Danian calcareous nannofossils in ODP Hole 119-738C

An apparently complete Danian section was recovered at ODP Site 738 on the southern Kerguelen Plateau. Calcareous nannofossils are abundant and moderately preserved in the section. A number of taxa common in middle or low latitudes, such as Braarudosphaera, Biscutum? romeinii, Biscutum? parvulum, Cyclagelosphaera, Octolithus multiplus, and Toweius petalosus are absent at Site 738. On the other hand, a bloom of Hornibrookina occurs at Site 738 only slightly (15 cm) above the Cretaceous/Tertiary boundary as defined by the iridium peak. Species of Chiasmolithus and Prinsius are very abundant. This gives the nannofossil assemblages distinct high-latitude characteristics and suggests significant latitudinal thermal gradients in the Danian oceans. A Danian nannofossil zonation for the Antarctic region is proposed, which utilizes traditional markers and several nontraditional markers, i.e., the first occurrences of Hornibrookina, Prinsius martinii, and Chiasmolithus bidens, and the last occurrence of Hornibrookina teuriensis. Quantitative analyses of the calcareous nannofossil assemblages from Site 738 reveal four steps of rapid floral changes in the early Danian before relatively stable nannofloral conditions were reached at about 63.8 Ma.

Automated composite depth scale reconstruction of ODP Leg 138 and 154 sites

A composite section, which reconstructs a continuous stratigraphic record from cores of multiple nearby holes, and its associated composite depth scale are important tools for analyzing sediment recovered from a drilling site. However, the standard technique for creating composite depth scales on drilling cruises does not correct for depth distortion within each core. Additionally, the splicing technique used to create composite sections often results in a 10-15% offset between composite depths and measured drill depths. We present a new automated compositing technique that better aligns stratigraphy across holes, corrects depth offsets, and could be performed aboard ship. By analyzing 618 cores from seven Ocean Drilling Program (ODP) sites, we estimate that ?80% of the depth offset in traditional composite depth scales results from core extension during drilling and extraction. Average rates of extension are 12.4 ± 1.5% for calcareous and siliceous cores from ODP Leg 138 and 8.1 ± 1.1% for calcareous and clay-rich cores from ODP Leg 154. Also, average extension decreases as a function of depth in the sediment column, suggesting that elastic rebound is not the dominant extension mechanism.

Pollen and macroremains from three sediment cores from Göttingen, Germany

In a borehole in the southern outskirts of the town of Göttingen, limnic sediments of several Pleistocene warm periods occur intercalated with coarse solifluction debris and gravel of the river Leine. Pollen analysis of the limnic sediments in a borehole at Ottostrasse gave evidence of three warm periods of interglacial character, followed by three interstadial phases. The warm phases are separated one from another by stadial phases with, at least in one case, indications of periglacial solifluction. This sequence belongs to the Brunhes magnetic epoch. The pollen data allow to exclude an Eemian or Holsteinian age of the warm period sediments. Thus a Cromerian age is assumed, though the exact position of the newly described warm periods within the ''Cromerian'' remains uncertain. A section in a borehole at Akazienweg is of Holsteinian age.

Bedding dip data from core site CRP-3 in Victoria Land, Antarctica

Bedding dips in the CRP-3 drillhole were determined in three ways: (1) analysis of a dipmeter log, (2) identification of bed boundaries on borehole televiewer log images, and (3) identification of bed boundaries on digital images of the outer surfaces of oriented cores. All three methods determine both dip magnitude and downdip azimuth of bedding. Dipmeter results document variations in bedding dip throughout the logged interval (20-902 mbsf), whereas core and televiewer results are available at present only for selected depth intervals. Dipmeter data indicate that structural dip is remarkably constant, at 21° dip to azimuth 65°, throughout the Tertiary shelf section, except for the top 100 m where dips appear to be 5-10° shallower. This pattern, in conjunction with the systematically increasing dips throughout CRP-2A, suggests that the growth faulting active during CRP-2A deposition began during the final period of deposition at CRP-3. Normal faults at 260 and 539 mbsf in CRP-3 exhibit neither drag (localized dip steepening) nor significant changes in structural dip across them. Oriented core and televiewer analyses, covering a total of 200 m in the interval 400-900 mbsf, indicate bedding patterns that confirm the dipmeter results. The doleritic breccia at the base of the Tertiary section has steeper dips than overlying structural dips, possibly indicating a sedimentary dip to ENE in these fan sediments. Dip directions in the underlying Devonian Beacon sandstone are surprisingly similar to those in the overlying Tertiary section. Superimposed on the average Beacon dip of 22° to the ENE are localized tilts of up to 20°, probably caused by Tertiary fracturing and brecciation rather than original sedimentary dip variations.

