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1.
KELLY A. DILLIARD MICHAEL C. POPE MARIO CONIGLIO STEPHEN T. HASIOTIS BRUCE S. LIEBERMAN 《Sedimentology》2010,57(2):513-542
The lower part of the Early Cambrian Sekwi Formation in the Selwyn Basin of the Northwest Territories, Canada, is composed of two regional, unconformity‐bounded sequences, S0 and S1, which record the first widespread carbonate deposition during the initial Palaeozoic transgression onto the western margin of Laurentia. These Early Cambrian sequences are unique to the western North American Cordillera, representing the only record of primarily deep‐water deposition on a tectonically active, mixed carbonate–siliciclastic ramp during this period. More specifically, the geometry of the Sekwi ramp changed during deposition of S0 and S1, from a shallowly dipping homoclinal ramp during the S0 transgressive systems tract to a steeply dipping tectonically modified ramp during the early highstand systems tract of S0. The steeply dipping ramp profile of S0 was preserved into the early transgressive systems tract of S1. The Sekwi ramp returned to a gently sloping ramp during the late highstand systems tract of S1 and remained so throughout the remainder of Sekwi deposition. The evolving shape of the Sekwi ramp is attributed to syndepositional ‘down to the basin’ faulting during deposition of both S0 and S1 and is recorded by: (i) the westward thickening, irregular geometries of S0 and S1; (ii) geographical restriction of deep‐water facies (including sediment gravity flow deposits); (iii) the presence of large allochthonous blocks; and (iv) the clast composition of sediment gravity flow deposits. Sediment gravity flow deposits play an unusually important role in the sequence stratigraphic interpretation of the lower Sekwi Formation, as they delineate depositional packages, including the maximum flooding zone, the transitions between portions of systems tracts, and the inferred locations of syntectonic extensional faults. Syntectonic faults increased accommodation basinward of an extensive ooid‐shoal complex that developed along the Sekwi ramp crest, greatly influencing sequence geometry and initiating the downslope motion of sediment gravity flows. The syndepositional faulting probably was a continuation of extension that began during the latest Neoproterozoic rifting of western Laurentia. The composition of sediment gravity flow deposits track changing accommodation space on the lower Sekwi ramp and can be used to differentiate systems tracts that probably were related more to tectonism than eustasy. 相似文献
2.
The upper Millstone Grit strata (Yeadonian, Namurian) of North Wales have been studied using sedimentological facies analysis and sequence stratigraphy. These strata comprise two cyclothems, each containing prodelta shales (Holywell Shale) that pass gradationally upwards into delta‐front and delta‐plain deposits (Gwespyr Sandstone Formation). The deltas formed in shallow water (<100 m), were fluvial‐dominated, had elongate and/or sheet geometries and are assigned to highstand systems tracts. Two delta complexes with distinctive sandstone petrographies are identified: (1) a southerly derived, quartzose delta complex sourced locally from the Wales‐Brabant Massif, and (2) a feldspathic delta complex fed by a regional source(s) to the north and/or west. The feldspathic delta complex extended further south in the younger cyclothem. A multistorey braided‐fluvial complex (Aqueduct Grit, c. 25 m thick) is assigned to a lowstand systems tract, and occupies an incised valley that was eroded into the highstand feldspathic delta complex in the younger cyclothem. A candidate incised valley cut into the highstand feldspathic delta complex in the older cyclothem is also tentatively identified. Transgressive systems tracts are thin (<5 m) and contain condensed fossiliferous shales (marine bands). The high‐resolution sequence stratigraphic framework interpreted for North Wales can be readily traced northwards into the Central Province Basin (‘Pennine Basin’), supporting the notion that high‐frequency, high‐magnitude sea‐level changes were the dominant control on stratigraphic architecture. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
3.
通过对黔南坳陷和桂中坳陷的地层对比和分析,识别出了8种层序界面标志,共划分两个超(二级)层序SS1和SS2,并讨论了各体系域特征。在层序格架中对研究区内的储集体类型进行了总结,主要包括生物礁(滩)储集体、白云岩储集体和缝洞型储集体等3种类型。对层序格架中储集体的成因类型进行了总结归纳:有利的储集体主要有TST礁滩灰岩储集体、HST礁滩灰岩、白云岩储集体。 相似文献
4.
5.
