A storm and tidally-influenced prograding shoreline—Upper Cretaceous Milk River Formation of Southern Alberta, Canada

The Santonian-Campanian Milk River Formation of Southern Alberta represents the transition from an open shelf, through a storm-dominated shoreface into a non-marine sequence of shales and sandstones, with coal. The open shelf deposits consist of interbedded bioturbated mudstones with sharp-based hummocky cross-stratified sandstones. There are no indications of fairweather reworking of the sandstones, which are therefore interpreted as having been deposited below fairweather wavebase. The shoreface sequence consists of a 28 m thick sandstone. It has a very sharp, loaded base, and is dominated by swaley cross-stratification, a close relative of hummocky cross-stratification. Angle of repose cross-bedding is preserved in scattered patches only in the top 5 m of the sand body. Channels up to 180 m wide and 7 m deep are cut into this sand body, with channel margins characterized by lateral accretion surfaces. Regional dispersal trends, as well as local palaeocurrent readings suggest flow toward the NW. Within the channels there is some herringbone cross-bedding and at least two examples of neap-spring bundle cycles, suggesting that the channels are tidally-influenced. Above the channels there is a sequence of carbonaceous shales with in situ root casts and lignitic coal seams. No marine, brackish or lagoonal fauna was identified, and the sequence appears to represent a distal floodplain. The sequence from interbedded hummocky cross-stratified sandstones and bioturbated mudstones into a 10–20 m thick, sharp-based shoreface sandstone characterized by swaley cross-stratification is uncommon. The scarcity or absence of angle of repose cross-bedding in the shoreface, and the dominance of swaley cross-stratification suggests that the shoreface was so storm-dominated that almost no fairweather record was preserved. Other examples of swaley cross-stratified shorefaces are reviewed in the paper.     

A decision support system-based procedure for evaluation and monitoring of protected areas sustainability for the Mediterranean region

Despite common acknowledgement of the value of protected areas as instruments in ensuring sustainability, and their promotion for the achievement of policies on halting the loss of biodiversity, there is no common approach today for monitoring and evaluating them. This paper presents a novel integrated nature conservation management procedure developed to monitor and evaluate the sustainability of Mediterranean protected areas. This procedure was successfully implemented and formally evaluated by protected area managers in six Mediterranean countries, results of which are presented here together with an overview of the web-based Decision Support System (DSS) developed to facilitate its wide adoption. The DSS and procedure has been designed and evaluated by managers as a useful tool, which facilitates and provides needed procedural guidance for protected area monitoring whilst minimizing input requirements to do so. The procedure and DSS were developed following a review of existing protected area assessment tools and a detailed primary investigation of the needs and capacity of its intended users. Essentially, the procedure and DSS guides provide the facilities for protected area managers, in following a participatory approach to develop a context-specific sustainability monitoring strategy, for their protected area. Consequently, the procedure is, by design, participatory, context specific, holistic and relevant to protected area management and institutional procedures. The procedure was piloted and formally evaluated in Greece, Italy, Turkey, Egypt, Malta and Cyprus. Feedback collected from the pilot evaluations is also summarised herein.     

Low-grade metamorphic rocks from the Pulur complex,NE Turkey: implications for the pre-Liassic evolution of the Eastern Pontides

In the Pulur complex (Sakarya Zone, Eastern Pontides, Turkey) a low-grade tectonometamorphic unit (Doankavak) is exposed in three tectonic windows beneath a complex medium-pressure high-temperature metamorphic unit of late Carboniferous age. The thrust plane between both units is transgressively covered by Liassic conglomerates. The Doankavak unit comprises a sequence of metabasites with MORB-type chemical compositions and phyllites, with subordinate calcareous phyllites, marbles, quarzofeldspathic schists and metacherts. This sequence is interpreted as a former accretionary complex related to the consumption of the Palaeotethys. Mineral parageneses in the metabasites allow for the distinction of two domains with slightly different peak metamorphic conditions, i.e. 375–425 °C/0.5–0.8 GPa (greenschist facies) and 400–470 °C/0.6–1.1 GPa (albite-epidote amphibolite facies). The age of metamorphism is constrained at ~ 260 Ma (early Late Permian) by two Rb-Sr mineral-whole rock ages (hornblende, phengite) and one ⁴⁰Ar/³⁹Ar single step total fusion age (phengite). In conjunction with previous data on other accretionary complexes in the Sakarya zone in Northern Turkey, the data presented in this study suggest a continuous subduction of the Palaeotethys at least from Early/Late Permian to Late Triassic and a discontinuous preservation of accretion complexes in both space and time.     

