Geochemistry and isotopic ratios of basalts from ODP Leg 163 sites

Voluminous, subaerial magmatism resulted in the formation of extensive seaward-dipping reflector sequences (SDRS) along the Paleogene Southeast Greenland rifted margin. Drilling during Leg 163 recovered basalts from the SDRS at 66ºN (Site 988) and 63ºN (Sites 989 and 990). The basalt from Site 988 is light rare-earth-element (REE) enriched (La(n)/Yb(n) = 3.4), with epsilon-Nd(t=60) = 5.3, 87Sr/86Sr = 0.7034, and 206Pb/204Pb = 17.98. It is similar to tholeiites recovered from the Irminger Basin during Leg 49 and to light-REE-enriched tholeiites from Iceland. Drilling at Site 989, the innermost of the sites on the 63ºN transect, was proposed to extend recovery of the earliest part of the SDRS initiated during Leg 152. These basalts are, however, younger than those from Site 917 and are compositionally similar to basalts from the more seaward Sites 990 and 915. Many of the basalts from Sites 989 and 990 show evidence of contamination by continental crust (e.g., epsilon-Nd(t=60) extends down to -3.7, 206Pb/204Pb extends down to 15.1). We suggest that the contaminant is a mixture of Archean granulite and amphibolite and that the most contaminated basalts have assimilated ~5% of crust. Uncontaminated basalts are isotopically similar to basalts from Site 918, on the main body of the SDRS, and are light-REE depleted. Consistent with previous models of the development of this margin, we show that at the time of formation of the basalts from Sites 989 and 990 (1) melting was at relatively shallow levels in a fully-fledged rift zone; (2) fragments of continental crust were present in the lithosphere above the zones of melt generation; and (3) the sublithospheric mantle was dominated by a depleted Icelandic plume component.

Hydrocarbon gas concentrations in sediments from ODP Leg 164 sites

Residual concentrations and distributions of hydrocarbon gases from methane to n-heptane were measured in sediments at seven sites on Ocean Drilling Program (ODP) Leg 164. Three sites were drilled at the Cape Fear Diapir of the Carolina Rise, and one site was drilled on the Blake Ridge Diapir. Methane concentrations at these sites result from microbial generation which is influenced by the amount of pore-water sulfate and possible methane oxidation. Methane hydrate was found at the Blake Ridge Diapir site. The other hydrocarbon gases at these sites are likely the product of early microbial processes. Three sites were drilled on a transect of holes across the crest of the Blake Ridge. The base of the zone of gas-hydrate occurrence was penetrated at all three sites. Trends in hydrocarbon gas distributions suggest that methane is microbial in origin and that the hydrocarbon gas mixture is affected by diagenesis, outgassing, and, near the surface, by microbial oxidation. Methane hydrate was recovered at two of these three sites, although gas hydrate is likely present at all three sites. The method used here for determining amounts of residual hydrocarbon gases has its limitations and provides poor assessment of gas distributions, particularly in the stratigraphic interval below about ~100 mbsf. One advantage of the method, however, is that it yields sufficient quantities of gas for other studies such as isotopic determinations.

Magnetic susceptibility parameters of ODP Leg 204 sites

In this paper, we present a rock magnetic data set produced for sediments from Hydrate Ridge recovered during Ocean Drilling Program Leg 204. Our data set is based on several artificially induced magnetic properties that can be used as a diagnostic for the presence of magnetic iron sulfides. The occurrence of magnetic iron sulfides within the gas hydrate stability zone in locations where gas hydrates are present seems to confirm previous interpretations linking formation of such minerals with generation of gas hydrate. Magnetic iron sulfides are also found at positions deeper than the gas hydrate stability zone. We suggest that these positions, which include intervals located just below the bottom-simulating reflector and also at deeper positions, may mark the former presence of gas hydrates that have been later dissociated as the gas hydrate stability zone moved upward through time. Detailed characterization of the magnetic iron sulfide mineralogy and comparison with sedimentological and geochemical data will be attempted for better determining the significance of magnetic iron sulfides in Hydrate Ridge sediments and their possible applications in the study of gas hydrates.

