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1.
D. Uli&#;ný 《Sedimentology》2001,48(3):599-628
Deposits of coarse‐grained, Gilbert‐type deltas showing varying degrees of reworking of foresets by basinal currents were identified in Middle Turonian to Early Coniacian sandstones of the Bohemian Cretaceous Basin. The progradation of the deltaic packages, earlier interpreted as large‐scale subaqueous dunes, shelf ridges or subaqueous fault‐scarp ‘accumulation terraces’, was controlled by high‐ and low‐frequency, relative sea‐level changes in a relatively slowly subsiding, intracontinental strike‐slip basin. End‐member types of the Bohemian Cretaceous coarse‐grained deltas are deep‐water deltas, characterized by thick (50–80 m) foreset packages with steep (10–30°) foresets, and shallow‐water deltas, which deposited thin (<15 m) packages with foresets typically between 4° and 10°. The differences in thickness and foreset slope angle were controlled predominantly by the accommodation available during progradation. The depositional regime of the deltas was governed by (i) the fluvial input of abundant sand bedload, with a minor proportion of gravel; (ii) gravity flows, most probably caused by liquefaction of the upper part of the unstable foreset slope; and (iii) migration of sandy bedforms on the foreset slopes. The bedform migration was driven by unidirectional currents of possible tidal origin. Individual foreset packages represent systems tracts, or parts of systems tracts, of depositional sequences. A variety of stacking patterns of high‐frequency sequences exists in the basin, caused by low‐frequency relative sea‐level changes as well as by local changes in sediment input. Because of generally low subsidence rates, fluvial or beach topset strata were not preserved in the cases studied. The absence of preserved fluvial facies, which has been one of the main arguments against the fluvio‐deltaic origin of the sandstone bodies, is explained by erosion of the topsets during transgression and their reworking into coarse‐grained lags of regional extent covering ravinement surfaces. 相似文献
2.
Sequence architecture and carbonate platform configuration (Late Cenomanian–Santonian), Sinai, Egypt
Abstract Relative sea‐level changes on the mixed carbonate–siliciclastic platform of Sinai are manifested in shifts of distinct facies belts (deep‐water facies, high‐energy subtidal, shallow subtidal, lagoon, shallow shoreface siliciclastics, supratidal) and are interpreted in terms of sequence stratigraphy. Eight sedimentary sequences are recognized for the Upper Cenomanian to Santonian. Their correlation along a north–south transect reveals distinct changes in lithofacies and progradation/retrogradation patterns within the individual systems tracts. The number and stratigraphy of the sequence boundaries of Sinai correlate well with those from adjacent areas. Patterns of increased subsidence are documented for the Central Sinai Basin since the Late Cenomanian by increased thickness of the stratal packages (post‐CeSin 7 HST, post‐TuSin 1 LST and HST, post‐TuSin 2 LST) and are balanced by varying accumulation rates. Based on new sedimentological and biostratigraphic data, large‐scale palaeogeographic maps and cross‐sections show the: (1) temporal and spatial evolution of the Central Sinai Basin, e.g. its latest Cenomanian initial formation, Lower Turonian deep‐water facies, Middle Turonian to Coniacian synsedimentary subsidence; (2) drowning of the Cenomanian platform coinciding with the latest Cenomanian to Early Turonian relative sea‐level rise; (3) re‐establishment of the platform in Middle–Late Turonian times; and (4) a Coniacian basin and swell morphology. 相似文献
3.
