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The Xujiaweizi (XJWZ) fault depression is a primary area for deep-seated gas exploration in Daqing. Through seismic profile interpretation, the main sag-controlling fault and structural characteristics in the XJWZ fault depression were analyzed based on folds and faults analysis. A three-dimensional geological model of the XJWZ fault depression was also set up to enable further discussion by means of structural physical modeling. According to our research, the basic structural framework of the XJWZ fault depression was the result of regional extension. Its formation and evolution were mainly controlled by the Xuxi fault. The structural framework of S-N blocking was due to changes in the fracture attitude. The Xuzhong uplift and the depressions on both sides belong to a normal-fault-related fold and were formed by controlling of the ramp/flat normal fault in the same tectonic movement period. [ABSTRACT FROM AUTHOR]

The late Ediacaran Billy Springs Formation is a little-studied, mudstone-dominated unit deposited in the Adelaide Rift Complex of South Australia. Sediments are exposed in an approximately 11 km × 15 km synclinal structure interpreted as a salt-withdrawal minibasin. The stratigraphic succession is characterized by convolute-laminated slump deposits, rhythmically laminated silty mudstones, rare diamictites and fining-upward turbidite lithofacies. Lithofacies are the product of deposition in a deepwater slope or shelf setting, representing one of the few such examples preserved within the larger basin. Although exact correlations with other formations are unclear, the Billy Springs Formation probably represents the distal portion of a highstand systems tract, and is overlain by coarser sediments of the upper Pound Subgroup. Diamictite intervals are interpreted to be the product of mass flow processes originating from nearby emergent diapirs, in contrast to previous studies that suggest a glacial origin for extrabasinal clasts. Within the spectrum of outcropping minibasins around the world, the sediments described here are unique in their dominantly fine-grained nature and overall lithological homogeneity. Exposures such as these provide an opportunity to better understand the sedimentological processes that operate in these environments, and provide an analogue for similar settings in the subsurface that act as hydrocarbon reservoir-trap systems. [ABSTRACT FROM AUTHOR]

The geochemistry of oil shale units of Hançili Formation in the Çankırı-Çorum Basin (Central Turkey) was studied using various chemical analyses. The mineralogical composition of the samples were preliminarily investigated using Pearson's correlation coefficients of selected elements, indicating that the samples contain abundant clay minerals as well as K-feldspar and carbonate. The K 2 O/Al 2 O 3 and SiO 2 /Al 2 O 3 ratios indicate that the major proportion of clay minerals is composed of smectite. Si, Al, Ti, K, Na, and Fe reside in clay minerals, while Ca, Mg, and Mn are mostly associated with carbonates (e.g., calcite and dolomite) and phosphorous (P) is present as apatite. The total REE content of the oil shale range from 19 to 113 ppm. The chondrite-normalized patterns of the oil shale show LREE enrichments, HREE deficits, negative Eu anomalies and negligible Ce anomalies. In general, major, trace and rare earth element abundances suggest that the studied oil shale in the Çankırı-Çorum Basin are mainly from the intermediate rocks, mixed with small amounts of basic rocks, and that their source rocks are mostly deposited in the continental collision setting. The REE geochemistry of the oil shale suggests that these samples were derived from a consistent terrigenous source and the Eu anomaly was inherited from the source rocks. The paleoclimate index (C-value), varies between 0.07 and 1.22 reflecting a generally semi-arid to humid conditions. In addition, Rb/Sr (~ 0.22) and Sr/Cu (~ 9.09) ratios support the idea that warm and humid conditions prevailed during deposition of the Hançili Formation. Sr/Ba ratios (0.54–3.7) of the studied samples suggest a paleoenvironment with variable salinity. The co-variation among this factor and paleoclimate indicators suggest that variations in climatic conditions exerted a primary control on salinity. The substantially low C-value and Rb/Sr ratio and significantly high ratios of Sr/Cu and Sr/Ba and also elevated carbonate content of four samples indicate that these samples were deposited during hot and arid periods and that the paleoclimate controlled the terrigenous sediment flux to the lake basin. The chemical index of alteration (CIA), A-CN-K ternary diagram, and high Th/U ratios indicate that the parent rocks of the oil shale experienced moderate chemical weathering (steady state). [ABSTRACT FROM AUTHOR]

