Deep Sea Drilling Research Articles

Two areoligeracean dinoflagellate cysts from the Carstone Formation (Lower Cretaceous) at Middlegate Quarry, North Lincolnshire, UK

Five Lower Albian (Lower Cretaceous) areoligeracean dinoflagellate cyst species are present in the Carstone Formation at Middlegate Quarry, North Lincolnshire, UK: Canninginopsis monile , Circulodinium deflandrei , Cyclonephelium compactum , Cyclonephelium intonsum and Cyclonephelium longispinatum . The taxonomy of Circulodinium deflandrei is reviewed with respect to 20 measured Carstone specimens. The taxonomy of Cyclonephelium longispinatum is reviewed with respect to 70 measured Carstone specimens and a study of 40 measured specimens from its type material in Site 361, Deep Sea Drilling Project Leg 40, offshore southwestern Africa. Circulodinium deflandrei and Cyclonephelium longispinatum have recently been considered by other workers to be junior synonyms, respectively, of Circulodinium hirtellum and Tenua anaphrissa . However, following detailed study of their morphologies, the synonymies are formally rejected here. An emended diagnosis is given for C. longispinatum . A re-assessment of the stratigraphical ranges of taxa co-occurring with the type material of C. longispinatum is consistent with a Late Albian to Early Turonian age range in Site 361.

Environmentally friendly and temperature resistant water-based drilling fluids with highly inhibitory synthetic nanocellulose polymers for deep sea drilling

The ocean is rich in sustainable hydrocarbon. The process of extracting these resources poses challenges such as coexistence of low temperature and high temperature, high pressure of deepwater and unpredictable shale formations. A kind of ionic crosslinking polymer consisting of N, N-dimethylacrylamide (DMA), 2-acrylamido-2-methylpropane sulfonic acid (AMPS), and Cellulose Nanofibers (CNF) (PADC), was synthesized to address these challenges. Cellulose was first oxidized to nanocellulose (CNF) through 2,2,6,6-tetramethylpiperidinyl-1-oxide (TEMPO) oxidation. Subsequently, the ionic crosslinking polymer, consisting of DMA, AMPS, and CNF, was synthesized using ionic crosslinking polymerization. The surface characteristics and morphology were characterized by transmission electron microscopy (TEM), nanoparticle size analysis, and zeta potential analysis. The structural composition was analyzed by Fourier Transform Infrared Spectroscopy (FT-IR). The shale inhibition mechanism was investigated through contact angle and pressure transmission experiments. The results indicated that the average length of PADC is approximately 1450 nm, with an average diameter of less than 100 nm and contains sulfonic acid groups. The shale contact angle increased from 16.75° to 82°, indicating that PADC increased the hydrophobicity of the shale by 390%. Pressure transfer experiments show that PADC can reduce shale permeability by 37%, which means PADC has good hydration inhibition performance. In addition, a drilling fluid system suitable for deep sea drilling was proposed. The drilling fluid system exhibits good rheological properties at 160 °C and 0 °C. The fluid loss after hot rolling at 160 °C is less than 12 mL. The linear expansion of shale core after 16 h is only 0.7%, and the rolling recovery rate at 160 °C is as high as 99.48%. Luminescent bacteria EC50 is 2.0 × 105 mg/L, which means it is non-toxic and environmentally friendly. And drilling fluid conforms to the power law flow model. Therefore, the drilling fluids proposed in this paper can meet the requirements of deep sea drilling in terms of rheological properties and filtration loss properties at 0–160 °C, and can seal shale pores and inhibit shale hydration through the ionic cross-linking PADC. This research offers insights into the utilization of cellulose in well drilling processes and provides references for designing deep sea drilling fluids.

Geochemical peculiarities of the Atlantic Pleistocene sediments

In the geochemical review based on records from cruises of International project of Deep-Sea Drilling (phases of DSDP, ODP, IODP) and other literature data we presented tables of average arithmetic chemical composition, meanweighted chemical composition, accumulation rates, and mass accumulation rates of chemical components. These tables can be used for comparative analysis with sediments of the same or other stratons in different oceanic basins and also with paleooceanic sediments on the continents. Terrigenous matrix dominates within lithogenic matter. Using methods of mathematical statistics we revealed main geochemical associations and base factors determinating the chemical composition of studied sediments. Masses of oxides of petrogenic elements and a number of trace elements have been calculated for Pleistocene sediments. We managed to take an idea about average chemical composition of the Atlantic Pleistocene.

