Multi‐scale analysis of a migrating submarine channel system in a tectonically‐confined basin: The Miocene Gorgoglione Flysch Formation,southern Italy

The Miocene Gorgoglione Flysch Formation records the stratigraphic product of protracted sediment transfer and deposition through a long‐lived submarine channel system developed in a narrow and elongate thrust‐top basin of the Southern Apennines (Italy). Channel‐fill deposits are exposed in an outcrop belt approximately 500 m thick and 15 km long, oriented oblique to the palaeoflow, which was roughly south‐eastward. These exceptional exposures of channel‐fill strata allow the stacking architectures and the evolution of the channel system to be analyzed at multiple scales, enabling the effects of syn‐sedimentary thrust tectonics and basin confinement on the depositional system development to be deciphered. Two end‐member types of elementary channel architecture have been identified: high‐aspect‐ratio, weakly‐confined channels, and low‐aspect‐ratio, incisional channels. Their systematic stacking results in a complex pattern of seismic‐scale depositional architectures that determines the stratigraphic framework of the deep‐water system. From the base of the succession, two prominent channel complex sets have been recognized, namely CS1 and CS2, consisting of amalgamated incisional channel elements and weakly‐confined channel elements. These channelized units are overlain by isolated incisional channels, erosional into mud‐prone slope deposits. The juxtaposition of different channel architectures is interpreted to have been governed by regional thrust‐tectonics, in combination with a high subsidence rate that promoted significant aggradation. In this scenario, the alternating ‘in sequence’ and ‘out of sequence’ tectonic pulses of the basin‐bounding thrusts controlled the activation of coarse‐clastic inputs in the basin and the resulting stacking architectures of channelized units. The tectonically‐driven confinement of the depositional system limited the lateral offset in channel stacking, preventing large‐scale avulsions. This study represents an excellent opportunity to analyze the stratigraphic evolution of a submarine channel system in tectonically‐active settings from an outcrop perspective. It should find wide applicability in analogous depositional systems, whose stratigraphic architecture has been influenced by tectonically‐controlled lateral confinement and associated lateral tilting.     

北部湾盆地层序地层格架及其内部构成

本文根据地震剖面、测井曲线及钻孔岩心等资料，运用层序地层学工作方法对北部湾盆地进行了层序地层划分，并在此基础上作了沉积体系分析和相分析。     

构造活动盆地沉积层序形成过程模拟——以断陷和前陆盆地为例

应用二维层序地层模拟系统开展了构造活动盆地沉积层序的形成过程的动态模拟分析,揭示了同沉积断裂活动、湖平面变化及沉积物供给量变化相互作用对沉积层序形成的控制作用。模拟表明,快速的构造沉降、相对高的湖平面和大量的沉积物供给是形成相对深水扇三角洲的必要条件;而沉积物的供给量变小或构造沉降量加大时有利于形成近岸湖底扇或水下扇。模拟揭示出断陷湖盆陡坡边缘断裂形成的古地貌坡折控制着低水位域浊积扇或湖底扇的发育部位,同时对水进或高位域的三角洲前缘的沉积中心的分布具控制作用。断裂坡折带的构造沉降是控制可容纳空间变化的关键因素。在陆内前陆逆冲构造边缘,层序发育早期（底部）发育冲积扇和河流沉积,但由于相对快的构造沉降形成水进序列;在快速沉降的晚期沉降速率减小,碎屑体系向盆地方向推进,形成广泛河流三角洲沉积。由隐伏逆冲断裂形成的构造坡折带对低位域的分布具控制作用。在构造坡折带下的低位域砂体与上覆的水进域泥岩组合可形成重要的地层油气藏。     

Tectonic control on fluvial styles: the Balfour Formation of the Karoo Basin, South Africa