We report the early Eocene Cambay sedimentation, petrogenesis and tectonics of a rift graben basin of western India using geochemistry. The carbonaceous shales of Tadkeshwar Formation from Tadkeshawar and Rajpardi lignite mines of Cambay basin were studied using major, trace and rare earth elements. The study reveals that the protolith of these shales is likely to be mafic to ultramafic in nature based on the high abundance of Fe 2 O 3 (avg. of 8.68%), MgO (avg. of 5.78%) and TiO 2 (avg. of 8.80%) with a lower SiO 2 content (avg. of 44.74%) when compared to PAAS values. PAAS normalized REE distribution patterns of carbonaceous shales indicate relatively depleted LREE with enriched HREE coupled with small magnitude of Eu/Eu* strongly supports the protolith of these shales to be mafic to ultramafic. Weathering indices confirm these shales were derived from a source subjected to intense weathering. Low Na 2 O and high perseverance of Al 2 O 3 are proxies for Smectite to Illite transformations of shales in a gaining temperature regime across the basin. We speculate that the high geothermal gradients prevailed during 60–65 Ma along the western margin of Indian plate might be responsible for the intense weathering of the marine mafic protolith. Redox-sensitive trace element ratios and negative Ce-anomalies suggest that the shales were deposited under suboxic to oxic environment. The link between early Eocene marine transgression followed by basin subsidence is inferred for the deposition of these carbonaceous shales in suboxic to oxic environments. The immobile trace element ratios and geochemical discrimination diagrams (K 2 O/Na 2 O vs. Si 2 O; La–Th–Sc) reveals, the protoliths of the Tadkeshwar Formation were derived from a transitional domain of intra ocean island arc to active continental margin followed by convergence, leading to the deposition of immature shales. [ABSTRACT FROM AUTHOR]

The tectonic evolution of the Lhasa terrane (southern Tibetan Plateau) played a fundamental role in the formation of the Tibetan Plateau. However, many uncertainties remain with regard to the tectonic and paleogeographic evolution of the Lhasa terrane prior to the India-Asia collision. To determine the early tectonic processes that controlled the topographic evolution of the Lhasa terrane, we analyze the Cretaceous strata exposed in the Coqen Basin (northern Lhasa subterrane), which comprises the Langshan and Daxiong Formations. The Langshan Formation unconformably overlies the volcanic rocks of the Lower Cretaceous Zelong Group and consists of ~80 m of Orbitolina-bearing limestones, which were deposited in a low-energy, shallow marine environment. Micropaleontological analysis indicates that the Langshan Formation in the Coqen Basin was deposited from late Aptian to early Cenomanian times (ca. 113-96 Ma). The overlying Daxiong Formation (~1700 m thick) consists of conglomerate, coarse sandstone, and siltstone with interbedded mud-stone, and represents deposits of alluvial fans and braided rivers. The Daxiong Formation was deposited after the early Cenomanian (ca. 96 Ma) and accumulated until at least ca. 91 Ma, indicating accumulation rates of greater than 0.3 km m.y.-1. By combining paleocurrent data, sandstone petrology, detrital zircon U-Pb ages, and Hf isotope analysis, we demonstrate that the Daxiong Formation was derived from Lower Cretaceous volcanic rocks and pre-Cretaceous strata in the northern Lhasa subterrane. During Late Cretaceous time, two thrust systems with opposite vergence were responsible for transforming the northern Lhasa subterrane into an elevated mountain range. This process resulted in the evolution from a shallow marine environment (Langshan Formation) into a terrestrial depositional environment (Daxiong Formation) on the southern margin of the northern Lhasa subterrane. Given the regional paleogeographic context, we conclude that the Daxiong Formation in the Coqen Basin records local crustal shortening and flexure resulting in foreland basin development on the southern margin of the northern Lhasa subterrane, which implies early topographic growth of the northern Lhasa subterrane in southern Tibet prior to the India-Asia collision. [ABSTRACT FROM AUTHOR]

