Depositional processes across the Sinú Accretionary Prism,offshore Colombia

The Pliocene to Recent of the Sinú Accretionary Prism, offshore Colombia, features gravity current dominated basins characterised primarily by channel- and sheet-like architectures and those with dominantly hemipelagic fills. The prism is fed by rivers that drain from uplifted older basins and volcanic Andean terranes to the south and east which source large volumes of sediment to the Colombian Shelf into the Colombian Basin. Some basin fills show evidence of both localised fold-induced sediment failure and regional-scale shelf collapse, both related to the generation and destruction of oversteepened slopes. Large scale collapses can create new sediment routing pathways and/or local depocentres into which sediment subsequently accumulates. In the Colombian Basin, even relatively distal basins show evidence of channel activity related primarily to the creation of new sediment distribution pathways through breaches in the substrate barriers between basins. These channels are often orientated parallel to the regional drainage trend, suggesting that regional sediment transport trends can assert themselves relatively early in a basin filling history regardless of the local bathymetric grain. While, at a regional scale, sediment dispersal fairways reflect drainage from the continental shelf to the basin floor, intraslope basins form local bathymetric obstructions that can drive local spatial variations in sediment distribution. Thus, both local and regional length scales of bathymetric control are evident within the intraslope basins of the Sinú Accretionary Prism. Although regional dispersal patterns generally become more important in time, individual intraslope basins exhibit more complex filling histories because events such as sill or shelf collapse may serve to disrupt established distribution pathways, initiating repeated episodes of adjustment.     

Inter‐comparison of hydro‐climatic regimes across northern catchments: synchronicity,resistance and resilience

The higher mid‐latitudes of the Northern Hemisphere are particularly sensitive to climate change as small differences in temperature determine frozen ground status, precipitation phase, and the magnitude and timing of snow accumulation and melt. An international inter‐catchment comparison program, North‐Watch, seeks to improve our understanding of the sensitivity of northern catchments to climate change by examining their hydrological and biogeochemical responses. The catchments are located in Sweden (Krycklan), Scotland (Mharcaidh, Girnock and Strontian), the United States (Sleepers River, Hubbard Brook and HJ Andrews) and Canada (Catamaran, Dorset and Wolf Creek). This briefing presents the initial stage of the North‐Watch program, which focuses on how these catchments collect, store and release water and identify ‘types’ of hydro‐climatic catchment response. At most sites, a 10‐year data of daily precipitation, discharge and temperature were compiled and evaporation and storage were calculated. Inter‐annual and seasonal patterns of hydrological processes were assessed via normalized fluxes and standard flow metrics. At the annual‐scale, relations between temperature, precipitation and discharge were compared, highlighting the role of seasonality, wetness and snow/frozen ground. The seasonal pattern and synchronicity of fluxes at the monthly scale provided insight into system memory and the role of storage. We identified types of catchments that rapidly translate precipitation into runoff and others that more readily store water for delayed release. Synchronicity and variance of rainfall–runoff patterns were characterized by the coefficient of variation (cv) of monthly fluxes and correlation coefficients. Principal component analysis (PCA) revealed clustering among like catchments in terms of functioning, largely controlled by two components that (i) reflect temperature and precipitation gradients and the correlation of monthly precipitation and discharge and (ii) the seasonality of precipitation and storage. By advancing the ecological concepts of resistance and resilience for catchment functioning, results provided a conceptual framework for understanding susceptibility to hydrological change across northern catchments. Copyright © 2010 John Wiley & Sons, Ltd.     

The dynamic strength of an ordinary chondrite

Abstract– Dynamic and quasistatic unconfined compression experiments were performed on samples of the L5 ordinary chondrite MacAlpine Hills (MAC) 88118. The dynamic compressive strength measurements are the first of its kind for a stony meteorite, and indicate that the material tested here exhibits significant increase in compressive strength with increasing strain rate. This increase in compressive strength is larger than the increases typically observed in terrestrial rock specimens compressed over a similar range of strain rates. The details of the failure process are investigated by recording images of the experiments in real time. Specifically, the crack growth speeds in the dynamic compression experiments are measured from ultrahigh‐speed images. These speeds are significantly lower than the speeds observed in terrestrial analogs that are typically used in numerical investigations of large‐scale impacts. The implications of these measurements of strength and failure process are explored in the contexts of atmospheric disruption of meteors and impact cratering/disruption of asteroids.     

