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1.
Tectono-stratigraphic analysis of the East Tanka fault zone (ETFZ), Suez Rift, indicates that the evolution of normal fault segments was an important control on syn-rift depositional patterns and sequence stratigraphy. Sedimentological and stratigraphic analysis of the Nukhul Formation indicates that it was deposited in a narrow (ca 1–2 km), elongate (ca 5 km), fault-bounded, tidally influenced embayment during the low subsidence rift-initiation phase. The Nukhul Formation is composed of transgressive (TST) and highstand (HST) systems tract couplets interpreted as reflecting fault-driven subsidence and the continuous creation of accommodation in the hangingwall to the ETFZ. The overlying Lower Rudeis Formation was deposited during the high subsidence rift-climax phase, and is composed of forced regressive systems tract (FRST) shallow marine sandbodies, and TST to HST offshore mudstones. Activity on the ETFZ led to marked spatial variability in stratal stacking patterns, systems tracts and key stratal surfaces, as footwall uplift, coupled with regressive marine erosion during deposition of FRST sandbodies, led to the removal of intervening TST–HST mudstone-dominated units, and the amalgamation of FRST sandbodies and the stratal surfaces bounding these units in the footwall. This study indicates that the evolution of normal fault segments over relatively short (i.e. <1 km) length-scales has the potential to enhance or suppress a eustatic sea-level signal, leading to marked spatial variations in stratal stacking patterns, systems tracts and key stratal surfaces. Crucially, these variations in sequence stratigraphic evolution may occur within time-equivalent stratal units, thus caution must be exercised when attempting to correlate syn-rift depositional units based solely on stratal stacking patterns. Furthermore, local, tectonically controlled variations in relative sea level can give rise to syn-rift stacking patterns which are counterintuitive in the context of the structural setting and perceived regional subsidence rates. 相似文献
2.
兰州-民和盆地河口群形成于早白垩世，其间充填了巨厚的陆源碎屑物，碎屑物的组合内容和方式反映了冲积扇相，扇三角洲相，湖泊相沉积体系占主导，盆地地层层序具有退积型。加积型，进积型叠置的变化旋回，显示了全韵律的特点。代表了构造旋回幕的产物。根据盆地的发展演化特征和层序界面的确定，初步建立了盆地的层序地层格架，同时阐述了盆地的演化过程。 相似文献
3.
The Lower Jurassic Mashabba Formation crops out in the core of the doubly plunging Al-Maghara anticline, North Sinai, Egypt. It represents a marine to terrestrial succession deposited within a rift basin associated with the opening of the Neotethys. Despite being one of the best and the only exposed Lower Jurassic strata in Egypt, its sedimentological and sequence stratigraphic framework has not been addressed yet. The formation is subdivided informally into a lower and upper member with different depositional settings and sequence stratigraphic framework. The sedimentary facies of the lower member include shallow-marine, fluvial, tidal flat and incised valley fill deposits. In contrast, the upper member consists of strata with limited lateral extension including fossiliferous lagoonal limestones alternating with burrowed deltaic sandstones. The lower member contains three incomplete sequences (SQ1-SQ3). The depositional framework shows transgressive middle shoreface to offshore transition deposits sharply overlain by forced regressive upper shoreface sandstones (SQ1), lowstand fluvial to transgressive tidal flat and shallow subtidal sandy limestones (SQ2), and lowstand to transgressive incised valley fills and shallow subtidal sandy limestones (SQ3). In contrast, the upper member consists of eight coarsening-up depositional cycles bounded by marine flooding surfaces. The cycles are classified as carbonate-dominated, siliciclastic-dominated, and mixed siliciclastic-carbonate. The strata record rapid changes in accommodation space. The unpredictable facies stacking pattern, the remarkable rapid facies changes, and chaotic stratigraphic architecture suggest an interplay between allogenic and autogenic processes. Particularly syndepositional tectonic pulses and occasional eustatic sea-level changes controlled the rate and trends of accommodation space, the shoreline morphology, the amount and direction of siliciclastic sediment input and rapid switching and abandonment of delta systems. 相似文献
4.
