The problem,significance and implications for metamorphism of 60 million years of multiple phases of staurolite growth

Microstructural measurements of FIAs in staurolite reveal at least 3 periods of growth in the Proterozoic Colorado Front Range and 5 in the Paleozoic Western Maine. Dated monazite inclusions in staurolite have an absolute age of 1760±12 Ma (FIA 1), 1720±7 Ma (FIA 2), 1682±18 Ma (FIA 3) in Colorado, and 408±10 Ma (FIA 2), 388±8 Ma (FIA 3), 372±6 Ma (FIA 4), 352±4 Ma (FIA 5) in Maine, supporting the multiple periods of deformation and metamorphism indicated by the FIA succession in each region. Multiple phases of growth by similar reactions in the same as well as in diverse adjacent rocks in both regions suggest that PT and X are not the only factors controlling the commencement and cessation of metamorphic reactions. The FIAs preserved by the staurolite porphyroblasts indicate that the local partitioning of deformation at the scale of a porphyroblast was the eventual controlling factor on whether or not the staurolite forming reactions took place.     

Incipient eclogite facies metamorphism in the Moldanubian granulites revealed by mineral inclusions in garnet

We investigated several mineral phases and their replacement products which occur as inclusions in garnets from felsic and mafic granulites of the Gföhl Unit in the Moldanubian Zone. The most important mineral inclusions, Ti-rich muscovite and omphacite, were used for the reconstruction of the metamorphic history of granulites. Some inclusions were transformed during high-temperature granulite facies metamorphism, partial melting and decompression to other phases, and so the original mineral can only be deduced from the inclusion morphology and reaction products. These inclusions have columnar shapes and consist of K-feldspar + kaolinite, albite + Fe-oxide, plagioclase + Fe-oxide, or albite + K-feldspar, respectively. The pseudomorphs with albite/plagioclase occur in a Ca-rich garnet that shows prograde zoning. Pressure–temperature (PT) evolution, derived from mineral assemblages in granulite and based on the inclusions, suggests a prograde metamorphism from amphibolite through eclogite to granulite facies conditions with subsequent amphibolite facies overprint during exhumation. The estimated PT trajectory for the studied granulites, which also host lenses or boudins of eclogites and garnet peridotites, allows reconstruction of the complete clockwise metamorphic path that is consistent with subduction geotherm prior to the tectonic amalgamation within the continental collisional root.     

Lead isotope signatures of Pb-Zn sulfide mineralization in the Reshian-Lamnian area of Azad Jammu and Kashmir,Pakistan

The Reshian-Lamnian area within the Hazara-Kashmir syntaxis in Pakistan is composed mainly of the rocks of the Salkhala, Panjal and Murree formations. Base metal sulfide mineralization in the form of sphalerite and galena with lesser amounts of chalcopyrite and pyrite is present within the Salkhala Formation of the study area. Chemically all these ore phases are homogeneous in composition. The Pb isotopic composition of galena from the area suggests that there is very little or negligible variation in the ratios of ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb. Modal ages ranging from 509 to 562 Ma and the μ values of 10.71 to 10.93 have been calculated for the studied Pb-Zn mineralization. On the basis of field features, mineralogy and Pb-isotope signatures, it is concluded that the Pb-Zn sulfide mineralization in the Reshian-Lamnia area is pre-Himalayan in age and can be correlated with the Cambro-Ordovician (Pan-African) orogenic event.     

Hydrological processes of adsorption,sedimentation, and infiltration into the lake bed during the 2004 urban flood in Dhaka city,Bangladesh

The urban flood of Dhaka city in September 2004 is a result of heavy rainfall (341 mm a day or more than 600 mm in 5 days). In addition to the local rainfall, elevated water levels in the surrounding rivers may have affected the flood duration by bank filtration. Two lakes, Banani and Gulshan, in the mid of the city are the part of general storm water retention system in Dhaka. Flood water runs through the lakes acting as channels to the pumping station downstream. A tank model is used in this study to describe the total drainage process with the hydraulic geometry and resistance laws to derive cross-sections and friction factors of the quasi-uniform flows. Assuming the dissolved matters of the flood water was of similar composition as in the lake sediments, the process was a combination of adsorption and sedimentation. Lake sediment samples collected in March 2004 show an anomaly of chromium which may reflect the previous 1998 flood, and there may be a diffusive leakage from the source area to the adjacent zones. Further evidence of infiltration process is seen in records of diurnal thermal stratification of Lake Banani. It responds to only heavy rainfalls over 100 mm/day, and the fact means that infiltration to the groundwater is rather intermittent.     

