碳氧同位素与海平面变化──以新疆柯坪地区上震旦统一奥陶系碳氧同位素剖面为例

由于沉积物的压实作用、上覆沉积物和水体重荷引起的地壳均衡响应和地壳运动等原因，使得我们无法获得稳定的参照点，致使海平面变化尚无直接测量方法．值得庆幸的是海平面变化引起沉积记录、同位素记录的变化，据此我们可以利用同位素记录和沉积记录来间接再现地质时期中海平面的变化．根据碳氧同位素记录重塑了新疆柯坪地区晚震旦世─奥陶纪海平面变化特点．     

天然气体水合物在地质作用过程中变化的探讨

天然气体水合物是一种准稳定态的物质, 对引起温-压条件变化的各种地质作用是非常敏感的.沉积与剥蚀、海平面升降、冰期与间冰期等地质过程改变着海底环境温-压状况, 控制了沉积物中水合物的形成、保存与分解.快速沉积(尤其是海底滑坡和泥火山喷发等带来的瞬间堆积)、海平面上升、高纬地区冰期等使海底环境朝着增压、降温的方向变化, 有利于气体水合物形成与保存; 而迅速剥蚀、海平面下降、上覆冰体移除引起水合物分解.水合物的分解可以是渐渐的气体溢出, 也可以是猛然的气体喷发, 这取决于温度上升及压力降低的速度.气体水合物的“爆炸式”分解在海底表面可留下“圆坑状”地貌特征.地质过程中同一地区频繁的温-压波动可引起水合物中乙烷成分相对增加.      

“泥质海岸带近现代地质环境与海平面变化研讨会”将于9月份在津召开

2011年9月中下旬,天津地质调查中心将举办"泥质海岸带近现代地质环境与海平面变化研讨会"。会议内容:(1)泥质海岸带晚更新世以来地质环境演化、(2)全新世海平面变化、(3")小冰期"结束以来自然进程与人类活动共同作用下的现代地质环境变化及海岸带演化趋势。届时将邀请来自中国、英国、美国、丹麦等国的多位专家围绕以上主题做专题学术报告,欢迎有兴趣的同行们届时与会。     

湘西北奥陶纪碳酸盐台缘的变迁与海平面升降

通过综合多方面的地质资料，包括岩性、沉积构造、生物的生态类型、碳酸盐台地的迁移以及坡折位置的变更等来判断湘西北地区奥陶经平面变化，在湘西北地区海水深浅变化、台地边缘迁移和坡折位置的变更表现出相似的规律，从而可勾画出海平面变化曲线，两河口阶和宝塔阶是海平面上升期，调 阶和五峰阶是海平面下降期，其间牯牛期有一次不匠海平面变化，该区三次海平面升降旋回与Ｒｏｓｓ于１９８８年所作的全球海平面变化旋基本一致。     

浙江乌镇幅1∶50 000区域地质图数据库

浙江乌镇幅（H51E008002）1∶50 000区域地质图数据库综合采用遥感解译、槽型钻揭露、地质钻探和物探等多种调查手段,查明了主干断裂的第四纪活动性,详细总结了各地层单位岩性组合特征和时空分布规律,恢复了工作区第四纪以来气候特征及海平面变化特征,将末次冰期以来古地理古环境、海平面变化曲线重建与杭嘉湖平原古人类遗迹分布及迁徙特征相结合,探讨末次冰期以来海平面变化对古人类活动及迁移的影响。图幅数据库包含5个地层单元、10个钻孔,数据量约为 293 MB,涵盖了浅表沉积物属性特征及第四纪松散层、隐伏基岩及断裂构造等多方面的综合信息,充分反映了杭嘉湖平原第四纪沉积基底特征、地层结构及沉积环境演化特征,丰富了长江三角洲第四纪研究内容,为区域工程地质、水文地质调查提供了基础地质支撑。     

国际大洋钻探全球海平面变化研究进展

国际科学大洋钻探计划对全球海平面变化问题的关注始于1980年代初,至今已在被动大陆边缘、孤立碳酸盐台地、混积台地边缘、平顶海山等不同类型海区执行了23个与海平面变化相关的专题航次,采集了大量的钻探资料,为全球海平面变化研究提供了关键信息。依据这些资料,重建了近100 Ma以来的全球海平面变化历史,检验了Exxon的层序地层模型和海平面假说,明确了海平面变化的地层响应,建立了南极冰盖演化与海平面变化的关系。尽管如此,科学大洋钻探海平面变化研究仍存在一些不足,如钻探区的地域代表性还不够多,全球海平面变化信息提取时难以消除其他地质因素(如构造沉降)的影响,海平面变化记录的精度有待提高,多种因素作用下地层结构对海平面变化的响应还需进一步研究,海平面变化机制特别是冰盖动力学对海平面变化的影响及暖期海平面变化的原因还认识不清。在当今气候变暖的大背景下,这些问题的解决有助于提升未来海平面变化趋势预测的可靠性。     

关于长阳组建组剖面的问题

《长江三峡地区珍贵地质遗迹保护和太古宙-中生代多重地层划分与海平面升降变化》(汪啸风,陈孝红,张仁杰等,2002,地质出版社——以下简称02专著)出版后,许寿永认为其中的泥盆系(张仁杰、冯少南等,P.131—172)和石炭系(冯少南,张仁杰等.P.     

地质历史时期海平面变化曲线的数学模型

地层层序是古海平面变化的信息记录载体, 有效容纳空间(C(t))是地层层序的堆积场所, 是海平面变化(L(t))、构造沉降(Y(t)) 和地质时间(t) 的函数.通过对上扬子地台西缘二叠—三叠系层序地层学研究, 在总结前人海平面变化曲线研究方法的基础上, 建立了海平面变化曲线的数学模型(数学地质模型和数学函数模型), 即首先创立海平面变化曲线的数学地质模型: C(t) =L(t)+Y(), 进而提出了海平面变化曲线的数学函数模型.运用该模型定量编制了上扬子地台西缘二叠—三叠纪海平面变化曲线.      

