Flexural Basin Research Articles

Quantitative modelling of the Jurassic‐Holocene subsidence history of the Vulcan Sub‐basin, North West Shelf: Constraints on lithosphere evolution during continental breakup

Flexural isostatic basin modelling techniques allow an insight into the development of subsidence mechanisms associated with crustal extension and the evolution of rift basins. The Vulcan Sub‐basin, which is located in the Timor Sea on the northwest Australian passive continental margin, underwent a period of rifting during the Middle to Late Jurassic with upper crustal extension of β =1, 1, Additional, more regional extension by low‐displacement domino faulting occurred on the Ashmore Platform during the Early Jurassic and has a similar stretching factor. Thermal and flexural isostatic models have been developed for the post‐Triassic structural evolution and subsidence histories across these provinces. These models show a different post‐rift subsidence history to that predicted by McKenzie (1978)‐type subsidence models and suggest that an additional regional thermal anomaly was overprinted on the lithosphere temperature field during Late Jurassic rifting. This produced an initial uplift mechanism, which allowed erosion of the Ashmore Platform, followed by increased post‐rift thermal subsidence, which allowed the development of accommodation space for Cretaceous‐Holocene post‐rift sediments. This thermal anomaly is estimated to have a magnitude equivalent to stretching values of β = 1.5–1.6 across the Ashmore Platform, decreasing to the southwest to β = 1.2 beneath the Londonderry High. The development of this anomaly is coincident with estimates of the timing of breakup of the Australian plate and implies that a regional ductile stretching in the lithospheric mantle and lower crust developed during breakup and which increased towards the continent‐ocean boundary. Therefore, the relationship between upper crustal faulting and total lithosphere stretching, as predicted by the isostatic response and the development of accommodation space, is not a simple one and the discrepancy observed suggests a breakup mechanism along the margin which involves partitioning of upper and lower plate deformation.

New Gravity and Magnetic Anomaly Maps in the Taiwan-Luzon Region and Their Preliminary Interpretation

We have compiled new free-air gravity anomaly (FAA) and magnetic anomaly maps, shedding light on the tectonics in the Taiwan-Luzon region. To have a suitable datum level for both the available gravity and magnetic anomaly data, the set of data from an ACT cruise, conducted during May 27 to June 21, 1996, was chosen as a reference. Based on the cross-over error analysis, all the other data were adjusted accordingly. Some satellite-derived, airborne or land data were also added to the compilation to obtain better coverage. Several major new insights into the Taiwan-Luzon region are revealed by the new maps. (1) A prominent NE-SW trending belt of gravity and magnetic anomalies is present in the onshore and offshore areas of southwestern Taiwan. The Peikang High is located on this belt. (2) Located in the offshore region west of Taiwan and to the north of the belt described above, the Taishi Basin, in contrast, occupies a relatively low FAA area. It could be regarded as a flexural basin on account of the loading of a thrust-and-fold belt in western Taiwan. (3) A probable NW-SE trending old transform fault is well imaged off southwestern Taiwan, which separates the lithosphere (plate) of the South China Sea from a trapped piece of the Philippine Sea plate. (4) Located east of the Luzon Are, the Huatung Basin contains several E-W trending magnetic reversals and two N-S trending old fracture zones. The Huatung Basin is separated from the West Philippine Basin by the 123E Fracture Zone . Accordingly, the Gagua Ridge corresponds to a transverse ridge bounding the 123E Fracture Zone. (5) The Luzon Are is abnormally concave toward the Manila Trench and becomes wider toward the south. The internal deformation of the Luzon Are in terms of several NE-SW discontinuities could be related to its collision with eastern Taiwan, (6) Three previously proposed NW-SE trending strike-slip faults in the southern Okinawa Trough, west of 123...

