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Deborah A. Spratt - One of the best experts on this subject based on the ideXlab platform.
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geometry and kinematic interpretation of a Triangle Zone in the central alberta foothills
2009Co-Authors: Josgre Salazar, Deborah A. Spratt, Don LawtonAbstract:Summary This study shows preliminary results of an integrated structural interpretation of a Triangle Zone in the central Alberta Foothills (Figure 1). A data set comprising 3D seismic data, well logs and surface geology has been interpreted and integrated resulting in a better understanding of the geometry and kinematics of structures in the area.
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The Oldman River Triangle Zone: A Complicated Tectonic Wedge Delineated by New Structural Mapping and Seismic Interpretation
Bulletin of Canadian Petroleum Geology, 1996Co-Authors: Glen S Stockmal, Don C. Lawton, Paul A. Mackay, Deborah A. SprattAbstract:ABSTRACT New structural mapping and seismic interpretation indicate that the Triangle Zone and related structures exposed along and adjacent to the Oldman River, southern Alberta Foothills, comprise a complicated structure involving significant deformation in the hanging wall of the upper detachment. This deformation includes orogen-directed thrusts and large orogen-vergent folds (ca. 1 km amplitude) as well as apparent secondary orogen-directed tectonic wedging. Although duplex structures are interpreted to occupy the interior of the Triangle Zone, the term "passive-roof duplex" is inappropriate due to the degree and nature of deformation above the upper detachment. The upper detachment is best viewed as a structural domain boundary, separating dominantly foreland-directed structures below from dominantly orogen-directed structures above. Multiple levels of detachment have resulted in two "nested" tectonic wedges which show evidence for some synchronous deformation. Our interpretation suggests that a relict Triangle Zone toe may be preserved and exposed along the Oldman River, immediately above the principal upper detachment (the Big Coulee Fault). RESUME Les nouvelles cartes structurelles et interpretations sismiques indiquent que la Zone triangulaire et les structures connexes exposees le long et adjacent a Oldman River, au sud des Foothills de l'Alberta, englobent une structure compliquee impliquant une deformation significative du toit de la faille oblique du decollement superieur. Cette deformation comprend des chevauchements qui se dirigent vers l'orogenese et des larges plis qui s'inclinent vers l'orogenese (ca. amplitude 1 km) ainsi que l'enfoncement tectonique secondaire qui se dirige vers l'orogenese. Meme si les structures de duplex sont interpretees comme occupant l'interieur de la Zone triangulaire, le terme "couverture passive en duplex" n'est pas approprie a cause du degre et de la nature de la deformation au-dessus du decollement superieur. Le decollement superieur est mieux percu comme etant une limite structurelle du domaine, separant les structures dominantes sous-jacentes qui se dirigent vers l'avant-pays des structures dominantes sus-jacentes qui se dirigent vers l'orogene. Les multiples niveaux de decollements ont donne deux enfoncements tectoniques "emboites", ce qui donnent une preuve pour certaines deformations synchrones. Notre interpretation suggerent qu'un front de Zone triangulaire residue est possiblement conserve et expose le long de Oldman River, directement au-dessus du decollement superieur principal (la faille Big Coulee). Traduit par Marie-Louise Tomas
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en echelon geometry and two dimensional model of the Triangle Zone grease creek syncline area alberta
Bulletin of Canadian Petroleum Geology, 1996Co-Authors: Gregory S Soule, Deborah A. SprattAbstract:ABSTRACT The Triangle Zone structure examined in this study is a deformed wedge inserted along a delaminated horizon in the basal Upper Brazeau Formation (Upper Cretaceous clastic unit). The surface expression of the Triangle Zone is an antiform, with an east-dipping thrust cutting through the core of the antiform. Surface antiforms delineate three en echelon structures in the Grease Creek area, with a strike length of approximately 20 km. A comparison of three balanced cross-sections suggests the en echelon surface geometry reflects the changing position of the lower bounding detachment of the intercutaneous wedge. From south to north the structures consistently step eastward. A "relict" Triangle Zone is interpreted beneath the west flank of the Grease Creek Syncline based on interpreted seismic data. The surface culmination of the Wildcat Hills Triangle Zone, located at the deformation front south of the study area, can be traced to the position of this relict Triangle Zone, demonstrating that there are two separate en echelon intercutaneous wedges. An important implication of the en echelon geometry is that it produces closure of the structural traps along strike because individual structures terminate along strike. A composite two-dimensional model of the Triangle Zone is presented from the published models and the Grease Creek study. Important features of this model include a ramp and flat geometry of the upper detachment and upper and lower detachments of the intercutaneous wedge that do not merge. Instead, the toe