This study combines data from many published case studies to undertake a quantitative characterization of clastic parasequences, with the aim to determine how accommodation, sediment supply and autogenic sediment-storage dynamics are recorded in their sedimentary architecture and stacking patterns. Results of this study are used to critically evaluate the validity of paradigms and models that are routinely used to explain and predict trends in the anatomy and arrangement of parasequences. Data on 957 parasequences from 62 case studies of clastic, shallow-water successions were coded in a relational database, which includes outcrop and subsurface datasets of ancient and Quaternary examples. These units cover the preserved records of both river-dominated deltas and wave-dominated coasts, representing shoreline transits over a breadth of timescales, likely of both local and regional extent. The role of extant accommodation, rates of creation of accommodation and rates of sediment supply in determining parasequence architecture is assessed through analysis of relationships between: (i) proxies of these variables at different scales (rates of aggradation and progradation, facies-belt shoreline trajectories, systems-tract type, parasequence-set stacking patterns, parasequence progradation angle and stratigraphic rise, size of feeder rivers); and (ii) parameters that describe the geometry and stacking style of parasequences, and associated shallow-water sand bodies. Statistical analyses of database outputs indicate which proxies of accommodation, sediment supply and accommodation/sediment-supply ratio are significant as predictors of parasequence architecture, and allow for interpretations of the importance of allogenic and autogenic factors. The principal results of this study reveal the following: (i) parasequence thickness varies as a function of water depth, accommodation generation and erosional truncation, and these variations are also reflected across types of systems tracts and parasequence sets; (ii) the dip length of parasequence sand bodies demonstrates scaling with measures of accommodation/sediment-supply ratio at multiple scales, partly in relation to the possible effect of sediment supply on progradation rates; (iii) in systems tracts, stratigraphic trends in parasequence stacking due to autogenic mechanisms or to acceleration or deceleration in relative sea-level fluctuations are not revealed quantitatively; (iv) some association is seen between the abundance of deltaic or river-dominated parasequences and progradational stacking; (v) positive but modest correlation is observed between measures of river-system size and the dip length of shallow-marine parasequence sand bodies. The resulting insights can be applied to guide sequence stratigraphic interpretations of the rock record and the characterization of sub-seismic stratigraphic architectures of subsurface successions. 相似文献
5.
Biplab Bhattacharya Joyeeta Bhattacharjee Sandip Bandyopadhyay Sudipto Banerjee Kalyan Adhikari 《Journal of Earth System Science》2018,127(2):29
The present research is an attempt to assess the Barakar Formation of the Raniganj Gondwana Basin, India, in the frame of fluvio-marine (estuarine) depositional systems using sequence stratigraphic elements. Analysis of predominant facies associations signify deposition in three sub-environments: (i) a river-dominated bay-head delta zone in the inner estuary, with transition from braided fluvial channels (FA-B1) to tide-affected meandering fluvial channels and flood plains (FA-B2) in the basal part of the succession; (ii) a mixed energy central basin zone, which consists of transitional fluvio-tidal channels (FA-B2), tidal flats, associated with tidal channels and bars (FA-B3) in the middle-upper part of the succession; and (iii) a wave-dominated outer estuary (coastal) zone (FA-B4 with FA-B3) in the upper part of the succession. Stacked progradational (P1, P2)–retrogradational (R1, R2) successions attest to one major base level fluctuation, leading to distinct transgressive–regressive (T–R) cycles with development of initial falling stage systems tract (FSST), followed by lowstand systems tract (LST) and successive transgressive systems tracts (TST-1 and TST-2). Shift in the depositional regime from regressive to transgressive estuarine system in the early Permian Barakar Formation is attributed to change in accommodation space caused by mutual interactions of (i) base level fluctuations in response to climatic amelioration and (ii) basinal tectonisms (exhumation/sagging) related to post-glacial isostatic adjustments in the riftogenic Gondwana basins. 相似文献
6.
B. Krapez 《Australian Journal of Earth Sciences》2013,60(4):355-380
The new approaches to stratigraphy, that permit geodynamic interpretations of rock units during mapping, are beginning to be applied to Precambrian successions. Foremost among the new approaches is sequence stratigraphy. In its simplest form, the technique combines the mapping of facies and time‐significant bedding surfaces. The primary surface is the unconformable sequence boundary, or its correlative conformity. However, sequence stratigraphy is not only the documentation of the vertical and internal order of rock units bounded by unconformities, but also the documentation of the hierarchical rank of those units because there are three ranks of unconformity‐bounded sequences. First‐order sequences (megasequences and megasequence sets) record global tectonic cycles. Second‐order sequences (supersequences) record depositional basins or their tectonic stages. Third‐order sequences (depositional sequences) are basin‐filling rhythms. A depositional sequence, regardless of its provenance, geodynamic setting and contained depositional systems, is divided internally into sets of sedimentation units that additively have progradational, aggradational or retrogradational stacking patterns. These patterns record the relationships between the rate of sediment accumulation and the rate at which space was made available for sediment accumulation (or rate of creation of accommodation). Depositional sequences are therefore the non‐random, but not necessarily periodic, cyclic linkage between sediment flux and accommodation, and are a reflection of geodynamic evolution. The importance of eustasy in sequence stratigraphy should be de‐emphasised. Instead the role of the sequence approach in identifying basin‐filling rhythms, whatever their cause, should be stressed. The adaptability of the technique is best viewed by using examples in which tectonic controls were dominant and chaotic responses evident. Despite the uniqueness of each basin‐fill, sequence mapping reveals an order in stratigraphic style that is inherent to basin type, regardless of basin age. Greater acceptance of the sequence approach will add significantly to the revolution in Precambrian geology, because the technique can establish the conformity in stratigraphic style between, and within, the Phanerozoic and Precambrian rock records. 相似文献
7.
