Late Cenozoic fluvial successions in northern and western India: an overview and synthesis

Late Cenozoic fluvial successions are widespread in India. They include the deposits of the Siwalik basin which represent the accumulations of the ancient river systems of the Himalayan foreland basin. Palaeomagnetic studies reveal that fluvial architecture and styles of deposition were controlled by Himalayan tectonics as well as by major climatic fluctuations during the long (∼13 Ma) span of formation. The Indo-Gangetic plains form the world's most extensive Quaternary alluvial plains, and display spatially variable controls on sedimentation: Himalayan tectonics in the frontal parts, climate in the middle reaches, and eustasy in the lower reaches close to the Ganga–Brahmaputra delta. Climatic effects were mediated by strong fluctuations in the SW Indian Monsoon, and Himalayan rivers occupy deep valleys in the western Ganga plains where stream power is high, cut in part during early Holocene monsoon intensification; the broad interfluves record the simultaneous aggradation of plains-fed rivers since ∼100 ka. The eastward increase in precipitation across the Ganga Plains results in rivers with low stream power and a very high sediment flux, resulting in an aggradational mode and little incision. The river deposits of semi-arid to arid western India form important archives of Quaternary climate change through their intercalation with the eolian deposits of the Thar Desert. Although the synthesis documents strong variability—both spatial and temporal—in fluvial stratigraphy, climatic events such as the decline in precipitation during the Last Glacial Maximum and monsoon intensification in the early Holocene have influenced fluvial dynamics throughout the region.     

冈底斯-喜马拉雅碰撞造山带前陆盆地系统及构造演化

碰撞带前陆盆地的建立是大陆碰撞的直接标志和随后造山带构造变形的忠实记录。本文对欧亚板块与印度板块碰撞前后发育在拉萨地块上的冈底斯弧背前陆盆地,同碰撞产生的雅鲁藏布江周缘前陆盆地,以及碰撞后陆内变形产生的喜马拉雅前陆盆地的沉积地层演化以及碎屑锆石物源特征等进行了系统分析,结合前人及我们近些年的研究成果,认为冈底斯岛弧北侧发育一个典型的弧背前陆盆地系统而不是以前普遍接受的伸展盆地。除传统认为的喜马拉雅前陆盆地系统外,在碰撞造山带中还发育一个雅鲁藏布江前陆盆地系统,它是欧亚板块与印度板块碰撞以后,欧亚板块加载到印度被动大陆边缘产生的典型周缘前陆盆地。上述2个造山带前陆盆地系统的识别,大大提高了对新特提斯洋俯冲、碰撞过程的认识。造山带前陆盆地证据指示,新特提斯洋至少于140 Ma以前就已开始俯冲, 110 Ma俯冲速度开始提高,在65 Ma前后印度大陆与欧亚大陆发生碰撞,喜马拉雅山于40 Ma开始隆升,其剥蚀物质大量堆积在喜马拉雅前陆盆地中。     

华南地区加里东期前陆盆地演化过程中的沉积响应

华南地区从震旦纪至早古生界经历了从洋盆的形成、直至转换成前陆盆地的过程。被动大陆边缘阶段，在扬子陆块的东南边缘构成了2次从碎屑岩陆架到碳酸盐台地的沉积序列，一次为震旦纪；另一次为寒武纪至早奥陶世。从中奥陶世至志留纪末，华南洋关闭、形成前陆盆地系统。它由前陆推覆体、前陆前渊、前陆隆起和隆后盆地4部分组成。前陆推覆体细分为根带、中带、前锋带。随着推覆体的上叠式的逆冲，形成外前渊盆地（钦防一带）和内前渊盆地（湘西、黔东南）。当前陆推覆体向克拉通推进时，前陆隆起也逐渐向后退。此带表现出一个海平面相对上升的过程，形成碳酸盐缓坡。随着推覆体进一步逆冲，前缘隆起继续隆升，且露出水面，使其后的隆后盆地转变为半局限环境。晚志留世末，前陆盆地回返，海水从东向西逐渐退出扬子大陆。     

Migration of the Ganga river and its implication on hydro-geological potential of Varanasi area, U.P., India

