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EPPO OOMKENS 《Sedimentology》1974,21(2):195-222
A study of cores from thirty-three coreholes drilled in various parts of the Niger delta has shown tidal channel sand to be the dominant lithofacies type in the uppermost 30 m of the deltaic complex. Below 30 m fluviatile sand becomes predominant. Coastal barrier sand is present in the uppermost 5 m of the present coastal belt, but chances for preservation of this lithofacies appear to be small. The Post-Glacial deltaic sediments can be divided into three units.
- 1 Alluvial valley-fill sands and conglomerates deposited during the strong Post-Glacial sea level rise.
- 2 An onlapping complex of lower coastal plain deposits which contains a lower member of fine grained lagoonal and mangrove swamp deposits and an upper member of tidal channel and coastal barrier sands. This complex is thought to have been deposited during the strong Post-Glacial rise in sea level and is locally as much as 25 m thick.
- 3 An offlapping complex of fluviomarine and coastal deposits which contains a lower member of marine clay and silt and an upper member of tidal channel and coastal barrier sand. The presence of this late Holocene complex indicates that deltaic progradation was resumed as soon as the rapid rise in sea level slowed down. The offlapping complex is locally as much as 35 m thick.
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A palynological and sedimentological study has been carried out on the Cretaceous fluvial and deltaic Atane Formation of West Greenland. Two localities, Skansen and Igdlunguaq on the southern coast of Disko island, have been studied. The sediments are divided into two genetic facies associations interpreted as representing deposition in fluvial channels and on a floodplain. The facies indicate that most of the sediments on the floodplain accumulated in swamps or shallow lakes, whereas abundant spores and pollen indicate the presence of vegetated land nearby. The palynomorph assemblages recovered consist of 72 species of spores and pollen grains of bryophytes, pteridophytes, gymnosperms and angiosperms. The palynomorphs from Skansen and most of those from Igdlunguaq indicate a maximum age-range from late Albian to Cenomanian for the successions sampled, although a mid Cenomanian age seems most likely. The highest horizon examined at Igdlunguaq may, however, be late Cenomanian or Turonian in age. The assemblages compare well with palynofloras from North America and Northwest Europe. 相似文献
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Analysis of 92 engineering core logs located in the Balize sector of the eastern Mississippi delta focuses on the late Wisconsin unconformity and lithofacies of strata lying immediately below and above this stratigraphic horizon. This major sequence boundary is a key feature used to correlate strata across shelf and slope to the basin. Observations emphasize lithofacies distributions of the latest Pleistocene sediments underlying the unconformity, the late Pleistocene to early Holocene transgressive facies, and the immediately overlying deltaic deposits. Maps and a cross-section compiled with this information highlight the critical relation between lithofacies distributions and late Wisconsin sea-level oscillations. Core analysis reveals that the transgressive facies comprises distinct environments of deposition, offshore to onshore. Findings identify criteria to determine the approximate position of the shoreline at the late Wisconsin maximum sea-level lowstand and at the extent of early Holocene maximum marine inundation in the Balize complex. Mapping of lithologies along the late Wisconsin unconformity serves to improve correlation of sediment facies with changes in acoustic response along high-resolution seismic profiles. An estimate of long-term averaged land subsidence suggests lowering of at least 1 mm/year near the shelfedge during the past 18 000 years. This mapping also refines sea-level response models for the Mississippi delta, including criteria to locate key paleogeographic features such as shelfedges and maximum flooding surfaces in other Recent marine deltas and in older, stacked deltaic sequences. 相似文献
