The “Camporeale wedge-top Basin” (NW Sicily; Italy) in the frame of the Late Miocene Sicilian Foreland Basin System; Inferences from the Upper Tortonian–Lower Messinian Terravecchia Formation

Since the latest Oligocene–earliest Miocene the building of the Sicilian fold and thrust belt has been accompanied by development of a “peripheral” foreland basin system which migrated toward the foreland. In north-western Sicily, the sedimentary record of the foreland basin system migration is represented by a stratigraphic succession made up of several lithostratigraphic units, bounded by regional unconformity surfaces, deposited recording at least four main sedimentary phases, each characterized by the development of different types of syntectonic basins.     

藏南定日地区上三叠统-古近系构造沉降分析与沉积盆地特征

构造沉降史研究是沉积盆地分析的一项重要内容。本文对藏南定日地区上三叠统-古近系进行了构造沉降史分析。研究表明:特提斯喜马拉雅定日地区晚三叠世-古近纪经历了由被动大陆边缘盆地沉降向周缘前陆盆地沉降的转换过程,根据构造沉降曲线特征,可划分为五个阶段。第Ⅰ-Ⅲ阶段即晚三叠世-晚白垩早期为被动大陆边缘沉降阶段,构造沉降曲线总体比较缓,沉降速率整体呈指数衰减,反映被动大陆边缘稳定的构造沉降过程。第Ⅳ阶段晚白垩晚期-古新世早期为构造隆升,古新世晚期再次为稳定构造沉降。对于晚白垩晚期-古新世早期的隆升有两种可能的解释,即德干地幔柱上涌引起的隆升或大陆碰撞板块挠曲引起的隆升。第V阶段始新世时期为印度-亚洲大陆碰撞形成的周缘前陆盆地沉降期,构造沉降曲线斜率增大,沉降速率增加,反映了该时期前陆盆地前渊区快速的沉降特征。     

The flexural margin,the foredeep,and the orogenic margin of a northern Cordilleran foreland basin: Cretaceous tectonostratigraphy and detrital zircon provenance,northwestern Canada

Reconstructions of the Albian to Campanian foreland basin adjacent to the northern Canadian Cordillera are based on outcrop and well log correlations, seismic interpretation, and reconnaissance-level detrital zircon analysis. The succession is subdivided into two tectonostratigraphic units. First is an Albian tectonostratigraphic unit that was deposited on the flexural margin of a foreland basin. At the base is a shallow marine sandstone interval that was deposited during transgressive reworking of sediment from cratonic sources east of the basin that resulted in a dominant 2000–1800 Ma detrital zircon age fraction. Subsequent deposition in a west-facing muddy ramp setting was followed by east-to-west shoreface progradation into the basin.Near the Albian–Cenomanian boundary, regional uplift and exhumation resulted in an angular unconformity at the base of the Cenomanian–Campanian tectonostratigraphic unit. Renewed subsidence in the Cenomanian resulted in deposition of organic-rich, radioactive, black mudstone of the Slater River Formation in a foredeep setting. Cenomanian–Turonian time saw west-to-east progradation of a shoreface-shelf system from the orogenic margin of the foreland basin over the foredeep deposits. Detrital zircon age peaks of approximately 1300 Ma, 1000 Ma, and 400 Ma from a Turonian sample are consistent with recycling of Mississippian and older strata from the Cordillera west of the study area, and show that the orogen-attached depositional system delivered sediment from the orogen to the foreland basin. A near syndepositional detrital zircon age of ca. 93 Ma overlaps with known granitoid ages from the Cordillera. After the shelf system prograded across the study area, subsequent pulses of subsidence and uplift resulted in dramatic thickness variations across an older structural belt, the Keele Tectonic Zone, from the Turonian to the Campanian.The succession of depositional systems in the study area from flexural margin to foredeep to orogenic margin is attributed to coupled foreland propagation of the front of the Cordilleran orogen and the foreland basin. Propagation of crustal thickening and deformation toward the foreland is a typical feature of orogens and so the distal to proximal evolution of the foreland basin should also be considered as typical.     

