R-3 Repository :: Browsing by Author "Oldow, John S."

Browsing by Author "Oldow, John S."

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A seismic stratigraphic and structural interpretation of the middle Paleozoic Ikpikpuk-Umiat Basin, National Petroleum Reserve in Alaska
(1985) Mauch, Elizabeth A.; Bally, Albert W.; Anderson, John B.; Oldow, John S.
The Ikpikpuk-Umiat Basin is located in the eastern NPRA in northern Alaska. The basin overlies the eroded remnants of a Middle Devonian folded belt and contains up to 18, feet of Late Devonian and Mississippian elastics and up to 8 feet of Mississippian and Pennsylvanian carbonates. These sediments were deposited in two depocenters, an older larger depocenter in the southeast primarily composed of the clastic sequence and a younger, smaller depocenter in the northwest predominantly filled with the carbonate sequence. The sediments in the southeastern depocenter were deposited while the basin was undergoing subsidence and extension whereas sediments in the northwest depocenter were deposited during 8n intra-Mississippian compressional event which affected the entire basin. This compressional event is characterized by north vergent thrust faults trending west-northwest across the basin. A number of these thrust faults are reactivated earlier down-to-the-basin normal faults. The Ikpikpuk-Umiat Basin is tentatively interpreted to be part of an A-subduction related backarc region analogous to the Pannonian Basin in Hungary.
A structural study of the Hukou and Hsinchu areas Northwestern Taiwan
(1985) Liu, Chingju; Bally, Albert W.; Oldow, John S.; Anderson, John B.
Northwestern Taiwan, which includes the Kuanyin, Hukou and Hsinchu areas, was initially a part of the continental shelf of the mainland China coast. The Neogene sediments were deposited m gently east-dipping basement in a stable shelf type environment. The sedimentary sequence shows a regional tilt as well as a thickening of strata towards the southeast, the location of the former ocean. The structures which make up the Hukou and Hsinchu areas are located in the frontal edge of the western foothills range. The structure is dominated by simple-step thrust faults. Frequently, the upthrown blocks of the faults are folded and form the typical asymmetrical folds with steeper north/northwest limbs (e.g. the Hukou and Chingtsaohu Anticlines). A possible solution to the structure of western Taiwan is a progressive change from a simple-step thrust fault in the north to more imbricated faults in the foothills to the southeast. This is similiar to the type of imbrication found in the Canadian Rocky Mountain. Based on the assumption of the oblique plate convergence in the Taiwan area, a model with more westerly substructural involvement of pre-Miocene rocks provides a more conservative estimate of the possible amount of the plate shortening in Taiwan than do previously published studies based on the fault-bend folding model.
Geochemistry and regional correlation of pre-tertiary volcanic rocks in West-Central Nevada
(1983) Seidensticker, C. Michael; Oldow, John S.; Leeman, William P.; Lallemant, Hans G. Avé
Isolated exposures of late Paleozoic and Mesozoic volcanic rocks in the Walker Lake region of west-central Nevada are tectonically disrupted, and their interrelationships are uncertain. Recent work has resulted in the recognition of several formations: The Pennsylvanian Shamrock, Permian Black Dyke, Triassic Pamlico, and Cretaceous Gold Range. Each of these formations is characterized, with particular emphasis on lithology, petrography, chemistry, and age. Outcrops of pre-Tertiary volcanic rocks of unknown age are similarly characterized, and several units are thereby correlated with known formations. Geochemical data confirm the presumption that the volcanic rocks formed at a convergent plate boundary. Upper Paleozoic volcanic rocks were created in an island arc system which underwent major deformation during the Early Triassic Sonoma orogeny, whereas Mesozoic volcanic rocks were erupted along an active continental margin and deposited in a back arc basin of the Mesozoic Sierran arc system.
