Physical properties and bulk minerals from IODP Holes 308-U1322B, U1322D and U1324B

How the micro-scale fabric of clay-rich mudstone evolves during consolidation in early burial is critical to how they are interpreted in the deeper portions of sedimentary basins. Core samples from the Integrated Ocean Drilling Program Expedition 308, Ursa Basin, Gulf of Mexico, covering seafloor to 600 meters below sea floor (mbsf) are ideal for studying the micro-scale fabric of mudstones. Mudstones of consistent composition and grain size decrease in porosity from 80% at the seafloor to 37% at 600 mbsf. Argon-ion milling produces flat surfaces to image this pore evolution over a vertical effective stress range of 0.25 (71 mbsf) to 4.05 MPa (597 mbsf). With increasing burial, pores become elongated, mean pore size decreases, and there is preferential loss of the largest pores. There is a small increase in clay mineral preferred orientation as recorded by high resolution X-ray goniometry with burial.

Elements and mineralogical compostions from different sediment cores off the southern China Sea

The mineralogy, major and trace elements, and neodymium and strontium isotopes of surface sediments in the South China Sea (SCS) are documented with the aim of investigating their applicability in provenance tracing. The results indicate that mineralogical compositions alone do not clearly identify the sources for the bulk sediments in the SCS. The Nd isotopic compositions of the SCS sediments show a clear zonal distribution. The most negative epsilon-Neodymium values were obtained for sediments from offshore South China (-13.0 to -10.7), while those from offshore Indochina are slightly more positive (-10.7 to -9.4). The Nd isotopic compositions of the sediments from offshore Borneo are even higher, with epsilon-Neodymium ranging from -8.8 to -7.0, and the sediments offshore from the southern Philippine Arc have the most positive epsilon-Neodymium values, from -3.7 to +5.3. This zonal distribution in epsilon-Neodymium is in good agreement with the Nd isotopic compositions of the sediments supplied by river systems that drain into the corresponding regions, indicating that Nd isotopic compositions are an adequate proxy for provenance tracing of SCS sediments. Sr isotopic compositions, in contrast, can only be used to identify the sediments from offshore South China and offshore from the southern Philippine Arc, as the 87Sr/86Sr ratios of sediments from other regions overlapped. Similar zonal distributions are also apparent in a La-Th-Sc discrimination diagram. Sediments fromthewestmargin of the SCS, such as those fromBeibuwan Bay, offshore fromHainan Island, offshore from Indochina, and from the Sunda Shelf plot in the same field, while those offshore from the northeastern SCS, offshore from Borneo, and offshore from the southern Philippine Arc plot in distinct fields. Thus, the La-Th-Sc discrimination diagram, coupledwith Nd isotopes, can be used to trace the provenance of SCS sediments. Using this method, we re-assessed the provenance changes of sediments at Ocean Drilling Program (ODP) Site 1148 since the late Oligocene. The results indicate that sediments deposited after 23.8 Ma (above 455 mcd: meters composite depth) were supplied mainly from the eastern South China Block, with a negligible contribution from the interior of the South China Block. Sediments deposited before 26 Ma (beneath 477 mcd) were supplied mainly from the North Palawan Continental Terrane, which may retain the geochemical characteristics of the materials covered on the late Mesozoic granitoids along the coastal South China. For that the North Palawan Continental Terrane is presently located within the southern Philippine Arc but was located close to ODP Site 1148 in the late Oligocene. The weathering products of volcanic material associated with the extension of the SCS ocean crust also contributed to these sediments. The rapid change in sediment source at 26-23.8 Ma probably resulted from a sudden cessation of sediment supply from the North Palawan Continental Terrane. Wesuggest that the North Palawan Continental Terrane drifted southwards alongwith the extension of the SCS ocean crust during that time, and when the basin was large enough, the supply of sediment from the south to ODP Site 1148 at the north slope may have ceased.

Geochemical and mineralogical analyses of clay-rich intervals in ODP Sites 166-1006 and 166-1007

The western flank of the Great Bahama Bank, drilled during ODP Leg 166 at seven sites, represents a prograding carbonate sequence from late Oligocene to Holocene [Eberli et al., Proc. ODP Init. Reports 166 (1997)]. The signatures of the detrital input and of diagenetic alteration are evident in clay enriched intervals from the most distal Sites 1006 and 1007 in the Straits of Florida. Mineralogical and chemical investigations (XRD, TEM, SEM, ICP-MS) run on bulk rocks and on the clay fractions enable the origin and evolution of silicate parageneses to be characterized. Plio-Pleistocene silt and clay interbeds contain detrital clay assemblages comprising chlorite, illite, interstratified illite smectite, smectite, kaolinite and palygorskite. The greater smectite input within late Pliocene units than in Pleistocene oozes may relate either varying source areas or change in paleoclimatic conditions and weathering intensity. The clay intervals from Miocene-upper Oligocene wackestone sections are fairly different, with prevalent smectite in the fine fraction, whose high crystallinity and Mg contents that point towards an authigenic origin. The lower Miocene section, below 1104 mbsf, at depths where compaction features are well developed, is particularly characterized by abundant authigenic Na-K-clinoptilolite filling foraminifer tests. The authigenic smectite and clinoptilolite paragenesis is recorded by the chemical trends, both of the sediment and the interstitial fluid. This diagenetic evolution implies Si- and Mg rich fluids circulating in deeper and older sequences. For lack of any local volcaniclastic input, the genesis of zeolite and the terms of water rock interaction are discussed. The location of the diagenetic front correlates with that of the seismic sequence boundary P2 dated as 23.2 Ma. This correspondence may allow the chronostratigraphic significance of some specific seismic reflections to be reassessed.