of the wedge is a Zone between the upper and lower detachments rather than a distinct tip line. The internal geometry of the Triangle Zone structure is hinterland-dipping in the study area. RESUME La structure de la Zone triangulaire dans cette etude est un prisme deforme emboite le long d'un horizon delamine a la base de la Formation du Brazeau superieur (unite clastique du Cretace superieur). L'expression de la surface de la Zone triangulaire est une structure anticlinale, avec un chevauchement qui s'incline vers l'est coupant a travers le noyau de la structure anticlinale. La surface des structures anticlinales trace trois structures en echelon de la region de Grease Creek, avec une longueur de direction d'environ 20 km. Une comparaison des trois coupes transversales equilibrees suggere que la geometrie de la surface en echelon traduit le changement de position du decollement du prisme intercutane bordier inferieur. Du sud au nord les structures plongent regulierement vers l'est. Une Zone triangulaire "relique" est interpretee sous le flanc ouest du pli synclinal de Grease Creek selon les donnees sismiques interpretees. La culmination de surface de la Zone triangulaire Wildcat Hills, situee au front sud de la deformation de la region etudiee, peut etre tracee a la position de cette Zone triangulaire "relique", demontrant qu'il y a deux prismes intercutanes en echelon distincts. Une implication importance de la geometrie en echelon est la creation de fermeture des pieges structuraux le long de l'inclinaison puisque les structures individuelles se terminent le long de l'inclinaison. Un modele compose en deux dimensions de la Zone triangulaire est presente a partir des modeles publies et de l'etude de Grease Creek. Des caracteristiques importantes de ce modele comprennent une rampe et une geometrie aplanie du decollement superieur et des decollements superieur et inferieur du prisme intercutane qui ne fusionnent pas. A la place, le front d'eboulement du prisme est une Zone entre les decollements superieur et inferieur plutot qu'une ligne d'extremite distincte. La geometrie interne de la structure de la Zone triangulaire s'incline vers l'arriere-pays de la region etudiee. Traduit par Marie-Louise Tomas
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seismic interpretation of the Triangle Zone at jumping pound alberta
Bulletin of Canadian Petroleum Geology, 1996Co-Authors: Robin T Slotboom, Donald C Lawton, Deborah A. SprattAbstract:ABSTRACT We interpret the structure at Jumping Pound, Alberta to be a NW-SE-trending antiformal stack of thrust sheets involving Cretaceous rocks that have been wedged into the foreland between two detachments. The lower of these detachments carries carbonate rocks of Mississippian age in its hanging wall. It rises from a flat in the Mississippian Banff Formation and flattens out near the top of the Upper Cretaceous Belly River Formation. An upper detachment rides within the Upper Cretaceous Edmonton Group. Apparently there is no simple branch point connecting the two faults directly in front of the main culmination. Tectonic wedging probably extends a considerable distance to the foreland, where the two faults likely merge. Three major thrust sheets involving Lower to Upper Cretaceous strata have been stacked to form the main culmination of the wedge. The structure is tightly folded at Jumping Pound and broadens northwest along strike. Shortening at the level of the mid-Cretaceous Cardium Formation is greater than that at the level of the Paleozoic section, indicating that much of the shallow section shortening was fed from Paleozoic-involved culminations further to the west (e.g., Jumping Pound West culmination) along a detachment within the Jurassic Fernie Formation. RESUME Nous interpretons la structure a Jumping Pound, Alberta comme etant un pilier anticlinal de duplex qui se dirige vers le NO-SE impliquant des roches du Cretace qui ont ete enfoncees dans l'avant-pays entre deux decollements. Le decollement inferieur contient des roches carbonates du Mississipien dans son toit de faille oblique. Il se souleve d'un bas-fond de la Formation Banff du Mississipien et s'aplatit pres de la partie superieure de la Formation Belly River du Cretace superieur. Le decollement superieur chevauche dans le Groupe Edmonton du Cretace superieur. Il semble qu'il n'existe pas de simple point de ramification reliant les deux failles directement en avant de la culmination principale. Le calage tectonique s'etend probablement pendant une distance considerable vers l'avant-pays ou la fusion des deux failles a probablement eu lieu. Trois couches de chevauchements principales mettant en jeu les strates s'echelonnant du Cretace inferieur au Cretace superieur ont ete empiles de facon a former la culmination principale du prisme. La structure du pli est fermee a Jumping Pound et s'elargit au nord-ouest le long de l'orientation. Le raccourcissement au niveau de la Formation Cardium du Cretace moyen est superieur a ceux au niveau de la section du Paleozoique, indiquant qu'une grande partie de la section du raccourcissement peu profonde a ete alimentee des culminations mettant en jeu des strates du Paleozoique plus a l'Ouest (p. ex. culminaison de Jumping Pound West) le long du decollement dans la Formation Fernie du Jurassique. Traduit par Marie-Louise Tomas
Glen S Stockmal - One of the best experts on this subject based on the ideXlab platform.