Regressive and transgressive sequences in a raised Holocene gravelly beach, southwestern Crete 总被引：2，自引：0，他引：2
Both a modern and a raised, late Holocene gravelly beach have been studied along the cliffed coast near the village of Chora Sfakion in southwestern Crete, Greece. The Holocene beach shows the record of regional, well-documented relative sea-level changes, in the form of regressive and transgressive sequences. The texture, fabric and depositional architecture of these sequences are described and compared with those of the modern, microtidal beach there. The depositional history of the raised beach is discussed in terms of the sediment transport processes and relative sea-level changes. The regressive sequences of both the modern and the Holocene beach resemble those of the mesotidal beaches in the Sker district of southwest Wales, described by Bluck (1967). The transgressive sequence of the Holocene beach resembles the mesotidal beach sequence near Newton (southwest Wales), recognized by Bluck as another type of progradational (regressive) beach. Therefore, transgressive beach sequences in the stratigraphic record might easily be overlooked or misinterpreted as regressive. The stratigraphic depositional patterns of gravelly beach systems are, apparently, still poorly understood. 相似文献
8.
扇三角洲体系可发育在断陷盆地演化的不同阶段，但类型有所不同，分为进积型和退积型。松辽东缘断陷盆地中扇三角洲体系不同类型在盆地充填序列中发育位置反映出湖侵—湖退的周期过程。特点是伴随湖侵发育退积型扇三角洲，而伴随湖退发育进积型扇三角洲。扇三角洲类型的特征与发育位置分析可以作为体系域类型的识别标志，并有助于层序过程的理解 相似文献
9.
《Gondwana Research》2002,5(3):683-699
The early Carboniferous sedimentation of the Tethyan Margin of Gondwana in the Kashmir Himalaya represents alternating siliciclastic - carbonate succession consisting of distinct stratigraphic sequences which are bounded by discontinuities. The discontinuities in the sedimentation are related to environmental changes in the form of subaerial exposure, subaqueous erosion, subaqueous omission or changes in texture and facies. These distinct surface zones or time significant boundaries can be correlated across the depositional platform. Low stand, high stand and transgressive sedimentation units in the lower and middle parts of early Carboniferous Syringothyris Limestone Formation in Banihal area have been recognised. This is explained by superposition of high frequency and low amplitude sea level fluctuations on a large-scale trend under greenhouse conditions during the early Carboniferous period. The facies associations present in the early Carboniferous succession of the Himalaya broadly represent intertidal (peritidal), shallow subtidal, deeper subtidal, off-shore-slope and deeper environments. Discontinuities that are interpreted as progradational, retrogradational and aggradational phases of sedimentation bound these facies associations. This formation represents continental margin depositional setting which is authenticated by deposition of siliciclastic sediments. This marginal depositional setting is greatly affected by numerous dynamic processes including tectonic and other active sea as well as continental processes. The records of all those processes in this formation reflect the eustatic changes in sea level. These periodic eustatic changes have generated the various discontinuities, stratigraphic sequences or systems tracts. Overall it appears that interplay of many processes such as sediment supply, thermal and tectonic activity, eustatic and climatic changes in the Kashmir Tethyan depositional basin generated these distinct depositional sequences during the early Carboniferous period. 相似文献
10.
