Lower Cambrian patch reefs and associated sediments: southern Labrador, Canada

The complex pattern of biological accretion, internal sedimentation, early lithification, and biological destruction, that characterizes modern reefs and many fossil reefs has been recognized in archaeocyathid-rich patch reefs of Lower Cambrian age in the Forteau Formation, southern Labrador. Patch reefs occur as isolated masses or complex associations of many discrete masses of archaeocyathid-rich limestone and skeletal lime sands, surrounded by well-bedded skeletal limestones and shales. Each reef is composed of many loafshaped mounds stacked on top of one another. The limestone of each mound comprises archaeocyathids and Renalcis or Renalcis-like structures in a matrix of argillaceous lime mud rich in sponge spicules, trilobite and salterellid skeletons. Numerous growth cavities roofed by pendant Renalcis-like organisms and Renalcis are partially to completely filled with geopetal sediment indicating that much of the matrix was deposited as internal sediment. Two stages of diagenetic alteration are recognized: (1) syn-depositional, which affected only the reefs, and (2) post-depositional, which affected both reefs and inter-reef sediments. On the sea floor reef sediments were pervasively cemented and fibrous carbonate was precipitated in intraskeletal and growth cavities. These limestones and cements as well as archaeocyathid skeletons, were subsequently bored by endolithic organisms. Later post-depositional subaerial diagenesis resulted first in dissolution of certain skeletons and precipitation of calcite cement above the water table, followed by extensive precipitation of pore-filling calcite below the water table. These carbonate reefs are similar in structure to the basal pioneer accumulations of much younger lower and middle Palaeozoic reefs. They did not develop into massive ‘ecologic’ reefs because archaeocyathids never developed the necessary large, massive, hemispherical skeletons. This occurrence indicates that reefs developed more or less coincident with, and not long after, the appearance of skeletal metazoans in the Lower Cambrian.     

GIS and SBF for estimating groundwater recharge of a mountainous basin in the Wu River watershed,Taiwan

The temporal and spatial distributions of precipitation are extremely uneven; so, careful management of water resources in Taiwan is crucial. The long-term overexploitation of groundwater resources poses a challenge to water resource management in Taiwan. However, assessing groundwater resources in mountainous basins is challenging due to limited information. In this study, a geographic information system (GIS) and stable base-flow (SBF) techniques were used to assess the characteristics of groundwater recharge considering the Wu River watershed in central Taiwan as a study area. First, a GIS approach was used to integrate five contributing factors: lithology, land cover/land use, lineaments, drainage, and slope. The weights of factors contributing to the groundwater recharge were obtained from aerial photos, geological maps, a land use database, and field verification. Second, the SBF was used to estimate the groundwater recharge in a mountainous basin scale. The concept of the SBF technique was to separate the base-flow from the total streamflow discharge in order to obtain a measure of groundwater recharge. The SBF technique has the advantage of integrating groundwater recharge across an entire basin without complex hydro-geologic modelling and detailed knowledge of the soil characteristics. In this study, our approach for estimating recharge provides not only an estimate of how much water becomes groundwater, but also explains the characteristics of a potential groundwater recharge zone.     

Origin and significance of mud-filled incised valleys (Upper Cretaceous) in southern Alberta, Canada