Using the seismic profiles and analog modeling, this paper addresses the salt structures in the M and B blocks in the Southern Precaspian Basin. The salt structural features, the formation mechanism and the controlling factors of structural deformation are investigated and discussed systematically. The interpretation of the seismic profiles shows that typical salt-related structures include salt wall, (flip-flop) salt diapir, salt roller, salt pillow (dome), salt weld, salt withdrawal minibasin and drag structure (or drape fold). In addition, model results demonstrate that the gravity spreading driven by progradation and aggradation is probably the primary factor in controlling the formation of the salt structures in the research area. Due to the differential loading driven by progradation, passive salt diapir developed near the progradational front followed by the formation of intrasalt withdrawal minibasin bounded by two salt diapirs, and secondary reactive triangle salt diapir or salt pillow might form within the intrasalt withdrawal minibasin. Model results also indicate that the pattern of the subsalt basement has important influence on the formation and evolution of salt structures. Salt diapirs primarily developed along the margin of the subsalt uplift basement, where high shear deformation was induced by differential sedimentary loading between the uplift area and the slope area. [ABSTRACT FROM AUTHOR]

Up to 10% of the liquid hydrocarbons of the Golfo San Jorge basin come from the Mina del Carmen Formation (Albian), an ash-dominated fluvial succession preserved in a variably integrated channel network that evolved coeval to an extensional tectonic event, poorly analyzed up to date. Fault orientation, throw distribution and kinematics of fault populations affecting the Mina del Carmen Formation were investigated using a 3D seismic dataset in the Cerro Dragón field (Eastern Sector of the Golfo San Jorge basin). Thickness maps of the seismic sub-units that integrate the Mina del Carmen Formation, named MEC-A–MEC-C in ascending order, and mapping of fluvial channels performed applying geophysical tools of visualization were integrated to the kinematical analysis of 20 main normal faults of the field. The study provides examples of changes in fault throw patterns with time, associated with faults of different orientations. The “main synrift phase” is characterized by NE–SW striking (mean Az = 49°), basement-involved normal faults that attains its maximum throw on top of the volcanic basement; this set of faults was active during deposition of the Las Heras Group and Pozo D-129 formation. A “second synrift phase” is recognized by E–W striking normal faults (mean Az = 91°) that nucleated and propagated from the Albian Mina del Carmen Formation. Fault activity was localized during deposition of the MEC-A sub-unit, but generalized during deposition of MEC-B sub-unit, producing centripetal and partially isolated depocenters. Upward decreasing in fault activity is inferred by more gradual thickness variation of MEC-C and the overlying Lower Member of Bajo Barreal Formation, evidencing passive infilling of relief associated to fault boundaries, and conformation of wider depocenters with well integrated networks of channels of larger dimensions but random orientation. Lately, the Mina del Carmen Formation was affected by the downward propagation of E–W to ESE–WNW striking normal faults (mean Az = 98°) formed during the “third rifting phase”, which occurs coeval with the deposition of the Upper Member of the Bajo Barreal Formation. The fault characteristics indicate a counterclockwise rotation of the stress field during the deposition of the Chubut Group of the Golfo San Jorge basin, likely associated to the rotation of Southern South America during the fragmentation of the Gondwana paleocontinent. Understanding the evolution of fault-controlled topography in continental basins allow to infer location and orientation of coeval fluvial systems, providing a more reliable scenario for location of producing oil wells. [ABSTRACT FROM AUTHOR]

The Žacléř coalfield in the western part of the Intra-Sudetic Basin is an example of coal accumulation in an alluvial valley deposited under a long-term (~3m.y.) stable tectonic regime, with climatic oscillations possibly operating on several time scales. The resulting sedimentary record, about 600m thick, encompasses about 60 coal-bearing cycles formed in a relatively small and localized part of the valley, whereas elsewhere a higher clastic input and/or lower rate of subsidence resulted in deposition of strata with very little coal. Available data suggest that tectonics produced accommodation for sediments and, via changes in topography and/or size of the source area, affected the volume and dispersal patterns of clastic material transported to the depocentre. Areas with long-term tectonic stability were suitable places for recognition of climatic signals in the sedimentary record, modified by the intensity of local clastic input. Climatic fluctuations generated coal-bearing cycles, probably through a variable intensity of precipitation which affected the density of vegetation cover across the landscape along with evaporation and groundwater table. These factors influenced the intensity of chemical weathering and hence regulated the volume and composition of clastics delivered to the depocentre. This in turn resulted in alternation of short periods of bedload-dominated deposition during the seasonally dry part of the cycle with periods of dominantly suspended load and organic (peat) deposition during the more humid (?everwet) part of the cycle. Estimated duration of the basic cycles (~46k.y.) approximates the orbitally-driven axial tilt cyclicity. Basic cycles are arranged into two larger-scale cyclic patterns lasting for 270k.y. and 1.5m.y., respectively, which broadly correspond with the timing of glacial maxima and minima inferred from high-latitude glacial deposits of Gondwanan basins. All the coals of the Žacléř coalfield display similar petrographic composition dominated by collotelinite, and field observations as well as detailed petrographic study show that they formed in planar rheotrophic peat swamps where long-lasting peat accretion was episodically interrupted only by major floods on a century to millennial scale. [ABSTRACT FROM AUTHOR]