Stratigraphic patterns and sequence development in tectonically active extensional basins remain poorly documented in comparison with passive‐margin settings. Rift basin fills are generally characterized by coarsening‐upward trends in response to the rapid creation of accommodation by extensional faulting, and the progressive filling of graben during more quiescent periods. The Early Permian Irwin River Coal Measures in the Northern Perth Basin (Western Australia) record a complex stratigraphic arrangement of conglomerate, sandstone, mudstone and coal, and have been attributed to delta plain depositional environments that developed in a cool–temperate climatic setting during syn‐rift activity. Sedimentary analysis of outcrop and core data from the fault‐bounded Irwin Terrace is used to distinguish nine facies associations reflecting deposition in braided rivers, fixed‐anastomosed channel belts, tide‐influenced coastal environments and storm‐affected distal bays. The broader depositional system is interpreted as a morphologically asymmetrical tide‐dominated embayment with a fluvial and wave influence. The stratigraphic architecture of the Irwin River Coal Measures was strongly influenced by the evolving rift basin margin. Fault reactivation of the major basin‐bounding Darling Fault in the early syn‐rift phase caused footwall uplift and the inception of transverse palaeo‐valleys occupied by braided fluvial systems. Fault block subsidence during the subsequent balanced, backstepping and drowning phases resulted in a dominantly retrogradational stacking pattern indicating progressive flooding of marginal‐marine areas and culminating in deposition of distal marine elements. In the active rift basin, it is proposed that preservation of a shallow‐marine syn‐rift sequence was promoted by the geomorphological confinement of the embayed system increasing tidal current acceleration and hampering transgressive ravinement. The proposed sequence model demonstrates that transgressive successions can develop in the early syn‐rift phase in response to footwall uplift and tectonic subsidence. The syn‐rift sequence recording the filling of an embayment on a rift basin margin may be applied in similar tectonic and/or depositional contexts worldwide. 相似文献
11.
Sequence stratigraphy of the Lower Cenomanian Bahariya Formation, Bahariya Oasis, Western Desert, Egypt 总被引：1，自引：0，他引：1
The Lower Cenomanian Bahariya Formation corresponds to a second-order depositional sequence that formed within a continental shelf setting under relatively low-rate conditions of positive accommodation (< 200 m during 3–6 My). This overall trend of base-level rise was interrupted by three episodes of base-level fall that resulted in the formation of third-order sequence boundaries. These boundaries are represented by subaerial unconformities (replaced or not by younger transgressive wave ravinement surfaces), and subdivide the Bahariya Formation into four third-order depositional sequences.
The construction of the sequence stratigraphic framework of the Bahariya Formation is based on the lateral and vertical changes between shelf, subtidal, coastal and fluvial facies, as well as on the nature of contacts that separate them. The internal (third-order) sequence boundaries are associated with incised valleys, which explain (1) significant lateral changes in the thickness of incised valley fill deposits, (2) the absence of third-order highstand and even transgressive systems tracts in particular areas, and (3) the abrupt facies shifts that may occur laterally over relatively short distances. Within each sequence, the concepts of lowstand, transgressive and highstand systems tracts are used to explain the observed lateral and vertical facies variability.
This case study demonstrates the usefulness of sequence stratigraphic analysis in understanding the architecture and stacking patterns of the preserved rock record, and helps to identify 13 stages in the history of base-level changes that marked the evolution of the Bahariya Oasis region during the Early Cenomanian. 相似文献
12.
The Kerinitis Delta in the Corinth Rift, Greece, is a footwall derived, coarse‐grained, Gilbert‐type fan delta deposited in the hangingwall of a linked normal fault system. This giant Gilbert‐type delta (radius 3·8 km, thickness > 600 m) was supplied by an antecedent river and built into a brackish to marine basin. Although as yet poorly dated, correlation with neighbouring deltas suggests that the Kerinitis Delta was deposited during a period of 500 to 800 ka in the Early to early Middle Pleistocene. Facies characterizing a range of depositional processes are assigned to four facies associations (topset, foreset, bottomset and prodelta). The dominantly fluvial topset facies association has locally developed shallow marine (limestone) and fluvial‐shoreface sub‐associations. This delta represents a subsidence‐dominated system in which high fault displacement overwhelmed base‐level falls (creation of accommodation predominantly ≥ 0). Stratal geometries and facies stacking patterns were used to identify 11 key stratal surfaces separating 11 stratal units. Each key stratal surface records a landward shift in the topset breakpoint path, indicating a rapid increase in accommodation/sediment supply. Each stratal unit records a gradual decrease in accommodation/sediment supply during deposition. The cyclic stratal units and key stratal surfaces are interpreted as recording eustatic falls and rises, respectively. A 30 m thick package of foresets below the main delta records the nucleation of a small Proto‐delta probably on an early relay ramp. Based on changes in stratal unit geometries, the main delta is divided into three packages, interpreted as recording the initiation, growth and death of the controlling fault system. The Lower delta comprises stacked, relatively thin, progradational stratal units recording low displacement on the young fault system (relay ramp). The Middle delta comprises vertically stacked stratal units, each recording initial aggradation–progradation followed by progradation; their aggradational component increases up through the Middle delta, which records the main phase of increasing rate of fault displacement. The Upper delta records pure progradation, recording abrupt cessation of movement on the fault. A major erosion surface incising basinward 120 m through the Lower and Middle delta records an exceptional submarine erosion process (canyon or delta collapse). 相似文献
13.