Siliciclastic intervals in Lower Permian carbonate–siliciclastic cyclothems in western Kansas record climate control on facies progression, deposition and preservation. The 26 000 km2 study area comprises seven marine‐continental (carbonate–siliciclastic) cyclothems caused by glacioeustasy. Core data and a three‐dimensional geological model provide a detailed view of the sub‐surface on a gently sloping ramp. Siliciclastic intervals in the cyclothems are fine‐grained red beds with extensive pedogenic features, indicating a continental origin. Bed geometry (sheet‐like deposits that thin to the east), lateral grading, grain size (very fine‐grained sand to silt) and grain angularity (sub‐angular to angular) suggest that the sediment is loess sourced from the west, probably the Ancestral Rocky Mountains. There is a repeated record of glacial‐cycle‐scale, climate‐controlled cyclicity within siliciclastic intervals that has not been recognized previously. Aeolian silt grain size coarsens upward towards the middle, then fines upward in each siliciclastic interval. When sea‐level was high (interglacial) and carbonate production flourished, aeolian sedimentation nearly ceased, suggesting increased vegetation and rainfall at the source. As sea‐level fell, fine‐grained siliciclastic sediments were deposited under relatively dry, but seasonally wet conditions on an exposed ramp. Laterally graded coarser grained siliciclastic sediments with diagnostic fabrics indicate drier conditions with seasonal rainfall during a continued relative fall in sea‐level. The coarsest siliciclastic sediments were deposited during the lowest sea‐level and driest conditions, but still with sufficient seasonal moisture to allow vegetative cover and bioturbation. Subsequent upward fining is correlated with sedimentological indications of wetter conditions during relative sea‐level rise. Unlike common sequence stratigraphic models that relate siliciclastic sediment accumulation to base‐level rise, continental deposits were preserved because plants and pedogenesis stabilized aeolian sediment. The aggradational landscape formed by this process had several metres of positive relief that reduced accommodation for overlying marine carbonate strata. Thus, this mechanism for continental siliciclastic aggradation has a significant effect on sequence stratigraphic architecture. 相似文献
6.
RYAN M. PHELPS CHARLES KERANS SAM Z. SCOTT XAVIER JANSON JEROME A. BELLIAN 《Sedimentology》2008,55(6):1777-1813
This study highlights three‐dimensional variability of stratigraphic geometries in the ramp crest to basin of mixed carbonate–siliciclastic clinoforms in the Permian San Andres Formation. Standard field techniques and mapping using ground‐based lidar reveal a high degree of architectural complexity in channellized, scoured and mounded outer ramp stratigraphy. Development of these features was a function of location along the ramp profile and fluctuations in relative sea‐level. Deposition of coarse‐grained and fine‐grained turbidites in the distal outer ramp occurred through dilute and high‐density turbidity flows and was the result of highstand carbonate shedding within individual cycles. In this setting, high‐frequency cycles of relative sea‐level are interpreted on the basis of turbidite frequency, lateral extent and composition. Submarine siliciclastic sediment bypass during lowstand cycles resulted in variable degrees of siliciclastic preservation. Abundant siliciclastic material is preserved in the basin and distal outer ramp as point‐sourced lowstand wedges and line‐sourced early transgressive blankets. In mounded topography of the outer ramp, siliciclastic preservation is minimal to absent, and rare incised channels offer the best opportunity for recognition of a sequence boundary. Growth of mounded topography in the outer ramp began with scouring, followed by a combination of bioherm construction, fusulinid mound construction and isopachous draping. Intermound areas were then filled with sediment and continued mound growth was prevented by an accommodation limit. Mound growth was independent of high‐frequency cycles in relative sea‐level but was dependent on available accommodation dictated by low‐frequency cyclicity. Low‐angle ramp clinoforms with mounded topography in the outer ramp developed during the transgressive part of a composite sequence. Mound growth terminated as the ramp transformed into a shelf with oblique clinoform geometries during the highstand of the composite sequence. This example represents a ramp‐to‐shelf transition that is the result of forcing by relative sea‐level fluctuations rather than ecologic or tectonic controls. 相似文献
7.
