共查询到20条相似文献，搜索用时 31 毫秒
1.
2.
IVOR A. J. MacCARTHY 《Sedimentology》1987,34(3):389-422
This paper describes the sedimentation style associated with the basal Carboniferous transgression in southern Ireland and the influence which this event had on the palaeogeography of the region. The transgression as marked by the base of the Carboniferous succession is shown to represent one of several genetically related transgressive pulses which commenced during the Late Devonian. At this time an east-west trending graben, the South Munster Basin, developed in southern Ireland. This was initially a non-marine depositional site in which sediment was derived from the north and west. Subsidence and eustatic sea-level rise resulted in a marine transgression which proceeded in a rhythmic style resulting in a number of transgressive-stillstand pulses. The first transgressive pulse (T1) advanced in a westerly direction along the basin axis resulting in the development of an epicontinental-like sea. The shoreline remained essentially static along the northern basin margin initially until a second transgressive pulse (T2) resulted in expansion of the marine area. The latter proceeded by gradual northward erosive advance of a barred coastal area as far as the northern basin margin where the stability of the bounding platform halted its progress. Erosion of the barrier shoreface was insufficient to destroy all the backbarrier lagoonal deposits which are preserved as a thin transgressive diachronous unit which grades northwards to a coastal alluvial plain. Immediately preceding the basal Carboniferous transgression (T3), a shallow, wave-dominated, storm-influenced shelf sea occupied the basinal area. Two sublittoral sand bar complexes developed on the shelf under the influence of shore-parallel current regimes, apparently derived from source areas located on either side of the epicontinental sea The basal Carboniferous transgression took place in two pulses. The first (T3a) resulted in a rapid reduction in sand supply to the shelf and deposition of clay. The barrier shoreline responded by erosively retreating across the lagoon, leaving a transgressive lag in its wake. Its northwards advance was, however, limited due to the relative stability of the northern platform. Sand supply to the shelf was completely terminated in the second pulse (T3b) and the barrier rapidly migrated erosively across the northern platform for a considerable distance such that the coastal plain is overlain by a thin transgressive lag. This transgressive phase was immediately followed by shoreline stillstand and progressive shallowing of the shelf. An open sandy shelf developed on which offshore sand bars accumulated under a storm and wave dominated regime. Clay deposition continued in the deeper part of the basinal area but was eventually terminated as the shelf sands prograded centripetally into the basin. The main factor that controlled the style of the overall transgression was an interplay between eustatic sea level rise and basin subsidence. The rate of relative sea-level rise together with the effect of differential subsidence and fluvial input from the north appear to have diminished with time. The rate at which successive transgressive pulses advanced northwards shows an overall progressive increase. 相似文献
3.
《Journal of Asian Earth Sciences》1999,17(3):369-393
Neogene strata of the northern part of the Pegu (Bago) Yoma Range, Central Myanmar, contain a series of shallow marine clastic sediments with stratigraphic ages ranging from the Early to Late Miocene. The studied succession (around 750 m thick) is composed of three major stratigraphic units deposited during a major regression and four major transgressive cycles in the Early to Late Miocene. The transgressive deposits consist of elongate sand-bars and broad sand-sheets that pass headward into mixed-flats of tidal environments. Marine flooding in transgressive deposits is associated with coquina beds and allochthonous coral-bearing sandy limestone bands. Major marine regressions are associated with lowstand progradation of thick estuary point-bars passing up into upper sand-flat sand bodies encased within the tidal flat sequences and lower shoreface deposits with local unconformities. The succession initially formed in a large scale incised-valley system, and was later interrupted by two major marine transgressions in the generally regressive or basinward-stepping stratigraphic sequences. Successive sandbodies were formed during a sea-level lowstand and early stage of the subsequent relative rise of sea level in a tide-dominated estuary system in the eastern part of the Central Myanmar Tertiary Basin during Early to Late Miocene times. 相似文献
4.