Modeling the integrated roles of insurance and retrofit in managing natural disaster risk: a multi-stakeholder perspective

This paper introduces a new modeling framework to understand and improve regional natural disaster risk management in the USA, including the interactions among key stakeholders and between the two important risk management mechanisms of insurance and retrofit. The framework includes a stochastic programming optimization to represent insurer decisions, which interacts with a utility-based model of individual homeowners’ decisions to insure and/or retrofit. Reinsurer and government roles are represented as inputs, and the decision models are integrated with a detailed regional catastrophe loss estimation model. This modeling framework is applied to a full-scale, realistic case study for hurricane risk to residential buildings in Eastern North Carolina. Several alternative system configurations are considered that affect the incentives for adoption of alternative risk management methods. They include providing a government subsidy for insured homeowners to encourage retrofit, providing both a government subsidy and insurance rebate to reduce retrofit costs, and mandating insurance purchase with a cap on insurance premiums. For each configuration, outcomes are presented from the perspectives of all key stakeholders—primary insurer, homeowners (insured and uninsured, in high- and low-risk areas), reinsurers, and the government. Results suggest that it is possible to design policies in which all stakeholders can be better off simultaneously. Retrofit incentives for insured homeowners can be effective in linking and strengthening the benefits of retrofit and insurance. Mandatory insurance coupled with capped profit loading factors and possibly retrofit rebates from the insurer to the homeowner can also reduce overall system risk.     

Experimental Set-up for Determining Soil Water Retention Curves for Granular Soils During Drying

Abstract: Soil water retention curves (SWRCs) provide an important means of describing the response of unsaturated soils during drying / wetting processes in terms of variations of degree of saturation, water content or void ratio with suction. A key consideration in generating these curves is how to measure the suction. Frequently the filter paper technique is adopted, especially when high suctions are developed, e.g. with plastic clays. As each measurement takes at least a week with this technique, it can take months or years to generate a full SWRC in drying and wetting. Developments in laboratory tensiometers now allow matrix suctions up to about 1.5 MPa to be measured. With such a device it is possible to develop SWRCs for granular soils such as silts and clays in hours or days by continuous measurement. This paper describes an experimental set-up that was developed to measure changes in volume, water content and matrix suction during drying of three granular soils. Limitations of the apparatus and usefulness of the curves are discussed.     

Hydrology and water quality in two mountain basins of the northeastern US: assessing baseline conditions and effects of ski area development

Mountain regions throughout the world face intense development pressures associated with recreational and tourism uses. Despite these pressures, much of the research on bio‐geophysical impacts of humans in mountain regions has focused on the effects of natural resource extraction. This paper describes findings from the first 3 years of a study examining high elevation watershed processes in a region undergoing alpine resort development. Our study is designed as a paired‐watershed experiment. The Ranch Brook watershed (9·6 km²) is a relatively pristine, forested watershed and serves as the undeveloped ‘control’ basin. West Branch (11·7 km²) encompasses an existing alpine ski resort, with approximately 17% of the basin occupied by ski trails and impervious surfaces, and an additional 7% slated for clearing and development. Here, we report results for water years 2001–2003 of streamflow and water quality dynamics for these watersheds. Precipitation increases significantly with elevation in the watersheds, and winter precipitation represents 36–46% of annual precipitation. Artificial snowmaking from water within West Branch watershed currently augments annual precipitation by only 3–4%. Water yield in the developed basin exceeded that in the control by 18–36%. Suspended sediment yield was more than two and a half times greater and fluxes of all major solutes were higher in the developed basin. Our study is the first to document the effects of existing ski area development on hydrology and water quality in the northeastern US and will serve as an important baseline for evaluating the effects of planned resort expansion activities in this area. Published in 2007 by John Wiley & Sons, Ltd.     

