Concentrations of Ti, Fe, and Al and radiogenic isotope data for sediments of ODP Leg 177

Identifying terrigenous sources in deep-sea sediments may reveal temporal trends in paleocirculation and the relative role of eolian, upwelled, and hemipelagic Fe sources to surface waters. Bulk elemental and isotopic geochemistry of deep-sea sediments recovered during Ocean Drilling Program Leg 177 in the southeastern Atlantic sector of the Southern Ocean reveal several important aspects of paleocirculation and terrigenous provenance. The sites studied span 43°-53°S and represent different oceanographic settings relative to regional hydrography and sediment type. Bulk sediment geochemistry indicates that terrigenous provenance varied over the past 600 k.y. Site 1089, the northernmost site, exhibits clear glacial-interglacial variability in provenance, while provenance appears to vary regardless of climate state at the more southerly sites (Site 1093 and 1094). Nd and Sr isotopes and Sm/Nd ratios of the terrigenous fraction indicate that study sites have geochemically distinguishable provenance. Nd and Sr isotopes further suggest that Sites 1089 and 1094 both contain detrital components that originated in South America over the past 30 k.y.; however, Site 1089 is also influenced by southern African sources and the strength of the Agulhas Current. The e-Nd data support a more hemipelagic source for the terrigenous material rather than an eolian source based on comparisons with Antarctic ice core data and known sea-ice extent.

Stable carbon isotope record of sediment core Bass_River_Site

A thick, apparently continuous section recording events of the latest Paleocene thermal maximum in a neritic setting was drilled at Bass River State Forest, New Jersey as part of ODP Leg 174AX [Miller, Sugarman, Browning et al., 1998]. Integrated nannofossil and magneto-stratigraphy provides a firm chronology supplemented by planktonic foraminiferal biostratigraphy. This chronologic study indicates that this neritic section rivals the best deep-sea sections in providing a complete record of late Paleocene climatic events. Carbon and oxygen isotopes measured on benthic foraminifera show a major (4.0% in carbon, 2.3% in oxygen) negative shift correlative with the global latest Paleocene carbon isotope excursion (CIE). A sharp increase in kaolinite content coincides with the isotope shift in the Bass River section, analogous to increases found in several other records. Carbon and oxygen isotopes remain low and kaolinite content remains high for the remainder of the depositional sequence above the CIE (32.5 ft, 9.9 m), which we estimate to represent 300-500 k.y. We interpret these data as indicative of an abrupt shift to a warmer and wetter climate along the North American mid-Atlantic coast, in concert with global events associated with the CIE.

Age dating and isotopic analyses of sediment core RC11-120

Using the concept of 'orbital tuning', a continuous, high-resolution deep-sea chronostratigraphy has been developed spanning the last 300,000 yr. The chronology is developed using a stacked oxygen-isotope stratigraphy and four different orbital tuning approaches, each of which is based upon a different assumption concerning the response of the orbital signal recorded in the data. Each approach yields a separate chronology. The error measured by the standard deviation about the average of these four results (which represents the 'best' chronology) has an average magnitude of only 2500 yr. This small value indicates that the chronology produced is insensitive to the specific orbital tuning technique used. Excellent convergence between chronologies developed using each of five different paleoclimatological indicators (from a single core) is also obtained. The resultant chronology is also insensitive to the specific indicator used. The error associated with each tuning approach is estimated independently and propagated through to the average result. The resulting error estimate is independent of that associated with the degree of convergence and has an average magnitude of 3500 yr, in excellent agreement with the 2500-yr estimate. Transfer of the final chronology to the stacked record leads to an estimated error of +/-1500 yr. Thus the final chronology has an average error of +/-5000 yr.

Water temperature reconstructions based on paired Uk'37 and Tex86 records, and paired surface and subsurface Mg/Ca records

This dataset contains the collection of available published paired Uk'37 and Tex86 records spanning multi-millennial to multi-million year time scales, as well as a collection of Mg/Ca-derived temperatures measured in parallel on surface and subsurface dwelling foraminifera, both used in the analyses of Ho and Laepple, Nature Geoscience 2016. As the signal-to-noise ratios of proxy-derived Holocene temperatures are relatively low, we selected records that contain at least the last deglaciation (oldest sample >18kyr BP).