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Carbonate ramps are the most widespread platform type in the geological record, and the bulk of hydrocarbon-bearing carbonates were deposited in ramp-like settings. Nevertheless, ramps remain one of the more enigmatic carbonate platform types. In contrast to steeper sloped rimmed shelves and isolated buildups, where the factors that controlled their location and development are commonly evident, the controls on ramp development have seldom been clearly demonstrated. This volume is an up-to-date compilation of our understanding of modern and ancient carbonate ramp deposystems from 13 countries. It sheds new light on ramp development and related topics by addressing a number of key issues including: terminology - can we classify ramps? processes - how important are water temperature controls and production-depth profiles? tectonic controls - are ramps by necessity restricted to shallow, flexural basins? sedimentary processes - sediment dispersal versus in situ production origin of ramp reef-mounds evolution of ramps into other platform types The international field of authors present case studies of carbonate ramp deposystems, including new reviews of the southern Arabian Gulf shallow-water deposits, the Brazilian coast, northern UK shelf, as well as studies of Ordovician to Tertiary ramps systems. Also included are examples of the use of modelling in understanding the architecture of ancient carbonate platforms.

The Klagenfurt Basin in the Eastern Alps: an intra-orogenic decoupled flexural basin?

The Klagenfurt Basin is an E-W-trending narrow Sarmation to Quaternary flexural basin formed by flexure of the Austro-Alpine lithosphere by loading through the southerly adjacent Karawanken Mountains in the Eastern Alps (Austria). The tectonic evolution of the basin is kinematically connected to Miocene brittle transpressive dextral strike-slip deformation along the Periadriatic Fault which separates the South Alpine unit from the Austro-Alpine unit in the Eastern Alps. The final NW-directed overthrust of the Karawanken Mountains onto the foreland is characterised by a positive flower structure, which is kinematically linked to dextral transpressive shearing along the Periadriatic Fault. Only a small part of the lithosphere appears to support the regional isostatic response to the load by the Karawanken Mountains. The area is characterised by a crustal thickness between 40 and 45 km, elevated heat flow and a strength distribution which suggests that only the upper crust elastically supports the topographic load. Ductile flow of the lower crust is also supported by the absence of a crustal root beneath the Karawanken chain. Rheologic models for this lithospheric configuration indicate a mechanical decoupling of upper crust, lower crust and mantle and generally low strengths for the lower crust and mantle.

Rheology of the Indian and Tarim plates in the Karakoram continent-to-continent collision zone

Bouguer gravity anomalies in the region of Western Himalayas, Karakoram and Tien Shan show large negative values, but classical isostatic models are insufficient to account for the detailed pattern of the observed anomalies. In the past years the gravimetric surveys in the Karakoram done by Marussi, Caputo and others in 1954 have been extended and intensified. The full body of available gravimetric data, including the pendulum observations by De Filippi and Hedin at the beginning of this century, have been re-analyzed. Terrain corrections have been computed systematically for all available data using a unique algorithm and Digital Terrain Model. The isostatic anomalies along a profile from the Indo-Gangetic foredeep, across the Karakoram range and terminating in the Tarim basin show the oscillating values already noted by Marussi. It is here proposed that this oscillatory pattern can be explained by a model in which the convergent boundaries of the Indian and Tarim plates deform by elastic flexure, besides isostasy. The gravity data constrain the numerical values of the model parameters, particularly the flexural rigidity of the plates. For the Indian plate the best fitting value of the flexural rigidity is D = 5 1024 N m, a value very similar to those reported in Central Himalaya. The flexural rigidity of the Tarim plate turns out to be considerably larger D = 7 1025 N m, which makes the Tarim more rigid than the neighboring Central Tibet. Both plates are loaded by an estimated shear stress of 7 1012 N m-1 located in a region corresponding to the Nanga Parbat Haramosh syntaxis. It is concluded that the Indo-Asian continental collision in the Western Himalaya and Karakoram resulted in the development of flexural basins on both sides, unlike the Central Himalaya where the collision produced a flexural basin, the Ganga basin, to the south and, to the north, the indentation of an isostatically supported Tibetan block with possible rheological layering and eastward lateral extrusion.