Excellent tribocorrosion resistance of additively manufactured Ti-based heterogeneous composite coating via hardening and toughening effects

To improve the tribocorrosion resistance of oil drill pipes used in deep-sea drilling, a Ti-based composite coating was successfully fabricated by laser direct energy deposition technology on the TC4 titanium alloy surface. The microstructure analysis showed that a new heterogeneous structure of multistage strengthening phases (micron-sized TiN phases and nano-sized TiB phases) distributed on the β matrix (soft Cu-rich phases and hard Mo-rich phases) was formed, and the size of β grain was refined to 2 μm with the content of Cu higher than 12 wt.%. The microhardness of the composite coating was increased to more than 700 HV0.2 due to the solution strengthening of Mo elements and the formation of hard TiN phases. At the same time, the fracture toughness of 12Cu composite coating was significantly increased to 8.37 MPa m1/2, which was attributed to the combined effect of grain refining, high-density dislocations in Cu-rich phases, and nanoscale TiB phases. The synergistic enhancement of hardness and toughness of 12Cu composite coating promoted the generation of titano-molybdenum-copper composite oxide film on the worn surface, and the tribocorrosion resistance increased more than 7 times compared with TC4.

Biogenic silica accumulation and diatom assemblage variations through the Eocene-Oligocene Transition: A Southern Indian Ocean versus South Atlantic perspective

It is widely interpreted that there is a significant link between climate cooling at the Eocene-Oligocene Transition (EOT; ∼34 Ma) and subsequent diatom proliferation in the world's oceans during the mid to late Cenozoic. Yet, our understanding of biogenic silica flux through the EOT interval is based on limited data from a few sites, and there are many complications in making a meaningful comparison based on biogenic silica concentration data generated using different techniques. Here, we present new biogenic opal flux and diatom assemblage records across EOT from Ocean Drilling Program Site 748 (Southern Kerguelen Plateau, southern Indian Ocean), in addition to new biogenic opal flux records from the South Atlantic (Deep Sea Drilling Project Site 511, Falkland Plateau and Ocean Drilling Program Site 1090, Agulhas Ridge). Observed opal flux shifts and variability at Site 748 are consistent with published data from nearby Site 744; both sites show considerable shifts in biogenic opal accumulation rates corresponding to shifts in published benthic oxygen isotope records through the EOT. In contrast, our new opal flux record for Site 511, derived from biogenic opal concentration measurements via spectrophotometry, differs from the published record derived from insoluble residues, whereas new data generated for Site 1090 are generally consistent with previously published flux reconstructions. The South Atlantic biogenic opal flux records, however, are dissimilar from one another, and both are dissimilar from the Southern Indian Ocean records. Also, the taxonomic composition of the diatom assemblages from Sites 511, 748 and 1090 display considerable differences, with hemiauloids and rhizosolenids – generally inferred as indicative of oligotrophic conditions – being the dominant diatoms at the Southern Kerguelen Plateau (Site 748). Published records show that hemiauloid taxa are absent from the earliest Oligocene interval at Site 1090, which is widely seen as a record of deposition from nutrient-rich waters sustaining abundant diatom assemblages. These differences in diatom assemblages testify to regional differences in nutrient concentrations. In particular, the timing of biogenic opal flux pulses between Sites 1090 and 748 imply a shift in the locus of opal deposition to areas further south in the Southern Ocean across the EOT, likely related to proto-ACC development and strengthening of frontal boundaries. Thus, combined geochemical and micropaleontological evidence points to a regionally variable rather than a global, unified opal flux response to climate cooling through the Eocene-Oligocene Transition.