Seven mud-filled incised valleys (MFIVs) in the paralic facies of the Dinosaur Park and Horseshoe Canyon formations (Upper Cretaceous) of southern Alberta were studied to better understand their morphology, geometry and depositional histories in an estuarine context. Two preservational geometries occur: simple, U-shaped forms; and internally complex forms. Both types of MFIV record deposition in the central zone of low energy (turbidity) in an estuarine setting. Simple, U-shaped MFIVs have sharp basal erosional surfaces and consist of mudstone-dominated heterolithic fills of channel-wide, concave-up laminae. Associated fossil assemblages are marine to brackish. Each simple MFIV records a cut-and-fill history associated with a cycle of relative sea-level drop and rise. Low-energy depositional settings, loss of channel form during infilling, and associated shoreface deposits, as well as the absence of clear tidal indicators suggest a coastal plain estuarine setting, along a wave-dominated, barred coastline. Complex MFIVs are rarer, and consist of imbricated, wedge-shaped sets of inclined-to-horizontal heterolithic strata. Tidal deposits and/or nonmarine-to-marine macrofossils occur locally. Complex MFIVs were infilled in meandering reaches of the central zone of low energy in tide-dominated estuaries. Their rarity compared to simple MFIVs and their freshwater palaeontological content suggest that they were contiguous landward with extensive fluvial channels. A complex MFIV near Onefour comprises three in-channel depositional cycles. Each cycle consists of an erosional surface overlain by lateral accretion bedding and a conformable transition to vertically aggraded strata. Each cycle reflects a cut-and-fill event under the control of changes in relative sea-level that culminated in overbank flooding. All MFIVs formed in low-gradient settings (≤0.03%) where estuarine zones were stretched out over many tens of kilometres. Tide-dominated estuaries apparently exhibited simple, straight-to-meandering upstream transitions and extensive landward penetration (≥200 km) of tidal backwater effects. Few modern estuaries serve as adequate modern analogues to these ancient, tide-dominated estuaries. Radiometric data indicate that MFIV cut-and-fill cycles were 100 000-400 000 years in maximum duration and thus, equivalent to 4th order sea-level cycles. However, negative evidence tentatively suggests that these cycles took place over time intervals 1-2 orders of magnitude smaller (5th order or higher sea-level cycles).     

Improvement in Background Error Covariances Using Ensemble Forecasts for Assimilation of High-Resolution Satellite Data

Satellite data obtained over synoptic data-sparse regions such as an ocean contribute toward improving the quality of the initial state of limited-area models. Background error covariances are crucial to the proper distribution of satellite-observed information in variational data assimilation. In the NMC (National Meteorological Center) method, background error covariances are underestimated over data-sparse regions such as an ocean because of small differences between different forecast times. Thus, it is necessary to reconstruct and tune the background error covariances so as to maximize the usefulness of the satellite data for the initial state of limited-area models, especially over an ocean where there is a lack of conventional data. In this study, we attempted to estimate background error covariances so as to provide adequate error statistics for data-sparse regions by using ensemble forecasts of optimal perturbations using bred vectors. The background error covariances estimated by the ensemble method reduced the overestimation of error amplitude obtained by the NMC method. By employing an appropriate horizontal length scale to exclude spurious correlations, the ensemble method produced better results than the NMC method in the assimilation of retrieved satellite data. Because the ensemble method distributes observed information over a limited local area, it would be more useful in the analysis of high-resolution satellite data. Accordingly, the performance of forecast models can be improved over the area where the satellite data are assimilated.     

An Engineering Application Tool for Visual Assessment of the Equilibrium Beach

An engineering application tool for prediction of the static equilibrium bay(Beach Mod)is established to describe two bay shape formulas by use of the programming software "MATLAB" with a graphic user interface(GUI).The tool is user-friendly for engineering students for the design of beach shapes.This tool was tested through application on three types of beaches in Taiwan and Australia.By implementing the concept of Headland Control,the Beach Mod program allows users to draw a structure and create an artificial headland.The results indicate that Beach Mod can efficiently forecast beach changes as well as MEPBAY,a competing software package,while boasting a better user interface.     

Multivariate analysis of fluorescence and source identification of dissolved organic matter in Jiaozhou Bay, China

Hierarchical clustering analysis and principal component analysis (PCA) methods were used to assess the similarities and dissimilarities of the entire Excitation-emission matrix spectroscopy (EEMs) data sets of samples collected from Jiaozhou Bay, China. The results demonstrate that multivariate analysis facilitates the complex data treatment and spectral sorting processes, and also enhances the probability to reveal otherwise hidden information concerning the chemical characteristics of the dissolved organic matter (DOM). The distribution of different water samples as revealed by multivariate results has been used to track the movement of DOM material in the study area, and the interpretation is supported by the results obtained from the numerical simulation model of substance tracing technique, which show that the substance discharged by Haibo River can be distributed in Jiaozhou Bay.     

