Benthic foraminiferal number of specimens in Cretaceous samples of various DSDP and ODP Sites (Table 2)

Benthic foraminifera from 24 DSDP/ODP sites were investigated to assess their global horizontal and vertical distribution in the deep-sea environment at the end of the Cretaceous period. The samples analyzed are from the late Maastrichtian and within the planktic foraminiferal Abathomphus mayaroensis Zone from a wide range of oceans and paleolatitudes, including the low-latitude Sites 10 and 384 (Atlantic Ocean), 47, 171, 305, and 465 (Pacific Ocean), the mid-latitude Sites 20, 111, 356, 363, 516, 525, 527, 548, and 605 (Atlantic Ocean), 216, 217, and 758 (Indian Ocean), and the high-latitude Sites 208 (Pacific Ocean), 689,698,700,738 and 750 (Southern Ocean). Correspondence analysis, based on the 75 most common taxa, shows a clear biogeographic trend along the first correspondence axis by arranging the sites in paleolatitudinal order. The assemblages from the Tethyan Realm (i.e., low latitudes) are marked by abundant heavily calcified buliminids (such as Bulimina incisa, B. trinitatensis, B. velascoensis, and Reussella szajnochae) and Aragonia spp., whereas high-latitude faunas are characterized by abundant Alabamina creta, Gyroidinoides quadratus, and Pullenia coryelli. The results indicate that the faunas at low and high latitudes, respectively, were influenced by quite different environmental conditions. This is based on the much higher abundance of infaunal morphotypes at low and mid latitudes compared to high latitudes, suggesting that the biogeographic trend found in the data set coincides with the trophic regime at the various sites. The results also provide support for the hypothesis that postulates two simultaneous sources and mechanisms for deep-water formation during the Late Cretaceous, including warm, saline deep water produced by evaporation at low (equatorial) latitudes in contrast to the formation of cold deep waters at high (southern) latitudes.

(Table T1) Permeability, electrical resistivity and density of ODP Hole 193-1188A and Site 193-1189 minicores, PACMANUS field

Magmatic fluids, heat fluxes, and fluid/rock interactions associated with hydrothermal systems along spreading centers and convergent margins have a significant impact on the genesis of major sulfide deposits and biological communities. Circulation of hydrothermal fluids is one of the most fundamental processes associated with localized mineralization and is controlled by inherent porous and permeable properties of the ocean crust. Heat from magmatic intrusions drives circulation of seawater through permeable portions of the oceanic crust and upper mantle, discharging at the seafloor as both focused high-temperature (250°-400°C) fluids and diffuse lower-temperature (<250°C) fluids. This complex interaction between the circulating hydrothermal fluids and the oceanic basement greatly influences the physical properties and the composition of the crust (Thompson, 1983; Jacobson, 1992, doi:10.1029/91RG02811; Johnson and Semyan, 1994, doi:10.1029/93JB00717). During Ocean Drilling Program (ODP) Leg 193, 13 holes were drilled in the PACMANUS hydrothermal system (Binns, Barriga, Miller, et al., 2002, doi:10.2973/odp.proc.ir.193.2002). The hydrothermal system consists of isolated hydrothermal deposits lined along the main crest of the Pual Ridge, a 500- to 700-m-high felsic neovolcanic ridge in the eastern Manus Basin. The principal drilling targets were the Snowcap (Site 1188) and Roman Ruins (Site 1189) active hydrothermal fields. Samples from these two sites were used for a series of permeability, electrical resistivity, and X-ray computed tomography measurements.

Calcium carbonate in sediments at DSDP Leg 92

The carbonate contents of sediments recovered at Leg 92 Sites 597, 598, and 601 were determined at 5-cm intervals. The long-term record of carbonate variation at Sites 597 and 598 shows the effect of decreasing dilution by hydrothermal phases as the sites moved away from the ridge crest at which they formed. Superimposed on this trend are high-amplitude variations in carbonate content. In the lower portions of Sites 597 and 598 the high-amplitude variations have a duration of a few hundred thousand years. The upper portion of the sediment column at both sites was deposited below the lysocline, and high-amplitude variations in this interval represent 1 to 2 m.y. The data suggest that only very intense carbonate dissolution events can be identified reliably at sites with low accumulation rates. At sites like Site 598, where the sedimentation rate is higher, the details of carbonate variation can be correlated with the carbonate lithostratigraphies developed for sites in the equatorial and North Pacific oceans.