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structural style and evolution of the Triangle Zone and external foothills southwestern alberta implications for thin skinned thrust and fold belt mechanics
Bulletin of Canadian Petroleum Geology, 2001Co-Authors: Glen S Stockmal, D Lebel, Margaret E Mcmechan, Paul A. MackayAbstract:ABSTRACT A thin-skinned, NNW-striking, structural Triangle Zone (tectonic wedge) and steep, imbricate, dominantly foreland-vergent thrusts characterize the eastern margin of the Rocky Mountain Foothills belt in southwestern Alberta. Recent 1:50,000 scale mapping indicates that the structure of the Triangle Zone and outer Foothills varies significantly and systematically along strike. These map-scale variations correlate strongly with lateral changes in the structurally involved Cretaceous-Tertiary foreland stratigraphy and the composition of units structurally inserted into the Triangle Zone, and correlate less strongly with lateral changes in topography. These variations probably reflect the influence of mechanical stratigraphy, and perhaps the associated role of surface processes (landscape evolution) active during structural evolution. On the basis of structural style, the Triangle Zone and outer Foothills structures are divisible into three regions between the Oldman River (49°45 N) and Turner Valley (50°40 N), a distance of approximately 80 km. In the southern region, the upper detachment of the Triangle Zone is localized within the mechanically weak Bearpaw Formation, and the structure is characterized by a series of map-scale, dominantly hinterland-vergent structures in its hanging wall. In the central region, the Bearpaw Formation remains the locus of the upper detachment, but the structure is characterized by an absence of hanging-wall structures, resulting in a simpler "passive roof duplex" geometry. The transition between the central and southern regions is marked by an abrupt but continuous eastward shift in the trace of the upper detachment, coincident with exposure of a south-plunging antiformal stack in its footwall that reflects the subsurface presence of Mississippian carbonates carried on the blind Outwest Thrust. In the northern region, strain associated with the upper detachment becomes distributed over a stratigraphically broad Zone (the Longview Deformation Zone), locally over 2 km in width across strike, centred approximately on the northward-thinning Bearpaw shale. The observed structural variations correspond to changes in the lithology of involved units, indicating the importance of "mechanical stratigraphy". However, there is also a correspondence between the change in structural style from the southern to the central region and the topographic expression of Paleocene units (Porcupine Hills Formation) above the upper detachment. This suggests that patterns of syn-deformational erosion, deposition, and lithification may have influenced structural style. "Out-of-sequence" motion is recorded on some faults, as well as reactivation, with deformation apparently accommodated on a number of faults simultaneously. RESUME Une Zone triangulaire de tectonique epidermique mince (biseau tectonique), orientee NNO et des chevauchements fortement pentes, imbriques, a mouvements a dominance vers l'avant-pays caracterisent la marge est de la chaine du Piedmont des montagnes Rocheuses dans le sud-ouest de l'Alberta. La cartographie recente a l'echelle du 1 : 50 000 indique que la structure de la Zone triangulaire et du Piedmont externe varie significativement et systematiquement parallelement a sa direction principale. Ces variations a l'echelle de la carte sont fortement correlees avec des changements lateraux dans la stratigraphie des unites impliquees de maniere structurale du Cretace-Tertiaire de l'avant-pays et la composition des unites inserees de maniere structurale dans la Zone triangulaire, et se correlent moins avec des changements lateraux de la topographie. Ces variations refletent probablement l'influence de la stratigraphie mecanique, et peut-etre le role associe des processus de surface (evolution du relief) qui furent actifs durant l'evolution structurale. End_Page 472------------------------ Sur la base du style structural, les structures de la Zone triangulaire et de la Zone externe du Piemont sont divisibles en trois regions entre la riviere Oldman (49°45 N) et Turner Valley (50°40 N), soit sur une distance approximative