Lithological evidence, benthic foraminiferal census counts, and X-ray fluorescence (XRF) scanner-derived elemental data were integrated with planktonic foraminiferal biostratigraphy and bulk carbonate stable isotopes to retrace the Turonian to early Campanian paleoenvironmental evolution and sea-level history of the Tarfaya Atlantic coastal basin (SW Morocco). The lower Turonian is characterized by laminated organic-rich deposits, which contain impoverished benthic foraminiferal assemblages, reflecting impingement of the oxygen minimum zone on the shelf during a sea-level highstand. This highstand level is correlated to the global transgressive pulse above the sequence boundary Tu1. The appearance of low-oxygen tolerant benthic foraminiferal assemblages dominated by Gavelinella sp. in the middle to upper Turonian indicates an improvement in bottom water oxygenation, probably linked to offshore retraction of the oxygen minimum zone during a regressive phase. This interval is marked by major regressive events expressed by a series of erosional truncations associated with the prominent sequence boundaries Tu3 and/or Tu4. Dysoxic–anoxic conditions recorded in the upper Santonian of the Tarfaya Basin coincide with the eustatic sea-level rise prior to Sa3 sequence boundary. The lower Campanian transgression, only recorded in the southern part of the Tarfaya Basin, coincided with substantial deepening, enhanced accumulation of fine-grained clay-rich hemipelagic sediments and improved oxygenation at the seafloor (highest diversity and abundance of benthic foraminiferal assemblages). Stable isotope data from bulk carbonates are tentatively correlated to the English Chalk carbon isotope reference curve, in particular the Hitch Wood Event in the upper Turonian, the Navigation Event in the lower Coniacian, the Horseshoe Bay Event in the Santonian and the Santonian/Campanian Boundary Event. 相似文献
5.
The Eocene Trihueco Formation is one of the best exposed successions of the Arauco Basin in Chile. It represents a period of marine regression and transgression of second-order duration, during which barrier island complexes developed on a muddy shelf. The strata are arranged in classical shoaling-upward parasequences of shoreface and beach facies capped by coal-bearing, back-barrier lagoon deposits. These fourth-order cycles are superimposed upon third-order cycles which caused landward and seaward shifts of the coastal facies belts. The final, punctuated rise in sea level is represented by shelf mudrocks with transgressive incised shoreface sandstones. Relative sea-level oscillations as revealed in the stratigraphy of the Trihueco Formation show a reasonable correlation with published Eocene eustatic curves. 相似文献
6.
首次对华北板块东部早古生代克拉通边缘盆地的碳酸盐地层进行层序地层学剖析,认为从寒武纪至早奥陶世加积、侧积的碳酸盐层序主要受海平面升降所制约,为历时约110 Ma的一个海进—海退旋回,是与全球海平面升降同步的超周期(二级旋回,P.R.Vail,1978)。而且海面升高与海侵同步,其间被Ⅰ、Ⅱ型层序界面不整合分隔为四个层序。海面升降模式是缓慢的海进,快速的海退,在主体海退过程中层序界面及海面降低控制着蒸发岩(石膏)矿床的形成。对长期争议的“三山子”白云岩的成因问题提出了新认识:“三山子”白云岩系海面区际性下降过程中,淡水渗流作用下形成的准同生交代白云岩,并随海面向北退却而使白云岩化向北推移且层位升高,是穿时性的“淡水透镜体”的向盆迁移,是区际性层序界面不整合的重要标志。 相似文献
7.
