Calcareous nannofossil biostratigraphy of ODP Hole 108-667A and DSDP Site 85-574

Detailed quantitative analyses of selected calcareous nannofossil species were used to determine the placement of zonal boundaries. In Hole 667A in the equatorial Atlantic Ocean, Zones CP19 through CN5 were recognized, whereas at Site 574 in the equatorial Pacific Ocean, only the CN4/CN5 boundary could be determined. Boundaries were identified by sharp rises and declines in abundance at the beginnings and ends, respectively, of index fossil ranges. The sharp rise in abundance at the beginning of the range of Triquetrorhabdulus rugosus provided a good datum level in both regions; the same is true for the sharp decline in abundance at the end of the range of Cyclicargolithus floridanus. The last occurrence of Helicosphaera ampliaperta was used to mark the CN3/CN4 boundary in Hole 667A, while at Site 574, H. ampliaperta was absent. The abundance pattern of Triquetrorhabdulus carinatus obtained from Hole 667A makes it impossible to observe a distinct disappearance level. Age/depth plots reveal uniform sedimentation rates at both sites during early Miocene times. At Site 667 in the Atlantic the mean sedimentation rate was 14.90 m/m.y., and at Site 574 in the Pacific it was 16.17 m/m.y. during this same period. One new nannofossil species, Triquetrorhabdulus rioensis, is described; and one species, Triquetrorhabdulus serratus, is recombined.

(Table 1) Major and trace elements analyses from FAMOUS-Project and DSDP Site 54-424

Hydrothermal deposits "sensu stricto" have been recovered during the FAMOUS cruise and Leg 54 of the Deep Sea Drilling Project near the Galapagos Spreading Centre. The studied sediments, mainly composed of clay material, have very poor REE concentrations, below about ten ppm. The shale-normalized patterns are characterized by a significant enrichment in heavy rare earths and show a negative Ce anomaly. The magnitude of this anomaly fluctuates but is generally lower than the seawater Ce anomaly. The geochemical characteristics of these hydrothermal deposits are in contrast with those of metalliferous sediments which are more enriched in trace elements, especially in REE.

Table 2: Water stable isotope results and sampling site information of samples taken between 2003 and 2009 on the island of Corsica (western Mediterranean)

The Mediterranean is regarded as a region of intense climate change. To better understand future climate change, this area has been the target of several palaeoclimate studies which also studied stable isotope proxies that are directly linked to the stable isotope composition of water, such as tree rings, tooth enamel or speleothems. For such work, it is also essential to establish an isotope hydrology framework of the region of interest. Surface waters from streams and lakes as well as groundwater from springs on the island of Corsica were sampled between 2003 and 2009 for their oxygen and hydrogen isotope compositions. Isotope values from lake waters were enriched in heavier isotopes and define a local evaporation line (LEL). On the other hand, stream and spring waters reflect the isotope composition of local precipitation in the catchment. The intersection of the LEL and the linear fit of the spring and stream waters reflect the mean isotope composition of the annual precipitation (dP) with values of -8.6(±0.2) per mil for d18O and -58(±2) per mil for d2H. This value is also a good indicator of the average isotope composition of the local groundwater in the island. Surface water samples reflect the altitude isotope effect with a value of -0.17(±0.02) per mil per 100 m elevation for oxygen isotopes. At Vizzavona Pass in central Corsica, water samples from two catchments within a lateral distance of only a few hundred metres showed unexpected but systematic differences in their stable isotope composition. At this specific location, the direction of exposure seems to be an important factor. The differences were likely caused by isotopic enrichment during recharge in warm weather conditions in south-exposed valley flanks compared to the opposite, north-exposed valley flanks.