The controls and development of early-post-rift, deep-water depositional systems are poorly understood due to their commonly deeply-buried nature. As a consequence, in the subsurface there is usually a lack of well penetrations and/or weak seismic imaging. At outcrop, early post-rift strata have commonly been deformed beyond reasonable recognition by later inversion tectonics. In contrast to these systems, the North Viking Graben shows a well-imaged Cretaceous early post-rift package with good well control and little effect from inversion. Therefore, this paper examines the early post-rift, deep-water depositional systems of the North Viking Graben to determine the controls on their stratigraphic position, geometry and evolution, and thus provide an analogue for comparable systems. Greater understanding of such systems will allow for the enhanced prediction of reservoir units in the subsurface and development of new play models since post-rift intervals are generally under-explored.The basin configuration inherited by the Cretaceous early post-rift in the northern North Sea was set up by Permo-Triassic and Late Jurassic rifting. In the North Viking Graben this established considerable along-strike variability, resulting in a northern basin segment surrounded by steep slopes and faulted-bounded structural highs and a southern basin segment margined by slopes with noticeably gentler gradients. Associated with the Cretaceous post-rift is an overall transgressional trend, which drowned local source areas, resulting in prevalent carbonate and hemipelagic mudstone deposition in the basins. In the North Viking Graben, the uplifted Oseberg fault-block provided the sub-aerial clastic source area until it was submerged in the early Upper Cretaceous.The early post-rift infill of the North Viking Graben was divided into four key seismic stratigraphic units (K1, K2, K3 and K4) using an integration of seismic and well data. Inside this stratigraphic framework, the depositional systems within each K-unit were resolved from characteristic seismic facies, amplitude anomalies, relationship with adjacent reflections, and geomorphologies. In the northern basin segment, the early post-rift stratigraphy contains basin-floor fans, a channel complex and a shoreline-like geometry, whereas the southern basin segment is solely characterised by hemipelagic and carbonate deposition. This spatial variability indicates that one of the dominant controls on the development of the early post-rift depositional systems in the North Viking Graben was the inherited syn-rift fault-controlled topography. The steep slopes bounding the northern basin segment aided the delivery of sediment from the sub-aerial Oseberg source area to the graben whereas the submerged, gentle slopes in the southern basin segment were relatively sediment-starved.Long- and short-term changes in relative sea-level also heavily influenced the evolution of the early post-rift basin stratigraphy. Short-term relative sea-level fall allowed basin-floor fan emplacement whereas short-term relative sea-level stand-still favoured deposition of a channel complex. Deposition of the shoreface-like geometry is associated with a short-term relative sea-level rise. This temporal difference in the style and scale of the depositional systems is also interpreted to reflect the gradual denudation and drowning of the Oseberg source area. Regional short-term trangressive and anoxic events in the northern North Sea further influenced the early post-rift strata, resulting in the deposition of stratigraphic units that can be correlated across the North Sea. 相似文献
14.
Sedimentology and sequence stratigraphy of a transfer zone coarse-grained delta, Miocene Suez Rift, Egypt 总被引：4，自引：0，他引：4
This study focuses on Miocene sedimentation and stratigraphic evolution in a major transfer zone at the northern tip of the Thal Fault segment, Gulf of Suez. The succession generally shoals upwards from offshore mudstone containing pro-delta turbidites, into conglomeratic delta foresets and topsets, with sandstone-dominated shoreface facies coexisting laterally. Despite this upward shoaling, key stratal surfaces marking abrupt changes in relative sea-level allow the succession to be divided into four stratal units. The stacking pattern of the stratal units suggests an initial relative sea-level rise that generated a major marine flooding surface. A relative sea-level fall followed, resulting in widespread exposure and incision. During the ensuing relative sea-level rise a lowstand coarse-grained delta and coeval shoreface succession prograded several kilometres basinward. The stratigraphic development of the transfer zone delta is in marked contrast to that of aggradationally stacked deltas that occur near the centre of the Baba-Sidri fault segment, further south. At the transfer zone, low rates of subsidence and accommodation development coupled with a high sediment supply derived from a large fault tip drainage catchment have produced a strongly progradational delta subject to marked changes in relative sea-level. In the fault centre location, however, higher rates of accommodation development coupled with lower rates of sediment supply from footwall catchments have produced aggradationally stacked deltas. The results from this study have implications for sequence stratigraphic models and hydrocarbon exploration within extensional basins. 相似文献
15.
