Geochemical investigation of ODP Leg 113 sites

Dissolved organic carbon (DOC) was determined in pore water extracted from pelagic and hemipelagic sediments recovered during Leg 113. DOC concentration varied between 1.82 and 13.6 mg C/L which is one to two orders of magnitude less than previously reported for hemipelagic sediments. It is argued that this difference is related to differences in the intensity of degradation of organic matter. As a first approximation it is found that in reducing sediments, the level of DOC is proportional to the intensity of sulfate reduction. It is suggested that DOC is formed by different mechanisms in oxic and reducing environments.

Characteristic directions and polarity ratings and polarity chron assignments of ODP Leg 171B sites

The full suite of magnetic polarity chrons from Subchron M''-2r'' (early Albian) through Chron C13r (latest Eocene) were resolved at one or more Ocean Drilling Program sites on the Blake Nose salient of the Florida continental margin. These sediments preserve diverse assemblages of calcareous and siliceous microfossils; therefore, the composite suite provides a reference section for high-resolution correlation of biostratigraphic datums to magnetic polarity chrons of the Late Cretaceous and Paleogene. Relative condensation or absence of polarity zones at different sites along the transect enhance the recognition and dating of depositional sequences and unconformities within the margin succession. A stable paleolatitude of ~25°N was maintained from the late Aptian through Eocene.

Chemical and isotope compositions of bottom sediments from ODP Leg 168, Eastern Flank of the Juan de Fuca Ridge

Ten sites were drilled in the eastern flank of the Juan de Fuca Ridge (North East Pacific) along a 100 km-long east-west transect during Leg ODP 168. This study focuses on the mineralogical and chemical study of sediments that overly basaltic basement through which seawater circulates. Silicate authigenesis was observed in the sediment layer just above basement at sites located more than 30 km from the ridge axis. This sediment alteration is particularly abundant at ODP Sites 1031 and 1029 where authigenic formation of Fe-Mg rich smectite and zeolite and the dissolution of biogenic calcite are observed. Comparison of the distribution of the alteration in the basal sediment collected along this transect suggests that diffusional transport of aqueous solutes from the basement into the overlying sediment cannot produce the mineralogical and chemical changes in the basal sediments at Sites 1031 located on a basement topographic high, and at Site 1029 located at about 50 km from the ridge axis on a buried basement area. Vertical advection of basement fluid though the sediment section is required to produce this alteration. These processes are still active at Site 1031, based on systematic variations in pore-water profiles and temperatures obtained from stable isotopic data on calcium carbonates and the nature of authigenic minerals. At Site 1029, there is no present-day advection of basement fluids though the sediment section, suggesting that this is a relic site for fluid flow.

Investigations of Cretaceous and Tertiary kerogens in sediments of ODP Leg 113 holes

Seventy-one samples from nine sites were analyzed for total organic carbon (TOC). Fifty-six samples, containing 0.2% or more TOC, were evaluated by Rock-Eval to assess the nature of their kerogen and its petroleum source potential. Visual kerogen studies were carried out. Petroleum potential was encountered only in Valanginian calcareous claystones at Hole 692B close to the margin of Dronning Maud Land. A section of 44.7 m was penetrated. The unit possesses a revised mean TOC of 9.8% and petroleum potential of 43.2 kg/Mg, relatively high values in comparison to other Cretaceous anoxic oceanic sections and the totality of petroleum source rocks. At Sites 689 and 690, extremely low TOC levels, mean 0.07%, preclude kerogen analysis. Kerogens in Eocene to Pliocene sediments of the central and western Weddell Sea (Sites 694, 695, 696, and 697) are similar everywhere, largely comprising brown to black, granular, amorphous material of high rank, and generally possessing several reflectance populations of vitrinite particles. The latter are interpreted as indicative of the recycling of sediments of a variety of levels of thermal maturity.

Maxima of interstitial water and gas parameters in ODP Leg 182 sediments

During the drilling of the southern Australian continental margin (Leg 182 of the Ocean Drilling Program), fluids with unusually high salinities (to 106?) were encountered in Miocene to Pleistocene sediments. At three sites (1127, 1129, and 1131), high contents of H2S (to 15%), CH4 (50%), and CO2 (70%) were also encountered. These levels of H2S are the highest yet reported during the history of either the Deep Sea Drilling Project or the Ocean Drilling Program. The high concentrations of H2S and CH4 are associated with anomalous Na+/Cl- ratios in the pore waters. Although hydrates were not recovered, and despite the shallow water depth of these sites (200-400 m) and relative warm bottom water temperatures (11-14°C), we believe that these sites possess disseminated H2S-dominated hydrates. This contention is supported by calculations using the measured gas concentrations and temperatures of the cores, and depths of recovery. High concentrations of H2S necessary for the formation of hydrates under these conditions were provided by the abundant (SO4)2- caused by the high salinities of the pore fluids, and the high concentrations of organic material. One hypothesis for the origin of these fluids is that they were formed on the adjacent continental shelf during previous lowstands of sea level and were forced into the sediments under the influence of hydrostatic head.

