共查询到20条相似文献，搜索用时 31 毫秒
1.
Rosana Gandini Dilce de Fátima Rossetti Renata Guimarães Netto Francisco Hilário Rego Bezerra Ana Maria Góes 《Quaternary Research》2014
Quaternary post-Barreiras sediments are widespread along Brazil's passive margin. These deposits are well exposed in the onshore Paraíba Basin, which is one of the rift basins formed during the Pangean continental breakup. In this area, the post-Barreiras sediments consist of sandstones with abundant soft-sediment deformation structures related to seismicity contemporaneous with deposition. The trace fossils Thalassinoides and Psilonichnus are found up to 38 m above modern sea level in sandstones dated between 60.0 (± 1.4) and 15.1 (± 1.8) ka. The integration of ichnological and sedimentary facies suggests nearshore paleoenvironments. Such deposits could not be related to eustatic sea-level rise, as this time coincides with the last glaciation. Hence, an uplift of 0.63 mm/yr, or 1.97 mm/yr if sea level was 80 m lower in the last glaciation, would have been required to ascend the post-Barreiras sediments several meters above the present-day sea level during the last 60 ka. This would suggest that the post-rift stage of the South American eastern passive margin may have experienced tectonic reactivation more intense than generally recognized. Although more complete data are still needed, the information presented herein may play an important role in studies aiming to decipher the Quaternary evolution of this passive margin. 相似文献
2.
近年来,混合沉积研究已逐渐成为沉积学领域颇受关注的重要课题。在前人研究的基础上系统梳理、总结了国内外混合沉积研究所取得的进展,提出了现阶段混合沉积研究面临的主要问题。国内外混合沉积研究可划分为4个阶段:现象描述阶段、基础理论研究阶段、海相混合沉积研究阶段、陆相混合沉积及综合研究阶段。受不同地质条件的约束,混合沉积岩石学分类方案并未形成统一的标准。混合沉积成因类型一般包括间断混合、相混合、原地混合与母源混合。混合沉积现象具有普遍性,可发育于海相、淡水湖盆、咸化湖盆等各类型沉积环境中,具有多样化的沉积类型,其控制因素一般包括碎屑物质供给、气候与水体环境、海（湖）平面变化、古地貌条件、构造作用以及水动力条件等。混合沉积具有重要的油气地质意义,与三角洲伴生的近源混合沉积、水下隆起区的远源混合沉积以及藻混合沉积可形成优质的陆相混积型油气储层。现阶段混合沉积研究中主要存在以下几方面问题:岩石分类方案不统一、缺乏与野外露头剖面和现代沉积的考察对比、层序格架内混合沉积发育模式不清、传统的成因类型在复杂陆相混合沉积研究中的应用存在较大局限性、混积型储层地震响应特征不明确。针对混合沉积进行全面、深入的研究,对古地理环境恢复、沉积动力学分析及相关油气勘探具有重要的意义。 相似文献
3.
Frihy Omran E. 《GeoJournal》1992,26(3):389-394
Carbon dating data of changes in seal level during the Holocene at the Nile delta coast provide eustatic depth-time curve
of the region. The curve reveals that sea level was approximately 41 meters below the present level around 8,500 years ago.
Trend analysis indicates that with melting of glaciers there was a rapid rise in sea level of about 3 mm/yr. The constructed
data points are found to be comparable with other curves in the Mediterranean and wold-wide regions. The general changes of
the data points are fairly correlated with the ancient shoreline indicators of morphological features (shelf terraces and
slopes, old dunes, sand accretion ridges) and sediments at continental shelf and its contiguous coastal zone that belong to
Holocene transgression. 相似文献
4.
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
5.
中国东部晚第四纪海侵的新构造背景 总被引：19，自引：1，他引：18
中国东部沉降海岸及近海钻孔研究表明,第四纪大部分时间里,福建－岭南隆起带基本阻挡了海水大规模进入东海－黄海盆地,约在１６０ｋａ ＢＰ已有低海相性的海侵出现,但是自末次间冰期以来才开始发生大规模海侵,而此时青藏高原正以空前的速率隆升。 相似文献
6.
A. R. Wyatt 《International Journal of Earth Sciences》1993,82(2):185-188
Sediment yield from modern continental blocks is a function of the area (dissolved load) and hypsometry (mechanical load) of the blocks. Hypsographic curves for modern continental blocks show that the change in the percentage area flooded for any change in eustatic sea level depends on the size of the block and the absolute sea level. This allows predictions of changes in sediment yield around different sized blocks for any given eustatic change. The range in size of continental blocks is such that, for any given sea level change, the blocks will show different percentage changes in yield. Data from modern continental blocks are compared with theoretical results. Assuming that the rules governing modern hypsometries applied in the past, and a constant volume of continental crust, it is possible to estimate the hypsographic curves of former continental blocks. The implications of suggested past continental configurations and sea levels for sediment yield are discussed. 相似文献
7.
