Deep Sea Drilling Research Articles

Physical properties of sediments from the Ulleung Basin, East Sea: Results from Second Ulleung Basin Gas Hydrate Drilling Expedition, East Sea (Korea)

Physical properties, including basic index properties, undrained shear strength, and thermal conductivities were measured on conventional cores retrieved from the Ulleung Basin, during the second Ulleung Basin Gas Hydrate expedition (UBGH2). The UBGH2 logged 13 sites and cored 10 sites to locate potential sites for an offshore test production. A total of 211 conventional cores were recovered. Undrained shear strength, thermal conductivity, and index properties, including porosity and grain density, were measured onboard. Mineral composition analyses and grain size analyses were completed onshore after the expedition.The averaged porosity at each site ranges from 65% to 71%, the averaged grain density at each site ranges from 2.57 to 2.66 g/cm3, and the mean grain size mostly lies between 4 μm and 25 μm, with sparsely scattered coarse grained intervals. The relatively high porosity and low grain density are due to the large portion of diatomaceous sediments. The thermal conductivities average around 0.8 W/mK, and the low porosity and the abundance of clay mineral and OAPL-A may have caused the relatively low thermal conductivity in the Ulleung Basin.The geomechanical analyses revealed a few relevant findings important for sediment physical behaviors during gas hydrate production. The particle migration in coarse grained layers during production necessitates proper measure for sand productions while fine grained layers are mostly self-filtering. The vertical deformation estimated from the compression index suggested that the subsidence induced by the pore pressure change from the depressurization is much higher than those induced by the lost of gas hydrate particles from dissociation. Massive vertical deformation in fine-grained layers has been predicted to occur due to the pore pressure change from depressurization induced gas hydrate production. The drilling mud weight induced pressure window is mostly determined by the water depth in deep sea drilling, but caution should be taken in determination of fracture pressures in hydrate-bearing sediments, because gas hydrate saturations alter Poisson's ratio.

Pollen-corrected leaf wax D/H reconstructions of northeast African hydrological changes during the late Miocene

Plant leaf wax hydrogen isotope (δDwax) reconstructions are increasingly being used to reconstruct hydrological change. This approach is based upon the assumption that variations in hydroclimatic variables, and in particular, the isotopic composition of precipitation (δDP), dominate δDwax. However modern calibration studies suggest that offsets between plant types may bias the δDwax hydrological proxy at times of vegetation change. In this study, I pair leaf wax analyses with published pollen data to quantify this effect and construct the first vegetation-corrected hydrogen isotopic evidence for precipitation (δDcorrP). In marine sediments from Deep Sea Drilling Program Site 231 in the Gulf of Aden spanning 11.4–3.8Ma (late Miocene and earliest Pliocene), I find 77‰ swings in δDwax that correspond to pollen evidence for substantial vegetation change. Similarities between δDP and δDcorrP imply that the hydrological tracer is qualitatively robust to vegetation change. However, computed vegetation corrections can be as large as 31‰ indicating substantial quantitative uncertainty in the raw hydrological proxy. The resulting δDcorrP values quantify hydrological change and allow us to identify times considerably wetter than modern at 11.09, 7.26, 5.71 and 3.89Ma. More generally, this novel interpretative framework builds the foundations of improved quantitative paleohydrological reconstructions with the δDwax proxy, in contexts where vegetation change may bias the plant-based proxy. The vegetation corrected paleoprecipitation reconstruction δDcorrP, represents the best available estimate as proof-of-concept, for an approach that I hope will be refined and more broadly applied.

The first microbiological contamination assessment by deep-sea drilling and coring by the D/V Chikyu at the Iheya North hydrothermal field in the Mid-Okinawa Trough (IODP Expedition 331)