Carbonate and bulk grain-size record for ODP Leg 130 holes

A major goal of Ocean Drilling Program (ODP) Leg 130 was to drill four sites down the northeastern flank of the Ontong Java Plateau to collect a series of continuous sedimentary sequences that would provide a depth transect of Neogene sediments. In particular, the study of the sediments recovered along the depth transect is expected to yield high-resolution stratigraphic, geochemical, and physical properties records across intervals of major paleoceanographic changes by evaluating variations of primary sedimentological and paleoceanographic indicators (e.g., carbonates, isotopes, grain size, microfossil assemblages, etc.). This data report presents the results of highresolution (3-5 Ka sample intervals) analyses of carbonate concentration and bulk sediment grain size at Sites 803-806 for the time interval from 2 Ma to the present.

Bulk calcite minor element composition of ODP Leg 130 samples

We investigated minor element ratios (Sr/Ca and Mg/Ca) in bulk sediment samples from Sites 803-807 using a recently optimized sample treatment protocol for calcium-carbonate-rich sediments consisting of sequential reductive and ion exchange treatments. We evaluated this protocol relative to bulk sediment leaching using samples from Sites 804 and 806, the two end-member sites in the depth transect, reporting as well Mn/Ca and Fe/Ca ratios for sediments from these two sites processed by means of both methods. The Sr/Ca ratios were only slightly affected by the sample treatment, with an average reduction of 6%-7% caused primarily by the ion exchange step. The reductive sample treatment, designed to be effective at removing Mn-rich oxyhydroxides, has a major effect on Mg/Ca ratios, with up to 50% reduction, whereas little effect occurred in ion exchange alone on Mg/Ca ratios. The Mn/Ca and Fe/Ca ratios were not consistently offset by the sample treatment, and these ratios do not appear to be representative of calcite geochemistry reflecting either ocean history or diagenetic overprinting. Celestite solubility appears to be an important control on interstitial water Sr concentrations in these sites, and it must be considered when constructing Sr mass balance models of calcite recrystallization. Calcite Sr/Ca ratios (range 1-2 mmol/mol) are similar from site to site when plotted vs. age, with a pattern comparable to that for well-preserved foraminifer tests over the past 40 Ma. Interstitial water Mg and Ca gradients appear to reflect basement character and the intensity of alteration; they can vary substantially over a small area. Calcite Mg/Ca ratios (range 1.5-4.5 mmol/mol) differ from site to site, with generally higher ratios for sites at a shallower water depth. Increasing calcite Mg/Ca ratios correlate with decreasing Sr/Ca ratios in the treated samples. No consistent pattern exists for calcite Mg/Ca ratios vs. age or depth, nor is any direct correlation to interstitial water Mg/Ca ratios present.

Geochemistry of ODP Leg 129 igneous rocks

This report presents all the available major and trace elemental analyses and Sr, Nd, and Pb isotopic compositions of basaltic rocks recovered from Ocean Drilling Program Sites 800, 801, and 802 during Leg 129 (Table 1). Its main purpose is to provide other investigators a complete summary of geochemical data for Leg 129 basement basalts that they can use for later work. Detailed discussions of the data are presented elsewhere in the volume by Floyd and Castillo (Site 801 geochemistry and petrogenesis, dataset: doi:10.1594/PANGAEA.779154) Floyd et al. (Sites 800 and 802 geochemistry and petrography, dataset: doi:10.1594/PANGAEA.779129), Alt et al. (Site 801 alteration, dataset: doi:10.1594/PANGAEA.779207), and Castillo et al. (Sr, Nd, and Pb isotope geochemistry of Leg 129 basalts, dataset: doi:10.1594/PANGAEA.779191).

