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Donna Kirkwood - One of the best experts on this subject based on the ideXlab platform.
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A structural study of western Anticosti Island, St. Lawrence platform, Quebec: a fracture analysis that integrates surface and subsurface structural data
Bulletin of Canadian Petroleum Geology, 2010Co-Authors: Esther Bordet, Michel Malo, Donna KirkwoodAbstract:Abstract Field data from fracture sets, folds and faults affecting generally flat lying Lower Ordovician to Lower Silurian strata on western Anticosti Island, Quebec, are integrated with remote sensing and seismic reflection data. Spatial and temporal relationships among different structural features observed on the Island and in the Gulf of St. Lawrence are assessed with the aim of understanding the role of these structural features for petroleum migration through the Anticosti Platform. The tectonic impact of Appalachian orogenic events on Anticosti Platform is considered, together with Jurassic and Quaternary tectonics. Four fracture sets are identified in Lower Silurian rocks: 1) a NS-EW orthogonal fracture system (Sets I and II); 2) a N40–70 set (Set III); 3) and a N135–165 set (Set IV). Some irregular, randomly oriented fractures are also observed. The orthogonal system may be related to Early Acadian events, which may have induced extensional stresses within the Platform during Late Silurian-Early Devonian time. Normal faults observed in the Lower Silurian succession may be related to this extensional event. The N135–165 and N40–70 sets may have developed either during the Middle Devonian Acadian Orogeny or later in the Jurassic. The irregular fractures could have formed during the final stages of fracture development in response to erosion of the Lower Silurian and younger succession, or in response to isostatic rebound following glaciation. Shuttle Radar Digital Elevation Model lineaments are consistent either with observed fracture set orientations, or subsurface Taconian fault orientations. We infer some Taconian faults and Silurian fracture zones were reactivated, probably during the opening of the Atlantic Ocean, as indicated by the intrusion of two Jurassic dikes. In the subsurface of the Island, major SW-dipping normal faults and extensional fractures affect the Lower to Upper Ordovician succession most. These probably formed in response to an extensional stress field in front of the Taconian deformation front during Late Ordovician time. WSW-trending typically open folds occur on southern Anticosti Island in Chicotte Formation and in the Gulf of St. Lawrence. They involve Lower Silurian to Devonian rocks, and may have formed in a compressive regional setting during the Middle Devonian Acadian Orogeny. Thermal maturation and petroleum generation on Anticosti Platform are controlled mainly by the burial history. However, the structures described in this study, in particular Taconian and Early Acadian fractures and faults systems, may have played an important role in petroleum migration and in potential reservoir development.
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microstructural analysis and geochemical vein characterization of the salinic event and Acadian Orogeny evaluation of the hydrocarbon reservoir potential in eastern gaspe
Bulletin of Canadian Petroleum Geology, 2001Co-Authors: Donna Kirkwood, Martine M SavardAbstract:ABSTRACT For the past century, eastern Gaspe Peninsula has generated an interest in oil and gas exploration. This paper examines the fractured reservoir play in the Upper Ordovician to Lower Silurian limestones of the White Head Formation. The White Head Formation is strategically important for play concepts in eastern Gaspe because of its stratigraphic position, overlying potential source rocks of Cambrian and Ordovician age, and underlying Silurian and Devonian rocks that host oil seeps. Combined microstructural and petrographic evidence, as well as isotope geochemistry, helped in proposing a genetic link between fracture sets and the Salinic event and Acadian Orogeny. The proposed tectonic model involves three distinct events beginning with shallow to moderate burial, followed by fracturing and uplift as a result of normal faulting during the Salinic disturbance, and deeper burial, fracturing, folding and strike-slip faulting during the Acadian Orogeny. Fractures that developed within the White Head limestones during the Salinic event and the Acadian Orogeny contributed to enhance porosity and permeability to some extent at different stages during the entire tectonic history of the rocks. The presence of liquid hydrocarbon inclusions in Salinic veins