Chronology and stable carbon isotopic ratios of sediments from the Western Pacific Warm Pool region

Instrumental data suggest that major shifts in tropical Pacific atmospheric dynamics and hydrology have occurred within the past century, potentially in response to anthropogenic warming. To better understand these trends, we use the hydrogen isotopic ratios of terrestrial higher plant leaf waxes (DDwax) in marine sediments from southwest Sulawesi, Indonesia, to compile a detailed reconstruction of central Indo-Pacific Warm Pool (IPWP) hydrologic variability spanning most of the last two millennia. Our paleodata are highly correlated with a monsoon reconstruction from Southeast Asia, indicating that intervals of strong East Asian summer monsoon (EASM) activity are associated with a weaker Indonesian monsoon (IM). Furthermore, the centennial-scale oscillations in our data follow known changes in Northern Hemisphere climate (e.g., the Little Ice Age and Medieval Warm Period) implying a dynamic link between Northern Hemisphere temperatures and IPWP hydrology. The inverse relationship between the EASM and IM suggests that migrations of the Intertropical Convergence Zone and associated changes in monsoon strength caused synoptic hydrologic shifts in the IPWP throughout most of the past two millennia.

Deep drilling of glaciers: Russian projects in the Arctic (1975-1995)

The data collection "Deep Drilling of Glaciers: Soviet-Russian projects in Arctic, 1975-1995" was collected by the following basic considerations: - compilation of deep (>100 m) drilling projects on Arctic glaciers, using data of (a) publications; (b) archives of IGRAN; (c) personal communication of project participants; - documentation of parameters, references. Accuracy of data and techniques applied to determine different parameters are not evaluated. The accuracy of some geochemical parameters (up to 1984 and heavy metalls) is uncertain. Most reconstructions of ice core age and of annual layer thickness are discussed; - digitizing of published diagrams (in case, when original numerical data were lost) and subsequent data conversion to equal range series and adjustment to the common units. Therefore, the equal-range series were calculated from original data or converted from digitized chart values as indicated in the metadata. For the methodological purpose, the equal-range series obtained from original and reconstructed data were compared repeatedly; the systematic difference was less then 5-7%. Special attention should be given to the fact, that the data for individual ice core parameters varies, because some parameters were originally measured or registered. Parameters were converted in equal-range series using 2 m steps; - two or more parameter values were determined, then the mean-weighted (i.e. accounting the sample length) value is assigned to the entire interval; - one parameter value was determined, measured or registered independently from the parameter values in depth intervals which over- and underlie it, then the value is assigned to the entire interval; - one parameter value was determined, measured or registered for two adjoining depth intervals, then the specific value is assigned to the depth interval, which represents >75% of sample length ; if each of adjoining depth intervals represents <75% of sample length, then the correspondent parameter value is assigned to both intervals of depth. This collection of ice core data (version 2000) was made available through the EU funded QUEEN project by S.M. Arkhipov, Moscow.

Origin and evolution of Cycladophora davisiana (Radiolaria) in DSDP Hole 19-192, Northwest Pacific

This paper documents the evolutionary history of Cycladophora davisiana Ehrenberg from an uppermost Miocene to Pleistocene sedimentary record in the high-latitude Northwest Pacific. It apparently evolved from C. sakaii Motoyama through a series of intermediates. C. sakaii has a relatively large shell with an external spongy layer. The evolutionary transition is characterized by a relatively rapid decrease in thorax size with a reduction of the spongy appendage. This change occurred during about 0.4 m.y. from 2.8 to 2.4 Ma without cladogenesis. Following this interval, a decrease in thorax size continued gradually up to the Recent, resulting in a very small morphology. Although the population of C. davisiana first appeared at about 2.5 Ma, some morphotypic specimens may occur in earlier periods as indistinguishable very small endmembers in the C. sakaii populations. Timing of the first appearance events both of morphotypic specimens and of a population of C. davisiana in Site 192 and previously reported cores does not disprove the idea that C. davisiana evolved first in the Northwest Pacific region, and later migrated into other regions of the world ocean. Biometrics clearly indicate no direct phylogenetic relationships between C. davisiana and C. cornutoides Kling in the studied core. Thus, the latter species, which was originally described as a variation and later elevated to a subspecies of the former species, is separated from the former species and raised to the species rank.