de 80 km. Dans la region sud, le decollement superieur de la Zone triangulaire est situe a l'interieur de la Formation de Bearpaw qui est mecaniquement faible, et la structure est caracterisee par une serie de structures a dominance vers l'interieur de la chaine et a l'echelle de la carte, dans son toit. Dans la region centrale, la Formation de Bearpaw demeure le lieu geometrique du decollement superieur, mais la structure est caracterisee par une absence de structure de toit, resultant en une geometrie a 'duplexe de toit passif'. La transition entre les regions du centre et du sud est marquee par un deplacement abrupt et continu vers l'Est de la trace du decollement superieur, coincidant avec l'affleurement d'un empilement structural antiforme et a plongee vers le sud dans son mur qui reflete la presence en subsurface de carbonates du Mississippien charries par le chevauchement aveugle du chevauchement de Outwest. Dans la region du nord, la deformation associee avec le decollement superieur devient distribue sur une Zone stratigraphiquement plus large (la Zone de deformation de Longview), qui a localement plus de 2 km de largeur perpendiculaire a l'axe de la chaine, et centre approximativement sur la Zone d'amincissement vers le Nord du shale de Bearpaw. Les variations structurales observees correspondent a des changements des lithologies des unites impliquees, indiquant l'importance de la 'stratigraphie mecanique'. Toutefois, il y a aussi une correspondance entre le changement du style structural entre les regions du sud et du centre et l'expression topographique des unites du Paleocene (Formation de Porcupine Hills) au-dessus du decollement superieur. Ceci suggere que les patrons d'erosion syn-deformation, le depot et la lithification aient influence le style structural. Le mouvement 'hors-sequence' est enregistre sur certaines des failles, de meme que la reactivation, ou la deformation est apparemment accommodee simultanement par un certain nombre de failles. Traduit par Lynn Gagnon
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abstract variations in structural style of the Triangle Zone and external foothills between oldman river and turner valley southwestern alberta the influence of mechanical stratigraphy
2000Co-Authors: Glen S Stockmal, D Lebel, Margaret E McmechanAbstract:ABSTRACT The eastern margin of the Foothills belt, southwestern Alberta, is characterized by a thin-skinned, north-northwest striking, structural Triangle Zone (tectonic wedge) and steep, imbricated, dominantly foreland-vergent thrusts. New, detailed 1:50,000 scale mapping, undertaken for the Geological Survey of Canada's Southeastern Cordillera NATMAP project (designed to remap the Foothills between the international border and Turner Valley), demonstrates that structures between Oldman River (49°45' N) and Turner Valley (50°40' N) vary significantly. These variations occur in concert with lateral changes in Cretaceous-Tertiary foreland stratigraphy and the composition of units structurally inserted into the Triangle Zone. We interpret these variations to reflect the influence of mechanical stratigraphy. Between Oldman River and Chaffen Creek (50°05' N), deformation is characterized by a series of dominantly hinterland-vergent structures in the hanging wall (east of) the Triangle Zone upper detachment (the Big Coulee Fault Zone), including thrusts and large, kilometre-scale folds and folded thrusts. The upper detachment (a broad regional backthrust shear Zone) lies within the mechanically weak Bearpaw Formation marine shale interval, which locally is greatly thickened structurally. At Chaffen Creek, a smooth and continuous eastward step of the trace of the upper detachment coincides with exposure of a southward-plunging antiformal stack in its footwall. The prominent, orogen-vergent structures in the hanging wall of the upper detachment, characteristic of the southern area, apparently die out at this latitude. Instead, the Triangle Zone resembles a simple passive roof duplex, with the upper detachment remaining within the structurally thickened Bearpaw interval. The antiformal stack reflects the presence at depth of a mechanically competent beam of Mississippian carbonates carried on the blind, foreland-vergent Outwest Thrust. A hanging wall lateral ramp cuts out the carbonates to the south, coincident with the southward plunge of the duplex stack and the eastward swing in the trace of