Dissolved lithium and silicon through time in microbial dissolution experiments on ODP Leg 209 peridotite

Using peridotite drilled during Ocean Drilling Program Leg 209, a series of enrichment cultures were initiated on board the ship to stimulate microbially enhanced dissolution of olivine. Dissolution was estimated by measured changes in dissolved Li and Si in the media through time (up to 709 days). The results suggest that there was no significant difference between the amounts of dissolved Li and Si in most of the inoculated microbial cultures compared to the control cultures. Alternative explanations for this are that 1. No microbes are living in the culture tubes that can affect the dissolution rates of olivine, 2. The control cultures have microbes effecting the dissolution of olivine as well as the inoculated cultures, 3. Not enough time has passed to build up a large enough microbial population to effect the dissolution of the olivine in the culture tubes, 4. Microbes act to suppress dissolution of olivine instead of enhancing dissolution, and 5. Abiotic dissolution overshadows microbially enhanced dissolution. Further work is required to test these alternatives.

Experiment: Competition between calcifying and noncalcifying temperate marine macroalgae under elevated CO2 levels

Since pre-industrial times, uptake of anthropogenic CO2 by surface ocean waters has caused a documented change of 0.1 pH units. Calcifying organisms are sensitive to elevated CO2 concentrations due to their calcium carbonate skeletons. In temperate rocky intertidal environments, calcifying and noncalcifying macroalgae make up diverse benthic photoautotrophic communities. These communities may change as calcifiers and noncalcifiers respond differently to rising CO2 concentrations. In order to test this hypothesis, we conducted an 86?d mesocosm experiment to investigate the physiological and competitive responses of calcifying and noncalcifying temperate marine macroalgae to 385, 665, and 1486 µatm CO2. We focused on comparing 2 abundant red algae in the Northeast Atlantic: Corallina officinalis (calcifying) and Chondrus crispus (noncalcifying). We found an interactive effect of CO2 concentration and exposure time on growth rates of C. officinalis, and total protein and carbohydrate concentrations in both species. Photosynthetic rates did not show a strong response. Calcification in C. officinalis showed a parabolic response, while skeletal inorganic carbon decreased with increasing CO2. Community structure changed, as Chondrus crispus cover increased in all treatments, while C. officinalis cover decreased in both elevated-CO2 treatments. Photochemical parameters of other species are also presented. Our results suggest that CO2 will alter the competitive strengths of calcifying and noncalcifying temperate benthic macroalgae, resulting in different community structures, unless these species are able to adapt at a rate similar to or faster than the current rate of increasing sea-surface CO2 concentrations.

Stable carbon and oxygen isotope record of foraminifera from DSDP Hole 30-289

Sediments accumulate on the sea floor far from land with rates of a few millimetres to a few centimetres per thousand years. Sediments have been accumulating under broadly similar conditions, subject to similar controls, for the past 10 8 years and more. In principle we should be able to study the distribution of climatic variance with frequencies over the range 10**-3 to 10**-7 cycles per year with comparative ease. In fact, nearly all our data are heavily weighted towards the youngest part of the geological record. We study frequencies higher than 10**-4 cycles per year in the special case of a Pleistocene interglacial (the present one), and frequencies in the range 10**-4 to 10**-5 cycles per year in the special case of an ice-age. Although these may be of more direct interest to mankind than earlier periods, it may well be that we will understand the causes of climatic variability better if we can examine their operation over a longer time scale and under different boundary conditions. Rather than review the available data, I have collected some new data to show the feasibility of gathering a data base for examining climatic variability without this usual bias toward the recent. The most widely applicable tool for extracting climatic information from deep-sea sediments is oxygen isotope analysis of calcium carbonate microfossils. It is generally possible to select from the sediment both specimens of benthonic Foraminifera (that is, those that lived in ocean deep water at the sediment-water interface) and specimens of planktonic Foraminifera (that is, those that lived and formed their shells near the ocean surface, and fell to the sediment after death). Thus one is able to monitor conditions at the surface and at depth at simultaneous moments in the geological past. The necessity to analyse calcareous microfossils restricts investigation to calcareous sediments, but even with this restriction in sediment type there are many factors governing the rate of sediment accumulation. On a global scale, sediment accumulates so as to balance the input to the oceans from continental erosion. Even when averaged globally, long-term accumulation rates have varied by almost a factor of ten (Davies et al., 1977, doi:10.1126/science.197.4298.53). At the regional scale, surface productivity and deep-water physical and chemical conditions also affect the sediment accumulation rate. Since all these are susceptible to variation and may well vary in response to climatic change as well as other factors, it is extremely hazardous to attempt to express any climatic variable as a function of time on the basis of measurements originally made as a function of depth in sediment. Although time has been used as a basis for plotting Figs. i-8, these should be regarded as freehand sketches of climatic history rather than as time-series plots.