沉积物体积分配原理——高分辨率层序地层学的理论基础 总被引：119，自引：4，他引：115
基准面旋回期间沉积物以不同体积被分配到不同相域的过程及其伴随的可容纳空间的变化称为“沉积物体积分配” ,它反映了沉积过程响应系统遵循物质保存定律。沉积物体积分配在地层记录中的沉积学和地层学的响应表现为 :( 1)地层旋回的对称性随时间和空间的变化 ;( 2 )反映原始地貌要素保存程度的相分异作用 ;( 3)进积 /加积地层单元的叠加样式。这些沉积学与地层学属性无一不是高分辨率层序地层划分与对比的基础。根据沉积物体积分配原理 ,正确的年代地层对比应该是有时岩石与岩石、有时岩石与界面或界面与界面的对比 ,而不是等厚度对比和岩性地层对比。鄂尔多斯盆地上古生界海陆过渡相和渤海湾裂谷盆地东营组湖相沉积的地层对比说明了沉积物体积分配的过程及其在高分辨率地层划分和对比中的应用。 相似文献
16.
沉积盆地的层序和沉积充填结构及过程响应 总被引：13，自引：4，他引：9
现代层序地层学的理论发展,把沉积过程纳入到地质演化的时空框架中并与地球的多旋回或节律演化结合研究,形成了一套带有革命性的、在等时地层格架中研究沉积作用的新方法,成为了油气资源等沉积矿产预测勘探的重要工具。沉积盆地的沉积充填可划分出与各级沉积旋回相对应的层序地层单元。追踪对比由不整合面或不整合面及其对应的整合面为界的高级别层序地层单元建立的区域性等时地层格架,对盆地构造古地理再造和油气勘探战略性研究至关重要;追踪四、五级等低级别层序地层单元和体系域建立的高精度层序地层格架,可为重点区域或区带的沉积体系和储集体的沉积构成和分布等的解剖提供精细的地层对比基础。依据沉积基准面的变化,从层序内水进到水退的沉积旋回中可划分出正常水退沉积、强制性水退沉积、水进沉积及垂向加积等成因沉积类型。海相或湖相盆地中三级层序地层单元内均可较好地划分出低位、水进、高位及下降体系域。盆地构造作用、气候变化、海、湖平面升降过程对层序发育的控制作用及沉积响应研究,一直是层序地层学或沉积地质分析领域的研究热点。沉积盆地的层序地层序列演化是盆地地球动力学过程的总体响应。层序地层学把盆地古构造、古地理的变迁纳入到统一的地球演化系统中研究,形成了与区域地球演化史或盆地动力学演化相结合的重要研究领域。多旋回盆地或叠合盆地中多期次的构造变革导致了多个区域性不整合面所分隔的多个构造层序的叠加。注重构造—层序地层的结合分析,揭示盆地的层序地层序列与多期盆地构造作用的成因联系,是构造活动盆地或大型叠合盆地沉积地质演化和油气聚集规律研究的关键。盆地构造作用,如前陆盆地多期次的逆冲挠曲沉降和回弹隆起的构造作用、多幕裂陷过程、多期构造反转等与重要不整合及区域性沉积旋回或层序的形成密切相关;而由气候变化引起的海或湖平面变化是控制高频沉积旋回或低级别层序发育的主要因素。在构造活动盆地中,构造坡折带对沉积体系域和沉积相的发育分布具重要控制作用。 相似文献
17.