Miocene to Pliocene planktonic foraminifers in ODP Hole 134-832B

One hundred and sixty core samples were analyzed from Hole 832B to evaluate planktonic foraminiferal datum levels, and to zone and correlate the borehole succession. A total of 32 biostratigraphic events were recognized in the interval from Core 134-832B-59R through 134-832B-73R (702.49 through 846.4 meters below seafloor [mbsf]). These include 17 first appearance datum levels (FAD), 10 last appearance datum levels (LAD), and 5 coiling-change events in trochospiral species. The studied succession has been subdivided into nine planktonic foraminiferal zones (viz. downsequence N.22, N.21, N.20, N.19, N.18, N.17B, N.17A-N.16, N.15, N.8). The zonal index species occur in the expected stratigraphic order for zonal correlation, but some of the zonal boundaries may be diachronous compared to other localities in the western Pacific region. The FAD of Globorotalia (Truncorotalia) truncatulinoides (d' Orbigny) at 714.10 mbsf defines the boundary between the Zone N.22 and N.21; the boundary between Zones N.21 and N.20 at 741.73 mbsf is marked by the FAD of Globorotalia (Truncorotalia) tosaensis Takayanagi and Saito. The lower boundary of Zone N.20 is placed at 747.65 mbsf, based on the FAD of Globorotalia (Truncorotalia) crassaformis s.s. (Galloway and Wissler); the FAD of Sphaeroidinella dehiscens (Parker and Jones) at 756.61 mbsf defines the boundary between Zones N.18 and N.19. The FAD of Globorotalia (Globorotalia) tumida tumida (Brady) at 811.15 mbsf marks the boundary between Zones N.18 and N.17B. The boundary between Zones N.17B and N.17Ais placed at 843.52 mbsf, based on the FAD of Pulleniatina primalis Banner and Blow. A change in depositional conditions occurs at 846.4 mbsf just below the Zone N.17B lower boundary and is marked by the first appearance of abundant planktonic foraminifers in the region. The interval between 849.13 and 856.1 mbsf is placed in undifferentiated Zones N.17A and N.16, based on the rare occurrence of Neogloboquadrina acostaensis (Blow). The sparsely fossiliferous volcanic sandstone unit between 934.19 and 955.67 mbsf is positioned within Zone N.15 based on the presence of Globigerina (Zeaglobigerina) nepenthes Todd and Globigerinoides (Zeaglobigerina) druryi Arkers, and absence of N. acostaensis and Globorotalia (Jenkinsella) siakensis LeRoy. An unconformity between 955.67 and 971.80 mbsf may explain the absence of Zones N.14 through N.9. Basal Zone N.8 is recognized at 971.80 to 1008.60 mbsf by the presence of Globigerinoides sicanus De Stefani and the absence of Praeorbulina and Orbulina spp. The age of the succession between 702.49 and 1008.6 mbsf extends from the latest Pliocene or earliest Pleistocene (Zone N.22) to the earliest middle Miocene (Zone N.8). Among the datum levels evaluated here, the following events are considered to be the most reliable for time correlation in the studied region: the FADs of G. (T.) truncatulinoides, G. (T.) tosaensis, G. (T.) crassaformis, S. dehiscens, G. conglobatus (Brady), G. (G.) tumida tumida, and P. primalis; and the LADs of Globorotalia (Menardella) multicamerata Cushman and Jarvis, and Dentoglobigerina altispira altispira (Cushman and Jarvis). Application of a chronometric scale to part of the succession, suggests that the interval of calcareous sediment between 702.49 and 846.4 mbsf accumulated at about 30 m/m.y.

Interstitial water chemistry, Deep Sea Drilling Project, Leg 96

On Leg 96 of the Deep Sea Drilling Project (DSDP), holes were drilled in Orca and Pigmy basins on the northern Gulf of Mexico continental slope and on the Mississippi Fan. The holes on the fan encountered interbedded sand, silt, and mud deposited extremely rapidly, most during late Wisconsin glacial time. Pore-water chemistry in these holes is variable, but does not follow lithologic changes in any simple way. Both Ca and SO4 are enriched in the pore water of many samples from the fan. Two sites drilled in the prominent central channel of the middle fan show rapid SO4 reduction with depth, whereas two nearby sites in overbank deposits show no sulfate reduction for 300 m. Calcium concentration decreases as SO4 is depleted and Li follows the same pattern. Strontium, which like Li, is enriched in samples enriched in Ca, does not decrease with SO4 and Ca. Potassium in the pore water decreases with depth at almost all sites. Sulfate reduction was active at the two basin sites and, as on the fan, this resulted in calcium carbonate precipitation and a lowering of pore water Ca, Mg, and Li. The Orca Basin site was drilled through a brine pool of 258? salinity. Pore-water salinity decreases smoothly with depth to 50 m and remains well above normal seawater values to the bottom of the hole at about 90 m. This suggests constant sedimentation under anoxic hypersaline conditions for at least the last 50,000 yr.