the upper detachment. Lower Cretaceous Blairmore Group rocks are exposed along the crest of the antiformal stack to the north, only 1 km from the trace of the upper detachment. Between Chaffen Creek and Stimson Creek (50°23'), the Triangle Zone continues to resemble a simple passive roof duplex, but the Outwest Thrust splays to the surface and the hinterland-vergent upper detachment in the Bearpaw Formation is apparently offset by younger foreland-vergent thrust(s). A younger hinterland-vergent roof thrust has developed to the east in stratigraphically younger strata at Stimson Creek. Between Pekisko Creek (50°26') and Sheep River (50°40'), the Bearpaw stratigraphic level remains the locus of an internally complex, hinterland-vergent upper detachment Zone. However, the Bearpaw thins substantially from south to north, becoming an increasingly poor detachment to the Triangle Zone; this results in the distribution of shear strain over a broad Zone, involving marginal marine sediments in adjacent units. On Pekisko Creek, primarily hinterland-vergent folds and faults are developed in the overlying St. Mary River Formation, forming a mappable Zone 2 km wide, and on Highwood River (50°32') a similar broad Zone also involves strata of the underlying Belly River Group. This broad, mappable Zone of intense strain may represent a transition to the intercutaneous wedge-style Triangle Zone documented farther north.
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The Oldman River Triangle Zone: A Complicated Tectonic Wedge Delineated by New Structural Mapping and Seismic Interpretation
Bulletin of Canadian Petroleum Geology, 1996Co-Authors: Glen S Stockmal, Don C. Lawton, Paul A. Mackay, Deborah A. SprattAbstract:ABSTRACT New structural mapping and seismic interpretation indicate that the Triangle Zone and related structures exposed along and adjacent to the Oldman River, southern Alberta Foothills, comprise a complicated structure involving significant deformation in the hanging wall of the upper detachment. This deformation includes orogen-directed thrusts and large orogen-vergent folds (ca. 1 km amplitude) as well as apparent secondary orogen-directed tectonic wedging. Although duplex structures are interpreted to occupy the interior of the Triangle Zone, the term "passive-roof duplex" is inappropriate due to the degree and nature of deformation above the upper detachment. The upper detachment is best viewed as a structural domain boundary, separating dominantly foreland-directed structures below from dominantly orogen-directed structures above. Multiple levels of detachment have resulted in two "nested" tectonic wedges which show evidence for some synchronous deformation. Our interpretation suggests that a relict Triangle Zone toe may be preserved and exposed along the Oldman River, immediately above the principal upper detachment (the Big Coulee Fault). RESUME Les nouvelles cartes structurelles et interpretations sismiques indiquent que la Zone triangulaire et les structures connexes exposees le long et adjacent a Oldman River, au sud des Foothills de l'Alberta, englobent une structure compliquee impliquant une deformation significative du toit de la faille oblique du decollement superieur. Cette deformation comprend des chevauchements qui se dirigent vers l'orogenese et des larges plis qui s'inclinent vers l'orogenese (ca. amplitude 1 km) ainsi que l'enfoncement tectonique secondaire qui se dirige vers l'orogenese. Meme si les structures de duplex sont interpretees comme occupant l'interieur de la Zone triangulaire, le terme "couverture passive en duplex" n'est pas approprie a cause du degre et de la nature de la deformation au-dessus du decollement superieur. Le decollement superieur est mieux percu comme etant une limite structurelle du domaine, separant les structures dominantes sous-jacentes qui se dirigent vers l'avant-pays des structures dominantes sus-jacentes qui se dirigent vers l'orogene. Les multiples niveaux de decollements ont donne deux enfoncements tectoniques "emboites", ce qui donnent une preuve pour certaines deformations synchrones. Notre interpretation suggerent qu'un front de Zone triangulaire residue est possiblement conserve et expose le long de Oldman River, directement au-dessus du decollement superieur principal (la faille Big Coulee). Traduit par Marie-Louise Tomas
Paul A. Mackay - One of the best experts on this subject based on the ideXlab platform.