The Upper Oligocene–Lower Miocene succession in eastern Jylland can be subdivided into three sequences (A–C from older to younger) deposited on and around the Ringkøbing-Fyn High. The development of the sequences reflects a complex interaction between eustatic sea-level changes, physiography and variable sediment supply. Superimposed on this, frequent storms promoted longshore sediment transport and the development of spit systems adjacent to structural highs. As a consequence, sequence boundaries and flooding surfaces are not always expressed as portrayed in conventional sequence models; sequence boundaries or flooding surfaces may only be marked by subtle changes in depositional environment that can only be revealed by careful integration of sedimentological observations with palynological data. The influence of the topography resulted in the development of brackish water basins that were sufficiently large to permit the deposition of hummocky cross-stratified sands with muds. These deposits are overlain by clean hummocky and swaley cross-stratified sands that were deposited in a fully marine, high-energy environment. This evolution from mud-rich, storm-influenced sediments to sand-dominated shoreface sediments resulted from a rise in sea level and was not the result of shoreface progradation and downstepping during a sea level fall. In addition to the topographic control on sequence development, sediment supply to the study area changed significantly during the deposition of the three sequences. Initially the basin was sediment-starved, favouring the formation of glaucony-rich sediments. The sediment input gradually increased and the influence of structural highs and lows became less significant with time. Consequently, both sequence boundaries and flooding surfaces are characterized by more conventional features in the younger part of the succession, where a basinward displacement of the shoreline resulted in thick lowstand delta deposits. 相似文献
8.
Ian Shennan 《第四纪科学杂志》1986,1(2):155-179
Stratigraphic, micropalaeontologic and radiocarbon data show that since c. 6500 BP the Fenland has been influenced by 7 periods of positive sea-level tendencies and by 6 periods of negative sea-level tendencies. Despite the numerous problems associated with the reconstruction of past altitudes of sea level the periods of positive sea-level tendencies were clearly characterised by a rise in sea level, the development of transgressive overlaps and a landward movement of the coastline. The periods of negative sea-level tendencies were characterised by the development of regressive overlaps, a seaward movement of the coastline and a reduced or negative rate of sea-level rise. The various altitudinal errors do not permit the incontrovertible distinction of periods of falling sea levels. All changes within the Fenland were not synchronous and local factors influenced the exact nature of each sea-level indicator. Dominant regional and local factors have been identified for different areas and different time periods. The chronological and spatial characteristics of the sequences within the Fenland are best explained by a palaeocoastline without supratidal barriers controlling sedimentation. The data indicate an average crustal subsidence in the Fenland of 0.9m/1000 years since c. 6500 BP and the pattern of positive and negative tendencies of sea-level movement is also seen in the chronologies for north west England and north east Scotland. 相似文献
9.
受限陆表海的海侵模式 总被引：22，自引：4，他引：22
突发性海侵是受限陆表海的特征之一,受海平面升降引起的峡口启闭控制,多发生在板块的活动边缘。突发性海侵常有相序缺失,常见海陆相交互层;海相层在大范围内分布稳定,无明显相变,具有良好的等时性,可以作为区域对比的标志层。受限陆表海的突发性海浸,有利于油气的生成和聚集。 相似文献
10.
Yang Zigeng 《《地质学报》英文版》1994,7(2):195-207
Abstract According to the alternation of terrestrial beds and transgressive beds, the sedimentary sequence of the South Yellow Sea since the Olduvai subchron can be divided into 15 strdatigraphical intervals. According to the facies analysis, there are 7 transgressive beds an one bed with transgression marks, and classical transgressive-regressive facies sequence also appears in the major transgressive beds. Palaeogeographic evolution in the shelf area involved 4 periods: (1) 1.70-0.5 Ma B. P. was the stage for the development of the Palaeo-Yangtze River alluvial plain and delta. Tide influenced-river channel sediments formed during the Olduvai have been found in borehole QC2. The river mouth was located near 124° E and during the transgressive stage from 0.97-0.73 Ma B.P. to the east of 122.2° E, a large-scale undersea delta was formed. In the regressive stage, the shelf area became an alluvial plain. (2) 0.50-0.75 Ma B.P. was a multi-transgressive fluctuation stage during which 3 transgressive beds (HVI, HV, HIV)developed, being dated as 0.50-0.30 Ma B.P., 0.27-0.20 Ma B.P. and 127-75 Ka B.P. respectively, with the extent of transgression increasing gradually. Influenced by southeast monsoons, the eastern China continent began to have a larger moisture source. (3) 75–14 Ka B.P. was the lower sea-level stage during the last glacial period. The downcuttihg depth of rivers was up to -133 m. The palaeo-Yangtze River system flowed northeastwards into the Sea of Japan through the Sea of Japan through the Tsushima and Korean Straits. The interfluvial area became an eroded, weathered high land. In the cores, two short-lived, relatively high sea-level stages were recorded, corresponding to two interstades in the last glacial period. (4) The period since 14 Ka B.P. is the stage for “Holocene transgression” and the development of the Yellow River-Huaihe River delta. Before 14 Ka the sea level rose to -68 m, and before 11 Ka to -50 m, and the sea-level was once at a standstill or slightly got down, which is coincident with the Younger Dryas event. The Yellow River-Huaihe River delta developed on transgressive bed HI and consists of the superimpositions of 6 deltaic complexes. 相似文献
11.