Tectonic inheritance, crustal architecture, and contrasting structural styles in the Venezuela Andes

Surface and subsurface data image contrasting structural styles for the two flanks of the Venezuela Andes. In the north, a flexural basin developed in Neogene times between the Andes and the Lake Maracaibo. North verging thrusts are mainly detached in the pre‐Cretaceous substratum and form a deeply buried antiformal stack. Secondary décollement levels occur both in the Upper Cretaceous and Tertiary strata, accounting for the passive roof thrust of a conventional frontal triangle zone. In the south, the Barinas basin hardly compares with a flexural basin. It is largely dominated by both north and south verging basement‐involving structures. Paleogene normal faults are locally inverted, and Caribbean nappes are frequently reactivated or refolded by younger oblique Neogene Andean structures. Seismic profiles in this area also attest to the strong Neogene structural inversion of Upper Jurassic‐Lower Cretaceous grabens. Hercynian, or more likely Early Paleozoic structures account for local preexisting crustal heterogeneities, reactivated during both the Tethyan rifting and the Andean deformations. Two trans‐Andean regional profiles have been balanced and constrained by an inversion of the gravimetric data. They imply a progressive deepening of the northern Moho and a south dipping subduction of the infracontinental lithospheric mantle of the Maracaibo block. The shortening for both sections averages 60 km. Palinspastic restorations assume a relative cylindricity for the deep crustal architecture of the Andes and minimize the possible effects of a progressive right‐lateral escape of the Maracaibo block with respect to stable South America along the Bocono Fault. Strain partitioning during Neogene oblique convergence induced surficial thrust fronts parallel to the plate boundary, strike‐slip motion in the allochthon along the Bocono Fault, and an asymmetric subduction (wedging) at depth.

Plate tectonic setting and genetic types of gas (oil)-bearing basins in China

The plate tectonic setting and genetic types of the gas (oil)-bearing basins in China are studied. Based on the history of break-up and amalgamation of Pangea, the three tectonic evolutionary megastages can be divided and the sedimentary basins in China are classified as Palaeowic and Meso-Cenozoic basins. The Palaeozoic gas (oil) bearing basins are mainly located in intracratonic basins, on which different types of Meso-Cenozoic basins are superimposed, and located in cratonic marginal basins and aulacogens destroyed with a slight degree. In contrast, the Mesozoic and Cenozoic gas (oil)-bearing basins mainly formed in extensional foreland and intracontinental shortening flexural basins.

Tectonic Inheritance, Crustal Architecture and Contrasting Structural Styles along the Northern and Southern Andean Flanks, Venezuela: ABSTRACT

Regional seismic profiles, exploration wells, geological maps and field studies image contrasting structural styles of the northern and southern flank of the Venezuelan Andes. In the north, a flexural basin developed in Neogene times between the Andes and the Maracaibo Lake. North verging thrusts are mainly detached in the pre-Cretaceous substratum and form a deeply buried antiformal stack, whereas secondary decollement levels occur either in the Lower Cretaceous or in the Tertiary, accounting for the passive roof thrusting of the frontal triangle zone. In the south, the Barinas Basin can hardly be compared with a flexural basin. It is largely dominated by basement involved structures, either north or south verging. Tectonic inheritance is obvious, as Paleogene normal faults have been locally inverted, and early Caribbean nappes (Paleogene structures) are frequently reactivated or refolded by younger oblique Andean (Neogene) structures. All these data have been integrated to compile two crustal scale balanced sections which have been constrained by an inversion of the gravimetric data. The Present relief of sections is directly inherited from the Jurassic (Tethyan) rifting event. The southern low land results from the structural inversion of Jurassic extensional structures (thin initial crust), whereas the northern culmination relates to newlymore » created Andean structures (thick Jurassic crust). Whether the Hercynian structures have been or not reactivated during the Tethyan rifting or the Andean deformation, remains an open question. The Hercynian thrusts trend more or less parallels to the younger structures, especially Mesozoic extensional ones which could thus partially result from the negative inversion (collapse) of the Paleozoic edifice.« less

Structural Synthesis and Tectonic Evolution of the Maracaibo and Barinas-Apure Basins, Western Venezuela: ABSTRACT