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structural style and evolution of the Triangle Zone and external foothills southwestern alberta implications for thin skinned thrust and fold belt mechanics
Bulletin of Canadian Petroleum Geology, 2001Co-Authors: Glen S Stockmal, D Lebel, Margaret E Mcmechan, Paul A. MackayAbstract:ABSTRACT A thin-skinned, NNW-striking, structural Triangle Zone (tectonic wedge) and steep, imbricate, dominantly foreland-vergent thrusts characterize the eastern margin of the Rocky Mountain Foothills belt in southwestern Alberta. Recent 1:50,000 scale mapping indicates that the structure of the Triangle Zone and outer Foothills varies significantly and systematically along strike. These map-scale variations correlate strongly with lateral changes in the structurally involved Cretaceous-Tertiary foreland stratigraphy and the composition of units structurally inserted into the Triangle Zone, and correlate less strongly with lateral changes in topography. These variations probably reflect the influence of mechanical stratigraphy, and perhaps the associated role of surface processes (landscape evolution) active during structural evolution. On the basis of structural style, the Triangle Zone and outer Foothills structures are divisible into three regions between the Oldman River (49°45 N) and Turner Valley (50°40 N), a distance of approximately 80 km. In the southern region, the upper detachment of the Triangle Zone is localized within the mechanically weak Bearpaw Formation, and the structure is characterized by a series of map-scale, dominantly hinterland-vergent structures in its hanging wall. In the central region, the Bearpaw Formation remains the locus of the upper detachment, but the structure is characterized by an absence of hanging-wall structures, resulting in a simpler "passive roof duplex" geometry. The transition between the central and southern regions is marked by an abrupt but continuous eastward shift in the trace of the upper detachment, coincident with exposure of a south-plunging antiformal stack in its footwall that reflects the subsurface presence of Mississippian carbonates carried on the blind Outwest Thrust. In the northern region, strain associated with the upper detachment becomes distributed over a stratigraphically broad Zone (the Longview Deformation Zone), locally over 2 km in width across strike, centred approximately on the northward-thinning Bearpaw shale. The observed structural variations correspond to changes in the lithology of involved units, indicating the importance of "mechanical stratigraphy". However, there is also a correspondence between the change in structural style from the southern to the central region and the topographic expression of Paleocene units (Porcupine Hills Formation) above the upper detachment. This suggests that patterns of syn-deformational erosion, deposition, and lithification may have influenced structural style. "Out-of-sequence" motion is recorded on some faults, as well as reactivation, with deformation apparently accommodated on a number of faults simultaneously. RESUME Une Zone triangulaire de tectonique epidermique mince (biseau tectonique), orientee NNO et des chevauchements fortement pentes, imbriques, a mouvements a dominance vers l'avant-pays caracterisent la marge est de la chaine du Piedmont des montagnes Rocheuses dans le sud-ouest de l'Alberta. La cartographie recente a l'echelle du 1 : 50 000 indique que la structure de la Zone triangulaire et du Piedmont externe varie significativement et systematiquement parallelement a sa direction principale. Ces variations a l'echelle de la carte sont fortement correlees avec des changements lateraux dans la stratigraphie des unites impliquees de maniere structurale du Cretace-Tertiaire de l'avant-pays et la composition des unites inserees de maniere structurale dans la Zone triangulaire, et se correlent moins avec des changements lateraux de la topographie. Ces variations refletent probablement l'influence de la stratigraphie mecanique, et peut-etre le role associe des processus de surface (evolution du relief) qui furent actifs durant l'evolution structurale. End_Page 472------------------------ Sur la base du style structural, les structures de la Zone triangulaire et de la Zone externe du Piemont sont divisibles en trois regions entre la riviere Oldman (49°45 N) et Turner Valley (50°40 N), soit sur une distance approximative de 80 km. Dans la region sud, le decollement superieur de la Zone triangulaire est situe a l'interieur de la Formation de Bearpaw qui est mecaniquement faible, et la structure est caracterisee par une serie de structures a dominance vers l'interieur de la chaine et a l'echelle de la carte, dans