Kristian Vasskog John‐Inge Svendsen Jan Mangerud Kristian Agasster Haaga Arve Svean Eva Maria Lunnan 《第四纪科学杂志》2019,34(6):410-423
Based on six consistent radiocarbon dates from the isolation basins Grødheimsvatnet and Kringlemyr, we estimate a minimum deglaciation age for southern Karmøy, an island in outer Boknafjorden (south‐west Norway), of around 18 000 calibrated years before present (18k cal a bp ). We use microscopic phytoplankton, macrofossils, lithostratigraphic evidence and X‐ray fluorescence data to identify the isolation contacts in the basins, and date them to 17.52–17.18k cal a bp in Grødheimsvatnet [15.57 m above present mean sea level (MSL)] and 16.19–15.80k cal a bp in Kringlemyr (11.99 m above MSL). Combining these data with previous studies, we construct a relative sea‐level (RSL) curve from 18k cal a bp until the present, which is ~3 ka longer than any previous RSL reconstruction from southern Norway. Following deglaciation, southern Karmøy has experienced a net emergence of around 16–19 m, although with significant RSL fluctuations. This includes two RSL minima well below present MSL around ~13.8 and ~10k cal a bp , and two maxima that culminated around 5–7 m above MSL during the Younger Dryas and early to mid‐Holocene, respectively. Considering eustatic sea level and modelled gravitational deformation of the geoid, we estimate a net postglacial isostatic uplift of ~120 m. © 2019 John Wiley & Sons, Ltd 相似文献
8.
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.
Earthquakes are widely recognized as triggers for turbidites, submarine debris flows and slumps. In tectonically active areas, surprisingly small changes in stress can trigger seismic events, implying that past sea level changes may be important in controlling the timing of seismicity and the occurrence of turbidites. We apply this idea in an analysis of turbidites from the upper Cretaceous–Paleocene Scaglia Rossa Formation of the Umbria‐Marches region of Italy. These turbidites are composed of resedimented foraminiferal tests derived from fluidizing deep‐water (∼1500 m), pelagic sediments; seismic triggering is the most likely triggering mechanism given this setting and composition. The timing of these turbidites (and associated synsedimentary slumps), constrained by biostratigraphy and magnetostratigraphy, reveals an unusual, non‐random temporal pattern that appears to correlate well with proposed eustatic fluctuations. This correlation between turbidites and eustatic fluctuations leads us to suggest that stress and pore fluid pressure changes associated with changing sea level may trigger periods of increased seismicity in the geological past. 相似文献
11.
全新世长江泥沙堆积的时空分布及通量估算 总被引：1，自引：1，他引：0
利用长江中下游、河口及口外、浙-闽沿岸陆架6个主要沉积盆地的40个晚第四纪钻孔及其年代学数据和长江口外、陆架的浅地层剖面,计算了全新世不同阶段各沉积盆地的沉积速率,并进行了近7 000年来泥沙堆积通量的估算。研究发现全新世早期距今10 000年至8 000年间长江口下切古河谷是长江泥沙的主要堆积中心,沉积速率可高达15m/ka。随着海平面上升,全新世中期长江中下游也成为长江泥沙的重要沉积盆地,其中江汉盆地的沉积速率可达10m/ka。近2 000年来,口外、陆架的堆积呈明显增加趋势,反映长江中下游盆地和河口可容空间日益减小。根据沉积速率估算,距今7 000年来长江中下游堆积泥沙约13 074×108 t,同期水下三角洲和陆架的泥沙堆积量约为9 470×108 t。研究还发现全新世以来有两个异常低沉积速率时期：距今8000-7 000年期间上述各沉积盆地沉积速率均显著低,未见长江泥沙的沉积中心; 距今4 000-2 000 年期间长江口呈现低沉积速率。 这两次异常的原因推测与海平面、气候波动事件密切相关。 相似文献
12.