塔中东部地区发育上奥陶统良里塔格组礁滩相碳酸盐岩是油气产出的主力产区。为了揭示层序地层格架特征及其内部沉积微地貌特征对礁滩体储层的控制机理,本文通过对岩石学、沉积微相、古生物、测井相研究,建立了上奥陶统良里塔格组高频层序地层格架,可划分为11个四级层序和多个五级层序。研究区良三段—良二段以高位体系域垂向持续加积作用为主,是礁(丘)、滩组合镶边沉积的主要发育期,一个四级层序内可发育一个至多个礁滩体沉积微地貌旋回,礁型微地貌发育规模及厚度受海平面升降次级旋回和构造沉降控制。通过对良三段—良二段高位体系域成岩组构和成岩环境分析,认为受同生岩溶作用所形成的大气成岩透镜体主要发育在高频层序向上变浅旋回的顶部和微地貌高处。同一层序内沉积微地貌隆起和海平面相对升降变化所控制的暴露作用,以及同生期大气淡水溶蚀、淋滤作用是控制台缘礁滩体优质储层发育以及层位性和区域差异性的关键因素。集中揭示高频层序格架内微地貌特征及其对礁滩体储层的控制机理,有效指导了塔中东部地区奥陶系礁滩型油气藏勘探开发。 相似文献
8.
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
9.
EBERHARD GISCHLER ROBERT N. GINSBURG JENS O. HERRLE SACHINDRA PRASAD 《Sedimentology》2010,57(4):1049-1068
The Belize barrier and atoll reefs represent one of the largest reef structures in the Atlantic Ocean. The southern shelf of Belize is a classic location of a modern mixed carbonate–siliciclastic system. Whereas knowledge of the Holocene deposits in the area is extensive, data on the Pleistocene system are fragmentary. Open questions include: (i) the nature of the reef foundations (carbonate versus siliciclastics); (ii) the ages of the deposits including the initiation of the barrier reef; and (iii) the response of the mixed system to sea‐level fluctuations. The results of a study of borings on the southern Belize shelf are presented here. Six, up to 105 m long borings were made to better understand the history of this important mixed system. Uranium‐series dating in the Pleistocene was not possible because of diagenetic alteration; however, lithostratigraphy, strontium isotopes and calcareous nannofossil biostratigraphy were used to constrain stratigraphic ages. Results support the contention that the Quaternary development in Belize was quite similar to that of other major barrier reefs such as the Florida Reef Tract and, further afield, the Great Barrier and the New Caledonian Barrier Reefs. All of these barrier reefs are mixed carbonate–siliciclastic systems and significant reef growth only began after the onset of high‐amplitude, eccentricity‐controlled sea‐level changes and as late as during the exceptionally long and warm marine isotope stage 11, some 400 ka. In Belize, Early Pleistocene sections at bases of borings include mollusc‐rich wackestones, rare coral packstones and marls, which were deposited under low to moderate energy conditions in a ramp setting before ca 900 ka, during the high sea‐levels of marine isotope stage 25 and possibly earlier (marine isotope stage 31 or 37). The Belize shelf was subaerially exposed for most of the mid‐Pleistocene and was dominated by siliciclastic sedimentation, possibly during marine isotope stages 24 to 12 when highstands were comparatively low. Continuous reefs at the shelf margin were developing during highstands. In the Late Pleistocene, beginning with the long and high highstand of marine isotope stage 11 (some 400 ka), the southern shelf was flooded entirely and carbonates started to dominate once more. Reefs developed on top of siliciclastic deposits on the shelf. A continuous barrier reef came into existence and largely developed on top of carbonates at the shelf margin. During Late Pleistocene lowstands, siliciclastics presumably no longer reached the shelf margin because of the topographic high of the barrier reef platform. The Quaternary Belize example may serve as a model for reconstructing ancient mixed systems in icehouse worlds, however, any extrapolations are limited by the fact that fast‐growing Scleractinian reef‐builders had not yet evolved in the Palaeozoic. 相似文献
10.
在与海平面变化存在联系的近滨线河流相地层中,源于海岸碎屑沉积体系的层序地层学概念得到了较好的应用,从而在河流相地层中产生了低水位体系域(LST)、与海侵体系域类似的水进体系域(TST)及高水位体系域(HST)等常规体系域下的河流相层序地层划分方案。由于源于海岸沉积体系的早期体系域划分存在着概念体系的不协调,故常规体系域划分在河流相层序中的使用也就存在着概念体系的不协调。非常规体系域(低可容纳空间体系域,LAST;高可容纳空间体系域,HAST)的提出可避免这种概念体系的不协调,并为研究复杂的河流沉积过程和提取地层记录规律提供重要的线索和思路。 相似文献
11.
