ALBERT

Description: During Leg 105 of the Ocean Drilling Program, a series of 11 holes was drilled at three sites along a north-south transect in Baffin Bay and the Labrador Sea. Intermittent recovery and drilling disturbance, resulting in part from the harsh weather conditions encountered, hampered magnetostratigraphic study. In particular, incomplete recovery of undisturbed sediment and sparse biostratigraphic control make it difficult to correlate the polarity zones observed in sediments recovered at Site 645 in Baffin Bay with the geomagnetic polarity time scale. However, the undisturbed Pliocene-Pleistocene sediments recovered using the advanced piston corer (APC) at Sites 646 and 647 yield polarity sequences that are readily correlated with the time scale. Deeper sequences cored using the extended core barrel (XCB) corer at Site 646 provide a coarse polarity sequence that, in conjunction with the available biostratigraphic data, may be correlated tentatively with late Miocene reversal sequences. The polarity record obtained from a relatively undisturbed upper Eocene sequence recovered from Hole 647A using the rotary core barrel (RCB) is correlated with Chronozones C19 through C18.

Description: Radiolaria are present in frequencies ranging from rare to abundant and with generally moderate to good preservation quality in Leg 104 sediments younger than 22 Ma. Preservation degrades in progressively younger sediments, and upper Pliocene to mid-Pleistocene radiolaria were found only at Site 644, where sporadic assemblages of moderate to poorly preserved specimens persist to approximately 0.75 Ma. Radiolaria are essentially absent in Leg 104 recovery older than basal Miocene. The stratigraphic ranges of 55 taxa of radiolaria are documented in 451 samples from the biosiliceous recoveries of Holes 642B, 642C, 642D, 643A, and 644A. The stratigraphic ranges of 25 of these species are used as boundary criteria for a new system of 28 Neogene zones and subzones that are used to characterize approximately 72% of the past 22 m.y. of sedimentation on the Vriring Plateau. This new scheme is intended to supercede the NRS zones provisionally proposed in the Leg 104 Initial Reports. The applicability of this regional biozonation beyond the Wring and Iceland Plateaus is not presently known. The radiolaria biostratigraphy serves as a basis for inferring a sequence of hiatuses and faunal overturns that may be associated with sea-level low stands and consequent cold-water isolation of the Norwegian Sea. Twenty-one new taxa are described as follows: Actinomma henningsmoeni, Actinomma livae, Actinomma mirabile, Actinomma plasticum, Ceratocyrtis broeggeri, Ceratocyrtis manumi, Ceratocyrtis stoermeri, Clathrospyris vogti, Corythospyris hispida, Corythospyris jubata sverdrupi, Corythospyris reuschi, Crytocapsella ampullacea, Cyrocapsella kladaros, Gondwanaria japonica kiaeri, Hexalonche esmarki, Larcospira bulbosa, Phormospyris thespios, Pseudodicytophimus amundseni, Spongotrochus vitabilis, Spongurus cauleti, and Tessarastrum thiedei.

Description: Benthic foraminifers have been studied in about 900 samples from Sites 642, 643, and 644 (ODP Leg 104, Voring Plateau), ranging in age from Eocene to Holocene. This sequence has been subdivided into seven assemblage zones. The Eocene to middle Miocene deposits are characterized by an agglutinated fauna. This reflects an environment causing dissolution of calcareous tests rather than the original living fauna. The upper Miocene to middle Pliocene deposits contain a diverse benthic foraminiferal fauna dominated by calcareous forms. The uppermost part of the sediment record, deposited during late Pliocene to Holocene, is characterized by many barren intervals and samples containing shallow-water species as well as ice-rafted material indicating glacial periods. Interglacials are reflected in samples containing a true oceanic foraminifer assemblage and no coarse clastic material.

Description: Possible genetic relationships between syn- and post-depositional processes and sediment microstructure were investigated. Samples from cores at Sites 646 and 647 of Ocean Drilling Program (ODP) Leg 105 included examples of bottom current deposition (contourites), turbidity current deposition, consolidation, and diagenesis. Examination of nearly 200 micrographs of 14 samples from Site 646 and 13 samples from Site 647 leads to the conclusion that sedimentation processes do not appear to have an obvious influence on fabric. The effects of post-depositional processes, such as bioturbation, coring disturbance, and even remolding, appear to be less significant than one might expect as a result of the relatively coarse grain size of the sediments studied. Consolidation resulting from increased overburden stress results in increased particle alignment and compression of fabric elements with depth. The transition from open, random fabric in shallow samples to preferred orientation at depth represents the only change in these sediments that can be ascribed directly to a specific depositional or post-depositional process. Mineralogical variations, owing to changes in weathering processes and growth of authigenic/diagenetic minerals, also have a pronounced effect on sediment fabric.