(Table 1) Age comparison between the GPTS and ODP Site 181-1123 age model for each chron base within the Middle Miocene section

Today the deep western boundary current (DWBC) east of New Zealand is the most important route for deep water entering the Pacific Ocean. Large-scale changes in deep water circulation patterns are thought to have been associated with the development of the East Antarctic Ice Sheet (EAIS) close to the main source of bottom water for the DWBC. Here we reconstruct the changing speed of the southwest Pacific DWBC during the middle Miocene from ~15.5-12.5 Ma, a period of significant global ice accumulation associated with EAIS growth. Sortable silt mean grain sizes from Ocean Drilling Program Site 1123 reveal variability in the speed of the Pacific inflow on the timescale of the 41 kyr orbital obliquity cycle. Similar orbital period flow changes have recently been demonstrated for the Pleistocene epoch. Collectively, these observations suggest that a strong coupling between changes in the speed of the deep Pacific inflow and high-latitude climate forcing may have been a persistent feature of the global thermohaline circulation system for at least the past 15 Myr. Furthermore, long-term changes in flow speed suggest an intensification of the DWBC under an inferred increase in Southern Component Water production. This occurred at the same time as decreasing Tethyan outflow and major EAIS growth between ~15.5 and 13.5 Ma. These results provide evidence that a major component of the deep thermohaline circulation was associated with the middle Miocene growth of the EAIS and support the view that this time interval represents an important step in the development of the Neogene icehouse climate.

Chemistry of smectite and volcanic glass of ODP Site 159-959

The Ocean Drilling Program (ODP) Site 959 was drilled in the northern border of the Côte d'Ivoire-Ghana Ridge at a water depth of 2100 m. Pleistocene total thickness does not exceed 20 m. Winnowing processes resulted in a low accumulation rate and notable stratigraphic hiatuses. During the Late Pleistocene, bottom circulation was very active and controlled laminae deposition (contourites) which increased the concentration of glauconitic infillings of foraminifera, and of volcanic glass and blue-green grains more rarely, with one or several subordinate ferromagnesian silicates. Volcanic glass generally was X-ray amorphous and schematically classified as basic to intermediate (44-60% SiO2). Opal-A or opal-CT suggested the beginning of the palagonitisation process, and previous smectitic deposits may have been eroded mechanically. The blue-green grains presented two main types of mineralogic composition: (1) neoformed K, Fe-smectite associated with zeolite (like phillipsite) and unequal amounts of quartz and anorthite; (2) feldspathic grains dominated by albite but including quartz, volcanic glass and smectites as accessory components. They were more or less associated with the volcanic glass. On the basis of their chemical composition, the genetic relationship between the blue-green grains and the volcanic glass seemed to be obvious although some heterogeneous grains seemed to be primary ignimbrite and not the result of glass weathering. The most reasonable origin of these pyroclastic ejecta would be explosive events from the Cameroon Volcanic Ridge, especially from the Sao Thome and Principe Islands and Mount Cameroon area. This is supported both by grain geochemistry and the time of volcanic activity, i.e. Pleistocene. After westward wind transport (some 1200 km) and ash fall-out, the subsequent winnowing by bottom currents controlled the concentration of the volcanic grains previously disseminated inside the hemipelagic sediment. Palagonitisation, and especially phillipsite formation, may result from a relatively rapid reaction during burial diagenesis (<1 m.y.), in deep-sea deposits at relatively low sedimentation rate. However, it cannot be excluded that the weathering had begun widely on the Cameroon Ridge before the explosive event.

Vegetation, soil and site characteristics of samples taken along the Yamal Transet in 2007-2008

