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Foreland Basin (foreland + basin)

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Earth and Environmental Science	100%

Selected Abstracts

Unravelling the multi-stage burial history of the Swiss Molasse Basin: integration of apatite fission track, vitrinite reflectance and biomarker isomerisation analysis

BASIN RESEARCH, Issue 1 2006
Martin Mazurek
ABSTRACT A complex basin evolution was studied using various methods, including thermal constraints based on apatite fission-track (AFT) analysis, vitrinite reflectance (VR) and biomarker isomerisation, in addition to a detailed analysis of the regional stratigraphic record and of the lithological properties. The study indicates that (1) given the substantial amount of data, the distinction and characterisation of successive stages of heating and burial in the same area are feasible, and (2) the three thermal indicators (AFT, VR and biomarkers) yield internally consistent thermal histories, which supports the validity of the underlying kinetic algorithms and their applicability to natural basins. All data pertaining to burial and thermal evolution were integrated in a basin model, which provides constraints on the thickness of eroded sections and on heat flow over geologic time. Three stages of basin evolution occurred in northern Switzerland. The Permo-Carboniferous strike,slip basin was characterised by high geothermal gradients (80,100°C km,1) and maximum temperature up to 160°C. After the erosion of a few hundreds of metres in the Permian, the post-orogenic, epicontinental Mesozoic basin developed in Central Europe, with subsidence triggered by several stages of rifting. Geothermal gradients in northern Switzerland during Cretaceous burial were relatively high (35,40°C km,1), and maximum temperature typically reached 75°C (top middle Jurassic) to 100°C (base Mesozoic). At least in the early Cretaceous, a stage of increased heat flow is needed to explain the observed maturity level. After erosion of 600,700 m of Cretaceous and late Jurassic strata during the Paleocene, the wedge-shaped Molasse Foreland Basin developed. Geothermal gradients were low at this time (,20°C km,1). Maximum temperature of Miocene burial exceeded that of Cretaceous burial in proximal parts (<35 km from the Alpine front), but was lower in more distal parts (>45 km). Thus, maximum temperature as well as maximum burial depth ever reached in Mesozoic strata occurred at different times in different regions. Since the Miocene, 750,1050 m were eroded, a process that still continues in the proximal parts of the basin. Current average geothermal gradients in the uppermost 2500 m are elevated (32,47°C km,1). They are due to a Quaternary increase of heat flow, most probably triggered by limited advective heat transport along Paleozoic faults in the crystalline basement. [source]

Different Hydrocarbon Accumulation Histories in the Kelasu-Yiqikelike Structural Belt of the Kuqa Foreland Basin

ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 5 2010
WANG Zhaoming
Abstract: The Kuqa foreland basin is an important petroliferous basin where gas predominates. The Kela-2 large natural gas reservoir and the Yinan-2, Dabei-1, Tuzi and Dina-11 gas reservoirs have been discovered in the basin up to the present. Natural gases in the Kelasu district and the Yinan district are generated from different source rocks indicated by methane and ethane carbon isotopes. The former is derived from both Jurassic and Triassic source rocks, while the latter is mainly from the Jurassic. Based on its multistage evolution and superposition and the intense tectonic transformation in the basin, the hydrocarbon charging history can be divided into the early and middle Himalayan hydrocarbon accumulation and the late Himalayan redistribution and re-enrichment. The heavier carbon isotope composition and the high natural gas ratio of C1/C1,4 indicate that the accumulated natural gas in the early Himalayan stage is destroyed and the present trapped natural gas was charged mainly in the middle and late Himalayan stages. Comparison and contrast of the oils produced in the Kelasu and Yinan regions indicate the hydrocarbon charging histories in the above two regions are complex and should be characterized by multistage hydrocarbon migration and accumulation. [source]

Oil and Gas Accumulation in the Foreland Basins, Central and Western China

ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 2 2010
Yan SONG
Abstract: Foreland basin represents one of the most important hydrocarbon habitats in central and western China. To distinguish these foreland basins regionally, and according to the need of petroleum exploration and favorable exploration areas, the foreland basins in central and western China can be divided into three structural types: superimposed, retrogressive and reformative foreland basin (or thrust belt), each with distinctive petroleum system characteristics in their petroleum system components (such as the source rock, reservoir rock, caprock, time of oil and gas accumulation, the remolding of oil/gas reservoir after accumulation, and the favorable exploration area, etc.). The superimposed type foreland basins, as exemplified by the Kuqa Depression of the Tarim Basin, characterized by two stages of early and late foreland basin development, typically contain at least two hydrocarbon source beds, one deposited in the early foreland development and another in the later fault-trough lake stage. Hydrocarbon accumulations in this type of foreland basin often occur in multiple stages of the basin development, though most of the highly productive pools were formed during the late stage of hydrocarbon migration and entrapment (Himalayan period). This is in sharp contrast to the retrogressive foreland basins (only developing foreland basin during the Permian to Triassic) such as the western Sichuan Basin, where prolific hydrocarbon source rocks are associated with sediments deposited during the early stages of the foreland basin development. As a result, hydrocarbon accumulations in retrogressive foreland basins occur mainly in the early stage of basin evolution. The reformative foreland basins (only developing foreland basin during the Himalayan period) such as the northern Qaidam Basin, in contrast, contain organic-rich, lacustrine source rocks deposited only in fault-trough lake basins occurring prior to the reformative foreland development during the late Cenozoic, with hydrocarbon accumulations taking place relatively late (Himalayan period). Therefore, the ultimate hydrocarbon potentials in the three types of foreland basins are largely determined by the extent of spatial and temporal matching among the thrust belts, hydrocarbon source kitchens, and regional and local caprocks. [source]

Large-scale Migration of Fluids toward Foreland Basins during Collisional Orogeny: Evidence from Triassic Anhydrock Sequences and Regional Alteration in the Middle-Lower Yangtze Area

ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 1 2004
HOU Zengqian
Abstract The middle-lower Yangtze area underwent a series of complex tectonic evolution, such as Hercynian extensional rifting, Indosinian foreland basining, and Yanshanian transpression-transtension, resulting in a large distinctive Cu-Fe-Au metallogenic belt. In the tectonic evolution, large-scale migration and convergence of fluids toward foreland basins induced during the collisional orogeny of the Yangtze and North China continental blocks were of vital importance for the formation of the metallogenic belt. Through geological surveys of the middle-lower Yangtze area, three lines of evidence of large-scale fluid migration are proposed: (1) The extensive dolomitic and silicic alteration penetrating Cambrian-Triassic strata generally occurs in a region sandwiched between the metallogenic belt along the Yangtze River and the Dabie orogenic belt, and in the alteration domain alternately strong and weak alteration zones extend in a NW direction and are controlled by the fault system of the Dabie orogenic belt; it might record the locus of the activities of long-distance migrating fluids. (2) The textures and structures of very thick Middle-Lower Triassic anhydrock sequences in restricted basins along the river reveal the important contribution of the convergence of regional hot brine in restricted basins and the chemical deposition or their formation. (3) Early-Middle Triassic syndepositional iron carbonate sequences and Fe-Cu-Pb-Zn massive sulfide deposits alternate with anhydrock sequences or are separated from the latter, but all of them occur in the same stratigraphic horizon and are intimately associated with each other, being the product of syndeposition of high-salinity hot brine. According to the geological surveys, combined with previous data, the authors propose a conceptual model of fluid migration-convergence and mineralization during the Dabie collisional orogeny. [source]

Oil and Gas Accumulation in the Foreland Basins, Central and Western China

Provenance of siliciclastic and hybrid turbiditic arenites of the Eocene Hecho Group, Spanish Pyrenees: implications for the tectonic evolution of a foreland basin

BASIN RESEARCH, Issue 2 2010
M. A. Caja
ABSTRACT The Eocene Hecho Group turbidite system of the Aínsa-Jaca foreland Basin (southcentral Pyrenees) provides an excellent opportunity to constrain compositional variations within the context of spatial and temporal distribution of source rocks during tectonostratigraphic evolution of foreland basins. The complex tectonic setting necessitated the use of petrographic, geochemical and multivariate statistical techniques to achieve this goal. The turbidite deposits comprise four unconformity-bounded tectonostratigraphic units (TSU), consisting of quartz-rich and feldspar-poor sandstones, calclithites rich in extrabasinal carbonates and hybrid arenites dominated by intrabasinal carbonates. The sandstones occur exclusively in TSU-2, whereas calclithites and hybrid arenites occur in the overlying TSU-3, TSU-4 and TSU-5. The calclithites were deposited at the base of each TSU and hybrid arenites in the uppermost parts. Extrabasinal carbonate sources were derived from the fold-and-thrust belt (mainly Cretaceous and Palaeocene limestones). Conversely, intrabasinal carbonate grains were sourced from foramol shelf carbonate factories. This compositional trend is attributed to alternating episodes of uplift and thrust propagation (siliciclastic and extrabasinal carbonates supplies) and subsequent episodes of development of carbonate platforms supplying intrabasinal detrital grains. The quartz-rich and feldspar-poor composition of the sandstones suggests derivation from intensely weathered cratonic basement rocks during the initial fill of the foreland basin. Successive sediments (calclithites and hybrid arenites) were derived from older uplifted basement rocks (feldspar-rich and, to some extent, rock fragments-rich sandstones), thrust-and-fold belt deposits and from coeval carbonate platforms developed at the basin margins. This study demonstrates that the integration of tectono-stratigraphy, petrology and geochemistry of arenites provides a powerful tool to constrain the spatial and temporal variation in provenance during the tectonic evolution of foreland basins. [source]

Tilting neotectonics of the Guadiamar drainage basin, SW Spain

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 2 2004
Josep M. SalvanyArticle first published online: 23 DEC 200
Abstract The Guadiamar river ,ows from the southern Iberian Massif to the Guadalquivir foreland basin, SW Spain. Its drainage basin displays asymmetries in the stream network, the arrangement of alluvial terraces and the con,guration of the trunk river valley. The stream network asymmetry was studied using morphometric measures of transverse topographic sym-metry, asymmetry factor and drainage basin shape. The alluvial terraces were studied through the lithologic logs of more than a hundred boreholes and ,eld mapping. The morphometric methods demonstrate a regional tectonic tilting toward the SSE, causing both the migration of the Guadiamar river toward the east and the migration of the Guadiamar tributaries toward the southwest. As a consequence of the Guadiamar river migration, an asymmetric valley developed, with a steep eastern margin caused by river dissection, and a gentle western margin where the main alluvial deposits are found. The ages obtained using the 14C analysis of samples from several alluvial deposits show that the river migration, and thus tilting, has occurred during the Holocene as well as earlier in the Quaternary. This interpretation revises the Guadiamar longitudinal fault assumed by previous studies. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Syntectonic infiltration by meteoric waters along the Sevier thrust front, southwest Montana

GEOFLUIDS (ELECTRONIC), Issue 4 2006
A. C. RYGEL
Abstract Structural, petrographic, and isotopic data for calcite veins and carbonate host-rocks from the Sevier thrust front of SW Montana record syntectonic infiltration by H2O-rich fluids with meteoric oxygen isotope compositions. Multiple generations of calcite veins record protracted fluid flow associated with regional Cretaceous contraction and subsequent Eocene extension. Vein mineralization occurred during single and multiple mineralization events, at times under elevated fluid pressures. Low salinity (Tm = ,0.6°C to +3.6°C, as NaCl equivalent salinities) and low temperature (estimated 50,80°C for Cretaceous veins, 60,80°C for Eocene veins) fluids interacted with wall-rock carbonates at shallow depths (3,4 km in the Cretaceous, 2,3 km in the Eocene) during deformation. Shear and extensional veins of all ages show significant intra- and inter-vein variation in ,18O and ,13C. Carbonate host-rocks have a mean ,18OV-SMOW value of +22.2 ± 3, (1,), and both the Cretaceous veins and Eocene veins have ,18O ranging from values similar to those of the host-rocks to as low as +5 to +6,. The variation in vein ,13CV-PDB of ,1 to approximately +6, is attributed to original stratigraphic variation and C isotope exchange with hydrocarbons. Using the estimated temperature ranges for vein formation, fluid (as H2O) ,18O calculated from Cretaceous vein compositions for the Tendoy and Four Eyes Canyon thrust sheets are ,18.5 to ,12.5,. For the Eocene veins within the Four Eyes Canyon thrust sheet, calculated H2O ,18O values are ,16.3 to ,13.5,. Fluid,rock exchange was localized along fractures and was likely coincident with hydrocarbon migration. Paleotemperature determinations and stable isotope data for veins are consistent with the infiltration of the foreland thrust sheets by meteoric waters, throughout both Sevier orogenesis and subsequent orogenic collapse. The cessation of the Sevier orogeny was coincident with an evolving paleogeographic landscape associated with the retreat of the Western Interior Seaway and the emergence of the thrust front and foreland basin. Meteoric waters penetrated the foreland carbonate thrust sheets of the Sevier orogeny utilizing an evolving mesoscopic fracture network, which was kinematically related to regional thrust structures. The uncertainty in the temperature estimates for the Cretaceous and Eocene vein formation prevents a more detailed assessment of the temporal evolution in meteoric water ,18O related to changing paleogeography. Meteoric water-influenced ,18O values calculated here for Cretaceous to Eocene vein-forming fluids are similar to those previously proposed for surface waters in the Eocene, and those observed for modern-day precipitation, in this part of the Idaho-Montana thrust belt. [source]

