Landscape evolution and depositional processes in the Miocene Amazonian Pebas lake/wetland system: Evidence from exploratory boreholes in northeastern Peru.

This study of the type and scales of depositional processes and landscape development in western Amazonia during the Miocene is based on the description and interpretation of three boreholes from the Marañon basin (Peru). The Miocene Pebas Formation, and the overlying Marañon Formation and underlying Chambira Formation are lithologically characterised. An age calculation model indicates an Oligocene age for the Chambira Formation, and an Early - early Late Miocene age for the Pebas Formation. The base of the Chambira Formation is placed at a sequence boundary and corresponds to the beginning of a regression. The succession was deposited in floodplains included in a RST and a LST under a seasonal climate with a pronounced dry season. The base of the Pebas Formation is placed at a TS. It represents TST and HST lacustrine and swamp settings at or near sealevel, formed in a tropical monsoon climate alike the present-day climate in the region. At the time, the area was a mosaic of lakes, swamps and fluvial belts, but experienced tidal influence as well. During apparently regularly recurring base level highstands, open aquatic settings (lakes at sea level) were widespread. The depositional system was driven by tectonic subsidence in the area, uplift and erosion in the Andean hinterland and the western rim of the Pebas system (the developing Subandean zone), delta lobe switching and river belt avulsions, as well as presumable Milankovitch scale precipitation/erosion cycles and eustatic sea level variation. The base of the Marañon Formation is placed at a sequence boundary. It represents the end of the Pebas lake/wetland system, and the change to permanent fluvial conditions during the Late Miocene RST and LST

Are spherulitic lacustrine carbonates an expression of large-scale mineral carbonation? : A case study from the East Kirkton Limestone, Scotland

BP Exploration Co. is thanked for funding, and particularly the Carbonate Team for supporting this research and for fruitful discussions. West Lothian Council and Scottish Natural Heritage are thanked for allowing access and permission for sampling the site. The Core Store Team at BGS Keyworth is particularly acknowledged for their assistance. Mark Anderson, Tony Sinclair (University of Hull), and Bouk Lacet (VU University Amsterdam) are thanked for technical support. Anne Kelly (SUERC) for carrying out the Strontium Isotope analyses. Mark Tyrer is thanked for his advice on PHREEQC modelling.Peer reviewedPostprin

A test of the biogenicity criteria established for microfossils and stromatolites on quaternary tufa and speleothem materials formed in the “Twilight zone” at Caerwys, UK

© 2015, Mary Ann Liebert, Inc. The ability to distinguish the features of a chemical sedimentary rock that can only be attributed to biology is a challenge relevant to both geobiology and astrobiology. This study aimed to test criteria for recognizing petrographically the biogenicity of microbially influenced fabrics and fossil microbes in complex Quaternary stalactitic carbonate rocks from Caerwys, UK. We found that the presence of carbonaceous microfossils, fabrics produced by the calcification of microbial filaments, and the asymmetrical development of tufa fabrics due to the more rapid growth of microbially influenced laminations could be recognized as biogenic features. Petrographic evidence also indicates that the development of "speleothem-like" laminae was related to episodes of growth interrupted by intervals of nondeposition and erosion. The lack of any biogenic characteristics in these laminae is consistent with their development as a result of variation in the physicochemical parameters that drive calcite precipitation from meteoric waters in such environmental settings

Problems in obtaining precise and accurate Sr isotope analysis from geological materials using laser ablation MC-ICPMS

This paper reviews the problems encountered in eleven studies of Sr isotope analysis using laser ablation multicollector inductively coupled plasma mass spectrometry (LA-MC-ICPMS) in the period 1995–2006. This technique has been shown to have great potential, but the accuracy and precision are limited by: (1) large instrumental mass discrimination, (2) laser-induced isotopic and elemental fractionations and (3) molecular interferences. The most important isobaric interferences are Kr and Rb, whereas Ca dimer/argides and doubly charged rare earth elements (REE) are limited to sample materials which contain substantial amounts of these elements. With modern laser (193 nm) and MC-ICPMS equipment, minerals with >500 ppm Sr content can be analysed with a precision of better than 100 ppm and a spatial resolution (spot size) of approximately 100 μm. The LA MC-ICPMS analysis of 87Sr/86Sr of both carbonate material and plagioclase is successful in all reported studies, although the higher 84Sr/86Sr ratios do suggest in some cases an influence of Ca dimer and/or argides. High Rb/Sr (>0.01) materials have been successfully analysed by carefully measuring the 85Rb/87Rb in standard material and by applying the standard-sample bracketing method for accurate Rb corrections. However, published LA-MC-ICPMS data on clinopyroxene, apatite and sphene records differences when compared with 87Sr/86Sr measured by thermal ionisation mass spectrometry (TIMS) and solution MC-ICPMS. This suggests that further studies are required to ensure that the most optimal correction methods are applied for all isobaric interferences

Carbon, nitrogen, and oxygen stable isotopes in modern tooth enamel: A case study from Gorongosa National Park, central Mozambique