The overarching goal of the Yamal portion of the Greening of the Arctic project is to examine how the terrain and anthropogenic factors of reindeer herding and resource development combined with the climate variations on the Yamal Peninsula affect the spatial and temporal patterns of vegetation change and how these changes are in turn affecting traditional herding of the indigenous people of the region. The purpose of the expeditions was to collect groundobservations in support of remote sensing studies at four locations along a transect that traverses all the major bioclimate subzones of the Yamal Peninsula. This data report is a summary of information collected during the 2007 and 2008 expeditions. It includes all the information from the 2008 data report (Walker et al. 2008) plus new information collected at Kharasavey in Aug 2008. The locations included in this report are Nadym (northern taiga subzone), Laborovaya (southern tundra = subzone E of the Circumpolar Arctic Vegetation Map (CAVM), Vaskiny Dachi (southern typical tundra = subzone D), and Kharasavey (northern typical tundra = subzone C). Another expedition is planned for summer 2009 to the northernmost site at Belyy Ostrov (Arctic tundra = subzone B). Data are reported from 10 study sites - 2 at Nadym, 2 at Laborovaya, and 3 at Vaskiny Dachi and 3 at Kharasavey. The sites are representative of the zonal soils and vegetation, but also include variation related to substrate (clayey vs. sandy soils). Most of the information was collected along 5 transects at each sample site, 5 permanent vegetation study plots, and 1-2 soil pits at each site. The expedition also established soil and permafrost monitoring sites at each location. This data report includes: (1) background for the project, (2) general descriptions and photographs of each locality and sample site, (3) maps of the sites, study plots, and transects at each location, (4) summary of sampling methods used, (5) tabular summaries of the vegetation data (species lists, estimates of cover abundance for each species within vegetation plots, measured percent ground cover of species along transects, site factors for each study plot), (6) summaries of the Normalized Difference Vegetation Index (NDVI) and leaf area index (LAI) along each transect, (7) soil descriptions and photos of the soil pits at each study site, (8) summaries of thaw measurements along each transect, and (9) contact information for each of the participants. One of the primary objectives was to provide the Russian partners with full documentation of the methods so that Russian observers in future years could repeat the observations independently.

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.

Isotopic composition of igneous rocks from DSDP Site 462

The tholeiitic basalts and microdolerites that comprise the Cretaceous igneous complex in the Nauru Basin in the western equatorial Pacific have moderate ranges in initial 87Sr/86Sr (0.70347 - 0.70356), initial 143Nd/144Nd (0.51278 - 0.51287), and measured 206Pb/204Pb (18.52 - 19.15), 207Pb/204Pb (15.48 - 15.66) and 208Pb/204Pb (38.28 - 38.81). These isotopic ratios overlap with those of both oceanic island basalts (OIB) and South Atlantic and Indian mid-ocean ridge basalts (MORB). However, the petrography, mineralogy, and bulk rock chemistry of the igneous complex are more similar to MORB than to OIB. Also, the rare earth element contents of Nauru Basin igneous rocks are uniformly depleted in light elements (La/Sm(ch) < 1) indicative of a mantle source compositionally similar to that of MORB. These results suggest that the igneous complex is the top of the original ocean crust in the Nauru Basin, and that the notion that the crust must be 15 to 35 m.y. older based on simple extrapolation and identification of the M-sequence magnetic lineations (Larson et al., 1981, doi:10.2973/dsdp.proc.61.1981; Moberly et al., 1985, doi:10.2973/dsdp.proc.81.1984) may be invalid because of a more complicated tectonic setting. The igneous complex most probably was extruded from an ocean ridge system located near the anomalously hot, volcanically active, and isotopically distinct region in the south central Pacific which has been in existence since c. 120 Ma.

Chemistry of interstitial waters and sediments at DSDP Leg 64 Holes

Studies of interstitial waters obtained from DSDP Leg 64 drill sites in the Gulf of California have revealed information both on early diagenetic processes in the sediments resulting from the breakdown of organic matter and on hydrothermal interactions between sediments and hot doleritic sill intrusions into the sediments. In all the sites drilled sulfate reduction occurred as a result of rapid sediment accumulation rates and of relatively high organic carbon contents; in most sites methane production occurred after sulfate depletion. Associated with this methane production are high values of alkalinity and high concentrations of dissolved ammonia, which causes ion exchange processes with the solid phases leading to intermediate maxima in Mg++, K+, Rb+, and Sr++(?). Though this phenomenon is common in Leg 64 drill sites, these concentration reversals had been noticed previously only in Site 262 (Timor Trough) and Site 440 (Japan Trench). Penetrating, hot dolerite sills have led to substantial hydrothermal alteration in sediments at sites drilled in the Guaymas Basin. Site 477 is an active hydrothermal system in which the pore-water chemistry typically shows depletions in sulfate and magnesium and large increases in lithium, potassium, rubidium, calcium, strontium, and chloride. Strontium isotope data also indicate large contributions of volcanic matter and basalt to the pore-water strontium concentrations. At Sites 478 and 481 dolerite sill intrusions have cooled to ambient temperatures but interstitial water concentrations of Li+, Rb+, Sr++ , and Cl- show the gradual decay of a hydrothermal signal that must have been similar to the interstitial water chemistry at Site 477 at the time of sill intrusion. Studies of oxygen isotopes of the interstitial waters at Site 481 indicate positive values of d18O (SMOW) as a result of high-temperature alteration reactions occurring in the sills and the surrounding sediments. A minimum in dissolved chloride at about 100-125 meters sub-bottom at Sites 478, 481, and particularly Site 479 records a possible paleosalinity signal, associated with an event that substantially lowered salinities in the inner parts of the Gulf of California during Quaternary time.

