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1

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Stable isotopes and heavy metal distribution in Dreissena polymorpha (Zebra Mussels) from western basin of Lake Erie, Canada (1998)

Al-Aasm, I. S. ; Clarke, J. D. ; Fryer, B. J.

Springer

Environmental geology 33 (1998), S. 122-129

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ISSN: 1432-0495

Keywords: Key words Stable isotopes ; Heavy metals ; Zebra mussels ; Lake Erie

Source: Springer Online Journal Archives 1860-2000

Topics: Geosciences

Notes: Abstract Dreissena polymorpha is an exotic freshwater bivalve species which was introduced into the Great Lakes system in the fall of 1985 through the release of ballast water from European freighters. Utilizing individual growth rings of the shells, the stable isotope distribution (δ18O and δ13C) was determined for the life history of selected samples which were collected from the western basin of Lake Erie. These bivalves deposit their shell in near equilibrium with the ambient water and thus reflect any annual variation of the system in the isotopic records held within their shells. Observed values for δ18O range from -6.64 to –9.46‰ with an average value of –7.69‰ PDB, while carbon values ranged from –0.80 to –4.67‰ with an average value of –1.76‰ PDB. Dreissena polymorpha shells incorporate metals into their shells during growth. Individual shell growth increments were analyzed for Pb, Fe, Mg, Mn, Cd, Cu, and V concentrations. The shells show increased uptake of certain metals during periods of isotopic enrichment which correspond with warmer water temperatures. Since metals are incorporated into the shells, the organism may be useful as a biomonitor of metal pollution within aquatic environments.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s002540050232

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Sequence stratigraphic distribution of diagenetic alterations in coal-bearing, paralic sandstones: evidence from the Rio Bonito Formation (early Permian), southern Brazil (2003)

Ketzer, J. Marcelo ; Holz, Michael ; Morad, S. ; [et al.]

Oxford, UK : Blackwell Science Ltd

Sedimentology 50 (2003), S. 0

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ISSN: 1365-3091

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Geosciences

Notes: Abstract Linking siliciclastic diagenesis to sequence stratigraphy allows a better understanding of the parameters controlling the spatial and temporal distribution of diagenetic alterations, and hence of reservoir quality. A study of the coal-bearing, alluvial, deltaic, estuarine and shallow-marine sandstones of the Rio Bonito Formation, early Permian, Paraná Basin (southern Brazil), reveals that the distribution of diagenetic alterations and of related reservoir quality evolution can be constrained within a sequence stratigraphic framework. Calcite, dolomite, siderite, kaolinite and pyrite cementation is consistently linked to sequence and parasequence boundaries, transgressive and maximum flooding surfaces and is systematically distributed within lowstand, transgressive and highstand systems tracts. Diagenesis of coal layers at parasequence boundaries has promoted the formation of stratabound calcite (detectable in resistivity wire line logs), concretionary pyrite and kaolinite and of silicate grain dissolution in sandstones located above and below these boundaries, particularly in the transgressive systems tract. Meteoric water diagenesis caused grain dissolution and the formation of kaolinite in sandstones below sequence boundaries and in lowstand systems tract sandstones. Carbonate bioclasts and low sedimentation rates in lag deposits at parasequence boundaries, transgressive and maximum flooding surfaces favoured the formation of grain-rimming siderite. The results of this study are relevant to the exploration of coal-bed methane and other coal-bearing reservoirs, where it is crucial to unravel and predict the distribution and quality of reservoirs and compartments.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-3091.2003.00586.x

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Diagenesis of a mixed siliciclastic/evaporitic sequence of the Middle Muschelkalk (Middle Triassic), the Catalan Coastal Range, NE Spain (1995)

MORAD, S. ; AL-AASM, I. S. ; LONGSTAFFE, F. J. ; [et al.]

