Accumulation of particulate organic carbon at the Eurasian continental margin during late Quaternary times

Data on the amount and composition of organic carbon were determined in sediment cores from the Kara and Laptev Sea continental margin, representing oxygen isotope stages 1-6. The characterization of organic matter is based on hydrogen index (HI) values, n-alkanes and maceral composition, indicating the predominance of terrigenous organic matter through space and time. The variations in the amount and composition of organic carbon are mainly influenced by changes in fluvial sediment supply, Atlantic water inflow, and continental ice sheets. During oxygen isotope stage (OIS) 6, high organic carbon contents in sediments from the Laptev Sea and western East Siberian Sea continental margin were probably caused by the increased glacial erosion and further transport in the eastward-flowing boundary current along the continental margin. During OIS 5 and early OIS 3, some increased amounts of marine organic matter were preserved in sediments east of the Lomonosov Ridge, suggesting an influence of nutrient-rich Pacific waters. During OIS 2, terrigenous organic carbon supply was increased along the Barents and western Kara Sea continental margin caused by extended continental ice sheets in the Barents Sea (Svalbard to Franz Josef Land) area and increased glacial erosion. Along the Laptev Sea continental margin, on the other hand, the supply of terrigenous (organic) matter was significantly reduced due to the lack of major ice sheets and reduced river discharge. Towards the Holocene, the amount of total organic carbon (TOC) increased along the Kara and Laptev Sea continental margin, reaching average values of up to 0.5 g C/cm**2/ky. Between about 8 and 10 ka (9 and 11 Cal ka), i.e., during times when the inner shallow Kara and Laptev seas became largely flooded for the first time after the Last Glacial Maximum, maximum supply of terrigenous organic carbon occurred, which is related to an increase in coastal erosion and Siberian river discharge. During the last 8000 years, the increased amount of marine organic carbon preserved in the sediments from the Kara and Laptev Sea continental margin is interpreted as a result of the intensification of Atlantic water inflow along the Eurasian continental margin.

Early Cretaceous spores and pollen of ODP Leg 103 holes

About 80 species of spores and pollen grains were recorded during detailed palynological investigations of selected Lower Cretaceous sections from Holes 638B and 638C and the bottom of Hole 641C. Most of them are long-ranging taxa with worldwide distribution. However, on the Iberian margin and in the southern European basins, Trilobosporites canadensis, Trilobosporites bernissartensis, Parvisaccites amplus, Foveosporites subtriangularis, and Ephedripites multicostatus seem to be index species of the Valanginian to late Aptian interval. Clavatipollenites was not recovered in the Barremian marginal marine sediments.

(Table T1) Stable carbon and oxygen isotope ratios of benthic foraminifera in the Late Pliocene-Pleistocene section of ODP Site 181-1123 in the Southwest Pacific

Stable isotope records were generated for a late Pliocene-early Pleistocene interval from Ocean Drilling Program (ODP) Site 1123 in the southwest Pacific (41°47 S, 171°30 W; 3290 m water depth). Based on these data, new revisions were made to the shipboard splice and composite section. The isotope records will be used to evaluate the influence of North Atlantic and Southern Ocean deepwater masses on water entering the Pacific in the Deep Western Boundary Current. Three holes were cored at Site 1123, yielding a complete composite section over approximately the last 4.7 m.y. A representative spliced record ("the splice") was developed aboard ship based on magnetic susceptibility, gamma ray attenuation bulk density, and percent reflectance data from the three adjacent holes (Carter, McCave, Richter, Carter, et al., 1999, doi:10.2973/odp.proc.ir.181.2000). No gaps in the sedimentary record were detected for the multiple-cored section of Site 1123. In addition to the isotope data, postcruise revisions to the splice and composite section based on stable isotope data are described here.