Chemical composition and elemental oxide ratios to AI2O3 of bulk solids at DSDP Leg 64 Holes

Analyses of sediments from Leg 64 sites reveal a diverse and in one case unique geochemistry. Sites are characterized by high heat flow along an active, divergent plate boundary, or rapid accumulation of diatom muds, or both. The geochemical trends of Sites 474-476 at the tip of Baja California reflect changes4n the percentages of sedimentary components - particularly biogenous matter and mineralogy - that support interpretations of sedimentary environments inferred to be present since the commencement of subsidence along this young, passive continental margin. The sediments below dolerite sills in Holes 477, 477A, 478, and 481 show major mineralogic and chemical deviations from "average" hemipelagic sediments. The sills appear to have two functions: (1) they allow hydrothermal circulation and metamorphism in a partially closed system by trapping heat and fluids emanating from below, and (2) they expel heated interstitial fluids at the moment of intrusion and mobilize elements, most likely leading to the formation of metalliferous deposits along the surface traces of normal faults in the basin. The hydrothermal system as a whole appears to be localized and ephemeral, as is indicated by the lack of similar geochemical trends and high heat flow at Sites 478 and 481. Site 479 illustrates sedimentation in an oxygen-minimum zone with anoxic sediments and concomitant geochemical trends, especially for MnO. With few exceptions, geochemical trends are remarkably constant with depth, suggesting that Site 479 can serve as an "internal" standard or average sediment against which the magnitude of hydrothermal alteration at the basinal Sites 477, 478, and 481 can be measured.

Characteristics and radiocarbon ages of four retrogressive thaw slumps on Herschel Island and King Point

Four retrogressive thaw slumps (RTS) located on Herschel Island and the Yukon coast (King Point) in the western Canadian Arctic were investigated to compare the environmental, sedimentological and geochemical setting and characteristics of zones in active and stabilised slumps and at undisturbed sites. In general, the slope, sedimentology and biogeochemistry of stabilised and undisturbed zones differ, independent of their age or location. Organic carbon contents were lower in slumps than in the surrounding tundra, and the density and compaction of slump sediments were much greater. Radiocarbon dating showed that RTS were likely to have been active around 300 a BP and are undergoing a similar period of increased activity now. This cycle is thought to be controlled more by local geometry, cryostratigraphy and the rate of coastal erosion than by variation in summer temperatures.

Pore water (SO4, CH4, alkalinity, HS-, Ca, Sr, Mg, Ba) and solid phase (Ca, Sr, Mg, Ba) data measured in pockmark sediments of the Northern Congo Fan