H. D. SINCLAIR 《Sedimentology》1993,40(5):955-978
High resolution stratigraphical analysis divides a rock succession into the basic genetic units of stratigraphy which are here termed small scale stratigraphical cycles. Each cycle records the sedimentological response to an episode of shallowing and deepening. Assuming that these changes in water depth reflect changes in the shoreline position, they can be considered as regressive/transgressive episodes. Each cycle comprises a regressive and transgressive facies tract which will be variably proportioned; in some examples a facies tract may only be represented by a hiatal surface of no deposition, erosion and/or bypass. In the Annot Sandstones of south-east France, variations in facies types, proportions and associations can be demonstrated both laterally and vertically through the succession. First, it is demonstrated that facies variations occur within regressive or transgressive facies tracts as a function of the stratigraphical stacking pattern of the cycles (i.e. landward, vertical or seaward stacked); this is termed ‘vertical facies differentiation’. Second, the proportions of facies tracts and their constituent facies types within an individual cycle vary between more landward and more seaward palaeogeographical locations; this is termed ‘lateral facies differentiation'. The upper Eocene/lower Oligocene Annot sandstones outcrop in the Maritime Alps of south-east France, within the thin skinned outer fold and thrust belt of the Alpine arc. The sandstones are well exposed in the area of the Col de la Cayolle on the north-west margin of the Argentera Massif, where lithostratigraphical correlations are possible over 3·5 km in a NNW/SSE direction, perpendicular to the edge of the depositional basin. Traditionally, these outcrops have been interpreted as deep marine turbidite lobe sediments; this study reflects a significant reinterpretation of this succession as having been deposited in a shallow marine environment. Seven sedimentary sections were measured through the succession, which is divided into 10 small scale stratigraphical cycles. These cycles are described in terms of eight facies which are separated into their transgressive or regressive facies tracts. In eight of the 10 cycles, the regressive facies tracts reflect the progradation of storm influenced braid deltas over shelf muds and silts. In two of the 10 cycles, the regressive facies tracts reflect barrier inlet and wash-over sands interfingering with back barrier deposits. These latter two cycles are located within landward stepping cycle sets; this is an example of vertical facies differentiation. Transgressive facies tracts locally reworked the upper surface of the regressive facies tract and also comprise barrier and back barrier deposits. The facies succession within each cycle varies according to its position with respect to the palaeoshoreline. The more landward portion of an individual cycle comprises a deltaic shoaling upward succession, culminating in coarse distributary channel conglomerates, overlain by a transgressive barrier/inlet system with extensive back barrier deposits. Beyond the delta front, the more seaward equivalent of individual cycles comprises an erosive base, with aggradational massive pebbly sandstones sitting directly upon offshore heterolithics; these sandstones are interpreted as hyperconcentrated fluvial efflux into the nearshore environment. This grades upward into offshore heterolithics and graded storm deposits representing the products of ravinement, which are then overlain by shelf mudstones. In summary, the more landward portions of cycles preserve predominantly regressive facies tracts, whereas the more seaward portions preserve aggradational to retrogradational strata of the transgressive facies tract; this is an example of lateral facies differentiation. 相似文献
18.
Cauvery Basin, a pericratonic rift basin along the Eastern Continental Margin of India, evolved during the breakup of the Eastern Gondwanaland. It exposes both syn-rift and later post-rift passive margin deposits ranging from Barremian to Miocene. The Karai Formation, upper Aptian-lower/middle (?) Turonian represents the oldest passive margin in the Cauvery Basin. It is bounded at both contacts by major sequence boundaries viz. the break-up unconformity and the Turonian tilt event. The present communication deals with the ichnology of the Karai Formation and its integration with sedimentary facies and biostratigraphy to interpret the sea level changes during deposition. A traverse between the villages Karai and Kulakkalnattam was studied in detail for this purpose. Based on the lithological position, characters and internal grain size trends, the Karai Formation is sub-divided into four informal lithologic units; the lower three units, constitute a lithostratigraphic unit known in literature as the Gypsiferous Clay Member, while the uppermost, corresponds to the Sandy Clay Member. At the base, clays of the Karai Formation unconformably onlap onto the Precambrian basement or the fluvial syn-rift deposits across the break-up unconformity. Upper Aptian to middle Cenomanian, units I and II showing the distal Cruziana ichnofacies, deepening of the basin and a retrogradational stacking pattern represent a transgressive system tract (TST). This long phase of transgression is attributed to continuous accommodation created by the post-breakup thermal subsidence. The upper part of unit II (middle Cenomanian) shows condensation, with its top representing the maximum flooding surface (MFS). Upper Cenomanian to lower/middle (?) Turonian, units III and IV characterised by a shift from the distal Cruziana to the Skolithos ichnofacies, an initial aggradational and later deltaic, progradational stacking pattern resulting from a fall in the relative sea level and filling up of accommodation space represent the highstand system tract (HST). A further fall in the relative sea level led to the exposure, incision and erosion of the Karai Formation over which the younger transgressive sequence of the Trichinopoly Group was deposited with an angular unconformity. 相似文献
19.