Patrick J. Brenchley Jim D. Marshall David A. T. Harper Caroline J. Buttler Charlie J. Underwood 《Geological Journal》2006,41(1):1-22
The growth and decay of the end‐Ordovician Gondwanan glaciation is globally reflected by facies changes in sedimentary sequences, which record a major eustatic fall and subsequent rise in the Hirnantian Stage at the end of the Ordovician. However, there are different reported estimates of the magnitude and pattern of sea‐level change. Particularly good evidence for end‐Ordovician sea‐level change comes from a sequence at Meifod in central Wales, which has a karstified limestone unit within a channel incised into marine shelf sediments. Pre‐glacial (Rawtheyan) mudstones have a diverse fauna suggesting a mid‐to‐deep‐shelf water depth of c. 60 m. The channel, 20 m deep, was incised into these mudstones and partially filled with a mixture of fine sand and detrital carbonate. The taphonomy of bioclasts and intraclasts indicates that many had a long residence time on the sea floor or suffered diagenesis after shallow burial before being resedimented into the channel. The presence of carbonates on the Welsh shelf is atypical and they are interpreted as having accumulated as patches during a minor regression prior to the main glacio‐eustatic fall. Comparison of the carbon stable‐isotopic values of the bioclast material with the global isotopic record confirms that most of the material is of Rawtheyan age, but that some is Hirnantian. The resedimented carbonates lithified rapidly and formed a limestone, several metres thick, in the deepest parts of the channel. As sea‐level fell, this limestone was exposed and eroded into karstic domes and pillars with a relief of over 2 m. The overall, glacio‐eustatic, sea‐level fall is estimated to be in excess of 80 m. A succeeding sea‐level rise estimated to be 40–50 m is recorded in the laminated crust that mantles the karstic domes and pillars. The crust is formed of encrusting bryozoans, associated cystoids, crinoid holdfasts and clusters of the brachiopod Paromalomena, which is normally associated with mid‐shelf environments. Fine sands buried the karst topography and accumulated to fill the channel. In the sandstones at the base of the channel there is a Hirnantia fauna, while in the sandstones high in the channel‐sequence there is cross‐stratification characteristic of mid‐shoreface environments. This would indicate a fall of sea‐level of c. 30 m. The subsequent major transgression marking the end of the glaciation is not recorded at the Meifod locality, but nearby exposures of mudstones suggest a return to mid‐to‐deep‐shelf environments, similar to those that prevailed before the Hirnantian regression. The Meifod sequence provides strong evidence for the magnitude of the Hirnantian sea‐level changes and by implication confirm larger estimates for the size of the ice sheets. Smaller oscillations in relative sea‐level seen at Meifod may be local phenomena or may reflect eustatic changes that have not been widely reported elsewhere. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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14.
塔里木盆地上泥盆统与石炭系层序地层分析 总被引：9，自引：0，他引：9
塔里木盆地晚泥盆世-石炭纪为远离陆棚边缘的陆棚内部碎屑岩和碳酸盐岩陆表海沉积环境,在层序地层分布模式上与Vail等根据被动大陆边缘盆地提出的层序地层分布模式有所不同。共将上泥盆统-石炭系划分出五个层序,十四个体系域。其中,第Ｉ层序是在快速的海平面上升和陆源碎屑物质快速补偿条件下形成的;第Ⅱ层序代表陆源物质补给由快变慢的条件下形成的;第Ⅲ层序代表海面由慢速上升至快速下降过程中且陆源物质补给相对稳定条件下形成的;第Ⅳ层序代表海平面快速上升与陆源物质补给相对稳定的条件下形成的;第Ⅴ层序是在快速海平面上升及陆源物质供给补偿不足的条件下形成的。塔里木盆地晚泥盆世-石炭纪的沉积史是在相对海平面呈阶段性上升的海侵过程中发生的,可将这一时期的海平面变化划分为五个二级周期旋回。其中构造作用对第Ｉ、Ｉ、Ｖ周期的形成起了重要的作用。 相似文献
15.
Telm Bover‐Arnal Ramon Salas Joan Guimerà Josep Anton Moreno‐Bedmar 《Sedimentology》2014,61(6):1558-1593
Long‐term relative sea‐level cycles (0·5 to 6 Myr) have yet to be fully understood for the Cretaceous. During the Aptian, in the northern Maestrat Basin (Eastern Iberian Peninsula), fault‐controlled subsidence created depositional space, but eustasy governed changes in depositional trends. Relative sea‐level history was reconstructed by sequence stratigraphic analysis. Two forced regressive stages of relative sea‐level were recognized within three depositional sequences. The first stage is late Early Aptian age (intra Dufrenoyia furcata Zone) and is characterized by foreshore to upper shoreface sedimentary wedges, which occur detached from a highstand carbonate platform, and were deposited above basin marls. The amplitude of relative sea‐level drop was in the order of tens of metres, with a duration of <1 Myr. The second stage of relative sea‐level fall occurred within the Late Aptian and is recorded by an incised valley that, when restored to its pre‐contractional attitude, was >2 km wide and cut ≥115 m down into the underlying Aptian succession. With the subsequent transgression, the incision was backfilled with peritidal to shallow subtidal deposits. The changes in depositional trends, lithofacies evolution and geometric relation of the stratigraphic units characterized are similar to those observed in coeval rocks within the Maestrat Basin, as well as in other correlative basins elsewhere. The pace and magnitude of the two relative sea‐level drops identified fall within the glacio‐eustatic domain. In the Maestrat Basin, terrestrial palynological studies provide evidence that the late Early and Late Aptian climate was cooler than the earliest part of the Early Aptian and the Albian Stage, which were characterized by warmer environmental conditions. The outcrops documented here are significant because they preserve the results of Aptian long‐term sea‐level trends that are often only recognizable on larger scales (i.e. seismic), such as for the Arabian Plate. 相似文献
16.