Tectonic, eustatic and environmental controls on mid-Cretaceous carbonate platform deposition, south-central Pyrenees, Spain 总被引：2，自引：0，他引：2
Cenomanian–Turonian strata of the south‐central Pyrenees in northern Spain contain three prograding carbonate sequences that record interactions among tectonics, sea level, environment and sediment fabric in controlling sequence development. Sequence UK‐1 (Lower to Upper Cenomanian) contains distinct lagoonal, back‐margin, margin, slope and basin facies, and was deposited on a broad, flat shelf adjacent to a deep basin. The lack of reef‐constructing organisms resulted in a gently dipping ramp morphology for the margin and slope. Sequence UK‐2 (Upper Cenomanian) contains similar shallow‐water facies belts, but syndepositional tectonic modification of the margin resulted in a steep slope and deposition of carbonate megabreccias. Sequence UK‐3 (Lower to Middle Turonian) records a shift from benthic to pelagic deposition, as the shallow platform was drowned in response to a eustatic sea‐level rise, coupled with increased organic productivity. Sequences UK‐1 to UK‐3 are subdivided into lowstand, transgressive and highstand systems tracts based on stratal geometries and facies distribution patterns. The same lithologies (e.g. megabreccias) commonly occur in more than one systems tract, indicating that: (1) the depositional system responded to more than just sea‐level fluctuations; and (2) similar processes occurred during different times throughout sequence development. These sequences illustrate the complexity of carbonate platform dynamics that influence sequence architecture. Rift tectonics and flexural subsidence played a major role in controlling the location of the platform margin, maintaining a steep slope gradient through syndepositional faulting, enhancing slope instability and erosion, and influencing depositional processes, stratal relationships and lithofacies distribution on the slope. Sea‐level variations (eustatic and relative) strongly influenced the timing of sequence and parasequence boundary formation, controlled changes in accommodation and promoted platform drowning (in conjunction with other factors). Physico‐chemical and climatic conditions were responsible for reducing carbonate production rates and inducing platform drowning. Finally, a mud‐rich sediment fabric affected platform morphology, growth geometries (aggradation vs. progradation) and facies distribution patterns. 相似文献
4.
The Early Miocene Bílina Palaeodelta consists of fluvio‐deltaic and lacustrine clastics deposited along the south‐eastern margin of the extensional Most Basin, part of the Eger Graben in north Bohemia (Czech Republic). The Bílina succession shows evidence of repeated advances of an axial deltaic system across a thick accumulation of organic material and clay in the hangingwall of an active fault. Exposures up to ca 4·5 km long in the Bílina open‐cast mine help bridge the gap between seismic scale and typical outcrop scale of observation and thus allow the relationships between small‐scale and basin‐scale stratal geometries to be evaluated. The Bílina Palaeodelta deposits include sand‐dominated, fluvial channel fills and heterolithic sheets interpreted as delta plain strata, sand‐dominated mouth‐bar wedges and heterolithic sheets of prodeltaic deposits, passing distally into lacustrine clays. The depositional environment is interpreted as a fluvial‐dominated, mixed‐load, lacustrine delta with a high degree of grain‐size segregation at the feeder‐channel mouths. On the largest temporal and spatial scales, variable tectonic subsidence controlled the overall advance and retreat of the delta system. The medium‐term transgressive‐regressive history was probably driven by episodes of increased subsidence rate. However, at this temporal scale, the architecture of the deltaic sequences (deltaic lobes and correlative lacustrine deposits) was strongly affected by: (i) compaction of underlying peat and clay which drove lateral offset stacking of medium‐term sequences; and (ii) growth of a fault‐propagation fold close to the active Bílina Fault. At the smallest scale, the geometries of individual mouth bars and groups of mouth bars (short‐term sequences) reflect the interaction among sediment loading, compaction and growth faulting that produced high‐frequency relative lake‐level fluctuations and created local accommodation at the delta front. 相似文献
5.