Infiltration of basinal fluids into high-grade basement, South Norway: sources and behaviour of waters and brines

GEOFLUIDS (ELECTRONIC), Issue 1 2003
S. A. Gleeson
Abstract Quartz veins hosted by the high-grade crystalline rocks of the Modum complex, Southern Norway, formed when basinal fluids from an overlying Palaeozoic foreland basin infiltrated the basement at temperatures of c. 220°C (higher in the southernmost part of the area). This infiltration resulted in the formation of veins containing both two-phase and halite-bearing aqueous fluid inclusions, sometimes with bitumen and hydrocarbon inclusions. Microthermometric results demonstrate a very wide range of salinities of aqueous fluids preserved in these veins, ranging from c. 0 to 40 wt% NaCl equivalent. The range in homogenization temperatures is also very large (99,322°C for the entire dataset) and shows little or no correlation with salinity. A combination of aqueous fluid microthermometry, halogen geochemistry and oxygen isotope studies suggest that fluids from a range of separate aquifers were responsible for the quartz growth, but all have chemistries comparable to sedimentary formation waters. The bulk of the quartz grew from relatively low ,18O fluids derived directly from the basin or equilibrated in the upper part of the basement (T < 200°C). Nevertheless, some fluids acquired higher salinities due to deep wall-rock hydration reactions leading to salt saturation at high temperatures (>300°C). The range in fluid inclusion homogenization temperatures and densities, combined with estimates of the ambient temperature of the basement rocks suggests that at different times veins acted as conduits for influx of both hotter and colder fluids, as well as experiencing fluctuations in fluid pressure. This is interpreted to reflect episodic flow linked to seismicity, with hotter dry basement rocks acting as a sink for cooler fluids from the overlying basin, while detailed flow paths reflected local effects of opening and closing of individual fractures as well as reaction with wall rocks. Thermal considerations suggest that the duration of some flow events was very short, possibly in the order of days. As a result of the complex pattern of fracturing and flow in the Modum basement, it was possible for shallow fluids to penetrate basement rocks at significantly higher temperatures, and this demonstrates the potential for hydrolytic weakening of continental crust by sedimentary fluids. [source]

NEOGENE TECTONIC HISTORY OF THE SUB-BIBANIC AND M'SILA BASINS, NORTHERN ALGERIA: IMPLICATIONS FOR HYDROCARBON POTENTIAL

JOURNAL OF PETROLEUM GEOLOGY, Issue 2 2007
H. L. Kheidri
The southern Bibans region in northern Algeria is located in the external zone of the Tell fold-and-thrust belt. Field observations in this area together with seismic data integrated with previous studies provide evidence for a number of Tertiary deformation phases. Late Eocene Atlassic deformation was followed by Oligocene (?)-Aquitanian-Burdigalian compression, which was associated with the development of a foreland basin in front of a southerly-propagating thrust system. Gravity-driven emplacement of the Tellian nappes over the basin margin probably occurred during the Langhian-Serravallian-Tortonian. The Hodna Mountains structural culmination developed during the Miocene-Pliocene. Analysis of brittle structures points to continued north-south shortening during the Neogene, consistent with convergence between the African and Eurasian Plates. The unconformably underlying Mesozoic-Cenozoic autochthonous sequence in this area contains two potential source rock intervals: Cenomanian-Turonian and Eocene. Reservoir rocks include Lower Cretaceous siliciclastics and Upper Cretaceous to Palaeogene carbonates. Structural style has controlled trap types. Thus traps in the Tell fold-and-thrust belt are associated with folds, whereas structural traps in the Hodna area are associated with reactivated normal faults. In the latter area, there is also some evidence for base-Miocene stratigraphic traps. [source]

THE VENEZUELAN HYDROCARBON HABITAT, PART 2: HYDROCARBON OCCURRENCES AND GENERATED-ACCUMULATED VOLUMES

JOURNAL OF PETROLEUM GEOLOGY, Issue 2 2000
K. H. James
Venezuela's most important hydrocarbon reserves occur in the intermontane Maracaibo Basin and in the Eastern Venezuela foreland basin. Seeps are abundant in these areas. Lesser volumes occur in the Barinas-Apure foreland basin. Most of the oil in these basins was derived from the Upper Cretaceous La Luna Formation in the west and its equivalent, the Querecual Formation, in the east. Minor volumes of oil derived from Tertiary source rocks occur in the Maracaibo and Eastern Venezuela Basins and in the Falcdn area. Offshore, several TCF of methane with some associated condensate are present in the Cadpano Basin, and gas is also present in the Columbus Basin. Oil reserves are present in La Vela Bay and in the Gulf of Paria, and oil has been encountered in the Cariaco Basin. The Gulf of Venezuela remains undrilled. The basins between the Netherlands and Venezuelan Antillian Islands seem to lack reservoirs. Tertiary sandstones provide the most important reservoirs, but production comes also from fractured basement (igneous and metamorphic rocks), from basal Cretaceous sandstones and from fractured Cretaceous limestones. Seals are provided by encasing shales, unconformities, faults and tar plugs. There is a wide variety of structural and stratigraphic traps. The Orinoco Heavy Oil Belt of the Eastern Venezuela Basin, one of the world's largest accumulations (1.2 times 1012 brl) involves stratigraphic trapping provided by onlap and by tar plugging. Stratigraphic trapping involving unconformities and tar plugging also plays a major role also in the Bolivar Coastal complex of fields along the NE margin of Lake Maracaibo. Many of the traps elsewhere in the Maracaibo Basin were influenced by faulting. The faults played an extensional role during Jurassic rifting and subsequently suffered inversion and strike-slip reactivation. This created anticlines as well as fracture porosity and permeability, and influenced the distribution of sandstone reservoirs, unconformities and related truncation traps. The faults probably also provided migration paths as well as lateral seals. This is very likely the case also in the large, thrust-related traps of the Furrial Trend in Eastern Venezuela. Normal faults, many antithetic to basement dip, provide important traps in the Las Mercedes, Oficina and Emblador complexes on the southern flanks of the Eastern Venezuela Basin. Similar faults seem to control the Sinco-Silvestre complex of the Barinas-Apure Basin. Much of VenezuelaS crude (around 1.5 trillion brls original STOIIP) has been degraded and is heavy, Perhaps two to three trillion brls of precursor, lighter oil existed. While the known Upper Cretaceous La Luna and Querecual Formations are known to include prolific source rocks, a reasonable generation/accumulation efficiency of 10% implies volumes too large to have come from the reported kitchens. The country's vast reserves are perhaps better explained by recognizing that the present-day basins are remnants of much broader sedimentary areas. The source rocks originally had a much more regional distribution. They suffered widespread, earlier phases of generation that probably charged early-formed traps on a regional scale. These, together with more recent kitchens, provided oil to the present-day accumulations. This history involved long-distance migration and remigration. [source]