Re-evaluation of the Mesozoic–Cenozoic biostratigraphy of the Laurentian Subbasin of the Scotian Basin, offshore eastern Canada

We use new and existing nannofossil, palynological, and microfossil biostratigraphic data in conjunction with lithologic and geophysical logs from four wells to establish a series of sequence-stratigraphic events in the Mesozoic–Cenozoic of the Laurentian Subbasin of offshore Newfoundland, eastern Canada. Well biostratigraphic events are integrated with reflection seismic in the area to correlate regional seismic stratigraphic surfaces. The four wells are: Bandol-1, Emerillon C-56, East Wolverine G-37, and Heron H-73. We extend the event stratigraphic scheme previously developed for the Scotian Margin, offshore Nova Scotia, into new areas to the east along the southern Grand Banks, where we recognize four new well-log sequence stratigraphic events, and we modify the definition of a previously recognized regional surface. The new and modified regional surfaces are the Early Albian Unconformity, the Late Bathonian Maximum Flooding Surface (MFS), the Late Bajocian MFS (renamed from Bathonian/Bajocian MFS), the ?Bajocian/Toarcian Unconformity, and the Late Pliensbachian MFS. We recognize the "Avalon Unconformity" and "Base-Tertiary Unconformity" of previous studies as amalgamations of multiple smaller-scale unconformities and refine their age in the studied wells. A major improvement over our earlier Scotian Margin event schemes is the extension of the event stratigraphy into the Early Jurassic using a suite of marine biostratigraphic markers. We compare the Early Jurassic event scheme to Deep Sea Drilling Project Site 547B on the conjugate Moroccan Margin to better constrain potential source rock intervals and the early history of the central Atlantic Ocean.

Biochronology and evolution of Pulleniatina (planktonic foraminifera)

Abstract. Pulleniatina is an extant genus of planktonic foraminifera that evolved in the late Miocene. The bottom and top occurrences of its six constituent morphospecies (P. primalis, P. praespectablis, P. spectabilis, P. praecursor, P. obliquiloculata, P. finalis) provide a series of more or less useful constraints for correlating tropical and subtropical deep-sea deposits, as do some prominent changes in its dominant coiling direction and a substantial gap in its record in the Atlantic Ocean. Biostratigraphic information about these events has accumulated over many decades since the development of systematic deep-sea drilling in the 1960s, during which time the geochronological framework has evolved substantially, as have taxonomic concepts. Here we present new data on the biochronology of Pulleniatina from International Ocean Discovery Program Site U1488, which has a record of its entire evolutionary history from the centre of its geographic range in the Western Pacific Warm Pool. We then present and compare revised calibrations of 183 published Pulleniatina bioevents worldwide, with stated sampling errors as far as they are known, using a consistent methodology and in the context of an updated evolutionary model for the genus. We comment on the reliability of the various bioevents; their likely level of diachrony; and the processes of evolution, dispersal, and extinction that produced them.

In-situ ultrasonic measurement for hydrate pressure cores sampled by deep sea drilling

Deep sea drilling core detection and analysis is a convenient technology deployed by drilling platforms or geological exploration vessels. This paper develops an in-situ ultrasonic detection unit which can be combined with long distance pressure-holding transfer of hydrate cores, based on the original Pressure-core On-board Transfer and Analysis System (POTAS). The screw-in design of transducers allows for rapid adjustments in measurement distance during hydrate core transfer, while effectively solving the problems of high-pressure resistance. The drilling depth and core diameter are firstly used as parameters for wave velocity calculation. The method simplifies the solution and error analysis of in-situ ultrasonic measurement of hydrate pressure cores under complex drilling operation conditions. The introduction of two engineering-related parameters takes full account of the influence of sedimental burial depths and drilling tool selection on in-situ ultrasonic detection, and provides important support for ultrasonic measurements of hydrate pressure cores.

Chemical Composition of the Indian Ocean Pleistocene Sediments

Geochemical review of Pleistocene sediments from the Indian Ocean has been performed based on reports of deep-sea drilling cruises and other literature references. We created the data base including more than 2000 chemical analyses of sediment samples. As result we compiled a number of tables concerning the mean ariphmetic composition of lithogenic and biogenic sediments. All data have been normalized on PAAS (PostArchean Australean shales). We revealed the dominant role of terrigenous clastics in formation of chemical composition of noncarbonate sediments and noncarbonated matter of planktic carbonates as well. Main geochemical associations have been established together with three main factors determinating sediment composition: terrigenous, carbonate and hydrogenous. We managed to calculate meanwheighted chemical composition, accumulation rates of elements in the studied sediments and their mass accumulation rates. All these parameters of the chemical composition can be used later for comparative analysis with analog para-meters from other ocean sediments within frames of Pleistocene straton in the World Ocean.