陆相断陷盆地层序形成动力学及层序地层模式 总被引：55，自引：0，他引：55
文中认为 :陆相断陷盆地层序形成的动力学机制源于全球构造事件导致的区域构造应力场、地幔隆升产生的岩石圈拉张伸展而导致的不同级别的幕式构造运动以及由构造、冰川消融作用和地球旋转而产生的气候旋回。基准面的变化是构造、气候的函数 ,对于地史时期的滨海盆地 ,基准面就是相对海平面。不同级别的基准面变化旋回形成不同级别的层序 ,表现为盆地的裂陷旋回期相当于海平面变化旋回的超周期组 ,形成构造层序 ;裂陷幕和气候的二级旋回相当于海平面旋回的超周期 ,形成层序组 ;幕式断陷作用和气候的三级旋回形成层序。断陷盆地一个典型层序形成的模式是 :由于湖水体积的有限性 ,一次断陷和掀斜运动就能产生构造坡折并使湖水体积再分配 ,湖水向主断层和构造坡折之间可容空间增大的区域流动 ,造成基准面下降 ,产生陆上暴露、下切水道、水下冲积扇、废弃型三角洲及扇三角洲构成低位域 (LST)。构造宁静期 ,在气候等因素的作用下 ,湖水将趋于恢复断陷前的位置 ,使基准面 (湖平面 )升高 ,形成湖浸和河流退积作用形成的破坏型三角洲 ,深湖、浊积扇及浅湖构成湖扩张体系域 (EST)。当湖平面达到最高并趋于稳定 ,由于断陷使流域地形变陡 ,大量碎屑物入湖形成以三角洲前积体为主的高位体系域 (HST)。叠加在三级基准? 相似文献
6.
ABSTRACT A three‐dimensional numerical model of sediment transport and deposition in coarse‐grained deltas is used to investigate the controls on depositional sequence variability in marine half‐graben extensional basins subject to eustatic sea‐level change. Using rates of sea‐level change, sediment supply and fault slip reported from active rift basins, the evolution of deltas located in three contrasting structural settings is documented: (1) footwall‐sourced deltas in high‐subsidence locations near the centre of a fault segment; (2) deltas fed by large drainage catchments at fault tips; and (3) deltas sourced from drainage catchments on the hangingwall dip slope. Differences in the three‐dimensional form and internal stratigraphy of the deltas result from variations in tilting of the hangingwall and the impact of border fault slip rates on accommodation development. Because subsidence rates near the centre of fault segments are greater than all but the fastest eustatic falls, footwall‐sourced deltas lack sequence boundaries and are characterized by stacked highstand systems tracts. High subsidence and steep bathymetry adjacent to the fault result in limited progradation. In contrast, the lower subsidence rate settings of the fault‐tip and hangingwall dip‐slope deltas mean that they are subject to relative sea‐level fall and associated fluvial incision and forced regression. Low gradients and tectonic tilting of the hangingwall influence the geometry of these deltas, with fault‐tip deltas preferentially prograding axially along the fault, creating elongate delta lobes. In contrast, broad, sheet‐like delta lobes characterize the hangingwall dip‐slope deltas. The model results suggest that different systems tracts may be coeval over length scales of several kilometres and that key stratal surfaces defining and subdividing depositional sequences may only be of local extent. Furthermore, the results highlight pitfalls in sequence‐stratigraphic interpretation and problems in interpreting controlling processes from the preserved stratigraphic product. 相似文献
7.
Many studies of foreland basins have recognized a hierarchical organization in the stacking of sequences deposited by axial‐deltaic and alluvial fan systems. The hierarchy is often explained in terms of the competing control of eustasy and pulsed tectonic subsidence and the different frequencies at which these processes operate. Unravelling the relative contributions of tectonic and eustatic controls on the sequence stacking pattern is a fundamental question in foreland basin analysis, yet this is difficult because of the lack of independent stratigraphic evidence. In this study, a three‐dimensional numerical model is presented, which aids in the interpretation of alluvial successions in foreland basins filled by transverse and axial depositional systems, under conditions of variable tectonism and eustatic sea‐level change. The tectono‐sedimentary model is capable of simulating the hierarchical stratigraphic response to both eustatic and tectonic forcing, and is of higher resolution than previous models of foreland basin filling. Numerical results indicate that the onset of tectonic activity is reflected by rapid retrogradation of both depositional systems and by widespread flooding and onlap of carbonate sediments. Syntectonic fluvial patterns on the axial‐deltaic plain are dominated by bifurcating channels, swiftly relocating in response to the general rise in relative sea level induced by flexural subsidence. The resulting surface morphology of the axial delta is convex upwards. Syntectonic eustatic sea‐level fluctuations result in parasequence‐scale packages of retrograding and prograding fan and delta sediments bounded by minor flooding surfaces and type 2 sequence boundaries. Incised channels are rare within the syntectonic parasequences and are formed only during phases of tectonic quiescence when eustatic falls are no longer compensated by the subsidence component in the rise in relative sea level. Suites of amalgamating, axial channels corresponding to multiple eustatic falls delineate the resulting type 1 unconformities. Coarse‐grained, incised‐channel fills are found in the zone between the alluvial fan fringes and the convex‐upward body of the axial delta, as the axial streams tend to migrate towards this zone of maximum accommodation. 相似文献
8.