Importance of predecessor basin history on sedimentary fill of a retroarc foreland basin: provenance analysis of the Cretaceous Magallanes basin, Chile (50,52°S)

BASIN RESEARCH, Issue 5 2010
B. W. Romans
ABSTRACT An integrated provenance analysis of the Upper Cretaceous Magallanes retroarc foreland basin of southern Chile (50°30,,52°S) provides new constraints on source area evolution, regional patterns of sediment dispersal and depositional age. Over 450 new single-grain detrital-zircon U-Pb ages, which are integrated with sandstone petrographic and mudstone geochemical data, provide a comprehensive detrital record of the northern Magallanes foreland basin-filling succession (>4000-m-thick). Prominent peaks in detrital-zircon age distribution among the Punta Barrosa, Cerro Toro, Tres Pasos and Dorotea Formations indicate that the incorporation and exhumation of Upper Jurassic igneous rocks (ca. 147,155 Ma) into the Andean fold-thrust belt was established in the Santonian (ca. 85 Ma) and was a significant source of detritus to the basin by the Maastrichtian (ca. 70 Ma). Sandstone compositional trends indicate an increase in volcanic and volcaniclastic grains upward through the basin fill corroborating the interpretation of an unroofing sequence. Detrital-zircon ages indicate that the Magallanes foredeep received young arc-derived detritus throughout its ca. 20 m.y. filling history, constraining the timing of basin-filling phases previously based only on biostratigraphy. Additionally, spatial patterns of detrital-zircon ages in the Tres Pasos and Dorotea Formations support interpretations that they are genetically linked depositional systems, thus demonstrating the utility of provenance indicators for evaluating stratigraphic relationships of diachronous lithostratigraphic units. This integrated provenance dataset highlights how the sedimentary fill of the Magallanes basin is unique among other retroarc foreland basins and from the well-studied Andean foreland basins farther north, which is attributed to nature of the predecessor rift and backarc basin. [source]

Insights in the exhumation history of the NW Zagros from bedrock and detrital apatite fission-track analysis: evidence for a long-lived orogeny

BASIN RESEARCH, Issue 5 2010
Stéphane Homke
ABSTRACT We present the first fission-track (FT) thermochronology results for the NW Zagros Belt (SW Iran) in order to identify denudation episodes that occurred during the protracted Zagros orogeny. Samples were collected from the two main detrital successions of the NW Zagros foreland basin: the Palaeocene,early Eocene Amiran,Kashkan succession and the Miocene Agha Jari and Bakhtyari Formations. In situ bedrock samples were furthermore collected in the Sanandaj-Sirjan Zone. Only apatite fission-track (AFT) data have been successfully obtained, including 26 ages and 11 track-length distributions. Five families of AFT ages have been documented from analyses of in situ bedrock and detrital samples: pre-middle Jurassic at ,171 and ,225 Ma, early,late Cretaceous at ,91 Ma, Maastrichtian at ,66 Ma, middle,late Eocene at ,38 Ma and Oligocene,early Miocene at ,22 Ma. The most widespread middle,late Eocene cooling phase, around ,38 Ma, is documented by a predominant grain-age population in Agha Jari sediments and by cooling ages of a granitic boulder sample. AFT ages document at least three cooling/denudation periods linked to major geodynamic events related to the Zagros orogeny, during the late Cretaceous oceanic obduction event, during the middle and late Eocene and during the early Miocene. Both late Cretaceous and early Miocene orogenic processes produced bending of the Arabian plate and concomitant foreland deposition. Between the two major flexural foreland episodes, the middle,late Eocene phase mostly produced a long-lasting slow- or nondepositional episode in the inner part of the foreland basin, whereas deposition and tectonics migrated to the NE along the Sanandaj-Sirjan domain and its Gaveh Rud fore-arc basin. As evidenced in this study, the Zagros orogeny was long-lived and multi-episodic, implying that the timing of accretion of the different tectonic domains that form the Zagros Mountains requires cautious interpretation. [source]

Late Cenozoic structural and stratigraphic evolution of the northern Chinese Tian Shan foreland

BASIN RESEARCH, Issue 3 2010
Honghua Lu
ABSTRACT Three successive zones of fault-related folds disrupt the proximal part of the northern Tian Shan foreland in NW China. A new magnetostratigraphy of the Taxi He section on the north limb of the Tugulu anticline in the middle deformed zone clarifies the chronology of both tectonic deformation and depositional evolution of this collisional mountain belt. Our ,1200-m-thick section encompasses the upper Cenozoic terrigenous sequence within which ,300 sampling horizons yield an age span of ,8,2 Ma. Although the basal age in the Taxi He section of the Xiyu conglomerate (often cited as an indicator of initial deformation) is ,2.1 Ma, much earlier growth of the Tugulu anticline is inferred from growth strata dated at ,6.0 Ma. Folding of Neogene strata and angular unconformities in anticlines in the more proximal and distal deformed zones indicate deformation during Miocene and Early Pleistocene times, respectively. In the Taxi He area, sediment-accumulation rates significantly accelerate at ,4 Ma, apparently in response to encroaching thrust loads. Together, growth strata, angular unconformities, and sediment-accumulation rates document the northward migration of tectonic deformation into the northern Tian Shan foreland basin during the late Cenozoic. A progradational alluvial,lacustrine system associated with this northward progression is subdivided into two facies associations at Tugulu: a shallow lacustrine environment before ,5.9 Ma and an alluvial fan environment subsequently. The lithofacies progradation encompasses the time-transgressive Xiyu conglomerate deposits, which should only be recognized as a lithostratigraphic unit. Along the length of the foreland, the locus of maximum shortening shifts between the medial and proximal zones of folding, whereas the total shortening across the foreland remains quite homogeneous along strike, suggesting spatially steady tectonic forcing since late Miocene times. [source]

