ALBERT

Beschreibung: We present modern B/Ca core-top calibrations for the epifaunal benthic foraminifer Nuttallides umbonifera and the infaunal Oridorsalis umbonatus to test whether B/Ca values in these species can be used for the reconstruction of paleo-D[[CO3]2-]. O. umbonatus originated in the Late Cretaceous and remains extant, whereas N. umbonifera originated in the Eocene and is the closest extant relative to Nuttallides truempyi, which ranges from the Late Cretaceous through the Eocene. We measured B/Ca in both species in 35 Holocene sediment samples from the Atlantic, Pacific and Southern Oceans. B/Ca values in epifaunal N. umbonifera (~ 85-175 µmol/mol) are consistently lower than values reported for epifaunal Cibicidoides (Cibicides) wuellerstorfi (130-250 µmol/mol), though the sensitivity of D[[CO3]2-] on B/Ca in N. umbonifera (1.23 ± 0.15) is similar to that in C. wuellerstorfi (1.14 ± 0.048). In addition, we show that B/Ca values of paired N. umbonifera and its extinct ancestor, N. truempyi, from Eocene cores are indistinguishable within error. In contrast, both the B/Ca (35-85 µmol/mol) and sensitivity to D[[CO3]2-] (0.29 ± 0.20) of core-top O. umbonatus are considerably lower (as in other infaunal species), and this offset extends into the Paleocene. Thus the B/Ca of N. umbonifera and its ancestor can be used to reconstruct bottom water D[[CO3]2?], whereas O. umbonatus B/Ca appears to be buffered by porewater [[CO3]2-] and suited for constraining long-term drift in seawater B/Ca.

Beschreibung: Data were presented to compare pore fluids from Sites 1037 and 1038 in the Escanaba Trough, Gorda Ridge. Site 1037 constitutes the reference site, and Site 1038 is the hydrothermally affected site. The program was undertaken for two purposes: (1) to make a detailed analysis of the halide chemistry of these two sites, with the specific aim of discerning any potential differences in the generation of dissolved halides as a result of sediment diagenesis in these drill sites and (2) to investigate the geochemistry of Ba2+ and Mn2+ at these two sites to discover potential hydrothermal effects reflected in the concentration-depth distributions of these elements.

Beschreibung: During Ocean Drilling Program Leg 198, Sites 1207, 1208, 1212, 1213, and 1214 were drilled on Shatsky Rise, coring Lower to mid-Cretaceous successions of nannofossil chalk, porcellanite, and chert. Although recovery was poor, these sites yielded an outstanding record of calcareous nannoplankton, providing valuable data concerning the evolutionary succession and paleobiogeography of the largest Cretaceous marine habitat. Mid-Cretaceous sections (Aptian-Cenomanian) were recovered at all sites, and Site 1213 includes an apparently complete Berriasian-Hauterivian section. Biostratigraphic dating is problematic in places because of the absence or rarity of zonal fossils of both Boreal and Tethyan affinity. The majority of nannofossil assemblages are relatively typical of this age, but there are clear differences that set them apart from coeval epicontinental assemblages: for example, Lithraphidites carniolensis is common to abundant throughout and was most likely an oceanic-adapted taxon; the cold- to temperate-water species Crucibiscutum salebrosum, Repagulum parvidentatum, and Seribiscutum primitivum are entirely absent, indicating the persistence of tropical, warm surface water temperatures; and the warm-water species Hayesites irregularis is common. Most striking, however, is the virtual absence of Nannoconus and Micrantholithus, both taxa that were conspicuous and often common components of many Tethyan and Atlantic nannofloras. These forms were almost certainly neritic adapted and usually absent in deep open-ocean settings away from guyots and platforms. Other Tethyan taxa are also absent or rare and sporadically distributed (e.g., Calcicalathina oblongata, Conusphaera spp., Tubodiscus verenae, and Lithraphidites bollii), and factors related to neritic environments presumably controlled their distribution. Site 1213 also records extended Early Cretaceous ranges for species previously thought to have become extinct during the Late Jurassic (e.g., Axopodorhabdus cylindratus, Hexapodorhabdus cuvillieri, and Biscutum dorsetensis), suggesting these species became Pacific-restricted prior to their extinction. Watznaueria britannica may also have been a species with Pacific affinities before reexpansion of its biogeography in the early Aptian. One new genus (Mattiolia) and thirteen new species (Zeugrhabdotus clarus, Zeugrhabdotus petrizzoae, Helicolithus leckiei, Rhagodiscus amplus, Rhagodiscus robustus, Rhagodiscus sageri, Rhagodiscus adinfinitus, Tubodiscus bellii, Tubodiscus frankiae, Gartnerago ponticula, Haqius peltatus, Mattiolia furva, and Kokia stellata) are described from the Shatsky Rise Lower Cretaceous section.