The Balfour Formation represents a fully fluvial succession of late Late Permian–earliest Triassic age which accumulated in the foredeep of the Karoo Basin during the overfilled phase of the foreland system. The lack of a coeval marine environment within the limits of the preserved Karoo Basin provides an opportunity to study the stratigraphic cyclicity developed during a time when accommodation was solely controlled by tectonics. The Balfour stratigraphy is composed of a succession of six third-order fluvial depositional sequences separated by subaerial unconformities. They formed in isolation from eustatic influences, with a timing controlled by orogenic cycles of loading and unloading. Sediment accumulation took place during stages of flexural subsidence, whereas the bounding surfaces are related to stages of isostatic uplift. The vertical profile of all sequences displays an overall fining-upward trend related to the gradual decrease in topographic slope during orogenic loading. At the same time, an upward change in fluvial styles can be observed within each sequence, from initial higher to final lower energy systems. The actual fluvial styles in each location depend on paleoslope gradients and the position of the stratigraphic section relative to the orogenic front. Proximal sequences show transitions from braided to meandering systems, whereas more distal sequences show changes from sand-bed to fine-grained meandering systems. The average duration of the Balfour stratigraphic cycles was 0.66 My, i.e. six cycles during 4 My. No climatic fluctuations are recorded during this time, with the long-term climatic background represented by temperate to humid conditions.     

Upper Cretaceous marine‐continental transition (Leonese Area,NW Spain) defined from integrated outcrop and seismic stratigraphy

The Upper Cretaceous succession of the Leonese Area (NW Spain) comprises mixed clastic and carbonate sediments. This succession is divided into two lithostratigraphic units, the Voznuevo Member and the Boñar Formation, which represent fluvial, shoreface, intertidal, subtidal and open‐shelf sedimentary environments. Regional seismic interpretation and sequence stratigraphic analysis have allowed the study of lateral and vertical changes in the sedimentary record and the definition of third‐order levels of stratigraphic cyclicity. On the basis of these data, the succession can be divided into two second‐order depositional sequences (DS‐1 and DS‐2), incorporating three system tracts in a lowstand to transgressive to highstand system tract succession (LST–TST–HST). These sequences are composed of fluvial systems at the base with palaeocurrents that flowed westward and south‐westward. The upper part of DS‐1 (Late Albian–Middle Turonian) shows evidence of intertidal to subtidal and offshore deposits. DS‐2 (Late Turonian–Campanian) comprises intertidal to subtidal, tidal flat, shallow marine and lacustrine deposits and interbedded fluvial deposits. Two regressive–transgressive cycles occurred in the area related to eustatic controls. The evolution of the basin can be explained by base‐level changes and associated shifts in depositional trends of successive retrogradational episodes. By using isobath and isopach maps, the main palaeogeographic features of DS‐1 and DS‐2 were constrained, namely coastline positions, the existence and orientation of corridors through which fluvial networks were channelled and the location of the main depocentres of the basin. Sedimentation on the Upper Cretaceous marine platform was mainly controlled by (i) oscillations of sea level and (ii) the orientation of Mesozoic faults, which induced sedimentation along depocentres. Copyright © 2013 John Wiley & Sons, Ltd.     

沉积记录中的古气候周期及其在高频层序形成中的意义

目前认为,构造升降、气候所控制的湖平面变化以及沉积物的供给对陆相湖盆层序发育的范围、厚度、演化阶段及层序边界的形成起着主要控制作用,而对于同一湖盆演化的不同阶段,则是不同因素对各级层序的形成起着主要的控制作用.某一时期,构造因素决定着较大级别层序边界的形成;而在构造活动相对稳定期,基于天文旋回的气候周期是高频层序形成的主要控制因素.在以往的研究中,对气候周期的深入分析一直较薄弱.加强气候因素的研究,从而更精确地解析高频层序的成因,进行高频层序的划分、对比,预测优质储层和烃源岩的特征及分布是今后能源和盆地研究中必不可少的一个工作重心.另外,随着"天文年代表"概念的提出,天文轨道旋回的方法已成为确定地层年代的一个重要手段.     

