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综合钱塘江下切河谷SE4孔岩心观察和描述及粒度、孢粉、测年等分析数据,探讨了钱塘江下切河谷晚第四纪沉积环境和古气候演化,揭示了其气候变化机制下沉积响应的具体过程。研究表明SE4孔晚第四纪沉积物自下而上包括河床亚相、河漫滩亚相、古河口湾相、浅海亚相和现代河口湾相5套沉积。研究区晚第四纪以来古植被和古气候演化分为6个阶段:第一阶段植被类型为阔叶树为主的针阔混交林—草原,气候温和偏湿,沉积了河床和河漫滩亚相;第二阶段为落叶栎稍多的针阔混交林,气候温和湿润,沉积了古河口湾相和浅海亚相;第三阶段为针阔混交林,气候温暖湿润,浅海亚相沉积发育;第四至第六阶段植被类型经历了针阔混交林—草原、针阔混交林、针阔混交林—草原的交替,气候经历了温和偏干、温和偏湿、温和偏干的变化,现代河口湾相沉积发育。 相似文献
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本文根据杭州湾沿海平原大量的钻井、静力触探井和分析化验等资料，研究了下切河谷（钱塘江和太湖下切河谷）充填物的沉积建造和沉积相，以及浅层生物气藏分布特征。研究表明，末次冰期以来，随着海平面变化，杭州湾地区下切河谷演化经历了深切、快速充填和埋藏三个阶段。末次冰盛期，海平面下降的幅度大，增加了河流梯度、加强了下切作用，本区形成了钱塘江和太湖下切河谷，随后在冰后期被充填和埋藏，下切河谷的两侧为暴露地表的古河间地。根据岩石学、沉积结构和沉积构造特征，本区下切河谷充填沉积物表现为向上变细的沉积层序，可以划分为4个沉积相类型，有河床滞留沉积物到部分曲流河沉积体系的边滩沉积、河漫滩-河口湾沉积、河口湾-浅海沉积和河口湾沙坝沉积。在河漫滩-河口湾相沉积期间，由于海平面上升、潮流体系、沉积物供给和可容空间条件适合一个潮流沙脊体系的发育，该相中砂质透镜体可能代表下切河谷内发育的潮流沙脊。对于河口湾-浅海沉积和河口湾沙坝沉积而言，由于沉积条件不再有利，没有形成沙脊沉积。所有的商业性生物气都存储在下切河谷内河漫滩-河口湾砂质透镜体中。 相似文献
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以最新钻取的SE2孔沉积物为重点研究对象,对晚第四纪以来钱塘江下切河谷充填物的沉积特征和沉积相进行了精细研究,重建了研究区地层结构和层序地层格架,总结了强潮型钱塘江河口湾和下切河谷的沉积模式。钱塘江下切河谷充填物自下而上依次发育河床、河漫滩、古河口湾、近岸浅海和现代河口湾5种沉积相类型,表现为一个较完整的Ⅰ型层序,其内部层序界面、初始海泛面、最大海泛面、海侵和海退潮流侵蚀面、体系域内海侵面发育。钱塘江下切河谷充填物自海向陆可划分为海向段、近海段、近陆段和陆向段4段,各段沉积序列和海陆相互作用程度不同。在钱塘江下切河谷充填物中海陆过渡部位首次明确划分出了古河口湾相,并对其沉积特征和分布模式进行了初步探讨;其形成时间在9000 a BP左右,具有与现代河口湾不同的沉积特征,表现为中部为潮道砂体沉积,向陆渐变为受潮流影响的河流沉积,两侧被潮坪或盐沼沉积包围,沉积物在平面上自陆向海呈现粗-细-粗的分布模式。现代河口湾平面上自陆向海依次发育受潮流影响的河流沉积、粉砂质砂坎、潮道-潮流砂脊复合体和湾口泥质沉积区,沉积物呈现粗-细-粗-细的分布模式,与大多数河口湾常见的粗-细-粗的分布格局明显不同。 相似文献
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对长江三角洲晚第四纪地层沉积特征进行了精细研究,探讨了研究区层序地层格架,在此基础上分析了浅层生物气成藏条件、特征和分布规律。研究表明,长江三角洲晚第四纪发育3期下切河谷,形成了3套沉积层序;因后期河流的强烈下切破坏,早期沉积层序往往被剥蚀殆尽,仅残留下部的河床相粗粒沉积,造成不同期河床相的叠置;相对而言,末次冰期以来形成的下切河谷沉积层序以相对完整的沉积相组合被保存下来。长江三角洲浅层天然气是未经运移的原生生物气,其主要富集于末次冰期以来的沉积层序内,气藏为自生自储同生型的岩性圈闭。河口湾—河漫滩和浅海相泥质沉积物既是气源岩,又是盖层,后者可作为良好的区域盖层;河口湾—河漫滩和河床相砂质沉积物为主要储集层。因此,研究区晚第四纪多期下切河谷沉积层序有利于浅层生物气藏的形成,特别是晚期下切河谷内河口湾—河漫滩相砂质透镜体以及河床相砂体可作为优先勘探目标。 相似文献