Late pleistocene and holocene sedimentation in the central and eastern Persian Gulf

The sandfraction of the sediment was analysed in five cores, taken from 65 m water depth in the central and eastern part of the Persian Gulf. The holocene marls are underlayn by aragonite muds, which are probably 10-11,000 years old. 1. The cores could be subdivided into coarse grained and fine grained layers. Sorting is demonstrated by the following criteria: With increasing median values of the sandfraction - the fine grained fraction decreases within each core; - the median of each biogenic component, benthonic as well as planktonic, increases; - the median of the relict sediment, which in core 1179 was carried upward into the marl by bioturbation, increases; - the percentages of pelecypods, gastropods, decapods and serpulid worms in the sandfraction increase, the percentages of foraminifera and ostracods decrease; - the ratios of pelecypods to foraminifera and of decapods to ostracods increase; - the ratios of benthonic molluscs to planktonic molluscs (pteropods) and of benthonic foraminifera to planktonic foraminifera increase (except in core 1056 and 1179); - the ratio of planktonic molluscs (pteropods) to planktonic foraminifera increases; - the globigerinas without orbulinas increase, the orbulinas decrease in core 1056. Different settling velocities of these biogenic particles help in better understanding the results : the settling velocities, hence the equivalent hydrodynamic diameters, of orbulinas are smaller than those of other globigerinas, those of planktonic foraminifera are smaller than those of planktonic molluscs, those of planktonic molluscs are smaller than those of benthonic molluscs, those of pelecypods are smaller than those of gastropods. Bioturbation could not entirely distroy this "grain-size-stratification". Sorting has been stronger in the coarse layers than in the finer ones. As a cause variations in the supply of terrigenous material at constant strength of tidal currents is suggested. When much terrigenous material is supplied (large contents of fine grained fraction) the sedimentation rates are high: the respective sediment surface is soon covered and removed from the influence of tidal currents. When, however, the supply of terrigenous material is small, more sandy material is taken away in all locations within the influence of terrigenous supply. Thus the biogenic particles in the sediment do not only reflect the organic production, but also the influence of currents. 2. There is no parameter present in all cores that is independently variable from grain size and can be used for stratigraphic correlation. The two cores from the Strait of Hormus were correlated by their sequences of coarse and fine grained layers. 3. The sedimentation rates of terrigenous material, of total planktonic and benthonic organisms and of molluscs, foraminifera, echinoids and ophiuroids are shown in table 1 (total sediment 6.3-75.5 cm/1000 yr, biogenic carbonate 1.9-3.6 cm/1000 yr). The sedimentation rates of benthonic organisms are nearly the same in the cores of the Strait of Hormus, whereas near the Central Swell they are smaller. In the upper parts of the two cores of the Strait of Hormus sedimentation rates are higher than in the deeper parts, where higher median values point to stronger reworking. 4. The sequence of coarse and fine grained intervals in the two cores of the Hormus Strait, attributed to variations in climate, as well as the increase of terrigenous supply from the deeper to the upper parts of the cores, agrees with the descriptions in the literature of the post Pleistocene climate as becoming more humid. The rise of sea level is sedimentologically not measurable in the marly sediments - except perhaps for the higher content of echinoids in the lower part of core 1056. These may be attributed to the influence of a migrating wave-base. 5. The late Pleistocene aragonite mud is very fine grained (> 50%< 2 p) and poor in fossils (0.5-1.8%) biogenic particles of total sediment. The sand fraction consists almost entirely of white clumps, c. 0.1 mm in diameter (1177), composed of aragonite needles and of detrital minerals with the same size (1201). The argonite mud was probably not formed in situ, because the water depth at time of formation was at most 35 m at least 12 m. The sorting of the sediment (predominance of the fine grained sand), the absence of larger biogenic components and of pellets, c. 0.2-0.5 mm in diameter, which are typical for Recent and Pleistocene locations of aragonite formation, as well as the sedimentological conditions near the sampling points, indicate rather a transport of aragonite mud from an area of formation in very shallow waters. Sorting as well as lenticular fabric in core 1201 point to sedimentation within the influence of currents. During alternating sedimentation - and reworking processes the aragonitic matrix was separated from the silt - and sand-sized minerals. The lenses grade into touches because of bioturbation. 6. In core 1056 D2 from Hormus Bay the percentages of organic carbon, total nitrogen and total carbonate were determined. With increasing amounts of smaller grain sizes the content of organic matter increases, whereas the amount of carbonate decreases. The amounts of organic carbon and of nitrogen decrease with increasing depth, probably due to early-diagenetic decomposition processes. Most of the total nitrogen is of organic origin, only about 10% may well be inorganically fixed as ammonium-nitrogen. In the upper part of the core the C/N-ratio increases with increasing depth. This may be connected with a stronger decomposition of nitrogen-containing organic compounds. The general decrease of the C/N-ratios in the lower part of the core may be explained by the relative increase of inorganically fixed ammonium-nitrogen with decreasing content of organic matter.