扬子地台西南缘早三叠世层序地层格架 总被引：7，自引：0，他引：7
扬子地台西南缘早三叠世地层被划分为4个沉积层序。通过综合研究已取得的牙形石生物地层资料,与Haq等人提出的三叠纪牙形石生物时带进行了对比,初步定出了各沉积层序及体系域的界面年龄(层序1底界年龄251Ma;层序2底界年龄245.2Ma;层序3底界年龄243Ma;层序4底界年龄240.5Ma,顶界年龄239.4Ma),从而建立了区内分辨率较高的早三叠世地层格架。格架中层序组合特征在碳酸盐岩台地边缘显示得非常清楚,其中,层序1-层序2高水位体系域的台地边缘依次向陆后退,呈退积或超覆(overlap)型组合关系;层序3-层序4高水位体系域的台地边缘则依次向海推进,呈进积或退覆(offlap)型组合关系。这种组合特征主要受沉积盆地的构造沉降及2级海平面升降亚旋回的海面变化的控制,构造沉降加速和海面上升期形成的层序呈退积型组合关系;构造沉降平缓及海面下降期形成的层序呈进积型组合关系。此外,还研究了斜坡地带(贵阳改毛)层序1-层序3底部的碳氧同位素组成变化规律:海侵体系域-高水位体系域碳、氧同位素组成变化不大,δ13C主要为正值,但在高水位体系域顶部明显负向偏移;低水位体系域碳、氧同位素组成变化剧烈,且均为负值。这为地层划分提供了地球化学方面的依据。 相似文献
12.
FABRIZIO BERRA 《Sedimentology》2007,54(4):721-735
In the Concarena‐Pizzo Camino Massif (Lombardy Basin, Southern Alps, Italy) the lateral transition from Ladinian‐Carnian carbonate platforms to coeval intraplatform basins is preserved. The succession records the sedimentological evidence of a sea‐level fall on a flat‐topped platform with a narrow marginal reef rim and its effects in the adjacent deeper‐water basin. Repeated high‐frequency exposures of the platform top are recorded by a peritidal–supratidal succession that overlies subtidal inner platform facies of the former highstand system tract (HST). On the slope and in the basin, the sea‐level fall is recorded by a few metre thick succession of bioclastic packstones. These facies directly lie on coarse clinostratified breccia bodies (slope facies of the former HST) or on resedimented, well‐bedded, dark laminated limestones (basinal facies of the HST). This facies distribution indicates that during the sea‐level fall carbonate production on the platform top decreased rapidly and that sedimentation in the basin was mainly represented by condensed facies. Microfacies record an enrichment, during low stand, in pelagic biota (packstones with radiolarians and spiculae), whereas the occurrence of platform‐derived, shallow‐water materials is limited to thin lenses of reworked and micritized Fe‐rich oolites and bioclasts (mainly pelecypods and echinoderms). The facies association in the Concarena‐Pizzo Camino Massif demonstrates that a highly‐productive carbonate factory was almost completely turned off during the emergence of the platform top at a sequence boundary, leading to low‐stand starvation in the basin. The reconstruction of the stratigraphic evolution of the Concarena‐Pizzo Camino carbonate platform therefore represents a significant case history for the study of the behaviour of ancient carbonate systems during a fall in sea‐level, independent of its origin (eustatic or tectonic). 相似文献
13.
雪峰古陆边缘沅陵地区的上石炭统岩性特殊,以灰岩为主平白云质灰岩、砾屑灰岩与砾岩、砂岩相互成层,交替出现,因此,相对海平面升降变化在这种类型沉积中表现明显,利用层序地层的研究。上石炭统为１个三级层序,底部以Ｉ型层序与震旦系留茶坡组硅质岩接触;顶部仍以Ｉ型层序边界与下二叠统黔阳组成邻。包括低水位体系域、海进体系域和高水位体系域;依据准层序的叠是分为两个准层序组,即海进体系域和高水位体系域。 相似文献
14.
