Chemial and isotope compositions of rocks from the West Antarctic

The paper is devoted to a marine geophysical-geological research in the West Antarctic. This researche contributed to establishing the base geodesic network of the West Antarctic and supplemented geokinematic monitoring based on this network with geophysical and geologic information on structure and features of geomorphological and tectonic development of the South Ocean floor. Collected materials allow to conclude about the inhomogeneity of the Scotia Sea floor and about combination of fragments of a continental massif with young rift structures in conditions of the upwelling mantle. The ancient continental bridge, faunal connections between the South America and the West Antarctic has been destroyed by processes of destruction, taphrogeny and sea floor spreading. Structures of the Scotia and Caribbean Seas, North Fiji and Arctic Basins are similar.

(Table T1) Calcium carbonate content of sediments from ODP Leg 172 sites

Visual-domain diffuse reflectance data collected aboard the JOIDES Resolution with the Minolta spectrometer CM-2002 during Ocean Drilling Program Leg 172 have been used to estimate successfully the carbonate content of sediments. Calibration equations were developed for each site and for each lithostratigraphic unit (or subunit at Site 1063) using multiple linear regression on raw as well as pretreated reflectance spectra (i.e., first-order derivation and squaring of raw reflectance spectra) for a total of 4141 direct carbonate measurements. The root-mean-square errors of 4% to 7% are within the range of previous estimates using diffuse reflectance data and are acceptable for the general extensive range of carbonate contents (i.e., 0-70 wt%) that characterize sedimentation at Leg 172 sites.

Chemical composition of rocks from the Marcus-Necker Rise

The Marcus Necker Rise has two geologically distinct parts: the western one is composed of the Marcus Wake seamounts and the eastern one of the Wake-Necker seamounts. The first contain differentiated alkali basaltoids, while the second show a distinctive prolonged and complicated history. The latter contain Early Cretaceous olivine basalts and Late Cretaceous alkali and hornblende basaltoids.

(Appendix B) Carbonate fraction geochemistry at DSDP Hole 72-516F

This paper presents data on trace elements (Sr, Mg, Na, K, Mn, Fe, Ni, Cr) and isotopes (13C, 18O) on the carbonate fraction of bulk sediments from the Coniacian to Paleocene samples of Hole 516F. Relationships of trace elements to mineralogy and stratigraphic position are discussed at length, with special emphasis on 1) the differences between Hole 516F and other oceanic sites, and 2) the transitions observed at the Cretaceous/Tertiary boundary. Isotope data are compared to those obtained in other localities of the same age. The sections show the same major 13C variations at the Cretaceous/Tertiary boundary, indicating that this event is a planetary phenomenon.

(Table 2) Chemical composition of rocks from the northern Sea of Japan

In terms of physical and genetic features studied nodules are assigned to the sedimentational manganese-iron type (Canary Basin) and to the iron-containing type (Guyana Basin). They are enriched in Fe, Co and Pb and depleted in Mn, Ni, Cu, and Zn. Cores of the nodules from the Canary Basin consist primarily of peridotite, gabbro, dolerite, and metamorphic rock. Great predominance of peridotite and gabbro indicates that blocks of ocean crust underwent considerable displacement, bringing the third and fourth layers of a crust to the surface.

Diagenetic development of deep-sea carbonate sediments from DSDP Holes 30-228, 30-289 and 33-316

Laboratory measurements of ultrasonic velocity (VP, VS) and attenuation (QP**-1, QS**-1) in deep-sea carbonate sequences at DSDP Sites 288, 289 and 316 in the equatorial Pacific were made in conjunction with studies of sediment density, porosity and pore geometry in order to investigate the role of diagenesis in the development of physical properties. Bulk porosity decrease appears to be related more significantly to depth of burial than to age of strata. Both depth of burial and age, however, are important factors controlling the modal pore diameter. In deep-burial diagenesis the modification of pore geometry is influenced by the presence of silica during diagenesis. In carbonate sequences at the three DSDP sites studied, shear wave attenuation anisotropy (QSHH**-1/QSHV**-1) correlates with the shear wave velocity anisotropy. Pore orientation, resulting from overburden pressure and other deep-burial diagenetic processes, is an important factor controlling the increase of VP anisotropy with age and depth of burial. On the basis of observed minor changes in anisotropy values with increasing pressure for some samples, other contributions to VP anisotropy such as grain orientation and bedding lamination cannot be ruled out.