运用钻井岩心、测井及层序地层学的有关理论、方法,对位于扬子地块西缘、四川攀枝花地区的宝鼎盆地的含煤岩系进行了层序地层学与聚煤作用研究。在主要含煤段大荞地组发育12个层序界面和11个四级层序,其中在40#煤层以上地层发育层序Ⅳ到层序Ⅺ等8个四级层序。伴随着宝鼎盆地由断陷盆地(大荞地组沉积时期)向大型拗陷盆地(宝鼎组沉积时期)演化,盆地基底沉降速率减小,可容空间增加速率降低,聚煤作用在垂向上先增强再减弱。断陷盆地发育早期,聚煤作用较弱;断陷盆地发展中期(层序Ⅳ-层序Ⅷ),主要煤层多发育于低位体系域、初始湖泛面附近和高位体系域中晚期,平面上聚煤中心位于可容空间增加速率中等的三角洲平原相带;至盆地发展晚期(层序Ⅸ-层序Ⅺ),主要煤层的发育位置逐渐向四级层序最大湖泛面靠近,平面上聚煤中心向可容空间增加速率最大的盆地沉积中心迁移。 相似文献
9.
The Cenomanian–Turonian carbonate-dominated lithofacies of Israel reflect a complex interplay between tectonics, sea-level change, and palaeoecology. Improved correlation based on revision of the bio- and chronostratigraphic framework has enabled the establishment of a sequence-stratigraphic model comprising five sequences delineated by four sequence boundaries, in the Late Cenomanian–Early Coniacian interval. The Late Cenomanian–Turonian succession begins with prograding, highstand, carbonate-platform deposits of the first sequence. Interruption of progradation and drowning of this platform took place within the Late Cenomanian guerangeri Zone (=the vibrayeanus Zone in Israel), resulting in a drowning unconformity which is regarded as a Type 3 sequence boundary (labelled CeUp). The drowning is attributed in part to extinctions in the rudist-dominated biofacies (e.g., Caprinidae), which led to reduced carbonate production and enhanced the impact of the sea-level rise. Similar drowning of Tethyan platforms around the C/T boundary has been linked to the establishment of coastal upwelling and consequent eutrophication. Outer ramp hemipelagic facies (Derorim and the Lower Ora formations) replaced the platform carbonates, thickening substantially southwards in the Eshet-Zenifim Basin of southern Israel. Along the ancient continental slope (Mediterranean coastal plain) evidence of this drowning is obscured by submarine erosion, while in central and northern Israel the drowned section is represented by condensation or a hiatus, reflecting an elevated, sediment-starved sea-floor. A carbonate platform dominated by rudistid shoals (‘Meleke’ Member; Shivta Formation) was re-established in the Judean hills and northern Negev during the middle part of the Turonian coloradoense Zone (local zone T4). Later, during kallesi Zone times (T7), the platform facies prograded southwards towards the Eshet-Zenifim intra-shelf basin. The drowning succession and overlying resurrected carbonate platform are topped in central and southern Israel by a pronounced Type 1 sequence boundary (Tu1) between the kallesi (T7) and ornatissimum (T8) zones (Middle Turonian). In central Israel and northern Negev the sequence boundary is overlain by lowstand deposits of the ‘Clastic Unit’ and by the transgressive and highstand inner to mid-ramp deposits of the Nezer and Upper Bina formations. In the southern Negev the sequence boundary is overlain by lowstand and transgressive systems tracts of mixed carbonates, siliciclastics, and localized evaporites (Upper Ora Formation), and then by mid to inner ramp carbonates of the Gerofit Formation. The latter represents a very high rate of accumulation, indicating rapid, continued subsidence balanced by platform growth. The Tu2 sequence boundary of the Late Turonian is expressed in the southern Negev by a shift from inner ramp carbonates of the Gerofit Formation to outer ramp chalky limestones of the Zihor Formation, indicating localized drowning. The succeeding Co1 sequence boundary again indicates localized drowning