During the Integrated Ocean Drilling Program (IODP) Expedition 331 at the Iheya North hydrothermal system in the Mid-Okinawa Trough by the D/V Chikyu, we conducted microbiological contamination tests of the drilling and coring operations. The contamination from the drilling mud fluids was assessed using both perfluorocarbon tracers (PFT) and fluorescent microsphere beads. PFT infiltration was detected from the periphery of almost all whole round cores (WRCs). By contrast, fluorescent microspheres were not detected in hydrothermally active core samples, possibly due to thermal decomposition of the microspheres under high-temperature conditions. Microbial contamination from drilling mud fluids to the core interior subsamples was further characterized by molecular-based evaluation. The microbial 16S rRNA gene phylotype compositions in the drilling mud fluids were mainly composed of sequences of Beta- and Gammaproteobacteria, and Bacteroidetes and not archaeal sequences. The phylotypes that displayed more than 97% similarity to the sequences obtained from the drilling mud fluids were defined as possible contaminants in this study and were detected as minor components of the bacterial phylotype compositions in 13 of 37 core samples. The degree of microbiological contamination was consistent with that determined by the PFT and/or microsphere assessments. This study suggests a constructive approach for evaluation and eliminating microbial contamination during riser-less drilling and coring operations by the D/V Chikyu.

New perspective of Miocene marine hydrocarbon source rocks in deep-water area in Qiongdongnan Basin of northern South China Sea

Drilling wells reveal that the organic matter abundance of Miocene marine source rocks in shallow water area of the Qiongdongnan Basin is relatively low with poor hydrocarbon generation potential. However, in some drilling wells of deep water area close to the central depression belt, Miocene marine source rocks with better organic matter abundance and hydrocarbon generation have been found, which have achieved better source rock standard based on the analysis of geochemical characteristics. Although there are no exploratory wells in deep water area of the research region, through the comparative analysis of geochemical data of several typical exploratory wells respectively from shallow water area in the basin, central depression belt margin in deep-water area of the basin and Site 1148 of deep sea drilling in the South China Sea Basin, it reveals that the tendency of the quality of source rocks becomes positive gradually from delta to bathyal environment, which then becomes negative as in deep oceanic environment. Owing to the lack of terrestrial organic matter input, the important controlling factors of Miocene marine source rocks in the Qiongdongnan Basin are ocean productivity and preservation conditions of organic matter. The element geochemistry data indicate that the tendency of the paleoproductivity and the preservation conditions of organic matter become positive as water depth increase from shallow area to bathyal area close to central depression belt. So it is speculated that there must exist high quality source rocks in the central depression area where the preservation conditions of organic matter are much better. Besides, in theory, in oxygen-poor zone of oceanic environment at the water depth 400–1 000 m, the preservation conditions of organic matter are well thus forming high-quality marine source rocks. The resulting speculation, it is reasonable to consider that there are high hydrocarbon generation potential source rocks in bathyal environment of the Qiongdongnan Basin, especially at the water depth 400–1 000 m.

Quaternary seismic facies of the atlantic continental rise

High-resolution seismic profiles collected by Parasound and SES-2000 deep profilers during Cruise 26 of the R/V Akademik Sergei Vavilov (2009) along the continental slope base of South America, NW Africa, and West Europe are correlated with the deep-sea drilling boreholes. Lithofacies interpretation of the Quaternary deep-water seismic facies of hemipelagites, bottom current deposits (contourites), and gravitites (turbidites, mud flow deposits) is presented. The data obtained reveal the domination of contourites in the accumulation of continental rise apron under conditions of relatively scarce terrigenous material supply. It is shown that acoustically stratified seismic facies under these conditions commonly reflect interbedding of the terrigenous clay and biogenic calcareous ooze related to the Pleistocene glacial/interglacial cycles.

Source rock characteristics and compositional kinetic models of Cretaceous organic rich black shales offshore southwestern Africa