The tectonics of the Virgin Islands Basin are controlled by the plate boundary between the Puerto Rico-Virgin Islands Microplate and the stable part of the Caribbean Plate. Several contradicting theories about the formation and development of this basin have previously been proposed. As part of the Danish Galathea 3 expedition, extensive marine geological investigations of the basin were carried out in March 2007 including sediment coring and acquisition of multi-beam and two-dimensional seismic data. This paper represents a summary of the key observations from the multi-beam and the seismic data set. The interpretation of these observations leads to the proposition of a tectonic model for the Virgin Islands Basin. The model consists of N-S to NW- SE directed extension combined with E-W trending sinistral strike-slip and the new structural evidence from the Virgin Islands Basin is entirely consistent with the most recently published GPS data. [ABSTRACT FROM AUTHOR]

Abstract: The stratigraphy, sedimentology and syn-depositional tectonic events (SdTEs) of the Upper Cretaceous/Paleogene (K–P) succession at four localities in north Eastern Desert (NED) of Egypt have been studied. These localities are distributed from south-southwest to north-northeast at Gebel Millaha, at North Wadi Qena, at Wadi El Dakhal, and at Saint Paul Monastery. Lithostratigraphically, four rock units have been recorded: Sudr Formation (Campanian–Maastrichtian); Dakhla Formation (Danian–Selandian); Tarawan Formation (Selandian–Thanetian) and Esna Formation (Thanetian–Ypresian). These rock units are not completely represented all over the study area because some of them are absent at certain sites and others have variable thicknesses. Biostratigrapgically, 18 planktonic foraminiferal zones have been recorded. These are in stratigraphic order: Globotruncana ventricosa Zone (Campanian); Gansserina gansseri, Contusotruncana contusa, Recimguembelina fructicosa, Pseudohastigerina hariaensis, Pseudohastigerina palpebra and Plummerita hantkenenoides zones (Maastrichtian); Praemurica incostans, Praemurica uncinata, Morozovella angulata and Praemurica carinata/Igorina albeari zones (Danian); Igorina albeari, Globanomanlina pseudomenradii/Parasubbotina variospira, Acarinina subsphaerica, Acarinina soldadoensis/Globanomanlina pseudomenardii and Morozovella velascoensis zones (Selandian/Thantian); and Acarinina sibaiyaensis, Pseudohastigerina wilcoxensis/Morozovella velascoensis zones (earliest Ypresian). Sedimentologically, four sedimentary facies belts forming southwest gently-dipping slope to basin transect have been detected. They include tidal flats, outer shelf, slumped continental slope and open marine hemipelagic facies. This transect can be subdivided into a stable basin plain plus outer shelf in the extreme southwestern parts; and an unstable slope shelf platform in the northeastern parts. The unstable slope shelf platform is characterized by open marine hemipelagic, fine-grained limestones and fine siliciclastic shales (Sudr, Dakhla, Tarawan and Esna formations). The northeastern parts are marked by little contents of planktonic foraminifera and dolomitized, slumped carbonates, intercalated with basinal facies. Tectonically, four remarkable syn-depositional tectonic events (SdTEs) controlled the evolution of the studied succession. These events took place strongly within the Campanian–Ypresian time interval and were still active till Late Eocene. These events took place at: the Santonian/Campanian (S/C) boundary; the Campanian/Maastrichtian (C/M) boundary; the Cretaceous/Paleogene (K/P) boundary; and the Middle Paleocene–Early Eocene interval. These tectonic events are four pronounced phases in the tectonic history of the Syrian Arc System (SAS), the collision of the Afro-Arabian and Eurasian plates as well as the closure of the Tethys Sea. [Copyright &y& Elsevier]