Mesozoic Geology of the Sand Springs Range, West-Central Nevada
(1995) Satterfield, Joseph I.; Oldow, John S.; Sisson, Virginia; Lallemant, Hans G.; Anderson, John B.; Ledley, Tamara Shapiro
Mesozoic structures and rock types mapped at a scale of 1:80000 in the Sand Springs Range (SSR), west-central Nevada, differ from those in adjacent allochthons. SSR structures and rock types contrast with those in better-known exposures in the Sierra Nevada to the west and in the Luning-Fencemaker thrust belt to the east. Cenozoic igneous rocks in the SSR are steeply tilted. However all Cenozoic-pre-Cenozoic contacts are fault or intrusive contacts and Cenozoic structures have not tilted or rotated pre-Cenozoic structures. Pre-Cenozoic rocks include: a) greenschist facies tectonites, b) amphibolite facies tectonites, c) unmetamorphosed Jurassic-Cretaceous basalt, and d) post-tectonic, Late Cretaceous granitoid plutons. Tectonites include: carbonate rocks, black slate/schist, felsic and mafic volcanic and volcanogenic rocks, and intrusive rocks. Three Triassic successions, two Jurassic successions, and three successions of unknown, Mesozoic and/or Paleozoic age are recognized within tectonites in individual fault blocks. Most successions can be placed within an overall Triassic-Jurassic stratigraphic section which appears consistent throughout the Sand Springs lithotectonic assemblage, the allochthon or terrane which includes the SSR. Rock types and depositional environments of the Sand Springs assemblage differ fromage-equivalent sections in adjacent allochthons, implying large displacements on bounding faults. Three generations of Mesozoic structures in the SSR, DI, D2, and D3, are distinguished by direct superposition. Middle-Late Jurassic D, structures include map-and outcrop-scale folds, faults, and pervasive metamorphic foliations and lineations of unknown original orientation. Late Jurassic-Cretaceous D2 structures are northeast-trending map- and outcrop-scale folds and low-angle faults. Late Jurassic-Cretaceous D3 structures are northwest-trending, map- and outcrop-scale folds. An angular unconformity separates tectonites deformed only in D, from Jurassic-Cretaceous basalt only deformed in D2 and D3. D2 and D3 structures are characteristic of the LuningFencemaker thrust belt, while D, structures, which predate D2 by a large time span, are possibly correlative to Middle-Late Jurassic structures widespread in westernmost Nevada and the Sierra Nevada. If DI is a Sierra Nevada deformation event, then Luning-Fencemaker thrusting must postdate Middle-Late Jurassic deformation in the Sierra Nevada.
Sedimentology and structural geology of the Endicott Mountains allochthon, central Brooks Range, Alaska
(1989) Handschy, James William; Oldow, John S.
The Endicott Mountains allochthon is an east-west striking stack of north-northwest vergent thrust sheets which were emplaced during late Mesozoic and Cenozoic (Brookian) orogenesis. Thrust sheets in the allochthon are composed of clastic and carbonate rocks which track the progressive evolution of a Late Devonian and Early Carboniferous continental margin. Sedimentary facies in lower Upper Devonian rocks of the Beaucoup Formation delimit a volcanically active depositional basin. Volcaniclastic sediments within the Beaucoup were apparently derived from the south; whereas siliciclastic sediments were derived from the north. By the late Late Devonian, the Beaucoup depositional basin had developed into a south-facing continental margin. Southwestward progradation of the Kanayut-Hunt Fork delta system deposited thick conglomerates, sandstones, and shales on the margin and created a lithofacies pattern in which the Kanayut Conglomerate is thicker in the north and the Hunt Fork Shale is thicker in the south. Transgression of the Lower Mississippian Kayak Shale over the Kanayut Conglomerate occurred as sea level rose during the Early Mississippian. Subsequent transgressive-regressive cycles in carbonates of the Lisburne Group indicate that the margin had evolved into a stable passive margin by the middle Mississippian. The style of Brookian structures in the Endicott Mountains allochthon changes from imbricate thrust sheets and large single-phase folds in the north to a thick, variably strained thrust nappe in the south. Strain variation in the southern nappe is evidenced by a progressive change from single-phase folds at the top of the nappe to polyphase folds at the bottom. First phase fold axes change from strike-parallel at the top of the nappe to dip-parallel at the bottom, and the angle between first phase axial planes and the basal thrust decreases with depth. The change from thrust imbrication in the north to heterogeneous intranappe strain in the south apparently was controlled by the distribution of sedimentary facies and the extent of tectonic burial. The greater thickness of Kanayut Conglomerate and lack of a superjacent thrust sheet favored thrust imbrication in the north; whereas the greater proportion of shale and tectonic burial beneath the Skajit allochthon favored heterogeneous intranappe deformation in the south. Changes in fold orientation, the number of superposed fold phases, and measured strain in the southern nappe indicate that deformation was facilitated by a combination of layer parallel shortening and simple shear in a collapsing shear zone.