A combined hydrologic and hydraulic modeling approach for testing efficiency of structural flood control measures

The necessity of estimating the degree and spatial extent of positive impacts with regard to protecting communities and properties through potential flood control projects can be considered one of the main reasons for performing flood modeling. This paper presents an overall systematic approach based on the simulation of some extreme event conditions, using a hydrological model to generate the resulting river flows and then using a hydraulic modeling exercise to decide upon floodplain evolution in the case-study area, Bostanli river basin, which has been under the threat of flooding for many years. The potential serviceability of the planned Bostanli Dam in the study area was examined by using the HEC-HMS and HEC-RAS modeling tools, both integrated with GIS functions for spatial operations. The results indicate that the dam construction as planned would have a somewhat positive impact as a potential flood control measure, since it seems to decrease the flood peaks of 68.9 and 158.7 m³/s (that would potentially be generated by 100- and 500-year storm events under current conditions) to 65.5 and 150.7 m³/s (when the dam is in operation), respectively. However, this seems to contribute little to the overall flood mitigation performance in the basin.     

Petrology of the tin-bearing granite-leucogranites of the Piaoak Massif, Northern Vietnam

The Piaoak tin-bearing granite-leucogranites located in the Caobang Province of Northern Vietnam compose a stock-like hypabyssal body. Host rocks are represented by Early Devonian carbonate sequences and Early Triassic ??black?? shales. The geochronological age of the Piaoak granite-leucogranites corresponds to the Late Cretaceous: T = 83.5 ± 6.2 Ma, ⁸⁷Rb/⁸⁶Sr method; T = 89.7 ± 1.0 Ma, ³⁹Ar/⁴⁰Ar method. The massif has a simple basic to acid order: two-mica and muscovite granite-leucogranite ?? raremetal aplites, pegmatites ?? tin-bearing greisens and hydrothermal veins. The petrographic and microstructural studies revealed a sharp change in crystallization conditions of the granite-leucogranite magma at the late magmatic stage and formation of muscovite via incongruent melting of protolithionite. The study of melt and coexisting fluid inclusions showed that solidus crystallization occurred under fluid-saturated conditions at 635?C600°C. In composition, the granite-leucogranites of the Piaoak Massif correspond to the raremetal-plumasite geochemical type (according to L.V. Tauson), and reach Li-F facies in terms of their rare-element composition. The composition of aplites and pegmatites demonstrates that granite-leucogranite magma did not accumulate lithophile and volatile components in the residual melt during differentiation, but was initially enriched in rare-metals. It is most probable that the melt was generated from Proterozoic lithotectonic complexes and overlaying Lower Triassic ??black?? shales.     

National flood discharge mapping in Austria

This article presents the approach and the results of a study in which 30, 100 and 200 year return period flood discharges were estimated for 26,000 km of Austrian streams. Three guiding principles were adopted: combination of automatic methods and manual assessments by hydrologists to allow speedy processing and account for the local hydrological situation; combination of various sources of information including flood peak samples, rainfall data, runoff coefficients and historical flood data; and involvement of the Hydrographic Services to increase the accuracy and enhance the acceptance of results. The flood discharges for ungauged catchments were estimated by the Top-kriging approach with manual adjustment to the local flood characteristics. The adopted combination approach proved to be very efficient both in terms of the project time required and in terms of the accuracy and acceptability of the estimated flood discharges of given return periods.     

Experimental study of partitioning of tantalum,niobium, manganese,and fluorine between aqueous fluoride fluid and granitic and alkaline melts