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渤海湾西岸尔王庄地区钻孔岩芯、微体古生物、孢粉及14C测年等资料及联合地质剖面研究结果表明，末次盛冰期全球海平面下降使该地区形成下切河谷，冰后期海平面迅速上升引发的海侵造成古河谷的充填，依次形成河床相、河漫滩―河口湾相和三角洲相，与相邻的滦河扇三角洲下切河谷有差异，该下切河谷受海河水系控制，流向大致与古潮白河一致。其演化过程受海平面变化、构造运动和古气候等因素影响，经历了末次盛冰期深切、15~7 ka BP海侵期间河床相及河漫滩―河口湾相的充填和之后海退形成的三角洲相埋藏等三个阶段。 相似文献
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渤海湾西北岸是渤海湾沿岸砂坝-澙湖沉积体系组成部分,其沉积物蕴含着丰富的地质环境演变信息,是认识该地区气候环境和新构造活动的关键.通过对渤海湾西北岸QEJ01孔80 m以上地层沉积环境、孢粉分析及微体古生物研究,结合测年数据,根据定量古气候重建数据,探讨了本区中更新世中期以来特征时期的植被演替及环境演变,并对MIS6～MIS1各阶段渤海湾西北岸的气候及环境变化进行了区域对比.QEJ01孔450.40～377.14 ka,植被类型以针阔混交林为主,气候温暖干燥,沉积环境由河床逐渐演变为滨海湖泊;377.14～113.96 ka,气候相对寒凉湿润,植被类型以针阔叶混交林-草原为主,沉积环境以湖泊为主,后期为洪泛平原;113.96～98.84 ka,该时期气候波动频繁,以稀树荒漠草原为主,气候温凉湿润,河床发育;98.84～74.33 ka,气候温暖湿润,植被景观为针阔混交林-草原,降水量增加,沉积环境以漫滩湖泊和河床相为主;74.33～48.09 ka,气候异常寒冷干旱,以针叶林为主的稀疏-荒漠草原较发育;48.09～25.72 ka,植被类型为针阔混交林-草原,气候温暖偏湿;25.72～22.52 ka,气候寒凉干旱,植被为稀树-荒漠草原;22.52～3.87 ka,植被类型由常绿落叶阔叶林演变为针阔混交林-草原,气候温暖湿润,沉积环境以三角洲平原为主;3.87～0.0 ka,气候凉爽干旱,植被类型以针阔混交林为主.渤海湾西北岸平原为构造活动的活跃地带,自MIS5阶段以来,沉降中心呈现自北西向南东迁移,以及海侵层的发育程度,均受区域构造运动和气候环境变化的影响控制. 相似文献
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江苏南通地区晚第四纪下切河谷沉积与环境演变 总被引：1，自引：0，他引：1
采用层序地层学基本原理,以海平面升降旋回为主线,根据钻井岩芯、古生物、测年和分析化验等资料,探讨了江苏南通地区晚第四纪地层层序、层序界面、沉积特征及沉积环境的演变。结果表明,研究区晚第四纪发育三期下切河谷,形成了三套沉积层序,自下而上三个层序的地质时代分别相当于晚第四纪早期、晚第四纪中期和晚第四纪晚期。由于后期河流的强烈下切破坏,早期沉积层序往往被剥蚀殆尽,仅残留下部的河床相粗粒沉积,造成不同期河床相的叠置;相对而言,晚第四纪晚期形成的下切河谷沉积层序以不同的沉积相组合被保存下来,自下而上划分为河床、河漫滩、河口湾、浅海和三角洲5种沉积相类型,表现为一个较完整的沉积层序。晚第四纪晚期下切河谷底界面,是末次冰期海面下降,河流下切形成的侵蚀面,与河间地古土壤层顶面的沉积间断面同属一个地史期的产物,一起构成区域不整合面,界面上下岩性突变,其上的冰后期地层属同一个海平面变化旋回,可互相对比,因而具有年代地层学意义。三期下切河谷层序的套叠结构表明,晚第四纪以来,研究区存在三次"低海面-海侵-高海面-海退"周期性海面变化。 相似文献
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末次盛冰期低海平面期间,长江三角洲地区可划分为2个古地理单元：古河谷和古河间地。下切河谷底部侵蚀面和古河间地顶面构成了冰后期海侵沉积旋回的底界面,它相当于层序地层学中的层序界面。位于河口湾-浅海相中的最大海侵面将冰后期海侵沉积旋回分为其下的海侵层序和其上的海退层序。随着δ18O 3期的海平面下降,长江开始下切,至δ18O 2期低海面时形成巨大的下切河谷。冰后期海平面上升引发的海侵造成了长江古河谷系的充填和河床、河漫滩－河口湾和部分河口湾－浅海相的形成,尔后的进积产生了部分河口湾－浅海相及三角洲相等。