Late Eocene to Recent deep-sea benthic foraminifera from the Central equatorial Pacific Ocean

Benthic foraminifers were studied in upper Eocene to Recent core-catcher samples from DSDP Sites 573, 574, and 575. The sites are on a north-south transect from the equator to about 05°N at about 133°W, water depth 4300 to 4600 m. At Site 574 additional samples were used to study the Eocene/Oligocene boundary in detail. About 200 specimens were counted per sample. The fauna is highly diverse (about 50 to 70 species per sample) and is of low dominance. The diversity is not related to age or sub-bottom depth. Many species are cosmopolitan and probably have wide environmental tolerances. Fluctuations in frequency of some taxa (e.g., Nuttallides umbonifera, Epistominella exigua, and Uvigerina spp.) cannot be correlated from one site to another. Several common species (e.g. Oridorsalis umbonatus and Globocassidulina subglobosa) range from late Eocene to Recent. First and last appearances are generally difficult to define precisely because many species are rare. For some species these datums differ from one site to another, but several datum levels are within 1 m.y. at all sites. First and last appearances are most numerous in two intervals, the late Eocene to early Oligocene (about 32 to 37 Ma) and the early to middle Miocene (about 13 to 18.5 Ma). Isotopic events occur within each of these periods of benthic faunal change, but the isotopic events have a shorter duration and start after the initiation of the changes in the fauna. Changes in deep-sea benthic faunal composition are not directly related to short-term oceanographic changes as expressed in isotopic records.

Mid-to Late Holocene flood frequency in the northeastern Alps as recorded in varved sediments of Lake Mondsee

Annually laminated (varved) lake sediments with intercalated detrital layers resulting from sedimentary input by runoff events are ideal archives to establish precisely dated records of past extreme runoff events. In this study, the mid- to late Holocene varved sediments of Lake Mondsee (Upper Austria) were analysed by combining sedimentological, geophysical and geochemical methods. This approach allows to distinguish two types of detrital layers related to different types of extreme runoff events (floods and debris flows) and to detect changes in flood activity during the last 7100 years. In total, 271 flood and 47 debris flow layers, deposited during spring and summer, were identified, which cluster in 18 main flood episodes (FE 1-18) with durations of 30-50 years each. These main flood periods occurred during the Late Neolithic (7100-7050 vyr BP and 6470-4450 vyr BP), the late Bronze Age and the early Iron Age (3300-3250 and 2800-2750 vyr BP), the late Iron Age (2050-2000 vyr BP), throughout the Dark Ages Cold Period (1500-1200 vyr BP), and at the end of the Medieval Warm Period and the Little Ice Age (810-430 vyr BP). Summer flood episodes in Lake Mondsee are generally more abundant during the last 1500 years, often coinciding with major advances of alpine glaciers. Prior to 1500 vyr BP, spring/summer floods and debris flows are generally less frequent, indicating a lower number of intense rainfall events that triggered erosion. In comparison with the increase of late Holocene flood activity in western and northwestern (NW) Europe, commencing already as early as 2800 yr BP, the hydro-meteorological shift in the Lake Mondsee region occurred much later. These time lags in the onset of increased hydrological activity might be either due to regional differences in atmospheric circulation pattern or to the sensitivity of the individual flood archives. The Lake Mondsee sediments represent the first precisely dated and several millennia long summer flood record for the northeastern (NE) Alps, a key region at the climatic boundary of Atlantic, Mediterranean and East European air masses aiding a better understanding of regional and seasonal peculiarities of flood occurrence under changing climate conditions.

