Use of chemical tracers in assessing the diet and foraging regions of eastern North Pacific killer whales

Top predators in the marine environment integrate chemical signals acquired from their prey that reflect both the species consumed and the regions from which the prey were taken. These chemical tracers-stable isotope ratios of carbon and nitrogen; persistent organic pollutant (POP) concentrations, patterns and ratios; and fatty acid profiles-were measured in blubber biopsy samples from North Pacific killer whales (Orcinus orca) (n=84) and were used to provide further insight into their diet, particularly for the offshore group, about which little dietary information is available. The offshore killer whales were shown to consume prey species that were distinctly different from those of sympatric resident and transient killer whales. In addition, it was confirmed that the offshores forage as far south as California. Thus, these results provide evidence that the offshores belong to a third killer whale ecotype. Resident killer whale populations showed a gradient in stable isotope profiles from west (central Aleutians) to east (Gulf of Alaska) that, in part, can be attributed to a shift from off-shelf to continental shelf-based prey. Finally, stable isotope ratio results, supported by field observations, showed that the diet in spring and summer of eastern Aleutian Island transient killer whales is apparently not composed exclusively of Steller sea lions.     

Naturally acid waters from Copahue volcano,Argentina

Volcanic acid sulfate–chloride brines form through absorption of volcanic vapors in shallow reservoirs of meteoric water. Reaction with surrounding volcanic rocks leads to partial neutralization of the fluids and precipitation of secondary minerals. Chemical data of such acid waters from Copahue volcano, Argentina, covering 8 years of observations, show evidence for changes in composition related to water rock interaction at depth prior to emergence of the fluids at the surface. The chemical composition changed dramatically during the 2000 eruption of Copahue, with enhanced concentrations and fluxes of Mg, Na, Fe and Al, followed in 2001 by rapidly declining concentrations and element fluxes. The subsequent 5 years saw more variable element ratios and strong depletions in K and Al. Most incompatible elements are released from the rock matrix stochiometrically, whereas some elements are enriched through vapor input from the magma (As, Pb, Zn). Most fluids have LREE enrichments relative to the rock matrix, but during periods of new magma intrusion the LREE enrichment decreases as does the magnitude of the negative Eu anomaly in the fluids. These observations are interpreted assuming early dissolution of plagioclase, olivine and volcanic glass that occurs during intrusion of new magma into the hydrothermal system. The high field strength elements are virtually immobile even in these hot acid fluids, with Nb and Ta more so than Hf and Zr. The mobility of U and Th in these fluids is comparable, at variance with Th behavior in neutral fluids. The local rivers and lakes of Copahue are fertilized by volcanic dissolved P, and most surface waters with pH < 3 have high levels of As. The acid fluids from Copahue may be surficial analogs for deep subduction fluids that evolve below zones of arc magma generation as well as for early Mars environments that are thought to have had large acid lakes.     

The late Cretaceous Arman flora of Magadan oblast,Northeastern Russia

The Arman flora from the volcanogenic-sedimentary beds of the Arman Formation is systematically studied using materials from the Arman River basin and the Nelkandya-Khasyn interfluve (Magadan oblast, Northeastern Russia). Seventy-three species of fossil plants belonging to 49 genera are described. They consist of liverworts, horsetails, ferns, seed ferns, cycadaleans, bennettitaleans, ginkgoaleans, czekanowskialeans, conifers, gymnosperms of uncertain systematic affinity, and angiosperms. The Arman flora shows a unique combination, with relatively ancient Early Cretaceous ferns and gymnosperms occurring alongside younger Late Cretaceous plants, primarily angiosperms. The similarity of the Arman flora to the Penzhina and Kaivayam floras of northwestern Kamchatka and the Tylpegyrgynai flora of the Pekul’nei Ridge allows the Arman flora to be dated as Turonian and Coniacian (Late Cretaceous), which is corroborated by isotopic (U-Pb and ⁴⁰Ar/³⁹Ar) age determination for the plant-bearing layers.     

WATIN—A COMPUTER PROGRAM FOR GENERATING INPUT FILES FOR WATEQF

Abstract. WATIN is a FORTRAN 77 program for creating and modifying input files of analytical data for WATEQF, the aqueous geochemical speciation/saturation model. WATIN uses menus to display information about the data file and to accept new information from the user. In addition to providing basic editing functions, WATIN provides default values for WATEQF parameters and checks for errors and inconsistencies in the data file. WATIN simplifies and streamlines access to WATEQF for both researchers and students, and along with WATEQF, can be an important part of a geochemical data analysis system.     

Spatial flow and sedimentation patterns within patches of epibenthic structures: Combining field,flume and modelling experiments