溯源堆积是产生下部河流沉积单元的主要过程,其中河漫滩沉积中出现的潮汐层理和少量小个体有孔虫说明了海洋因素的影响,河口湾－浅海相泥质沉积主要形成于最大海侵之时,三角洲的进积则产生了具有多期河口坝的三角洲。古河间地表面的硬粘土层经历了沉积和成壤作用交替、持续成壤作用和早期成岩作用,它们大致分别对应于δ18O 3期、δ18O 2期和δ18O 1期,硬粘土层中留下了这3种作用的烙印。长江三角洲古河间地的古土壤母质属河漫滩相。持续成壤阶段河流基面和地下水位均较低,年降雨量约为500～800 mm,相当于现今的温带地区,干湿周期变化明显,地下水升降频繁。所有这些表明,当时并非干旱气候。 相似文献
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近年来,在浙江省北部钱塘江河口湾地区发现并开发了大量的晚第四纪浅层生物气藏。末次盛冰期,全球海平面的下降使河流梯度增加,下切作用增强,导致钱塘江下切河谷的形成。下切河谷内的沉积序列从下到上可划分为4种沉积相类型,分别为河床相、河漫滩-河口湾相、河口湾-浅海相和河口湾砂坝相。 所有的商业浅气田和气藏都分布于太湖下切河谷和钱塘江下切河谷及其支谷的河漫滩-河口湾相砂体中。钱塘江下切河谷的河漫滩-河口湾砂体埋深30～80 m,厚3～7 m,被非渗透的黏土包围,可能代表了下切河谷内分布的潮流沙脊。快速堆积的河口湾-浅海相沉积物为生物气藏的形成提供了充足的源岩和良好的保存条件。 河漫滩-河口湾相的黏土层为研究区浅层生物气藏的直接盖层,主要分布在下切河谷内,其埋深、残留地层厚度和孔隙度范围分别为30～80 m、10～30 m和42.2％～62.6％。河口湾-浅海相的淤泥层为间接盖层,覆盖了整个下切河谷,其埋深、残留地层厚度和孔隙度范围分别为5～35 m、10～20 m和50.6％ ～53.9％。黏土层和淤泥层的孔隙水压力远大于下伏砂体的孔隙水压力,其差值可达0.48 MPa。在储集层和盖层分界面即浅气藏的顶部,孔隙水压力值达到最大。黏土层和淤泥层的孔隙水压力可以超过砂质储集层中气体压力和孔隙水压力之和。黏土和淤泥盖层的高孔隙水压力可能是浅层生物气被完全封闭住的最重要因素。直接盖层的封闭能力比间接盖层要好。黏土层和淤泥层的孔隙水压力消散时间很长,有时候很难达到稳定状态,这表明黏土层和淤泥层的渗透性差、封闭性好。随着埋深的增加,其压实程度和封闭性能增加。与黏土层和淤泥层相比,砂层的孔隙水压力消散较快,很容易达到稳定状态,而且消散时间与埋深无关,表明砂层渗透性好、封闭性差。气体一旦进入砂层,孔隙水就不能有效释放,导致砂层的孔隙水压力消散时间比黏土层和淤泥层的要长,这可能与生物气在孔隙水压力释放后的快速补充有关。 相似文献
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The Kathmandu and Banepa Basins, Central Nepal, are located in a large syncline of the Lesser Himalayas. The Older Kathmandu Lake evolved during the Pliocene and early Pleistocene; the Younger Kathmandu Lake, which is the focus of this study, is infilled with late Quaternary sediments. Three formations, arranged in stratigraphical order, the Kalimati, Gokarna and Thoka Formations formed during the infilling stage of this lacustrine basin. Structural and textural sedimentological analyses, a chemical survey across the basin and mineralogical investigations of fine‐grained sediments form the basis of this palaeogeographical study. The basin under investigation was covered by a perennial freshwater