Borehole data reveals that during Late Quaternary, the Ganga river was non-existent in its present location near Varanasi. Instead, it was flowing further south towards peripheral craton. Himalayan derived grey micaceous sands were being carried by southward flowing rivers beyond the present day water divide of Ganga and mixed with pink arkosic sand brought by northward flowing peninsular rivers. Subsequently, the Ganga shifted to its present position and got incised. Near Varanasi, the Ganga river is flowing along a NW-SE tectonic lineament. The migration of Ganga river is believed to have been in response to basin expansion caused due to Himalayan tectonics during Middle Pleistocene times. Multi-storied sand bodies generated as a result of channel migration provide excellent aquifers confined by a thick zone of muddy sediments near the surface. Good quality potable water is available at various levels below about 70 m depth in sandy aquifers. Craton derived gravelly coarse-to-medium grained sand forms the main aquifer zones of tens of meter thickness with enormous yield. In contrast, the shallow aquifers made up of recycled interfluve silt and sandy silt occur under unconfined conditions and show water-level fluctuation of a few meters during pre-and post-monsoon periods.     

环青藏高原巨型盆山体系构造与塔里木盆地油气分布规律

中国中西部受控于喜山期青藏高原的隆升和向北、向东的推挤,在其外围形成一个巨型的盆山构造体系,环青藏高原巨型盆山体系主要由复活后的古造山带、前陆冲断带和小型克拉通盆地三个基本的构造单元组成,其中古生界小型克拉通与中新生界前陆冲断带是重要的含油气单元,它决定了中国中西部油气分布主要受古生界克拉通古隆起和中新生界前陆冲断带的控制。塔里木盆地在纵向上由发育齐全的下古生代碳酸盐岩、上古生代海相-海陆交互相碎屑岩沉积和中新生代陆相碎屑岩等构造层序叠置而成,在平面上以较稳定的小型克拉通为核心,边缘环绕库车、喀什、塔西南、塔东南等褶皱或冲断变形的前陆冲断带。塔里木盆地古生界小型克拉通盆地与中新生界前陆逆冲带叠合-复合的构造特征,以及演化的多阶段性,决定了这类盆地具有"多套烃源岩、多储盖组合、多含油气系统"的叠合-复合含油气系统的特点;油气分布受小型克拉通盆地中的古隆起控制,形成大面积岩性地层油气藏,前陆盆地中的冲断带构造控制形成背斜油气藏,具有多期成藏并存与晚期成藏为主的特点。     

中国喜马拉雅构造运动的陆内变形特征与油气矿藏富集

在前人研究的基础上,结合近年来在油气勘探中不断积累的地质资料和地质认识,提出了中国喜马拉雅构造运动的陆内变形特征及其分布规律受控于小型克拉通板块拼贴的基底结构和印/欧碰撞与太平洋板块俯冲所主导的双重控制因素;喜马拉雅构造运动的发育特征主要表现为三种动力学机制:青藏高原隆升、盆地与造山带体制和东部拉张活动。喜马拉雅构造运动的大地构造格局及其构造变形分布规律集中体现为4个构造域:青藏高原隆升区、环青藏高原盆山体系、稳定区和环西太平洋裂谷活动区。我国沉积盆地在喜马拉雅构造运动中的构造特征分为三种类型:(1)东部渤海湾、松辽等盆地受拉张构造环境控制的裂谷沉降;(2)中部四川、鄂尔多斯等盆地受青藏高原的向东推挤、盆缘冲断、盆内抬升剥蚀;(3)西部的塔里木、准噶尔、柴达木等盆地受青藏高原的向北推挤、冲断挠曲沉降,表现为克拉通单边或双边的压缩挠曲沉降与克拉通内部的冲断隆升沉降等多种盆山耦合形式。喜马拉雅构造运动控制着中国油气晚期定位与富集成藏,主要体现在:盆地的沉积与成藏,形成新生界自生自储的含油气盆地和油气藏;圈闭形成与油气运聚成藏;早期油气藏的调整和再分配;油气藏的破坏。     

Latest Miocene to Quaternary horizontal and vertical displacement rates during simultaneous contraction and extension in the Southern Apennines orogen, Italy

Foreland contraction and hinterland extension in the Southern Apennines orogen of Italy produced a complex spatial and temporal pattern of vertical and horizontal displacement. Remarkably, Late Miocene to mid-Pleistocene foreland migration of the contractional front at ∼16 mm yr⁻¹ was not accompanied by uplift and the frontal thrust belt remained at or below sea level. Only following a mid-Pleistocene reduction in horizontal displacement did the frontal thrust belt and foreland begin uplift at ∼0.5 mm yr⁻¹, a rate that increased to ∼1 mm yr⁻¹ after 125 ka. Although the extensional hinterland experienced net subsidence during formation of the Tyrrhenian basin, an extensional transition zone adjacent to the frontal thrust belt records sustained uplift at ∼0.3 mm yr⁻¹. The interaction of preexisting crustal structure and deep tectonic processes resulted in time-integrated displacement rates suggesting steady-state deformation for periods of 10⁶ years. Displacement rate changes were abrupt and occurred over intervals of 10⁵ years or less.     