Influence of the mechanical behaviour of brittle,ductile fold,thrust belts on the development of foreland basins

BASIN RESEARCH, Issue 2 2010
Guy D. H. Simpson
ABSTRACT A two-dimensional mathematical model considering coupling between a deforming elasto-visco-plastic fold,thrust belt, flexural subsidence and diffusional surface processes is solved using the Finite Element Method to investigate how the mechanical behaviour of brittle,ductile wedges influences the development of foreland basins. Results show that, depending mainly on the strength of the basal décollement, two end-member types of foreland basin are possible. When the basal detachment is relatively strong, the foreland basin system is characterised by: (1) Highly asymmetrical orogen formed by thrusts concentrated in the incoming pro-wedge. (2) Sedimentation on retro-side takes place in one major foredeep basin which grows throughout orogen evolution. (3) Deposition on the pro-side occurs initially in the foredeep, and continues in the wedge-top before isolated basins are advected towards the orogen core where they become uplifted and exhumed. (4) Most pro-wedge basins show an upward progression from low altitude, foredeep deposits at the base to high altitude, wedge-top deposits near the surface. In contrast, when the basal detachment behaves weakly due to the presence of low viscosity material such as salt, the foreland basin system is characterised by (1) Broad, low relief orogen showing little preferential vergence and predominance of folding relative to faulting. (2) Deposition mainly in wedge-top basins showing growth strata. (3) Many basins are initiated contemporaneously but form discontinuously due to the locus of active deformation jumping back and forth between different structures. Model results successfully reproduce first order observations of deforming brittle,ductile wedges and foreland basins. Moreover, the results support and provide a framework for understanding the existence of two main end-member foreland basin types, simple and complex, associated with fold,thrust belts whose detachments are relatively strong and weak, respectively. [source]

Provenance of siliciclastic and hybrid turbiditic arenites of the Eocene Hecho Group, Spanish Pyrenees: implications for the tectonic evolution of a foreland basin

Tectonic vs. climate forcing in the Cenozoic sedimentary evolution of a foreland basin (Eastern Southalpine system, Italy)

BASIN RESEARCH, Issue 6 2009
N. Mancin
ABSTRACT This paper discusses the Cenozoic interaction of regional tectonics and climate changes. These processes were responsible for mass flux from mountain belts to depositional basins in the eastern Alpine retro-foreland basin (Venetian,Friulian Basin). Our discussion is based on the depositional architecture and basin-scale depositional rate curves obtained from the decompacted thicknesses of stratigraphic units. We compare these data with the timing of tectonic deformation in the surrounding mountain ranges and the chronology of both long-term trends and short-term high-magnitude (,aberrant') episodes of climate change. Our results confirm that climate forcing (and especially aberrant episodes) impacted the depositional evolution of the basin, but that tectonics was the main factor driving sediment flux in the basin up to the Late Miocene. The depositional rate remained below 0.1 mm year,1 on average from the Eocene to the Miocene, peaking at around 0.36 mm year,1, during periods of maximum tectonic activity in the eastern Southern Alps. This dynamic strongly changed during the Pliocene,Pleistocene, when the basin-scale depositional rate increased to an average of 0.26 mm year,1 (Pliocene) and 0.73 mm year,1 (Pleistocene). This result fits nicely with the long-term global cooling trend recorded during this time interval. Nevertheless, we note that the timing of the observed increase may be connected with the presumed onset of major glaciations in the southern flank of the Alps (0.7,0.9 Ma), the acceleration of the global cooling trend (since 3,4 Ma) and climate variability (in terms of magnitude and frequency). All these factors suggest that combined high-frequency and high-magnitude cooling,warming cycles are particularly powerful in promoting erosion in mid-latitude mountain belts and therefore in increasing the sediment flux in foreland basins. [source]

Evolution of the late Cenozoic Chaco foreland basin, Southern Bolivia

BASIN RESEARCH, Issue 2 2006
Cornelius Eji Uba
ABSTRACT Eastward Andean orogenic growth since the late Oligocene led to variable crustal loading, flexural subsidence and foreland basin sedimentation in the Chaco basin. To understand the interaction between Andean tectonics and contemporaneous foreland development, we analyse stratigraphic, sedimentologic and seismic data from the Subandean Belt and the Chaco Basin. The structural features provide a mechanism for transferring zones of deposition, subsidence and uplift. These can be reconstructed based on regional distribution of clastic sequences. Isopach maps, combined with sedimentary architecture analysis, establish systematic thickness variations, facies changes and depositional styles. The foreland basin consists of five stratigraphic successions controlled by Andean orogenic episodes and climate: (1) the foreland basin sequence commences between ,27 and 14 Ma with the regionally unconformable, thin, easterly sourced fluvial Petaca strata. It represents a significant time interval of low sediment accumulation in a forebulge-backbulge depocentre. (2) The overlying ,14,7 Ma-old Yecua Formation, deposited in marine, fluvial and lacustrine settings, represents increased subsidence rates from thrust-belt loading outpacing sedimentation rates. It marks the onset of active deformation and the underfilled stage of the foreland basin in a distal foredeep. (3) The overlying ,7,6 Ma-old, westerly sourced Tariquia Formation indicates a relatively high accommodation and sediment supply concomitant with the onset of deposition of Andean-derived sediment in the medial-foredeep depocentre on a distal fluvial megafan. Progradation of syntectonic, wedge-shaped, westerly sourced, thickening- and coarsening-upward clastics of the (4) ,6,2.1 Ma-old Guandacay and (5) ,2.1 Ma-to-Recent Emborozú Formations represent the propagation of the deformation front in the present Subandean Zone, thereby indicating selective trapping of coarse sediments in the proximal foredeep and wedge-top depocentres, respectively. Overall, the late Cenozoic stratigraphic intervals record the easterly propagation of the deformation front and foreland depocentre in response to loading and flexure by the growing Intra- and Subandean fold-and-thrust belt. [source]

Linkage of Sevier thrusting episodes and Late Cretaceous foreland basin megasequences across southern Wyoming (USA)