Fringing reef growth on a terrigenous mud foundation, Fantome Island, central Great Barrier reef, Australia 总被引：2，自引：0，他引：2
The leeward fringing reef at Fantome Island (central Great Barrier Reef province) is a carbonate body which has developed under the influence of terrigenous sedimentation. The reef flat is up to 1000 m wide and is surfaced by mobile sand and gravel, with almost all live corals restricted to the seaward rim. The reef slope has coral columns and heads on the upper part, but below 5 m water depth it is a muddy substrate with scattered mounds of branching corals. Three high recovery cores show the reef is up to 10 m thick and developed over a gently sloping terrace of weathered Pleistocene alluvium. Three post-glacial stratigraphic units are recognised: (1) carbonate reef top unit of coral rudstone and framestone including Sinularia spiculite; (2) lower slope unit of coral floatstone in a terrigenous muddy matrix; and (3) transgressive basal unit of skeletal arkosic sand. The acid insoluble content of matrix and of individual corals increases downwards. Coral growth rates decrease downwards, reflecting slower growth in muddier environments. Radiocarbon dating shows that the reef prograded seaward at almost stable sea level. An average vertical accumulation rate of 6.7 mm yr-1 is indicated. Two age reversals are interpreted as material transported by storms or by erosion in response to a late Holocene sea-level fall. The carbonate reef top unit has developed adjacent to, and is environmentally compatible with a muddy terrigenous, lower slope unit. Terrigenous influx has not changed during the Holocene, and terrigenous content of sediments is controlled by deposition on the reef slope of fine sediment winnowed from the reef flat and concentration of coarse sediment in the transgressive basal sheet. 相似文献
15.
A. Van Heeswijck 《Australian Journal of Earth Sciences》2013,60(3):417-426
Upper Carboniferous to Lower Permian sedimentary rocks extend along the periphery of the northern Sydney Basin, a sub‐basin of the Sydney‐Gunnedah‐Bowen Basin complex. The basin contains basal basalts and volcanic sediments deposited in a nascent rift zone. This rift zone was created through crustal thinning during trench rollback on the eastern edge of the New England Orogen. Thermal subsidence created accommodation for predominantly marine Dalwood Group sediments. Clastic sedimentation then occurred in the Maitland‐Cessnock‐Greta Coalfield and Cranky Corner Basin during the Early Permian. This occurred on a broad shelf undergoing renewed thermal subsidence on the margin of a rift flank of the Tamworth Belt of the southern New England Orogen. Braidplain fans prograded or aggraded in two depositional sequences. The first sequence commences near the top of the Farley Formation and includes part of the Greta Coal Measures, while the second sequence includes the majority of the Greta Coal Measures and basal Branxton Formation. Thin, areally restricted mires formed during interludes in a high sedimentation regime in the lowstand systems tracts. As base‐level rose, areally extensive mires developed on the transgressive surface of both sequences. A paludal to estuarine facies changed to a shallow‐marine facies as the braidplain was transgressed. The transgressive systems tracts continued to develop with rising relative sea‐level. Renewed uplift in the hinterland resulted in the erosion of part of the transgressive systems tract and all of the highstand systems tract of the lower sequence. In the upper sequence a reduction in relative sea‐level rise saw the development of a deltaic to nearshore shelf highstand systems tract. Extensional dynamics caused a fall in relative base‐level and the development of a sequence boundary in the Branxton Formation. Finally, renewed thermal subsidence created accommodation for the overlying, predominantly marine Maitland Group. 相似文献
16.
华北石炭-二叠纪层序地层格架及其特征 总被引：18，自引：3，他引：15
华北石炭二叠纪沉积建造由两部分组成,下部为碳酸盐岩与硅质碎屑岩构成的含煤建造,上部为硅质碎屑岩红色建造。根据不整合面及其它识别层序界面的标志,该沉积建造可划分为５个沉积层序。ＤＳ１、ＤＳ２、ＤＳ３层序属陆表海型层序,其底界面为Ⅰｅ型层序界面,层序内仅发育海侵体系域和高位体系域;ＤＳ４层序为过渡型层序,由低位体系域、海侵体系域和高位体系域构成;ＤＳ５层序为湖泊型层序,包括低水位体系域、水进体系域和高位体系域。盆地充填超层序（ＤＳ１-ＤＳ５）的发育受控于全球二级相对海平面变化,而沉积层序的发育则与区域性造山作用引起的三级海平面变化有关。 相似文献
17.