Tab. 1: Meerfelder Maar Drilling B4, stratigraphy and sequence of the lake sediments (pdf 215 kB)

A core from Meerfelder Maar, with a basal age of 29,000 years, provides a continuous sedimentary sequence from Late-Glacial times to the present. It includes the stratigraphical marker of the Laach Pumice Tuff. Sedimentological, geochemical, palynological, palaeobiological, palaeomagnetic and palaeontological analyses permit reconstructions of the history of the lake and its catchment area, and hence of the climate of the region, to be made. The discovery of Middle Oligocene marine, detrital fossils in the maar sediments provides insights into the palaeogeography of the Eifel region during Tertiary times.

(Tables 1, 2) Permafrost borehole characteristics in the Nordic Area during the IPY 2007-2009

This paper provides a snapshot of the permafrost thermal state in the Nordic area obtained during the International Polar Year (IPY) 2007-2009. Several intensive research campaigns were undertaken within a variety of projects in the Nordic countries to obtain this snapshot. We demonstrate for Scandinavia that both lowland permafrost in palsas and peat plateaus, and large areas of permafrost in the mountains are at temperatures close to 0°C, which makes them sensitive to climatic changes. In Svalbard and northeast Greenland, and also in the highest parts of the mountains in the rest of the Nordic area, the permafrost is somewhat colder, but still only a few degrees below the freezing point. The observations presented from the network of boreholes, more than half of which were established during the IPY, provide an important baseline to assess how future predicted climatic changes may affect the permafrost thermal state in the Nordic area. Time series of active-layer thickness and permafrost temperature conditions in the Nordic area, which are generally only 10 years in length, show generally increasing active-layer depths and rising permafrost temperatures.

Heavy metal and petroleum product concentrations in waters at the Obskaya 1 drill site

During recent years, the basins of the Kara Sea (Kamennomysskaya, Obskaya, and Chugor'yakhinskaya structures) in the Russian Federation have been considered as promising regions for oil and gas exploration and, simultaneously, as possible paths of relatively cheap pipeline and tanker transportation of hydrocarbons projected for recovery. On the other hand, exploration operations, recovery, and transportation of gas pose a considerable risk of accidents and environmental pollution, which causes a justified concern about the future state of the ecological system of the Gulf of Ob and the adjoining parts of the Kara Sea. Therefore, regular combined environmental investigations (monitoring) are the most important factor for estimating the current state and forecasting the dynamics of the development of estuary systems. The program of investigations (schedule, station network, and measured parameters) is standardized in accordance with the international practice of such work and accounts for the experience of monitoring studies of Russian and foreign researchers. Two measurement sessions were performed during ecological investigations in the region of exploration drilling: at the beginning at final stage of drilling operations and borehole testing; in addition, natural parameters were determined in various parts of the Ob estuary before the beginning of investigations. Hydrophysical and hydrochemical characteristics of the water medium were determined and bottom sediments and water were analyzed for various pollutants (petroleum products, heavy metals, and radionuclides). The forms of heavy-metal occurrence in river and sea waters were determined by the method of continuous multistep filtration, which is based on water component fractionation on membrane filters of various pore sizes. These investigations revealed environmental pollution by chemical substances during the initial stage of drilling operations, when remains of fuels, oils, and solutions could be spilled, and part of the chemical pollutants could enter the environment. Owing to horizontal and vertical turbulent diffusion, wave mixing, and the effect of the general direction of currents in the Ob estuary from south to north, areas are formed with elevated concentrations of the analyzed elements and compounds. However, the concentration levels of chemical pollutants are practically no higher than the maximum admissible concentrations, and their substantial dissipation to the average regional background contents can be expected in the near future. Our investigations allowed us to determine in detail the parameters of anthropogenic pollution in the regions affected by hydrocarbon exploration drilling in the Obskii and Kamennomysskii prospects in the Gulf of Ob and estimate their influence on the ecological state of the basin of the Ob River and the Kara Sea on the whole.