Stable carbon and oxygen isotope ratios of Late Miocene and Early Pliocene foraminifera from the Southwest Pacific

The Late Miocene-Early Pliocene paleoclimatic history has been evaluated for a deep drilled sediment sequence at Deep Sea Drilling Project Site 281 and a shallow water marine sediment sequence at Blind River, New Zealand, both of which lay within the Subantarctic water mass during the Late Miocene. A major, faunally determined, cooling event within the latest Miocene at Site 281 and Blind River coincides with oxygen isotopic changes in benthonic foraminiferal composition at DSDP Site 284 considered by Shackleton and Kennett (1975) to indicate a significant increase in Antarctic ice sheet volume. However, at Site 281 benthonic foraminiferal oxygen isotopic changes do not record such a large increase in Antarctic ice volume. It is possible that the critical interval is within an unsampled section (no recovery) in the latest Miocene. Two benthonic oxygen isotopic events in the Late Miocene (0.5 ? and 1 ? in the light direction) may be useful as time-stratigraphic markers. A permanent, negative, carbon isotopic shift at both Site 281 and Blind River allows precise correlations to be made between the two sections and to other sites in the Pacific region. Close interval sampling below the carbon shift at Site 281 revealed dramatic fluctuations in surface-water temperatures prior to a latest Miocene interval of refrigeration (Kapitean) and a strong pulse of dissolution between 6.6 and 6.2 +/- 0.1 m.y. which may be related to a fundamental geochemical change in the oceans at the time of the carbon shift (6.3-6.2 m.y.). No similar close interval sampling at Blind River was possible because of a lack of outcrop over the critical interval. Paleoclimatic histories from the two sections are very similar. Surface water temperatures and Antarctic ice-cap volume appear to have been relatively stable during the late Middle-early Late Miocene (early-late Tongaporutuan). By 6.4 m.y. cooler conditions prevailed at Site 281. Between 6.3 and 6.2 -+ 0.1 m.y. the carbon isotopic shift occurred followed, within 100,000 yr, by a distinct shallowing of water depths at Blind River. The earliest Pliocene (Opoitian) is marked by increasing surface-water temperatures.

(Table 1) Sr, Nd, and Pb isotopic composition of ODP Leg 129 basalts

Basaltic rocks recovered from three drill sites in the western Pacific during Ocean Drilling Program Leg 129 have fairly distinct Sr, Nd, and Pb isotopic compositions. The Cretaceous alkali olivine dolerites from Site 800 in the northern part of Pigafetta Basin have fairly low 87Sr/86Sri (0.70292-0.70320) and 143Nd/144Ndi (0.51277-0.51281) and high present-day Pb isotopic ratios (206Pb/204Pb = 20.53-21.45; 207Pb/204Pb = 15.70-15.77; 208Pb/204Pb = 40.02-40.68). The Middle Jurassic tholeiites from Site 801 in the southern part of the basin have low 87Sr/86Sri (0.70237-0.70248), high 143Nd/144Ndi (0.51298-0.51322), and moderate present-day Pb isotopic ratios (206Pb/204Pb = 18.20-19.12; 207Pb/204Pb = 15.47-15.60; 208Pb/204Pb = 37.56-38.18); isotopic compositions of the alkali olivine basalts overlying the tholeiites fall between those of the tholeiites and Site 800 dolerites. The Cretaceous tholeiites from Site 802 in the East Mariana Basin have high 87Sr/86Sri (0.70360-0.70372), fairly low 143Nd/144Ndi (0.51277-0.51280), and fairly low and homogeneous present-day Pb isotopic ratios (206Pb/204Pb = 18.37-18.39; 207Pb/204Pb = 15.49-15.51; 208Pb/204Pb = 38.34-38.39). Isotopic compositions of Site 801 tholeiites are indistinguishable from those of modern mid-ocean ridge basalts, consistent with the proposal that these tholeiites are a part of the oldest Pacific crust. The diverse isotopic compositions of the younger basalts appear to be the result of Jurassic Pacific plate migration over the geologically anomalous south-central Pacific region, wherein they acquired their distinct isotopic compositions. The anomalous region was volcanically more active during the Cretaceous than at present.