Geochemistry, clay mineralogy and grain size distribution in various sediment cores drilled during ODP Leg 119 on the Antarctic continental shelf off Prydz Bay

Drilling was undertaken at five sites (739-743) on ODP Leg 119 on a transect across the continental shelf of Prydz Bay, East Antarctica, to elucidate the long-term glacial history of the area and to examine the importance of the area with respect to the development of the East Antarctic ice sheet as a whole. In addition to providing a record of glaciation spanning 36 m.y. or more, Leg 119 has provided information concerning the development of a continental margin under the prolonged influence of a major ice sheet. This has allowed the development of a sedimentary model that may be applicable not only to other parts of the Antarctic continental margin, but also to northern high-latitude continental shelves. The cored glacial sedimentary record in Prydz Bay consists of three major sequences, dominated by diamictite: 1. An upper flat-lying sequence that ranges in thickness from a few meters in inner and western Prydz Bay to nearly 250 m in the outer or eastern parts of the bay. The uppermost few meters consist of Holocene diatom ooze and diatomaceous mud with a minor ice-rafted component overlying diamicton and diamictite of late Miocene to Quaternary age. The diamictite is mainly massive, but stratified varieties and minor mudstone and diatomite also occur. 2. An upper prograding sequence cored at Sites 739 and 743, unconformly below the flat-lying sequence. This consists of a relatively steep (4° inclination) prograding wedge with a number of discrete sedimentary packages. At Sites 739 and 743 the sequence is dominated by massive and stratified diamictite, some of which shows evidence of slumping and minor debris flowage. 3. A lower, more gently inclined, prograding sequence lies unconformably below the flat-lying sequence at Site 742 and the upper prograding sequence at Site 739. This extends to the base of both sites, to 316 and 487 mbsf, respectively. It is dominated by massive, relatively clast-poor diamictite which is kaolinite-rich, light in color, and contains sporadic carbonate-cemented layers. The lower part of Site 742 includes well-stratified diamictites and very poorly sorted mudstones. The base of this site has indications of large-scale soft-sediment deformation and probably represents proximity to the base of the glacial sequence. Facies analysis of the Prydz Bay glacial sequence indicates a range of depositional environments. Massive diamictite is interpreted largely as waterlain till, deposited close to the grounding line of a floating glacier margin, although basal till and debris flow facies are also present. Weakly stratified diamictite is interpreted as having formed close to or under the floating ice margin and influenced by the input of marine diatomaceous sediment (proximal glaciomarine setting). Well-stratified diamictite has a stronger marine input, being more diatom-rich, and probably represents a proximal-distal glaciomarine sediment with the glaciogenic component being supplied by icebergs. Other facies include a variety of mudstones and diatom-rich sediments of marine origin, in which an ice-rafted component is still significant. None of the recovered sediments are devoid of a glacial influence. The overall depositional setting of the prograding sequence is one in which the grounded ice margin is situated close to the shelf edge. Progradation was achieved primarily by deposition of waterlain till. The flat-lying sequence illustrates a complex sequence of advances and retreats across the outer part of the shelf, with intermittent phases of ice loading and erosion. The glacial chronology is based largely on diatom stratigraphy, which has limited resolution. It appears that ice reached the paleoshelf break by earliest Oligocene, suggesting full-scale development of the East Antarctic ice sheet by that time. The ice sheet probably dominated the continental margin for much of Oligocene to middle Miocene time. Retreat, but not total withdrawal of the ice sheet, took place in late Miocene to mid-Pliocene time. The late Pliocene to Pleistocene was characterized by further advances across, and progradation of, the continental shelf. Holocene time has been characterized by reduced glacial conditions and a limited influence of glacial processes on sedimentation.