Structural development and kinematic history of ramp-footwall collapse in the Doonerak multiduplex, central Brooks Range, arctic Alaska
(1992) Seidensticker, Charles Michael; Oldow, John S.
The Doonerak multiduplex of the central Brooks Range fold and thrust belt in arctic Alaska developed during footwall collapse beneath the Amawk thrust, which underlies the Endicott Mountains allochthon. The Endicott Mountains allochthon transported Devonian clastic rocks northward over a footwall composed of lower Paleozoic clastic and volcanic rocks of the Apoon assemblage and uppermost Devonian to Carboniferous clastic and carbonate strata. The geometry and kinematic development of the Doonerak multiduplex differ from typical duplex models in that the Doonerak example consists of two stacked duplexes that formed simultaneously. The upper duplex (the Blarney Creek duplex) and the lower duplex (the Apoon duplex) are separated by the Blarney Creek thrust zone, which served both as the floor thrust of the upper duplex and as the roof thrust of the lower duplex. The intervening fault zone between the two stacked duplexes changes character along strike, from that of a sharp tectonic contact to a diffuse zone of distributed shear up to 250 meters thick. In most locations, the fault zone is tens of meters thick and characteristically contains deformed conglomerate. The stratigraphic position of the fault zone was controlled by a thin conglomerate unit which forms the interface between the Apoon assemblage and the overlying clastic and carbonate rocks. The fault zone truncates structures at the base of the upper duplex and at the top of the lower duplex, locally omitting up to 30 meters of section. Where it is broadest, the Blarney Creek fault zone contains interleaved thin slices of both upper-duplex and lower-duplex lithologies.
Structural evolution of metamorphic tectonites beneath the Silver Peak-Lone Mountain detachment fault, west-central Nevada
(1995) Kohler, Gretchen; Oldow, John S.
The Silver Peak Range of west-central Nevada reveals metamorphic tectonites below a low-angle fault deformed in a northwesterly-trending doubly-plunging anticline. The rock units in the region are divided into a lower plate, a Lower Paleozoic upper plate and an Oligocene and younger upper plate. The lower plate assemblage and Lower Paleozoic upper plate rocks share a common structural history, with the exception that peak metamorphic conditions in the lower plate reached lower amphibolite grade, whereas conditions in the upper plate never exceeded lower greenschist facies. Rocks of Oligocene and younger only experienced late-stage brittle deformation which warped the detachment fault into a doubly-plunging anticline. The cooling history of lower plate tectonites and structural evidence from the upper and lower plate rocks indicate an early history associated with Mesozoic thrusting, and a younger history of Miocene extension associated with displacement transfer between the Furnace Creek Fault and Walker Lane Belt.
Structural interpretation of the Tinaquillo peridotite and its country rock, Cojedes State, Venezuela
(1984) Ostos Rosales, Marino; Lallemant, Hans G. Avé; Oldow, John S.; Stormer, J. C.
The Tinaquillo Complex is bordered to the south by the Tinaco Complex, and to the north is separated by a thrust fault from the Cordillera de la Costa belt. The Tinaquillo Complex, consisting mainly of harzburgite and metagabbro, was formed at high temperature (up to 14°C) and presumably at great depth in the upper mantle. The Tinaco Complex consists of meta-igneous and metasedimentary rocks. The Tinaquillo Complex was juxtaposed onto the Tinaco Complex at intermediate crustal levels at temperatures of about 65°C. Structures in the Tinaquillo harzburgites indicate that the juxtaposition was caused by northwesterly directed thrusting. The metamorphism in the Tinaco Complex is clearly not of the contact type, as has been suggested previously, but is a regional metamorphism. Although good age dates are not available, it is suggested that the juxtaposition of the two complexes occurred during Late Paleozoic times, probably related to collision of a volcanic island arc with South America. The juxtaposition of both complexes onto the Cordillera de la Costa belt is probably a Late Cretaceous or Tertiary event and may be related to a collision of another volcanic island arc with South America.