层序地层学是近20年来发展起来的一门新的方法学科,并在聚煤作用分析中得到广泛应用。作者就近海型含煤岩系沉积学研究历史以及煤系层序地层学研究方法及有关问题进行探讨,认为近海环境的聚煤作用实际上是海平面(基准面)上升过程中发生的,同时提出煤层厚度受泥炭堆积速率与可容空间增加速率的控制：靠陆一侧冲积平原和三角洲平原沉积环境中,厚煤层主要出现在最大海泛面位置;而靠海一侧障壁-潟湖或碳酸盐岩台地沉积环境中,厚煤层主要出现在初始海泛面的位置;但就整个三级复合层序来说,层序中厚度最大、分布最广的煤层主要分布于可容空间增加速率最大的最大海泛面附近的位置。对于中国晚古生代近海型煤系中常见的“根土岩-煤-石灰岩”序列,聚煤作用发生于海相石灰岩“滞后时段”,即在海侵之后、海相石灰岩层真正沉积下来之前的时段,这一时段可容空间增加速率与泥炭堆积速率平衡,有利于聚煤作用发生。 相似文献
12.
The distribution of foraminifers, ostracods, diatoms and pollen is studied in cores from submarine boreholes. This reveals that the history of the Flandrian transgression is largely the record of the infilling of meltwater channels cut during the early Late Glacial with transgressive estuarine and finally marine deposits. It also supports the idea of the ‘climatic earliness’ of the Welsh seaboard at all stages. Estuarine deposits in excess of —51 m O.D. suggest that Late Glacial sea levels were initially as low as —60 m O.D. and support the idea that the Welsh ice withdrew before 14,000 years B.P. The sea-level rise plots as a smooth curve but was probably episodic in its early phases. 相似文献
13.
陆表海盆地海侵事件成煤作用机制分析 总被引：29，自引：4，他引：25
研究了含煤地层中海侵事件沉积序列,即海侵沉积与煤层直接接触的组合特点,总结了海侵事件和海侵事件成煤特点,提出了陆表海聚煤盆地海侵事件成煤作用理论及海侵事件成煤机制。研究表明,陆表海盆地充填沉积序列中,既有海退成煤作用又有海侵成煤作用发生,而且,海侵事件为陆表海盆地海平面变化的典型特色,海侵的突发性是海侵事件的基本属性,其沉积具有等时性。海侵事件导致盆地事件型聚煤作用发生。本文还深入讨论了海侵事件成煤机制及其在含煤地层层序地层界面识别、层序地层单元划分的重要意义和作用。 相似文献
14.