Tab. 1: Trace-element concentrations in ore samples collected from mercury mines and deposits in southwestern Alaska

A belt of small but numerous mercury deposits extends for about 500 km in the Kuskokwim River region of southwestern Alaska. The southwestern Alaska mercury belt is part of widespread mercury deposits of the circum Pacific region that are similar to other mercury deposits throughout the world because they are epithermal with formation temperatures of about 200 °C, the ore is dominantly cinnabar with Hg-Sb-As±Au geochemistry, and mineralized forms include vein, vein breccias, stockworks, replacements, and disseminations. The southwestern Alaska mercury belt has produced about 1400 t of mercury, which is small on an international scale. However, additional mercury deposits are likely to be discovered because the terrain is topographically low with significant vegetation cover. Anomalous concentrations of gold in cinnabar ore suggest that gold deposits are possible in higher temperature environments below some of the Alaska mercury deposits. We correlate mineralization of the southwestern Alaska mercury deposits with Late Cretaceous and early Tertiary igneous activity. Our 40Ar/39Ar ages of 70 ±3 Ma from hydrothermal sericites in the mercury deposits indicate a temporal association of igneous activity and mineralization. Furthermore, we suggest that our geological ancl geochemical data from the mercury deposits indicate that ore fluids were generated primarily in surrounding sedimentary wall rocks when they were cut by Late Cretaceous and early Tertiary intrusions. In our ore genesis model, igneous activity provided the heat to initiate dehydration reactions and expel fluids from hydrous minerals and formational waters in the surrounding sedimentary wall rocks, causing thermal convection and hydrothermal fluid flow through permeable rocks and along fractures and faults. Our isotopic data from sulfide and alteration minerals of the mercury deposits indicate that ore fluids were derived from multiple sources, with most ore fluids originating from the sedimentary wall rocks.

Global distributions of pteropods (Gymnosomata, Thecosomata, Pseudothecosomata) abundance and biomass - Gridded data product (NetCDF) - Contribution to the MAREDAT World Ocean Atlas of Plankton Functional Types

Pteropods are a group of holoplanktonic gastropods for which global biomass distribution patterns remain poorly resolved. The aim of this study was to collect and synthesize existing pteropod (Gymnosomata, Thecosomata and Pseudothecosomata) abundance and biomass data, in order to evaluate the global distribution of pteropod carbon biomass, with a particular emphasis on its seasonal, temporal and vertical patterns. We collected 25 902 data points from several online databases and a number of scientific articles. The biomass data has been gridded onto a 360 x 180° grid, with a vertical resolution of 33 WOA depth levels. Data has been converted to NetCDF format. Data were collected between 1951-2010, with sampling depths ranging from 0-1000 m. Pteropod biomass data was either extracted directly or derived through converting abundance to biomass with pteropod specific length to weight conversions. In the Northern Hemisphere (NH) the data were distributed evenly throughout the year, whereas sampling in the Southern Hemisphere was biased towards the austral summer months. 86% of all biomass values were located in the NH, most (42%) within the latitudinal band of 30-50° N. The range of global biomass values spanned over three orders of magnitude, with a mean and median biomass concentration of 8.2 mg C l-1 (SD = 61.4) and 0.25 mg C l-1, respectively for all data points, and with a mean of 9.1 mg C l-1 (SD = 64.8) and a median of 0.25 mg C l-1 for non-zero biomass values. The highest mean and median biomass concentrations were located in the NH between 40-50° S (mean biomass: 68.8 mg C l-1 (SD = 213.4) median biomass: 2.5 mg C l-1) while, in the SH, they were within the 70-80° S latitudinal band (mean: 10.5 mg C l-1 (SD = 38.8) and median: 0.2 mg C l-1). Biomass values were lowest in the equatorial regions. A broad range of biomass concentrations was observed at all depths, with the biomass peak located in the surface layer (0-25 m) and values generally decreasing with depth. However, biomass peaks were located at different depths in different ocean basins: 0-25 m depth in the N Atlantic, 50-100 m in the Pacific, 100-200 m in the Arctic, 200-500 m in the Brazilian region and >500 m in the Indo-Pacific region. Biomass in the NH was relatively invariant over the seasonal cycle, but more seasonally variable in the SH. The collected database provides a valuable tool for modellers for the study of ecosystem processes and global biogeochemical cycles.

Geochemistry of DSDP Hole 91-596

Geochemical analyses of sediments from the top 24.5 m of Deep Sea Drilling Project hole 596 (23°51.20'S, 169°39.27'W) show great variability in the composition of pelagic clays accumulated in the South Pacific since the late Cretaceous. Elemental associations indicate that most of this variability can be attributed to variations in abundances of six sediment end-member components: detrital (eolian), andesitic (volcanic), hydrothermal, hydrogenous, phosphate (fish debris), and biogenic silica. We develop a sedimentation model which is used to infer processes that might have influenced the accumulation rates of these components over the last 85 million years. The accumulation of eolian detritus in the South Pacific shows some similarities to that observed in the North Pacific and has been largely controlled by global climate trends in the Cenozoic. Much of the variation in the accumulation of other sediment components likely reflects the paleoceanographic evolution of the South Pacific. The most notable change in the sedimentary environment occurred at about the Paleogene/Neogene boundary. At that time, significant changes in the color, mineralogy, and chemistry of the sediment probably reflect major shifts in climate mode as well as oceanic circulation in the central South Pacific region.