The source rock potential of Cretaceous organic rich whole rock samples from deep sea drilling project (DSDP) wells offshore southwestern Africa was investigated using bulk and quantitative pyrolysis techniques. The sample material was taken from organic rich intervals of Aptian, Albian and Turonian aged core samples from DSDP site 364 offshore Angola, DSDP well 530A north of the Walvis Ridge offshore Namibia, and DSDP well 361 offshore South Africa. The analytical program included TOC, Rock-Eval, pyrolysis GC, bulk kinetics and micro-scale sealed vessel pyrolysis (MSSV) experiments. The results were used to determine differences in the source rock petroleum type organofacies, petroleum composition, gas/oil ratio (GOR) and pressure–volume–temperature (PVT) behavior of hydrocarbons generated from these black shales for petroleum system modeling purposes.The investigated Aptian and Albian organic rich shales proved to contain excellent quality marine kerogens. The highest source rock potential was identified in sapropelic shales in DSDP well 364, containing very homogeneous Type II and organic sulfur rich Type IIS kerogen. They generate P–N–A low wax oils and low GOR sulfur rich oils, whereas Type III kerogen rich silty sandstones of DSDP well 361 show a potential for gas/condensate generation. Bulk kinetic experiments on these samples indicate that the organic sulfur contents influence kerogen transformation rates, Type IIS kerogen being the least stable. South of the Walvis Ridge, the Turonian contains predominantly a Type III kerogen. North of the Walvis Ridge, the Turonian black shales contain Type II kerogen and have the potential to generate P–N–A low and high wax oils, the latter with a high GOR at high maturity.Our results provide the first compositional kinetic description of Cretaceous organic rich black shales, and demonstrate the excellent source rock potential, especially of the Aptian-aged source rock, that has been recognized in a number of the South Atlantic offshore basins.

Development of a Continuous Directional Coring System for Deep-Sea Drilling

Summary Core sampling is one of most important methods for gaining knowledge on formation properties below the seafloor or for extracting such potential new energy resources as methane hydrates. The riser-equipped deep-sea drilling vessel Chikyu carries out scientific expeditions for such underwater formation core drilling to analyze the origin of hydrate generation near the coast of Japan. Among the various systems available, continuous coring using wireline is the most promising for obtaining a steady supply of core samples. Although measuring-while-drilling/logging-while-drilling (MWD/ LWD) methods are deployed, an advanced directional control system specifically for deep-sea coring is currently under technical development. Core barrels consisting of the inner and outer barrels have been designed with an inner barrel that is retrievable and resettable. The new method combines an adjustable bent-housing sub that is located between the outer barrel and just above the inner core tube. Laboratory tests in which the inner barrel is passed through the bent housing section have been performed, with results showing bent housing angles of 0.25-2.0°. Land drilling tests with the bent housing were also performed in order to ensure drilling efficiency and core recovery. This paper presents the progress of our newly developed coring system with an integrated analysis of directional-drilling and coring capabilities.

Changing spectrum of geomagnetic intensity variations in a fragmented 12 My sediment record from the Oligocene

Time series of relative geomagnetic paleointensity variations derived from marine sediments can be calibrated using absolute data derived from igneous materials. The resulting records may be suitable for spectral analysis of geomagnetic dipole variations. This work re-evaluates the 12 My (22.74–34.77 Ma) sediment record from Deep Sea Drilling Project Leg 73, Site 522, that is a key data set for determining the paleomagnetic power spectrum in the frequency range 1–100 My −1. The 12 My record is marred by uneven sampling, with the interval between samples ranging from 1 to 640 ky, and contains several gaps that are considered too long to interpolate. The relative intensity data are calibrated using 129 globally distributed absolute paleointensity data from the same time interval. The power spectrum of the resulting time series is estimated using direct multi-taper spectral estimation with prolate data tapers adapted to deal with missing sections in the time series. The longest record available for analysis is thereby extended from 5.3 to 12 My. The new paleomagnetic power spectrum confirms the presence of a broad spectral peak at around 8 My −1 for the early Oligocene and uncovers a peak around 2.5 My −1 in the late Oligocene. Both peaks may be linked to tiny wiggles in marine magnetic anomalies. The new analysis unambiguously verifies that there is lower overall power in the younger part of the record, where the reversal process appears to dominate the power spectrum of the paleosecular variation. A comparison of the late Oligocene spectrum with that of PADM2M, a model of paleomagnetic axial dipole variations for 0–2 Ma, reveals some broad similarities; both time periods have similar power levels and a reversal rate of 4 My −1. During the early Oligocene the reversal rate is about a factor of two lower, the field strength is higher, and the secular variation is stronger, suggesting that a strong magnetic field inhibits reversals but produces more variability in field strength.