Seismic profiles have imaged the complex and multiphase geometry of major structures in the Maracaibo and Barinas-Apure basins and foothills of the adjacent orogens. Pre-Mesozoic structuring can be documented in subsurface as a peneplaned south-southeast vergent fold-thrust-belt of Hercynian or Caledonian age. In Jurassic times, rifting developed in connection with the opening of western Tethys and thick continental red beds were deposited in the rift grabens. In Late Cretaceous times, postrift thermal subsidence was subsequently recorded. From Maastrichtian through Eocene times, the obduction of the Tethyan ophiolites and the coeval tectonic accretion of the Caribbean allocthon loaded the South American foreland lithosphere, inducing the development of a flexural basin in the northeastern part of the Maracaibo basin. In Late Eocene and Oligocene times, a major extensional event took place in the East Zulia and Falcon area soon after the Caribbean compressional deformation ceased. Since the Neogene, structuring was related to the Andean orogeny, and the deformation was partially superimposed onto older Paleogene and Jurassic structures. These results, integrated with geochemical and chronostratigraphic models, have been used to understand the evolution of the petroleum system and to improve the play fairway risk assessment for exploration.

Development of the Witwatersrand Basin, South Africa

Abstract The Witwatersrand basin is a large hinterland basin of Archaean age developed on already consolidated continental crust south of the Limpopo plate margin. It is a flexural basin formed southeast of a major thick-skinned thrust system, modified by a second thrust system to the southeast. Studies of several thousand kilometres of seismic data, together with geophysical modelling and new field data, have allowed the thrusts and their associated hanging-wall uplifts to be mapped and dated, relative to sediments of Central Rand age. The basin subsequently underwent extension on large detachment faults. Associated half-grabens are infilled with growth sequences of Platberg sediments and intermediate volcanics. These grabens were inverted during post-Platberg and post-Transvaal times. Studies of the Witwatersrand Basin allow tectonic models to be developed for the Archaean which can be used to help interpret Cenozoic mountain belts.

Development of three genetically related basins associated with detachment-style faulting: Predicted characteristics and an example from the central Mojave Desert, California

Three types of sedimentary basins may develop in large-magnitude detachment-type extensional systems. Possible early Miocene examples of these basin types have been identified in association with northeast-directed extension on the central Mojave metamorphic core complex, southern California. From west to east the basins are (1) the Tropico basin, a flexural basin formed on the unextended footwall behind, and bounded by, the detachment breakaway zone; (2) the Pickhandle basin, a supradetachment half graben bounded to the southwest by the detachment breakaway and to the northeast by the hanging wall; and (3) the Clews basin, an intra-hanging-wall basin that formed on the upper plate of the detachment system. Different basin types may be recognized by the nature and geometry of their strata. The footwall flexural basin should be shallow and areally extensive, with basin fill dominated by fine-grained, low-energy deposits. The supradetachment basin typically will be elongate normal to the extension direction and characterized by a thick sequence of volcanic and coarse-grained deposits that reflect its fault-controlled margins. Intra-hanging-wall basins may be of half- or full-graben geometry and will vary in dimension depending on the spacing of the transfer elements. Recognition of these basin types is potentially useful in delineating features of the extensional system that are important to its reconstruction, including the detachment breakaway zone and the boundaries of the extensional system parallel and normal to the extension direction.

Active tectonics in southern Xinjiang, China: Analysis of terrace riser and normal fault scarp degradation along the Hotan‐Qira Fault System