(Appendix) Late Cretaceous calcareous nannofossils of DSDP Holes 80-549 and 80-551

he early late Cretaceous (Cenomanian-early Turonian) is thought to have been one of the warmest periods of the Phanerozoic. This period was characterised by tropical sea surface temperatures of up to 36 °C and a pole-to-equator-gradient of less than 10 °C. The subsequent Turonian-Maastrichtian was characterised by a continuous climatic cooling, peaking in the Maastrichtian. This climatic cooling and the resulting palaeoceanographic changes had an impact on planktic primary producer communities including calcareous nannofossils. In order to gain a better understanding of these Cenomanian-Maastrichtian palaeoceanographic changes, calcareous nannofossils have been studied from the proto North Atlantic (Goban Spur, DSDP Sites 549, 551). In order to see potential differences between open oceanic and shelf dwelling nannofossils, the data from Goban Spur have been compared to findings from the European shelf (northern Germany). A total of 77 samples from Goban Spur were studied for calcareous nannofossils revealing abundant (mean 6.2 billion specimens/g sediment) and highly diverse (mean 63 species/sample) nannofossil assemblages. The dominant taxa are Watznaueria spp. (mean 30.7%), Prediscosphaera spp. (mean 18.3%), Zeugrhabdotus spp. (mean 8.3%), Retecapsa spp. (mean 7.2%) and Biscutum spp. (mean 6.6%). The Cenomanian assemblages of both Goban Spur (open ocean) and Wunstorf (shelf) are characterised by elevated abundances of high fertility taxa like Biscutum spp., Zeugrhabdotus spp. and Tranolithus orionatus. Early Turonian to Maastrichtian calcareous nannofossil assemblages of Goban Spur are, however, quite different to those described from European sections. Oceanic taxa like Watznaueria spp., Retecapsa spp. and Cribrosphearella ehrenbergii dominate in Goban Spur whereas the fertility indicators Biscutum spp. and T. orionatus are more abundant in the European shelf assemblages. This shift from a homogeneous distribution of calcareous nannofossils in the Cenomanian towards a heterogeneous one in the Turonian-Maastrichtian implies a change of the ocean circulation. The "eddy ocean" system of the Cenomanian was replaced by an oceanic circulation similar to the modern one in the Turonian-Maastrichtian, caused by the cooling. The increased pole-to-equator-gradients resulted in an oceanic circulation similar to the modern one.