Oxford, UK : Blackwell Publishing Ltd

Sedimentology 42 (1995), S. 0

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ISSN: 1365-3091

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Geosciences

Notes: The Middle Muschelkalk (Middle Triassic) of the Catalan Coastal Range (north-east Spain) comprises sandstone, mudstone, anhydrite and minor carbonate layers. Interbedded sandstones and mudstones which are dominant in the north-eastern parts of the basin are terminal alluvial fan deposits. South-westward in the basin, the rocks become dominated by interbedded evaporites and mudstones deposited in sabkha/mudflat environments. The diagenetic and pore water evolution patterns of the Middle Muschelkalk suggest a strong facies control. During eodiagenesis, formation of microdolomite, anhydrite, baryte, magnesite, K-feldspar and mixed-layer chlorite/smectite was favoured within and adjacent to the sabkha/mudflat facies, whereas calcite, haematite, mixed-layer illite/smectite and quartz formed mainly in the alluvial facies. Low δ18OSMOW values for microdolomite (+23.7 to +28.4%) and K-feldspar overgrowths (+17.3 to +17.7%) suggest either low-temperature, isotopic disequilibrium or precipitation from low-18O porewaters. Low-18O waters might have developed, at least in part, during low-temperature alteration of volcanic rock fragments. During mesodiagenesis, precipitation of quartz overgrowths and coarse dolomite occurred in the alluvial sandstones, whereas recrystallization of microdolomite was dominant in the sabkha/mudflat facies. The isotopic compositions of these mesogenetic phases reflect increasing temperature during burial. Upon uplift and erosion, telogenetic calcite and trace haematite precipitated in fractures and replaced dolomite. The isotopic composition of the calcite (δ18OSMOW=+21.5 to +25.6%o; δ13C= 7.7 to - 5.6%o) and presence of haematite indicate infiltration of meteoric waters.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1365-3091.1995.tb00407.x

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Diagenesis and formation water chemistry of Triassic reservoir sandstones from southern Tunisia (1994)

MORAD, S. ; ISMAIL, H. N. BEN ; ROS, L. F. ; [et al.]

Oxford, UK : Blackwell Publishing Ltd

Sedimentology 41 (1994), S. 0

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ISSN: 1365-3091

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Geosciences

Notes: The fluvial Triassic reservoir subarkoses and arkoses (2409·5–2519·45 m) of the El Borma oilfield, southern Tunisia, were subjected to cementation by haematite, anatase, infiltrated clays, kaolinite and K-feldspar at shallow burial depths from meteoric waters. Subsequently, basinal brines controlled the diagenetic evolution of the sandstones and resulted initially in the precipitation of quartz overgrowths, magnesian siderite, minor ferroan magnesite and anhydrite. The enrichment of siderite in 12C isotope (δ13CPDB= - 14·5 to - 9‰) results from derivation of carbon from the thermal decarboxylation of organic matter. During further burial, the precipitation of dickite and pervasive transformation of kaolinite into dickite occurred, followed by the formation of microcrystalline K-feldspar and quartz, chlorite and illite, prior to the emplacement of oil. Present day formation waters are Na-Ca-Cl brines evolved by the evaporation of seawater and water/mineral interaction and are in equilibrium with the deep burial (≤ 3·1 km) minerals. These waters are suggested to be derived from the underlying Silurian and Devonian dolomitic mudstones.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1365-3091.1994.tb01452.x

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Subaerial exposure and meteoric diagenesis of the Cenomanian-Turonian Upper Sarvak Formation, southwestern Iran (2010)

Hajikazemi, E. ; Al-Aasm, I. S. ; Coniglio, M.

In: Geological Society Special Publication 330: 253-272.

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Publication Date: 2010-06-03

Description: The Sarvak Formation (Cenomanian-Turonian) forms one of the main reservoir rocks in many oilfields in southern Iran. Extensive lateral and vertical facies variations as well as effects caused mainly by the subaerial exposure associated with the regional Turonian unconformity have resulted in variable porosity and permeability. Dissolution affected the entire upper part of the Sarvak Formation and is the most important process related to subaerial exposure. Brecciation, development of palaeosol and formation of bauxite deposits are also limited to the upper few metres of the top of the Sarvak Formation and indicate warm and humid climatic conditions. Subaerial exposure had varying effects on the diagenesis depending on its duration, palaeotopography and the availability of meteoric water. The {delta}18O and {delta}13C values obtained from calcitic matrix, various generations of calcite cements and calcitic rudist shells in the Upper Sarvak overlap to a large extent, indicating their equilibration with fluids of similar isotopic composition. Negative {delta}18O values (i.e. -6.6{per thousand} to -1.7{per thousand}) suggest a significant meteoric component. More 18O-depleted values (e.g. -12.3{per thousand}) obtained from late calcite cements indicate their precipitatation from warm fluids. Positive {delta}13C values (i.e. 0.00{per thousand} to 3.4{per thousand}) in the various carbonate phases reflect values of seawater coeval with an Oceanic Anoxic Event and later modified by meteoric waters.

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Origin and evolution of microporosity in packstones and grainstones in a Lower Cretaceous carbonate reservoir, United Arab Emirates (2016)

Morad, D., Paganoni, M., Al Harthi, A., Morad, S., Ceriani, A., Mansurbeg, H., Al Suwaidi, A., Al-Aasm, I. S., Ehrenberg, S. N.