Revised Cenozoic hiatus database

The differential effects of climate change, sea level, and water mass circulation on deposition/erosion of marine sediments can be constrained from the distribution of unconformities in the world's oceans. I identified temporal and depth patterns of hiatuses ("hiatus events") from a large and chronologically well constrained stratigraphic database of deep-sea sediments. The Paleogene is characterized by few, several million year long hiatuses. The most significant Cenozoic hiatus event spans most of the Paleocene. The Neogene is characterized by short, frequent hiatus events nearly synchronous in shallow and deep water sediments. Epoch boundaries are characterized by peaks in deep water hiatuses possibly caused by an increased circulation of corrosive bottom water and sediment dissolution. The Plio-Pleistocene is characterized by a gradual decrease in the frequency of hiatuses. Future studies will focus on the regional significance of the hiatus events and their possible causes.

Stable oxygen and carbon isotope data for planktic and benthic foraminifera from southern Atlantic of DSDP Hole 74-525A and ODP Hole 113-690C

Published stable isotope records in marine carbonate are characterized by a positive d18O excursion associated with a negative d13C shift during the early Maastrichtian. However, the cause and even the precise timing of these excursions remain uncertain. We have generated high-resolution foraminiferal stable isotope and gray-scale records for the latest Campanian to early Maastrichtian (73-68 Ma) at two Ocean Drilling Program sites, 525 (Walvis Ridge) and 690 (Weddell Sea). We demonstrate that the negative d13C excursion is decoupled from the d18O increase with a lag of about 600 ka. Our d13C records (both planktic and benthic) show an amplitude for the negative excursion of 0.7 per mill that falls between about 72.1 and 70.7 Ma. Our planktic d18O records indicate an overall increase of 1.2 per mill from 73 to 68 Ma at Site 690, whereas at Site 525 they record a slightly smaller increase (1 per mill) that peaks around 70.1 Ma with decreasing values thereafter. Our benthic d18O data indicate an increase of 1.5 per mill at Site 525 and 0.7 per mill at Site 690 between about 71.4 and 69.9 Ma. Benthic d18O values show different baseline values at the two sites before and after the excursion, but the larger increase at Site 525 means that the values attained at the peak of the excursion are similar at the two sites. We interpret this observation in terms of water mass changes. The excursion is interpreted to reflect a cooling of bottom waters in response to the strengthening contribution of intermediate- to deep-water production in the high southern latitudes rather than increased ice volume. The associated carbon cycle perturbations that we observe are interpreted to reflect a weakening of surface water stratification and increased productivity, as supported by our gray value data.

Latitudinal variation in the planktic foraminifer Contusotruncana contusa in the terminal Cretaceous ocean

The morphological variability (coiling properties, size and shape) of the planktic foraminifer Contusortuncana contusa (Cushman) in the terminal Cretaceous ocean was examined at eight deep-sea sites and two continental sections from low (16°) to middle (42°) paleolatitudes in both hemispheres. The material used in this study includes samples from the South Atlantic (DSDP Sites 356, 527 and 525A), North Atlantic (Sites 384 and 548A), Indian and Pacific Oceans (DSDP Site 465A and ODP Sites 761C and 762C) and Tethyan Ocean (outcrop sections from El-Kef and Caravaca). On average 45 specimens from two samples per location were analysed, from an interval corresponding approximately to the last 60 kyr of the Cretaceous. No differences in coiling direction (dextral proportions were > 90% in all samples), percentage of kummerform specimens (usually > 50%) and number of chambers in the last whorl (4-5) were observed between the sites. Both test size (expressed as spiral outline area and test volume) and total number of chambers increase significantly towards lower latitudes. Similarly, test conicity, examined by shape coordinate and eigenshape methods, and angularity of the spiral outline show a rather continuous, slight increase towards lower latitudes. Kummerform specimens of C. contusa were slightly larger and more conical than normalforms and possessed substantially more chambers (both totally and in the last whorl). A principal components analysis of the sample means of five variables describing size and shape clearly distinguished high-latitude sites (525A, 527, 548A, 761C and 762C) from low-latitude sites (384, 465A, Caravaca and El-Kef). Specimens from Site 356 are transitional with respect to those two groups. The results indicate: (1) considerable morphological variation in C. contusa during the terminal Cretaceous comparable to that known in many Recent planktic foraminiferal species and (2) a geographical distribution of this variation corresponding to previously suggested biogeographic schemes based on quantitative analysis of planktic foraminiferal assemblages. Despite the differences in sample means, the overall morphology of C. contusa overlaps among the sites studied, supporting the classification of all C. contusa morphotypes as a single species. Similarly, no discrete morphologic groups could be distinguished within any of the samples.