Abstract: The key to understanding the fluvial response to climate change and surface uplift is a thorough distinguishing between their roles in terrace formation. Previous studies have tended to attribute the fluvial behavior of deposit–incision alternation to climate cyclicity. A preliminary explanation is proposed here for terrace formation in the eastern part of the Fenwei Basin, China. The observed fluvial terrace sequence was developed by the Yellow River deeply downcutting into the Emei Platform, which was uplifted within the eastern Fenwei Basin, and therefore it probably records the tectonic history of this platform. On the basis of the magnetostratigraphy and optically stimulated luminescence (OSL) dating, a ca. 1.2Ma chronology was established for this terrace sequence. Pedostratigraphic analysis of the loess deposits accumulated on each tread reveals that the terrace deposits are overlain immediately by a paleosol bed, suggesting that the abandonment of these terraces due to fluvial incision occurred at the transitions from glacial to interglacial climates. The glacial–interglacial climate cycle probably has a temporal control on the fluvial behavior of deposit–incision alternation, even though the Yellow River develops in the subsiding Fenwei Basin. The terrace generation may be sporadic and in the form of unusual stacked pattern before the Emei Platform was uplifted within the eastern Fenwei Basin. The terrace staircases however, formed in synchrony with glacial–interglacial climate cycles since this platform began to uplift in the late Middle Pleistocene. This result indicates that uplift may be necessary in large terrace staircase genesis. It can force the river system to downcut deeply enough during climatic transitions to separate terrace levels adequately, favoring the generation and subsequent preservation of the terrace treads. The terrace sequence of the Yellow River in the eastern Fenwei Basin therefore can be considered as a combined archive of climate change and local tectonic activity. [Copyright &y& Elsevier]

Abstract: The Qinghai-Tibet Plateau, composed of several continental slivers within the eastern Tethyan domain, is one of the pivotal sites to examine to better understand the theory of plate tectonics and the orogenic evolution on Earth. This plateau is generally inferred to be a collage of several continental blocks that rifted from Gondwanaland and subsequently accreted to the Asian continent. However, recent recognition of over twenty ophiolite mélange zones and their associated island arcs indicates that the traditional model of tectonic evolution requires revision. Based on 177 recently finished 1:250,000 scale geological maps and related studies, we summarize the main tectonic context of the Qinghai-Tibet Plateau and propose a new integrated model to account for the new findings. The complex orogen of the immense Qinghai-Tibet Plateau, consisting of multiple island arc-basin systems that developed at different stages while surrounded by the North China, Yangtze, Tarim, and Indian plates, is emphasized. The entire orogen, surrounded by suture zones that mark the locations of oceanic closure, is investigated by examining (I) the first-order tectonic units and ophiolitic mélanges (including arc–arc/continent collision zones) and (II) their internally enclosed blocks as the second-order tectonic units. Therefore, the Qinghai-Tibet Plateau is divided into three major orogenic systems, namely, from northeast to southwest, the Early Paleozoic Qinling–Qilianshan–Kunlunshan (Qin–Qi–Kun), the Late Paleozoic–Triassic Qiangtang–Sanjiang, and the Late Paleozoic to Cenozoic Gangdese–Himalaya orogenic systems, which are separated by the Kangxiwa–Muzitagh–Maqin–Mianxian and the Bangong–Shuanghu–Changning–Menglian sutures, respectively. We propose that the formation and evolution of the Qinghai-Tibet Plateau to have been intrinsically related to those of the eastern Tethys, recorded by the Longmu Co-Shuanghu ophiolite mélange zone, the Southern Qiangtang Paleozoic accretionary arc-basin system, the Bangong–Nujiang suture zone, and their associated, composite island arc-basin systems. The present-day Bangong–Shuanghu–Changning–Menglian suture system marks the final closure of the Tethyan Ocean. The Yarlung Zangbo Ocean opened as a back-arc basin in response to the southward subduction of the Tethyan Ocean lithosphere in the Middle Triassic and closed as a result of the India–Asia collision at the end of Cretaceous, followed by the northward indention of the Indian plate that resulted in significant intra-continental deformation and plateau uplift in the Cenozoic. [Copyright &y& Elsevier]