Kinetics of the Reactions of IO with HO2 and O(3P)

A discharge-flow tube coupled with resonance fluorescence and chemiluminescence detection has been used to investigate the reactions IO + HO₂ products (1) and IO + O(³P) I + O₂(2), at T = 296 ± 1 K and P = 1.7 - 2 Torr. The rate constants k_-1 and k₂ have been found to be (7.1 ± 1.6) × 10^-11 cm³ molecule^-1 s^-1 and (1.35 ± 0.15) × 10^-10 cm³ molecule^-1 s^-1, respectively.     

A multivariate sedimentary environmental analysis of Great South Bay and South Oyster Bay, New York

A multivariate statistical strategy for classifying paleoenvironments is effective for studying modern sedimentary processes in western Great South Bay and South Oyster Bay, New York. The 13 whole phi weight percent variables were tested for redundancy with R-mode cluster analysis. The samples were partitioned statistically into five environmentally significant facies using Q-mode cluster analysis: (A)sandy gravel, (B)sandy silt, (C)silty sand, (D)slightly gravelly sand, and (E)fine sand. An ordination depicted gradational relationships among the samples and the facies. It was used to evaluate the environmental and textural parameter gradients within the sample space. Interpretations obtained in this manner and by examination of the grain-size curves suggest that these sediments were deposited by waves and currents on beaches and in wave zones (facies C and E),shoal areas (facies B),and tidal channels (facies A and D).Tidal currents, wave action, and eelgrass control the distribution of sediments within the two bays.     

Groundwater demand management at local scale in rural areas of India: a strategy to ensure water well sustainability based on aquifer diffusivity and community participation

Watershed development programmes provide an opportunity for sustainable management strategies, although currently, they remain largely supply-side mechanisms of water resources development. Hydrogeological conditions, community participation and status of groundwater usage are important in evolving strategies on demand-side groundwater management.Neemkheda aquifer is a typical low-storage, low-hydraulic conductivity aquifer from a watershed in the dryland regions of Madhya Pradesh State of central India. A shallow unconfined aquifer, it consists of an upper coarse, calcareous sandstone unit underlain by a fine-grained sandstone unit. A well commune of seven wells is poised to test the concept of joint groundwater management, wherein wells are mechanisms of tapping a common water source, the Neemkheda aquifer.The strategy for systematic groundwater management in the Neemkheda well commune is based upon the relationship between Transmissivity (T) and Storage coefficient (S), i.e. aquifer diffusivity, and its variation within the aquifer. Wells within a high diffusivity domain tend to dewater more quickly than wells within a low diffusivity domain. A well-use schedule during the dry season, based upon aquifer diffusivity forms the basis of the groundwater management concept. The distribution of local aquifer diffusivities governs the relationship between local and regional aquifer depletion times and forms the basis of the groundwater management exercise being proposed for the Neemkheda aquifer.

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Resumen Los programas de desarrollo de una cuenca hídrica son una oportunidad para el uso de estrategias de gestión sostenible, aunque hoy en día estas siguen siendo principalmente mecanismos para el desarrollo de recursos hídricos con énfasis en la oferta. Las condiciones hidrogeológicas, la participación comunitaria y la condición de utilización del agua subterránea, son importantes en el desarrollo de estrategias para la gestión del agua subterránea, desde el punto de vista de la demanda.El acuífero de Neemkheda es un acuífero típico de almacenamiento bajo y conductividad hidráulica baja, perteneciente a una cuenca hídrica ubicada en las regiones secas del Estado de Madhya Pradesh, en la parte central de India. Un acuífero de tipo libre, somero, formado por una unidad superior de arenisca calcárea de grano grueso, subyacida por una unidad de arenisca de grano fino.Un campo de pozos comunitario compuesto por siete pozos, pone a prueba el concepto de gestión conjunta del agua subterránea, dentro del cual los pozos son mecanismos para usar una fuente de agua común: El acuífero de Neemkheda.La estrategia usada para la gestión sistemática del agua subterránea, en el campo de pozos comunitario de Neemkheda, se basa en la relación existente entre Transmisividad (T) y Coeficiente de Almacenamiento (S), es decir en la Difusividad del Acuífero y en su variación observada dentro del mismo acuífero. Los pozos cuya difusividad esta dentro de un rango alto, tienden a experimentar un descenso en su nivel mas rápidamente que aquellos pozos con una difusividad baja. El concepto de gestión de agua subterránea se basa en un programa especial de operación para cada pozo durante la estación seca, el cual a su vez se basa en la difusividad del acuífero. La distribución de difusividades locales del acuífero rige las relaciones entre las épocas de descensos de nivel en el acuífero a escala regional y local, y además constituyen la base del ejercicio de la gestión del agua subterránea que se esta proponiendo para el acuífero de Neemkheda.