Annotated record of the detailed examination of Mn deposits from DEEPSONDE Expedition stations near the East Pacific Rise

Basalts from the base of a small seamount on ~1.5-m.y.-old crust west of the East Pacific Rise (EPR) at 9°N are intermediate in chemical and isotopic composition between light-rare-earth-element-depleted tholeiite (normal midocean ridge basalt (MORB)) and alkali basalt. Like oceanic alkali basalt, these rocks contain significantly more Ba, K, P, Sr, Ti, U, and Zr than normal MORB. Since the absolute abundances of these elements are still well below alkali basalt levels, the label transitional is adopted for these basalts. A series of fractionated MORB also occurs in this area, northwest of the Siqueiros Fracture Zone - Transform Fault. The normal tholeiites are either olivine-plagioclase or plagioclase-clinopyroxene phyric, while the transitional basalts are spinel-olivine phyric. Fractional crystallization quantitatively accounts for the chemical variability of the tholeiitic series but not for the transitional basalts. The tholeiitic series probably evolved in a crustal magma chamber ~4 km below the crest of the East Pacific Rise. 143Nd/144Nd and other chemical data suggest that the large-ion-lithophile-enriched transitional basalts may represent a hybrid of normal MORB and Siqueiros area alkali basalt. Incompatible element plots of K, P, and U indicate possible derivation of the transitional basalts by magma mixing. Magma mixing of unfractionated normal MORB and Siqueiros alkali basalt has been quantified. Derivation of the transitional basalts from a 1:1 mixture is supported by all available chemical data, including Cr, Cu, Nd, Ni, Sm, Sr, U, and V. This magma mixing apparently occurred at ?<~30 km depth within a few tens of kilometers from the EPR axis. These Siqueiros area EPR transitional basalts are compared with Mid-Atlantic Ridge (MAR) transitional basalts from the Iceland and Azores areas. The Siqueiros area basalts reflect a profound chemical and isotopic heterogeneity in the upper mantle, similar to that found along the MAR. Unlike the MAR, the EPR shows no evidence of plumelike bulges and associated large-scale outpourings of nonnormal MORB resulting from these mantle heterogeneities. Siqueiros alkali basalt and MORB, as well as transitional basalt and MORB, were recovered from single dredge hauls. Such close spatial and temporal proximity of the inferred mantle sources places severe constraints on geometric and physicochemical upper mantle models.

Spectral analysis of seabed elevation from the Danish Wadden Sea

Bedforms both reflect and influence shallow water hydrodynamics and sediment dynamics. A correct characterization of their spatial distribution and dimensions is required for the understanding, assessment and prediction of numerous coastal processes. A method to parameterize geometrical characteristics using two-dimensional (2D) spectral analysis is presented and tested on seabed elevation data from the Knudedyb tidal inlet in the Danish Wadden Sea, where large compound bedforms are found. The bathymetric data were divided into 20x20 m areas on which a 2D spectral analysis was applied. The most energetic peak of the 2D spectrum was found and its energy, frequency and direction were calculated. A power-law was fitted to the average of slices taken through the 2D spectrum; its slope and y-intercept were calculated. Using these results the test area was morphologically classified into 4 distinct morphological regions. The most energetic peak and the slope and intercept of the power-law showed high values above the crest of the primary bedforms and scour holes, low values in areas without bedforms, and intermediate values in areas with secondary bedforms. The secondary bedform dimensions and orientations were calculated. An area of 700x700 m was used to determine the characteristics of the primary bedforms. However, they were less distinctively characterized compared to the secondary bedforms due to relatively large variations in their orientations and wavelengths. The method is thus appropriate for morphological classification of the seabed and for bedform characterization, being most efficient in areas characterized by bedforms with regular dimensions and directions.