lake before 30 000 yr BP. The lake was infilled with alluvial and fluvial sediments delivered mainly from the mountains north of the basin. A fairly low gradient was favourable for the formation of diatomaceous earths, carbonaceous mudstones and siltstones, which were laid down in the centre of the lake and in small ponds. Towards the basin edge, lacustrine sediments gave way to deltaic deposits spread across the delta plain. Crevasse splays and anastomosing rivers mainly delivered suspended load for the widespread siltstones and mudstones. The proximal parts of the alluvial–fluvial sedimentary wedge contain debris flows that interfinger with fine‐grained floodplain deposits. Three highstands of the water‐level (>30 000 yr BP, 28 000–19 000 yr BP, 11 000–4000 yr BP (?)) have been recognised in the sedimentary record of the younger Kathmandu Lake in the Late Quaternary. Second‐order water‐level fluctuations are assumed to be triggered by local processes (damming by tectonically induced landslides). First‐order water‐level fluctuations are the result of climatic changes. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
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两护村ZKC1孔位于洞庭盆地安乡凹陷的东南部,孔内第四系(底部跨上新世)厚达294 m,为河流和湖泊沉积,自下而上依次为上新世—早更新世华田组、早更新世汨罗组、中更新世洞庭湖组、晚更新世坡头组以及全新统等。对ZKC1孔第四系进行了详细的孢粉分析,自下而上划分出16个孢粉组合带。ESR年龄和孢粉组合及其反映的气候特征指示华田组下段形成于上新世末。根据孢粉组合特征,结合构造—沉积演化和区域气候背景,重塑洞庭盆地上新世末以来的气候演化过程:上新世末期由孢粉带Ⅰ和Ⅱ指示具暖干气候。早更新世经历了凉干(孢粉带Ⅲ、Ⅳ)→暖湿间凉干(孢粉带Ⅴ～Ⅶ)→冷干间温湿(孢粉带Ⅷ～Ⅹ)→暖较湿(孢粉带Ⅺ,Ⅻ)的气候演变过程。中更新世早期无孢粉样品(洞庭湖组下部砾石层),其沉积环境暗示冷干气候条件;中期由孢粉带ⅩⅢ反映出暖稍湿的气候特征;晚期因构造抬升缺失沉积,同期湿热化事件指示暖湿气候。晚更新世早期缺乏沉积,据区域对比应为寒冷气候;中期由孢粉带ⅩⅣ指示温较湿的气候特征;晚期缺失沉积,系寒冷气候下区域海平面下降所致。全新世经历了暖稍湿(孢粉带ⅩⅤ)→暖稍干(孢粉带ⅩⅥ)的演变。上述气候演变过程与ZKC1孔化学蚀变指数曲线反映的气候演变过程以及中国东部第四纪气候演化基本吻合。以孔深140 m为界,上部孢粉数量显著高于下部,种属也更为丰富。这一变化很可能对应于一次重要的地质事件,其成因有待今后深入研究。 相似文献