Although sequence stratigraphic concepts have been applied extensively to coarse-grained siliciclastic deposits in nearshore environments, high-resolution sequence stratigraphic analysis has not been widely applied to mudstone-dominated sedimentary successions deposited in more distal hemipelagic to pelagic settings. To examine how sequence stratigraphic frameworks can be derived from the facies variability of mudstone-dominated successions, the Tununk Shale Member of the Mancos Shale Formation in south-central Utah (USA) was examined in detail through a combination of sedimentological, stratigraphic and petrographic methods. The Tununk Shale accumulated on a storm-dominated shelf during the second-order Greenhorn sea-level cycle. During this eustatic event, the depositional environment of the Tununk Shale shifted laterally from distal middle shelf to outer shelf, then from an outer shelf to an inner shelf environment. At least 49 parasequences can be identified within the Tununk Shale. Each parasequence shows a coarsening-upward trend via upward increases in silt and sand content, thickness and lateral continuity of laminae/beds, and abundance of storm-generated sedimentary structures. Variations in bioturbation styles within parasequences are complex, although abrupt changes in bioturbation intensity or diversity commonly occur across parasequence boundaries (i.e. flooding surfaces). Due to changes in depositional environments, dominant sediment supply and bioturbation characteristics, parasequence styles in the Tununk Shale show considerable variability. Based on parasequence stacking patterns, eleven system tracts, four depositional sequences and key sequence stratigraphic surfaces can be identified. The high-resolution sequence stratigraphic framework of the Tununk Shale reveals a hierarchy of stratal cyclicity. Application of sequence stratigraphic concepts to this thick mudstone-dominated succession provides important insights into the underlying causes of heterogeneity in these rocks over multiple thickness scales (millimetre-scale to metre-scale). The detailed sedimentological characterization of parasequences, system tracts and depositional sequences in the Tununk Shale provides conceptual approaches that can aid the development of high-resolution sequence stratigraphic frameworks in other ancient shelf mudstone successions. 相似文献
20.
《Sedimentary Geology》2006,183(1-2):125-144
In the Mejillones Formation, a shallow-marine Pleistocene succession of northern Chile, the cyclic stratigraphic record is the result of the complex interaction of regional uplift, glacio-eustasy, local tectonics, sediment supply, and sedimentary processes. Stratal geometries, characteristics of sedimentary facies, and nature of sequence-bounding unconformities have been investigated to evaluate the influence of: (i) intrabasinal, short-term normal faulting on both along-strike variations in sequence architecture and genetic complexity of key stratal surfaces; and (ii) long-term regional uplift on sequence stacking pattern. The stratigraphic succession, dissected by small-displacement (few meters) normal faults striking obliquely with respect to the palaeo-shoreline trends, displays systematic variations in sequence architecture and the nature of bounding surfaces across them. Indeed, depending on position with respect to the fault plane, two basic types of internal organisation can be recognised in the examined shallow-marine, almost clastic-starved sequence. Within grabens it consists of a siliciclastic-rich transgressive systems tract (TST), which is bounded beneath by a transgressively modified, Glossifungites-demarcated sequence boundary (SB/RS), overlain by a mollusc-bearing falling-stage systems tract (FSST). The erosional downlap surface that separates the TST from the FSST is the regressive surface of marine erosion (RSME). On the footwall crests the combination of marine regressive erosion, during falls in relative sea-level, and uplift has resulted in complete removal of the sediments of the TST from these sites, leading to the formation of a tectonically enhanced basal unconformity composed of the RSME superimposed onto the previous SB/RS (SB/RS/RSME). The prominent lateral change in component units (systems tracts) and nature of bounding surfaces within the studied sequence is directly related to the presence of normal faults and indicates that fault activity had a major impact on the sequence stratigraphic evolution of the Mejillones Formation, enhancing subsidence within the grabens and promoting unconformities in the horsts.Overall, the Mejillones Formation records a long-term sea-level fall driven by the contemporaneous regional uplift, punctuated by repeated, high-frequency eustatic sea-level changes. The effect of this superimposition was that glacio-eustatic sequences were displaced progressively downward and basinward and stacked in a distinct downstepping, tectonically enhanced falling-stage sequence set, which reflects basin-wide loss in accommodation space. The sequence set is underlain by a composite RSME that becomes progressively younger basinward and is made up by the lateral and down-dip connection of a series of lower-rank sequence boundaries including hanging-wall SB/RSs and footwall SB/RS/RSMEs of successive sequences. 相似文献