The objectives of the present study were twofold: (1) to identify spatial sedimentation and erosion patterns developing within patches of epibenthic structures (i.e. physical structures that protrude from the sediments, originating either from animals or plants) as a consequence of biophysical interactions; and (2) to assess the relevance of hydrodynamic flume studies for the long-term sediment dynamics in the field. We addressed these objectives by using patches of well-defined artificial structures (bamboo canes) for which we could easily monitor the long-term sediment dynamics in the field, measure the hydrodynamic effects in detail in the flume, and simulate the field and flume set-up with a commercially available hydrodynamic model. Two-year monitoring in the field showed that sedimentation was much larger in the high-density patches than the low-density ones. Within the high-density patches, comparable spatial patterns emerged at different field sites: erosion at the front and the side of the patches, and sedimentation more down-stream within the patches. The low-density patches showed no such patterns, and were generally characterised by some small-scale erosion directly around individual bamboo canes. Sedimentation and erosion in the field was well explained by the patterns in bed shear stress that were derived from our flume measurements. The 3D hydrodynamic modelling facilitated up-scaling of the flume results to the field, but failed to simulate accurately the effects at the leading edge. We conclude that: (A) field observations on sedimentation revealed interesting spatial patterns, but could not elucidate underlying processes; (B) detailed hydrodynamic measurements in a flume can elucidate these underlying processes, provided that appropriate scaling is being used; (C) flume studies are by definition not able to capture all spatial scales that are relevant for estuarine landscape formation and will always cause some flow artefacts; (D) hydrodynamic modelling offers a valuable tool to upscale flume observations, even though present models are not yet capable of fully reproducing all detailed spatial patterns; and (E) spatial heterogeneity is very important when looking at small-scale patches. There is a need for more spatially explicit and scale-dependent knowledge on bio-physical interactions.     

Peridotitic mantle xenoliths from kimberlites on the Ekati Diamond Mine property, N.W.T., Canada: major element compositions and implications for the lithosphere beneath the central Slave craton

The composition, structure and thermal state of the lithosphere beneath the Slave craton have been studied by analysing over 300 peridotitic mantle xenoliths or multiphase xenocrysts entrained within kimberlites in the Lac de Gras area. These xenoliths are derived from seven kimberlites located on the Ekati Diamond Mine™ property and define a detailed stratigraphic profile through the central Slave lithosphere from less than 120 km down to 200 km. Two dominant peridotite types are present, namely garnet-bearing harzburgite and lherzolite with rare occurrences of chromite-facies peridotite, websterite and wehrlite. The pressures and temperatures (P–T's) defined by the entire data-set range from 28 to 62 kbar and 650 to 1250 °C, respectively, and approximately intersect the diamond stability field at 900 °C and 42 kbar. There is no apparent change in the geotherm with depth that is discernable beyond the resolution of the various thermobarometers. The peridotites can be divided into two compositional zones—a shallow layer dominated by garnet harzburgite that straddles the diamond–graphite boundary and a deeper layer that is strongly dominated by garnet lherzolite. Compositionally, the harzburgites (and to a lesser extent, the shallow lherzolites) are ultra-depleted relative to the more fertile deeper layer, irrespective of whether they reside within the graphite or diamond stability field. This ultra-depleted layer beneath Ekati continues to 150 km.     

Internally consistent geothermometers for garnet peridotites and pyroxenites

Mutual relationships among temperatures estimated with the most widely used geothermometers for garnet peridotites and pyroxenites demonstrate that the methods are not internally consistent and may diverge by over 200°C even in well-equilibrated mantle xenoliths. The Taylor (N Jb Min Abh 172:381–408, 1998) two-pyroxene (TA98) and the Nimis and Taylor (Contrib Mineral Petrol 139:541–554, 2000) single-clinopyroxene thermometers are shown to provide the most reliable estimates, as they reproduce the temperatures of experiments in a variety of simple and natural peridotitic systems. Discrepancies between these two thermometers are negligible in applications to a wide variety of natural samples (≤30°C). The Brey and Köhler (J Petrol 31:1353–1378, 1990) Ca-in-Opx thermometer shows good agreement with TA98 in the range 1,000–1,400°C and a positive bias at lower T (up to +90°C, on average, at T _TA98 = 700°C). The popular Brey and Köhler (J Petrol 31:1353–1378, 1990) two-pyroxene thermometer performs well on clinopyroxene with Na contents of ~0.05 atoms per 6-oxygen formula, but shows a systematic positive bias with increasing Na_Cpx (+150°C at Na_Cpx = 0.25). Among Fe–Mg exchange thermometers, the Harley (Contrib Mineral Petrol 86:359–373, 1984) orthopyroxene–garnet and the recent Wu and Zhao (J Metamorphic Geol 25:497–505, 2007) olivine–garnet formulations show the highest precision, but systematically diverge (up to ca. 150°C, on average) from TA98 estimates at T far from 1,100°C and at T < 1,200°C, respectively; these systematic errors are also evident by comparison with experimental data for natural peridotite systems. The older O’Neill and Wood (Contrib Mineral Petrol 70:59–70, 1979) version of the olivine–garnet Fe–Mg thermometer and all popular versions of the clinopyroxene–garnet Fe–Mg thermometer show unacceptably low precision, with discrepancies exceeding 200°C when compared to TA98 results for well-equilibrated xenoliths. Empirical correction to the Brey and Köhler (J Petrol 31:1353–1378, 1990) Ca-in-Opx thermometer and recalibration of the orthopyroxene–garnet thermometer, using well-equilibrated mantle xenoliths and TA98 temperatures as calibrants, are provided in this study to ensure consistency with TA98 estimates in the range 700–1,400°C. Observed discrepancies between the new orthopyroxene–garnet thermometer and TA98 for some localities can be interpreted in the light of orthopyroxene–garnet Fe³⁺ partitioning systematics and suggest localized and lateral variations in mantle redox conditions, in broad agreement with existing oxybarometric data. Kinetic decoupling of Ca–Mg and Fe–Mg exchange equilibria caused by transient heating appears to be common, but not ubiquitous, near the base of the lithosphere.