Well‐cuttings, wireline logs and limited core and outcrop data were used to generate a regional, three‐dimensional sequence framework for Upper Mississippian (Chesterian), Greenbrier Group carbonates in the Appalachian foreland basin, West Virginia, USA. The resulting maps were used to document the stratigraphic response of the basin to tectonics and to glacio‐eustasy during the transition into ice‐house conditions. The ramp facies include inner ramp red beds and aeolianites, lagoonal muddy carbonates, mid‐ramp ooid and skeletal grainstone shoal complexes, and outer ramp wackestone–mudstone, that grades downslope into laminated silty lime mudstone. The facies make up fourth‐order sequences, a few metres to over 90 m (300 ft) thick. The sequences are bounded along the ramp margin by lowstand sandstones and calcareous siltstones. On the ramp, sequence boundaries are overlain by thin transgressive siliciclastics and aeolianites, and only a few are calichified. Maximum flooding surfaces on the outer ramp lie beneath deeper water facies that overlie lowstand to transgressive siliciclastic or carbonate units. On the shallow ramp, maximum flooding surfaces overlie siliciclastic‐prone transgressive systems tracts, that are overlain by highstand carbonates with significant grainstone units interlayered with lagoonal lime mudstones. The fourth‐order sequences are the major mappable subsurface units; they are bundled into weak composite sequences which are bounded by red beds. In spite of differential subsidence rates across the foreland basin (1 to 3 cm/k.y. up to 25 cm/k.y.), eustatic sea‐level changes controlled regional sequence development. Thrust‐load induced differential subsidence of fault‐blocks, coupled with in‐plane stress, controlled the rapid basinward thickening of the depositional wedge, whose thickness and facies were influenced by subtle structures such as arches trending at high angles as well as parallel to the margin. 相似文献
18.
黔中隆起及外围南华-留纪层序地层特征 总被引：8，自引：1，他引：7
以黔中地区层序地层研究为基础,并与三都盆区层序地层对比。根据不整合界面、地层结构及地层的堆叠型式等特征,将黔中隆起及外围地区的南华-志留纪地层划分为14个层序,并阐述了各层序及体系域的发育特征。在此基础上,建立了南华-志留纪的岩石地层格架及相对海平面变化曲线。研究区层序地层的特点是：在浅水陆架区,大多数层序由海侵体系域和高水位体系域构成,并且高水位体系域的厚度常大于海侵体系域的厚度;层序所反映的海平面升降变化,在层序的下部表现较剧,常快速上升。通过层序界面的对比研究,界面基本性质进一步得到明确,使地层格架更趋真实。如黔中、黔北南沱组与澄江组的接触关系性质,从盆地区海侵体系域一高水位体系域及层序界面的延伸对比来看,黔中地区缺失这两个体系域,证明这里南沱组与澄江组之间为假整合接触。 相似文献
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20.
Yasser SALAMA Michael GRAMMER Shaban SABER Soheir EL-SHAZLY Gouda ABDEL-GAWAD 《《地质学报》英文版》2018,92(1):286-310
The Lower Cretaceous sections in northern Sinai are composed of the Risan Aneiza (upper
Barremian-middle Albian) and the Halal (middle Albian-lower Cenomanian) formations. The facies
reflect subtle paleobathymetry from inner to outer ramp facies. The inner ramp facies are peritidal,
protected to open marine lagoons, shoals and rudist biostrome facies. The inner ramp facies grade
northward into outer ramp deposits. The upper Barremian-lower Cenomanian succession is subdivided
into nine depositional sequences correlated with those recognized in the neighbouring Tethyan areas.
These sequences are subdivided into 19 medium-scale sequences based on the facies evolution, the
recorded hardgrounds and flooding surfaces, interpreted as the result of eustatic sea level changes and
local tectonic activities of the early Syrian Arc rifting stage. Each sequence contains a lower
retrogradational parasequence set that constituted the transgressive systems tracts and an upper
progradational parasequence set that formed the highstand systems tracts. Nine rudist levels are
recorded in the upper Barremian through lower Cenomanian succession at Gabal Raghawi. At Gabal
Yelleg two rudist levels are found in the Albian. The rudist levels are associated with the highstand
systems tract deposits because of the suitability of the trophic conditions in the rudist-dominated ramp. 相似文献