Abstract: The present study reports a sedimentological analysis of the Guara Limestone Formation deposited during the Lutetian in the Sierras Exteriores, in the South-Pyrenean foreland basin. We provide a detailed facies analysis of the carbonates to precise the paleoenvironmental context during their deposition. We show that those limestones are mainly composed of shallow-water foraminifers and were deposited in relative shallow-water environments (<120m) during the whole Lutetian (SBZ 13 to SBZ 16). The Guara Limestone Formation represents the last occurrence of carbonate platform in the South-Pyrenean foreland basin and disappeared definitely at the Lutetian to Bartonian transition. The demise of carbonate producers at the end of the Lutetian could be related to an increase of continental erosion, due to tectonic and/or climatic forcing. We illustrate that in the Jaca basin, this event correlates with a marked increase in subsidence rate. However, this deformation event is local and the carbonate systems in the Pyrenean foreland resisted to many deformation events during the whole basin history before. Paleobathymetric reconstructions in the Jaca basin, where shallow marine sections outcrop, suggest an increase of the amplitude of high-frequency sea-level cycles. This increase is contemporaneous with several climatic evidences, which suggest the appearance of early ice-sheets near the Lutetian–Bartonian boundary. The demise of carbonate producers seems, therefore, to be the result of a major environmental shift in the basin accompanying increased subsidence rates, switching from low nutrient oligotrophic conditions – favourable for shallow water benthic foraminifers – to eutrophic conditions due to the increase of erosion and terrigenous nutrient input associated with higher-frequency sea-level changes and river destabilization. [Copyright &y& Elsevier]

Abstract: The origin of Pantheon Fossae, a complex structure consisting of radial graben in the center of the Caloris basin, Mercury, has been debated since the structure was first imaged by the MESSENGER spacecraft. Three different formation hypotheses have been suggested, i.e. an origin associated with the Apollodorus impact into a previously domed Caloris basin floor, graben formation as surface expressions of dike intrusions and basin-interior uplift alone. In order to test the scenarios, detailed observations from the currently available imagery were compared to the proposed formation mechanisms. We evaluate these origin hypotheses by means of detailed interpretations of the graben characteristics and patterns, by comparing to radial structures from Earth and Venus, and by mechanical analyses for each formation hypothesis. Results indicate that the formation of Pantheon Fossae as the result of doming in the central part of the Caloris basin is more likely than it having formed in association with a radially symmetric stress field centered at or near the Apollodorus crater, that would have been created by a magma chamber or been superimposed on a pre-existing dome due to impact mechanics. [ABSTRACT FROM AUTHOR]

Late Cretaceous emplacement of ophiolitic-radiolaritic thrust sheets over the Arabian passive margin was the first manifestation of the protracted closure of the Neotethys Ocean, which ended with the continental collision between Arabia and central Iran and the formation of the present Zagros fold belt. This tectonic stacking produced a flexural basin (the Amiran Basin: 400 x 200 km in size) in the northwest Zagros that was filled with a 1225-m-thick shallowing-upward detrital succession made up of the Amiran, Taleh Zang, and Kashkan Formations. This succession sits unconformably above the Late Cretaceous Gurpi Formation and is overlain by the Oligocene-Miocene Shahbazan-Asmari carbonate succession. Dating of the Amiran-Kashkan succession is based on detailed biostratigraphy using large foraminifera and calcareous nannoplankton. The Cretaceous-Tertiary (K-T) boundary is located within the uppermost 25-45 m of the Gurpi Formation. The overlying Amiran and Taleh Zang Formations have been dated as Paleocene in age. However, the base of the Paleocene within the Gurpi Formation lacks NP1 and NP2 zones, implying a hiatus of ~2 m.y. at ca. 65.5 Ma, which is inferred to correspond to an early folding phase near the Cretaceous-Paleocene boundary. The upper part of the Kashkan Formation is dated to the earliest Eocene by palynostratigraphy. A large hiatus (or very slow deposition) lasting about 15 m.y. occurs between the Kashkan and Shahbazan Formations in the studied region. The base of the prograding Shahbazan platform deposits is dated by 87Sr/86Sr stratigraphy at ca. 33.9 Ma. The upper part of the Asmari Formation is dated as early-middle Miocene using foraminifera associations. Reconstruction of the Amiran-Taleh Zang-Kashkan succession of the Amiran Basin indicates a thickening of the basin fill from the southern pinch-out along the SE flank of the Kabir Kuh anticline to SW of the Khorramabad anticline, where the flexure is at least 900 m. In contrast, the NE part of the basin underwent coeval contraction and uplift of ~1300 m. Superimposed smaller undulations onto the large-scale flexure are interpreted as Late Cretaceous-Paleocene folds. Regional comparisons (SE Zagros, Oman, and Turkey) indicate that Late Cretaceous--Early Tertiary deformation affected the entire NE margin of Arabia but that compression was not synchronous, being younger in Lurestan than in the NW Persian Gulf where inversion tectonics occurred from Turonian to mid-Campanian times. The long sedimentary hiatus spanning most of the middle and late Eocene must have been related to deep lithospheric processes linked to the initial events of the protracted closure of the Neotethys Ocean between Arabia and central Iran. The tectono-sedimentary history recorded in the Zagros Basin may help to understand early foreland basin growth in other orogens in which subsequent continental collision has obliterated these early events. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a stratigraphic, petrographic and sedimentologic analysis of felsic syn-eruptive deposits of the southernmost Permian basin in Europe (Viar Basin), an inner-orogenic, transtensional half-graben located between two major geotectonic zones of the Iberian Variscan Belt, SW Spain. The syn-eruptive deposits of the Viar Basin represent a mappable lithostratigraphic unit, that is herein named the Los Canchales Formation. This unit forms a wedge-shaped body bounded by alluvial–fluvial deposits (red layers) that are in gradational contact. The stratigraphic architecture of the Los Canchales Formation is complex with frequent facies changes and interfingering among pyroclastic rocks, resedimented–volcaniclastic rocks and sedimentary rocks. Abundant fossil flora is also recorded. A wax–wane cycle of volcanic activity is recognized during the syn-eruptive period. Two short-lived volcanic episodes were recorded including ignimbrites and a possible phreatomagmatic event. Explosive volcanism generated pyroclastic flow, surge and ash-fall deposits, in cases collapsing the drainage network. They also modified the vegetation and created a new depositional setting with four successive sedimentary environments: vegetated floodplain, ephemeral sandy braidplain, palustrine environment and again vegetated floodplain. Input of pyroclasts followed a NW to SE longitudinal–axial dispersal pattern. [Copyright &y& Elsevier]