BASIN RESEARCH, Issue 4 2005
Shao-Feng Liu
ABSTRACT Deposition and subsidence analysis, coupled with previous structural studies of the Sevier thrust belt, provide a means of reconstructing the detailed kinematic history of depositional response to episodic thrusting in the Cordilleran foreland basin of southern Wyoming, western interior USA. The Upper Cretaceous basin fill is divided into five megasequences bounded by unconformities. The Sevier thrust belt in northern Utah and southwestern Wyoming deformed in an eastward progression of episodic thrusting. Three major episodes of displacement on the Willard-Meade, Crawford and ,early' Absaroka thrusts occurred from Aptian to early Campanian, and the thrust wedge gradually became supercritically tapered. The Frontier Formation conglomerate, Echo Canyon and Weber Canyon Conglomerates and Little Muddy Creek Conglomerate were deposited in response to these major thrusting events. Corresponding to these proximal conglomerates within the thrust belt, Megasequences 1, 2 and 3 were developed in the distal foreland of southern Wyoming. Two-dimensional (2-D) subsidence analyses show that the basin was divided into foredeep, forebulge and backbulge depozones. Foredeep subsidence in Megasequences 1, 2 and 3, resulting from Willard-Meade, Crawford and ,early' Absaroka thrust loading, were confined to a narrow zone in the western part of the basin. Subsidence in the broad region east of the forebulge was dominantly controlled by sediment loading and inferred dynamic subsidence. Individual subsidence curves are characterized by three stages from rapid to slow. Controlled by relationships between accommodation and sediment supply, the basin was filled with retrogradational shales during periods of rapid subsidence, followed by progradational coarse clastic wedges during periods of slow subsidence. During middle Campanian time (ca. 78.5,73.4 Ma), the thrust wedge was stalled because of wedge-top erosion and became subcritical, and the foredeep zone eroded and rebounded because of isostasy. The eroded sediments were transported far from the thrust belt, and constitute Megasequence 4 that was mostly composed of fluvial and coastal plain depositional systems. Subsidence rates were very slow, because of post-thrusting rebound, and the resulting 2-D subsidence was lenticular in an east,west direction. During late Campanian to early Maastrichtian time, widespread deposits of coarse sediment (the Hams Fork Conglomerate) aggraded the top of the thrust wedge after it stalled, prior to initiation of ,late' Absaroka thrusting. Meanwhile Megasequence 5 was deposited in the Wyoming foreland under the influence of both the intraforeland Wind River basement uplift and the Sevier thrust belt. [source]

Cenozoic stratigraphy and subsidence history of the South China Sea margin in the Taiwan region

BASIN RESEARCH, Issue 4 2003
A. T. Lin
Seismic reflection profiles and well data are used to determine the Cenozoic stratigraphic and tectonic development of the northern margin of the South China Sea. In the Taiwan region, this margin evolved from a Palaeogene rift to a latest Miocene,Recent foreland basin. This evolution is related to the opening of the South China Sea and its subsequent partial closure by the Taiwan orogeny. Seismic data, together with the subsidence analysis of deep wells, show that during rifting (,58,37 Ma), lithospheric extension occurred simultaneously in discrete rift belts. These belts form a >200 km wide rift zone and are associated with a stretching factor, ,, in the range ,1.4,1.6. By ,37 Ma, the focus of rifting shifted to the present-day continent,ocean boundary off southern Taiwan, which led to continental rupture and initial seafloor spreading of the South China Sea at ,30 Ma. Intense rifting during the rift,drift transition (,37,30 Ma) may have induced a transient, small-scale mantle convection beneath the rift. The coeval crustal uplift (Oligocene uplift) of the previously rifted margin, which led to erosion and development of the breakup unconformity, was most likely caused by the induced convection. Oligocene uplift was followed by rapid, early post-breakup subsidence (,30,18 Ma) possibly as the inferred induced convection abated following initial seafloor spreading. Rapid subsidence of the inner margin is interpreted as thermally controlled subsidence, whereas rapid subsidence in the outer shelf of the outer margin was accompanied by fault activity during the interval ,30,21 Ma. This extension in the outer margin (,,1.5) is manifested in the Tainan Basin, which formed on top of the deeply eroded Mesozoic basement. During the interval ,21,12.5 Ma, the entire margin experienced broad thermal subsidence. It was not until ,12.5 Ma that rifting resumed, being especially active in the Tainan Basin (,,1.1). Rifting ceased at ,6.5 Ma due to the orogeny caused by the overthrusting of the Luzon volcanic arc. The Taiwan orogeny created a foreland basin by loading and flexing the underlying rifted margin. The foreland flexure inherited the mechanical and thermal properties of the underlying rifted margin, thereby dividing the basin into north and south segments. The north segment developed on a lithosphere where the major rift/thermal event occurred ,58,30 Ma, and this segment shows minor normal faulting related to lithospheric flexure. In contrast, the south segment developed on a lithosphere, which experienced two more recent rift/thermal events during ,30,21 and ,12.5,6.5 Ma. The basal foreland surface of the south segment is highly faulted, especially along the previous northern rifted flank, thereby creating a deeper foreland flexure that trends obliquely to the strike of the orogen. [source]

Insulating effect of coals and organic rich shales: implications for topography-driven fluid flow, heat transport, and genesis of ore deposits in the Arkoma Basin and Ozark Plateau