Structure and stratigraphy of lower Paleozoic rocks, Doonerak Window, central Brooks Range, Alaska
(1989) Julian, Frances Elizabeth; Oldow, John S.
Deep structural levels of the Brooks Range thrust belt, and a unique sequence of lower Paleozoic rocks (informally named the Apoon assemblage) are exposed in a structural high near Mount Doonerak. Previous workers interpreted these rocks as autochthonous basement to the Brooks Range thrust belt, and correlated them with rocks of similar age in the North Slope and northeastern Brooks Range. The contact between the Apoon assemblage and the overlying Carboniferous rocks has been called an angular unconformity, with deformation in the lower Paleozoic rocks attributed to Devonian orogenesis. In this study, the Apoon assemblage is subdivided into four fault-bound lithologic units: (1) a fine-grained clastic unit (Pzp); (2) a mixed volcanic and volcaniclastic unit (Pzv); (3) a coarse clastic unit (Pzc); and (4) a pyroclastic volcanic unit (Pza). The rocks in the Doonerak Window contain three phases of folds: an early isoclinal phase overprinted by two less intense folding events. The last two phases of folds are parallel in the Apoon assemblage and the overlying Carboniferous rocks. The first phase of folds, however, is usually discordant. This discordance, and other data, suggest that the contact between the two units is a fault, not an angular unconformity. All three folding phases are probably related to Brookian deformation. A duplex model is proposed to explain the geometry of the structural high. The lack of Devonian structures within the Apoon assemblage affects correlation with other lower Paleozoic rocks in northern Alaska. The North Slope and northeastern Brooks Range show evidence of Devonian deformation, and hence, have a different structural history than the Apoon assemblage. The lithologies (especially volcanics) are also different in these area. The Apoon assemblage seems more closely related to lower Paleozoic rocks of the Skajit and Rosie Creek allochthons which contain related lithologies and show no evidence of Devonian deformation.
Structure and stratigraphy of the Marietta District, Excelsior mountains, west-central Nevada
(1982) Bowen, Corey Scott; Oldow, John S.; Lallemant, Hans G. Avé; Anderson, John B.
A thick sequence of upper Paleozoic and Mesozoic rocks are exposed in the Marietta district of the central Excelsior Mountains, westcentral Nevada. Rocks are divided into allochthonous and autochthonous terranes by the westernmost known extent of the Luning thrust, a regionally extensive thrust surface which juxtaposes pre-Tertiary layered rocks of disparate depositional and deformational histories in the Mina-Hawthorne region of west-central Nevada. The Luning allochthon in the Excelsior Mountains is an imbricate pile of thrust slices each of which is composed of a single formation or single lithologic assemblage. Lithologic units exposed in the allochthon are: (1) the Permian Black Dyke Formation of volcanic island-arc affinity consisting of extrusive and intrusive rocks of mafic to intermediate composition and volcanogenic sedimentary rocks; (2) the Jurassic-Cretaceous (?) Dunlap Formation, consisting of coarse, continentally derived conglomerate and mature quartz-arenite with interbedded shallow marine to intertidal mudstone, siltstone, and carbonates; and (3) rocks of the Marietta assemblage, possibly of Jurassic or Cretaceous age, consisting of mudstone and siltstone with intercalated conglomerate lenses, volcaniclastic sandstone, and minor volcanic flows. The autochthon in the Excelsior Mountains is composed of the Jurassic-Cretaceous (?) Dunlap Formation, compositionally similar to the Dunlap Formation in the overlying allochthon, which overlies the Permian Mina Formation with angular unconformity. The Mina Formation is an interbedded succession of pelite, bedded chert and volcanogenic turbidites of deep marine origin. Two episodes of thrusting and two phases of folding are recognized in the area studied. Folds within the allochthon and the autochthon occur as two superimposed fold sets designated P1 and P2 in order of decreasing age. First phase folds (P1) are northeasterly trending, upright tight to isoclinal major and minor folds with axial plane cleavage. Second phase folds (P2) are northwesterly trending, overturned, open to close minor folds. Three thrust nappes are recognized. Rocks within the nappes are folded in both fold sets and in one case a nappe is folded in second generation (P2) folds. In all other cases, basal thrusts of nappes truncate first and second phase folds indicating displacement after folding. Pre-Tertiary layered rocks in the Marietta district are intruded by Cretaceous granitic rocks on the west and are uncomfortably overlain by Tertiary volcanic rocks on the north. Several Cenozoic high-angle faults cut through the study area.