Mineralogy, grain size composition, bulk carbonate isotopic ratios and ages of ODP Site 182-1128 sediments

This report presents mineralogic and geochemical data from Ocean Drilling Program Leg 182 Site 1128 in the Great Australian Bight. Clay mineralogy is dominated by mixed-layer illite-smectite, followed by minor amounts of kaolinite and illite, with intervals of pure smectite. Carbonate mineralogy is exclusively low-Mg calcite, except for one interval of dolomite in lower Oligocene sediments. Carbonate increases significantly in upper Eocene sediments, decreases through the lower Oligocene, then increases again in the Neogene. Quartz is present as a minor component that covaries inversely with carbonate. High-resolution sampling associated with Chron 13 normal (early Oligocene) reveals high-frequency (~23 k.y.) fluctuations in clay mineralogy and carbonate abundance and a positive oxygen and carbon isotope excursion (in bulk carbonates) related to Antarctic glaciation.

Geochemistry and mineralogy of variably altered dacite volcanic rocks from ODP Leg 193 sites, PACMANUS field

A geochemical, mineralogical, and isotopic database comprising 75 analyses of Ocean Drilling Program (ODP) Leg 193 samples has been prepared, representing the variable dacitic volcanic facies and alteration types observed in drill core from the subsurface of the PACMANUS hydrothermal system (Table T1. The data set comprises major elements, trace and rare earth elements (REE), various volatiles (S, F, Cl, S, SO4, CO2, and H2O), and analyses of 18O and 86Sr/87Sr for bulk rock and mineral separates (anhydrite). Furthermore, normative mineral proportions have been calculated based on the results of X-ray diffraction (XRD) analysis (Table T2) using the SOLVER function of the Microsoft Excel program. Several of the samples analyzed consist of mesoscopically distinctive domains, and separate powders were generated to investigate these hand specimen-scale heterogeneities. Images of all the samples are collated in Figure F1, illustrating the location of each powder analyzed and documenting which measurements were performed.

Biostratigraphy, magnetostratigraphy, granulometry, isotopes and clay mineral composition of ODP Site 188-1165

During Ocean Drilling Program Leg 188 to Prydz Bay, East Antarctica, several of the shipboard scientists formed the High-Resolution Integrated Stratigraphy Committee (HiRISC). The committee was established in order to furnish an integrated data set from the Pliocene portion of Site 1165 as a contribution to the ongoing debate about Pliocene climate and climate evolution in Antarctica. The proxies determined in our various laboratories were the following: magnetostratigraphy and magnetic properties, grain-size distributions (granulometry), near-ultraviolet, visible, and near-infrared spectrophotometry, calcium carbonate content, characteristics of foraminifer, diatom, and radiolarian content, clay mineral composition, and stable isotopes. In addition to the HiRISC samples, other data sets contained in this report are subsets of much larger data sets. We included these subsets in order to provide the reader with a convenient integrated data set of Pliocene-Pleistocene strata from the East Antarctic continental margin. The data are presented in the form of 14 graphs (in addition to the site map). Text and figure captions guide the reader to the original data sets. Some preliminary interpretations are given at the end of the manuscript.

Characteristics and distribution of Neogene turbidites at ODP Site 108-657

Numerous and variable silty-sandy siliciclastic turbidites were observed in Neogene pelagic sediments (late Miocene to Holocene) at Site 657: (1) thick-bedded, coarse-grained and thin-bedded, fine-grained turbidites; and (2) turbidites composed of eolian dune sand and shallow-water bioclasts or of fluvial-sand or mixed sandy component assemblages. The stratigraphic distribution of these turbidites indicates five periods during which climatic conditions and material sources change. Turbidite occurrence prior to 6.2 Ma (late Miocene) is sparse; the deposits contain coarse and fine-grained turbidites with quartz grains of eolian or mixed origin suggesting the existence of arid conditions at about 8.5 and 6.5 Ma. A coarse-grained turbidite of fluvial origin, recording a humid climate, occurs at about 6.2 Ma. During the early Pliocene, turbidites are frequent (15/Ma); they contain only fine-grained sequences comprising material of mixed origin, which indicates a more humid climate perhaps. The late Pliocene starts with rare coarse-grained turbidites of wind-transported sand while the uppermost Pliocene deposits show a higher frequency of fine-grained sequences (10/0.7 Ma) composed mainly of fluvial material. During the early Pleistocene, similar high turbidite frequency was observed (20/1.3 Ma) but with a total lack of eolian supply. During the last 0.7 Ma, the frequency decreases and the sequences are characterized by highly variable sediment components that could be related to strong variations of climatic conditions. The sedimentary characteristics of turbidites are mainly controlled by sediment source and climate. The frequency must be influenced by sea-level variations, by cyclic processes of climatic origin, and possibly by variations in the continental slope morphology. Clay mineral assemblages suggest a south Saharan source of terrigenous material during the late Miocene and the Pliocene and a northwest Saharan source during the Pleistocene.

