Trace element ratios of Globigerina bulloides from the southwest Pacific Ocean

We present Mg/Ca data for Globigerina bulloides from 10 core top sites in the southwest Pacific Ocean analyzed by laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). Mg/Ca values in G. bulloides correlate with observed ocean temperatures (7°C-19°C), and when combined with previously published data, an integrated Mg/Ca-temperature calibration for 7°C-31°C is derived where Mg/Ca (mmol/mol) = 0.955 * e**(0.068 * T) (r**2 = 0.95). Significant variability of Mg/Ca values (20%-30%) was found for the four visible chambers of G. bulloides, with the final chamber consistently recording the lowest Mg/Ca and is interpreted, in part, to reflect changes in the depth habitat with ontogeny. Incipient and variable dissolution of the thin and fragile final chamber, and outermost layer concomitantly added to all chambers, caused by different cleaning techniques prior to solution-based ICPMS analyses, may explain the minor differences in previously published Mg/Ca-temperature calibrations for this species. If the lower Mg/Ca of the final chamber reflects changes in depth habitat, then LA-ICPMS of the penultimate (or older) chambers will most sensitively record past changes in near-surface ocean temperatures. Mean size-normalized G. bulloides test weights correlate negatively with ocean temperature (T = 31.8 * e**(-30.5*wtN); r**2 = 0.90), suggesting that in the southwest Pacific Ocean, temperature is a prominent control on shell weight in addition to carbonate ion levels.

Major, trace element and XRF data for sediments and fish tooth samples, from a shallow marine setting with varying redox conditions (Site U1356, Wilkes Land Margin, E.Antarctica)

Fossil fish teeth from pelagic open ocean settings are considered a robust archive for preserving the neodymium (Nd) isotopic composition of ancient seawater. However, using fossil fish teeth as an archive to reconstruct seawater Nd isotopic compositions in different sedimentary redox environments and in terrigenous-dominated, shallow marine settings is less proven. To address these uncertainties, fish tooth and sediment samples from a middle Eocene section deposited proximal to the East Antarctic margin at Integrated Ocean Drilling Program Site U1356 were analyzed for major and trace element geochemistry, and Nd isotopes. Major and trace element analyses of the sediments reveal changing redox conditions throughout deposition in a shallow marine environment. However, variations in the Nd isotopic composition and rare earth element (REE) patterns of the associated fish teeth do not correspond to redox changes in the sediments. REE patterns in fish teeth at Site U1356 carry a typical mid-REE-enriched signature. However, a consistently positive Ce anomaly marks a deviation from a pure authigenic origin of REEs to the fish tooth. Neodymium isotopic compositions of cleaned and uncleaned fish teeth fall between modern seawater and local sediments and hence could be authigenic in nature, but could also be influenced by sedimentary fluxes. We conclude that the fossil fish tooth Nd isotope proxy is not sensitive to moderate changes in pore water oxygenation. However, combined studies on sediments, pore waters, fish teeth and seawater are needed to fully understand processes driving the reconstructed signature from shallow marine sections in proximity to continental sources. This article is protected by copyright. All rights reserved.

Halogene concentrations and iodine isotopic composition in pore water on Hydrare Ridge, Cascadia continental margin

We report iodine and bromine concentrations in a total of 256 pore water samples collected from all nine sites of Ocean Drilling Program Leg 204, Hydrate Ridge. In a subset of these samples, we also determined iodine ages in the fluids using the cosmogenic isotope 129I (T1/2 = 15.7 Ma). The presence of this cosmogenic isotope, combined with the strong association of iodine with methane, allows the identification of the organic source material responsible for iodine and methane in gas hydrates. In all cores, iodine concentrations were found to increase strongly with depth from values close to that of seawater (0.0004 mM) to concentrations >0.5 mM. Several of the cores taken from the northwest flank of the southern summit show a pronounced maximum in iodine concentrations at depths between 100 and 150 meters below seafloor in the layer just above the bottom-simulating reflector. This maximum is especially visible at Site 1245, where concentrations reach values as high as 2.3 mM, but maxima are absent in the cores taken from the slope basin sites (Sites 1251 and 1252). Bromine concentrations follow similar trends, but enrichment factors for Br are only 4-8 times that of seawater (i.e., considerably lower than those for iodine). Iodine concentrations are sufficient to allow isotope determinations by accelerator mass spectrometry in individual pore water samples collected onboard (~5 mL). We report 129I/I ratios in a few samples from each core and a more complete profile for one flank site (Site 1245). All 129I/I ratios are below the marine input ratio (Ri = 1500x10**-15). The lowest values found at most sites are between 150 and 250x10**-15, which correspond to minimum ages between 40 and 55 Ma, respectively. These ages rule out derivation of most of the iodine (and, by association, of methane) from the sediments hosting the gas hydrates or from currently subducting sediments. The iodine maximum at Site 1245 is accompanied by an increase in 129I/I ratios, suggesting the presence of an additional source with an age younger than 10 Ma; there is indication that younger sources also contribute at other sites, but data coverage is not yet sufficient to allow a definitive identification of sources there. Likely sources for the older component are formations of early Eocene age close to the backstop in the overriding wedge, whereas the younger sources might be found in recent sediments underlying the current locations of the gas hydrates.