华北晚古生代陆表海盆地海侵事件微观沉积特征及成煤探讨 总被引：3，自引：0，他引：3
采用沉积学、煤地质学、古生物学、地层学及地球化学等多技术手段,结合比较分析法的思路,分析了事件型海侵的特点和海侵事件沉积组合特征,研究发现:海侵事件沉积组合为区域对比性强、具沉积时间连续性与相序间断性的暴露沉积-煤层-灰岩组合,其关键沉积学特征是煤层底板的暴露沉积.海侵事件组合灰岩的古生化石个体小、破碎强烈等特征表现为高能量水体运动等环境,孢粉表现为低含量的单缝孢和裸子植物及高含量的三缝孢.地球化学分析表明暴露沉积为陆相环境,煤层中的微量元素表现为海相主要原因是由于泥炭沼泽覆于深水后受海水影响所致.海侵事件成煤与海侵过程成煤差异体现在两个方面:第一,盆地属性差异,即海侵事件成煤形成于陆表海盆地之中,而海侵过程成煤则形成于具有缓坡的边缘海盆地,第二,成煤原理存在着差异,海侵事件成煤强调的是成煤前海侵未发生前的碎屑体系废弃而发育大量泥炭沼泽且被后期突发性海侵终止,而海侵过程成煤则强调的是泥炭沼泽发育于滨海的活动碎屑体系并终止于后期的缓慢海平面上升. 相似文献
15.
The Lower Tagus Valley in Portugal contains a well-developed valley-fill succession covering the complete Late Pleistocene and Holocene periods. As large-scale stratigraphic and chronologic frameworks of the Lower Tagus Valley are not yet available, this paper describes facies, facies distribution, and sedimentary architecture of the late Quaternary valley fill. Twenty four radiocarbon ages provide a detailed chronological framework. Local factors affected the nature and architecture of the incised valley-fill succession. The valley is confined by pre-Holocene deposits and is connected with a narrow continental shelf. This configuration facilitated deep incision, which prevented large-scale marine flooding and erosion. Consequently a thick lowstand systems tract has been preserved. The unusually thick lowstand systems tract was probably formed in a previously (30,000–20,000 cal BP) incised narrow valley, when relative sea-level fall was maximal. The lowstand deposits were preserved due to subsequent rapid early Holocene relative sea-level rise and transgression, when tidal and marine environments migrated inland (transgressive systems tract). A constant sea level in the middle to late Holocene, and continuous fluvial sediment supply, caused rapid bayhead delta progradation (highstand systems tract). This study shows that the late Quaternary evolution of the Lower Tagus Valley is determined by a narrow continental shelf and deep glacial incision, rapid post-glacial relative sea-level rise, a wave-protected setting, and large fluvial sediment supply. 相似文献
16.
通过对广西六景、贵州独山和乌当泥盆系剖面层序、体系域、副层序及作用相和环境相的系统研究,识别出2种层序界面;3种海进过程和10种层序、体系域和相对海面变化.并发现,阶跃型高幅海平面变化形成的层序界面、层序、体系域、副层序和旋回层往往可在大区域追踪对比;剖面作用相、环境相分析是露头层序地层和相对海平面变化研究的基础,剖面上层序、体系域及其反映的相对海平面变化的频率、幅度、速度和相位研究对层序界面、层序、体系域、副层序和旋回层的空间延拓、等时追踪对比和驱动机制的成因解释有重要的指导、预测作用. 相似文献
17.
V. PAUL WRIGHT 《Sedimentology》1986,33(2):221-241
During early Carboniferous times a major sea-level rise led to the development of an extensive carbonate ramp over what is now South Wales. Differential subsidence and sea-level changes resulted in distinctive facies sequences in the ramp succession and a model is offered which recognizes three distinct geomorpho-tectonic settings; inner, mid- and outer ramp. The inner ramp zone occurs in the more landward part of the province and was an area undergoing little or no subsidence. The sequence is dominated by oolitic grainstones and peritidal limestones representing shoal and back shoal environments. The peritidal units are transgressive deposits consisting of stacked asymmetrical shallowing-up cycles. The sequence contains many subaerial breaks and tectonic uplift resulted in base-level changes and fluvial incision. The mid-ramp zone sequence is intermediate in thickness between the inner and outer ramp successions and consists mainly of bioclastic limestones deposited below fairweather wave base. Sedimentation periodically exceeded sea-level rise and subsidence, and regressive (progradational) oolitic sand bodies developed, the thickest of which are stacked units with up to four individual sand bodies. Storm processes were of major importance in this setting. The outer ramp zone is represented by a thick sequence of muddy bioclastic limestones deposited below storm wave base and major Waulsortian reef-mounds also developed. None of the shallowing phases seen in the other ramp zones can be detected in this sequence. Subsidence and eustatic sea-level rise seem to have been the major controls on deposition but the recognition of eustatic sea-level falls is difficult. The detailed facies model for ramp carbonates presented here may be applicable elsewhere in the geological record. 相似文献
18.