This study presents a new set of quantitative experimental data on the partitioning of Ta, Nb, Mn, and F between aqueous F-bearing fluid and water-saturated, Li- and F-rich haplogranite melts with varying alumina/alkali content at T = 650–850 °C and P = 100 MPa. The starting homogeneous glasses were preliminary obtained by melting of three gel mixtures of K₂O-Na₂O-Al₂O₃-SiO₂ composition with a variable Al₂O₃/(Na₂O+K₂O) ratio, ranging from 0.64 (alkaline) and 1.1 (near-normal) to 1.7 (alumina-rich). Ta, Nb, and Mn were originally present in glass only, whereas F was load in both the glass and the solution. The solutionto-glass weight ratio was 1.5–3.0. The compositions of quenched glass were measured by an electronic microprobe, and those of the aqueous solution, with the ICP-MS and ICP-AES methods. The F concentration in the quenched solution was calculated from the mass balance. Under experimental conditions the partition coefficients of Ta, Nb, and Mn between the fluid and the granitic melt (weight ratio ^fluid C _Ta/^melt C _Ta = ^fluid/melt D _Ta) are shown to be extremely low (0.001–0.008 for Ta, 0.001–0.022 for Nb, and 0.002–0.010 for Mn); thus, these metals partition preferentially into the melt. The coefficients ^fluid/melt D _Ta and ^fluid/melt D _Nb generally increase either with increasing alumina ratio A/NKM in the glass composition, or with rising temperature. The experiments also demonstrated that F preferentially concentrates in the melt; and the partition coefficients of F are below 1, being within the range of 0.1–0.7.

     

The Spačice eclogite: constraints on the P–T–t history of the Gföhl granulite terrane, Moldanubian Zone, Bohemian Massif

Summary In the Kutná Hora Complex, the Běstvina Formation, which is similar to Gf?hl granulite, contains eclogite that has escaped widespread retrograde recrystallization. The eclogite assemblage, garnet + omphacite + quartz + rutile ± plagioclase, yields an estimate for peak metamorphic conditions of 18–20 kbar and 835–935 °C, which is comparable to that determined from felsic granulite, 14–20 kbar and 900–1000 °C. Garnet in eclogite exhibits both prograde and retrograde compositional zoning, from which constraints on thermal history of the Gf?hl terrane can be derived by diffusion modelling. At 900 °C, a garnet grain of 800–1000 μm radius would homogenize in 7.5–11.7 million years, but the existence of compositional gradients on a length scale of 100–200 μm suggests that the duration of peak metamorphism may have been limited to ∼500,000 years. Diffusion modelling of retrograde zoning in garnet yields a cooling rate of 150–100 °C/m.y. for a radius of 800–1000 μm and initial temperature of 900 °C. The relatively brief duration of high-pressure/high-temperature metamorphism and rapid cooling and exhumation of the Gf?hl terrane may be a consequence of lithospheric delamination during Early Carboniferous collision of Bohemia (Teplá-Barrandia) and Moldanubia (Franke, 2000).     

Emerald mineralisation in Colombia: fluid chemistry and the role of brine mixing

Emerald mineralisation in Colombia is located in two distinct zones along the borders of the Eastern Cordillera, some 80 km apart. Mineralisation in the western zone has been dated at ca. 35 Ma whereas in the eastern zone it is 30 Ma older. Crush leach analysis of the electrolyte chemistry of fluid inclusions contained in emerald, quartz, calcite, dolomite and fluorite from both zones, demonstrates that in each region brines associated with emerald mineralisation range between two extremes with many samples yielding intermediate compositions. Fluid 1, found mainly in emerald-hosted fluid inclusions, is dominated by NaCl with high Cl:Br ratios indicating that the salinity was derived by dissolution of halite, most probably from the local salt beds. Fluid 2, found notably in quartz hosted-fluid inclusions, is of similar salinity but contains less Na and significant concentrations of Ca–K–Fe–Cl and other cations. It has lower Cl:Br ratios, more comparable with formation waters, but is inferred to have obtained part of its salinity by halite dissolution. Bivariate plots of almost all cations have linear or sublinear trends regardless of the mineral hosting the inclusions or the locality from which the samples originated, demonstrating that mixing of the two saline fluids has occurred. Because the same two fluids occur in both eastern and western zones, despite the difference in space and time, it is inferred that fluid compositions were rock controlled by similar interactions with evaporites and black shales in both instances. It is proposed that beryllium was transported as Be–F complexes in the NaCl-fluid, and was precipitated as emerald after mixing with the calcic brine caused precipitation of fluorite and parisite. Received: 9 April 1999 / Accepted: 14 March 2000     

A lithofacies model of upper jurassic productive deposits in the eastern part of the Shirotnoye Priobie region (Western Siberia)

On the basis of an integrated interpretation of well data, core analysis, geophysical well logging, and seismic data a new geological model of the JV₁¹⁻² stratum is suggested for one of the Shirotnoye Priobie areas in Western Siberia. The results of acoustic inverse and the rock elastic property research were used for the validation of lithofacies zonation. Supplementary exploration of the area and production drilling are recommended.