Controls on large‐scale patterns of fluvial sandbody distribution in alluvial to coastal plain strata: Upper Cretaceous Blackhawk Formation,Wasatch Plateau,Central Utah,USA

Current models of alluvial to coastal plain stratigraphy are concept‐driven and focus on relative sea‐level as an allogenic control. These models are tested herein using data from a large (ca 100 km long and 300 m thick), continuous outcrop belt (Upper Cretaceous Blackhawk Formation, central Utah, USA). Many channelized fluvial sandbodies in the Blackhawk Formation have a multilateral and multistorey internal character, and they generally increase in size and abundance (from ca 10% to ca 30% of the strata) from base to top of the formation. These regional, low‐resolution trends exhibit much local variation, but are interpreted to reflect progressively decreasing tectonic subsidence in the upper Blackhawk Formation and overlying Castlegate Sandstone. The trend may also incorporate progressively more frequent channel avulsion during deposition of the lower Blackhawk Formation. Laterally extensive coal zones formed on the coastal plain during shallow‐marine transgressions, and define the high‐resolution stratigraphic framework of the lower Blackhawk Formation. Large (up to 25 m thick and 1 to 6 km wide), multistorey, multilateral, fluvial channel‐complex sandbodies that overlie composite erosion surfaces occur at distinct stratigraphic levels, and are interpreted as fluvial incised valley fills. Low amplitude (<30 m) relative sea‐level variations are interpreted as the dominant control on stratigraphic architecture in the lower Blackhawk Formation, which was deposited up to 50 km inland from the coeval shoreline. In contrast, the high‐resolution stratigraphy of the upper Blackhawk Formation is poorly defined, and channelized fluvial sandbodies are poorly organized. Vertical and laterally offset stacking of a small proportion (<10%) of sandbodies produced ‘clusters’ that are not confined by ‘master’ erosion surfaces. Avulsion is interpreted to dominate the stratigraphic architecture of the upper Blackhawk Formation. This data‐driven analysis indicates that alluvial to coastal plain stratigraphic architecture reflects a combination of various allogenic controls and autogenic behaviours. The relative sea‐level control emphasized in sequence stratigraphic models is only rarely dominant.     

关于造山带动力沉积学若干问题的思考

造山带动力沉积学是造山带地质学和大陆动力学研究的重要方面。造山带动力沉积学研究的重要基础是识别造山带的原型沉积盆地,认识其大地构造沉积相和原型沉积盆地的演化。造山带动力沉积学研究的主要内容包括造山带区域地层学、沉积学、大地构造学、造山带原型盆地的充填序列或构造层序、古地理和古海洋及建立沉积盆地的动力模式。其研究方法涉及造山带原型盆地的物源和组分分析、沉积相和沉积体系及沉积构型分析、充填序列和构造层序分析、古流向和古地理分析、沉积厚度和沉降分析以及沉积盆地动力模拟等。     

Changing lake dynamics and sequence stratigraphy of synrift lacustrine strata in a half-graben: an example from the Triassic Ischigualasto–Villa Unión Basin, Argentina

Well‐exposed Triassic rift strata from the Ischigualasto–Villa Unión Basin (NW Argentina) include a 80 to ca 515 m thick lacustrine‐dominated package that can be correlated across a half‐graben using key stratigraphic surfaces (sequence boundaries, lacustrine flooding surfaces and forced regressive surfaces). The characteristics of the synrift lacustrine fill in different parts of the half‐graben have been examined and the mechanisms controlling sedimentation inferred. A variety of sedimentary environments are recognized including; volcaniclastic floodplain, mildly saline lake and playa lake, offshore lacustrine, delta front to fluvial‐dominated and wave‐dominated deltas, distributary and fluvial channel, and interdistributary bay. The succession can be divided into four stratigraphic sequences (SS1 to SS4), the oldest of which (SS1) contains volcaniclastic, fluvial and saline lake deposits; it is thickest close to the western border fault zone, reflecting more rapid subsidence here. Accommodation exceeded sediment and water input during SS1. The second and third sequences (SS2 and SS3) mark the onset of widespread lacustrine sedimentation, reflecting a balance between accommodation creation and water and sediment fluxes. Sequences SS2 and SS3 are represented by offshore meromictic lacustrine and deltaic deposits, the latter mostly sourced from the flexural and southern axial margins of the half‐graben. The presence of stacked parasequences bound by lacustrine flooding surfaces is related to climatically induced lake‐level fluctuations superimposed on variable rates of subsidence on the controlling rift border fault zone. The youngest sequence (SS4) is represented by the deposits of littoral lacustrine and shallow shelf deltas distinguished by a change in lithofacies, palaeocurrents and sandstone composition, suggesting a switch in sediment supply to the footwall margin to the NW. The change in the sediment source is related to reduced footwall uplift, the possible presence of a relay ramp and/or supply from a captured antecedent drainage network. During SS4, the rate of creation of accommodation was exceeded by the sediment and water discharge. The stratigraphic evolution of lacustrine strata in the half‐graben was mainly controlled by tectonic processes, including subsidence rate and the growth and evolution of the border fault zone, but changing climate (inducing changes in water balance and lake level) and autocyclic processes (delta lobe switching) were also important.     