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《Quaternary Science Reviews》2007,26(3-4):322-335
An exposure within the central portion of a large drumlin at Port Byron, New York State, USA, part of the large New York drumlin field, reveals a sequence of steeply dipping cemented sands and gravels of proglacial, ice-contact deltaic origin overlain by a thin till veneer. The sands and gravels appear to have been deposited within the proximal proglacial environment during a late retreat phase of the Laurentide Ice Sheet sometime prior to being overridden by subsequent ice and drumlinized. During deposition of the ice-contact delta, escaping subglacial regelation-meltwater permeated the proximal deltaic sediment pile and calcium carbonate was released, in a series of pulses, to form pore-occluding calcite cement within the sand and gravel porespaces. The calcium carbonate precipitated into the sands and gravels due to a reduction in hydrostatic pressure and CO2 outgassing of the meltwater as it exited from beneath the ice sheet. Once cemented, these deltaic sediments were considerably stronger and acted afterward as an obstacle around which the future ice advance streamed and, in turn, produced the characteristic drumlin shape. In overriding the ice-contact deltaic sediments, the ice sheet emplaced a thin layer of till which exhibits syndepositional deformation features indicative of being emplaced as a deforming bed layer beneath the advancing ice sheet. Micromorphological analysis of the overlying till shows that no interstitial or intraclastic calcite occurs within the till. 相似文献
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Testing optically stimulated luminescence dating on sand-sized quartz of deltaic deposits from the Sperchios delta plain,central Greece 总被引：1，自引：1，他引：0
Evangelos Tsakalos Elias Dimitriou Maria Kazantzaki Christos Anagnostou John Christodoulakis Eleni Filippaki 《古地理学报》2018,(2)
This study reports on the first investigation into the potential of luminescence dating to establish a chronological framework for the depositional sequences of the Sperchios delta plain, central Greece. A series of three borehole cores(20 m deep) and two shallow cores(4 m deep), from across the delta plain, were extracted, and samples were collected for luminescence dating. The luminescence ages of sand-sized quartz grains were obtained from small aliquots of quartz, using the Single-Aliquot Regenerative-dose(SAR) protocol.The equivalent dose determination included a series of tests and the selection of the Minimum Age Model(MAM) as the most appropriate statistical model. This made it possible to confirm the applicability of quartz Optically Stimulated Luminescence(OSL) dating to establish absolute chronology for deltaic sediments from the Sperchios delta plain.Testing age results of the five cores showed that the deltaic sediments were deposited during the Holocene.A relatively rapid deposition is implied for the top ~14 m possibly as a result of the deceleration in the rate of the sea-level rise and the transition to terrestrial conditions, while on the deeper parts, the reduced sedimentation rate may indicate a lagoonal or coastal environment. 相似文献
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Jeffrey E. Gutsell John J. Clague Melvyn E. Best Peter T. Bobrowsky Ian Hutchinson 《第四纪科学杂志》2004,19(5):497-511
The architectural framework and Holocene evolution of the Zeballos fjord‐head delta on west‐central Vancouver Island was established through a multidisciplinary field‐based study. The Zeballos delta is a composite feature, consisting of an elevated, incised, late Pleistocene delta and an inset Holocene delta graded to present sea level. Both deltas have a classic Gilbert‐type tripartite architecture, with nearly flat topset and bottomset units and an inclined foreset unit. Time domain electromagnetic (TDEM) and ground‐penetrating radar (GPR) surveys, borehole data, and gravel pit exposures provided information on the internal form, lithologies and substrate of both deltas. Both sets of deltaic deposits coarsen upward from silt