The Debatabase book: a must-have guide for successful debate

this book provides background, arguments and resources on over 130 debate topics in areas as diverse as business, science and technology, environment, politics, religion, culture and education. All topics have been updated and new topics added for this edition. Among the new topics are: Arizona's Immigration Law Bribery, Ever Acceptable? Prosecution of Child Soldiers Increase US use of Coal Criminalizing Blasphemy Deep-sea Drilling Drones, use of in Warfare Electing Judges Genetic Privacy/Ethics in Medical Research Instant Replay in Sports Internet force for Democracy Merry Christmas or Happy Holidays Proposition 14 (Non-partisan State Primaries) Religious Garb/Symbols in Public Places, Right to know parentage Soft Drink/Junk Food Tax (Fatty Food Tax) Statute of Limitation, Abolition of Twentieth-eighth Amendment, Proposed

Open up monitoring of deep-sea drilling

Open up monitoring of deep-sea drilling

Around the World

In science news around the world this week, officials with Tokyo Electric Power Co. say it could take up to 9 months to end the threat of radioactive releases from the stricken reactors at Fukushima Daiichi, researchers have released new criteria for diagnosing Alzheimer's disease, some 30 ring-tailed lemurs are headed to a private island, deep-sea drilling is 50 years old, a promising HIV strategy has fallen short in trials in Africa, a Canadian safe-injection facility has been found to cut the death rate from overdoses, and the 2011 U.S. federal budget will create a key satellite data gap in 2017.

Loss of trace elements from serpentinites during fluid-assisted transformation of chrysotile to antigorite — An example from Guatemala

Abstract We studied a unique chrysotile–antigorite serpentinite, drilled on Deep Sea Drilling Project Leg 84 (Site 566) in the Guatemala forearc. Our in situ major and trace element data provide new constraints on possible reactions and associated trace element mobilisation during shallow serpentinite subduction. Chrysotile of the studied serpentinite, formed by the hydration of an upper mantle peridotite precursor, is partially replaced by antigorite (alone) which also occurs in 0.5 mm wide unoriented veins crosscutting the rock. Based on textural relationships and the P–T–X stability of the rock forming phases, the replacement of chrysotile by antigorite occurred at T The fluid-assisted chrysotile-to-antigorite transformation and associated trace element loss documented here can occur in the shallow (

Calcareous nannofossil changes during the Mid-Pleistocene Revolution: Paleoecologic and paleoceanographic evidence from North Atlantic Site 980/981

New quantitative data on calcareous nannofossil assemblages through 583–1138 thousand years ago (kyr) have been acquired in high sample resolution (2–3ky) at northern Atlantic ODP (Ocean Drilling Program) Site 980/981. Assemblage composition reflects a temperate paleobioprovince suggesting significant influx of warm North Atlantic Current at the site location during the mid-Pleistocene transition, between Marine Isotope Stage (MIS) 35 and 15.Three intervals have been described based on changes in nannofossil composition and abundance fluctuations of taxa. Reticulofenestrids are abundant just in the first interval (MIS 35–22), which is also characterised by the absence of Gephyrocapsa (>4μm) and C. pelagicus s.l., the latter occurring in upper MIS 24 only. The second interval corresponds to the expanded warm MIS 21 that is accompanied by high carbonate content, absence of both nannofossil reworking and ice rafted debris (IRD), higher abundance of C. leptoporus (5–8μm) and H. carteri, and absence of C. pelagicus s.l. and medium gephyrocapsids. The third interval (MIS 20–15) records the occurrence of C. pelagicus s.l. and medium Gephyrocapsa, generally higher abundance and higher amplitude fluctuations of helicoliths, and absence of reticulofenestrids. The major changes in nannofossil assemblages seem to be the result of combined paleoenvironmental factors related to sea surface water features (temperature and nutrient availability, sea-ice cover) and possibly to deep and intermediate water production of both Northern and Southern Hemisphere origin during glacial and interglacial phases. Complex inter-relationships between environmental parameters and evolutionary/ecological factors are inferred to explain the patterns of Coccolithus pelagicus subspecies, whose distribution and abundance fluctuations are compared with the available patterns of Turborotalia quinqueloba and Neogloboquadrina pachyderma (left coiled) at Site 980 and with the C. pelagicus subspecies patterns from North Atlantic DSDP (Deep Sea Drilling Project) Site 607 and South Atlantic ODP Site 1090.Data collected provide additional information on stratigraphic distribution of selected taxa; the First Occurrence (FO) of Gephyrocapsa omega is confirmed as a diachronous event, even in the Atlantic Ocean, while the First and Last Common Occurrence (FCO, LCO) of R. asanoi appear as diachronous and synchronous events, respectively, on a global scale.