The northern piedmont of the western Kunlun mountains (Xinjiang, China) is marked at its easternmost extremity, south of the Hotan‐Qira oases, by a set of normal faults trending N50E for nearly 70 km. Conspicuous on Landsat and SPOT images, these faults follow the southeastern border of a deep flexural basin and may be related to the subsidence of the Tarim platform loaded by the western Kunlun northward overthrust. The Hotan‐Qira normal fault system vertically offsets the piedmont slope by 70 m. Highest fault scarps reach 20 m and often display evidence for recent reactivations about 2 m high. Successive stream entrenchments in uplifted footwalls have formed inset terraces. We have leveled topographic profiles across fault scarps and transverse abandoned terrace risers. The state of degradation of each terrace edge has been characterized by a degradation coefficient τ, derived by comparison with analytical erosion models. Edges of highest abandoned terraces yield a degradation coefficient of 33 ± 4 m2. Profiles of cumulative fault scarps have been analyzed in a similar way using synthetic profiles generated with a simple incremental fault scarp model. The analysis shows that (1) rate of fault slip remained essentially constant since the aggradation of the piedmont surface and (2) the occurrence of inset terraces was synchronous at all studied sites, suggesting a climate‐driven terrace formation. Observation of glacial and periglacial geomorphic features along the northern front of the western Kunlun range indicates that the Qira glaciofluvial fan emplaced after the last glacial maximum, during the retreat of the Kunlun glaciers (12–22 ka). The age of the most developed inset terrace in uplifted valleys is inferred to be 10 ± 3 ka, coeval with humid climate pulses of the last deglaciation. The mass diffusivity constant (k=τ/T, being time B.P.) in the Hotan region is determined to be 3.3 ± 1.4 m2/103 years, consistent with other estimates in similar climatic and geologic environments of western China. These results imply a minimum rate for the Tarim subsidence of 3.5 ± 2 mm/yr. If Western Kunlun overthrusts the Tarim platform on a crustal ramp dipping 40°–45° to the south, it would absorb at least 4.5 ± 3 mm/yr of convergence between western Tibet and Tarim.

Early Miocene basin evolution in northern Hungary: Tectonics and eustasy

It is presumed that the Oligocene-early Miocene basin evolution in northern Hungary was primarily driven by compressional tectonics, producing a major second-order transgressive-regressive faciès cycle. The early Miocene basin evolution is best understood in terms of “molasse” sedimentation in an overfilled flexural basin. During this time the gradual cessation of thrusting in the adjacent West Carpathian thrust-fold belt resulted in its uplift and subaerial exposure. Significant amounts of sediment were delivered to the flexural basin filling it up to sea level. During the late-stage uplift of the flexural basin a shallow-marine depositional environment developed, as a result of isostatic rebound, and signals of third-order eustatic sea-level changes can be revealed. Sedimentological studies of outcrops of the Lower Miocene succession proved marked changes in facies. Along the gently dipping distal (southeastern) flank of the basin a sudden inception of shallow-marine coarse elastics on top of siltstones, deposited in significantly deeper water, may have been the result of a third-order eustatic sea-level fall shortly before the Burdigalian (at the boundary of the NN1/NN2 nannofossil zones). During the resulting lowstand, various tide-dominated facies aggraded, which were subsequently flooded by the “Burdigalian sea-level rise”. The highstand is represented by upwards shallowing progradational units due to accelerating sedimentation and/or tectonic uplift. The typically elongated and narrow flexural basin, characterized by small water depth, had dimensions which were particularly suitable for the amplification of tidal motions. This resulted in the deposition of tide-influenced sandy sediments. In contrast to examples where the evolution of a strong tidal influence is related to transgressions, here such conditions developed following a drop of sea level.

Paleogene retroarc flexural basin beneath the Neogene Pannonian Basin: A geodynamic model