Tectono-stratigraphic evolution and hydrocarbon exploration in the Eocene Southern Lufeng Depression,Pearl River Mouth Basin,South China Sea

The structural evolution and stratigraphic architecture of the Southern Lufeng Depression in the Pearl River Mouth Basin, South China Sea show two second-order sequences (SSQ1 and SSQ2) and nine third-order sequences (WSQ1-5 and ESQ1-4) within the Eocene rift-related successions. Based on integrated interpretations of seismic reflections, well logs and core data, five distinct tectono-stratigraphic patterns are identified: (1) the initial synrift-I sequence (WSQ1) of low tectonic subsidence, overfilled by alluvial fan or fan-delta deposits and volcanic deposits, with no clear systems tracts; (2) the climax synrift-I sequences (WSQ2–4) developed in response to rapid tectonic subsidence, generally consisting of a low-stand systems tract (LST), transgressive systems tract (TST) and high-stand systems tract (HST); (3) the late synrift-I sequence (WSQ5) characterised by a decreased tectonic subsidence rate, dominated by braided delta, deep and shallow lacustrine sediments, mainly constructed by TST and HST; (4) the early synrift-II sequences (ESQ1–2) rapidly filled by braided deltaic sandstone and mainly composed of TST and HST with less common LST units; and (5) the late synrift-II sequences (ESQ3–4), which are totally filled by braided deltaic system in a shallow-water lake setting, presenting typical imbricate clinoforms or sub-parallel seismic configurations, consisting of only TST and HST components. During the climax stage of synrift-I development, the depositional setting changed from a prominent shallow lake (WSQ2) to a deep-lucustrine with turbiditic deposits (WSQ3) and finally dominated by mostly braided deltaic-shallow lacustrine deposits (WSQ4); the HST occupies an increasing proportion from early to late. Furthermore, the stratigraphic patterns, especially LST units of the climax synrift-I stage, are significantly influenced by topographic variations and slope-break belt types in the hanging dip-slope. This study reveals that the spatial and temporal evolution of lacustrine depositional and stratigraphic patterns were significantly controlled by the interplay of tectonic subsidence and sediment supply, and provides a fundamental basis for predicting the favourable reservoirs and geometry of source rocks related to the general variability of Eocene rift-related tectonic subsidence in the Southern Lufeng Depression of the Pearl River Mouth Basin. Furthermore, the topographic responses of differential active fault-stepped patterns associated with magma intrusions, highlight the variability of relevant sequence architectures in the hanging dip-slope in lacustrine rift basins.     

Climate‐modulated sequence development in a tropical rift basin during the Late Palaeocene to Early Eocene super greenhouse Earth

Sequence developments in rift basins are considered to be influenced largely by tectonics and to a lesser extent by eustatic sea‐level and climate. Studies indicate that in passive margin basins, climate can mask the effects of tectonics and eustasy by modulating the sediment supply. It is, however, less understood how the sedimentary sequence in rift basins might respond to strong climatic fluctuations where tectonic pulses generate rapid accommodation space. Here a case study has been provided to assess the effect of climate vis à vis sea‐level and tectonics on sequence development in the Cambay rift basin, western India, during the Early Palaeogene (Late Palaeocene to Early Eocene) super greenhouse globe. Facies analysis of this shale–lignite sequence suggests deposition in a lagoon/bay, developed over the Deccan Trap basement. Detailed sequence stratigraphic analysis using basin‐wide representative composite sections, marker lignite seam, event bed and high‐resolution carbon isotope (δ¹³C) chemostratigraphy suggest an overall transgressive motif. Among the three prominent Early Eocene eustatic highstands, only the one at ca 53·7 Ma is expressed by the thickest coal accumulation throughout the basin. Expression of the other sequence stratigraphic surfaces is subdued and can be due to the overall finer grain size of the sediment or local variation in the subsidence rate at different fault‐controlled mini‐basins. Enigmatic presence of a maximum flooding surface coinciding with the 53·7 Ma climate event (Eocene Thermal Maximum 2), manifested by negative carbon isotope excursion, indicates possible influence of climate over and above tectonics in developing the rift sequence. Qualitative rainfall variation assessed using the magnitude of the carbon isotope excursion and pollen abundance show that a relatively dry/low precipitation climatic phase during the Eocene Thermal Maximum 2 hindered the siliclastic supply to the basin. Thus, it has been inferred that climate‐induced high siliciclastic supply possibly enhanced the autocyclic reorganization and hindered the development of the key sequence stratigraphic surfaces across the basin during climate extremes.     