Age determination and sea surface temperature reconstruction from marine and lake records, Iberian Peninsula

Selected multi-proxy and accurately dated marine and terrestrial records covering the past 2000 years in the Iberian Peninsula (IP) facilitated a comprehensive regional paleoclimate reconstruction for the Medieval Climate Anomaly (MCA: 900-1300 AD). The sequences enabled an integrated approach to land-sea comparisons and, despite local differences and some minor chronological inconsistencies, presented clear evidence that the MCA was a dry period in the Mediterranean IP. It was a period characterized by decreased lake levels, more xerophytic and heliophytic vegetation, a low frequency of floods, major Saharan eolian fluxes, and less fluvial input to marine basins. In contrast, reconstruction based on sequences from the Atlantic Ocean side of the peninsula indicated increased humidity. The data highlight the unique characteristics of the MCA relative to earlier (the Dark Ages, DA: ca. 500-900 years AD) and subsequent (the Little Ice Age, LIA: 1300-1850 years AD) colder periods. The reconstruction supports the hypothesis of Trouet et al. (2009, doi:10.1126/science.1166349), that a persistent positive mode of the North Atlantic Oscillation (NAO) dominated the MCA.

Tab. 1: Age of biogene material from the ice margin, Kofoed-Hansen Bræ and Storstrømmen

Early Holocene recession of the ice cover over Germania Land in North-East Greenland 7.5 ka B.P. brought the Inland Ice margin back to a position close to the present. Continued recession after that time lead to the formation of a "Storstrømmen Sound" which separated Germania Land from mainland Greenland in the period from about 6 to 1 ka B.P. The present filling of the approximately 100 km long sound by the glaciers of Storstrømmen and Kofoed-Hansen Bræ must therefore have taken place during the Little lce Age. In an archaeological sense this implies deterioration of the living conditions of Neo-Eskimos compared to those of Palaeo-Eskimos. The neoglacial re-formation and present existence of the glaciers as a Little Ice Age relict may imply a present-day instability in their dynamics, as demonstrated by the pulsations (surge-like behaviour) in the last part of the 20th century. An earlier Little Ice Age advance might possibly have had the same amplitude as that documented from the 20th century but its exact age and character is not known. The glacio-isostatic response of the earth's crust to the variations in the Holocene glacier load implies a relatively slow and slight emergence and subsequent submergence. The shift from emergence to submergence must have taken place between about 2 and 1 ka B.P.

Accumulation rate, carbon geochemistry and clay mineralogy of ODP Site 181-1123 sediments, southwest Pacific

Site 1123 is located on the northeastern flank of the Chatham Rise. Sedimentological and clay mineralogical analyses indicate a very fine grained carbonate-rich sediment. Smectite and illite are the main constituents of the clay mineral assemblage. High smectite values in the Eocene decrease in younger sediment sequences. Illite and chlorite concentrations increase in younger sediments with significant steps at 13.5, 9, and 6.4 Ma. The kaolinite content is near the detection limit and not significant. We observed only small fluctuations of the clay mineral composition, which indicates a uniform sedimentation process, probably driven by long-term processes. Good correspondence is shown between increasing illite and chlorite values and the tectonic uplift history of the Southern Alps.