and methane inclusions in the Acadian veins indicates that hydrocarbon-rich fluids migrated through the fracture network. The Salinic fracture network could therefore have provided a pathway for expulsion of liquid hydrocarbons from source rocks before they became overmature. RESUME Au cours du dernier siecle, l'Est de la Gaspesie a suscite l'interet pour l'exploration de l'huile et du gaz. Cet article evalue le potentiel en reservoirs fractures dans les calcaires ordoviciens superieurs a siluriens inferieurs de la Formation de White Head. Cette derniere est strategiquement importante pour cette demarche d'evaluation a cause de sa position stratigraphique au-dessus de roches cambriennes et ordoviciennes potentiellement roches-meres, et en-dessous de roches siluriennes et devoniennes dans lesquelles on a repertorie des sources d'huile. Une combinaison d'evidences venant de l'analyse microstructurale et petrographique et de la geochimie isotopique conduit a proposer l'existence d'un lien genetique entre des ensembles de fractures, la pulsation salinique et l'orogenie acadienne. Le modele tectonique propose implique trois evenements distincts: d'abord un enfouissement peu profond a intermediaire, suivi par de la fracturation et du soulevement relies a du faillage normal durant la pulsation salinique, puis finalement un enfouissement plus profond, de la fracturation, du plissement et du faillage de decrochement durant l'orogenie acadienne. Des fractures se sont developpees dans les calcaires de White Head pendant l'evenement salinique; l'orogenie acadienne a par la suite contribue a ameliorer dans une certaine mesure la porosite et la permeabilite a differents stades pendant toute l'histoire tectonique de la formation. La presence d'inclusions d'hydrocarbures liquides dans des veines saliniques et d'inclusions de methane dans des veines acadiennes indique que des fluides riches en hydrocarbures ont migre a travers le reseau de fractures. Le reseau de fractures salinique a pu consequemment presenter une voie d'expulsion des hydrocarbures liquides de la roche-mere, avant qu'ils ne deviennent trop matures. Traduit par les auteurs. End_Page 262------------------------
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paleogeography and tectono sedimentary history at the margin of laurentia during silurian to earliest devonian time the gaspe belt quebec
Geological Society of America Bulletin, 2000Co-Authors: Pierreandre Bourque, Michel Malo, Donna KirkwoodAbstract:The Silurian–Lower Devonian sequence of the Gaspe Belt at the Laurentia margin south of the Quebec reentrant and St. Lawrence promontory was deposited during the period between the two main orogenies that created the northern Appalachians: the Late Ordovician Taconian and the Middle Devonian Acadian orogenies. Although this sequence is traditionally considered to have been deposited during a period of quiescence between both orogenies, significant tectonic activity attributed to the Salinic disturbance began during late Llandoverian (Telychian) time and persisted until the Acadian Orogeny. This tectonic activity has profoundly influenced the composition and distribution of the Silurian–earliest Devonian sedimentary facies. The shelf and shelf edge history at the Laurentia margin along the Quebec reentrant–St. Lawrence promontory is summarized according to four broad phases. Phase 1 is a Llandoverian–Wenlockian regressive phase (R1) related to post-Taconian successor basin filling, that culminated with extensive carbonate platform development. Phase 2 is a late Wenlockian–Ludlovian transgressive phase (T1). Phase 3 corresponds to a later Ludlovian–Pridolian second regressive phase (R2). Phases 2 and 3 were accompanied by extensional tectonics that produced shelf faulting and block tilting, on top of which block reefs and reef complexes settled and built a reef tract all the way along the Gaspe-Temiscouata shelf. Phase 4 is an Early Devonian phase of accelerated subsidence (transgression T2) affecting the northwestern part of the segment (Quebec reentrant area), while the southeastern part (St. Lawrence promontory area) was already uplifted due to the ongoing collision between Laurentia and the western margin of Gondwana-related terranes to the south. Composition and distribution of sedimentary facies were controlled by the interaction of tectonics, sediment influx, and sea-level fluctuations. Construction of a post-Taconian–pre-Acadian palinspastic map to plot facies has proven to be basic to obtaining a realistic picture of the paleogeography of the shelf and shelf edge of the Gaspe-Temiscouata segment at the margin of the Laurentia craton during the Silurian–earliest Devonian time interval.