Discovery prospects for a supernova signature of biogenic origin

Approximately 2.8 Myr before the present our planet was subjected to the debris of a supernova explosion. The terrestrial proxy for this event was the discovery of live atoms of 60Fe in a deep-sea ferromanganese crust. The signature for this supernova event should also reside in magnetite (Fe 3O 4) microfossils produced by magnetotactic bacteria extant at the time of the Earth-supernova interaction, provided the bacteria preferentially uptake iron from fine-grained iron oxides and ferric hydroxides. Using estimates for the terrestrial supernova 60Fe flux, combined with our empirically derived microfossil concentrations in a deep-sea drill core, we deduce a conservative estimate of the 60Fe fraction as 60Fe/Fe ≈ 3.6 × 10 −15. This value sits comfortably within the sensitivity limit of present accelerator mass spectrometry capabilities. The implication is that a biogenic signature of this cosmic event is detectable in the Earth’s fossil record.

TRANSFORMING DEEP-SEA DRILLING

A CORNERSTONE of U.S. energy policy—domestic offshore oil and natural gas drilling and production—is likely to be transformed with enactment of recommendations of the presidentially appointed National Commission on the BP Deepwater Horizon Oil Spill & Offshore Drilling. Gone would be a system in which a small, underfunded, and poorly trained agency does double time—collecting industry-paid royalties while attempting to oversee industrial safety. In its place would be a new independent safety-only agency that uses risk-based regulations and more and better-trained inspectors to review and implement industry-developed, site-specific drilling management plans. Since last May, the seven-member oversight panel has held hearings, interviewed witnesses and experts, and traveled the Gulf of Mexico as it studied the April 20, 2010, BP oil rig accident that killed 11 workers and resulted in the worst offshore oil spill in history. The panel’s review grew to include industry operations and government regulation of o...

Chapter 46 Scientific deep-sea drilling in high northern latitudes

Abstract Some 30 years ago the regional aspects of the plate tectonic history of the Norwegian–Greenland Sea and the eastern Arctic Ocean were unravelled and showed that these ocean basins had opened in early Eocene, 55–56 Ma ago. Drilling by Glomar Challenger in the Norwegian–Greenland Sea during Leg 38 of the Deep Sea Drilling Project confirmed the plate tectonic model and established a marine biostratigraphy framework for the region. The leg set the stage for three subsequent Ocean Drilling Program legs of thematically oriented drilling by the Joides Resolution . Leg 104 drilled a deep acoustic basement hole on the Vøring Plateau, which has become a legacy hole for volcanic margin studies, and provided new key information on the Northern Hemisphere Glaciation and the history of the Norwegian Current. Legs 151 and 162 addressed North Atlantic–Arctic gateways problems. During Leg 151 the Joides Resolution succeeded, with icebreaker support, in reaching the ice-free waters north of Svalbard, thus for the first time bringing a scientific drill ship into the Arctic Ocean. In 2004, the Integrated Ocean Drilling Program organized the mission-specific Expedition 302 to the Lomonosov Ridge in the permanently ice-covered central Arctic Ocean. Comprising a flotilla of three icebreakers, it was a major logistical venture, and resulted in a huge scientific success. The same year the deep site on the Vøring Plateau was revisited and a thermal borehole observatory installed. During these legs a large quantity of core samples has allowed the scientific community to address fundamental questions in terms of continental margin development; plate tectonics; nature of basement; marine biostratigraphy; and the temporal and spatial evolution of the high-latitude northern climate and environments. However, major challenges remain, in particular related to the deep basins, ridges and margins of the Arctic Ocean proper. The next advance in knowledge is contingent on new technology and research infrastructure both for drilling and site surveying. Presently, plans for a new research icebreaker with drilling capability are being developed, the Aurora Borealis project. It will allow systematic drilling in most of the permanently ice-covered basins in the high north. The northern high latitudes have been predicted to contain vast hydrocarbon resources and cooperative ventures between industry and academia may be advantageous.