The analyses of the stable isotope ratios of carbon (delta C-13), nitrogen (delta N-15), and oxygen (delta O-18) in animal tissues are powerful tools for reconstructing the feeding behavior of individual animals and characterizing trophic interactions in food webs. Of these biomaterials, tooth enamel is the hardest, most mineralized vertebrate tissue and therefore least likely to be affected by chemical alteration (i.e., its isotopic composition can be preserved over millions of years), making it an important and widely available archive for biologists and paleontologists. Here, we present the first combined measurements of delta C-13, delta N-15, and delta O-18 in enamel from the teeth of modern fauna (herbivores, carnivores, and omnivores) from the well-studied ecosystem of Gorongosa National Park (GNP) in central Mozambique. We use two novel methods to produce high-precision stable isotope enamel data: (i) the "oxidation-denitrification method," which permits the measurement of mineral-bound organic nitrogen in tooth enamel (delta N-15(enamel)), which until now, has not been possible due to enamel's low organic content, and (ii) the "cold trap method," which greatly reduces the sample size required for traditional measurements of inorganic delta C-13(enamel) and delta O-18(enamel) (from >= 0.5 to <= 0.1 mg), permitting analysis of small or valuable teeth and high-resolution serial sampling of enamel. The stable isotope results for GNP fauna reveal important ecological information about the trophic level, dietary niche, and resource consumption. delta N-15(enamel) values clearly differentiate trophic level (i.e., carnivore delta N-15(enamel) values are 4.0 parts per thousand higher, on average, than herbivores), delta C-13(enamel) values distinguish C-3 and/or C-4 biomass consumption, and delta O-18(enamel) values reflect local meteoric water (delta O-18(water)) in the park. Analysis of combined carbon, nitrogen, and oxygen stable isotope data permits geochemical separation of grazers, browsers, omnivores, and carnivores according to their isotopic niche, while mixed-feeding herbivores cannot be clearly distinguished from other dietary groups. These results confirm that combined C, N, and O isotope analyses of a single aliquot of tooth enamel can be used to reconstruct diet and trophic niches. Given its resistance to chemical alteration, the analysis of these three isotopes in tooth enamel has a high potential to open new avenues of research in (paleo)ecology and paleontology.info:eu-repo/semantics/publishedVersio

Production of ultrasonic vocalizations by Peromyscus mice in the wild

BACKGROUND: There has been considerable research on rodent ultrasound in the laboratory and these sounds have been well quantified and characterized. Despite the value of research on ultrasound produced by mice in the lab, it is unclear if, and when, these sounds are produced in the wild, and how they function in natural habitats. RESULTS: We have made the first recordings of ultrasonic vocalizations produced by two free-living species of mice in the genus Peromyscus (P. californicus and P. boylii) on long term study grids in California. Over 6 nights, we recorded 65 unique ultrasonic vocalization phrases from Peromyscus. The ultrasonic vocalizations we recorded represent 7 different motifs. Within each motif, there was considerable variation in the acoustic characteristics suggesting individual and contextual variation in the production of ultrasound by these species. CONCLUSION: The discovery of the production of ultrasonic vocalizations by Peromyscus in the wild highlights an underappreciated component in the behavior of these model organisms. The ability to examine the production of ultrasonic vocalizations in the wild offers excellent opportunities to test hypotheses regarding the function of ultrasound produced by rodents in a natural context

Moving from contractor to owner operator: Impact on safety culture; a case study

Purpose – The purpose of this paper is to investigate whether a change in staffing contractual arrangements, specific training in hazard identification, mentoring of supervisors and the introduction of a robust safety system could improve an organisation\u27s safety culture. How safety conditions change under contracted out labour compared to direct labour and the influence that contracting out has on organisational safety culture is explored. Design/methodology/approach – The study used a case study methodology to detail how the change occurred over a six month period in 2011. As part of the analysis a model of the change process and push-pull factors is offered. Findings – As a result of the change, all areas saw some improvement. Work-related injury statistics dropped significantly, supervisors were clear of their roles, actively monitoring their crews to ensure they worked in a safer manner than before, and staff were actively addressing work-place hazards. With the safety system in place the organisation should be deemed compliant and diligent by the state auditing authorities. This study has also shown that using contractor workers together with in-house workers that are managed under different safety regimes is problematic. The problems don’t occur due to the contractor\u27s safety systems being less robust than the parent company\u27s or that contract workers are themselves less safe; it is the added complexity of managing multiple safety regimes and the lack of trust of the robustness of each system that create conflict. Research limitations/implications – The paper reports on the change process of one mining organisation in Western Australia as a case study from a managerial sample and is thereby limited. Practical implications – This study demonstrates the difficulties in changing safety culture in an underground mining organisation. The paper argues the need for specialised training in identifying hazards by the staff, the mentoring of supervisory staff and the adoption of a robust safety system to support improved safety culture. Originality/value – There is little research conducted in the resources sector researching changes in human resource supply and OHS management, in particular moving from contracted labour to hiring in-house. This case provides an insight into how a change in staffing hiring arrangements, together with specific safety initiatives, has a positive impact on safety performance