in the bottomset unit to gravel in the topset unit. The TDEM survey revealed a highly irregular, buried bedrock surface, ranging from 20 m to 190 m in depth, and it delineated saltwater intrusion into the deltaic sediments. Late Quaternary sea‐level change at Zeballos was inferred from delta morphology and the GPR survey. The elevated, late Pleistocene delta was constructed when the sea was about 21 m higher relative to the land than it is today. It was dissected when sea‐level fell rapidly as a result of glacio‐isostatic rebound. Relative sea‐level reached a position about 20 m below the present datum during the early Holocene. Foreset beds that overlap and progressively climb in a seaward direction and topset beds that thicken to 26 m landward imply that the delta aggraded and prograded into Zeballos Inlet during the middle and late Holocene transgression. Sea‐level may have risen above the present datum during the middle Holocene, creating a delta plain at about 4 m a.s.l. Remnants of this surface are preserved along the valley margins. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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PIERRE CALLOT FRANCIS ODONNE ELIE-JEAN DEBROAS AGNÈS MAILLARD DAMIEN DHONT† CHRISTOPHE BASILE‡ GUILHEM HOAREAU 《Sedimentology》2009,56(5):1226-1249
Five successive fossil submarine slides have been mapped and described in the Sobrarbe deltaic complex (Ainsa Basin, Spanish Pyrenees). These slides affect and remove up to 15% of the delta front. The head of the scar surfaces is recognized clearly in the field due to the angular unconformity between the infilling sediments and the underlying layers. Most of the slide scarps trend 55°N with 20° to 40° dips indicating north-westward sliding. Downslope, traces of the sliding surfaces parallel stratification. However, these surfaces can be identified by displaced masses, resedimented sandstones and soft-sediment deformation features such as metre-scale half-grabens, normal faults and tension cracks; all the surfaces indicate a sliding displacement toward the north-west. A three-dimensional model built from topographic data with Earth Vision® software shows the architecture of the slide surfaces and provides an estimation of the volume of each sedimentary body within the limit of the studied area. This study also indicates that: (i) the sediments have been cut and carried away before their lithification; (ii) the sedimentation rate infilling a single slump scar is estimated to be about 8 m per 1000 years, i.e. 10 times higher than in the overall area of the Sobrarbe deltaic complex; (iii) each composite scar progressively develops and infills by retrogressive slumps; (iv) the successive slide surfaces stack vertically in a collapse complex structure and migrate downward to follow the sea-level drop between two successive collapse complex structures; (v) the development of the scars in the Sobrarbe delta is described from a seven-stage conceptual model starting with a regressive event; and (vi) the triggering of the Sobrarbe instabilities is controlled by high values of sedimentation rate, relative sea-level falls mainly controlled by tectonic uplift, and likely seismic activity. 相似文献
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三角洲冲淤具有空间异质性,而沉积物的磁性特征可灵敏地反映物源、沉积动力特征以及早期成岩作用影响,是揭示空间异质性的有效方法。选取长江水下三角洲20~35 m水深的四个约2 m长的柱样进行磁学和碳、硫地球化学分析,结合粒度及年代资料,探讨了长江水下三角洲沉积物柱样磁性特征空间差异及其冲淤指示意义。研究结果显示,粒度表征的动力分选影响沉积物的磁性特征,这在年代较新（<350 a）的柱样中表现尤为明显,即细颗粒沉积物中富集亚铁磁性矿物,从而具有较高的磁化率。铁、碳、硫及硫同位素特征揭示了长江水下三角洲沉积物较弱的硫酸盐还原特征。沉积物年龄及沉积速率影响沉积物成岩改造强度,进而导致了磁性特征垂向变化的空间差异,整体上看,远离现代沉积中心的柱样,成岩改造特征更为明显。磁化率值的大小、成岩分带的完整性及其反映的铁还原带和硫酸盐还原带转换深度,一定程度上可以揭示三角洲的淤积和侵蚀特征。 相似文献
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通过对准噶尔盆地阜东斜坡区侏罗系的沉积背景,沉积岩成分,结构、构造及岩性序列等综合研究表明,该区侏罗系具有较好的旋回性,可划分为６个沉积层序和两个构造层序,侏罗系沉积物具有较低的成分成熟度和中等结构成熟度,粒度概率图及沉积构造均显示其具有牵引流沉积特征及三角洲沉积序列。在研究区侏罗系发育南、北两大特源区及方向的水系,据此可识别出辫状河,辫状河三角洲、曲流河、正常三角洲、滑塌浊积扇和湖泊等多种沉积体 相似文献
12.
湘西北永顺——龙山地区早志留世三角洲沉积 总被引：2，自引：0，他引：2
湘西北早志留世龙马溪期至溶溪期为三角洲沉积，可划分出前三角洲、三角洲前缘和三角洲平原三个亚相。前三角角洲亚相以龙马溪组为代表，已鉴别出原地泥页岩、浊积岩和底流沉积三一相，其中后二者主要见于龙马溪组 ；三角洲前缘亚相以小河坝且为代表，已鉴别出试状砂粒滩、礁间泥微相；三角洲平面亚相以溶溪组为代表，已鉴别出分流河道及沼沼泽微相。该三角洲沉积的特征是入海河流流速低而流量大，泥沙含量高而粒级细小，在三角洲前 相似文献
13.