Multiproxy sedimentation patterns of sediment cores from the continental margin off northeast Brazil

Tropical regions have been reported to play a key role in climate dynamics. To date, however, there are uncertainties in the timing and the amplitude of the response of tropical ecosystems to millennial-scale climate change. We present evidence of an asynchrony between terrestrial and marine signals of climate change during Heinrich events preserved in marine sediment cores from the Brazilian continental margin. The inferred time lag of about 1000 to 2000 years is much larger than the ecological response to recent climate change and appears to be related to the nature of hydrological changes.

Sedimentology of ODP sites in the Cape Basin, southeast Atlantic Ocean

Middle/late Miocene to early Pliocene sedimentary sequences along the continental margin of southwest Africa have changes that correspond to the carbonate crash (12-9 Ma) and biogenic bloom events (~7-4 Ma) described in the equatorial Pacific by Farrell et al. (1995, doi:10.2973/odp.proc.sr.138.143.1995). To explore the origins of these changes, we analyzed the carbon and coarse fraction contents of sediments from ODP Sites 1085, 1086, and 1087 at a time resolution of 5 to 30 kyr. Several major drops in CaCO3 concentration between 12 and 9 Ma are caused by dilution from major increases in clastic input from the Oranje River during global sea level regressions. Abundant pyrite crystals and good preservation of fish debris reflect low oxygenation of bottom/pore waters. Regional productivity was enhanced during the time equivalent to the carbonate crash period. Higher benthic/planktic foraminiferal ratios indicate that CaCO3 dissolution at Site 1085 peaked between 9 to 7 Ma, which was after the global carbonate crash. This period of enhanced dissolution suggests that Site 1085 was located within a low-oxygen water mass that dissolved CaCO3 more easily than North Atlantic Deep Water, which began to bathe this site at 7 Ma. At 7 to 6 Ma, the onset of the biogenic bloom, increases and variations in total organic carbon and benthic foraminiferal accumulation rates show that paleoproductivity increased significantly above values observed during the carbonate crash period and fluctuated widely. We attribute the late Miocene paleoproductivity increase off southwest Africa to ocean-wide increases in nutrient supply and delivery.

Distribution of benthic abyssal gastropods in the Iberian Deep-Sea Basin (Table 2)

During the cruises 3 and 15 of R.V. "Meteor", representatives of 7 families of benthic abyssal gastropods were collected. The prevalent group was the Turridae; the Naticidae are represented by 2 species, the remaining families by a single species each. A survey of the frequency and distribution of the species within the study area is given. A systematic part deals with the individual species in detail, including notes on taxonomy, material and distribution. Concerning the composition of the abyssal gastropod fauna of the present material, Neogastropoda are 4 times as many as Archaeogastropoda and 6 times as many as Mesogastropoda and Opisthobranchia. 89 % of all specimens are Neogastropoda. Usually deep-sea organisms have a non-pelagic development, but many of the Iberian deep-sea Turrids have a planktotrophic protoconch, that means a long pelagic larval period. Among the 19 species, 2 are cosmopolitan, 9 show a transatlantic distribution and 8 are confined to East-Atlantic basins.

Volcanic ash from the Peru continental margin

During Leg 112 off Peru, volcanic material was recorded from middle Eocene to Holocene time. The petrographical and chemical composition of tephra is consistent with an origin from the Andean volcanic arc. The amount and thickness of ash layers provide valuable evidence for explosive volcanic episodicity. The first indication of volcanism was found in mid-Eocene sediments. Three volcanic pulses date from Miocene time. Two intense episodes took place in upper Pliocene and from Pleistocene to Holocene time. Pliocene-Pleistocene tephra are restricted to the southern upper-slope and shelf sites, indicating a removal of the volcanic arc and the extinction of the northern Peru volcanoes. The Cenozoic tectonic phases of the Andean margin may be correlated with the Leg 112 volcanic records. The explosive supply of evolved magmatic products succeeded the Incaic and Quechua tectonic phases. Acidic glasses are related to both andesitic and shoshonitic series. The calc-alkaline factor (CAF) of these glasses exhibited moderate magmatic variations during middle and late Miocene time. A dramatic change occurred during the Pliocene-Pleistocene, reflected in a strong CAF increase and the appearance of potassium-rich evolved shoshonitic glasses. This took place when the Nazca Ridge subduction began. This change in the magma genesis and/or differentiation conditions is probably related to thickening of the upper continental plate and to a new configuration of the Benioff Zone.