Rock eval analysis of organic matter in sediment core 159-959D

The Cretaceous Equatorial Atlantic Gateway between the Central and South Atlantic basins is of interest not only for paleoceanographic and paleoclimatic studies, but also because it provided particularly favourable conditions for the accumulation and preservation of organic-rich sediments. Deposition of carbonaceous sediments along the Côte d'Ivoire-Ghana Transform Margin (Ocean Drilling Program Leg 159) was intimately linked to the plate tectonic and paleoceanographic evolution of this gateway. Notably, the formation of a marginal basement ridge on the southeastern border of the transform margin provided an efficient shelter of the landward Deep Ivorian Basin against erosive and potentially oxidizing currents. Different subsidence histories across the transform margin were responsible for the development of distinct depositional settings on the crest and on both sides of the basement ridge. Whereas the southern, oceanward flank of the basement ridge was characterized by rapid, continuous deepening since last Albian-early Cenomanian, marine sedimentation on the northern, landward flank was interrupted by a period of uplift and erosion in the late Albian, and rapid subsidence started after the early Coniacian. Organic-rich sediments occur throughout almost the entire Cretaceous section, but hydrogen-rich marine black shales were exclusively recovered from core sections above an uplift-related unconformity. These black shales formed when separation of Africa and South America was sufficient to allow permanent oceanic midwater exchange after the late Albian. Four periods of black shale accumulation are recovered, some of them are correlated with the global oceanic anoxic events: in the last Albian-earliest Cenomanian, at the Cenomanian-Turronian boundary, during the middle Coniacian-early Campanian, and in the mid-Maastrichtian. These periods were characterized by increasing carbon flux to the seafloor, induced by enhanced palaeoproductivity and intensified supply of terrestrial organic matter. Black shale depostion appears to be intimately linked to periods of rising or maximum eustatic sea level and to the expansion of the oxygen minimum zone, as indicated by foraminiferal biofacies. Intervals between black shales units, in contrast, indicate a shrinking oxygen minimum zone and enhanced detrital flux rates, probably related to lowering sea level. Upper Cretaceous detritral limestones with high porosities may provide excellent hydrocarbon reservoirs, alsthough their areal extent appears to be limited. Palaeogene porcellanites, capped by Neogene pelagic marls and clays, extend over a wider area and max provide another target for hydrocarbon exploration.

TOC, CaCO3, n-alkane and alkenone concentrations of ODP Sites 202-1237 and 202-1239

We generated preliminary downcore records of total organic carbon content, calcium carbonate, long-chain n-alkane concentration, total alkenone concentration, and alkenone-based sea-surface temperature for samples from the easternmost flank of Nazca Ridge (Site 1237) and the eastern crest of Carnegie Ridge (Site 1239). Total organic carbon and long-chain n-alkane concentrations will be used to evaluate terrestrial sediment sources. Downcore records of alkenone sea-surface temperature will benefit studies of paleoceanography of the southeastern Pacific. Since these sites are located under the influence of major tectonic events, such as the uplift of the Andes Mountains and the closure of the Isthmus of Panama, the records will help us to examine the effects of the tectonic events on the oceanic environment.

Sedimentology and planktonic foraminiferal dissolution during the latest Cretaceous in the South Atlantic

A high-resolution (10-20 kyr) record of variations in CaCO3 content and dissolution was established for latest Cretaceous (last 0.7 Myr) deep-sea sediments from the South Atlantic Ocean (DSDP Site 516 from the Rio Grande Rise, and sites 525 and 527 from the Walvis Ridge). The degree of fragmentation of planktonic foraminifera (DFP) was used as a measure of calcite dissolution. High negative correlations between DFP and other independent measures of carbonate dissolution (percentage of sand fraction, absolute abundance of planktonic foraminifera, and planktonic/benthic foraminiferal ratio) validate its use as a sensitive index of calcite dissolution in upper Maastrichtian deep-sea sediments. Very high DFP and a significant negative correlation between DFP and CaCO 3 content suggest that Site 516 was located below the foraminiferal lysocline during the entire interval studied. Such a shallow position of the lysocline (paleodepth of Site 516 was 1.2 km) may be explained by "upwelling" of corrosive deep waters along the southern margin of the Rio Grande Rise. Sites 525 and 527 were located above the foraminiferal lysocline; however, three short periods of enhanced dissolution were recognised at Site 525 (paleodepth 1 km) and one interval of strong dissolution was identified at Site 527 (paleodepth 2.7 km). The lack of correspondence between the dissolution regimes at sites from the Walvis Ridge suggests limited deep-water communication across this physiographic barrier. Two of the dissolution maxima recognised at Site 525 correspond to carbonate maxima at Site 527. Variations in "upwelling" intensity along the Walvis Ridge, resulting in fluctuations in primary productivity in this area, may be the proximal cause of both carbonate cycles at Site 527 and dissolution cycles at Site 525. We suggest that development of the bottom Ekman layer between a hypothetical westward geostrophic current and the topographical height of the Rio Grande Rise-Walvis Ridge system may be a plausible hydrodynamical explanation for the proposed "'upwelling" along the southern margin of this topographical structure.