Distribution and abundance of calcareous-nannoplankton species in the Cretaceous sediments of DSDP Leg 62 Holes

Cretaceous sediments were recovered at all four sites (Sites 463-466) of the central North Pacific drilled during Leg 62 of the Deep Sea Drilling Project. One of the objectives was to get more information about the development of ocean plankton communities and early evolution of planktonic groups of the Mesozoic. In this article, the Cretaceous calcareous nannofossils from two areas of the central North Pacific (Mid-Pacific Mountains and Hess Rise) are listed and discussed. (The Cenozoic calcareous nannofossils are discussed by R. Schmidt 1981). Coring was continuous at all sites. Mesozoic calcareous nannoplankton assemblages range on the Mid-pacific Mountains from Barremian to Early Maastrichtian, and on Hess Rise from Albian to Late Maastrichtian. (No calcareous nannofossils older than Barremian or Albian respectively were found).

Grain size analyses of ODP Leg 178 sites

Sites 1095, 1096, and 1101 were drilled on the continental rise west of the Antarctic Peninsula (Fig. F1) to recover a continuous high-resolution record of Antarctic glaciation. Site 1095 is the subject of a short paper in this volume (Pudsey, 2001, doi:10.2973/odp.proc.sr.178.214.2001), whereas mass accumulation rates at the three sites are described by Wolf-Welling (2001, doi:10.2973/odp.proc.sr.178.223.2001) and ice-rafted debris at Site 1101 is discussed by Cowan (2001, doi:10.2973/odp.proc.sr.178.206.2001) This report documents grain-size data (sand and fine fraction) and the proportion of biogenic silica for the upper 300 m at Site 1095, the upper 250 m at Site 1096, and the whole 220 m at Site 1101.

Geochemistry at DSDP Leg 62 Holes

A total of 191 samples was collected for inorganic geochemical analyses from DSDP Holes 463, 464, 465, 465A, and 466. These samples were collected with two main goals. First, at least one sample was collected from each core, whenever possible, to document the general geochemical variability within lithologic units. Unfortunately, several lithologic units were inadequately sampled because of poor recovery, mostly due to the presence of chert. The least-sampled units are Units III in Hole 464 and Units IB and II in Hole 466. The second goal was to look for geochemical differences between contrasting lithologies within main lithologic units, particularly between cyclic interbeds of red and green limestone in Lithologic Unit II, Hole 463, and between olive, laminated limestone and gray, massive limestone in Lithologic Unit II, Hole 465A.

Distribution of quaternary siliceous sponge spicules in sediments of ODP Leg 180 sites

Siliceous sponge spicules were found in Quaternary sediments recovered during drilling of Leg 180. The assemblage consists mainly of monaxon forms. Relative abundances of the various types are tabulated.

Miozene larger foraminifera in ODP Leg 133 holes

The Marion Plateau is a large carbonate platform off northeastern Queensland. Three sites (815, 816, and 826) were drilled on this platform and form the basis for this study. Larger benthic foraminifers, together with rare planktonic forms from the shallow-water carbonates that form the main part of the platform sequence, were studied to establish a biostratigraphy. The presence of Lepidocyclina (Nephrolepidiná) howchini sensu lato and Ladoronia vermicularis, together with Globorotalia (Globorotalia) praemenardii and Orbulina, indicate an early middle Miocene (N9-N12) age (i.e., lower Tf stage) for these carbonates. Dolomitization has destroyed much of the original fabric of these carbonates, making study of the larger foraminifers difficult. Sites 815 (forereef location) and 826 (backreef, lagoonal setting) provide the best faunas. However, at all sites nodular coralline algae and Halimeda are the major bioclasts; coral fragments form a major component at Sites 816 and 826. The middle Miocene neritic sequence is separated from the overlying hemipelagic sequence by an unconformity that spans much of the middle and late Miocene. At Site 815, which is in a forereef situation, the overlying hemipelagic sequence contains a Zone N17A fauna, but at Site 816, higher on the platform, a similar sequence contains a Zone N19 fauna. The faunas indicate that the platform was built up during the early middle Miocene and remained at fairly constant water depths and temperatures during this period. It was then exposed prior to subsiding rapidly during the late Miocene and Pliocene to depths similar to those of the present day.

Planktonic foraminifera abundance in sediments of ODP Leg 170 sites

From October to December in 1996, Sites 1039 through 1043 were drilled on the lower continental slope and the bottom of the Middle American Trench. Planktonic foraminifers were obtained from 377 samples of the total 487 examined. The Pliocene- to Pleistocene-age sediments of Sites 1039 and 1043 are continuous from Zones N19 through N23. At Sites 1039 and 1040, middle Miocene sediments are also continuous, encompassing Zones N8 through N12. The sequences of the upper part of Sites 1040, 1041, 1042, and 1043 are décollements, tentatively assignable to Zone N19 for Sites 1040, 1041, and 1042 and to Zone N22 for Site 1043. The oldest sediments of these sites are assigned to Zone N7 (latest early Miocene), ~17 Ma in age.