Stratigraphic and provenance evolution of the Southern Apennines foreland basin system during the Middle Miocene to Pliocene (Irpinia-Sannio successions,Italy)

The paper deals with original stratigraphic, petrographic and structural data concerning the evolution of the southern Apennines chain (Italy). The main Langhian to Pliocene deposits cropping out in the northern sector of the southern Apennines foreland basin system (Sannio-Irpinia area) have been studied and correlated in order to document the effects of tectonic changes on the evolution of sandstone detrital modes and stratigraphic architecture. The studied sandstone units can be grouped in five key intervals: a) Numidian Flysch, mostly formed by Langhian mature quartzarenitic deposits and conformable Serravallian post-Numidian successions, formed by arkosic and calciclastic arenaceous-pelitic beds (foreland depozones); b) Langhian to Tortonian San Giorgio Fm., mostly composed of quartzofeldspatic sandstones (foredeep depozone); c) Tortonian to Early Messinian, quartz-feldspatic and partly sedimentary-carbonatoclastic petrofacies, thrust-top successions (Vallone Ponticello, Villanova del Battista and San Bartolomeo fms.); d) Late Messinian quartzolithic to quartzofeldspatic sandstones (Torrente Fiumarella, Anzano Molasse and Tufo-Altavilla unit), which can be referred to infilled thrust-top basins; e) unconformity-bounded Pliocene quartzofeldspatic sandstone strata (wedge-top depozones), characterized by synsedimentary tectonic activity.Detrital modes of the Serravallian through Middle Pliocene sandstones of the southern Apennines foreland basin system testify clear provenance relations from the accreted terranes forming the southern Apennine thrust-belt. The studied clastics show almost the same blended (quartz-feldspatic) composition; this condition could be related to the tectonic transport over thrust ramp of source rocks, as suggested by the tectonic evolutionary model. This study, dealing with sedimentary provenance analysis and tectonostratigraphic evolution, provides an example of the close relations between clastic compositions and foreland basin system development in southern Apennines.     

早期碰撞造山带的构造样式及其板块构造演化意义：以华北克拉通五台山花岗岩—绿岩区为例

早期碰撞造山带的研究是探索板块构造早期体制的前缘领域。五台山地貌高差巨大（达2437m）、山体雄伟、地质露头连续完整,是我国早前寒武纪地质研究的经典地区和认识大陆克拉通早期地壳演化的窗口,已成为世界早前寒武纪碰撞造山带的典型实例。围绕五台山构造样式的深入研究,对于揭示早期板块构造演化及中浅地壳构造层次具有重要的地质意义。 大量的野外地质调查及构造横剖面研究表明,五台山东冶亚群为华北克拉通的早期沉积盖层,它以开阔复式向形为特征,不整合于造山杂岩及其前陆冲断带和前陆盆地之上。区域变质相的分布及豆村亚群主期褶皱枢纽指示,五台山花岗岩—绿岩区向西南掀斜,出露了新太古代碰撞造山带不同构造单元（造山杂岩及前陆冲断带和前陆盆地）中浅层次上连续而完整的构造剖面。前陆冲断带以沉积岩系大规模平卧褶皱和逆断层、蛇绿岩混杂带和基底构造活化为特征。造山杂岩发育低角度逆断层和复杂叠加褶皱,伴随不同时期花岗岩类的侵位。从浅部层次向深部,绿岩带复式褶皱逐渐被与TTG杂岩构造叠置的表壳岩构造岩片取代,构造面理由陡立趋于平缓。与世界其他花岗岩—绿岩区相比,五台山区完好保留了造山带挤压构造及其前陆盆地沉积,指示早期碰撞造山过程的强烈构造缩短和大规模地壳隆升作用,是研究早期板块碰撞造山过程的重要例证。     

Tectonic control on deltaic sediment dispersal in the middle to upper Turonian Western Cordilleran Foreland Basin,USA

Tectonic forcing of delta progradation is increasingly being invoked to explain stratal stacking patterns in foreland basins. Nonetheless, the recognition of different types of tectonic forcing and their consequences for the spatial and temporal distribution of accommodation often rely on incomplete data sets and indirect sequence stratigraphic criteria. Previous work has concluded that the Cenomanian–Turonian Frontier Formation of northern Utah, north‐west Colorado and south‐west Wyoming (‘Vernal Delta’) owes its origin largely to tectonic overprinting of depositional patterns, although the lack of a comprehensive sequence stratigraphic framework for the unit has hampered evaluation of this claim. This study provides detailed facies and sequence stratigraphic analyses based on outcrop sections and wireline log suites from the Uinta, Piceance and Green River basins. Four genetically related intervals were defined and mapped by using regionally traceable stratigraphic horizons (flooding surfaces and sequence boundaries). Internally, intervals are composed of distal and proximal delta front lithologies, and coastal plain facies. Overall, Intervals 1 to 4 form a major basinward projection of coarse clastic strata generated in response to four separate, high‐frequency regressions. Furthermore, a change through time from southward projection of elongate lobes (Intervals 1 and 2) to eastward dispersal and development of a broad, arcuate planform (Intervals 3 and 4) can be explained in terms of changes in prevailing tectonic forcing mechanisms. North–south trending Sevier Orogeny forebulge structures controlled Intervals 1 and 2. West–east progradation (Intervals 3 and 4) was probably controlled by Proterozoic basement lineament reactivation due to Laramide foreland uplifts. Therefore, this study provides direct geological evidence for the initiation of local Laramide deformation as early as 90 Ma. These findings contribute to a more complete understanding of tectonic forcing of coastal to shallow marine successions in foreland basins and the tectonic evolution of the western USA.     