A fully coupled thermo-poro-elastic model predicting the stability of wellbore in deep-sea drilling. Part B: Sensitivity analysis

A good understanding of the mechanical behavior around the wellbore is important for predicting wellbore stability in deep-sea drilling (DSD) for oil and gas production. In Part A of the companion papers, a fully coupled thermo-poro-elastic (THM) model has been developed by combining fluid circulation in the wellbore and rock deformation in the reservoir to predict the mechanical behaviors of a wellbore/reservoir system during DSD, and the analytical solution is obtained in Laplace space. In this paper, a comparison is made first to show the difference between land drilling (LD) and DSD. A sensitivity analysis is carried out to study the effect of different parameters, i.e. drilling depth, rock permeability, density and injection rate of drilling fluid, on the mechanical behaviors of wellbore/reservoir system. The results show that (1) The injection rate plays a dominant role in affecting the BHT. In the case studied, the BHT decreases by around 9 °C when the injection rate increases by 4 kg/s (3.64 × 10−3 m3/s). This will lead to a large temperature decrease after long time circulation. The injection rate does not have a significant effect on the pressure evolution; (2) Due to existence of the geothermal gradient, when the drilling depth varies, the change of temperature and pressure in the rock formation is approximately linearly proportional to the change in the drilling depth. The larger the drilling depth is, the larger the absolute value of the displacement and failure risk at the wellbore; (3) When the rock permeability varies from k = 4 × 10−8 D to 4 × 10−5 D, the hoop stress and failure index (FI) distribution change at small time; (4) Too large and too small fluid densities may cause wellbore instability; (5) The DSD model is degenerated into the LD model when the depth of seawater approaches 0 m. The difference in the temperature and pressure changes between the two models are relatively small. While the magnitude of radial and hoop stresses in LD is larger than that in DSD due to the in-situ stress fields and the failure index in LD is lower than that in DSD around the wellbore, but larger in the far field.

A fully coupled thermo-poro-elastic model predicting the stability of wellbore in deep-sea drilling. Part A: Analytic solutions

Wellbore stability is important to deep-sea drilling (DSD) for exploiting offshore oil and gas resources. Accurate prediction of the mechanical behaviors of rock formation around the wellbore can effectively prevent wellbore failure via adjusting mud weight. In this paper, a fully coupled thermo-poro-elastic (THM) model is developed by combining fluid circulation in the wellbore and rock deformation in the reservoir. Transient heat transfer in the wellbore/reservoir and heat exchange between the tubing, annulus, riser, casing, cement, seawater and rock formation are considered. By decomposing the problem into axisymmetric and antisymmetric sub-problems, the analytical solutions for transient temperature, pressure and stress in the rock formation and fluid temperature changes in the drill pipe, annulus and seawater near the riser are obtained and validated against with the numerical solutions, existing fluid circulation model, field measurement data and the existing model without considering fluid circulation. After that, a typical case study is carried out to show the mechanical behavior around the wellbore. It is found that the proposed fully coupled THM model has a high accuracy with a relative error of around 1.2%. There is a large difference in the predicted bottomhole temperature (BHT) and thus the temperature in the reservoir between the models with and without considering fluid circulation in the wellbore. An assumption of constant temperature boundary condition may lead to overestimated or underestimated results depending on the selection of the assigned wellbore temperature. In the DSD case studied, the rock formation at the upper part of the reservoir (Z < 0.40) is continuously heated and the rock formation at the lower part (Z > 0.6) of the reservoir is continuously cooled during fluid circulation, which thus results in a complex heat transfer and thus mechanical behavior in the wellbore/reservoir system, especially near the wellbore. The bottomhole temperature (BHT) decreases by 38.9 K due to cold fluid circulation from 3.68 min to 25.68 days, which can lead to 14.59 MPa tensile stress that cannot be ignored for wellbore stability analysis. The proposed analytical model provides a useful tool to predict the mechanical behaviors such as the transient temperature, pressure, displacement and stresses in the wellbore/reservoir system during fluid circulation in DSD. It runs efficiently in terms of seconds per case study in a portable laptop computer and can also work a benchmark for other numerical methods. However, the fully coupled THM model and its analytical solution are based on several assumptions, such as the heat generated by the drill bit rotation is ignored and only the liquid phase is considered, which requires further investigation.