Borehole temperature, submarine permafrost methane concentrations and pore water chemistry measured on borehole BK2, central Laptev Sea shelf

Submarine permafrost degradation has been invoked as a cause for recent observations of methane emissions from the seabed to the water column and atmosphere of the East Siberian shelf. Sediment drilled 52 m down from the sea ice in Buor Khaya Bay, central Laptev Sea revealed unfrozen sediment overlying ice-bonded permafrost. Methane concentrations in the overlying unfrozen sediment were low (mean 20 µM) but higher in the underlying ice-bonded submarine permafrost (mean 380 µM). In contrast, sulfate concentrations were substantially higher in the unfrozen sediment (mean 2.5 mM) than in the underlying submarine permafrost (mean 0.1 mM). Using deduced permafrost degradation rates, we calculate potential mean methane efflux from degrading permafrost of 120 mg/m**2 per year at this site. However, a drop of methane concentrations from 190 µM to 19 µM and a concomitant increase of methane d13C from -63 per mil to -35 per mil directly above the ice-bonded permafrost suggest that methane is effectively oxidized within the overlying unfrozen sediment before it reaches the water column. High rates of methane ebullition into the water column observed elsewhere are thus unlikely to have ice-bonded permafrost as their source.

Pliocene/Pleistocene benthic foraminiferal abundances from six drilling cores

Twenty percent (19 genera, 95 species) of cosmopolitan, deep-sea (500-4000 m), benthic foraminiferal species became extinct during the late Pliocene-Middle Pleistocene (3-0.12 Ma), with the peak of extinctions (76 species) occurring during the mid-Pleistocene Climate Transition (MPT, 1.2-0.55 Ma). One whole family (Stilostomellidae, 30 species) was wiped out, and a second (Pleurostomellidae, 29 species) was decimated with just one species possibly surviving through to the present. Our studies at 21 deep-sea core sites show widespread pulsed declines in abundance and diversity of the extinction group species during more extreme glacials, with partial interglacial recoveries. These declines started in the late Pliocene in southern sourced deep water masses (Antarctic Bottom Water, Circumpolar Deep Water) and extending into intermediate waters (Antarctic Intermediate Water, North Atlantic Deep Water) in the MPT, with the youngest declines in sites farthest downstream from high-latitude source areas for intermediate waters. We infer that the unusual apertural types that were targeted by this extinction period were adaptations for a specific kind of food source and that it was probably the demise of this microbial food that resulted in the foraminiferal extinctions. We hypothesize that it may have been increased cold and oxygenation of the southern sourced deep water masses that impacted on this deep water microbial food source during major late Pliocene and Early Pleistocene glacials when Antarctic ice was substantially expanded. The food source in intermediate water was not impacted until major glacials in the MPT when there were significant expansion of polar sea ice in both hemispheres and major changes in the source areas, temperature, and oxygenation of global intermediate waters.

Miocene to Pleistocene diatom biostratigraphy with a focus on Thalassiosira in sediments of ODP Leg 186 sites

Late Neogene biostratigraphy of diatoms has been investigated from two sites occupied during Ocean Drilling Program (ODP) Leg 186 off the coast of northeast Japan. A unique aspect of ODP Leg 186 was the installation of two permanent borehole geophysical observatories at the deep-sea terrace along the Japan Trench. The Neogene subsidence history of the forearc was documented from both Sites 1150 and 1151, and Quaternary to middle Miocene (16 Ma) sediments represent a nearly continuous stratigraphic sequence including numerous ash records, especially during the past 9 m.y. Diatoms are found in most samples in variable abundance and in a moderately well preserved state throughout the sequence. The assemblages are characterized consistently by age-diagnostic species of Denticulopsis and Neodenticula found in regions of high surface water productivity typical of middle to high latitudes. The Neogene North Pacific diatom zonation divides the Miocene to Quaternary sequences fundamentally well, except that the latest Miocene through early Pliocene Thalassiosira oestrupii Subzone is not applicable. Miocene and late Pliocene through Pleistocene diatom datum levels that have been proven to be of great stratigraphic utility in the North Pacific Ocean appear to be nearly isochronous within the level of resolution constrained by core catcher sample spacing. The taxonomy and stratigraphy of previously described species determined to be useful across the Miocene/Pliocene boundary have been investigated on the basis of the evolutionary changes within the Thalassiosira trifulta group. The biostratigraphically important forms belonging to the genus Thalassiosira have been illustrated with scanning electron micrographs.

Miocene dissolution facies and microfacies at Northwest Atlantic Deep Sea Drilling Project Site 93-603

Depth fluctuations of the lysocline and calcite compensation depth (CCD) through time were investigated at Deep Sea Drilling Project Site 603, Leg 93. The CCD fell during the middle Miocene at the onset of the Western Boundary Undercurrent, correlated with seismic Horizon X. Subsequently deposited units show fluctuations of the dissolution curve. Major changes in dissolution facies correspond with lithologic boundaries.