An Acoustic-Instrumented Mine for Studying Subsequent Burial

The U.S. Navy is supporting the research to develop and validate stochastic, time-dependent, mine burial prediction models to aid the tactical decision making process. This research requires continuous monitoring of both mine behavior during burial, and the near-field processes responsible for burial. A new instrumented mine has been developed that far exceeds the capabilities of the earlier optically instrumented mine in terms of the burial processes that can be measured. The acoustic-instrumented mine (AIM) utilizes acoustic transducers to measure burial and scour, localized flow rates, and sediment size and concentration in the water column. The AIM also includes sensors for measuring mine orientation and movement, as well as oceanographic information such as significant waveheights, wave period, and water temperature. Four AIMs were constructed and deployed during the Indian Rocks Beach (IRB, FL) and Martha's Vineyard Coastal Observatory (MVCO, Edgartown, MA) mine burial experiments. The results from the field experiments have proven that the sensor suite is viable in providing a wealth of data that are critical in understanding and modeling the complex subsequent burial process.     

Pleistocene climatic change in Southern Australia and its effect on speleothem deposition in some Nullarbor caves

Activity ratios of ²³⁴U/²³⁸U, ²³⁰Th/²³⁴U, and ²³⁰Th/²³²Th have been determined for calcite, gypsum and halite speleothems from caves of the Nullarbor Plain, mostly in the area N and NW of Mundrabilla Station, for the purpose of U-series dating. All calcite speleothems contain adequate amounts of uranium for dating, but some show an excess of ²³⁰Th. Stratigraphic relationships indicate that there were at least three phases of calcium carbonate deposition in the Nullarbor caves. The calcite samples, with one possible exception, have ages in excess of ca. 400000 yrs BP. This suggests that no significant amounts of calcium carbonate deposition have taken place during the last 400ka. At present, active deposition of speleothems is restricted almost entirely to gypsum and halite. The only gypsum speleothem dated was found to have a finite age of ca. 185 ka. Six dates on a small halite speleothem containing insect and arachnid remains indicate that it formed rapidly during Holocene time.     

Constraining Holocene sea‐surface conditions in the south‐western Black Sea using dinoflagellate cysts

This paper presents two dinoflagellate cyst records from the south‐western shelf of the Black Sea. A new site, MAR05‐13, from the Sakarya shelf is described and placed into context with site MAR02‐45, ～250 km distant on the Thracian shelf. The records provide a centennial resolution of surface water conditions in the Holocene. Analysis of the data suggests that the surface salinity of the south‐western shelf increased in a gradual and progressive manner. In the period ～11 000–9000 cal a BP the assemblages suggest surface‐water salinities between 7–13 psu. The initial arrival of euryhaline species, ～8100 cal a BP, is linked to the reconnection of the Black Sea and Marmara Sea. The suggested surface water changes related to the reconnection took approximately 1000 years. Following this initial change in assemblages, a further increase in the number of euryhaline species is noted between 5000 and 4000 cal a BP. This is linked to the establishment of more saline surface‐water conditions, close to present‐day values. The record for MAR05‐13 highlights the complexity of the changes in cyst assemblages during the mid‐Holocene. Copyright © 2012 John Wiley & Sons, Ltd.     

Bounce Rock—A shergottite‐like basalt encountered at Meridiani Planum,Mars

Abstract– The Opportunity rover of the Mars Exploration Rover mission encountered an isolated rock fragment with textural, mineralogical, and chemical properties similar to basaltic shergottites. This finding was confirmed by all rover instruments, and a comprehensive study of these results is reported here. Spectra from the miniature thermal emission spectrometer and the Panoramic Camera reveal a pyroxene‐rich mineralogy, which is also evident in Mössbauer spectra and in normative mineralogy derived from bulk chemistry measured by the alpha particle X‐ray spectrometer. The correspondence of Bounce Rock’s chemical composition with the composition of certain basaltic shergottites, especially Elephant Moraine (EET) 79001 lithology B and Queen Alexandra Range (QUE) 94201, is very close, with only Cl, Fe, and Ti exhibiting deviations. Chemical analyses further demonstrate characteristics typical of Mars such as the Fe/Mn ratio and P concentrations. Possible shock features support the idea that Bounce Rock was ejected from an impact crater, most likely in the Meridiani Planum region. Bopolu crater, 19.3 km in diameter, located 75 km to the southwest could be the source crater. To date, no other rocks of this composition have been encountered by any of the rovers on Mars. The finding of Bounce Rock by the Opportunity rover provides further direct evidence for an origin of basaltic shergottite meteorites from Mars.     