Calcareous nannofossils of ODP Hole 123-765C and DSDP Hole 27-261

Sediments from the Argo Abyssal Plain (AAP), northwest of Australia, are the oldest known from the Indian Ocean and were recovered from ODP Site 765 and DSDP Site 261. New biostratigraphic and sedimentologic data from these sites, as well as reinterpretations of earlier findings, indicate that basal sediments at both localities are of Late Jurassic age and delineate a history of starved sedimentation punctuated by periodic influx of calcareous pelagic turbidites. Biostratigraphy and correlation of Upper Jurassic-Lower Cretaceous sediments is based largely on calcareous nannofossils. Both sites yielded variably preserved nannofossil successions ranging from Tithonian to Hauterivian at Site 765 and Kimmeridgian to Hauterivian at Site 261. The nannofloras are comparable to those present in the European and Atlantic Boreal and Tethyan areas, but display important differences that reflect biogeographic differentiation. The Argo region is thought to have occupied a position at the southern limit of the Tethyan nannofloral realm, thus yielding both Tethyan and Austral biogeographic features. Sedimentary successions at the two sites are grossly similar, and differences largely reflect Site 765's greater proximity to the continental margin. Jurassic sediments were deposited at rates of about 2 m/m.y. near the carbonate compensation depth (CCD) and contain winnowed concentrations of inoceramid prisms and nannofossils, redeposited layers rich in calcispheres and calcisphere debris, manganese nodules, and volcanic detritus. Lower Cretaceous and all younger sediments accumulated below the CCD at rates that were highest (about 20 m/m.y.) during mid-Cretaceous and Neogene time. Background sediment in this interval is noncalcareous claystone; turbidites dominate the sequence and are thicker and coarser grained at Site 765. AAP turbidites consist mostly of calcareous and siliceous biogenic components and volcanogenic smectite clay; they were derived from relatively deep parts of the continental margin that lay below the photic zone, but above the CCD. The Jurassic-Lower Cretaceous section is about the same thickness across the AAP; turbidites in this interval appear to have had multiple sources along the Australian margin. The Upper Cretaceous-Cenozoic section, however, is three times thicker at Site 765 than at Site 261; turbidites in this interval were derived predominantly from the south. Patterns of sedimentation across the AAP have been influenced by shifts in sea level, the CCD, and configuration of the continental margin. Major pulses of calcareous turbidite deposition occurred during Valanginian, Aptian, and Neogene time-all periods of eustatic lowstands and depressed CCD levels. Sediment redeposited on the AAP has come largely from the Australian outer shelf, continental slope, or rise, rather than the continent itself. Most terrigenous detritus was trapped in epicontinental basins that have flanked northwestern Australia since the early Mesozoic.

Cretaceous planktonic foraminifera of the Kerguelen Plateau

An almost complete Upper Cretaceous sedimentary sequence recently recovered on the Kerguelen Plateau (southern Indian Ocean) during ODP Leg 183 was analysed for planktonic foraminifera in order to refine and integrate the zonal schemes previously proposed for the Southern Ocean area. Detailed biostratigraphic analysis carried out on holes 1135A, 1136A and 1138A (poleward of 50°S palaeolatitude during Late Cretaceous time) has allowed recognition of low and mid-high latitude bioevents, useful for correlation across latitudes, in addition to known Austral bioevents. The low latitude biozonation can be applied to Turonian sediments, because of the occurrence of Helvetoglobotruncana helvetica, which marks the boundary between Whiteinella archaeocretacea and Helvetoglobotruncana helvetica zones. The base of the Whiteinella archeocretacea Zone falls within the uppermost Cenomanian-Turonian black shale level in Hole 1138A. The stratigraphic interval from upper Turonian to uppermost Santonian can be resolved using bioevents recognized in the mid-high latitude sections. They are, in stratigraphic order: the last occurrence of Falsotruncana maslakovae in the Coniacian, the first occurrence of Heterohelix papula at the Coniacian/Santonian boundary, the extinction of the marginotruncanids in the late Santonian, and the first occurrence of Globigerinelloides impensus in the latest (?) Santonian. The remainder of the Late Cretaceous fits rather well in the Austral zonal scheme, except that Globigerinelloides impensus exhibits a stratigraphic range in agreement with its record at the mid-high latitude sections and extends further downwards than previously recorded at southern sites. Therefore, despite the poor recovery in certain intervals and the presence of several hiatuses of local and regional importance as revealed by correlation among holes, a more detailed zonal scheme has been obtained (mainly for the less resolved Turonian-Santonian interval). Remarks on some species often overlooked in literature are also provided.

Determination of ages and fossil Coleoptera fauna from eight sites in the London region

These data sets report the fossil beetle assemblages identified from the Mesolithic to Late Bronze Age at eight sites in the London region. All but one of the study sites are within 2 km of the modern course of the Thames. The sites produced 128 faunal assemblages that yielded 218 identified species in 41 families of Coleoptera (beetles).  Beetle faunas of Mesolithic age indicate extensive wetlands near the Thames, bordered by rich deciduous woodlands. The proportion of woodland species declined in the Neolithic, apparently because of the expansion of wetlands, rather than because of human activities. The Early Bronze Age faunas contained a greater proportion of coniferous woodland and aquatic (standing water) species. An increase in the dung beetle fauna indicates the presence of sheep, cattle and horses, and various beetles associated with crop lands demonstrate the local rise of agriculture, albeit several centuries after the beginnings of farming in other regions of Britain. Late Bronze Age faunas show the continued development of agriculture and animal husbandry along the lower Thames. About 33% of the total identified beetle fauna from the London area sites have limited modern distributions or are extinct in the U.K. Some of these species are associated with the dead wood found in primeval forests; others are wetland species whose habitat has been severely reduced in recent centuries. The third group is stream-dwelling beetles that require clean, clear waters and river bottoms.