二叠纪-三叠纪界线附近的全球海平面变化是当前沉积学研究的热点和难点问题,其与当时的显生宙最大规模生物灭绝事件存在一定关联,具有重要的研究意义。然而二叠纪-三叠纪界线附近的全球海平面变化存在较多争议,受单剖面或区域范围内相对海平面变化研究程度的制约,在缺乏从沉积学角度的综合对比研究的情况下,可能会影响对全球海平面变化过程与持续时间的判识。综述了二叠纪-三叠纪界线附近的海平面变化研究进展,整合了多位学者的研究剖面、主要观点及认识,梳理了全球海平面变化的主要观点（“上升论”和“下降-上升论”）,包括其各自的发展历程、代表剖面及海平面变化识别特征、海平面上升/下降的原因以及海平面变化与生物灭绝的关系等,并在此基础上,探讨了二叠纪-三叠纪全球海平面变化研究过程中产生争议的原因。本文旨在为二叠纪-三叠纪界线（PTB）附近海平面变化研究提供线索,同时为研究全球PTB地质事件发生的背景及差异性原因提供基础证据。 相似文献
19.
我国沿岸晚第四纪砂坝-泻湖体系的沉积模式 总被引：5，自引：2，他引：5
我国沿岸晚第四纪砂坝-泻湖体系可以分为海侵型、海退型、稳定型和局部海侵型,其理想分布模式为:海侵型分布于大陆架至冰后期最大海侵线之间的沉积层下部;海退型形成于最大海侵线至现代海岸线之间全新世沉积层上部;稳定型则出现在最大海侵线附近的狭窄地带。我国海岸线通过构造沉降带和隆起带,沉降带接受大量河流输沙,为多种砂坝-泻湖沉积体系准备了条件.隆起带沿岸沉积物来源贫乏,主要发育稳定型和局部海侵型砂坝-泻湖体系. 相似文献
20.
Marginal marine deposits of the John Henry Member, Upper Cretaceous Straight Cliffs Formation, were deposited within a moderately high accommodation and high sediment supply setting that facilitated preservation of both transgressive and regressive marginal marine deposits. Complete transgressive–regressive cycles, comprising barrier island lagoonal transgressive deposits interfingered with regressive shoreface facies, are distinguished based on their internal facies architecture and bounding surfaces. Two main types of boundaries occur between the transgressive and regressive portions of each cycle: (i) surfaces that record the maximum regression and onset of transgression (bounding surface A); and (ii) surfaces that place deeper facies on top of shallower facies (bounding surface B). The base of a transgressive facies (bounding surface A) is defined by a process change from wave‐dominated to tide‐dominated facies, or a coaly/shelly interval indicating a shift from a regressive to a transgressive regime. The surface recording such a process change can be erosional or non‐erosive and conformable. A shift to deeper facies occurs at the base of regressive shoreface deposits along both flooding surfaces and wave ravinement surfaces (bounding surface B). These two main bounding surfaces and their subtypes generate three distinct transgressive – regressive cycle architectures: (i) tabular, shoaling‐upward marine parasequences that are bounded by flooding surfaces; (ii) transgressive and regressive unit wedges that thin basinward and landward, respectively; and (iii) tabular, transgressive lagoonal shales with intervening regressive coaly intervals. The preservation of transgressive facies under moderately high accommodation and sediment supply conditions greatly affects stratigraphic architecture of transgressive–regressive cycles. Acknowledging variation in transgressive–regressive cycles, and recognizing transgressive successions that correlate to flooding surfaces basinward, are both critical to achieving an accurate sequence stratigraphic interpretation of high‐frequency cycles. 相似文献