Geological Society (of London)

In: Special Publications / Geological Society London

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Publication Date: 2016-12-23

Description: Microporosity in carbonate reservoirs is generated by the complex interplay between depositional and diagenetic processes. This petrographical, SEM, fluid-inclusion and isotopic study of a Lower Cretaceous carbonate reservoir, Abu Dhabi, UAE, revealed that: (1) micritization of ooids and skeletal fragments, which resulted in spheroidal (rounded) micrite, accounts for most microporosity in peloidal packstones and grainstones; and (2) transformation of spheroidal micrite into subhedral/euhedral micrite and microspar, known as aggrading neomorphism, could happen via precipitation of syntaxial calcite overgrowths around micrite (micro-overgrowths) and not only, as suggested previously in the literature, by recrystallization involving the dissolution (of micrite) and reprecipitation (of microspar). Precipitation of calcite cement around micrite (i.e. destruction of microporosity) is more extensive in the water zone than in the oil zone, which is possibly contributing to the lower porosity and permeability of the carbonate reservoir in the water zone. Similarity in bulk oxygen isotopic values of micritized packstones and grainstones in the water and oil zones (average 18 O V-PDB =–7.2 and –7.8, respectively) is attributed to: (1) a small difference in temperatures between the crest (oil zone) and the flanks (water zone); and (2) calcite precipitation around micrite occurred prior and subsequent to oil emplacement. Bulk carbon and strontium isotopic compositions of micritized packstones and grainstones in the water and oil zones (average 13 C V-PDB =+3.7 and average 87 Sr/ 86 Sr ratios=0.707469) indicate that calcite cement was derived from marine porewaters and/or dissolution of the host limestones. The minimum formation temperatures of bulk micrite/microspar, which are inferred based on paragenetic relationships, fluid-inclusion microthermometry and oxygen isotope data, are around 58–78°C.

Print ISSN: 0305-8719

Electronic ISSN: 2041-4927

Topics: Geosciences

Published by Geological Society (of London)

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Petrologic and geochemical attributes of calcite cementation, dolomitization and dolomite recrystallization: an example from the Mississippian Pekisko Formation, west-central Alberta (2017)

Adam, J., Al-Aasm, I. S.

Canadian Society of Petroleum Geologists (CSPG)

In: Bulletin of Canadian Petroleum Geology

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Publication Date: 2017-07-07

Description: Carbonate rocks of the Pekisko Formation make up an important reservoir in west-central Alberta, especially in fields along the Pekisko subcrop edge. They represent a transgressive-regressive carbonate platform sequence comprised of upward shallowing facies, which subsequently underwent extreme erosion leading to the development of karst topography. As a result, diagenetic alteration, mainly through dolomitization and karstification, has affected reservoir characterization for most of the carbonate facies. Several generations of calcite cementation and dolomite are the result of complex diagenetic changes. Calcite cements include isopachous fibrous, equant drusy mosaic, pendant/meniscus, blocky spar, syntaxial, fibrous, and bladed. These cements formed during early and late diagenetic events; pre-syn- and post exposure in shallow and deeper burial realms. There are five types of dolomite identified in the Pekisko Formation, based on petrographic and geochemical analyses: 1) pervasive, fine to coarse crystalline, subhedral to anhedral replacive dolomite; 2) void-filling, coarse crystalline, euhedral dolomite cement; 3) selective, fine to coarse crystalline, euhedral to anhedral dolomite; 4) dissolution seam-associated, fine crystalline, euhedral dolomite; and 5) saddle dolomite. Dolomite types 1), 3) and 4) are interpreted to have formed early in the diagenetic history and subsequently recrystallized, whereas void-filling, coarse crystalline, euhedral dolomite and saddle dolomite formed later in deeper burial setting. Petrographic evidence for recrystallization of dolomite types, excluding void-filling and saddle dolomite, includes: etching, displayed mainly on euhedral crystals; dissolved cores on many crystals of varying shapes; non-planar crystal boundaries, exclusively in pervasive dolomites; and coarsening crystal size, evident in both pervasive and selective dolomite types. Geochemical evidence, such as pronounced negative shift in oxygen isotopes (by up to 8 VPDB) and enrichment of radiogenic Sr isotopes further support this interpretation. There is a definite negative trend whereby wells closest to the subcrop edge have the most negative isotopic values and those farthest away show the least depletion. This trend in 18 O isotope values points to recrystallization of the earlier formed dolomites.

Print ISSN: 0007-4802

Electronic ISSN: 0007-4802

Topics: Geosciences