(Table 1) AMS radiocarbon ages from ODP Sites 169-1033 and 169-1034

This paper explores the paleoseismic record potentially preserved in the upper 40 m of hydraulic piston cores collected in 1996 at two sites in Saanich Inlet, British Columbia, during ocean drilling program (ODP) Leg 169S. The ODP cores are missing 1-2 m of water-rich sediment directly underlying the seafloor, but this sediment is preserved in shorter piston cores collected in 1989 and 1991. The upper part of the ODP cores consists of rhythmically laminated (varved) marine mud with intercalated massive beds, interpreted to be debris flow deposits. Some of the debris flow deposits are linked to past earthquakes, including the 1946 Vancouver Island earthquake (M7.2), a great (M8-9) plate-boundary earthquake at the Cascadia subduction zone in January 1700, and a large crustal or plate-boundary earthquake about 1000 yr ago. Earthquakes may also be responsible for debris flows in about AD 1600, 1500, 1250, 1150, 850, 450, 350, 180, and BC 200, 220, 500, 900, and 1050. If so, the average recurrence interval for moderate to large earthquakes, which trigger debris flows in Saanich Inlet, is about 150 yr. This recurrence interval is broadly consistent with the frequency of moderate to large earthquakes in the region during the historical period. Debris flows, however, can also be triggered by non-seismic processes, making it difficult to assemble a complete earthquake record from the Saanich Inlet cores. We propose that extensive debris flow deposits, emplaced by single large failures or many smaller coincident failures, probably have a seismic origin.

(Table 8.4, Page 220-223) Chemical composition of different growth structures of manganese nodules, SONNE cruise SO78

In the nodule field of the Peru Basin, situated south of the zone of high bioproductivity, a relatively high flux of biogenic matter explains a distinct redox boundary at about 10 cm depth separating very soft oxic surface sediments from stiffer suboxic sediments. Maximum abundance (50 kg/m**2) of diagenetic nodules is found near the calcite compensation depth (CCD), currently at 4250 m. There, the accretion rate of nodules is much higher (100 mm/Ma) than on ridges (5 mm/Ma). Highest accretion rates are found at the bottom of large nodules that repeatedly sink to a level immediately above the redox boundary. There, distinct diagenetic growth conditions prevail and layers of dense laminated Mn oxide of very pure todorokite are formed. The layering of nodules is mainly the result of organisms moving nodules within the oxic surface sediment from diagenetic to hydrogenetic environments. The frequency of such movements is much higher than that of climatic changes. Two types of nodule burial occur in the Peru Basin. Large nodules are less easily moved by organisms and become buried. Consequently, buried nodules generally are larger than surface nodules. This type of burial predominates in basins. At ridges where smaller nodules prevail, burial is mainly controlled by statistical selection where some nodules are not moved up by organisms.

Late Cretaceous and Cainozoic bathyal Ostracoda of DSDP Site 62-463 in the Central Pacific (Fig. 3)

Cainozoic deep-sea ostracod assemblages from the summits of Mid-Pacific guyots point to high levels of endemism possibly as a result of their bathymetric separation from the surrounding sea floor. However, the interpretation of these fossil assemblages is hampered by the paucity of comparative material from surrounding non-guyot sites. Fifteen ostracod assemblages from DSDP Site 463 (Late Cretaceous-Pleistocene) were studied to compare with those from nearby guyots. Three distinct faunal assemblages are recognised at Site 463: Assemblage A (Maastrichtian-Eocene), Assemblage B (Oligocene-Upper Miocene) and Assemblage C (Upper Miocene-Pleistocene) although the palaeoenvironmental significance of these units is unclear. Sixty-two ostracod species are identified, the thirteen most abundant are discussed in the taxonomic section, five of which are described as new. Between 30 and 100% of the species encountered in each sample are considered as endemic to Site 463, while some of the remaining species were previously thought to be endemic to individual guyots. Similarly high levels of endemism on nearby guyots probably reflect an incomplete knowledge of deep-sea ostracod faunas rather than the establishment of geographically or bathymetrically restricted populations. The presence of globally pandemic and geographically widespread taxa on sites such as the Mid-Pacific Mountains, surrounded by abyssal depths which lie below the CCD, indicates that some faunal exchange or migration of ostracods does take place. This must be achieved within the intermediate waters and probably occurs passively.