Paleoecological Inferences for Turborotalita Nikolasi (Koutsoukos, 2014) Based on Stable Carbon and Oxygen Isotopes

Abstract The species Turborotalita nikolasi first appeared immediately after the Cretaceous-Paleogene (K-Pg) boundary and is considered the progenitor of all Cenozoic normal perforate species. We present δ18O and δ13C isotope signals of T. nikolasi specimens and compare them with those of mixed-layer (Guembelina cretacea), thermocline (Subbotina trivialis and Chiloguembelina midwayensis), and deep water (Nuttalides truempyi) species with glassy shell preservation from São Paulo Plateau [Deep Sea Drilling Project (DSDP) Site 356]. Turborotalita nikolasi δ18O values are similar to those of G. cretacea, suggesting that both species cohabited the mixed layer. Values of δ13C for T. nikolasi are higher than those of all other planktic foraminiferal species, which may have been due to the presence of photosymbionts, and thus might represent the earliest known record of photosymbiosis for Cenozoic planktic foraminifera. Nuttalides truempyi δ13C values are remarkably high at Site 356, indicating low 12C abundance in deep waters, which could be related to reduced inefficiency of the biological pump in transporting 12C to the bottom of the ocean after the K-Pg boundary during the first ∼300 kyr of the Danian.

Design and Experimental Study of Core Bit for Hard Rock Drilling in Deep-Sea

The hard rock stratum will seriously affect the efficiency of deep-sea drilling and greatly increase the cost of drilling operations due to its complexity. In ocean drilling operations, the design of the bit is critical. Therefore, the core bit should be able to drill in a variety of formations, especially in hard rock stratum, with the function of reducing the need to change the bit due to formation changes and improving the drilling efficiency. In this paper, three different core bits were designed according to the hard rock stratum of the seabed: the roller bit, diamond bit and bionic bit. According to the test results, it was observed that: (1) It is fully proven that the roller core bit has the characteristics of stable drilling in hard strata, small torque and high drilling efficiency. The same method can realize the core in shallow soft strata through the setting of drilling parameters. (2) For the diamond bit, the field test data show that the new formula diamond bit has a good adaptability to the changing hard rock strata in this area, with an average rate of penetration (ROP) of 4.4 m/h and a bit life of 137.75 m. (3) For the bionic bit, field experiment data showed that drilling in the formation lithology was gray green tuff, which had a core recovery up to 100%. The average ROP was 1.35 m/h, and the highest ROP was 1.88 m/h. The design and experiment of three kinds of drill bits have effectively solved the technical problem of efficient drilling in deep-sea hard-rock stratum.

An araphid diatoms from marine Miocene deposits of the Fisher Massif (Prince Charles Mountains, East Antarctica)

The Late Cenozoic history of Antarctica is reflected in the few ice-free ground deposits of the continental marginal zone. While the planktonic diatom flora of the Cenozoic Antarctic, which has dominated the biocenoses of the Southern Ocean since the Eocene, has been fairly well studied based on Deep-Sea Drilling, the benthic diatoms found in sediments have been studied extremely poorly. In the materials collected during the 52nd and 53rd Russian Antarctic expeditions in 2006–2008 from deposits of the Fisher Massif (central part of the Prince Charles Mountains), a rich fossil diatom complexes were found, including more than 80 mainly benthic taxa. Of these, 13 species of araphid diatoms have been studied and described.

Origin of the southern Ryukyu Forearc Terrace: A seaward-protrusion of arc crust elevated by subducted asperities?