Late Glacial and Holocene data from sediment cores MD99-2236 and MD99-2256

The Laurentide Ice Sheet (LIS) was a large, dynamic ice sheet in the early Holocene. The glacial events through Hudson Strait leading to its eventual demise are recorded in the well-dated Labrador shelf core, MD99-2236 from the Cartwright Saddle. We develop a detailed history of the timing of ice-sheet discharge events from the Hudson Strait outlet of the LIS during the Holocene using high-resolution detrital carbonate, ice rafted detritus (IRD), d18O, and sediment color data. Eight detrital carbonate peaks (DCPs) associated with IRD peaks and light oxygen isotope events punctuate the MD99-2236 record between 11.5 and 8.0 ka. We use the stratigraphy of the DCPs developed from MD99-2236 to select the appropriate DeltaR to calibrate the ages of recorded glacial events in Hudson Bay and Hudson Strait such that they match the DCPs in MD99-2236. We associate the eight DCPs with H0, Gold Cove advance, Noble Inlet advance, initial retreat of the Hudson Strait ice stream (HSIS) from Hudson Strait, opening of the Tyrrell Sea, and drainage of glacial lakes Agassiz and Ojibway. The opening of Foxe Channel and retreat of glacial ice from Foxe Basin are represented by a shoulder in the carbonate data. DeltaR of 350 years applied to the radiocarbon ages constraining glacial events H0 through the opening of the Tyrell Sea provided the best match with the MD99-2236 DCPs; DeltaR values and ages from the literature are used for the younger events. A very close age match was achieved between the 8.2 ka cold event in the Greenland ice cores, DCP7 (8.15 ka BP), and the drainage of glacial lakes Agassiz and Ojibway. Our stratigraphic comparison between the DCPs in MD99-2236 and the calibrated ages of Hudson Strait/Bay deglacial events shows that the retreat of the HSIS, the opening of the Tyrell Sea, and the catastrophic drainage of glacial lakes Agassiz and Ojibway at 8.2 ka are separate events that have been combined in previous estimates of the timing of the 8.2 ka event from marine records. SW Iceland shelf core MD99-2256 documents freshwater entrainment into the subpolar gyre from the Hudson Strait outlet via the Labrador, North Atlantic, and Irminger currents. The timing of freshwater release from the LIS Hudson Strait outlet in MD99-2236 matches evidence for freshwater forcing and LIS icebergs carrying foreign minerals to the SW Iceland shelf between 11.5 and 8.2 ka. The congruency of these records supports the conclusion of the entrainment of freshwater from the retreat of the LIS through Hudson Strait into the subpolar gyre and provides specific time periods when pulses of LIS freshwater were present to influence climate.

Orbitally tuned time scale and astronomical forcing in the middle Eocene to early Oligocene determined on ODP and IODP sediment cores

Deciphering the driving mechanisms of Earth system processes, including the climate dynamics expressed as paleoceanographic events, requires a complete, continuous, and high-resolution stratigraphy that is very accurately dated. In this study, we construct a robust astronomically calibrated age model for the middle Eocene to early Oligocene interval (31-43 Ma) in order to permit more detailed study of the exceptional climatic events that occurred during this time, including the Middle Eocene Climate Optimum and the Eocene/Oligocene transition. A goal of this effort is to accurately date the middle Eocene to early Oligocene composite section cored during the Pacific Equatorial Age Transect (PEAT, IODP Exp. 320/321). The stratigraphic framework for the new time scale is based on the identification of the stable long eccentricity cycle in published and new high-resolution records encompassing bulk and benthic stable isotope, calibrated XRF core scanning, and magnetostratigraphic data from ODP Sites 171B-1052, 189-1172, 199-1218, and 207-1260 as well as IODP Sites 320-U1333, and -U1334 spanning magnetic polarity Chrons C12n to C20n. Subsequently we applied orbital tuning of the records to the La2011 orbital solution. The resulting new time scale revises and refines the existing orbitally tuned age model and the Geomagnetic Polarity Time Scale from 31 to 43 Ma. Our newly defined absolute age for the Eocene/Oligocene boundary validates the astronomical tuned age of 33.89 Ma identified at the Massignano (Italy) global stratotype section and point. Our compilation of geochemical records of climate-controlled variability in sedimentation through the middle-to-late Eocene and early Oligocene demonstrates strong power in the eccentricity band that is readily tuned to the latest astronomical solution. Obliquity driven cyclicity is only apparent during very long eccentricity cycle minima around 35.5 Ma, 38.3 Ma and 40.1 Ma.

Strontium isotope analysis of seawater and at a mixture of planktic foraminifera during the Paleocene and Early Eocene from different holes of ODP Leg 2008

We refined the strontium isotope seawater curve for the Paleocene and early Eocene by analysis of samples recovered from the Walvis Ridge during Ocean Drilling Project (ODP) Leg 208. The highest 87Sr/86Sr values occurred in the earliest Paleocene at 65 Ma and generally decreased throughout the Paleocene, reaching minimum values between 53 and 51 Ma in the early Eocene before beginning to increase again at 50 Ma. A plausible explanation for the 87Sr/86Sr decrease between 65 and 51 Ma is increased rates of hydrothermal activity and/or the eruption and weathering of large igneous provinces (e.g., Deccan Traps and North Atlantic). Strontium isotope variations closely parallel sea level and benthic d18O changes during the late Paleocene and early Eocene, supporting previous studies linking tectonic reorganization and increased volcanism to high sea level, high CO2, and warm global temperatures.