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通过对浙江余姚河姆渡—田螺山遗址附近的HMD1501和HMD1502两个钻孔的微体古生物学研究,揭示了该地区全新世以来的植被演变、气候变化、海平面变迁及人类活动。孢粉、海相沟鞭藻、淡水藻类及有孔虫内衬的记录表明: (1)在早全新世(对应于镇海组下部),植被群落属于常绿阔叶和针叶混交林,气候温暖潮湿,研究区属于海侵阶段。(2)在中全新世(对应于镇海组中部),植被群落虽仍为针阔叶混交林,但气候转为温和湿润,研究区仍属于海侵阶段。(3)由于人类活动的进一步加剧,在晚全新世(对应于镇海组上部)的植被群落中草地的面积也随之扩大,并在滨海地区开始有一些以莎草科为主的沼泽地形成,植被群落属于针阔叶混交林—草地,气候更加凉爽干燥,研究区转为海退阶段。(4)在~7235—3327 cal. yr B.P.期间,草本花粉的含量激增,特别是一些粒径不小于35,μm 的禾本科栽培作物花粉的含量增加,说明此时人类活动开始增强,河姆渡—田螺山遗址附近出现较多的水稻种植区。 相似文献
14.
Although evidence for Quaternary environmental changes in the Arabian Peninsula is now growing, research has mostly been conducted in the United Arab Emirates (UAE) and in the Sultanate of Oman. There have been virtually no recent studies in Saudi Arabia, especially in the central region such as around Al‐Quwaiayh. In this area there are a series of outwash plains developed along the eastern edge of the Arabian Shield that formed in the late Quaternary. Four sedimentary sections, which are representative of the deposits that have accumulated, have been studied and five luminescence ages obtained. These are the first luminescence ages acquired from Quaternary sediments in central Saudi Arabia. The preserved fluvial deposits in the study area have formed during humid events at ca. 54 ka, ca. 39 ka and ca. 0.8 ka. In more recent times aeolian sands have been encroaching on to the distal parts of the outwash plains. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
15.
对河北平原中部保定西伯章厚20.74 m的剖面进行实测,系统采集粒度和光释光（OSL）样品进行分析,以期获得其沉积特征及环境演变信息。光释光测年显示该剖面为102~8.69 ka的沉积,时代属于晚更新世到早全新世。岩性和粒度分析表明该剖面为曲流河冲积沉积,可以进一步划分为河道沉积和河漫滩沉积。河道沉积以含云母碎片的中粗砂为主,发育斜层理,频率曲线以正偏双峰频率曲线为主,分选中等到较差,概率累积曲线以跳跃组分为主的两段式为主。河漫滩沉积以黏土质粉砂为主,含保存良好的腹足类化石和钙质结核,频率曲线以负偏双峰为主,分选差,概率累积曲线以悬浮组分占比大的两段式为主。C-M图显示该剖面以均匀悬浮沉积为主,属典型曲流河沉积。实测剖面与黄土剖面对比分析显示西伯章剖面可以分为三个阶段,下部20.74~16.14 m为末次间冰期晚期沉积,气候温暖湿润,以粉砂质沉积为主;中部16.14~3.18 m为末次冰期沉积,气候干冷,沉积物显示细—粗—细的特征,与末次冰期早冰阶—间冰阶—盛冰阶一一对应;上部3.18~0.2 m为冰后期沉积,与末次间冰期晚期沉积环境类似,以黏土和黏土质粉砂沉积为主。粒度成因分析揭示了河北平原中部保定凹陷区晚第四纪沉积环境主要为河流冲积环境,粒度阶段性分布特征是晚第四纪以来冰期-间冰期气候的物质响应。 相似文献
16.