新生代以来南中国海的多幕旋回运动形成了其北部陆坡性质各异、演化有别的多个陆缘沉积盆地。依据各盆地新生界发育特征、主干地震剖面及钻井资料对南海北部的相对海平面变化与沉积环境进行系统分析,采用年代地层对比的方法探讨南海北部构造演化序列与海陆变迁规律的内在联系,再现了南海北部陆缘新生代的海陆变迁过程,从而建立了南海北部陆缘裂谷盆地、走滑拉分盆地和陆内裂谷盆地的构造—沉积充填一体化模式。新生代海平面整体呈上升趋势,古近纪各盆地以陆相河流、粗粒三角洲湖相沉积为主;而新近纪主要发育滨浅海及三角洲相,呈现出明显的早陆后海的规律。靠近陆地一侧的陆内裂谷盆地北部湾盆地海侵最晚,其古近系充填厚度明显大于新近系,以发育近源扇三角洲为特色;而靠近海域一侧的走滑拉分盆地(莺歌海盆地)则以新近纪海相沉积占优势;陆缘裂谷盆地(琼东南与珠江口盆地)古近纪陆相与新近纪海相相对均衡发育,发育大型三角洲与碳酸盐岩台地。不同盆地的沉积充填特征主要受构造运动与海侵规模控制,并由此奠定了不同盆地的资源前景。 相似文献
17.
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
18.
南京地区分布着一套新近纪的松散砂砾沉积,曾被统称为雨花台砾石层。依据岩性、层序、沉积构造等特征,我们解译了4个地点砂砾层的沉积环境。研究发现,洞玄观组的沉积环境类似于曲流河沉积,六合组类似于砂质辫状河沉积,雨花台组则属于砾质辫状河沉积。沉积环境的不同印证了前人的观点,即这些砂砾层是不同时期形成。古流向显示,从中新世到更新世早期本区的流域格局与目前的大体一致。而河流沉积环境的演化,却指示河道的坡降具有不断增大的趋势。我们认为这可能是全球海平面不断下降导致侵蚀基准面降低所引起的,而差异性的构造运动似乎不是主要的驱动因素。 相似文献
19.
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
20.
K.B. Lewis 《Earth》1974,10(1):37-71
The continental terrace, defined as the sediment and rock underlying the coastal plain, the continental shelf and continental slope, has been extensively explored during the last decade using seismic techniques. Some facts and theories about its structure and formation are reviewed.The development of the continental terrace is considered in three main stages: first, the formation of the major discontinuity between continent and ocean basin; second, the deposition of sedimentary strata; and third, the Quaternary modification of the continental terrace to form the present topography.The major discontinuity may be formed either by rifting of a continent or by accretion of a large mass of contorted continental terrace and continental rise sediments to a pre-existing edge of a continent. Both types of discontinuity may be either ancient or presently forming in an orogenic area. Sedimentary strata are built generally upwards and outwards but at most places development is modified either by basement structure, by current and slump erosion or by growth of organic and diapiric structures.During the Quaternary Era the terrace has been extensively modified as a result of large fluctuations of sea level. The present wide continental shelf and deep shelf break are at most places the result of wave planation and offshore deposition during the last low sea level and during the subsequent rise of sea level. The final process at many places has been formation of a Holocene coastal plain and deposition of a prism of sediment on the inner continental shelf.Most continental terraces show evidence of continental flexure, which is the seaward tilting of land and seabed with a zero isobase, a line of no vertical movement, close to the shore. The reasons for continental flexure are discussed. The relative positions of the shore line, the zero isobase and the boundary between erosion and deposition are controlled by rates of tilting, by rates of sedimentary processes and by eustatic movements of sea level.From an assessment of the general processes operating today, some conclusions are reached about the changes in form and topography of continental terraces of the past. 相似文献