This study focuses on the vertical distribution of authigenic carbonates (aragonite and high Mg-calcite) in the form of finely disseminated precipitates as well as massive carbonate concretions present in and above gas hydrate bearing sediments of the Northern Congo Fan. Analyses of Ca, Mg, Sr and Ba in pore water, bulk sediments and authigenic carbonates were carried out on gravity cores taken from three pockmark structures (Hydrate Hole, Black Hole and Worm Hole). In addition, a background core was retrieved from an area not influenced by fluid seepage. Pore water Sr/Ca and Mg/Ca ratios are used to reveal the current depths of carbonate formation as well as the mineralogy of the authigenic precipitates. The Sr/Ca and Mg/Ca ratios of bulk sediments and massive carbonate concretions were applied to infer the presence and depth distribution of authigenic aragonite and high Mg-calcite, based on the approach presented by Bayon et al. [Bayon et al. (2007). Sr/Ca and Mg/Ca ratios in Niger Delta sediments: Implications for authigenic carbonate genesis in cold seep environments. Marine Geology 241(1-4), 93-109, doi:10.1016/j.margeo.2007.03.007]. We show that the approach developed by Bayon et al. (2007) for sediments of cold seeps of the Niger Delta is also suitable to identify the mineralogy of authigenic carbonates in pockmark sediments of the Congo Deep-Sea Fan. We expand this approach by combining interstitial with solid phase Sr/Ca and Mg/Ca ratios, which demonstrate that high Mg-calcite is the predominant authigenic carbonate that currently forms at the sulfate/methane reaction zone (SMRZ). This is the first study which investigates both solid phase and pore water signatures typical for either aragonite or high Mg-calcite precipitation for the same sediment cores and thus is able to identify active and fossil carbonate precipitation events. At all investigated pockmark sites fossil horizons of the SMRZ were deduced from high Mg-calcite located above and below the current depths of the SMRZ. Additionally, aragonite enrichments typical for high seepage rates were detected close to the sediment surface at these sites. However, active precipitation of aragonite as indicated by pore water characteristics only occurs at the Black Hole site. Dissolved and solid phase Ba concentrations were used to estimate the time the SMRZ was fixed at the current depths of the diagenetic barite fronts. The combined pore water and solid phase elemental ratios (Mg/Ca, Sr/Ca) and Ba concentrations allow the reconstruction of past changes in methane seepage at the investigated pockmark sites. At the Hydrate Hole and Worm Hole sites the time of high methane seepage was estimated to have ceased at least 600 yr BP. In contrast, a more recent change from a high flux to a more dormant stage must have occurred at the Black Hole site as evidenced by active aragonite precipitation at the sediment surface and a lack of diagenetic Ba enrichments.

Mineral, chemical and isotopic compositions of altered rocks at ODP Sites 193-1188 and 193-1189

During ODP Leg 193, 4 sites were drilled in the active PACMANUS hydrothermal field on the crest of the felsic Pual Ridge to examine the vertical and lateral variations in mineralization and alteration patterns. We present new data on clay mineral assemblages, clay and whole rock chemistry and clay mineral strontium and oxygen isotopic compositions of altered rocks from a site of diffuse low-temperature venting (Snowcap, Site 1188) and a site of high-temperature venting (Roman Ruins, Site 1189) in order to investigate the water-rock reactions and associated elemental exchanges. The volcanic succession at Snowcap has been hydrothermally altered, producing five alteration zones: (1) chlorite+/-illite-cristobalite-plagioclase alteration apparently overprinted locally by pyrophyllite bleaching at temperatures of 260-310°C; (2) chlorite+/-mixed-layer clay alteration at temperatures of 230°C; (3) chlorite and illite alteration; (4) illite and chlorite+/-illite mixed-layer alteration at temperatures of 250-260°C; and (5) illite+/-chlorite alteration at 290-300°C. Felsic rocks recovered from two holes (1189A and 1189B) at Roman Ruins, although very close together, show differing alteration features. Hole 1189A is characterized by a uniform chlorite-illite alteration formed at ~250°C, overprinted by quartz veining at 350°C. In contrast, four alteration zones occur in Hole 1189B: (1) illite+/-chlorite alteration formed at ~300°C; (2) chlorite+/-illite alteration at 235°C; (3) chlorite+/-illite and mixed layer clay alteration; and (4) chlorite+/-illite alteration at 220°C. Mass balance calculations indicate that the chloritization, illitization and bleaching (silica-pyrophyllite assemblages) alteration stages are accompanied by different chemical changes relative to a calculated pristine precursor lava. The element Cr appears to have a general enrichment in the altered samples from PACMANUS. The clay concentrate data show that Cr and Cu are predominantly present in the pyrophyllites. Illite shows a significant enrichment for Cs and Cu relative to the bulk altered samples. Considerations of mineral stability allow us to place some constraints on fluid chemistry. Hydrothermal fluid pH for the chloritization and illitization was neutral to slightly acidic and relatively acidic for the pyrophyllite alteration. In general the fluids, especially from Roman Ruins and at intermediate depths below Snowcap, show only a small proportion of seawater mixing (<10%). Fluids in shallow and deep parts of the Snowcap holes, in contrast, show stronger seawater influence.