Tectonic controls on the geomorphic evolution of alluvial fans in the Piedmont Zone of Ganga Plain,Uttarakhand, India

The Piedmont Zone is the least studied part of the Ganga Plain. The northern limit of the Piedmont Zone is defined by the Himalayan Frontal Thrust (HFT) along which the Himalaya is being thrust over the alluvium of the Ganga Plain. Interpretation of satellite imagery, Digital Terrain Models (DTMs) and field data has helped in the identification and mapping of various morphotectonic features in the densely forested and cultivated Piedmont Zone in the Kumaun region of the Uttarakhand state of India. The Piedmont Zone has formed as a result of coalescing alluvial fans, alluvial aprons and talus deposits. The fans have differential morphologies and aggradation processes within a common climatic zone and similar litho-tectonic setting of the catchment area. Morphotectonic analysis reveals that the fan morphologies and aggradation processes in the area are mainly controlled by the ongoing tectonic activities. Such activities along the HFT and transverse faults have controlled the accommodation space by causing differential subsidence of the basin, and aggradation processes by causing channel migration, channel incision and shifting of depocentres. The active tectonic movements have further modified the landscape of the area in the form of tilted alluvial fan, gravel ridges, terraces and uplifted gravels.     

Morphologic evolution of the Central Andes of Peru

In this paper, we analyze the morphology of the Andes of Peru and its evolution based on the geometry of river channels, their bedrock profiles, stream gradient indices and the relation between thrust faults and morphology. The rivers of the Pacific Basin incised Mesozoic sediments of the Marañon thrust belt, Cenozoic volcanics and the granitic rocks of the Coastal Batholith. They are mainly bedrock channels with convex upward shapes and show signs of active ongoing incision. The changes in lithology do not correlate with breaks in slope of the channels (or knick points) such that the high gradient indices (K) with values between 2,000–3,000 and higher than 3,000 suggest that incision is controlled by tectonic activity. Our analysis reveals that many of the ranges of the Western Cordillera were uplifted to the actual elevations where peaks reach to 6,000 m above sea level by thrusting along steeply dipping faults. We correlate this uplift with the Quechua Phase of Neogene age documented for the Subandean thrust belt. The rivers of the Amazonas Basin have steep slopes and high gradient indices of 2,000–3,000 and locally more than 3,000 in those segments where the rivers flow over the crystalline basement of the Eastern Cordillera affected by vertical faulting. Gradient indices decrease to 1,000–2,000 within the east-vergent thrust belt of the Subandean Zone. Here a correlation between breaks in river channel slopes and location of thrust faults can be established, suggesting that the young, Quechua Phase thrust faults of the Subandean thrust belt, which involve Neogene sediments, influenced the channel geometry. In the eastern lowlands, these rivers become meandering and flow parallel to anticlines that formed in the hanging wall of Quechua Phase thrust faults, suggesting that the river courses were actively displaced outward into the foreland.     

Structural characteristics and evolution of the South Yellow Sea Basin since Indosinian

