The IUP Journal of Earth Sciences

Dolomitic Limestone in the Kallankurichchi Formation, (Lower Maastrichtian), Ariyalur Group, South India

-- Mu.Ramkumar

Occurence of dolomitic limestones from a restricted and structurally complex region of Kallankurichchi Formation, Ariyalur Group, South India is being documented in this paper. Field, petrographic, mineralogic and geochemical characteristics of the rocks suggest that these dolomites are diagenetic in origin and are developed during the late stage in a partially-closed system under oxygenated and partially-confined meteoric waters. Due to semi-closed system of diagenesis, stabilization of high magnesian calcite into low magnesian calcite concomitant with expulsion of Mg²⁺ to diagenetic waters, source for magnesium is local and available nearby. Poor dolomitic conditions in terms of weak diagenetic fluids, less bulk chemical difference between diagenetic components and susceptibility of micritic mud to alteration have led to the dolomitization of only the matrix portion of limestone.

© 2007 IUP . All Rights Reserved.

Facies Analysis of the Boka Bill Formation as Exposed along the Barogang-Hari River Section, Northeastern Sylhet, Bangladesh

-- Mrinal Kanti Roy, Mst.Shamima Akter, Partha Jit Roy, Sarmin Akther, Md. Nazwanul Haque, Atiqur Rahman Malik and Sultan Mahmud

The Boka Bill Formation of the Surma Group of Barogang-Hari section, NE Sylhet, Bangladesh is constituted by blue to black shale, yellowish gray to light yellow medium to fine sandstone, gray to grayish siltstone, gray to blue as well as dark colored mudstone and brownish gray conglomerate. Twelve distinct lithofacies have been recognized within the Boka Bill Formation. The facies are grouped into three facies associations based on genetic aspects: the Fluvial Facies Association (FFA) composes the Lower Boka Bill member; the Tidal Facies Association (TFA) forms the Middle Boka Bill member; and the Marine Facies Association (MFA) represents the Upper Boka Bill member. The FFA represents incised valley, braided channel and over bank fines; the TFA is formed due to the processes of estuary, tidal creek, and tidal flat; and the MFA is the result of deep marine hemipelagic sedimentation with little progradation of distal turbidite. The unimodal-unidirectional paleocurrent pattern of the FFA indicates mono-directional dispersal path of fluvial environment. The bipolar-bidirectional paleocurrent with some deviations of the TFA strongly shows flow reversal, which is common in tidal environment. The monodirectional-unimodal paleocurrent rose diagram of the MFA indicates unidirectional flow of turbidity current in the deep marine environment.

© 2007 IUP . All Rights Reserved.

Geology of the Gelali Iron Mineralization Related to the South Ghorveh Batholith, Western Iran

-- Hassan Zamanian

The South Ghorveh Batholith (SGB) in Western Iran intruded the volcanosedimentary sequence of Songhor Series (Triassic-Jurassic) during the Oligo-Miocene orogenic phase. The granitoids can be generally characterized as quartz monzonite, varying towards quartz monzodiorite, and diorite. Granitoids, comprising the batholith, are low in free quartz, and possess characteristics of the `magnetite series' of I-type, metaluminous and calc-alkaline type. Adjacent to the SGB, the magnetite skarn deposit is located at Gelali. The estimated ore reserve at the Gelali deposit is 61mt with 63% Fe. In the light of petrography, geochemistry, mineralogy and field investigations, it could be classified as Fe-skarn, and mainly bears the characteristics of mixed calcic and magnesian skarn deposits. Mixed nature of the Gelali deposit and presence of a cluster of calcic skarn deposits like Baba Ali and Chenar in adjacent area characterize an oceanic island arc environment for SGB setting. It is also supported by volcanosedimentary characteristics of the Songhor Series. The low association of sulfide minerals of Cu, Zn, Co, Au and Ni with the Gelali magnetite deposit is an additional supportive characteristic of the island arc environments.

© 2007 IUP . All Rights Reserved.

Groundwater Quality Assessment for Irrigation and Domestic Uses in Raigad District, Maharashtra, India

-- Saumitra Mukherjee and Anup Kumar Das

The chemical characteristics of groundwater in Raigad district of Maharashtra have been studied to evaluate the suitability of water for irrigation and domestic uses. Sixty seven water samples from dug wells, bore wells and observatory bore wells are collected and analyzed for pH, EC, TDS, TH, Na, K, Ca, Mg, CO₃, HCO₃, Cl, F, SO₄ and NO₃. It is observed that the quality of groundwater is suitable for domestic purpose with few exceptions. High SAR, %Na and RSC in most groundwater samples suggest that the waters are not suitable for irrigation. Doneen's permeability index classifies water good for irrigation.

© 2007 IUP . All Rights Reserved.

Quantitative Value Addition Analysis of Multisensor Data Fusion

-- Ch Venkateswara Rao, P Shasidhar Reddy, D S Jain and K M M Rao

Remote sensing satellites are equipped with different sensors that have varied characteristics. Due to certain constraints, the satellite data can have either high spatial resolution, but low spectral accuracy (panchromatic data) or exhibit high spectral fidelity (multispectral), but acquired with low spatial resolution. Fusion of digital image is an important technique to maximize the advantage of the available multisensor, multitemporal, and multispectral data obtained from remote sensing satellites. Fused images improve the quality of information, in addition to providing superior interpretation potential. Although several fusion methods at the pixel level are available, all these approaches do not consider in a similar manner the small structures to be injected from images of the highest resolution into the lowest resolution. A "preservation trade-off" exists between the spatial and spectral quality. The main demand of the user concerns the preservation of quality of the multispectral content while increasing the spatial resolution. This paper aims at the evaluation of spatial quality of fused images using a new approach by which the sharpest points are identified by the Modulus Maxima, and compares with other evaluation parameters. Spectral quality evaluation studies were carried out on fused images using image comparison, correlation, entropies, image noise index, and mutual information, which provide a concise framework for both. These evaluation measures are presented with reference to the IRS data sets. This forms a useful tool in identifying the appropriate technique for an intended application. The paper describes the original methodologies for acquiring unbiased measurements to assess the performance of fused images.

© 2007 IUP . All Rights Reserved.