Proterozoic seawater — felsic volcanics interaction W. Bergslagen,Sweden. Evidence for high REE mobility and implications for 1.8 Ga seawater compositions

Mg enrichment in diffusely bounded, schistose alteration zones occurring in Proterozoic submarine felsic volcanics NE of Hjulsjö, W. Bergslagen is shown to result from felsic rock-seawater interaction in a sub-seafloor hydrothermal system. The alteration is apparently in two stages, feldspar being altered first to a kaolinite-type clay which is then replaced by Mg-chlorite. Major and trace element data are presented for the schist and sheridanite (chlorite). Relative to the least altered felsic volcanics, and for negligible volume change, the schist shows strong addition of Mg and to a lesser extent Si; K, Al and Rb are apparently conserved, while most other elements are strongly depleted, including the REEs which are removed for ～75%, indicating a high degree of mobility. The chlorite, with its HREE enriched pattern, is considered to have equilibrated with the hydrothermal fluid, which consisted predominantly of seawater. Comparison with modern seawater leads to the tentative conclusion that the Proterozoic seawater HREE composition was not drastically different from that of modern seawater.     

Incidental capture of diamondback terrapin by crab pots

Two-hundred eighty-one diamondback terrapins (195♂, 86♀) were captured in baited and unbaited crab pots during premolt crab capture studies in South Carolina. Sampling was conducted four consecutive days each week from mid April to mid November, 1979, in the Ashley River estuary, and daily from April to July, 1980 and 1981, in the Wando River estuary. Fifty-five percent of the total were captured in April, and 32% in May. Males outnumbered females 2.3∶1, but this ratio may reflect crab pot entrance bias which restricted entry of large females. Median plastron length of females was 121 mm (range 76–175) and that for males 100 mm. (range 79–128); only two male terrapins equalled or exceeded the minimum legal size limit of 127 mm. Few captured terrapins were drowned when crab pots were checked daily, and it is estimated that capture mortality amounted to 10%. Terrapin catch per baited crab pot averaged 0.16 daily in April and May. Incidental terrapin capture by 743 commercial crabbers (fiscal year 1982 numbers) in South Carolina during April and May was estimated at 2,853 daily, and mortality was estimated at 285. These estimates are exclusive of mortalities resulting from lost pots. The impact of crabbing activities is believed to pose no threat to the terrapin population at current levels of commercial terrapin harvest. Because female terrapins mature at the minimum legal size, no segment of the egg laying population is protected except seasonally. If direct harvest of terrapins ever approaches that of the early twentieth century, then it is recommended that legal size limits be changed to protect a segment of the mature female population.     

The weathering of a late Tertiary volcanic ash: Importance of organic solutes

The weathering of a late Tertiary volcanic ash near Jackson, Wyoming, was studied by sampling water percolating through the ash with suction lysimeters, and by examination of the associated solid phases. Soluble organic compounds derived from vegetation control the release and transport of solutes by complexing Al and Fe, and by causing low pH values. The concentrations of Na, K, Ca, and Mg, as well as those of Al and Fe correlate with the dissolved organic carbon concentrations (DOC) and follow an annual cycle with a maximum in spring. DOC concentrations averaged 5O mg C per liter, and values as high as 260 mg/l were observed. Al and Fe concentrations ranged as high as 5 mg/l. The dissolved organic matter was largely in the form of humic acids, although minor amounts of oxalate, acetate, and formate were also present. The pH of the percolating waters ranged from 4.3 to 6.5 with a mean of 5.2.During laboratory weathering experiments with the same ash in the absence of dissolved organic compounds, pH values ranged from 7.3 to 9.5, dissolved Al and Fe concentrations were below the detection limit, and there was little resemblance between the compositions of the solutions and the compositions observed in the field. Any model attempting to describe weathering in a comparable setting must incorporate biological mechanisms as the dominant controls.     

Precambrian subcommission meets in Tanta,Egypt

Criteria of biogenicity of microspheroidal objects, which have been interpreted as microfossils, are here reviewed in the light of additional data. Much weight has been placed by some commentators on constrained heterogeneity as a primary criterion of biogenicity. The data from the field and laboratory suggest the need for continuing reservation in the interpretation of these objects. On the basis of these and other data, reasons are given for the alternative explanation that the objects are lithified relics of protobiotic assemblages. The question remains open as to whether the early Archean spheroidal objects are abiotic, protobiotic, or biotic in origin.     

Risk Management for Petroleum Reservoir Production: A Simulation-Based Study of Prediction

We consider numerical solutions of the Darcy and Buckley–Leverett equations for flow in porous media. These solutions depend on a realization of a random field that describes the reservoir permeability. The main content of this paper is to formulate and analyze a probability model for the numerical coarse grid solution error. We explore the extent to which the coarse grid oil production rate is sufficient to predict future oil production rates. We find that very early oil production data is sufficient to reduce the prediction error in oil production by about 30%, relative to the prior probability prediction.     