苏皖下扬子区震旦纪—中三叠世海相层序地层

笔者运用板块构造和层序地层学的理论和方法，从露头区精细研究开始，寻找层序地层单元的识别标志和沉积相标志，拟建立起研究区综合层序地层格架。在此基础上结合区域构造资料和沉积背景分析，对苏皖下扬子区的震旦纪－中三叠世的层序地层进行划分，共认识别出11个二级层序，64个三级层序。     

济阳坳陷义和庄凸起东部燕山期构造负反转及层序地层样式响应

通过钻井、测井与地震数据,依据不整合面分析、断层活动速率分析与地层的"负向结构"分析,在义和庄凸起东部燕山期内识别出一期发生于中晚侏罗世之交的构造负反转,并据此将义和庄凸起燕山期划分为早期与晚期两个阶段.通过单井与连井层序地层分析,分别建立了燕山早期与晚期的层序地层样式,两者在层序结构及内部沉积充填等方面表现出巨大差异.早期层序地层不具有显著的沉积厚度分异,且格架内部充填河流相沉积;晚期因构造负反转而形成小型拉张断陷盆地,沉积厚度分异明显,内部以扇三角洲沉积充填为主,呈现出对构造负反转的显著响应.燕山期构造-层序地层学的研究可为中国东部其他具有相似构造背景盆地前新生代的油气勘探提供借鉴.     

Stratigraphic architecture of the Cenozoic succession in the McMurdo Sound region,Antarctica: An archive of polar palaeoenvironmental change in a failed rift setting

The Victoria Land Basin forms part of the failed West Antarctic Rift, and preserves a Cenozoic succession up to 4 km thick that records the onset of Cenozoic glaciation, and the history of Antarctic glaciation over the past 34 Myr. This succession is relevant both to investigations of modern climate change and to studies of long‐term palaeoclimate change in general. This study provides a sedimentological and stratigraphic review of the Victoria Land Basin succession, based on analysis of several continuous drillcores acquired since the 1970s, and supported by seismic stratigraphic analysis of a large array of seismic reflection data. An array of fifteen lithofacies is recognized within the Victoria Land Basin Cenozoic succession, including fossiliferous and diversely bioturbated mudrocks and diatomites, texturally mature sandstones and conglomerates, mixed mudstones and sandstones with dispersed gravel with restricted bioturbation, and diamictites and associated lithologies. These facies record a variety of marine, glaciomarine, proglacial and subglacial environments. Locally, volcanic and volcaniclastic deposits are interbedded in the succession. Lithofacies are arranged in repetitive vertical stacking patterns (depositional sequences) that record glacial advance–retreat cycles with attendant relative sea‐level changes. Seven varieties of depositional sequences (stratigraphic motifs) are recognized within the succession as a whole, and interpreted to record a range of depositional settings from rifts unaffected by glacial ice (Motif 7), through varying degrees of glacial influence with abundant meltwater contributions (Motifs 6 to 3), to cold, polar glaciated environments such as that of today (Motifs 2 and 1). Overall, there is a gradual trend upward through the succession from Motif 7 at the base towards Motif 1 at the top, but the trend is not monotonic. A significant conclusion of this work is that a record of dynamic climate and glacial conditions is preserved through the entire 34 Myr period of the Cenozoic icehouse, at least in the Victoria Land Basin. Intervals characterized by consistent stratigraphic style (motifs) are recognized throughout the Victoria Land Basin succession. These intervals are of 1 to 6 Myr duration, each containing numerous depositional sequences; they are one to two orders of magnitude longer than glacial–interglacial cycles, and record periods during which environmental conditions varied in an internally consistent manner. These intervals are considered to reflect convolutions of orbital parameters that remained stable for periods of 10⁶ a, and then switched to alternative configurations. Such intervals are directly analogous to 1 to 8 Myr intervals characterized by glaciogenic strata that are preserved within the late Palaeozoic of eastern Australia among other areas, and may be a recurring stratigraphic response to icehouse climate regimes through geological time.     