of the prograding highstand deposits of the Zihor Formation (‘Transition Zone’) overlain by Lower Coniacian transgressive deposits of the upper part of the Zihor Formation. All of these third-order sequences are expressed in southern Israel, where the rate of subsidence was in balance with sea-level fluctuations. In contrast, the Judean Hills and eastern Galilee areas have a more incomplete succession, characterized by hiatuses and condensation, because of reduced subsidence. More distal areas of continuous deep-water deposition in western Galilee and the coastal plain failed to record the Middle Turonian lowstand, while a longer term, second-order sequence spanning the entire Late Cenomanian–Early Coniacian interval, is present in the Carmel and Yirka Basin areas. 相似文献
10.
G. Aiello A. Ascione D. Barra R. Munno P. Petrosino E. Russo Ermolli F. Villani 《第四纪科学杂志》2007,22(3):233-245
The Pantano di San Gregorio Magno is a 4.7 km2 large tectono‐karstic basin located in the axial belt of the Southern Apennines, an area affected by intense seismicity. The basin was formed in the Middle Pleistocene and is presently undissected. It is filled by lacustrine sediments (clays, silts and pyroclastic sands) passing laterally into alluvial fan deposits. Geomorphological investigations were integrated with tephrostratigraphical, palynological and palaeoecological analyses of a 61 m thick core (not reaching the bedrock). The multiproxy analysis of the S. Gregorio Magno record shows that, over the last 200k yr, the basin hosted a freshwater lake with an oscillating level. Age constraints provided by the tephrostratigraphic record allowed estimation of the sedimentation rate, which varied strongly through time. Evolution of the basin resulted from the complex combination of tectonic subsidence, karst processes and changing amounts of sedimentary inputs. The latter was influenced by allogenic contributions related both to primary and reworked volcanoclastic inputs and was climate‐driven. The overall evidence, which indicates that in the long‐term the accumulation rate substantially counterbalanced the accommodation space created by faulting, suggests that the basin evolution was also modulated by changing subsidence rates. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
11.
克拉通边缘前陆盆地动力层序地层学 总被引：5，自引：1，他引：5
通过近几年对层序地层学的深入研究，尤其是对上扬子地台西缘中三叠世拉丁期末和晚三叠世卡尼期周缘前陆盆地层序地层学的研究，提出了动力层序地层学，将边缘前陆盆地由盆缘逆冲断块向克拉通稳定边缘分为Ａ区带和Ｂ区带。 相似文献
12.
Dirk Radies Harald Stollhofen Gregor Hollmann Peter Kukla 《International Journal of Earth Sciences》2005,94(5-6):863-875
The Late Permian/Early Triassic succession of the Central European Basin (CEB) was repeatedly affected by the tectonic pulses
associated with the earliest phases of Tethyan and Arctic–North Atlantic rifting. Effects of the differential tectonic subsidence
are particularly well recorded by unconformities, which form widespread sequence boundaries. Such unconformities are most
obvious in areas occupied by fault-controlled intra-basinal highs (swells). In that areas, stratigraphic loss may comprise
entire Lower and Middle Buntsandstein formations and in places remnant Middle Buntsandstein successions directly rest on Permian
strata. Analysis of 3D-seismic data and well logs combined with high-resolution sedimentological logging of drillcores at
the western margin of the Ems Trough (NW Germany) reveals details of synsedimentary tectonic control on sequence development.