Based on the seismic data gathered in past years and the correlation between the sea and land areas of the Lower Yangtze Platform, the structural characteristics of the South Yellow Sea Basin since the Indosinian tectonic movement is studied in this paper. Three stages of structural deformation can be distinguished in the South Yellow Sea Basin since the Indosinian. The first stage, Late Indosinian to Early Yanshanian, was dominated by foreland deformation including both the uplifting and subsidence stages under an intensively compressional environment. The second stage, which is called the Huangqiao Event in the middle Yanshanian, was a change for stress fields from compression to extension. While in the third stage (the Sanduo Event) in the Late Himalayan, the basin developed a depression in the Neogene-Quaternary after rifting in the Late Cretaceous-Paleogene. The long-time evolution controlled 3 basin formation stages from a foreland basin, then a fault basin to a final depression basin. In conclusion, since the Indosinian, the South Yellow Sea Basin has experienced compressional fold and thrust, collisional orogen, compressional and tensional pulsation, strike-slip, extensional fault block and inversion structures, compression and convergence. The NE, NEE, nearly EW and NW trending structures developed in the basin. From west to east, the structural trend changed from NEE to near EW to NW. While from north to south, they changed from NEE to near EW with a strong-weak-strong zoning sequence. Vertically, the marine and terrestrial facies basins show a “seesaw” pattern with fold and thrust in the early stages, which is strong in the north and weak in the south and an extensional fault in later stages, which is strong in the north and weak in the south. In the marine facies basin, thrust deformation is more prevailing in the upper structural layer than that in the lower layer. The tectonic mechanism in the South Yellow Sea Basin is mainly affected by the collision between the Yangtze and North China Block, while the stress environment of large-scale strike-slip faults was owing to subduction of the Paleo-Pacific plate. The southern part of the Laoshan uplift is a weak deformation zone as well as a stress release zone, and the Meso-Paleozoic had been weakly reformed in later stages. The southern part of the Laoshan uplift is believed, therefore, to be a promising area for oil and gas exploration.     

鸡西盆地构造特征及控煤构造分析

鸡西煤盆地位于三江-穆棱煤盆地群内,属断拗型盆地,煤盆地构造受区域构造格局和构造演化的控制,构造格局具有南北分带、东西分区的基本特征,结合地层沉积特征及含煤岩系展布特征分析,建立了赋煤构造单元划分方案;煤盆地可分为北部坳陷、恒山隆起、南部坳陷和敦密断裂带4个三级赋煤构造单元,北部坳陷和南部坳陷进一步划分出3个四级赋煤构造单元;区内控煤构造样式划分为2大类4种类型,以伸展和挤压为主,主要包括单斜断块、堑垒构造、掀斜断块和逆冲褶皱型。     

塔北隆起北部叠加断裂构造特征与成因背景分析

塔北隆起在塔里木叠合盆地演化时期经历了古克拉通隆起、早期前陆前缘隆起、库车再生前陆盆地斜坡3个阶段。经过两期成盆构造变革阶段，塔北隆起北部垂向上叠加深、浅层两组断裂系统：深层断裂系统为基底逆冲断裂，发育冲断构造、背冲构造组合；浅层断裂系统为正断层，发育地堑、地垒构造样式组合。两组不同性质断裂系统的发育均对应于两期造山挤压背景下前陆盆地形成阶段。笔者认为，深层断裂并非是处于早期前陆变形区域，而是处于挤压背景下板内塔北古克拉通隆起“纵弯”构造变形中岩层破裂的结果。浅层断裂是库车再生前陆盆地阶段塔北隆起北部基底（前中生界构造层）受水平挤压翘曲变形（纵弯变形）导致上覆岩层引张破裂的结果。     

西南三江构造体系及演化、成因

西南三江构造体系突出表现为以昌都-兰坪-思茅地块为中轴的不对称走滑对冲构造,次为与走滑断裂相伴的伸展滑脱、走滑拉分盆地构造体系,再次为块体内部的近北东、北西向走滑断裂系.西南三江造山带构造体系演化分为挤压收缩变形、走滑深熔热隆、走滑剪切伸展、走滑剥蚀隆升等4个阶段.自晚白垩世开始,印度板块与欧亚板块碰撞,西南三江造山带...     