Mapped distribution of intertidal habitats in Australia between 1999 and 2014, link to data in ArcGIS format (29 MB)

Shorebirds have declined severely across the East Asian-Australasian Flyway. Many species rely on intertidal habitats for foraging, yet the distribution and conservation status of these habitats across Australia remain poorly understood. Here, we utilised freely available satellite imagery to produce the first map of intertidal habitats across Australia. We estimated a minimum intertidal area of 9856 km**2, with Queensland and Western Australia supporting the largest areas. Thirty-nine percent of intertidal habitats were protected in Australia, with some primarily within marine protected areas (e.g. Queensland) and others within terrestrial protected areas (e.g. Victoria). In fact, three percent of all intertidal habitats were protected both by both marine and terrestrial protected areas. To achieve conservation targets, protected area boundaries must align more accurately with intertidal habitats. Shorebirds use intertidal areas to forage and supratidal areas to roost, so a coordinated management approach is required to account for movement of birds between terrestrial and marine habitats. Ultimately, shorebird declines are occurring despite high levels of habitat protection in Australia. There is a need for a concerted effort both nationally and internationally to map and understand how intertidal habitats are changing, and how habitat conservation can be implemented more effectively.

Life-history traits of two Salvelinus species and mercury concentrations in fish and prey in ten Canadian lakes (2006-2008)

Mercury concentrations ([Hg]) in Arctic food fish often exceed guidelines for human subsistence consumption. Previous research on two food fish species, Arctic char (Salvelinus alpinus) and lake trout (Salvelinus namaycush), indicates that anadromous fish have lower [Hg] than nonanadromous fish, but there have been no intraregional comparisons. Also, no comparisons of [Hg] among anadromous (sea-run), resident (marine access but do not migrate), and landlocked (no marine access) life history types of Arctic char and lake trout have been published. Using intraregional data from 10 lakes in the West Kitikmeot area of Nunavut, Canada, we found that [Hg] varied significantly among species and life history types. Differences among species-life history types were best explained by age-at-size and C:N ratios (indicator of lipid); [Hg] was significantly and negatively related to both. At a standardized fork length of 500 mm, lake trout had significantly higher [Hg] (mean 0.17 µg/g wet wt) than Arctic char (0.09 µg/g). Anadromous and resident Arctic char had significantly lower [Hg] (each 0.04 µg/g) than landlocked Arctic char (0.19 µg/g). Anadromous lake trout had significantly lower [Hg] (0.12 µg/g) than resident lake trout (0.18 µg/g), but no significant difference in [Hg] was seen between landlocked lake trout (0.21 µg/g) and other life history types. Our results are relevant to human health assessments and consumption guidance and will inform models of Hg accumulation in Arctic fish.

Geochemistry of ODP Leg 135 igneous rock samples

Ocean Drilling Program Leg 135 provided igneous rock cores from six sites drilled on a transect across the Lau Basin between the Lau Ridge remnant arc and the modem spreading ridges of the Central and Eastern Lau Spreading Centers. The drill cores sampled crust from the earliest stage of backarc extension (latest Miocene time, about 6 Ma), and younger crust (late Pliocene, about 3.8-2 Ma, and middle Pleistocene, about 0.64-0.8 Ma). Nearly all of the igneous samples are from tholeiitic basalt flows; many of them are interbedded with arc-composition volcaniclastic sediments. Rock compositions range from olivine-plagioclase-clinopyroxene basalt, with up to 8% MgO, to oceanic andesites with less than 3.2% MgO and silica contents as high as 56%. The oldest rocks recovered are close in composition to rocks formed at the modern Central and Eastern Lau Spreading Centers and have MORB-like characteristics. Generation of the oldest units was coeval with arc-tholeiitic volcanism on the Lau Ridge less than 100 km to the west. The arc and backarc melts came from different mantle sources. At three sites near the center of the basin, the crust is arc-tholeiitic basalt, two-pyroxene basaltic-andesite, and two-pyroxene andesite. These rocks have many similarities to modem Tofua Arc lavas yet they were drilled within 70 km of the MORB-like Eastern Lau Spreading Center. Estimates of the minimum age for these arc-like rocks indicate that they are late Pliocene (about 2 Ma). These ages overlap the age of the nearby Eastern Lau Spreading Center. The heterogeneous crust of the Lau Basin carries many of the signatures of supra-subduction zone (SSZ) melts but also has a distinct MORB-like component. Mixing between SSZ and MORB mantle sources may explain the variations and the spatial distribution of magma types.