The Neogene (Middle Miocene-Recent) Pannonian Basin is superimposed on an earlier Paleogene (Middle Eocene-Early Miocene) basin complex as a result of back-arc extension. Although the stratigraphy of the latter is very well known due to raw material exploration, its formation and structural evolution is much less understood. A transtensional origin was generally proposed for the Paleogene Basin of Hungary, assuming an origin analogous to that of the overlying Neogene Pannonian Basin. We suggest an alternative geodynamic scenario for the development of the Paleogene basin complex, as we think that the observations are better understood in terms of a retroarc foredeep basin model. According to this, a flexural basin developed south of the backthrust inner West Carpathian units. The thrust load resulted in a generally deep, underfilled “flysch” basin during Middle Eocene-Early Oligocene times. In the Late Oligocene-Early Miocene predominantly shallow marine and continental deposition occurred indicating the gradual cessation of thrusting in the adjacent thrust-fold belt and the beginning of “molasse” sedimentation. Throughout the whole Paleogene, a shift can be observed of the bathyal, dominantly siliciclastic (in the axis of the foredeep) and neritic, partly carbonate (in the foreland flank of the foredeep) facies belts. This migration of the Middle Eocene-Early Miocene depocenters of the HPB (Hungarian Paleogene Basin) to the east-northeast in present-day coordinates is the result of two processes: 1. (1) the advancement of backthrusting to the southeast; 2. (2) along-strike shift of thrusting to the northeast. While a thin-skinned thrust front can be reconstructed for the Late Eocene (Buda Anticline), the Diósjenö-Hurbanovo line is interpreted as the result of a major thick-skinned thrusting event at the base of the NP24 zone ( $ ̃ 31 Ma). The subsidence pattern, the distinct depositional environments and the structural observations can be more easily integrated into a flexural basin model than into a wrench basin model. Based on the flexural basin model of this work the early Tertiary Western Carpathians formed a compressional arc. While this arc probably developed above a B-subduction zone, during the Late Eocene with a corresponding trench (Magura), a forearc basin (Central Carpathian or Podhale) and a retroarc flexural basin (Hungarian Paleogene), from the Early Oligocene to the Early Miocene it was characterized by A-subduction with a corresponding peripheral foredeep (Dukla and Silesian) and a retroarc flexural basin (Hungarian Paleogene).

Tectonics of the Himalayan collision between the Indian Plate and the Afghan Block: a synthesis

Abstract A synthesis of the available tectonic, structural, magmatic and geochronologic data from Afghanistan and western Pakistan suggests that collision between the Indian Plate and the Afghan Block (a collage of blocks assembled during the Cimmeride orogeny), took place during the Pliocene. Prior to this, the thinned western margin of the Indian Plate, together with the transitional to oceanic crust which separated the Indian Plate from the Afghan Block, was overlain by a wedge of Tertiary clastic sediments deposited in a large flexural basin that included what is now the Katawaz basin as well as the Sulaiman foredeep. At least three phases of collision can thus be recognised in the northwest Himalaya: the first, at about 100 Ma involved the suturing of the Kohistan-Ladakh-East Nuristan island arc to southern Asia; the second, at about 55 Ma involved India-Asia collision and the third, during the Pliocene, involved India-Afghanistan collision. During the Eocene and Miocene, the Afghan block was displaced southwards in response to Indian indentation into Asia. Simultaneous counterclockwise rotation of the Afghan Block resulted in intracontinental extension causing alkaline magmatism and right lateral displacements along the Herat Fault. As the Indian Plate moved northward with respect to Afghanistan, some of the wedge of clastic sediments deposited on the Indian transitional crust were accreted to the leading edge of the Afghan block and displaced sinistrally with respect to the rest of the sediments in the wedge. These displaced sediments now form the Makran sequence. Collisional structures on both sides of the India-Afghan collision zone in the Helmand block and the Sulaiman-Kirthar Ranges probably represent the inversion of continental margin basins rather than thrust belts with large shortening amounts. After initial inversion, the dominant feature of this highly oblique collision has been transpressional tectonics. Prior to its final docking with the Afghan Block, the Kabul block was a continental slice, completely surrounded by oceanic crust, and located northwest of continental India. Palaeocene collision between India and the Kabul block could have led to thickening of the Indian Plate prior to initiation of India-Asia collision.