Organic geochemistry and Rock-Eval pyrolysis at DSDP Leg 79 and 41 Holes

Cenozoic and Mesozoic sediments ranging in age from Pleistocene to Early Jurassic/late Triassic were recovered on DSDP Leg 79, off Morocco at Sites 544 to 547 in front of the Mazagan Plateau. The main zone of oil genesis should be reached at Site 547 within the Jurassic section. Organic material of marine origin with good petroleum potential characterizes the late Eocene slumps of Site 547 and originates from reworked organic matter of Cretaceous origin. Organic enrichment also occurs at Site 545 during the middle to late Albian period. Since the organic matter appears to be autochthonous, reducing environments of deposition are inferred. In the other Cretaceous deposits, variably altered organic matter of the same origin predominates. Finally, a transect including Site 370 off the Agadir Canyon, is studied: detrital organic matter and reducing environments of deposition were more developed during Albian time for Site 370 than for Site 545.

(Table S1) Carbon and oxygen isotope values, and Mn and Sr concentrations of Early Jurassic sediments

For much of the Mesozoic record there has been an inconclusive debate on the possible global significance of isotopic proxies for environmental change and of sequence stratigraphic depositional sequences. We present a carbon and oxygen isotope and elemental record for part of the Early Jurassic based on marine benthic and nektobenthic molluscs and brachiopods from the shallow marine succession of the Cleveland Basin, UK. The invertebrate isotope record is supplemented with carbon isotope data from fossil wood, which samples atmospheric carbon. New data elucidate two major global carbon isotope events, a negative excursion of ~2 per mil at the Sinemurian-Pliensbachian boundary, and a positive excursion of ~2 per mil in the Late Pliensbachian. The Sinemurian-Pliensbachian boundary event is similar to the slightly younger Toarcian Oceanic Anoxic Event and is characterized by deposition of relatively deepwater organic-rich shale. The Late Pliensbachian strata by contrast are characterized by shallow marine deposition. Oxygen isotope data imply cooling locally for both events. However, because deeper water conditions characterize the Sinemurian-Pliensbachian boundary in the Cleveland Basin the temperature drop is likely of local significance; in contrast a cool Late Pliensbachian shallow seafloor agrees with previous inference of partial icehouse conditions. Both the large-scale, long-term and small-scale, short-duration isotopic cycles occurred in concert with relative sea level changes documented previously from sequence stratigraphy. Isotope events and the sea level cycles are concluded to reflect processes of global significance, supporting the idea of an Early Jurassic in which cyclic swings from icehouse to greenhouse and super greenhouse conditions occurred at timescales from 1 to 10 Ma.

Oligocene to early Miocene benthic foraminifera in the eastern Equatorial Pacific