西江干流河水主要离子及锶同位素地球化学组成特征

水环境中锶（Sr）含量及其同位素组成特征的研究有助于认识区域水文地球化学特征及流域盆地岩石风化速率等地球化学行为,因此河流环境中Sr的地球化学行为是地球化学研究的重要课题之一。对中国南方西江干流及其支流河水主要阴阳离子及sr同位素组成进行了分析,发现其水化学组成主要以Ca^2＋、Mg^2＋、HCO3^-和SO4^2-离子为主,分别占阴阳离子组成的80％以上。郁江河水具有较高的Sr同位素比值（^87St／^86Sr=0．71049）和较低的Sr含量（0．0263mg／L）,而西江河水具有较低的Sr同位素比值以及较高的Sr含量,其Sr含量变化范围在0．0667．0．187mg／L之间,平均含量为0．136mg／L;Sr同位素比值变化范围在0．70856．0．70936之间,平均比值为0．70894。与世界主要河流水体中Sr含量平均值（0．078mg／L）及Sr同位素比值（^87Sr／^86Sr=0．7119）相比,西江干流水体具有较高的Sr含量及较低的Sr同位素比值。两条河流河水中主要离子及Sr的来源存在显著差异,西江干流河水中的主要溶解离子及Sr同位素主要源于碳酸盐岩（石灰岩和白云岩）的风化作用,主要受黔江及其上游红水河等化学组成所控制,而郁江则主要受碎屑岩风化作用的影响;同时,中上游地区的酸沉降及人类活动的输入可能导致西江干流水体受到一定程度的污染,而郁江受污染程度则相对较小。     

Combined flow origin of edgewise intraclast conglomerates: Sellick Hill Formation (Lower Cambrian), South Australia

Unusually thick, coarse grained edgewise intraclast conglomerates occur at eight or more horizons within subtidal nodular and ribbon bedded wackestones and packstones of the Lower Cambrian Sellick Hill Formation, South Australia. The intraclast beds are flat based and laterally discontinuous, forming bar-like structures that must have exhibited bathymetric relief of as much as 1 m. The internal fabrics of these beds are variable. Thinner beds are dominated by flat-lying intraclasts; thicker beds contain both chaotic, randomly oriented, steeply inclined intraclasts and clusters of fan-shaped, vertically stacked edgewise intraclasts. The Sellick Hill Formation intraclast conglomerates are inferred to have been formed by intense, storm-generated combined flows on a broad, subtidal carbonate ramp. Superimposition of wave-induced oscillatory motions on geostrophic bottom flows during large storms generates short-lived, but exceptionally high instantaneous shear stresses in the bottom boundary layer. Entrainment of the relatively large intraclasts occurs through sliding, rather than pivoting. Edgewise fabrics are a product of asymmetric acceleration and deceleration of intraclasts during passage of waves and the chaotic nature of collisions between intraclasts moving within the boundary layer. Collisions between intraclasts impart a rotating moment, causing intraclasts to tip up during maximum fluid shear stress. Lodgement or packing of clasts in vertical or steeply inclined positions occurs within scours, where intraclasts can wedge between other vertically inclined clasts, or where intraclasts are pinned in steep orientations by collisions with shallowly inclined intraclasts. Differential erosional resistance of the intraclast deposits probably led to the development of sharp lateral changes in thickness. The Sellick Hill Formation intraclast conglomerates record erosion and reworking of subtidal, subfairweather wave base environments by exceptionally intense and presumably rare storm flows. The intraclast horizons represent a substantial loss in stratigraphic resolution due to widespread erosion of the ramp.