• The southern Ryukyu Forearc Terrace exhibits an extremely high free-air gravity anomaly and a thick upper crust. • The rest of the southern Ryukyu forearc region is characterized by prominent forearc basins and a large-volume accretionary prism. • The forearc terrace represents a remnant seaward-protruded arc crust. • The bulged and uplifted basement of the forearc terrace is most probably caused by the subduction of asperities. A forearc terrace with distinct topography and gravity anomalies lies within the Ryukyu forearc between 125°E and 127°E. The origin and tectonic affinity of this terrace remain uncertain. This study attempts to depict the structural characteristics of the forearc terrace and to trace its origin and formation mechanisms through a comprehensive examination of newly acquired geophysical data combined with the results of previous surveys. The forearc terrace exhibits shallow bathymetry, an extremely high free-air gravity anomaly, a shallow buried acoustic basement, a thin sedimentary cover, and a thick upper crust. In contrast, the rest of the southern Ryukyu forearc region is characterized by a steep upper forearc slope, prominent forearc basins, a deeply buried acoustic basement, and a large-volume accretionary prism. The forearc terrace represents a remnant seaward-protrusion of arc crust created after the frontal portion of the arc crust had been removed by subducted ridges or other types of linear bathymetric highs. This is in contrast to other formation mechanisms such as a block sliding seaward along strike-slip faults or an accretion of exotic terrane from the outer margin of the original arc crust after being scraped off from the subducting oceanic crust. The bulged and uplifted basement of the forearc terrace is most likely associated with subducted seamounts. Further studies, especially deep-sea drilling, are necessary to verify the nature and origin of the forearc terrace.

New evidences of subaerial volcanism as a trigger for the Kilian event (Aptian-Albian transition) and major climatic changes from offshore Morocco (DSDP Site 545)

The Aptian-Albian transition is characterized by the presence of four organic-rich intervals all linked with major disturbances of the carbon cycle. Among these, the second subevent of the oceanic anoxic event (OAE) 1b, also called Kilian event, has an Aptian-Albian transition age and is characterized by a negative carbon isotope excursion. On the contrary of the Paquier OAE1b subevent, the Kilian event was not extensively studied and its triggering mechanisms and its consequences on regional climates remain uncertain. Here we present a geochemical (Rock-Eval, Mercury) and mineralogical (clay minerals) study on late Aptian-early Albian sediment cores from the Deep-Sea Drilling Program (DSDP) Site 545 (offshore Morocco, Eastern North Atlantic) where a Kilian level equivalent is present. Mercury (Hg) content results show two main peaks in the late Aptian, immediately below and above the Kilian level equivalent. The absence of correlations between Hg and total organic carbon and Hg and CaCO 3 indicates that the mercury content is mainly related to subaerial volcanic activity, probably issued from the emplacement of the Kerguelen large igneous province in the Indian Ocean. Mineralogical analyses show that the clay content, in our studied interval, mainly reflect the weathering and climatic conditions in Northwest Africa. The evolution in clay mineral assemblages depicts three distinctive climatic intervals: (i) a seasonally contrasted semi-arid climate below the first Hg anomaly; (ii) a moister and warmer climate during the Kilian level equivalent deposition; and (iii) a rapid transition toward more arid climate post Kilian level equivalent deposition that is linked with the second Hg anomaly (large increases in illite and palygorskite). Therefore, our study confirms that the Kerguelen volcanic activity was probably the trigger of the Kilian event and shows that the resulting changes in the carbon cycle caused two major climate changes before and after the Kilian event and a long term aridification of Northwest Africa. • Hg anomalies occurs immediately below and above the Kilian level. • Kerguelen volcanic activity was likely the trigger of the Kilian event • Three distinct climatic periods can be recognized along the late Aptian. • late Aptian represents a turning point for the Cretaceous climate changes.

Birth of the Pearl River at 30 Ma: Evidence from sedimentary records in the northern South China Sea

The Pearl River drains the South China Block and delivers large amounts of sediments to the northern South China Sea, and its development can be closely linked to the regional paleoenvironmental changes. However, the evolutionary history of the Pearl River has been poorly understood, mainly because of the lack of continuous and high-resolution sedimentary records over a long geological time. In this study, we present multiple new analytical results, including clay mineral assemblages and Sr-Nd isotopic compositions of the <2 μm siliciclastic sediments, from the latest deep sea drilling core in the northern South China Sea from International Ocean Discovery Program (IODP) Site U1501. We aim to reconstruct the evolutionary history of the Pearl River by tracing changes in clay mineral assemblages and Sr-Nd isotopic compositions. Provenance analysis indicates that the sediment source experienced a significant change between 32 and 30 Ma. Specifically, sediments prior to 32 Ma were derived from the southeastern Cathaysia coast, whereas sediments post to 30 Ma were mainly supplied by a proto-Pearl River. This provenance transition indicates that the modern-scale Pearl River has fully developed at least ∼30 Ma and began to contribute sediments to the northern South China Sea. We additionally compared the timings of major climatic and tectonic events in this region, and suggest that the topographic uplift of the SE Tibetan Plateau most likely drove the large-scale westward expansion of rivers drainage from the coast located in the Cathaysia Block to the interior of Yangtze Block. As a result of this fluvial drainage evolution followed by the development of Pearl River, geochemical and clay mineralogical characteristics of the deposits in the northern South China Sea correspondingly changed.