Persistent organic pollutants and stable isotopes in biopsy samples (2004/2006) from Southern Resident killer whales

“Southern Resident” killer whales include three “pods” (J, K and L) that reside primarily in Puget Sound/Georgia Basin during the spring, summer and fall. This population was listed as “endangered” in the US and Canada following a 20% decline between 1996 and 2001. The current study, using blubber/epidermis biopsy samples, contributes contemporary information about potential factors (i.e., levels of pollutants or changes in diet) that could adversely affect Southern Residents. Carbon and nitrogen stable isotopes indicated J- and L-pod consumed prey from similar trophic levels in 2004/2006 and also showed no evidence for a large shift in the trophic level of prey consumed by L-pod between 1996 and 2004/2006. ∑PCBs decreased for Southern Residents biopsied in 2004/2006 compared to 1993–1995. Surprisingly, however, a three-year-old male whale (J39) had the highest concentrations of ∑PBDEs, ∑HCHs and HCB. POP ratio differences between J- and L-pod suggested that they occupy different ranges in winter.     

Hydrologic significance of carbon monoxide concentrations in ground water

Dissolved carbon monoxide (CO) is present in ground water produced from a variety of aquifer systems at concentrations ranging from 0.2 to 20 nanomoles per liter (0.0056 to 0.56 microg/L). In two shallow aquifers, one an unconsolidated coastal plain aquifer in Kings Bay, Georgia, and the other a fractured-bedrock aquifer in West Trenton, New Jersey, long-term monitoring showed that CO concentrations varied over time by as much as a factor of 10. Field and laboratory evidence suggests that the delivery of dissolved oxygen to the soil zone and underlying aquifers by periodic recharge events stimulates oxic metabolism and produces transiently high CO concentrations. In between recharge events, the aquifers become anoxic and more substrate limited, CO is consumed as a carbon source, and CO concentrations decrease. According to this model, CO concentrations provide a transient record of oxic metabolism affecting ground water systems after dissolved oxygen has been fully consumed. Because the delivery of oxygen affects the fate and transport of natural and anthropogenic contaminants in ground water, CO concentration changes may be useful for identifying predominantly anoxic ground water systems subject to periodic oxic or microaerophilic conditions.     

A simple pore water hydrogen diffusion syringe sampler

Molecular hydrogen (H(2)) is an important intermediate product and electron donor in microbial metabolism. Concentrations of dissolved H(2) are often diagnostic of the predominant terminal electron-accepting processes in ground water systems or aquatic sediments. H(2) concentrations are routinely measured in ground water monitoring wells but are rarely measured in saturated aquatic sediments due to a lack of simple and practical sampling methods. This report describes the design and development (including laboratory and field testing) of a simple, syringe-based H(2) sampler in (1) saturated, riparian sediments, (2) surface water bed sediments, and (3) packed intervals of a fractured bedrock borehole that are inaccessible by standard pumped methods.     

Integrated stratigraphy and 40Ar/39Ar chronology of the early to middle Miocene Upper Freshwater Molasse in western Bavaria (Germany)

A detailed integrated stratigraphic study (biostratigraphy and magnetostratigraphy) was carried out on five sections from the western part of the Bavarian Upper Freshwater Molasse of the North Alpine Foreland Basin (NAFB), greatly improving the chronostratigraphy of these sediments. The sections belong to the lithostratigraphic units Limnische Untere Serie (UL) and Fluviatile Untere Serie (UF) and contain 19 (mostly new) small-mammal bearing levels, significantly refining the local biostratigraphy. Radiometric ages obtained from glass shards from tuff horizons are used together with the biostratigraphic information for constructing and confirming the magnetostratigraphic correlation of the studied sections to the Astronomical Tuned Time Scale (ANTS04; Lourens et al. in Geologic Time Scale 2004, Cambridge University Press, 2004). This correlation implies that the UL lithostratigraphic unit corresponds to the latest Ottnangian and the Early Karpatian, whereas the UF corresponds to the Karpatian and the Early Badenian. This indicates that the Brackish- to Freshwater Molasse transition already occurred during the late Ottnangian. The pre-Riesian hiatus occurred in the latest Karpatian and lower Early Badenian in Eastern Bavaria and Bohemia and in the Late Karpatian and earliest Badenian in Western Bavaria. The geochemical and Ar–Ar data of volcanic ashes suggest that highly evolved silicic magmas from a single volcano or volcanic center, characterized by a uniform Nd isotopic composition, erupted repetitively over the course of at least 1.6 Myr. Three phases of eruptive activity were identified at 16.1 ± 0.2 Ma (Zahling-2), 15.6 ± 0.4 Ma (Krumbad), and 14.5 ± 0.2 Ma (Heilsberg, Hegau). The correlation of the local biostratigraphic zonation to the ANTS04 enables further the characterization of both the Ottnangian–Karpatian and Karpatian–Badenian boundaries in the NAFB by small-mammal biostratigraphy. According to these results the Ottnangian–Karpatian boundary is contemporaneous with the first appearance datum of Megacricetodon bavaricus (in the size of the type population) and the first common occurrence of Keramidomys thaleri, whereas Ligerimys florancei, Melissiodon dominans and Prodeinotherium aff. bavaricum have been already disappeared during the late Ottnangian. The Karpatian–Badenian boundary is characterized by a significant size increase of the large Megacricetodon lineage and possibly a (re-)immigration of Prodeinotherium bavaricum.     