Alpine Tectonics of the Pannonian Basin

The Neogene evolution of the Pannonian basin is fairly well understood in terms of back-arc extension behind the Carpathian thrust-fold belt. This middle Miocene-Holocene basin, however, is superimposed on an earlier middle Eocene-early Miocene basin traditionally called the Paleogene basin of Hungary. Although the Paleogene stratigraphy of the basin is well known, its structural evolution is not clear; however, a transtensional origin is assumed analogous to the overlying Pannonian basin. The existing data set on the Paleogene basin can be integrated easily into a compressional basin model. Other intra-Carpathian Paleogene basins, such as the Transylvanian and Slovenian basins, are now considered to be flexural in origin. Systematic interpretation of reflection seismic data shows that these Tertiary basins are superimposed on a Cretaceous Alpine thrust-fold belt. The internal geometry of this belt in the basement of the Pannonian basin indicates a close relationship to the surrounding mountain belts (Alps, Carpathians, and Dinarides). Whereas the neogene Pannonian basin is in a mature stage of exploration, the underlying Paleogene flexural basins are much less explored. Furthermore, the Cretaceous thrust-fold belts should be regarded as frontier areas for future oil and gas exploration efforts.

Transition from back-arc to foreland basin development in the southernmost Andes: Stratigraphic record from the Ultima Esperanza District, Chile

Research Article| January 01, 1991 Transition from back-arc to foreland basin development in the southernmost Andes: Stratigraphic record from the Ultima Esperanza District, Chile TERRY J. WILSON TERRY J. WILSON 1Department of Geology and Mineralogy, Ohio State University, Columbus, Ohio 43210 Search for other works by this author on: GSW Google Scholar Author and Article Information TERRY J. WILSON 1Department of Geology and Mineralogy, Ohio State University, Columbus, Ohio 43210 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1991) 103 (1): 98–111. https://doi.org/10.1130/0016-7606(1991)103<0098:TFBATF>2.3.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation TERRY J. WILSON; Transition from back-arc to foreland basin development in the southernmost Andes: Stratigraphic record from the Ultima Esperanza District, Chile. GSA Bulletin 1991;; 103 (1): 98–111. doi: https://doi.org/10.1130/0016-7606(1991)103<0098:TFBATF>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract During the Mesozoic evolution of the southernmost Andes, back-arc basin formation in an extensional setting was followed by foreland basin development in a compressional setting. A stratigraphic record of this tectonic transition is described from Jurassic and Cretaceous rock units exposed in the Patagonian fold-thrust belt at 51°S latitude. Initiation of an extensional deep-marine trough in Late Jurassic time is documented by interstratified rhyolites and marine mudstones in the Tobifera Formation. Development of the Early Cretaceous Rocas Verdes back-arc basin is recorded by Zapata Formation submarine-slope deposits, which draped the west-facing, passively subsiding cratonic margin of the basin. The onset of Andean compressional orogenesis and creation of the Magallanes foreland basin is marked by the influx of coarse-grained sandstone turbidites of the Albian-Cenomanian Punta Barrosa Formation. During Late Cretaceous time, the foreland basin configuration consisted of a narrow foredeep trough bounded by a gently sloping foreland ramp on the craton to the east. This geometry reflects greater flexural subsidence of the stretched and thermally weakened passive back-arc basin margin beneath the load of the obducted Rocas Verdes basin floor. Changes in depositional regime and sediment dispersal patterns in the latest Cretaceous, together with an eastward shift in the Magallanes basin depocenter, record cratonward migration of deformation in the Patagonian fold-thrust belt. Loading of the thicker, cratonic lithosphere caused subsidence of the foreland ramp to form a wide flexural basin. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

The Cenozoic tectonic evolution of Alpine Corsica

During Palaeocene to Early Oligocene times, hinterland and foreland directed thrusts and folds developed in Alpine Corsica in response to the collision of the European continental plate and oceanic crust adjacent to the Adria promontory. The 'Nappes Supérieures' represent fragments of the oceanic lithosphere, emplaced toward the west upon the Eoalpine Schistes lustrés nappes and Hercynian continental basement. The 'Nappes Supérieures' were unaffected by syn-tectonic metamorphism, whilst the underlying Schistes lustrés nappes developed a greenschist facies replacement of blueschist parageneses and the foreland basement of Hercynian Corsica developed prehnite–pumpellyite facies assemblages. Small flexural basins, occupied by continentally derived flysch deposits, developed at the deformation front and were subsequently overridden by ophiolitic and continental nappes. During Oligocene to Early Miocene times there was a change in deformation style with the generation of strike-slip and normal faults. This non-metamorphic deformation event is considered to result from the 30° anticlockwise rotation of Corso–Sardinia relative to the European plate, producing oceanic lithosphere in the Liguro–Provencal back-arc basin and a zone of collision between Corso–Sardinia and Adria. The rotation of Corsica is modelled as resulting from the indentation of the European continental plate by the Adria microplate.