Trace metal and sulfur cycling in a hydrothermally active arc volcano: deep-sea drilling of the Brothers volcano, Kermadec arc, New Zealand

Trace metal and sulfur cycling in a hydrothermally active arc volcano: deep-sea drilling of the Brothers volcano, Kermadec arc, New Zealand

Ham ve Genleştirilmiş Perlitin Su Bazlı Sondaj Çamuruna Etkisinin Karşılaştırılması

Sondaj uygulamalarında başarılı bir operasyon gerçekleştirmek için kullanılan sondaj akışkanının performansı oldukça önemlidir. Son zamanlarda özellikle pahalı teknolojilerin kullanıldığı yatay ve derin deniz sondajlarındaki gelişmelerin yanı sıra sondaj çamuru teknolojisindeki gelişmeler de ekonomik anlam kazanmıştır. Bu çalışmada, ham perlit ve genleştirilmiş perlitin su bazlı sondaj çamuruna etkisinin karşılaştırılması amaçlanmıştır. Bu amaçla, su bazlı sondaj çamurları hazırlanmış ve hazırlanan çamur numunelerine farklı oranlarda (0.1 - 5 % k.h-1) ham perlit ve genleştirilmiş perlit ikame edilmiştir. Hazırlanan sondaj çamurlarının plastik viskozitesi, görünür viskozitesi, kopma noktası, jel mukavemeti değerleri (10 saniye ve 10 dakika) gibi reolojik özellikleri FANN viskozimetresi, filtrasyon kaybı özellikleri de API Filter Press aracılığıyla tespit edilmiştir. Tüm ölçümler Amerikan Petrol Enstitüsü (API) standartlarına uygun bir şekilde gerçekleştirilmiştir. Ham ve genleştirilmiş perlitin ayrı ayrı eklenmesi ile hazırlanan sondaj çamurlarının reolojik ve filtrasyon özellikleri ilk olarak katkısız sondaj çamuruyla daha sonra da kendi içlerinde karşılaştırılmıştır. Ham perlit ve genleştirilmiş perlitin su bazlı sondaj çamurunun reolojik özellikleri ile filtrasyon kaybı değerlerine olumlu yönde katkı sağladığı tespit edilmiştir. Ayrıca genleştirilmiş perlitin, ham perlite oranla daha iyi bir etkiye sahip olduğu görülmüştür.

In Pursuit of Understanding, a Career in Marine Geology

AbstractMy interest in the oceans first developed when I was a teenager, but I did not actually go to sea until I was in the U.S. Navy. With that experience, I developed a love of the oceans and an interest in oceanography. My graduate training was a time when oceanography and marine geology were blossoming with new ideas and new tools to explore the ocean world. The theory of plate tectonics was becoming widely accepted and scientific ocean drilling was just starting. My thesis study area was in the tropical Pacific. Soon after receiving my PhD, I sailed on Deep Sea Drilling Project Leg 8, which drilled the first transect across the Pacific equator. The nature of the sediments there posed many scientific questions that continued to intrigue me. Some of these questions remained unanswered for a long time. Early in my career I was fortunate to work with a group of specialists from outside my field of expertise to study the global climate during the last glacial maximum (the CLIMAP Project). Subsequently, I spent 8 years working in the oil industry. This experience taught me the skills of interpreting seismic reflection records that help unravel the history of sediment deposition. When I returned to academia, these skills proved particularly useful in studies of large lakes. Late in my career, I returned to studies of the tropical Pacific, where new tools and techniques helped answer some of my unanswered questions.