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Vertical and fold-axis parallel extension within a slate belt in a transpressive setting, northern Appalachians
Journal of Structural Geology, 1995Co-Authors: Donna Kirkwood, Pierre St-julien, Michel Malo, Pierre TherrienAbstract:Abstract An incremental and finite strain study of a Mid-Paleozoic slate belt in a transpressive setting in Gaspe, Canadian Appalachians, has been undertaken using syntectonic fibers from pyrite-type pressure shadows. Regionally, strain estimates are quite consistent and reflect only slightly higher strain in the central part of the anticlinorial structure defining the slate belt. Extensions of up to 160% vertically and 110% parallel to the fold axis were recorded in the slate belt combined with an estimated overall regional shortening of 80%. The fibers first rotated toward the final position of the cleavage within a vertical section normal to the cleavage, and then rotated from a vertical to a horizontal orientation. This change in fiber orientation observed in cleavage-parallel sections indicates an abrupt change in the incremental stretching direction from sub-vertical to sub-horizontal (fold-axis parallel). The vertical extension is related to folding and cleavage development during coaxial flattening. The horizontal extension reflects the strain imposed on the rocks during regional simple shear which produced strike-slip faulting and further tightening of the folds. Folding, cleavage development, fold-axis parallel extension and faulting are all related to oblique convergence during the Middle Devonian Acadian Orogeny in this part of the Canadian Appalachians and clearly indicate an overall transition from a pure shortening deformation to a simple shear dominant deformation in an overall transpressive setting.
A. J. Anderson - One of the best experts on this subject based on the ideXlab platform.
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Post-orogenic exhumation of an auriferous terrane: the paleoplacer potential of the Early Carboniferous St. Marys Basin, Canadian Appalachians
Mineralium Deposita, 2000Co-Authors: L. C. Jennex, J. B. Murphy, A. J. AndersonAbstract:The St. Marys Basin of mainland Nova Scotia, Canada, consists of Late Devonian–Early Carboniferous clastic rocks of the Horton Group deposited in the waning stages of the ca. 420–360 Ma Acadian Orogeny in the Canadian Appalachians. Clast lithologies and lithogeochemical analyses indicate that the detritus was predominantly derived from the Meguma terrane that occurs to the south of the basin. The Meguma terrane contains abundant mesothermal gold deposits that are coeval with peak magmatic activity from ca. 380 to 370 Ma and underwent rapid uplift and erosion between ca. 370 and 360 Ma. Within the St. Marys Basin, the contact between the lacustrine Little Stewiacke River Formation and the fluviatile Barrens Hills Formation is interpreted to represent a shoreline and a potentially favorable environment for depositing paleoplacer gold. Geochemical analyses of lithologies adjacent to this contact indicate that the siltstones are predominantly derived from Meguma terrane metasedimentary rocks, whereas the sandstones and conglomerates are predominantly derived from Meguma terrane granitoids. Geochemical and mineralogical analysis indicate the accumulation of heavy minerals including zircon and gold. Micron-scale (
Ruiqian Chen - One of the best experts on this subject based on the ideXlab platform.
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linking the Acadian Orogeny with organic rich black shale deposition evidence from the marcellus shale
Marine and Petroleum Geology, 2017Co-Authors: Ruiqian Chen, Shikha SharmaAbstract:Abstract The trace and rare earth elements (REE) analyses were conducted on samples collected from a 30 m core of the Marcellus Shale obtained from Greene County, southwestern Pennsylvania. Our results suggest that organic matter enrichment trends in the Marcellus Shale can be directly linked with the Acadian Orogeny. The Acadian Orogeny has been recognized as a main sediment source for the Marcellus Shale. Synthesis of tectonic history and recent ash bed geochronology, reveals that deposition of the organic carbon-rich (OR) zone (characterized by TOC >4%; located between 2393 m and 2406.5 m core depth) in the studied Marcellus Shale core was coincident with tectonically active and magmatic quiescent period of the Acadian Orogeny (ca. 395–380 Ma). This time period also corresponds to the highest rate of mountain building in the Acadian Orogeny. The light rare earth (LREE) and selected trace elemental (e.g., Ta, Cs) composition of the OR zone sediments is similar to that of the bulk continental crust, supporting the lack of magmatic activity in the source area (i.e. Acadian Orogeny). In contrast, subsequent deposition of the organic carbon-poor (OP) sediments (characterized by TOC
Henry D. Jones - One of the best experts on this subject based on the ideXlab platform.
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Rb–Sr dating of sphalerites from Tennessee and the genesis of Mississippi Valley type ore deposits
Nature, 1990Co-Authors: Shun'ichi Nakai, Alex N. Halliday, Stephen E. Kesler, Henry D. JonesAbstract:MISSISSIPPI Valley type (MVT) ore deposits commonly consist of some combination of lead, zinc and iron sulphides accompanied by barite, fluorite, dolomite and calcite. They are thought to form by fluid expulsion from sedimentary successions^1–3,but their exact origin has remained controversial because of the scarcity of reliable geochronological data. In a recent and widely quoted model the MVT deposits of the central and eastern United States formed as a result of large-scale lateral fluid flow driven by the tectonic squeezing of sedimentary successions during the late Palaeozoic Alleghenian Orogeny (330–250 Myr)^4. Here we report the first direct Rb–Sr dating of sphalerites from an MVT deposit and propose this as a useful geochronological technique for sulphide mineralization with poor age control. Rb–Sr data for sphalerites from Coy mine, East Tennessee, define an isochron age of 377 ± 29 Myr, ruling out any genetic connection with the Alleghenian Orogeny. Instead, MVT mineralization in the eastern United States was apparently generated from fluids expelled during thrusting associated with the older Acadian Orogeny (380–350 Myr).