Abstract: The western half of the Ordos Basin lies in the north of Central China, on the western margin of the North Chinese Platform. In the southwest and south it borders the Qilian and Qinling folded systems. Their frontal northeastern flank is thrust over the Paleozoic nappe of the Ordos Basin and consists of a series of large parallel linear folds separated by thrusts. The basement of the basin is made up of deformed metamorphic rocks of tentatively Late Proterozoic age. Carbonate and terrigenous intracratonic facies accumulated on the Ordos block from Early Cambrian through Middle Ordovician. From Middle Ordovician through Middle Carboniferous, the western edge of the block was uplifted as a land as a result of Caledonian tectonic movement and underwent denudation for about 150 Myr. In the Late Paleozoic, a series of coal-bearing formations was deposited. In the Triassic, the Ordos Basin became filled with fluviolacustrine delta facies. Thrusts and folds on the southwestern margin of the basin formed in the Mesozoic and were intensified by Himalayan tectonic movements. [Copyright &y& Elsevier]

Subaerial exposure beside the Wandandian Creek channel during the last glacial maximum led to the development of red and orange mottling and, in some areas, produced a palaeosol over the Pleistocene land surface. Incision of the palaeo-Wandandian Creek, during the Late Pleistocene, formed a relatively deep steep-sided channel partially infilled with medium-grained fluvial sand. This palaeovalley became drowned as the post-glacial marine transgression impounded the western portion of St Georges Basin and the basal prodelta/lagoonal mud facies was deposited from ca 7 ka. The Wandandian Creek delta prograded down the palaeovalley and reached the study area &nvsim;3500 – 4000 years ago with the deposition of delta-front sandy silt and the overlying prograded sand facies. The subaerial portion of the delta is characterised by well-developed floodplains, levees, mouth bars and backswamps. Dredging in Wandandian Creek and land clearing for rural and urban development have had little long-term effect on the growth and morphology of Wandandian Creek delta. [ABSTRACT FROM AUTHOR]

Geodynamic modelling indicates that the emergence of initially submarine convergent orogens above sea level can have a significant influence on their subsequent tectonic development. This is because of two effects. First, surface uplift under submarine conditions, and the resulting decrease in gravitational loads, tends to reactivate deformation in the uplifting part of the submerged orogen. Second, an increase in the rate of erosion associated with the emergence of land can cause increased exhumation rates, reduced thrust-front advance rates, narrowing of the orogen width, and a shift from slow deposition in piggyback basins to rapid deposition in the foredeep. These effects result from the ability of erosion to perturb mass balance at the orogen-scale. Based on these results, I hypothesize that the emergence of initially submerged orogens such as the Alps and Taiwan played a direct role in explaining major changes in orogen dynamics and basin evolution that are known to occur in these examples. [ABSTRACT FROM AUTHOR]