Geophysical exploration on the subsurface geology of La Garrotxa monogenetic volcanic field (NE Iberian Peninsula)

We applied self-potential (SP) and electrical resistivity tomography (ERT) to the exploration of the uppermost part of the substrate geology and shallow structure of La Garrotxa monogenetic volcanic field, part of the European Neogene–Quaternary volcanic province. The aim of the study was to improve knowledge of the shallowest part of the feeding system of these monogenetic volcanoes and of its relationship with the subsurface geology. This study complements previous geophysical studies carried out at a less detailed scale and aimed at identifying deeper structures, and together will constitute the basis to establish volcanic susceptibility in La Garrotxa. SP study complemented previous smaller-scale studies and targeted key areas where ERT could be conducted. The main new results include the generation of resistivity models identifying dykes and faults associated with several monogenetic cones. The combined results confirm that shallow tectonics controlling the distribution of the foci of eruptive activity in this volcanic zone mainly correspond to NNW–SSE and accessorily by NNE–SSW Neogene extensional fissures and faults and concretely show the associated magmatic intrusions. These structures coincide with the deeper ones identified in previous studies, and show that previous Alpine tectonic structures played no apparent role in controlling the loci of this volcanism. Moreover, the results obtained show that the changes in eruption dynamics occurring at different vents located at relatively short distances in this volcanic area are controlled by shallow stratigraphical, structural and hydrogeological differences underneath these monogenetic volcanoes.     

Mineralisation of amethyst-bearing geodes in Ametista do Sul (Brazil) from low-temperature sedimentary brines: evidence from monophase liquid inclusions and stable isotopes

Fluid inclusion studies in combination with hydrogen, oxygen and sulphur isotope data provide novel insights into the genesis of giant amethyst-bearing geodes in Early Cretaceous Paraná continental flood basalts at Amestita do Sul, Brazil. Monophase liquid inclusions in colourless quartz, amethyst, calcite, barite and gypsum were analysed by microthermometry after stimulating bubble nucleation using single femtosecond laser pulses. The salinity of the fluid inclusions was determined from ice-melting temperatures and a combination of prograde and retrograde homogenisation temperatures via the density maximum of the aqueous solutions. Four mineralisation stages are distinguished. In stage I, celadonite, chalcedony and pyrite formed under reducing conditions in a thermally stable environment. Low δ³⁴S_V-CDT values of pyrite (?25 to ?32?‰) suggest biogenic sulphate reduction by organotrophic bacteria. During the subsequent stages II (amethyst, goethite and anhydrite), III (early subhedral calcite) and IV (barite, late subhedral calcite and gypsum), the oxidation state of the fluid changed towards more oxidising conditions and microbial sulphate reduction ceased. Three distinct modes of fluid salinities around 5.3, 3.4 and 0.3 wt% NaCl-equivalent characterise the mineralisation stages II, III and IV, respectively. The salinity of the stage I fluid is unknown due to lack of fluid inclusions. Variation in homogenisation temperatures and in δ¹⁸O values of amethyst show evidence of repeated pulses of ascending hydrothermal fluids of up to 80–90 °C infiltrating a basaltic host rock of less than 45 °C. Colourless quartz and amethyst formed at temperatures between 40 and 80 °C, while the different calcite generations and late gypsum precipitated at temperatures below 45 °C. Calculated oxygen isotope composition of the amethyst-precipitating fluid in combination with δD values of amethyst-hosted fluid inclusions (?59 to ?51?‰) show a significant ¹⁸O-shift from the meteoric water line. This ¹⁸O-shift, high salinities of the fluid inclusions with chloride-sulphate composition, and high δ³⁴S values of anhydrite and barite (7.5 to 9.9?‰) suggest that sedimentary brines from deeper parts of the Guaraní aquifer system must have been responsible for the amethyst mineralisation.