Early Triassic extensional faulting of basement blocks provided stepwise addition of accommodation space for continental sequences
by growth faulting along north–south oriented fault zones blocks on the flanks of the East Netherlands High. This process
is most evident during the development of the Hardegsen Unconformity, which is characterised by an amalgamation of succeeding
unconformity surfaces in areas of structurally controlled intrabasinal highs. 相似文献
13.
Ramp sedimentation across a middle Albian,Arctic embayment: Influence of subsidence,eustasy and sediment supply on stratal architecture and facies distribution,Lower Cretaceous,Western Canada Foreland Basin 
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下载免费PDF全文 Robin A. Buckley A. Guy Plint Olivia A. Henderson Kathleen M. Vannelli 《Sedimentology》2016,63(3):699-742
Regional mapping of Middle Albian, shallow‐marine clastic strata over ca 100 000 km2 of the Western Canada Foreland Basin was undertaken to investigate the relationship between large‐scale stratal architecture and lithology. Results suggest that, over ca 5 Myr, stratal geometry and facies were dynamically linked to tectonic activity in the adjacent Cordillera. Higher frequency modulation of accommodation is most reasonably ascribed to eustasy. The Harmon and Cadotte alloformations were deposited at the southern end of an embayment of the Arctic Ocean. The Harmon alloformation, forming the lower part of the succession, constitutes a wedge of marine mudstone that thickens westward over 400 km from <5 m near the forebulge to >150 m in the foredeep. Constituent allomembers are also wedge‐shaped but lack distinct clinothems, a rollover point or downlapping geometry. Ubiquitous wave ripples indicate that the sea floor lay above storm wave base. Deposition took place on an extremely low‐gradient ramp, where accommodation was limited by effective wave base. Lobate, river‐dominated deltas fringed the southern margin of the basin. The largest deltas are stacked in the same area, suggesting protracted stability of the feeder river. A buried palaeo‐valley on the underlying sub‐Cretaceous unconformity may have influenced compaction and controlled river location for ca 3 Myr. Adjacent to the western Cordillera, a predominantly mudstone succession is interbedded with abundant storm beds of very fine‐grained sandstone and siltstone that reflect supply from the adjacent orogen. Bioturbation indices in the Harmon alloformation range from zero to six which reflects the influence of stressors related to river‐mouth proximity. Harmon alloformation mudstone grades abruptly upward into marine sandstone and conglomerate of the overlying Cadotte alloformation. The Cadotte is composed of three allomembers ‘CA’ to ‘CC’, that represent the deposits of prograding strandplains 200 × 300 km in extent. Allomembers ‘CA’ and ‘CB’ are strongly sandstone‐dominated, whereas allomember ‘CC’ contains abundant conglomerate in the west. The dominantly aggradational wedge of Harmon alloformation mudstone records flexural subsidence driven by active thickening in the adjacent orogen: the high accommodation rate trapped coarser clastic detritus close to the basin margin. In contrast, the tabular, highly progradational sandstone and conglomerate bodies of the Cadotte alloformation record a low subsidence rate, implying tectonic quiescence in the adjacent orogen. Erosional unloading of the orogen through Cadotte time steepened rivers to the extent that they delivered gravel to the shore. These observations support an ‘anti‐tectonic’ model of gravel supply proposed previously for the United States portion of the Cretaceous foreland basin. Because Cadotte allomembers do not thicken appreciably into the foredeep, accommodation changes that controlled these transgressive–regressive successions were probably of eustatic origin. 相似文献
14.
