some of the deep living species die to the lower temperature in the upper 300 m an a lower transparency, (3) no contribution to acoustic scattering by physonect siphonophores.

Occurrence of late Aptian/earliest Albian radiolaria from ODP Hole 113-693A (Table 2)

Unusually well preserved Cretaceous radiolarians are observed in the subsurface sections from two drilled sites in the Weddell Sea collected during Leg 113 of the Ocean Drilling Program. Radiolarians from the lithified calcareous chalk of Hole 689B represent the first Campanian-Maestrichtian assemblage which is characterized by abundant Cromyodruppa Iconcentrica, Dictyomitra multicostata, and Protostichocapsa stocki. Abundant Pseudodictyomitra pentacolaensis and Diacanthocapsa sp. 1, on the other hand, are the main constituents of the assemblage from the latest Aptian/earliest Albian diatomite of Hole 693B. These represent the oldest and the highest-latitude reported radiolarian occurrences from the Atlantic sector of the Antarctic Ocean. The assemblages are marked by their low diversity and an absence of low- to mid-latitude zonal indices.

Deep-sea sediment core PS2644 record from the southern Greenland Sea

The PS2644 deep-sea core sequence, retrieved from the northwestern margin of Iceland and covering the last 86 ka, exhibits high sedimentation rates during the last glacial cycle that allow the clear distinction of Greenland stadial (GS)/ interstadial (GI) cycles in the various proxy records. Abundance records of rhyolitic, basaltic and tachylytic tephra grains reveal several maxima. Tephra grains of all types were geochemically analyzed in 44 levels. A total of 92 tephras with a distinctive character have been defined within the glacial sequence of gravity core PS2644-5, whereas the Holocene record is dominated by reworked Vedde Ash grains and not suitable for tephra stratigraphic work. Of the 92 tephras only 19 geochemical populations have been linked with confidence to previously defined tephras such as from the Vedde Ash, Faeroe Marine Ash Zones (FMAZ) II and III and North Atlantic Ash Zone (NAAZ) II. For the glacial period informal names were given to 78 new tephras, most of which are basaltic tephras. Several of these layers have a unique geochemical character and might become new chronostratigraphic markers in the North Atlantic region. Linking the tephra populations to the volcanic system producing them, respectively, revealed that Icelandic eruptions dominate with 83 tephra geochemical populations and Jan Mayen with 9. Around 48% of the informal tephra layers linked to the Icelandic volcanic province are produced from either the Grimsvötn or the Veidivötn-Bardarbunga volcanic systems. The intervals spanning from Greenland Stadial (GS) 3 to Greenland Interstadial (GI) 4 (24.5-29 ka BP), from GI 8 to GS 10 (36.9-40.5 ka BP) and from GI 14 to GI 15.2 (50-56 ka BP) are the periods with the highest number of eruptions, all of which are associated with known tephra zones.

Mid-Cretaceous planktonic foraminifera off central Morocco

Sites 545 and 547 collectively penetrated 629 m of mid-Cretaceous strata (upper Aptian to upper Cenomanian) off central Morocco during Leg 79 of the Deep Sea Drilling Project. Site 545, at the base of the steep Mazagan Escarpment, records a virtually complete succession of hemipelagic sediments of early late Aptian to middle Cenomanian age. Minor faunal recycling occurred throughout much of the upper Aptian to middle Albian part of the sequence (Cores 55 through 41), reflecting bottom currents along the Mazagan Escarpment. This may be related to the strong upwelling regime and high surface water productivity over Site 545 during the latest Aptian through middle Albian. The upwelling system ceased rather abruptly in this area in late middle Albian time. Recycling of older strata by bottom currents also ceased in the late middle Albian and resulted in a slower average accumulation rate in the upper Albian to middle Cenomanian section of Site 545 (Cores 40 through 28). However, intervals of pebbly claystone conglomerates in Cores 40 and 34 record sporadic instability in the slope adjacent to Site 545. Site 547, located only about 15 km seaward, is situated in a small sub-basin adjacent to the basement block drilled by Site 544. It contains an expanded upper Albian to upper Cenomanian sequence as a result of the numerous conglomeratic intervals throughout much of the section. In contrast to Site 545, the conglomerates were not derived from older strata cropping out on the Mazagan Escarpment; rather, they originated penecontemporaneously from a local unstable slope. A detailed biostratigraphic framework based on planktonic foraminifers is established for the mid-Cretaceous sections of Sites 545 and 547 and a new composite zonal scheme is proposed for the early late Aptian through early late Cenomanian interval. Fifty-five species are recognized and illustrated