Sequence stratigraphic architectures and responses to syndepositional tectonic evolution in the Paleogene Lingshui Sag,Qiongdongnan Basin,northwestern South China Sea

ABSTRACT

The syndepositional tectonic evolution and sequence stratigraphic architecture of the Paleogene Lingshui Sag, Qiongdongnan Basin, South China Sea, are investigated with seismic profiles, boreholes and well logs. First, according to the recognized sequence boundaries, the Paleogene sequence stratigraphic framework is established. Then, based on analyzing the subsidence history and paleogeomorphology evolution, the Paleogene Lingshui Sag is clarified to present episodic tectonic evolution, showing tectonic stage-I, stage-II and stage-III. From stage-I to stage-III, the major basin-marginal faults gradually lost control over the subsidence center, which moved away from the initial basin margin to the late central basin. Structural slope break belts, such as fault slope break belts and gentle slope break belts, formed through the above three tectonic stages and controlled the formation of four types of relevant distinct sequence stratigraphic architectures, namely, Types A1, A2, B1 and B2. Finally, the responses of sequence stratigraphic architectures to tectonic evolution are described, and the favorable hydrocarbon reservoirs in the different architectures are discussed, which constitute stratigraphic traps, fault traps, lenticular lithologic traps and updip wedge-out traps. This information is beneficial in prospecting for subtle traps in basins located in deepwater areas.     

华南晚三叠世前陆盆地的成因地层格架及演化历史

在详细研究盆地中各类沉积体系的沉积构成和演化过程的基础上,通过成因地层对比,建立了残留海湾—前陆盆地的成因地层格架。根据沉积体系的时空组合及其与相关等时性地层面的配置关系,划分出了3个构造沉积幕,每个构造沉积幕都是盆地基底荷载挠曲变形至弹性回跳过程的沉积响应。海平面升降变化和盆内软沉积物压实沉降虽然不能触发和主控盆地基底的构造挠曲旋回,但对各构造沉积幕的地层构型和持续时间有重要影响。盆地基底荷载挠曲变形与海平面升降或压实沉降过程以不同方式叠加,产生各种类型的构造沉积幕,与前陆盆地共生的还有后陆盆地和残留的弧后盆地。     

A sedimentological model for the continental Upper Triassic Tadrart Ouadou Sandstone Member: recording an interplay of climate and tectonics (Argana Valley; South‐west Morocco)

The continental Upper Triassic Tadrart Ouadou Sandstone Member was deposited in an extensional setting on the Pangaean continent, strongly influenced by a low‐latitude climatic regime (10° to 20° north). Complex interaction of basin subsidence and climatically driven processes led to high facies variability and a lack of correlatable units across the Argana Valley exposures. A process‐orientated approach integrating detailed facies with architectural element analysis was undertaken, which resulted in a multistage depositional model for the Tadrart Ouadou Sandstone Member. The basin‐scale model shows that basal alluvial fan and braided river systems are confined to the centre of the Argana Valley exposures. Aeolian deposits occur throughout the sequence, but dominate in the north. After a phase of playa deposition, prominent basin‐wide fluvial incision of up to 8 m marks the onset of perennial fluvial flow. These well‐sorted, internally complex and locally highly amalgamated fluvial sandstones are widespread throughout the basin and are focused in a north to south (south‐west) flowing channel system. After a final stage of aeolian sedimentation, sandstone deposition of the Tadrart Ouadou Sandstone Member in the Argana Valley is terminated rapidly by the onlap of lacustrine mudstones of the Sidi Mansour Member. The study revealed that, except for one pronounced period of perennial conditions, sedimentation is controlled largely by ephemeral fluvial flow, alternating ground water tables, deflation processes and periods with limited periodic local run‐off. The study highlights that facies architecture in the basin is the result of complex interaction of local syn‐sedimentary tectonics and the climatic regime within the basin, but also the climate of the catchment area to the east. The data suggest a proximal to mid‐distal basin setting in the rain‐shadow to the west of a mountain range (Massif Ancien), which exerted a strong control on the depositional environments of Triassic deposits exposed in this part of South‐west Morocco.     