The Late Devonian‐Early Carboniferous Mansfield Basin is the northernmost structural sub‐basin of the Mt Howitt Province of east‐central Victoria. It is comprised predominantly of continental clastic sedimentary rocks, and is superimposed upon deformed Cambrian to Early Devonian marine sequences of the Palaeozoic Lachlan Fold Belt. This paper documents evidence for synsedimentary deformation during the early history of the Mansfield Basin, via sedimentological, structural and stratigraphic investigations. Repeating episodes of folding, erosion and sedimentation are demonstrated along the preserved western margins of Mansfield Basin, where fold structures within the lower sequences are truncated by intrabasinal syntectonic unconformities. A convergent successor basin setting (an intermontane setting adjacent to, or between major fault zones) is suggested for initial phases of basin deposition, with synsedimentary reverse faulting being responsible for source uplift and subsequent basin deformation. Palaeocurrents within conglomerate units indicate derivation from the west and are consistent with episodic thrusting along basin margin faults providing elevated source regions. Periods of tectonic quiescence are represented by finer grained meandering fluvial facies (indicative of lower regional topographic gradients) which display drainage patterns that appear not to have been influenced by bounding faults to the west. An up‐sequence increase in the textural and compositional maturity of basin sandstones and conglomerates is proposed to be a result of the incorporation of basin fill into ongoing basin deformation, with unstable metapelitic rocks being progressively winnowed from clast populations. Rather than resulting from Carboniferous (Kanimblan) reactivation of extensional structures, as is generally assumed, the deformation observed within the lower units of the Mansfield Basin is suggested here to be essentially syndepositional and at least Late Devonian in age. 相似文献
15.
Shi Xiaoying Lei Zhenyu Yin Jiarun China University of Geosciences Beijing 《《地质学报》英文版》1996,70(3):303-316
The Lower Jurassic is subdivided in ascending order into the Wulong, Kangdui and Yongjia Formations on the north slope of Mount Qomolangma, with a total thickness of 1362 m. They are thought to have been deposited respectively in the environments of the carbonate ramp fault-bounded basins and carbonate platform, with six sedimentary facies and six sub-facies. During the Early Jurassic, the Qomolangma area experienced strong faulting and subsidence, and was of a matured rift basin. The Lower Jurassic consists of eleven 3rd-order sequences, which can be grouped into three 2nd-order sequences and form a large transgressive-regressive cycle. The 3rd-order sequences and the corresponding sea-level changes recognized in the area can be correlated quite well with those set up in the western Tethys, and may have been caused by the eustatic fluctuations, while the 2nd-order sequences seem to be more closely related to the basement subsidence and the variation in sedimentary influx, indicating the evolution of th 相似文献
16.
D.P. Sen 《Sedimentary Geology》1981,30(4):291-310
During the Early Tertiary epoch a basin of deposition covered almost all the present Himalayan foot hill zone. Large quantities of detrital sediments were transported from the northern source area to the depositional basin. The rivers carrying the sediment load formed large delta complexes. In the area studied at least two such delta complexes, one around Kalka and the other around Nahan, were formed; of these the one around Kalka contains the greatest volume of sediments.
The recognition of the deltas is based on: (a) greater abundance of stream deposits than deposits of other environments; (b) lithologic criteria, particularly sedimentary structures, repetitive lithologic associations; (c) the general coarsening-upward nature of the sediments; (d) strong unimodal current direction; (e) the typical lenticular lithogenetic model, common in recent deltas.
The rocks of the Nahan Group are divisible into three formations at Kalka and two formations at Nahan where central formation did not develop. Himalayan tectonism has largely controlled both delta formation and stratigraphy.
The differential rates of sedimentation greatly influenced the rates of subsidence within the Nahan basin. The sediments of the Nahan Group are roughly bounded between two major phases of Himalayan uplift, namely Eocene and middle Miocene tectonic movements. The effects of intermittent tectonic pulses are well depicted in rocks of the Nahan Group. The intensity of the tectonism that controlled both the source-area rise and basin subsidence during deposition of the Nahan Group of sediments was nonuniform, both in vertical and lateral directions. Because of a generally higher rate of deposition compared to the rate of subsidence, the rocks of the Nahan group represent a normal regressive basin-filling sedimentation, forming thick detrital deposits due to progradation of younger deltas beyond the distal end of older deltas. 相似文献
17.