Clay mineralogy on five NBP cores

During 2006, the SHALDRIL program recovered cores of Eocene through Pliocene material at four locations in the northwestern Weddell Sea, each representing a key period in the evolution of the Antarctic Peninsula ice cap. The recovered cores are not continuous, yet they provide a record of climate change with samples from the late Eocene, late Oligocene, middle Miocene, and early Pliocene and represent the only series of samples recovered from the northwestern Weddell Sea and spanning the Cenozoic and the initial growth of the peninsula ice cap. Late Eocene sediments sampled in the James Ross Basin are typically characterized by very dark greenish-gray muddy fine sand with some preserved burrowing and are interpreted to represent a shallow water continental shelf setting. Rare dropstones, primarily of well-cemented sandstones and minor ice-rafted material consisting of angular grains with glacially influenced surface features record the onset of mountain glaciation, the earliest such evidence in the region. The remaining cores were collected on the Joinville Plateau to the north of the James Ross Basin. The late Oligocene sediments consist of dark gray sandy mud with some clay lenses and many burrows, likely representing a distal delta or shelf setting. This core contains only very few and small dropstones, and the individual grains show decreased angularity and fewer glacial surface features relative to late Eocene deposits. The middle Miocene strata are composed of pebbly gray diamicton, representing proximal glacimarine sediments. The lower Pliocene section also contains many ice-rafted pebbles but is dominated by sandy units rather than diamicton and is interpreted to represent a current-winnowed deposit, similar to the modern contour current-influenced sediments of the region.

Physical properties, sedimentation rates, and accumulation rates of bottom sediments from the Laptev Sea collected during SPASIBA-91 Russian-French Program

Humidity and wet and dry bulk densities were determined for bottom sediments of the Lena River marginal filter within a 700 km section from the outer boundary of the river delta. Earlier determinations of suspended matter concentration in water, material and grain-size composition and age of sediments were made along the same section. Sediment matter fluxes (accumulation rates), their changes in space and time (about 14 ka) were inferred from measurements of physical parameters. A correlation was found between the physical parameters of bottom sediments and changes in the Lena river marginal filter including those caused by sea-level fluctuations.

Eolian deposition on the Ontong Java Plateau

The record of eolian deposition on the Ontong Java Plateau (OJP) since the Oligocene (approximately 33 Ma) has been investigated using dust grain size, dust flux, and dust mineralogy, with the goal of interpreting the paleoclimatology and paleometeorology of the western equatorial Pacific. Studies of modern dust dispersal in the Pacific have indicated that the equatorial regions receive contributions from both the Northern Hemisphere westerly winds and the equatorial easterlies; limited meteorological data suggest that low-altitude westerlies could also transport dust to OJP from proximal sources in the western Pacific. Previous studies have established the characteristics of the grain-size, flux, and mineralogy records of dust deposited in the North Pacific by the mid-latitude westerlies and in the eastern equatorial Pacific by the low-latitude easterlies since the Oligocene. By comparing the OJP records with the well-defined records of the mid-latitude westerlies and the low-latitude easterlies, the importance of multiple sources of dust to OJP can be recognized. OJP dust is composed of quartz, illite, kaolinite/chlorite, plagioclase feldspar, smectite, and heulandite. Mineral abundance profiles and principal components analysis (PCA) of the mineral abundance data have been used to identify assemblages of minerals that covary through all or part of the OJP record. Abundances of quartz, illite, and kaolinite/chlorite covary throughout the interval studied, defining a mineralogical assemblage supplied from Asia. Some plagioclase and smectite were also supplied as part of this assemblage during the late Miocene and Pliocene/Pleistocene, but other source areas have supplied significant amounts of plagioclase, smectite, and heulandite to OJP since the Oligocene. OJP dust is generally coarser than dust deposited by the Northern Hemisphere westerlies or the equatorial easterlies, and it accumulates more rapidly by 1-2 orders of magnitude. These relationships indicate the importance of the local sources on dust deposition at OJP. The grain-size and flux records of OJP dust do not exhibit most of the events observed in the corresponding records of the Northern Hemisphere westerlies or the equatorial easterlies, because these features are masked by the mixing of dust from several sources at OJP. The abundance record of the Asian dust assemblage at OJP, however, does contain most of the features characteristic of dust flux by means of the Northern Hemisphere westerlies, indicating that the paleoclimatic and paleometeorologic signal of a particular source area and wind system can be preserved in areas well beyond the region dominated by that source and those winds. Identifying such a signal requires "unmixing" the various dust assemblages, which can be accomplished by combining grain-size, flux, and mineralogic data.