川北前陆盆地上三叠统须家河组陆相层序地层

中国中西部前陆盆地大多具有陆内俯冲造山形成的特点,层序地层学在这类前陆盆地中的应用是一个值得研究的新领域。对川北前陆盆地上三叠统须家河组5条露头剖面和1条测井剖面进行详细沉积相分析和层序地层划分,同时阐述了沉积相迁移规律、层序界面类型、层序发育特征及基准面变化;将川北前陆盆地上三叠统须家河组划分为4个三级层序(TS1,TS2,TS3和TS4)。大竹、开江一带须家河组沉积厚度为400～600m,4个层序发育完整;向北东至万源一带地层变薄至100余m,保存残留不全的须家河组只能归为1个三级层序(TS4)。在露头剖面和测井剖面层序地层划分的基础上建立的层序地层格架表明:TS1—TS2以曲流河及曲流河三角洲沉积体系为主,盆地处于稳定坳陷和慢速充填的欠补偿状态,TS3—TS4以冲积扇、辫状河及辫状河三角洲沉积体系为主,盆地处于强烈坳陷和快速充填的过补偿状态。沉积相的时空叠置样式受北部秦岭造山带构造活动的制约作用较为明显。     

裂谷地层的气候和构造控制:Zscape模型分析与在松辽盆地北安断陷的应用

气候和构造是裂谷盆地地层形成的两个重要控制因素。Zscape数字陆地景观演化模型通过对裂谷盆地汇水扇体系的模拟揭示出一些与裂谷盆地地层形成相关的气候及构造过程。Zscape模型的相关实验结果与层序地层结构的分析认为:(1)扇面积与断层滑动速率成反比;(2)高水位期大量沉积物进积是断层滑动速率减小所引发的;(3)层序界面的形成与低水位和水进沉积是降水速率变化所致。这些认识用于分析北安断陷沙河子期大量扇体沉积的发育和层序结构的形成。沙河子组下部层序发育时期构造活动剧烈,上部层序发育时期构造活动相对趋于稳定,断裂活动和降水速率的变化控制了层序发育。Zscape模型及其实验结果的地质分析,以及在北安断陷的应用显示,构造和气候的单因素分析对一些地质认识,特别是沉积作用对于断裂活动的滞后性的理论解释起到了推动作用。     

Three-dimensional evolution of the Keuper of the Paris basin based on detailed isopach maps of the stratigraphic cycles: tectonic influences

Detailed isopach maps of the stratigraphic cycles of the Keuper of the Paris basin are used to reconstruct the 3D evolution of the basin cycle by cycle and to investigate the influence of tectonic movements. The major base-level cycles record variations in the rate of subsidence in time and space. The area of greatest subsidence, which was confined to the east of the basin during the Scythian–Carnian cycle, shifted northwestwards during the Carnian–Liassic cycle. Within the “Marnes irisées inférieures”, the E–W faults abruptly limited the extent of salt deposits to the north and south by forming a “corridor” where subsidence was greater. The westward shift of areas of subsidence induced by the migration of fault activity enhanced the migration of salt series which was bounded by the Saint-Martin-de-Bossenay fault. The cessation of fault activity in the eastern part of the basin marked the end of halite sedimentation. From the “Grès à roseaux” formation, a general northwestward tilt of the basin with corresponding depocentre migration induced a truncation within the “Marnes irisées supérieures”. The depocentres were located in the west which was the site of most fault activity which influenced the fluvial deposits by creating tilted blocks where sediment could accumulate.