We investigated Oligocene and early Miocene benthic foraminiferal faunas (> 105 µm in size) from Ocean Drilling Program (Leg 199) Site 1218 (4826 m water depth and ~3300 to ~4000 m paleo-water depth) and Site 1219 (5063 m water depth and ~4200 to ~4400 m paleo-water depth) to understand the response of abyssal benthic foraminifera to mid-Oligocene glacial events in the eastern Equatorial Pacific Ocean. Two principal factor assemblages were recognized. The Factor 1 assemblage (common Nuttallides umbonifer) is related to either an influx of the Southern Component Water (SCW), possibly carbonate undersaturated, or a decrease in seasonality of the food supply from the surface ocean. The Factor 2 assemblage is characterized by typical deep-sea taxa living under variable trophic conditions, possibly with a seasonal component in food supply. The occurrence of abyssal benthic foraminifera faunas during the mid-Oligocene depends on either the effect of SCW or the seasonality of food resources. The Factor 1 assemblage was most common near 76Ol-C11r, 73Ol-C10rn and 67Ol-C9n (ca. 30.2, 29.1 and 26.8 Ma respectively by Pälike et al. (2006, doi:10.1126/science.1133822)). This indicates that the effect of SCW increased or the seasonal input of food from the surface ocean to benthic environments was weakened close to these glacial events. In contrast, the huge export flux of small biogenic carbonate particles close to these glacial events might be responsible for carbonate-rich sediments buffering carbonate undersaturation. Changes in deep-water masses or the periodicity of food supply from the surface ocean and variation in surface carbonate production affected by orbital forcing had an impact on the mid-Oligocene faunas of abyssal benthic foraminifera around the intervals of glacial events in the eastern Equatorial Pacific Ocean. The Factor 1 assemblage decreased sharply at ? 30 Ma (29.8 Ma by Pälike et al. (2006), 30.0 Ma by CK95) and returned to dominance after ? 29 Ma (28.6 Ma by Pälike et al. (2006), 28.8 Ma by CK95). It is likely that the effect of SCW (possibly carbonate undersaturated) has intensified since the late Oligocene. The faunal transition of benthic foraminifera in the eastern Equatorial Pacific Ocean at ~29 Ma might be attributable to the influence of Northern Component Water (NCW) input to the Southern Ocean and the subsequent formation of SCW at about that time.

Öate Cretaceous to early Paleogene nutrient and paleoproductivity records of ODP Leg 171 sites

We evaluate phosphorus (P) and biogenic barium (bio-Ba) as nutrient burial and export productivity indicators for the Late Cretaceous and early Paleogene, combining these with calcium carbonate (CaCO3), organic carbon (C), and bulk CaCO3 C isotopes (d13C). Sample ages span 36-71 Ma (~1 sample/0.5 m.y.) for a depth transect of sites in the western North Atlantic (Blake Nose, Ocean Drilling Program Leg 171B, Sites 1052, 1051, and 1050). We use a multitracer approach including redox conditions to investigate export productivity surrounding the global Paleocene d13C maximum (~57 Ma). Reducing conditions render most of the bio-Ba record not useful for export productivity interpretations. P and organic C records indicate that regional nutrient and organic C burial were high at ~61 and ~69 Ma, and low during the Paleocene d13C maximum, a time of proposed global high relative organic C burial. Observed organic C burial changes at Blake Nose cannot explain this C isotope excursion.

Late Cenozoic stable isotope record of benthic and planktonic foraminifera from the Pacific Ocean

Stable isotopic analyses of Middle Miocene to Quaternary foraminiferal calcite from east equatorial and central north Pacific DSDP cores have provided much new informatlon on the paleoceanography of the Pacific Neogene The history of delta18O change in planktonic foraminifera reflects the changing Isotopic composition and temperature of seawater at the time of test formation. Changes in the isotopic composition of benthonic foraminifera largely reflect changes m the volume of continental ice. Isotopic data from these cores indicates the following sequence of events related to continental glaciation (1) A permanent Antarctic ice sheet developed late in the Middle Miocene (about 13 to 11.5 m.y. ago) (2) The Late Miocene (about 11.5 to 5 m.y. ago) is marked by significant variation in delta18O of about 0.5? throughout, indicating instability of Antarctic ice cap size or bottom-water temperatures (3) The early Pliocene (5 to about 3 m.y. ago) was a time of relative stability in ice volume and bottom-water temperature (4) Growth of permanent Northern Hemisphere ice sheets is referred to have begun about 3 m.y. ago (5) The late Pliocene (3 to about 1.8 m.y. ago) is marked by one major glaciation or bottom-water cooling dated between about 2.1 to 2.3 m.y. (6) There is some evidence that the frequency of glacial-interglacial cycles increased at about 0.9 m.y. There is significant variation in delta13C at these sites but no geochemical interpretation is offered in this paper. The most outstanding feature of delta13C results is a permanent shift of about -0.8? found at about 6.5 m.y. in east equatorial and central north Pacific benthonic foraminifera. This benthonic carbon shift may form a useful marker in deep-sea cores recovering Late Miocene carbonates.