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Résumé Les programmes de développement des bassins versants offrent une occasion de développer des stratégies pour une gestion durable, bien qu à présent elles restent en grande mesure le terme source dans le mécanisme de développement de la ressource en eau. Les conditions hydrogéologiques, la participation de la communauté et lusage des eaux souterraines sont importants pour le terme demande dans les stratégies de gestion des eaux souterraines. Laquifère de Neemkheda presents des caractéristiques typiques pour un bassin versant dans les régions arides de létat Madhya Pradesh de lInde centrale en ce qui concerne les faible valeurs de la conductivité hydraulique et du coéfficient demmagasinement. Il sagit dun aquifère phrèatique dont la partie supérieure est constitué par des grès calcaire qui restent sur des grés plus fins. Afin dessayer le concept de gestion integrée, on a réalisé dans laquifère de Neemkheda un captage ayant sept forages qui forment la ressource en eau communale. La stratégie de la gestion systématique du captage est basée sur la relation entre la transmissivité (T), le coéfficient demmagasinement (S), donc la diffusivité hydraulique ainsi que sa variation spatiale. Les puits forés dans les zones à grande diffusivité tendent à sassècher plus vite que ceux creusés dans des zones à faible diffusivité. Le concept de la gestion des eaux souterraines est donc basé sur la distribution spatiale des diffusivités. À partir de ce concept on a développé un programme dexploitation des forages pendant les saisons sèches. La relation entre les temps d épuissment locaux et régionaux est determiné par la distribution spatiale de la diffusivitée et forme la base de lexercice sur la gestion des eaux proposée pour laquifère de Neemkheda.

     

Wetter or colder during the Last Glacial Maximum? Revisiting the pluvial lake question in southwestern North America

Well-preserved shorelines in Estancia basin and a relatively simple hydrologic setting have prompted several inquiries into the basin's hydrologic balance for the purpose of estimating regional precipitation during the late Pleistocene. Estimates have ranged from 86% to 150% of modern, the disparity largely the result of assumptions about past temperatures. In this study, we use an array of models for surface-water runoff, groundwater flow, and lake energy balance to examine previously proposed scenarios for late Pleistocene climate. Constraints imposed by geologic evidence of past lake levels indicate that precipitation for the Last Glacial Maximum (LGM) may have doubled relative to modern values during brief episodes of colder and wetter climate and that annual runoff was as much as 15% of annual precipitation during these episodes.     

GCP collection for corona satellite photographs: Issues and methodology

Use of high-resolution and historic CORONA satellite photographs for mapping and other purposes requires Ground Control Points (GCPs), as ephemeris data and image parameters are not available. However, the alterations in landscape in last 34 years (i.e., since the acquisition of these photographs) prevent identification and collection of large number of GCPs in the field. This paper presents a methodology for collection of GCPs for CORONA photographs. The advantages and limitations of the methodology are discussed. For a study site, situated in Siwaliks and Lower Himalayas, the GCPs were identified in CORONA photographs and their WGS84 coordinates were estimated through a process of datum transformation and georeferencing. Estimated GCP coordinates from the topo sheets and 2D and 3D views of photographs, helped in identifying the GCP locations in field, which were observed using DGPS. Investigations were carried out to relate Differential Global Positioning System (DGPS) accuracy with base line length and time of observation. Abase line of 350 km and half an hour observation were found appropriate to yield accuracy in GCP collection by DGPS method, which conforms to CORONA resolution of 3 m.