Structure of the Oxbow area, Oregon and Idaho
(1980) Schmidt, William Jay; Lallemant, Hans G. Avé; Baker, Donald R.; Oldow, John S.
The Lower to Middle(?) Jurassic Dunlap Formation, west-central Nevada: Deposition in actively extending half-graben basins
(1994) Bartel, Richard Lynn; Oldow, John S.
Autochthonous Lower Jurassic synorogenic strata (Dunlap and Water Canyon Formations) in the Pilot and Excelsior Mountains of west-central Nevada were deposited in actively extending half-graben basins. Northwest-trending syndepositional faults and rapid lateral variations in sedimentary facies from southwest to northeast indicate that the basins were northwesterly elongated. Mean northward paleotransport data indicates basins opened to the north. Sand-rich facies were funnelled northwestward down the axis of the basins by subaqueous tractive processes, whereas gravel-rich facies were shed northeastward by submarine fans which formed along the southwestern margins of the basins. Regional stratigraphic and petrographic evidence indicate that several basins existed, and that individual basins were isolated or poorly connected during deposition. Deposition of the Lower Jurassic Dunlap and Water Canyon Formations within half-grabens is in marked contrast to previous interpretations equating basin formation to mid-Mesozoic contraction. Dunlap sedimentation unequivocally predates the formation of Mesozoic folds and thrusts and cannot be used to date the onset of regional shortening. Synorogenic deposition of Lower Jurassic rocks in northwest-trending basins is consistent with widespread extensional systems in the western Great Basin, the Sierra Nevada and the Mojave.
Transition from ductile to brittle conditions and out-of-sequence thrusting, Luning-Fencemaker fold-thrust belt, Paradise Range, western Great Basin
(1989) Chan, Lawrence Ping-Chuen; Oldow, John S.
The western Paradise Range of central Nevada exposes complexly deformed rocks comprising three imbricate nappes of the Pamlico allochthon, which is a part of the regionally extensive Luning-Fencemaker fold-thrust belt of mid-Jurassic to Early Cretaceous age. Mapping and structural analysis reveal a complex deformation history involving dynamothermal metamorphism, out-of-sequence thrusting, and transition from ductile to brittle conditions during progressive deformation. The deformation reflects a spectrum of ductile-to-brittle conditions: from a tectonic thickening stage involving large recumbent folds culminating in ductile conditions during greenschist-amphibolite dynamothermal metamorphism and the development of mylonites; to a progressive ductile-to-brittle transition resulting in the developments of kink bands, polyphase buckle folds and thrust emplacement at relatively shallow structural levels. Fold-thrust relations suggest the development of an out-of-sequence duplex with thrusts cutting the hanging-wall of older and lower thrusts. Four episodes of shortening are recognized on the basis of fold-thrust relations. Deformation commenced in the mid-Jurassic and was completed before intrusion of Late Cretaceous granitoid plutons. The first phase of deformation involves the local inversion of large tracts of Late Triassic and Early Jurassic carbonates, clastics, and volcanic rocks of the Pamlico assemblage in recumbent folds with ultimate tectonic burial to depths of 10-20 km. Ductile structures, consisting of penetrative fabrics, mylonitic shear zones, and major recumbent folds were generated at depth During progressive southeast transport, the ductily deformed rocks were carried to shallower structural levels by thrusts that truncate earlier structures. Buckle folds associated with the thrusts indicate a protracted history of motion parallel to the transport recorded in the ductile structures contained within nappes. Following emplacement the three nappes exposed in the western Paradise Range were folded in tight to open upright folds. The final phase of folds documents a shift in the regional shortening axis from northwest-southeast to southwest-northeast.

Browsing by Author "Oldow, John S."

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