Upper Cretaceous platform carbonates of the Vocontian Basin (southeastern France) have been investigated in a cross-section from the proximal deposits exposed in the lower Rhône Valley to the distal part of the basin in the Southern Subalpine Ranges north of Nice. The stratigraphic interval studied in detail spans the uppermost Turonian and Coniacian.Palynofacies patterns were used to detect eustatic signals at a third-order scale and are the tool for correlation of proximal and distal platform deposits. The organic constituents observed in the studied samples have been grouped into a continental fraction, including higher plant debris (phytoclasts) and sporomorphs, and a marine fraction with dinoflagellate cysts, acritarchs, prasinophytes, and foraminiferal test linings. The main factors influencing the stratigraphic and spatial distribution of land-derived, allochthonous, and marine, relatively autochthonous, organic particles are the proximity of land, the organic productivity, the degree of biodegradation and the hydrodynamic conditions of the depositional system. Palynofacies parameters used for the sequence stratigraphic interpretation are: (1) the ratio of continental to marine constituents (CONT/MAR ratio); (2) the ratio of opaque to translucent phytoclasts (OP/TR ratio); (3) the phytoclast particle size and shape; and (4) the relative proportion and species diversity of marine plankton. Ternary diagrams illustrating significant proximality changes were used to decipher transgressive-regressive trends within the succession.High amounts of translucent phytoclasts and decreasing values of the CONT/MAR ratio occur during the phase of relative sea-level rise in the upper Turonian. The stratigraphic interval of maximum flooding around the Turonian/Coniacian boundary is marked by the highest abundance and species diversity of dinoflagellate cysts, and by high percentages of opaque, equidimensional particles within the phytoclast group. The OP/TR ratio is still high within the lower Coniacian representing the early highstand deposits, whereas the relative abundance of marine constituents is again decreasing. Sedimentary organic matter of the upper Coniacian is dominated by large, blade-shaped, mainly opaque phytoclasts, which are a characteristic palynofacies signature of late highstand deposits.The present study demonstrates the high potential of palynofacies analysis in high-resolution stratigraphy and correlation of sedimentary series of shallow epeiric seas. 相似文献
18.
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
19.
西北地区侏罗系的三角洲沉积 总被引：16，自引：0，他引：16
西北地区侏罗广泛发育扇三角洲,辫状河三角洲和曲流河三角洲相沉积,其中扇三角洲与陡倾的盆地边缘有关,盆地的沉降速率大于沉积率,沉积层序为加积型,并以沉积物重力流和无河道片流区同搬运的沉积短斩泄荷为特征,辫状河三角洲与不很陡的盆地边缘梯度有关,其沉积速率大于盆地的沉降速率,沉积层序为进积型,并以河道径流广泛发育为特征,曲流河三角洲与缓坡陷型构造边界有关,并具有以河流作用为主,湖泊作用的辅的特征,３种三 相似文献
20.
Sedimentary successions of non‐marine basins can be considered in terms of accommodation space and sedimentary supply changes. Changes in accommodation space controlling the large‐scale architecture of non‐marine basins are different in areas with high and low sedimentary supplies. Uplift of intrabasinal monoclines and anticlines reduced the available accommodation space, resulting in changes in both the geometry of the depositional sequences and the large‐scale architecture of fluvial, mudflat and shallow carbonate lacustrine deposits. Main drainage fluvial systems record areas with a high sedimentary supply, while mudflats and shallow fluctuating lakes represent areas that received less sediment. Two end members in the large‐scale architecture of main drainage fluvial system in the Almazán Basin (Spain) are: (i) ribbon‐shaped channel fills with low interconnectivity which pass laterally into mudflats dominated by mudstones and evaporites and into palustrine and shallow carbonate lacustrine deposits (mainly in the A2 depositional sequence); and (ii) sheet‐like channel fills with high interconnectivity laterally correlated with stacked calcretes in the marginal mudflats (in the upper part of A3). Ribbon‐shaped channel fills formed in areas of high accommodation space and sheet‐like channel fills formed in areas of reduced accommodation space. 相似文献