UV photolysis of quinoline in interstellar ice analogs

Abstract— The polycyclic aromatic nitrogen heterocycle (PANH) quinoline (C₉H₇N) was frozen at 20 K in interstellar ice analogs containing either pure water or water mixed with methanol or methane and exposed to ultraviolet (UV) radiation. Upon warming, the photolysis products were analyzed by high‐performance liquid chromatography and nanoscale liquid chromatography‐electrospray ionization mass spectrometry. A suite of hydroxyquinolines, which were formed by the addition of oxygen atoms to quinoline, was observed as the primary product in all the ices. Quinoline N oxide was not formed, but five hydroxyquinoline isomers were produced with no clear dominance of one isomer. Reduction products, formed by hydrogen atom addition, were also created. Ices created at 20 K with H₂O: quinoline ratios of 10:1 to 100:1 showed similar product distributions to those at 122 K, with no apparent temperature or concentration dependence. Increasing the UV dose led to a decrease in overall yield, indicating that quinoline and its products may be photo‐destroyed. Methylquinolines were formed upon photolysis of the methanol‐ and methane‐containing ices. In addition, possible methoxyquinolines or quinoline methylene alcohols were formed in the methanol‐containing ice, while methylhydroxyquinolines were created in the methane‐containing ice. This work indicates that oxidation of PANHs could occur in icy extraterrestrial environments and suggests that a search for such compounds in carbonaceous meteorites could illuminate the possible link between interstellar ice chemistry and meteoritic organics. Given the importance of oxidized and alkylated PANHs to biochemistry, the formation and delivery of such molecules to the early Earth may have played a role in the origin and evolution of life.     

Indigenous aliphatic amines in the aqueously altered Orgueil meteorite

The CI1 Orgueil meteorite is a highly aqueously altered carbonaceous chondrite. It has been extensively studied, and despite its extensive degree of aqueous alteration and some documented instances of contamination, several indigenous organic compounds including amino acids, carboxylic acids, and nucleobases have been detected in its carbon‐rich matrix. We recently developed a novel gas chromatographic method for the enantiomeric and compound‐specific isotopic analyses of meteoritic aliphatic monoamines in extracts and have now applied this method to investigate the monoamine content in Orgueil. We detected 12 amines in Orgueil, with concentrations ranging from 1.1 to 332 nmol g^?1 of meteorite and compared this amine content in Orgueil with that of the CM2 Murchison meteorite, which experienced less parent‐body aqueous alteration. Methylamine is four times more abundant in Orgueil than in Murchison. As with other species, the amine content in Orgueil extracts shows less structural diversity than that in Murchison extracts. We measured the compound‐specific stable carbon isotopic ratios (δ¹³C) for 5 of the 12 monoamines detected in Orgueil and found a range of δ¹³C values from –20 to +59‰. These δ¹³C values fall into the range of other meteoritic organic compounds, although they are ¹³C‐depleted relative to their counterparts extracted from the Murchison meteorite. In addition, we measured the enantiomeric composition for the chiral monoamines (R)‐ and (S)‐sec‐butylamine in Orgueil, and found it was racemic within experimental error, in contrast with the l ‐enantiomeric excess found for its amino acid structural analog isovaline. The racemic nature of sec‐butylamine in Orgueil was comparable to that previously observed in Murchison, and to other CM2 and CR2 carbonaceous chondrites measured in this work (ALH 83100 [CM1/2], LON 94101 [CM2], LEW 90500 [CM2], LAP 02342 [CR2], and GRA 95229 [CR2]). These results allow us to place some constraints on the effects of aqueous alteration observed over the monoamine concentrations in Orgueil and Murchison, and to evaluate the primordial synthetic relationships between meteoritic monoamines and amino acids.     

Amino acid analyses of R and CK chondrites

Exogenous delivery of amino acids and other organic molecules to planetary surfaces may have played an important role in the origins of life on Earth and other solar system bodies. Previous studies have revealed the presence of indigenous amino acids in a wide range of carbon‐rich meteorites, with the abundances and structural distributions differing significantly depending on parent body mineralogy and alteration conditions. Here we report on the amino acid abundances of seven type 3–6 CK chondrites and two Rumuruti (R) chondrites. Amino acid measurements were made on hot water extracts from these meteorites by ultrahigh‐performance liquid chromatography with fluorescence detection and time‐of‐flight mass spectrometry. Of the nine meteorites analyzed, four were depleted in amino acids, and one had experienced significant amino acid contamination by terrestrial biology. The remaining four, comprised of two R and two CK chondrites, contained low levels of amino acids that were predominantly the straight chain, amino‐terminal (n‐ω‐amino) acids β‐alanine, and γ‐amino‐n‐butyric acid. This amino acid distribution is similar to what we reported previously for thermally altered ureilites and CV and CO chondrites, and these n‐ω‐amino acids appear to be indigenous to the meteorites and not the result of terrestrial contamination. The amino acids may have been formed by Fischer–Tropsch‐type reactions, although this hypothesis needs further testing.