Pliocene climate change of the Southwest Pacific and the impact of ocean gateways

The transition from the early Pliocene “Warmhouse” towards the present “Icehouse” climate and the role of Gateway dynamics are intensively debated. Both, the constrictions of the Central American Seaway and the Indonesian Gateway affected ocean circulation and climate during the Pliocene epoch. Here, we use combined δ18O and Mg/Ca ratios of planktonic foraminifera (marine protozoa) from surface and subsurface levels to reconstruct the thermal structure and changes in salinities from the Southwest Pacific Deep Sea Drilling Project (DSDP) Site 590B from 6.5 to 2.5Ma. Our data suggest a gradual cooling of ~2°C and freshening of the sea surface during ~4.6–4Ma with an increased meridional temperature gradient between the West Pacific Warm Pool and the Southwest Pacific when the closing of the Central American Seaway reached a critical threshold. After ~3.5Ma, the restricted Indonesian Gateway might have amplified the East Australian Current, allowing enhanced heat transport towards the Southwest Pacific with reduced meridional temperature gradients when the global climate gradually cooled. At the same time our data suggest a cooling and freshening of Subantarctic Mode Water (SAMW) or/and an increased northward flow of SAMW towards Site 590B, possibly a first step towards the present Antarctic Frontal System.

Climate-driven body-size trends in the ostracod fauna of the deep Indian Ocean

Abstract: Body size is a common focus of macroevolutionary, macroecological and palaeontological investigations. Here, we document body-size evolution in 19 species-level ostracod lineages from the deep Indian Ocean (Deep Sea Drilling Program Site 253) over the past 40 myr. Body-size trajectories vary across taxa and time intervals, but most lineages (16/19) show net gains in body size. Because many modern ostracod taxa are larger in colder parts of their geographical range, we compared the timing and magnitude of these size changes to established Cenozoic deep-water cooling patterns confirmed through δ18O measurements of benthic foraminifera in the samples studied. These data show a significant negative correlation between size changes and temperature changes (ostracods get larger as temperatures get colder), and that systematic size increases only occur during intervals of sustained cooling. In addition, statistical support for an explicit temperature-tracking model exceeds that of purely directional evolution. We argue that this Cope’s Rule pattern is driven by secular changes in the environment, rather than any universal or intrinsic advantages to larger body sizes, and we note some difficulties in the attempts to link Cope’s Rule to observations made within a single generation.

Comments of the Society for Risk Analysis’s Past Presidents

The Society for Risk Analysis (SRA) has kindly authorised the EJRR to publish the comments of SRA Past Presidents on the Deepwater Horizon oil spill. Going beyond news media accounts, these comments offer a first hand analysis of the effects of the oil spill on the field of risk analysis and risk regulation. Following the call for a moratorium on deep-sea drilling in Europe by Gunther Oettinger, the European Commissioner for Energy, the publication of these comments seems particularly timely. (AA)

From microcontinents to extensional allochthons: witnesses of how continents rift and break apart?

ABSTRACT The conjunction of high-quality seismic surveys, deep sea drilling, and progress in numerical modelling has changed the way of thinking about how continents rift and oceans form. In particular the discovery of exhumed continental mantle and hyper-extended crust in deep-water rifted margins has led to a paradigm shift in research into the evolution of rifted margins. Although rifted margins now appear to be more complex and their architecture more diverse than previously thought, their study worldwide shows that there are in fact a limited number of structures observed in seismic images that characterize their architecture. These ‘building stones’ include crustal blocks of various sizes, often referred to as microcontinents, continental ribbons, H-blocks, extensional allochthons and outer highs. The aim of this paper is to define the characteristics of these continental blocks and to describe their relationship and position within the rifted margins, and to understand the underlying processes that govern their formation. We propose, using the example of the North Atlantic, that these crustal blocks are the result of specific rift processes that correspond to the sequential evolution from stretching, to thinning and exhumation of the continental lithosphere. We show that the relationship between the various rift structures provides fundamental insights into the controlling processes that thin and finally rupture continental lithosphere.