Age models and stable isotope record of sediment cores from the Atlantic Ocean

The high-resolution delta18O and delta13C records of benthic foraminifera from a 150,000-year long core from the Caribbean Sea indicate that there was generally high delta13C during glaciations and low delta13C during interglaciations. Due to its 1800-m sill depth, the properties of deep water in the Caribbean Sea are similar to those of middepth tropical Atlantic water. During interglaciations, the water filling the deep Caribbean Sea is an admixture of low delta13C Upper Circumpolar Water (UCPW) and high delta13C Upper North Atlantic Deep Water (UNADW). By contrast, only high delta13C UNADW enters during glaciations. Deep ocean circulation changes can influence atmospheric CO2 levels (Broecker and Takahashi, 1985; Boyle, 1988 doi:10.1029/JC093iC12p15701; Keir, 1988 doi:10.1029/PA003i004p00413; Broecker and Peng, 1989 doi:10.1029/GB003i003p00215). By comparing delta13C records of benthic foraminifera from cores lying in Southern Ocean Water, the Caribbean Sea, and at several other Atlantic Ocean sites, the thermohaline state of the Atlantic Ocean (how close it was to a full glacial or full interglacial configuration) is characterized. A continuum of circulation patterns between the glacial and interglacial extremes appears to have existed in the past. Subtracting the deep Pacific (~mean ocean water) delta13C record from the Caribbean delta13C record yields a record which describes large changes in the Atlantic Ocean thermohaline circulation. The delta13C difference varies as the vertical nutrient distribution changes. This new proxy record bears a striking resemblance to the 150,000-year-long atmospheric CO2 record (Barnola et al., 1987 doi:10.1038/329408a0). This favorable comparison between the new proxy record and the atmospheric CO2 record is consistent with Boyle's (1988a) model that vertical nutrient redistribution has driven large atmospheric CO2 changes in the past. Changes in the relative contribution of NADW and Pacific outflow water to the Southern Ocean are also consistent with Broecker and Peng's (1989) recent model for atmospheric CO2 changes.

Shell preservation of Limacina inflata in surface sediments of the Central and South Atlantic

Over 300 surface sediment samples from the Central and South Atlantic Ocean and the Caribbean Sea were investigated for the preservation state of the aragonitic test of Limacina inflata. Results are displayed in spatial distribution maps and are plotted against cross-sections of vertical water mass configurations, illustrating the relationship between preservation state, saturation state of the overlying waters, and overall water mass distribution. The microscopic investigation of L. inflata (adults) yielded the Limacina dissolution index (LDX), and revealed three regional dissolution patterns. In the western Atlantic Ocean, sedimentary preservation states correspond to saturation states in the overlying waters. Poor preservation is found within intermediate water masses of southern origin (i.e. Antarctic intermediate water (AAIW), upper circumpolar water (UCDW)), which are distinctly aragonite-corrosive, whereas good preservation is observed within the surface waters above and within the upper North Atlantic deep water (UNADW) beneath the AAIW. In the eastern Atlantic Ocean, in particular along the African continental margin, the LDX fails in most cases (i.e. less than 10 tests of L. inflata per sample were found). This is most probably due to extensive "metabolic" aragonite dissolution at the sediment-water interface combined with a reduced abundance of L. inflata in the surface waters. In the Caribbean Sea, a more complex preservation pattern is observed because of the interaction between different water masses, which invade the Caribbean basins through several channels, and varying input of bank-derived fine aragonite and magnesian calcite material. The solubility of aragonite increases with increasing pressure, but aragonite dissolution in the sediments does not simply increase with water depth. Worse preservation is found in intermediate water depths following an S-shaped curve. As a result, two aragonite lysoclines are observed, one above the other. In four depth transects, we show that the western Atlantic and Caribbean LDX records resemble surficial calcium carbonate data and delta13C and carbonate ion concentration profiles in the water column. Moreover, preservation of L. inflata within AAIW and UCDW improves significantly to the north, whereas carbonate corrosiveness diminishes due to increased mixing of AAIW and UNADW. The close relationship between LDX values and aragonite contents in the sediments shows much promise for the quantification of the aragonite loss under the influence of different water masses. LDX failure and uncertainties may be attributed to (1) aragonite dissolution due to bottom water corrosiveness, (2) aragonite dissolution due to additional CO2 release into the bottom water by the degradation of organic matter based on an enhanced supply of organic matter into the sediment, (3) variations in the distribution of L. inflata and hence a lack of supply into the sediment, (4) dilution of the sediments and hence a lack of tests of L. inflata, or (5) redeposition of sediment particles.

Surface sediment data, CaCO3 and TOC

Modern sedimentary total organic carbon (TOC) content as a proxy for surface water export production was mapped on the shelf and on the upper continental slope of the Benguela upwelling system using 137 core tops. Shelf maxima in TOC can be correlated with maxima in surface water productivity. On the slope, high TOC contents are observed offshore from sites of strong modern upwelling. Estimates of modern TOC mass accumulation rates (MAR) show that approximately 85% of the total is accumulating on the shelf. TOC MAR were calculated, mapped, and budgeted for the Holocene and for the Last Glacial Maximum (LGM) using 19 sediment cores from the continental slope. During the LGM, centers of deposition and production have migrated offshore with respect to their Holocene positions. TOC accumulation on the continental slope was approximately 84% higher during the LGM than during the Holocene, possibly reflecting enhanced productivity. The TOC distribution patterns and sediment echo sounding data suggest that undercurrents strongly influence the sedimentation off Namibia. Winnowing and focusing result in great lateral heterogeneity of sedimentation rates and sediment properties. Individual cores therefore do not necessarily reflect general changes in export production. These results highlight the need for detailed regional studies based on a large number of sediment cores for highly heterogeneous high-productivity areas in order to derive general statements on total fluxes.