son toit. Dans la region centrale, la Formation de Bearpaw demeure le lieu geometrique du decollement superieur, mais la structure est caracterisee par une absence de structure de toit, resultant en une geometrie a 'duplexe de toit passif'. La transition entre les regions du centre et du sud est marquee par un deplacement abrupt et continu vers l'Est de la trace du decollement superieur, coincidant avec l'affleurement d'un empilement structural antiforme et a plongee vers le sud dans son mur qui reflete la presence en subsurface de carbonates du Mississippien charries par le chevauchement aveugle du chevauchement de Outwest. Dans la region du nord, la deformation associee avec le decollement superieur devient distribue sur une Zone stratigraphiquement plus large (la Zone de deformation de Longview), qui a localement plus de 2 km de largeur perpendiculaire a l'axe de la chaine, et centre approximativement sur la Zone d'amincissement vers le Nord du shale de Bearpaw. Les variations structurales observees correspondent a des changements des lithologies des unites impliquees, indiquant l'importance de la 'stratigraphie mecanique'. Toutefois, il y a aussi une correspondance entre le changement du style structural entre les regions du sud et du centre et l'expression topographique des unites du Paleocene (Formation de Porcupine Hills) au-dessus du decollement superieur. Ceci suggere que les patrons d'erosion syn-deformation, le depot et la lithification aient influence le style structural. Le mouvement 'hors-sequence' est enregistre sur certaines des failles, de meme que la reactivation, ou la deformation est apparemment accommodee simultanement par un certain nombre de failles. Traduit par Lynn Gagnon
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The Oldman River Triangle Zone: A Complicated Tectonic Wedge Delineated by New Structural Mapping and Seismic Interpretation
Bulletin of Canadian Petroleum Geology, 1996Co-Authors: Glen S Stockmal, Don C. Lawton, Paul A. Mackay, Deborah A. SprattAbstract:ABSTRACT New structural mapping and seismic interpretation indicate that the Triangle Zone and related structures exposed along and adjacent to the Oldman River, southern Alberta Foothills, comprise a complicated structure involving significant deformation in the hanging wall of the upper detachment. This deformation includes orogen-directed thrusts and large orogen-vergent folds (ca. 1 km amplitude) as well as apparent secondary orogen-directed tectonic wedging. Although duplex structures are interpreted to occupy the interior of the Triangle Zone, the term "passive-roof duplex" is inappropriate due to the degree and nature of deformation above the upper detachment. The upper detachment is best viewed as a structural domain boundary, separating dominantly foreland-directed structures below from dominantly orogen-directed structures above. Multiple levels of detachment have resulted in two "nested" tectonic wedges which show evidence for some synchronous deformation. Our interpretation suggests that a relict Triangle Zone toe may be preserved and exposed along the Oldman River, immediately above the principal upper detachment (the Big Coulee Fault). RESUME Les nouvelles cartes structurelles et interpretations sismiques indiquent que la Zone triangulaire et les structures connexes exposees le long et adjacent a Oldman River, au sud des Foothills de l'Alberta, englobent une structure compliquee impliquant une deformation significative du toit de la faille oblique du decollement superieur. Cette deformation comprend des chevauchements qui se dirigent vers l'orogenese et des larges plis qui s'inclinent vers l'orogenese (ca. amplitude 1 km) ainsi que l'enfoncement tectonique secondaire qui se dirige vers l'orogenese. Meme si les structures de duplex sont interpretees comme occupant l'interieur de la Zone triangulaire, le terme "couverture passive en duplex" n'est pas approprie a cause du degre et de la nature de la deformation au-dessus du decollement superieur. Le decollement superieur est mieux percu comme etant une limite structurelle du domaine, separant les structures dominantes sous-jacentes qui se dirigent vers l'avant-pays des structures dominantes sus-jacentes qui se dirigent vers l'orogene. Les multiples niveaux de decollements ont donne deux enfoncements tectoniques "emboites", ce qui donnent une preuve pour certaines deformations synchrones. Notre interpretation suggerent qu'un front de Zone triangulaire residue est possiblement conserve et expose le long de Oldman River, directement au-dessus du decollement superieur principal (la faille Big Coulee). Traduit par Marie-Louise Tomas
Ron Foshee - One of the best experts on this subject based on the ideXlab platform.