Marine diatoms in deep sea sediments

Long-term evolution is thought to take opportunities that arise as a consequence of mass extinction (as argued, for example, by Gould, 2002) and the following biotic recovery, but there is absolutely no evidence for this being the case. However, our study shows that eutrophication by oceanic mixing also played a part in the enhancement of several evolutionary events amongst marine organisms, and these results could indicate that the rates of oceanic biodiversification may be slowed if upwelling becomes weakened by future global warming. This paper defines three distinct evolutionary events of resting spores of the marine diatom genus Chaetoceros, to reconstruct past upwelling through the analysis of several DSDP, ODP and land-based successions from the North, South and equatorial Pacific as well as the Atlantic Ocean during the past 40 million years. The Atlantic Chaetoceros Explosion (ACE) event occurred across the E/O boundary in the North Atlantic, and is characterized by resting spore diversification that occurred as a consequence of the onset of upwelling following changes in thermohaline circulation through global cooling in the early Oligocene. Pacific Chaetoceros Explosion events-1 and -2 (PACE-1 and PACE-2) are characterized by relatively higher occurrences of iron input following the Himalayan uplift and aridification at 8.5 Ma and ca. 2.5 Ma in the North Pacific region. These events not only enhanced the diversification and increased abundance of primary producers, including that of Chaetoceros, other diatoms and seaweeds, but also stimulated the evolution of zooplankton and larger predators, such as copepods and marine mammals, which ate these phytoplankton and plants. Current thinking suggests new evolutionary niches open up after a mass extinction, but our study finds that eutrophication can also stimulate evolutionary diversification. Moreover, in the opposite fashion, our results show that as thermohaline circulation abates, global warming progresses and the ocean surface becomes warmer, many marine organisms will be affected by the environmental degradation.

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.

Paleogene planktonic foraminifera of DSDP Hole 29-277

Stratigraphy of Paleogene deposits from high latitudes of the Pacific region (Koryak Highland, Kamchatka Peninsula, Karaginsky Island - in the northern hemisphere, Australian-Antarctic region - in the southern hemisphere) on planktonic foraminifera are under consideration in the book. Correlation with Paleogene of the warm Pacific belt is given. On the basis of geographic and stratigraphic distributions of planktonic foraminifera climatic zonation and the Paleogene climatic curve are analyzed. Description and photos of 115 species and varieties of planktonic foraminifera are given in the palaeontological part of the book.

Planktonic foraminifera of sediment core MD01-2390

Sea-surface temperature (SST) estimates in the sediment core MD01-2390 based on planktonic foraminiferal species abundances using five different transfer function techniques suggest nearly unchanged or unusually higher temperatures in the tropical southern South China Sea (SCS) during the Last Glacial Maximum (LGM) relative to modern temperatures. These results are in contrast to substantial cooling of 2-5 °C inferred by geochemical (Uk'37, Mg/Ca ratios) and terrestrial proxies from the western tropical Pacific region. Using multivariate statistics we show that the glacial southern SCS harboured unique planktonic foraminiferal assemblages that have no modern analogs. Analyses of faunal variation through the core reveal that planktonic foraminiferal assemblages responded to temperature changes inferred from Mg/Ca data but that this signal is subdued by superimposed variations in the relative abundance of Pulleniatina obliquiloculata and Neogloboquadrina pachyderma (dextral). These species occur in glacial samples at proportions that are not observed in the calibration data set. The glacial high abundance of N. pachyderma (dextral) are interpreted to reflect a seasonal (winter) inflow of cold surface water from the northeast via the Bashi Strait due to the combined effects of an intensified winter monsoon, a southward shift of the polar front and the eastward migration of the Kuroshio Current. In contrast, processes controlling the high relative abundances of P. obliquiloculata during the LGM may be unique to the southern SCS. We propose a scenario involving a stronger (winter) mixing or enhanced upwelling due to an intensified winter monsoon that prevented shallow-dwelling, warm indicators to establish larger populations during the LGM. Our results indicate that a no-analog behaviour of planktonic foraminifera faunas is responsible for the warm glacial conditions in this part of the western Pacific warm pool as implied by foraminiferal transfer functions and that a more significant surface cooling in the region as implied by terrestrial and geochemical (Mg/Ca ratios; alkenone unsaturation index) marine proxies is a more likely scenario.