BASIN RESEARCH, Issue 2 2002
J.A. Nunn
ABSTRACT Sedimentary rocks rich in organic matter, such as coal and carbonaceous shales, are characterized by remarkably low thermal conductivities in the range of 0.2,1.0 W m,1 °C,1, lower by a factor of 2 or more than other common rock types. As a result of this natural insulating effect, temperature gradients in organic rich, fine-grained sediments may become elevated even with a typical continental basal heat flow of 60 mW m,2. Underlying rocks will attain higher temperatures and higher thermal maturities than would otherwise occur. A two-dimensional finite element model of fluid flow and heat transport has been used to study the insulating effect of low thermal conductivity carbonaceous sediments in an uplifted foreland basin. Topography-driven recharge is assumed to be the major driving force for regional groundwater flow. Our model section cuts through the Arkoma Basin to Ozark Plateau and terminates near the Missouri River, west of St. Louis. Fluid inclusions, organic maturation, and fission track evidence show that large areas of upper Cambrian rocks in southern Missouri have experienced high temperatures (100,140 °C) at shallow depths (< 1.5 km). Low thermal conductivity sediments, such as coal and organic rich mudstone were deposited over the Arkoma Basin and Ozark Plateau, as well as most of the mid-continent of North America, during the Late Palaeozoic. Much of these Late Palaeozoic sediments were subsequently removed by erosion. Our model results are consistent with high temperatures (100,130 °C) in the groundwater discharge region at shallow depths (< 1.5 km) even with a typical continental basal heat flow of 60 mW m,2. Higher heat energy retention in basin sediments and underlying basement rocks prior to basin-scale fluid flow and higher rates of advective heat transport along basal aquifers owing to lower fluid viscosity (more efficient heat transport) contribute to higher temperatures in the discharge region. Thermal insulation by organic rich sediments which traps heat transported by upward fluid advection is the dominant mechanism for elevated temperatures in the discharge region. This suggests localized formation of ore deposits within a basin-scale fluid flow system may be caused by the juxtaposition of upward fluid discharge with overlying areas of insulating organic rich sediments. The additional temperature increment contributed to underlying rocks by this insulating effect may help to explain anomalous thermal maturity of the Arkoma Basin and Ozark Plateau, reducing the need to call upon excessive burial or high basal heat flow (80,100 mW m,2) in the past. After subsequent uplift and erosion remove the insulating carbonaceous layer, the model slowly returns to a normal geothermal gradient of about 30 °C km,1. [source]

Appalachian basin stratigraphic response to convergent-margin structural evolution

BASIN RESEARCH, Issue 4 2001
J. W. Castle
ABSTRACT From study of Palaeozoic formations in the Appalachian foreland basin, a predictive stratigraphic model is proposed based on facies tract development during convergent-margin structural evolution. Five major facies tracts are recognized: shallow-water carbonates that formed during interorogenic quiescence and initial foreland subsidence; deep-water siliciclastics that accumulated in the proximal foreland basin during early collision; syn-collisional shallow-water siliciclastics; syn-collisional, channellized fluvial sandstones that aggraded in the proximal foreland; and progradational shoreline sandstones that were deposited in response to filling of the proximal foreland. Two other facies tracts that occur are organic-rich siliciclastics (,black shales'), which accumulated in oxygen-deficient areas of low clastic-sediment influx, and incised valley-fill deposits, which formed where subsidence rate was low. Because the origin of each facies tract is dependent upon a unique combination of rate of accommodation change and rate of sediment supply, facies tract distribution is predictable from spatial and temporal patterns of subsidence and uplift associated with plate convergence. Alternating phases of thrust loading and quiescence caused fluctuations between underfilled and overfilled conditions during Palaeozoic evolution of the Appalachian basin. Along-strike variations in stratigraphic thickness, facies tract distribution, and development of unconformities in the Appalachian basin reflect the influence of structural irregularities along the collisional margin. In distal parts of the Appalachian foreland and in areas of structural recesses, eustatic influence on stratigraphic patterns is expressed more clearly than in areas of higher subsidence rate. [source]

Modern and ancient fluvial megafans in the foreland basin system of the central Andes, southern Bolivia: implications for drainage network evolution in fold-thrust belts

BASIN RESEARCH, Issue 1 2001
B. K. Horton
ABSTRACT Fluvial megafans chronicle the evolution of large mountainous drainage networks, providing a record of erosional denudation in adjacent mountain belts. An actualistic investigation of the development of fluvial megafans is presented here by comparing active fluvial megafans in the proximal foreland basin of the central Andes to Tertiary foreland-basin deposits exposed in the interior of the mountain belt. Modern fluvial megafans of the Chaco Plain of southern Bolivia are large (5800,22 600 km2), fan-shaped masses of dominantly sand and mud deposited by major transverse rivers (Rio Grande, Rio Parapeti, and Rio Pilcomayo) emanating from the central Andes. The rivers exit the mountain belt and debouch onto the low-relief Chaco Plain at fixed points along the mountain front. On each fluvial megafan, the presently active channel is straight in plan view and dominated by deposition of mid-channel and bank-attached sand bars. Overbank areas are characterized by crevasse-splay and paludal deposition with minor soil development. However, overbank areas also contain numerous relicts of recently abandoned divergent channels, suggesting a long-term distributary drainage pattern and frequent channel avulsions. The position of the primary channel on each megafan is highly unstable over short time scales. Fluvial megafans of the Chaco Plain provide a modern analogue for a coarsening-upward, > 2-km-thick succession of Tertiary strata exposed along the Camargo syncline in the Eastern Cordillera of the central Andean fold-thrust belt, about 200 km west of the modern megafans. Lithofacies of the mid-Tertiary Camargo Formation include: (1) large channel and small channel deposits interpreted, respectively, as the main river stem on the proximal megafan and distributary channels on the distal megafan; and (2) crevasse-splay, paludal and palaeosol deposits attributed to sedimentation in overbank areas. A reversal in palaeocurrents in the lowermost Camargo succession and an overall upward coarsening and thickening trend are best explained by progradation of a fluvial megafan during eastward advance of the fold-thrust belt. In addition, the present-day drainage network in this area of the Eastern Cordillera is focused into a single outlet point that coincides with the location of the coarsest and thickest strata of the Camargo succession. Thus, the modern drainage network may be inherited from an ancestral mid-Tertiary drainage network. Persistence and expansion of Andean drainage networks provides the basis for a geometric model of the evolution of drainage networks in advancing fold-thrust belts and the origin and development of fluvial megafans. The model suggests that fluvial megafans may only develop once a drainage network has reached a particular size, roughly 104 km2, a value based on a review of active fluvial megafans that would be affected by the tectonic, climatic and geomorphologic processes operating in a given mountain belt. Furthermore, once a drainage network has achieved this critical size, the river may have sufficient stream power to prove relatively insensitive to possible geometric changes imparted by growing frontal structures in the fold-thrust belt. [source]

Tectonic Fractures in Tight Gas Sandstones of the Upper Triassic Xujiahe Formation in the Western Sichuan Basin, China

ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 5 2010
ZENG Lianbo
Abstract: The western Sichuan Basin, which is located at the front of the Longmen Mountains in the west of Sichuan Province, China, is a foreland basin formed in the Late Triassic. The Upper Triassic Xujiahe Formation is a tight gas sandstone reservoir with low porosity and ultra-low permeability, whose gas accumulation and production are controlled by well-developed fracture zones. There are mainly three types of fractures developed in the Upper Triassic tight gas sandstones, namely tectonic fractures, diagenetic fractures and overpressure-related fractures, of which high-angle tectonic fractures are the most important. The tectonic fractures can be classified into four sets, i.e., N-S-, NE-, E-W- and NW-striking fractures. In addition, there are a number of approximately horizontal shear fractures in some of the medium-grained sandstones and grit stones nearby the thrusts or slip layers. Tectonic fractures were mainly formed at the end of the Triassic, the end of the Cretaceous and the end of the Neogene-Early Pleistocene. The development degree of tectonic fractures was controlled by lithology, thickness, structure, stress and fluid pressure. Overpressure makes not only the rock shear strength decrease, but also the stress state change from compression to tension. Thus, tensional fractures can be formed in fold-thrust belts. Tectonic fractures are mainly developed along the NE- and N-S-striking structural belts, and are the important storage space and the principal flow channels in the tight gas sandstone. The porosity of fractures here is 28.4% of the gross reservoir porosity, and the permeability of fractures being two or three grades higher than that of the matrix pores. Four sets of high-angle tectonic fractures and horizontal shear fractures formed a good network system and controlled the distribution and production of gas in the tight sandstones. [source]

Oil and Gas Accumulation in the Foreland Basins, Central and Western China

Sedimentary Response of Different Fan Types to the Paleogene,Neogene Basin Transformation in the Kuqa Depression, Tarim Basin, Xinjiang Province

ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 2 2009
Zhiyong GAO
Abstract: A group of alluvial fans formed in the early Paleogene represent marginal sedimentary facies at the foot of the South Tianshan Mountain, Kuqa Depression, Tarim Basin, Xinjiang province. Two types of fans occurred in the middle,late Paleogene Kumugeliemu and Suweiyi formations: one alluvial, and the other fan delta deposited in a lacustrine setting. Within the early Neogene Jidike Formation, coastal subaqueous fans developed, probably in a deeper water lacustrine setting. The three types of fans are stacked vertically in outcrop with the sequence in ascending order: bottom alluvial, middle fan-delta, and top subaqueous. The subaqueous is a typical coarse-fan deposit occurring in the glutinite member of the Jidike Formation in some wells. Laterally, from the foreland to the lacustrine settings, the distribution pattern of sedimentary facies represents the same three fan types sequentially. The spatial distribution of these fans was controlled by the Paleogene,Neogene Basin transformation, and evolution with different types of fans developed in the Kuqa Depression in response. In the Paleogene, the Kuqa Depression was a rift basin where an alluvial fan was deposited in the foreland setting, which, by early Neogene, became a foreland basin when the lake level changed. With any rise in lake level, fan-deltas migrated from lacustrine to foreland settings, whereas when the lake level fell, fan migration was reversed. In the early Neogene, with increasing slope and rising lake level, fans progressed and covered the previous fan-delta and lacustrine mudstone. Eventually, subaqueous fans developed, forming the present spatial configuration of these three fan types. [source]

Structural Characteristics and Formation Mechanism in the Micangshan Foreland, South China

ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 1 2009
Huaming XU
Abstract: Lying at the junction of the Dabashan, Longmenshan and Qinling mountains, the Micangshan Orogenic Belt coupled with a basin is a duplex structure and back-thrust triangular belt with little horizontal displacement, small thrust faults and continuous sedimentary cover. On the basis of 3D seismic data, and through sedimentary and structural research, the Micangshan foreland can be divided into five subbelts, which from north to south are: basement thrust, frontal thrust, foreland depression-back-thrust triangle, foreland fold belt or anticline belt, and the Tongjiang Depression. Along the direction of strike from west to east, the arcuate structural belt of Micangshan can be divided into west, middle and east segments. During the collision between the Qinling and Yangtze plates, the Micangshan Orogenic Belt was subjected to the interaction of three rigid terranes: Bikou, Foping, and Fenghuangshan (a.k.a. Ziyang) terranes. The collision processes of rigid terranes controlled the structural development of the Micangshan foreland, which are: (a) the former collision between the Micangshan-Hannan and Bikou terranes forming the earlier rudiments of the structure; and (b) the later collision forming the main body of the structural belt. The formation processes of the Micangshan Orogenic Belt can be divided into four stages: (1) in the early stage of the Indosinian movement, the Micangshan-Hannan Rigid Terrane was jointed to the Qinling Plate by the clockwise subduction of the Yangtze Plate toward the Qinling Plate; (2) since the late Triassic, the earlier rudiments of the Tongnanba and Jiulongshan anticlines and corresponding syncline were formed by compression from different directions of the Bikou, Foping and Micangshan-Hannan terranes; (3) in the early stage of the Himalayan movement, the Micangshan-Hannan Terrane formed the Micangshan Nappe torwards the foreland basin and the compression stresses were mainly concentrated along both its flanks, whereas the Micangshan-Hannan Terrane wedged into the Qinling Orogenic Belt with force; (4) in the late stage of the Himalayan movement, the main collision of the Qinling Plate made the old basement rocks of the terrane uplift quickly, to form the Micangshan Orogenic Belt. The Micangshan foreland arcuate structure was formed due to the non-homogeneity of terrane movement. [source]

Tectonic Evolution of the Middle Frontal Area of the Longmen Mountain Thrust Belt, Western Sichuan Basin, China

ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 1 2009
Wenzheng JIN
Abstract: By analyzing the balanced cross sections and subsidence history of the Longmen Mountain thrust belt, China, we concluded that it had experienced five tectonic stages: (1) the formation stage (T3x) of the miniature of Longmen Mountain, early Indosinian movement, and Anxian tectonic movement created the Longmen Mountain; (2) the stable tectonic stage (J1) where weaker tectonic movement resulted in the Longmen Mountain thrust belt being slightly uplifted and slightly subsiding the foreland basin; (3) the intense tectonic stage (J2.3), namely the early Yanshan movement; (4) continuous tectonic movement (K-E), namely the late Yanshan movement and early Himalayan movement; and (5) the formation of Longmen Mountain (N-Q), namely the late Himalayan movement. During those tectonic deformation stages, the Anxian movement and Himalayan movement played important roles in the Longmen Mountain's formation. The Himalayan movement affected Longmen Mountain the most; the strata thrust intensively and were eroded severely. There are some klippes in the middle part of the Longmen Mountain thrust belt because a few nappes were pushed southeastward in later tectonic deformation. [source]

Importance of predecessor basin history on sedimentary fill of a retroarc foreland basin: provenance analysis of the Cretaceous Magallanes basin, Chile (50,52°S)