塔里木盆地断裂构造分期差异活动及其变形机理

本文的目的是探讨塔里木盆地断裂构造分期差异活动过程及其变形机理.在地震剖面解释、钻井资料和地质资料综合分析的基础上,通过编制塔里木盆地不同时期断裂系统图,提出控制塔里木盆地断裂构造形成和演化主要构造活动期次为:加里东早期、加里东中期、加里东晚期-海西早期、海西晚期、印支期、燕山期和喜马拉雅期.加里东早期断裂活动受伸展环境制约,沿先存基底断裂带形成张性正断层.加里东中期、加里东晚期-海西早期断裂活动以逆冲作用为主,在塔东、塔中、塘古巴斯、巴楚和麦盖提地区最为发育.海西晚期断裂活动也是以逆冲作用为特征,并从早期断裂强烈活动的塔中、塘古巴斯、玛东等地区,迁移到塔北隆起和东部地区.印支、燕山和喜马拉雅期,前陆地区断裂构造发育,形成叠瓦冲断带、褶皱-冲断带、双重构造、盐相关构造等;但在盆内稳定区,断裂构造不发育,活动性弱.古生代断裂构造发育分布的控制机理,主要与区域大地构造环境的变化和构造转换、先存基底断裂带、大型区域性不整合、滑脱带等要素密切相关.区域大地构造环境的变化和构造转换主要受控于塔里木周缘洋盆的伸展裂解、俯冲消减和洋盆闭合的时限和强度.先存基底断裂带或基底构造软弱带往往控制着后期断裂的发育位置和展布方向.大型区域性不整合和滑脱带控制着断裂构造的发育和分布层位.中、新生代断裂构造发育分布的控制机理,与区域大地构造环境及其构造转换、区域构造位置有关.中、新生代塔里木断裂构造主要分为三种环境,即前陆构造环境、盆内稳定区构造环境和隆升剥蚀区构造环境.盆内稳定区断裂构造不发育,活动性较弱.中、新生代断裂构造主体发育在前陆构造环境中,主要受控于周缘造山带强烈隆升、挤压冲断、走滑-逆冲或逆冲-走滑作用,同时与喜马拉雅晚期盆-山耦合作用及滑脱层的发育有关.     

Tectonic controls on drainage evolution and development of terminal alluvial fans, southern Pyrenees, Spain

An understanding of how drainage patterns respond to tectonics can provide an insight into past deformational events within mountain belts and where sediment flux is supplied to depositional basins. The transverse rivers draining the Spanish Pyrenees show sudden diversions to axial courses and the capture of lateral systems producing large trunk rivers that break through the thrust front at structurally controlled points. The drainage reorganization from the initial regularly spaced pattern in the Late Eocene caused by the growth of thrust‐controlled topography influenced the location of outlets into the Ebro basin. The headward capture and merger of rivers as a result of structural diversion formed two large terminal fan systems during the Oligo‐Miocene along the Pyrenean thrust front. The early structural topographic controls on drainage evolution will have long‐term effects on sedimentation and stratigraphic architecture of foreland basins. This will only be maintained as long as there is tectonic uplift and the river systems strive to re‐attain a regular drainage spacing across the orogenic belt as partly achieved in the Pyrenees.     

库车前陆冲断带克拉苏构造带变形影响因素分析——基于离散元数值模拟研究

在解释库车前陆冲断带克拉苏构造带三维地震剖面的基础上,采用离散元数值模拟手段、单因素变量控制方法,通过六组模拟对比实验,探讨挤压背景下应变速率大小和作用时间、盐岩展布形态、先存盐底辟、基底先存断裂以及基底古隆起等因素,对库车前陆冲断带克拉苏构造带变形的影响。离散元数值模拟结果表明:相比于应变速率大小,应力作用时间对冲断带变形的影响更为显著,变形缩短率相同时导致挤压隆升幅度更大,可达70.25%,向前传播距离均更远,横向上变形范围可达73.82%,盐下层叠瓦状逆冲断裂倾角更小。先存底辟主要影响挤压端垂向变形规模,使得隆升幅度更大。先存断裂主要影响挤压端水平方向变形范围,挤压变形水平传播更远。基底古隆起和盐岩展布形态对克拉苏构造带变形也具有重要影响,基底隆起前沿形成应力集中带,盐岩在此聚集形成构造三角带。由于盐岩的分隔作用,盐上层变形相对较弱,靠近挤压端发育背斜和冲断构造,向盆地方向逐渐变为宽缓的向斜构造。     

构造事件的沉积响应—建立青藏高原大陆碰撞、隆升过程时空坐标的设想和方法

沉积盆地的地层形态、岩相类型以及空间配置样式是构造事件的重要标识.沉积序列中特征岩石组分的出现标志着毗邻造山带隆升的初始启动时间,与物源区地层单元垂向叠置序列相反或相同的岩屑组分剖面分布则是幕式构造旋回的反映.在前陆盆地中砾石层的出现被认为是冲断岩席活动的记录,而在断陷盆地和走滑拉分盆地中通常可识别出100m级的向上变粗和向上变细的旋回层,它们被解释为构造高地重复隆升和溯源侵蚀的结果.最近的研究工作表明,急剧的构造沉降主要是通过细粒级河湖相沉积补偿的,广泛的砾岩进积发生在构造活动的平静期.构造驱动的山脉隆升表现为砾岩地层呈楔状体,纵向河流水系发育;重力均衡回返所导致的山系隆升则形成以横向河流水系为主的板状砾岩沉积.从青藏高原腹地、周缘和外延海洋盆地的沉积记录中可获取重大构造变革时期的信息,也许是解决目前有关印度与亚洲大陆碰撞、高原隆升等时性或穿时性以及限定陆内变形调节机制的一个重要手段.     