笔者通过对长江三角洲平原晚新生代钻孔SG7孔沉积物的粒度和磁性分析,揭示磁性矿物类型随时间的演变,探讨新构造运动、气候、海平面等对本区沉积物源、沉积环境的耦合作用。研究结果显示,上新世磁性强弱相间,且达到全剖面最强,磁性矿物为磁铁矿、磁赤铁矿、针铁矿和黄铁矿,反映本区气候暖湿,发育山间湖泊,沉积物主要来自周边白龙港玄武岩的风化产物;早更新世早期,磁性为全剖面最弱,以磁铁矿为主,反映在构造沉降作用下,发生物源改变,即主要来自贫铁的中酸性浅成岩或喷出岩,同时沉积物主要为冰期的河道相沉积,反映山间河流/冲积扇环境;早更新世晚期至晚更新世末,磁性显著增强且和沉积物粗细变化一致,粗颗粒沉积物中磁性矿物以变质岩来源的粗粒磁铁矿为主,细粒沉积物中磁性矿物见针铁矿、赤铁矿和黄铁矿,反映古地理环境逐渐向冲积平原、滨海平原演变;自晚更新世晚期出现细粒磁赤铁矿和磁铁矿,反映长江上游物源的加入。全新世沉积物磁性较更新世泥质沉积物显著增强,反映长江河口、三角洲环境。 相似文献
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Major part of the Holocene Ganges-Brahmaputra delta occupies the southern and southwestern part of Bangladesh with a smaller
part extending beyond the international boundary in the west. Five facies assemblages are documented in the lower deltaic
plain in five different depositional environments: levee or levee complex, bil or depression, abandoned meander belt, interdistributary
plain and estuarine plain. The thickness of the Holocene sediments ranges from 30 m to 70 m in the deltaic plain, usually
floored by the Pleistocene stiff clays, with the exception of the abandoned meander belt deposit where Holocene channel sand
deposited directly on the Pleistocene sand. Radiocarbon dates indicate that low-rate sedimentation has occurred in the northern
part, where 4-6 m thick sediments were deposited since the mid-Holocene, whereas 10-30 mthick sediments were deposited in
the southern part during the same span of time. In addition, significant coastal subsidence (3 mm/a on average), added by
sea-level rise (1.5 mm/a, conservative rate) occurs in the study area, which serves as a negative factor in degrading the
coastal plain of Bangladesh in the future, while taking into consideration the weaker sedimentation in the area. 相似文献
15.
A range of mineral magnetic measurements have been carried out on archaeological sediments from Orkney and Cyprus. In a soil profile from Orkney, a magnetic enhancement factor of over 200 is observed in susceptibility data between the bedrock and a Norse sediment. The magnetic enhancement is associated with an increase in superparamagnetic grains probably caused by burning. Until now it has proved difficult to confirm the presence of superparamagnetic grains in natural samples using room temperature magnetic measurements. However, clear differences are to be found between the hysteresis loops of various magnetic domain states, including superparamagnetism. An algorithm has been developed to unmix hysteresis loops in terms of constituent domain states of ferrimagnetic iron oxides. Unmixing 128 hysteresis loops of archaeological sediments has shown that the dominant domain state in all sediments is superparamagnetic. Remarkably uniform superparamagnetic grain sizes of between 80 and 95 Å were found for all 128 sediments. © 1999 John Wiley & Sons, Inc. 相似文献
16.
The development of soft‐sediment deformation structures in clastic sediments is now reasonably well‐understood but their development in various deltaic subenvironments is not. A sedimentological analysis of a Pleistocene (ca 13·1 to 15 10Be ka) Gilbert‐type glaciolacustine delta with gravity‐induced slides and slumps in the Mosty‐Danowo tunnel valley (north‐western Poland) provides more insight, because the various soft‐sediment deformation structures in these deposits were considered in the context of their specific deltaic subenvironment. The sediments show three main groups of soft‐sediment deformation structures in layers between undeformed sediments. The first group consists of deformed cross‐bedding (inclined, overturned, recumbent, complex and sheath folds), large‐scale folds (recumbent and sheath folds) and pillows forming plastic deformations. The second group comprises pillar structures (isolated and stress), clastic dykes with sand volcanoes and clastic megadykes as examples of water‐escape structures. The third group consists of faults (normal and reverse) and extensional fissures (small fissures and neptunian dykes). Some of the deformations developed shortly after deposition of the deformed sediment, other structures developed later. This development must be ascribed to hydroplastic movement in a quasi‐solid state, and due to fluidization and liquefaction of the rapidly deposited, water‐saturated deltaic sediments. The various types of deformations were triggered by: (i) a high sedimentation rate; (ii) erosion (by wave action or meltwater currents); and (iii) ice‐sheet loading and seasonal changes in the ablation rate. Analysis of these triggers, in combination with the deformational mechanisms, have resulted – on the basis of the spatial distribution of the various types of soft‐sediment deformation structures in the delta under study – in a model for the development of soft‐sediment deformation structures in the topsets, foresets and bottomsets of deltas. This analysis not only increases the understanding of the deformation processes in both modern and ancient deltaic settings but also helps to distinguish between the various subenvironments in ancient deltaic deposits. 相似文献
17.