Regional Energy Demand Responses To Climate Change: Methodology And Application To The Commonwealth Of Massachusetts

Climate is a major determinant of energy demand. Changes in climate may alter energy demand as well as energy demand patterns. This study investigates the implications of climate change for energy demand under the hypothesis that impacts are scale dependent due to region-specific climatic variables, infrastructure, socioeconomic, and energy use profiles. In this analysis we explore regional energy demand responses to climate change by assessing temperature-sensitive energy demand in the Commonwealth of Massachusetts. The study employs a two-step estimation and modeling procedure. The first step evaluates the historic temperature sensitivity of residential and commercial demand for electricity and heating fuels, using a degree-day methodology. We find that when controlling for socioeconomic factors, degree-day variables have significant explanatory power in describing historic changes in residential and commercial energy demands. In the second step, we assess potential future energy demand responses to scenarios of climate change. Model results are based on alternative climate scenarios that were specifically derived for the region on the basis of local climatological data, coupled with regional information from available global climate models. We find notable changes with respect to overall energy consumption by, and energy mix of the residential and commercial sectors in the region. On the basis of our findings, we identify several methodological issues relevant to the development of climate change impact assessments of energy demand.     

Robustness of Recommended Farm Plans in England under Climate Change: A Monte Carlo Simulation

A methodology is described for estimating robustness of recommended farm plans under climate change while maintaining a meaningful representation of the underlying farm system. Monte Carlo Simulation (MCS) of crop yield data is used in conjunction with a fully specified farm-level model and output from a field worktime model. Estimates of farm net margin, enterprise mix (choice and area of enterprises), labour, machinery, storage and animal housing under mean crop yields and field worktimes for current (2000s) and 2050s conditions are generated. MCS is used to estimate the effect of crop yield variation on farm profitability and enterprise mix for the same periods by running the farm-level model with no constraints and running it constrained to the mean data plan. Estimates of robustness, measured as the percentage difference and the probability of exceeding the mean farm net-margin, were calculated from the outputs from these runs. For three representative farm types, mean farm net margin increased; however changes in robustness as shown by percentage difference in farm net margin depended on farm type while the probability of exceeding the mean plan net-margin decreased by 2050 indicating an increase in robustness. The most robust farm type had a diversified mix of enterprises and required no additional fixed resources by the 2050s. The least robust farm type was in a marginal location and mean plan recommendations for the 2050s required additional investment in fixed resources, particularly irrigation. It is concluded that the information provided by the methodology would be particularly useful to farmers: where mean data plans are not robust, MCS results could be used with financial planning techniques to minimise the impact of variability, rather than using high cost inputs to reduce variability per se.     

Reduced complexity strategies for modelling urban floodplain inundation

Significant advances in flood inundation modelling have been made in the last decade through the use of a new generation of 2D hydraulic numerical models. These offer the potential to predict the local pattern and timing of flood depth and velocity, enabling informed flood risk zoning and improved emergency planning. With the availability of high resolution DEMs derived from airborne lidar, these models can theoretically now be routinely parameterized to represent considerable topographic complexity, even in urban areas where the potential exists to represent flows at the scale of individual buildings. Currently, however, computational constraints on conventional finite element and volume codes typically require model discretization at scales well below those achievable with lidar and are thus unable to make optimal use of this emerging data stream.In this paper we review two strategies that attempt to address this mismatch between model and data resolution in an effort to improve urban flood forecasts. The first of these strives for a solution by simplifying the mathematical formulation of the numerical model by using a computationally efficient 2D raster storage cell approach coupled to a 1D channel model. This parsimonious model structure enables simulations over large model domains offering the opportunity to employ a topographic discretization strategy which explicitly represents the built environment. The second approach seeks to further reduce the computational overhead of this raster method by employing a subgrid parameterization to represent the effect of buildings and micro-relief on flow pathways and floodplain storage. This multi-scale methodology enables highly efficient model applications at coarse spatial resolutions while retaining information about the complex geometry of the built environment.These two strategies are evaluated through numerical experiments designed to reconstruct a flood in the small town of Linton in southern England, which occurred in response to a 1 in 250 year rainfall event in October 2001. Results from both approaches are encouraging, with the spatial pattern of inundation and flood wave propagation matching observations well. Both show significant advantages over a coarse resolution model without subgrid parameterisation, particularly in terms of their ability to reproduce both hydrograph and inundation depth measurements simultaneously, without need for recalibration. The subgrid parameterization is shown to achieve this without contributing significant computational complexity and reduces model run-times by an order of magnitude.     

Geomorphic constraints on the active tectonics of southern Taiwan

Taiwan is a region of rapid active tectonics, yet the study of the tectonic processes that shape the interior of the island is difficult due to the high rates of erosion and dense vegetation. We use digital topography to look for indications of active deformation preserved in the local geomorphology. In particular, anomalies in the regional pattern of drainage are used to infer zones of enhanced tectonic activity. The apparent anticlockwise rotation of major river systems in plan view indicates the presence of a diffuse zone of left-lateral shear running down the southeastern side of Taiwan. Asymmetries in the catchments of individual drainage basins show the influence of varying rates of uplift across southern Taiwan, with the most rapid uplift close to Taitung at the indentation point of the Luzon arc with the Chinese continental margin. Our interpretations, though based predominantly on remote-sensing observations, are consistent with the available field evidence. This study demonstrates the usefulness of drainage basins as tectonic markers in the quantification of regional strain and uplift, which may have wider applicability in other deforming parts of the world.