Beschreibung: Eight sites were drilled on Shatsky Rise during Ocean Drilling Program Leg 198. All sites (1207-1214) recovered Cretaceous sediments ranging in age from Maastrichtian to Berriasian. In the Upper Cretaceous, Maastrichtian-Campanian nannofossil oozes were recovered at Sites 1207-1212. At Sites 1207 and 1212 Santonian-Cenomanian oozes were also recovered from chert-dominated sequences, but this interval contains multiple hiatuses. Sites 1209-1211 terminated in chert. Calcareous nannofossil assemblages are abundant, diverse, and relatively well preserved throughout, but biostratigraphy is problematic in places due to missing or rare and sporadically distributed marker species. In the upper Maastrichtian, the first occurrences (FOs) of Micula murus and Lithraphidites quadratus appear to be reversed in most sections, and in the Campanian, Reinhardtites levis, Misceomarginatus pleniporus, and Eiffellithus parallelus are absent or virtually absent, probably due to biogeographic limitations. However, a number of previously unused bioevents were recognized that may prove to be useful Pacific-wide, including the FO of Ceratolithoides ultimus (in Subzone UC20dTP) and the last occurrence (LO) of Tegumentum stradneri (in Subzone UC20bTP) in the upper Maastrichtian; the FOs of Micula praemurus and consistent Cribrocorona gallica, the LOs of Zeugrhabdotus bicrescenticus and Cribrocorona echinus, and the FO of C. echinus lower in the Maastrichtian; and the LO of Rucinolithus? magnus (in Zone UC16), FO of R.? magnus (in Subzone UC15bTP), FO of Perchnielsenella stradneri (in Subzone UC15a/bTP), and FO of Ceratolithoides indiensis (Subzone UC14d-UC15dTP) in the Campanian. The assemblages are distinctly different in composition from those of the Atlantic Ocean and its marginal basins but show similarities with some Indian Ocean nannofloras, and so these sections will provide important insights into the paleobiogeography and paleoecology of Late Cretaceous nannoplankton. The assemblages are broadly dominated by cosmopolitan taxa such as Prediscosphaera, Watznaueria, and Retecapsa, but abundance data together with key occurrences and absences reveal a distinct paleobiogeographic character. High-latitude species such as Seribiscutum primitivum, Repagulum parvidentatum, and Nephrolithus frequens are completely absent from the Shatsky sites. The common presence of Ceratolithoides, Uniplanarius, Micula, and Cylindralithus/Perchnielsenella are indicative of tropical to subtropical paleolatitudes and reflect an open-ocean setting.

Beschreibung: Massive sulfide samples from the Bent Hill area were analyzed for 230Th/234U and 231Pa/235U disequilibria. Apparent ages calculated from these ratios are between 8.2 and 〉300 ka. Concordant ages were found for only three samples that originate near the surface from the clastic sulfide zone and suggest "true" ages of between 8.5 and 16.0 ka (mean of 230Th and 231Pa ages). The uranium vs. depth distribution in the Bent Hill Massive Sulfide deposit suggests an open system for uranium for the deeper part of the deposit, which was probably caused by extensive recrystallization processes inhibiting true age determinations.

Beschreibung: Phospholipid fatty acids were measured in samples of 60°-130°C sediment taken from three holes at Site 1036 (Ocean Drilling Program Leg 169) to determine microbial community structure and possible community replacement at high temperatures. Five of six samples had similar concentrations of phospholipid fatty acids (2-6 pmol/g dry weight of sediment), and biomass estimates from these measurements compare favorably with direct microscopic counts, lending support to previous microscopic measures of deep sedimentary biomass. Very long-chain phospholipid fatty acids (21 to 30 carbons) were detected in the sediment and were up to half the total phospholipid fatty acid measured; they appear to increase in abundance with temperature, but their significance is not known. Community composition from lipid analysis showed that samples contained standard eubacterial membrane lipids but no detectable archaeal lipids, though archaea would be expected to dominate the samples at high temperatures. Cluster analysis of Middle Valley phospholipid fatty acid compositions shows that lipids in Middle Valley sediment samples are similar to each other at all temperatures, with the exception of very long-chain fatty acids. The data neither support nor deny a shift to a high-temperature microbial community in hot cores, so at the present time we cannot draw conclusions about whether the microbes observed in these hot sediments are active.

Beschreibung: Sulfide mineral major and trace element analyses were performed on more than 50 polished slabs representing mineralization from three seafloor hydrothermal massive sulfide deposits. Samples from the Bent Hill and ODP Mound massive sulfide deposits, both on the Juan de Fuca Ridge, can be contrasted with samples from the Trans-Atlantic Geotraverse (TAG) hydrothermal mound on the Mid-Atlantic Ridge. The massive sulfide at Bent Hill is predominantly pyrite and pyrrhotite, with increasing amounts of copper-bearing sulfide minerals at the base of the massive sulfide body and through the stockwork to an interval 200 m below seafloor that hosts high copper mineralization (Deep Copper Zone). ODP Mound contains much more abundant sphalerite and copper-bearing sulfides as compared to either Bent Hill or TAG, which are predominantly pyrite with much less abundant chalcopyrite. Copper-bearing sulfides from the Deep Copper Zone beneath Bent Hill and the lowest sampled interval of ODP Mound are petrographically and chemically similar, but distinct from copper-bearing minerals higher in either sequence.