构造事件的沉积响应——建立青藏高原大陆碰撞、隆升过程时空坐标的设想和方法

沉积盆地的地层形态、岩相类型以及空间配置样式是构造事件的重要标识，沉积序列中特征岩石组分的出现标志着毗邻造山带隆升的初始启动时间，与物源区地层单元垂向叠置序列相反或相同的岩屑组分剖面分布则是幕式构造旋回的反映，在前陆盆地中砾石层的出现被认为是冲断岩席活动的记录，而在断陷盆地和走滑拉分盆地中通常可识别出100m级的向上变粗和向上变细的旋回层，它们被解释为构造高地重复姓升和溯源侵蚀的结果，最近的研究工作表明，急剧的构造沉降主要是通过细粒级河湖相沉积补偿的，广泛的砾岩进积发生在构造活动的平静期，构造驱动的山脉隆升表现为砾岩地层呈楔状体，纵向河流水系发育；重力均衡回返所导致的山系隆升则形成以横向河流水系为主的板状砾岩沉积，从青藏高原腹地、周缘和外延海洋盆地的沉积记录中可获得取重大构造变革时期的信息，也许是解决目前有关印度与亚洲大陆碰撞、高原隆升等时性或穿时性以及限定陆内变形调节机制的一个重要手段。     

两广云开大山—十万大山地区盆山耦合构造演化——兼论华南若干区域构造问题

云开大山自泛华夏造山作用以来就成为褶皱带和相对隆起区,现今的十万大山及其前身则同时成为前缘凹陷或前陆盆地,它们共同组成了一个盆山耦合系统.整个盆山耦合系统的构造演化可划分为如下阶段:早古生代造山事件第一幕(郁南运动)形成云开复式背斜带,古博白前缘凹陷形成于其东南侧.第二幕(北流运动)使云开复式背斜向西北推进,前陆盆地亦向西北侧迁移.第三幕(广西运动)使云开大山继续褶皱隆起,早印支运动(东吴运动)使钦防海槽褶皱成山,并在其北西侧形成前陆盆地.晚印支运动,广西大容山地区褶皱隆起,此时的前陆盆地已迁移至现今十万大山的东南边缘,奠定了十万大山盆地现今构造轮廓的基础.进入燕山期,随着桂东南逆冲推覆构造前缘不断地向NW方向扩展,侏罗纪-白垩纪时期的前陆盆地也不断地向NW方向迁移.进入新生代喜马拉雅期,本区的构造格局发生了重大变革,即由原来的NW-SE向挤压构造应力场变为NE-SW挤压构造应力场.     

Tectonic setting and sedimentology of Ganga River sediments, India

The Ganga basin provides a present-day example of a peripheral foreland basin. The course of the river is controlled by Himalayan tectonics. Three main types of architectural elements, such as channels (CH), sandy bedforms (SB) and overbank fines (OF) have been developed in Ganga River sediments. The channels (CH) include gravelly (Gs) and sandy channel (Ss) lithofacies. The sandy bedforms (SB) include trough cross-stratified (St), planar cross-stratified (Sp), horizontal stratified (Sh), sandy massive (Sm) and climbing ripple cross-laminated (Sr) lithofacies, all of which are active channel deposits. The overbank fines (OF) include massive silt and clay (Fm), parallel laminated silt and clay (FI) and climbing ripple cross-laminated (Sr) lithofacies. Mega units have been developed in the lower part of the active channel deposits, while small units have been developed in the upper part of active channel deposits, in inactive channel deposits and overbank fines. This study illustrates the seasonal and tectonic control on sedimentation. Petrofacies studies of the sediments indicate a recycled orogen provenance. The sediments are derived from rapidly uplifted fault blocks comprising granite, gneiss and basic and ultrabasic rocks. Lack of textural and compositional maturity suggests a local source of derivation. The principal control on sand composition is source lithology. The hot and humid climate may slightly increase the content of quartz in sand derived from reworked foreland basin sediments. but the effect is neither sufficient to shift the sand compositions out of the recycled orogen field nor does it obscure composition mixing patterns.