Several basins are developing near bends on strands of the North Anatolian transform fault in northwest Turkey. Oblique slip on these faults, rather than strain partitioning, accounts for trans-tension and subsidence. These basins are asymmetric, and tilt and subside most rapidly at their narrow ends near the bends. The turbidite surface marking the floor of the Cinarcik Basin (eastern Marmara Sea) was mostly abandoned at a sudden drop in sedimentation, which was likely coincident with the 14 ka lake-sea transition, and is now a warped reference surface from which we can measure strain and sedimentation. Subsidence and tilt are rapid, but do not require late Quaternary changes in regime. They are linked to transcurrent motion by slip parallel to an oblique bend on the North Anatolian fault and suggest tsunamogenic vertical motion in large Marmara Sea earthquakes. [ABSTRACT FROM AUTHOR]

Facies, shell bed features, and sequence stratigraphic framework for the shallow-marine Pleistocene upper Canoa and Tablazo Formations are presented, based on outcrop data from the southern coast of Cabo San Lorenzo, Ecuador. Sediments of this succession exhibit a distinct cyclic pattern, consisting of a stack of eight depositional sequences (cyclothems) likely developed under the main control of orbitally induced sea-level changes. As a rule, within the studied interval an idealized cyclothem is composed of a transgressive systems tract (TST) and a highstand systems tract (HST), whereas deposits attributable to the lowstand and Jailing-stage systems tracts are not present. Transgressive lithosomes may be defined by estuarine deposits interposed between the sequence boundary and the ravinement surface (back-barrier wedge) and by upward fining shoreface to inner-shelf facies successions above the ravinement (backstepping shelf wedge). Separated by an expanded siliciclastic core, hiatal shell concentrations occur at the base (onlap shell beds) and the top (backlap shell beds) of the transgressive shelf wedges, and some occur at the base of highstand systems tracts (down-lap shell beds). On the basis of sedimentary facies, geometry, taphonomy, and paleoecology of shell beds, and the nature of the transition between siliciclastic and mollusk-bearing sediments, cyclothems were classified into two main types that show dependence upon paleoshoreline morphological configuration: sheltered (in the upper Canoa Formation) and exposed (in the Tablazo Formation). Notwithstanding the different synsedimentary tectonic and climatic regimes, the Ecuadorian cyclothems share basic patterns of condensation and facies assemblages with other roughly coeval cyclothemic successions around the world. This suggests that (1) hiatal shell bed development is not just a temperate-latitude phenomenon; (2) a global process, such as glacio-eustatic sea-level change, is the primary mechanism of control for the general architecture of sequences; and (3) specific paleogeographic settings play an important role by determining the taphonomic and paleoecologic characteristics of key shell beds, the nature of their contacts with the encasing sediments, and the type of the component set of facies. At a multicycle time scale, tectonics influenced the long-term trend of the relative sea-level changes and consequently the large-scale stratigraphic organization. Owing to the continued tectonic uplift of the area, successive high-frequency depositional sequences are nested to form a longer-order falling-stage sequence set. [ABSTRACT FROM AUTHOR]

This article comments on an research paper regarding basin development during deposition of the Elliot Formations and the Karoo Supergroup in South Africa, published in the 2004 issue of "South African Journal of Geology." The article asserts that the recognition and precise stratigraphic position of the unconformities proposed in the upper Karoo succession is based on correlations with the Ar-Ar system dated orogenic pulses in the Cape Fold Belt. It refutes the claim that the upper Elliott Formation contains no planar cross-bedding and recognizes the influence of basin tectonics on upper Karoo sedimentation during Elliott formation times.

Arising from: D. B. Rowley & B. S. Currie 439, 677–681 (2006); Rowley & Currie replyThe determination of palaeo-elevation has emerged in the past 15 years as an important tool for constraining physical processes that govern the formation of mountain belts. Rowley and Currie report palaeo-elevations for the Lunpola basin within the Tibetan plateau and claim that these elevations are incompatible with 'mantle-thickening models' for mountain formation. We show here that their data do not support this conclusion and, indeed, are consistent with its opposite. The Tibetan plateau could have risen by a kilometre or more as its dense lower lithosphere sank into the underlying mantle. [ABSTRACT FROM AUTHOR]