Erratic shortening from balanced cross-sections of the western Himalayan foreland basin: causes and implications for basin evolution

Balanced cross-sections from the western Himalayan foreland foothill belt reveal a variation in shortening amounts from 22 to 71.3% over a lateral distance of 85 km. The large variation may be attributed to the fact that the method of cross-section balancing considers the initial layering as horizontal, which is an unlikely situation in foreland basins. Simple trigonometric relationships are used to minimize the error in shortening estimates. However, the suggested corrections could not be applied to the Himalayan foreland basin because of unavailability of the required data on initial basin geometry. The study also indicates that shortening rates for the area based on these shortening amounts cannot be used for earthquake prediction.     

Progression of deformation and sedimentation in the southernmost Andes

The chronology of thrust motion in the Fuegian thin-skinned fold-thrust belt was established using data from the Atlantic coast of Tierra del Fuego. A set of original structural–geological maps showing the distribution of structures, unconformities and synorogenic sequences in the last tip of the Andes reveals the cratonward propagation of thrusts and sedimentary depocenters. A succession of syntectonic angular and progressive unconformities occur in the studied zone: (1) an angular unconformity between Danian and Late Paleocene sequences, (2) a series of progressive and syntectonic angular unconformities developed from the Late Early Eocene to the Late Eocene, and (3) a Lower Miocene syntectonic unconformity. Additional evidence for the time–space location of the thrust-front is provided by the presence of seismically triggered sand intrusions in Late Cretaceous, Late Paleocene and Middle Miocene sequences.The integration of data shows that faulting occurred in three main episodes: San Vicente thrusting, ca. 61–55 Ma, Río Bueno thrusting, ca. 49–34, and Punta Gruesa strike-slip event, ca. 24–16 Ma. San Vicente thrusting represents the onset of thrust propagation onto the foreland craton. The thrust-front endured a major cratonward migration through the Río Bueno thrusting, and remained steady afterward. Punta Gruesa constitutes a strike-slip event, associated with the phase of wrench deformation that influences the southernmost Andes since the Oligocene. Although the overall pattern of faulting was progressively younger cratonward, several episodes of out-of-sequence thrusting and folding occurred.Other features in the southernmost Andes can be linked to these three deformation events to broadly characterize the behavior of the Fuegian orogenic wedge in terms of critical taper models. The Fuegian Andes underwent at least three cycles between subcritical, critical and supercritical stages of behavior in terms of deformation, erosion, and sedimentation.     

河西走廊东部晚古生代前陆盆地演化特征

河西走廊东部晚古生代前陆盆地从形成、稳定发展到收缩消亡的过程，反映了泥盆纪是主要成盆期，奠定了盆地的基本格架；石炭纪是盆地稳定发育阶段，也是盆地内煤、油气的主要形成期；自二叠纪至三叠纪，前陆盆地应变停止，应力粘弹性松驰，被重力作用下的山前盆地所取代。     

若尔盖-松潘前陆盆地的沉积与构造特点

若尔盖-松潘盆地中、上三叠统沉积剖面研究表明以陆相沉积为主,只在东北部青山峪有浅海相碳酸盐岩沉积。盆地北部出现河流、浅湖相沉积,中部以浅湖相沉积为主,局部出现深湖相沉积,南部主要为深湖相沉积。中、上三叠统地层的变形构造以冲褶席(duplex)构造为特点,表现出从北向南应变强度减弱。深部构造反映了盆地位于扬子板块大陆壳基底之上,叠覆在扬子板块北缘的前陆褶皱冲断带上。大地构造位置、沉积相与构造特点,共同说明若尔盖-松潘盆地是三叠纪碰撞造山作用时期扬子板块北部北缘的前陆盆地。