Flexural tectonics of southeastern sicily

An inverse elastic flexural model for foreland basins has been developed and applied to southeastern Sicily. The model employs a non-linear least squares technique to determine the best values for the flexural parameters based on geological and geophysical data, thus avoiding the trial and error approach to parameter determination inherent in forward models. The lithosphere is assumed to act as an elastic plate of finite lenght ( L) and constant flexural rigidity ( D). The plate is anchored at one end in cantilever fashion. Four boundary conditions are necessary for solution of the governing flexural equation: at the fixed end the displacement is zero and the dip angle of the plate is π; on the free end the bending moment is M and the applied load is V. Thus, the plate profile is determined by five parameters, D, L, π, M and V. The model allows for differential lateral loading along the plate, a significant improvement over previous models which assume that the thrust/sediment load is applied at one point at the end of the plate. Sensitivity analysis of parameter determination and uncertainty are also discussed. Cross sections from southeastern Sicily are modeled and in every case the average difference between predicted and observed values is less than 6% of the maximum relief of the basin. The close fits indicate that the subsidence in the region is largely due to elastic flexure of the basement in response to thrust and sediment loading. The results support the contention that two separate basins have developed independently in the region: the Caltanissetta basin, a foredeep depression, and the Ragusa basin, a marginal sag basin. Parameter sensitivity analysis indicates that these two basins have evolved by different tectonic mechanisms. The foredeep is a dominantly flexural basin, while the Ragusa basin has a strong component of isostatic subsidence. In addition, the parameter values and sensitivity patterns are consistent with independent geological information from the region.

Structural evolution of the Ardmore Basin, Oklahoma: Progressive deformation in the foreland of the Ouachita Collision

Synthesis of oil field studies, seismic reflection data, and surface geology has resulted in a reconstruction of the Pennsylvanian evolution of the structural style of fault systems bordering and within the Ardmore Basin in south central Oklahoma. Faults bounding the margins of the basin were part of a broader left‐lateral shear belt that affected southern Oklahoma during the early Pennsylvanian. The mid‐Pennsylvanian and later zone of deformation contracted in southern Oklahoma to concentrate on the Washita Valley‐Eola Robberson fault systems along the northern edge of the basin, and on the Criner Uplift‐Healdton‐Stephens County fault systems along the southern and western side of the basin. Deformation on the floor of the basin was amplified, with left‐lateral strike‐slip faults slicing the basin into a system of rhombohedral blocks. Deformation continued at least into Virgil time (late Pennsylvanian). A two‐dimensional displacement field derived for the middle to late Pennsylvanian deformation reveals that a strong component of transpression affected both the basin‐bounding faults and, by reason of the geometry of their connections to the west, the Wichita Mountain front as well. Broadly spread left‐lateral shear evolved into crustal scale transpression during the Pennsylvanian Period. That progressive contraction of deformation and the change in style correlate with mid‐Pennsylvanian approach and passage of the Ouachita collision along the Ouachita embayment (Thomas, 1983) on the southern margin of the North American craton. Inasmuch as the Ardmore Basin was located at the sharp internal corner of the embay ment, the coincidence suggests that the style of evolution records (1) early far‐field influence of the approaching Ouachita collision during early Pennsylvanian, (2) passage of the suture during mid‐Pennsylvanian, and (3) concentration of foreland deformation at the corner of the embayment as the Arkoma and Fort Worth flexural basins evolved to the south and east during late Pennsylvanian.