Chemical and isotopic compositions of deep-sea carbonate sediments and interstitial waters from DSDP Sites 30-288 and 30-289

Interstitial waters and sediments from DSDP sites 288 and 289 contain information on the chemistry and diagenesis of carbonate in deep-sea sediments and on the role of volcanic matter alteration processes. Sr/Ca ratios are species dependent in unaltered foraminifera from site 289 and atom ratios (0.0012-0.0016) exceed those predicted by distribution coefficent data (~0.0004). During diagenesis Sr/Ca ratios of carbonates decrease and reach the theoretical distribution at a depth which is identical to the depth of Sr isotopic equilibration, where 87Sr/86Sr ratios of interstitial waters and carbonates converge. Mg/Ca ratios in the carbonates do not increase with depth as found in some other DSDP sites, possibly because of diagenetic re-equilibration with interstitial waters showing decreasing Mg(2+)/Ca(2+) ratios with depth due to Ca input and Mg removal by alteration of volcanic matter. Interstitial 18O/16O ratios increase with depth at site 289 to d18O = 0.67? (SMOW), reflecting carbonate recrystallization at elevated temperatures (>/= 20°C), the first recorded evidence of this effect in interstitial waters. Interstitial Sr2+ concentrations reach high levels, up to 1 mM, chiefly because of carbonate recrystallization. However, 87Sr/86Sr ratios decrease from 0.7092 to less than 0.7078, lower than for contemporaneous sea water, showing that there is a volcanic input of strontium at depth. This volcanic component is recorded in the Sr isotopic composition of recrystallized calcites. Isotopic compositions of the unrecrystallized calcites suggests that the rate of increase of the 87Sr/86Sr ratio of sea water with time has been faster since 3 my ago than in the preceding 13 my.

Chemistry of Late Quaternary sediments and their interstitial waters of sediment cores from the Nort-West African continental margin

In the sediments of the NW African continental margin the mainly biogenic carbonate constituents become increasingly diluted with terrigenous material as one approaches the coast, as indicated by the carbonate-CO2 content, the Al2O3/SiO2-ratios, and the presence of ammonia fixed to alumino-silicates, predominantly to illites. In the norther area of the investigation - off Cape Blanc and Cape Bojador . the terrigenous constituents are mainly quartz from the Sahara Desert, whereas in the south - off Senegal - more alumino-silicates as clay minerals are admixed with the carbonate constituents. The organic carbon content of the continental slope sediments off Senegal is higher than in samples of the continental rise or of the preservation of organic matter as a result of high production and relatively rapid sedimentation. The zone of manganese-oxide enrichment follows the redox potential of + 330 mV from the surface (0-5 cm) into the sediments (20-30 cm deep) at 2000--3000 m and 3700 m of water depths, respectively. At shallower water depths, low redox potentials preclude deposition of manganese oxides and cause their mobilization from the sediments. About 1/3 of the total sedimentary Zn and 1/4 of the Cu is associated with the carbonate mineral fraction, probably in calcium phosphate overgrowths as a result of the mineralization of phosphorus-containing organic matter. Besides the precipitation of calcium phosphate, the mineralization of organic matter mediated by bacterial sulfate reduction also results in calcium carbonate precipitation and the exchange of ammonia for potassium on illites. Because of these simultaneous reactions, the depth distribution of all mineralization constituents in the interstitial water can be determined using the actual molar carbon-to-nitrogen-to phosphorus ratios of the sedimentary organic matter. The amount of sulfide sulfur in this process indicates the predominance of bacterial sulfate reduction in the sediments off NW Africa. This process also preferentially decomposes nitrogen- and phosphorus-containing organic compounds so organic matter deficient in these elements is characteristic for the rapidly accumulating sediments than today, indicating there was increased production of organic carbon compounds and more favorable conditions of their preservations. During the last interglacial times conditions were similar to those to today. This differentiation with time has also been observed in sediments from the Argentine Basin and from slope off South India indicating perhaps world-wide environmental changes throughout Late Quaternary times.