Beschreibung: The results of 72 index properties analyses and 29 high-pressure velocity experiments on samples of sediment, basalt, and sulfide rocks recovered during Leg 169 of the Ocean Drilling Program are presented. The large sample set was subjected to shore-based index properties measurements from which wet bulk densities (b), grain densities (g), and porosities were calculated. The majority of samples are from Sites 856 and 1035 in the Bent Hill area of Middle Valley, part of the northern Juan de Fuca Ridge. Four basalts are from Holes 1037B and 1038I drilled in the Escanaba Trough of the Gorda Ridge. Reentry drilling of Hole 856H below 93.8 meters below seafloor (mbsf) resulted in penetration of a complete Bent Hill Massive Sulfide (BHMS) area reference section below the massive sulfide deposit drilled during Leg 139. Physical properties samples were obtained from the underlying sulfide feeder zone section of mineralized sediments (Unit VI), a deeper interbedded hemipelagic and turbiditic sediment interval (Unit II), the intercalated sills and sediment of "hydrothermal basement" (Unit VII), and the basaltic flows of interpreted oceanic basement (Unit VIII). Elevated-pressure velocity measurements of sediments from Units II and VI, sediment interbeds of Unit VII, and basalts of Unit VIII were made for the first time. The presence of sulfide minerals as disseminations, blebs, and vein infillings affects the velocity and density signatures of sediment samples from cores in the vicinity of the BHMS (Site 1035). Densities, velocities, and porosities of massive sulfides (Unit V; Holes 1035F and 1035H) and basaltic sills (Hole 856H) are comparable to Leg 139 data for sulfides from 0.0 to 93.8 mbsf in Hole 856H and Hole 857D sills.

Beschreibung: Permeability, electrical resistivity, and thermal conductivity measurements were performed on samples from the Bent Hill area of the Middle Valley on the northern Juan de Fuca Ridge. Thermal conductivity measurements were also made on samples from the Trans-Atlantic Geotraverse (TAG) hydrothermal area in the Mid-Atlantic Ridge for direct comparison with previous studies and the Middle Valley results. Electrical resistivity and permeability measurements were made as a function of confining pressure on 15 samples comprising different lithologic compositions found in the Bent Hill area. The effect of pressure on electrical resistivity values is relatively small and the observed frequency dependence is highly controlled by the sulfide content in these rocks. Permeabilities are in the 10**-16 to 10**-20 m**2 (0.1-100 µD) range. Although permeability does not recover in samples that undergo significant permanent deformation, the elastic permeability dependence on confining pressure is relatively small. Permeability correlates with porosity. Permeability anisotropy correlates with the presence of oriented sulfide veins with increased flow parallel to the veins. Thermal conductivity measurements made on 41 samples from Middle Valley and 9 samples from the TAG area show systematic variations due to changes in composition and a weak relationship with porosity for sedimentary samples from Middle Valley. A comparison between the divided-bar and the half-space needle-probe methods of measuring thermal conductivity shows good agreement for the Leg 169 measurements unlike previous results from Legs 139 and 158. The discrepancies observed in earlier studies seem to be related to the long times used in the older measurements for the optimal T vs. ln(t) data interval. The apparatus used during Leg 169 was smaller, sampled a smaller volume of core, and in high conductivity material was not influenced by boundary effects.

Beschreibung: Sequences of late Pliocene to Holocene sediment lap onto juvenile igneous crust within 20 km of the Juan de Fuca Ridge in northwestern Cascadia Basin, Pacific Ocean. The detrital modes of turbidite sands do not vary significantly within or among sites drilled during Leg 168 of the Ocean Drilling Program. Average values of total quartz, total feldspar, and unstable lithic fragments are Q = 35, F = 35, and L = 30. Average values of monocrystalline quartz, plagioclase, and K-feldspar are Qm = 46, P = 49, and K = 5, and the average detrital modes of polycrystalline quartz, volcanic-rock fragments, and sedimentary-rock plus metamorphic-rock fragments are Qp = 16, Lv = 43, and Lsm = 41. Likely source areas include the Olympic Peninsula and Vancouver Island; sediment transport was focused primarily through the Strait of Juan de Fuca, Juan de Fuca Channel, Vancouver Valley, and Nitinat Valley. Relative abundance of clay minerals (〈2-µm-size fraction) fluctuate erratically with depth, stratigraphic age, and sediment type (mud vs. turbidite matrix). Mineral abundance in mud samples are 0%-35% smectite (mean = 8%), 18%-59% illite (mean = 40%), and 29%-78% chlorite + kaolinite (mean = 52%). We attribute the relatively low content of smectite to rapid mechanical weathering of polymictic source terrains, with little or no input of volcanic detritus from the Columbia River. The scatter in clay mineralogy probably was caused by converging of surface currents, turbidity currents, and near-bottom nepheloid clouds from several directions, as well as subtle changes in glacial vs. interglacial weathering products.