《Quaternary Science Reviews》1999,18(4-5):541-548
Three main stages can be distinguished in the sedimentary development and geomorphological formation of the present delta plains on the Aegean coast of Turkey. The Early Holocene is characterized by post-glacial transgression and dependent sedimentation. The Middle Holocene was the period when sea level reached the present level, and apart from small fluctuations, stopped rising. Alluviation and deltaic progradation were prevalent during this transition period from marine to terrestrial environments. As for the Late Holocene, deltaic progradation slowed down and delta plains were covered by floodplain sediments. These characteristics can be observed in the same sequence throughout the Aegean coast of Turkey. 相似文献
18.
长江三角洲全新世地层中潮滩沉积磁性特征及其古环境意义 总被引：3，自引：1，他引：2
对长江三角洲北翼江苏南通地区NT钻孔（长60.9 m）进行了系统的环境磁学分析,并结合岩性特征、粒度、漫反射光谱（DRS）等手段,探讨了全新世早、晚期潮滩沉积的磁性特征及其古环境意义。NT孔自下而上可分为6层（U1~U6层）,其中U2层下部（49.9~44.8 m）和U6层（7.5~0.3 m）为潮滩沉积,具有较低的退磁参数S比值及较高的硬剩磁（HIRM）和SIRM/χ,表明反铁磁性矿物如赤铁矿、针铁矿等含量和比例较高。结合漫反射光谱（DRS）分析,发现U6层上部盐沼（1.5~0.3 m）赤铁矿和针铁矿富集,U2层下部的盐沼仅富集赤铁矿。这一差异与U2层和U6层形成的时期和沉积环境有关。U2层形成于晚更新世晚期至早全新世,且曾长期暴露地表,有利于赤铁矿的形成,其后随着海平面的持续上升,盐沼不断垂向加积,始终处于水下环境,不利于针铁矿的形成;U6层形成于晚全新世三角洲海岸的进积过程中,氧化还原相互交替的环境有利于针铁矿的形成,后期成陆后的成土作用生成了较多的磁赤铁矿和赤铁矿。研究表明,全新世三角洲发育过程中,不同时期形成的盐沼具有不同的磁性特征,磁性特征的研究可以提供潮滩沉积环境演变的信息,对三角洲古环境重建研究具有重要意义。 相似文献
19.
对长江三角洲地区7个晚新生代钻孔沉积物的岩石地层和磁化率特征进行详细对比,并进一步选择浦东机场孔（PD孔）进行了详细的岩石磁学测试,讨论了该地区的晚新生代沉积物物源的演变。结果显示沉积物磁性的4次显著变化： 1）各钻孔上新世磁性强弱差异明显; 2）早更新世早期本区普遍表现出弱磁性; 3）从早更新世中晚期至全新世,磁性强度一般随粒度粗细变化波动,即砂质沉积磁性强,泥质沉积磁性弱; 4）晚更新世晚期以来,细颗粒沉积物的磁性较明显增强。磁性参数分析显示上新世和早更新世早期磁性矿物晶体颗粒较细,早更新世中晚期-晚更新世以粗晶粒磁性矿物为主,全新世细晶粒磁铁矿再次占主导。我们认为上述磁性变化反映构造沉降控制下现代长江三角洲地区物源区的不断扩大。 相似文献
20.
亚洲内陆晚新生代干旱化历史及其驱动机制是非常重要的科学问题。选择天山北麓柴窝堡盆地南缘乌鲁木齐河剖面为研究对象,基于磁性地层年代学研究建立的时间标尺,分析了该剖面碎屑沉积物岩石磁学特征及其控制因素,进一步探讨了柴窝堡盆地晚新生代古气候特征。磁性地层年代学研究约束乌鲁木齐河剖面底界年龄为~6.8 Ma,顶界年龄为~3.3 Ma。详细的岩石磁学测量及漫反射光谱分析结果表明,乌鲁木齐河剖面沉积物中磁性矿物主要包括磁铁矿、赤铁矿等,磁学参数χlf、χARM、SIRM、S-100mT、S-300mT、 χARM/SIRM等在~6.3 Ma、~5.2 Ma存在明显变化,揭示磁性矿物粒度、含量等存在相应变化,如在~6.3 Ma前后,磁性矿物颗粒逐渐变粗、含量降低;在~5.2 Ma前后,磁性矿物颗粒逐渐变细后趋于稳定、含量逐渐增多。基于稀土元素分析、沉积粒度与磁学参数相关性分析,认为沉积物源与沉积物粒度不是导致乌鲁木齐河剖面磁学性质变化的主要因素,自~6.8 Ma以来逐步干旱化的气候条件可能是导致该剖面磁学特征变化的重要原因。基于漫反射光谱分析得到的红度与亮度数据结果也揭示了同样的古气候特征。 相似文献