Geochemical data for drilled powder samples from two fossil Porites corals from Integrated Ocean Drilling Program Expedition 310

Fossil corals are unique archives of past seasonal climate variability, providing vital information about seasonal climate phenomena such as ENSO and monsoons. However, submarine diagenetic processes can potentially obscure the original climate signals and lead to false interpretations. Here we demonstrate the potential of laser ablation ICP-MS to rapidly detect secondary aragonite precipitates in fossil Porites colonies recovered by Integrated Ocean Drilling Program (IODP) Expedition 310 from submerged deglacial reefs off Tahiti. High resolution (100 µm) measurements of coralline B/Ca, Mg/Ca, S/Ca, and U/Ca ratios are used to distinguish areas of pristine skeleton from those afflicted with secondary aragonite. Measurements of coralline Sr/Ca, U/Ca and oxygen isotope ratios, from areas identified as pristine, reveal that the seasonal range of sea surface temperature in the tropical south Pacific during the last deglaciation (14.7 and 11 ka) was similar to that of today.

Age estimations of calcareous nannofossil biohorizons of the middle Paleocene to early Eocene at ODP Site 208-1262 (Table 1, Appendix B)

Over the last several decades debates on the 'tempo and mode' of evolution have centered on the question whether morphological evolution preferentially occurs gradually or punctuated, i.e., with long periods of stasis alternating with short periods of rapid morphological change and generation of new species. Another major debate is focused on the question whether long-term evolution is driven by, or at least strongly influenced by changes in the environment, or by interaction with other life forms. Microfossils offer a unique opportunity to obtain the large datasets as well as the precision in dating of subsequent samples to study both these questions.We present high-resolution analyses of selected calcareous nannofossils from the deep-sea section recovered at ODP Site 1262 (Leg 208) in the South-eastern Atlantic. The studied section encompasses nannofossil Zones NP4-NP12 (equivalent to CP3-CP10) and Chrons C27r-C24n. We document more than 70 biohorizons occurring over an about 10 Myr time interval, (~62.5 Ma to ~52.5 Ma), and discuss their reliability and reproducibility with respect to previous data, thus providing an improved biostratigraphic framework, which we relate to magnetostratigraphic information, and present for two possible options of a new Paleocene stratigraphic framework based on cyclostratigraphy. This new framework enabled us to tentatively reconstruct steps in the evolution of early Paleogene calcareous nannoplankton through documentation of transitional morphotypes between genera and/or species and of the phylogenetic relations between the genera Fasciculithus, Heliolithus, Discoasteroides and Discoaster, as well as between Rhomboaster and Tribrachiatus. The exceptional record provided by the continuous, composite sequence recovered at Walvis Ridge allows us to describe the mode of evolution among calcareous nannoplankton: new genera and/or new species usually originated through branching of lineages via gradual, but relatively rapid, morphological transitions, as documented by the presence of intermediate forms between the end-member ancestral and descendant forms. Significant modifications in the calcareous nannofossil assemblages are often "related" to significant changes in environmental conditions, but the appearance of structural innovations and radiations within a single genus also occurred during "stable" environmental conditions. These lines of evidence suggest that nannoplankton evolution is not always directly triggered by stressed environmental conditions but could be also driven by endogenous biotic control.

Core scan image analysis corrected for cracks, ODP Hole 154-926C

Drill cores are essential for the study of deep-sea sediments and on-land sites because often no suitable outcrop is available or accessible. These cores form the backbone of stratigraphical studies using and combining various dating techniques. Cyclostratigraphy is usually based on fast and inexpensive measurements of physical sediment properties. One indirect but highly valuable proxy for reconstructing the sediment composition and variability is sediment color. However, cracks and other disturbances in sediment cores may dramatically influence the quality of color data retrieved either directly from photospectrometry or derived from core image analysis. Here we present simple but powerful algorithms to extract color data from core images, and focus on routines to exclude cracks from these images. Results are discussed using the example of an ODP core from the Ceara Rise in the Central Atlantic. The crack correction approach presented highly improves the quality of color data and allows the easy incorporation of cracked cores into studies based on core images. This facilitates the quick and inexpensive generation of large color datasets directly from quantified core images, for cyclostratigraphy and other purposes.

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Wyoming Highway Patrol, Commercial Carrier Section, Cheyenne

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Transportation Department, Office of University Research, Washington, D.C.

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Transportation Department, Office of the Assistant Secretary for Systems Development and Technology, Washington, D.C.

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National Highway Traffic Safety Administration, Washington, D.C.