17.
V CHOWKSEY D M MAURYA PARUL JOSHI N KHONDE ARCHANA DAS L S CHAMYAL 《Journal of Earth System Science》2011,120(6):979-999
The Kachchh Mainland Fault (KMF) is a major E–W trending seismically active fault of the Kachchh palaeorift basin whose neotectonic
evolution is not known. The present study deals with the eastern part of the KMF zone where the fault is morphologically expressed
as steep north facing scarps and is divisible into five morphotectonic segments. The Quaternary sediments occurring in a narrow
zone between the E–W trending KMF scarps and the flat Banni plain to the north are documented. The sediments show considerable
heterogeneity vertically as well as laterally along the KMF zone. (The Quaternary sediments for a northward sloping and are
exposed along the north flowing streams which also show rapid decrease in the depth of incision in the same direction.) The
deposits, in general, comprise coarse as well as finer gravelly deposits, sands and aeolian and fluvial miliolites. The Quaternary
sediments of the KMF zone show three major aggradation phases. The oldest phase includes the colluvio-fluvial sediments occurring
below the miliolites. These deposits are strikingly coarse grained and show poor sorting and large angular clasts of Mesozoic
rocks. The sedimentary characteristics indicate deposition, dominantly by debris flows and sediment gravity flows, as small
coalescing alluvial fans in front of the scarps. These deposits suggest pre-miliolite neotectonic activity along the KMF.
The second aggradation phase comprises aeolian miliolites and fluvially reworked miliolites that have been previously dated
from middle to late Pleistocene. The youngest phase is the post-miliolite phase that includes all deposits younger than miliolite.
These are represented by comparatively finer sandy gravels, gravelly sands and sand. The sediment characteristics suggest
deposition in shallow braided stream channels under reduced level of neotectonic activity along the KMF during post-miliolite
time evidenced by vertical dips of miliolites and tilting of gravels near the scarps. The tectonically controlled incision
and dissection of the Quaternary deposits is the result of neotectonic activity that continues at present day. The overall
nature, sedimentary characteristics and geomorphic setting of the sediments suggest that the KMF remained neotectonically
active throughout the Quaternary period. 相似文献
18.
C. Kasse S.J.P. Bohncke G. Gábris 《Proceedings of the Geologists' Association. Geologists' Association》2010,121(2):180-194
The Weichselian Late Pleniglacial, Lateglacial and Holocene fluvial history of the middle Tisza valley in Hungary has been compared with other river systems in West and Central Europe, enabling us to define local and regional forcing factors in fluvial system change. Four Weichselian to Holocene floodplain generations, differing in palaeochannel characteristics and elevation, were defined by geomorphological analysis. Coring transects enabled the construction of the channel geometry and fluvial architecture. Pollen analysis of the fine-grained deposits has determined the vegetation development over time and, for the first time, a bio(chrono)stratigraphic framework for the changes in the fluvial system. Radiocarbon dating has provided an absolute chronology; however, the results are problematic due to the partly reworked character of the organic material in the loamy sediments. During the Late Pleniglacial, aggradation by a braided precursor system of the Tisza and local deflation and dune formation took place in a steppe or open coniferous forest landscape. A channel pattern change from braided to large-scale meandering and gradual incision occurred during the Late Pleniglacial or start of the Lateglacial, due to climate warming and climate-related boreal forest development, leading to lower stream power and lower sediment supply, although bank-full discharges were still high. Alternatively, this fluvial change might reflect the tectonically induced avulsion of the River Tisza into the area. The climatic deterioration of the Younger Dryas Stadial, frequently registered by fluvial system changes along the North Atlantic margin, is not reflected in the middle Tisza valley and meandering persisted. The Lateglacial to Holocene climatic warming resulted in the growth of deciduous forest and channel incision and a prominent terrace scarp developed. The Holocene floodplain was formed by laterally migrating smaller meandering channels reflecting lower bank-full discharges. Intra-Holocene river changes have not been observed. 相似文献