Dykstra J Eusden - One of the best experts on this subject based on the ideXlab platform.
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timing of the Acadian Orogeny in northern new hampshire
The Journal of Geology, 2000Co-Authors: Dykstra J Eusden, Chris A Guzofski, Alexander C Robinson, Robert D TuckerAbstract:Abstract New U‐Pb geochronology constrains the timing of the Acadian Orogeny in the Central Maine Terrane of northern New Hampshire. Sixteen fractions of one to six grains each of zircon or monazite have been analyzed from six samples: (1) an early syntectonic diorite that records the onset of the Acadian; (2) a schist, a migmatite, and two granites that together record the peak of the Acadian; and (3) a postkinematic pluton that records the end of the Acadian. Zircon from the syntectonic Wamsutta Diorite gives a 207Pb/206Pb age of circa 408 Ma, the time at which the boundary between the deforming orogenic wedge and the foreland basin was in the vicinity of the Presidential Range. This age agrees well with the Emsian position of the northwest migrating Acadian orogenic front and records the beginning of the Acadian in this part of the Central Maine Terrane. We propose a possible Acadian tectonic model that incorporates the geochronologic, structural, and stratigraphic data. Monazite from the schist, migma...
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stratigraphy and ductile structure of the presidential range new hampshire tectonic implications for the Acadian Orogeny
Geological Society of America Bulletin, 1996Co-Authors: Dykstra J Eusden, John M Garesche, Aaron H Johnson, Jennamarie Maconochie, Steven P Peters, Jonathan B Obrien, Beth L WidmannAbstract:The Presidential Range of New Hampshire with its unique high relief contains exceptionally well exposed rocks of the Acadian orogenic hinterland. These rocks are within the Central Maine terrane, a belt of complexly metamorphosed and deformed Silurian and Devonian metasedimentary rocks. The Presidential Range lies between regions to the south dominated by refolded nappes and synkinematic high-grade regional metamorphism and regions to the northeast dominated by overlapping multiple deformation and contact metamorphism produced by late- and post-Acadian plutons. To better understand these complex tectonic variations and, in particular, to clearly and accurately determine the effects of the Devonian Acadian Orogeny in a well-exposed region, the bedrock geology in the alpine zone of the Presidential Range was mapped in great detail. The results of the stratigraphic and ductile structural analyses are presented here. Five metasedimentary formations have been recognized and constitute a conformable stratigraphy, which, from oldest to youngest, are the Silurian (?) Rangeley, Perry Mountain, Smalls Falls, and Madrid Formations, and the Devonian (?) Littleton Formation. The Littleton Formation has been subdivided into fifteen different members and three submembers based on variations in bedding style of the schists and quartzites and other lithologic peculiarities. The Madrid, Smalls Falls, and Perry Mountains Formations are extremely thin, consistent with their deposition near the Silurian tectonic hinge. The Rangeley Formation is interpreted as an olistostromal melange and has been subdivided into three different members and six submembers on the basis of lithologic variations in the gneiss and subordinate units. The Presidential Range preserves three phases of ductile folding (F1, F2, and F3) and a single phase of thrust faulting (T1). Well-constrained southeast-, east- or northeast-facing directions and consistent asymmetry of F1 nappe limbs suggest that nappe vergence was easterly. Severe refolding of some nappes resulted during F2 collapse of the nappe pile. The west-vergent (?) Greenough Spring thrust fault truncated F1 and F2 structures and juxtaposed nonmigmatized and migmatized rocks. F3 east-vergent folding dominates the alpine zone and represents the final tightening of Acadian structures, which occurred after early granitic plutonism and prior to the emplacement of postkinematic granitic sheets. The structural and sedimentological evidence supports the existence of a subduction system that was active beginning in the early Silurian on the east flank of the Bronson Hill Anticlinorium with a west-dipping subducting slab geometry. This system persisted throughout the Acadian.