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structural stratigraphic reconstruction of frontal choctaw Triangle Zone within oklahoma atoka trend early controls pre thrusting on deposition of deep water clastic reservoirs
2007Co-Authors: Dan Cox, Ron FosheeAbstract:A structural and stratigraphic study in S.W. Oklahoma, encompassing approximately 30 townships in Atoka, Coal and Pittsburg counties, was completed, using several hundred wells, surface geologic maps and more than 400 miles of 1980's vintage seismic data. Tsopach maps were made of six Atokan sands, covering various areas, all within a deep water fan setting. Structural balancing was carried out on numerous geologic cross sections of six miles or less, for log correlation of the various reservoirs and structural details within the frontal "Choctaw" Triangle Zone. Two regional cross sections were made based on 12 and 16 miles, respectively, of recent high fold CDP seismic lines, with a minimum of one well per mile control, dipmeter data and surface geology. These cross-sections were reconstructed by line balancing, to illustrate the amount of thrusting in the section and the pre-Penn normal faulting that subtly control the Atoka sands depositional framework. The thickest and most channelized sands are found downthrown to these earlier faults, with this past relationship now obscured by post-Atokan thrusting. * Previously...Sr. Geophysicist-Arkla Exploration, Shreveport, La. ++Previously...Arkla Exploration, Shreveport, La.
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structural stratigraphic reconstruction of frontal open quotes choctaw close quotes Triangle Zone within oklahoma atoka trend early controls prethrusting on deposition of deep water clastic reservoirs
AAPG Bulletin, 1993Co-Authors: Dan Cox, Ron FosheeAbstract:A structural and stratigraphic study in southwestern Oklahoma, encompassing approximately 30 townships in Atoka, Coal, and Pittsburg counties, was done using several hundred wells, surface geologic maps, and more than 400 mi of 1980 seismic data. Isopach maps of six Atokan sands covered various areas, all within a deep-water fan setting. Structural balancing, done on numerous geologic cross sections of six mi or less, allowed correlation of logs of the various reservoirs and structural details within the frontal [open quotes]Choctaw[close quotes] Triangle Zone. Two regional cross sections were made based, respectively. on 12 and 16 mi or recent high-fold common-depth-point seismic lines, with a minimum of one-well-per-mile control, diameter data, and surface geology. These cross sections were reconstructed by line balancing to illustrate the amount of thrusting in the section and the pre-Pennsylvanian normal faulting that subtly controlled the Atoka sands depositional framework. The thickest and most channelized sands are found downthrown to these earlier faults, with is past relationship now obscured by post-Atokan thrusting.
Richard W Allmendinger - One of the best experts on this subject based on the ideXlab platform.
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thrust front Zone of the precordillera argentina a thick skinned Triangle Zone
AAPG Bulletin, 1996Co-Authors: Tomas R Zapata, Richard W AllmendingerAbstract:The frontal thrust Zone of the Precordillera thrust belt of western Argentina only superficially resembles a classical Alberta-style Triangle Zone. In this thick-skinned Triangle Zone, the thrust front is the result of interaction between the eastward-verging, thin-skinned Central Precordillera and the westward-verging, thick-skinned Eastern Precordillera system. The western boundary, formed by the Niquivil thrust plate, has been refolded and faulted by thrust faults from the Eastern Precordillera at several localities. The deformation is still active. We divide the thick-skinned Triangle Zone into three segments based on the system's activity: independent, late interfering, and collision Zones. Balanced cross sections across a thick-skinned Triangle Zone show a uniform s ortening for the Eastern Precordillera (~17 km). The structural geometry suggests multiple reactivation of the main faults. The thick-skinned Triangle Zone began to grow after 2.6 Ma and is still active. Episodic and alternating opposing movement is controlled by buttressing of the thin-skinned thrust system against the basement structures of the Eastern Precordillera.