东海陆架盆地第三纪海平面变化

东海陆架盆地是建立西太平洋新生代海平面变化的关键地区。本文以层序地层和沉积体系分析为基础,利用微体古生物带化石资料,建立了东海陆架盆地第三系相对精度较高的年代地层格架。通过古生态分析、成因相及特征沉积构造分析和反射地震剖面的海岸上超分析,辅以地球化学参数变化研究,首次编制了东海陆架盆地第三纪海平面变化曲线。自第三纪以来,能识别的长周期二级旋回海平面变化4次,短周期三级旋回变化26次,相对海平面变化幅度在0-150m.分析发现海平面变化具有不对称性,即海侵作用速度大于海退作用速度。与Haq曲线对比也有较大的差异。     

现代珠江三角洲地区QZK4孔第四纪沉积年代

在地质环境变迁迅速的现代珠江三角洲地区,对于第四纪沉积的年代存在多种认识。结合南中国海的海平面变化记录,通过AMS14C和光释光测年发现,珠江三角洲腹地QZK4孔第四纪岩心底部最老年龄约为43.71ka BP。岩心记录的第四纪环境对南中国海海平面变化有着良好的响应:岩心下部陆相河流沉积和暴露风化层发育于末次冰期至早全新世的低海平面时期,上部滨海—河口湾沉积发育于早中全新世以来的高海平面时期。根据钻孔岩心的环境分析,推测现代珠江三角洲地区第四纪的底界可能较本钻孔记录的更老。     

Sedimentary Evolution and Transgressions of the Western Subei Basin in Eastern China since the Late Pliocene

Sedimentary sequences in the Subei Basin are complex and have been affected by interactions between the ocean and rivers since the Late Pliocene, including the Yellow River, Huaihe River, and the Yangtze River. This sedimentary evolution, in particular the timing of Pleistocene transgressions, has long been a matter of controversy owing to the lack of precise chronological evidence. The aim of this study is to explore the evolution of the sedimentary environment throughout the past 3.00 Ma in this region on the basis of a comprehensive analysis of particle size and foraminifera and ostracods collected in the TZK9 core from the Subei Basin combined with geochronological studies of magnetostratigraphy, AMS¹⁴C and optically stimulated luminescence(OSL). The results show that fluvial facies in the sedimentary environment from 3.00 to 1.01 Ma. There were fluvial facies and reflects six sea-level high stands from 1.01 to 0.25 Ma. The study area was affected by four large-scale transgressions since 0.25 Ma. The four marine sedimentary layers known as DU7(buried at 48–52 m), DU5(buried at 35–41 m), DU3(buried at 16–23 m), and DU1(buried at 2–4 m) are recorded in the MIS7(210–250 ka), MIS5, MIS3, and Holocene, respectively. The magnitude of the DU5 transgression was identical to that of the DU3 transgression, both were larger than the DU7 transgression, and the DU1 transgression was the weakest. The variation of transgression strength reflects the influence of global changes in sea level, tectonic subsidence, shell ridges, and sand dams. In the TZK9 core, we found evidence of seven sea-level high stands from the Early–Middle Pleistocene, and the first one caused by regional rapid subsidence and could be traced back to 0.83-0.84 Ma. The sea-level high stands and the age of the first one recorded above was different from other cores in eastern China, this was caused by the lack of absolute age control and the differences in paleotopography during this period. This study reconstructs sedimentary evolution, determines the transgression and its age, establishes the chronology since the Late Pliocene, and provides a scientific framework for further paleoenvironmental and tectonic studies. The results of this study highlight the important role that local tectonics and global sea level play in the sedimentary evolution and transgressions that have occurred in the western Subei Basin.     

黄河三角洲ZK1孔晚第四纪以来沉积层序演化及其古环境意义

对黄河三角洲ZK1孔粒度、岩性、微体古生物组合和14C年代进行了分析,探讨了研究区晚第四纪以来的沉积层序演化历史及其古环境意义。黄河三角洲的ZK1孔共发育三个海侵层,自下而上为深海氧同位素3期（MIS3）的第Ⅲ海侵层和第Ⅱ海侵层以及氧同位素1期（MIS1）的第Ⅰ海侵层,指示自氧同位素4期（MIS4）以来研究区共发生三次主要海平面波动。这三次海平面波动分别对应于渤海海侵、献县海侵和黄骅海侵。根据沉积记录信息,ZK1孔可分辨第Ⅰ海侵层的河口三角洲相（5.63~14.04 m）和滨岸浅海相（14.04~20.62 m）,第Ⅱ海侵层的滨岸浅海相（39.52~49.57 m）和河口三角洲相（49.57~ 51.52 m）,第Ⅲ海侵层的滨岸浅海相（76.00~83.63 m）和潮滩相（83.63~92.70 m）,均以特征的微体古生物组合和沉积相为标志。结合前人研究,阐明了本区自晚第四纪以来的海平面变化及沉积环境演变历史。     

大凌河河口地区中更新世晚期以来沉积环境演化

大凌河河口地区LZK06孔40m以浅岩心的沉积学、古生物学和年代学等综合研究以及该地区LZK02- 04钻孔资料,揭示了研究区中更新世晚期以来经历了两次海侵- 海退旋回,依次形成了中更新世晚期湖相/河流相 SymbolnB@ 晚更新世海相- 湖相/河流相 SymbolnB@ 全新世海相- 河流相地层。全新世早中期由于物源供给很少,研究区处于长达约10ka的饥饿滞留相沉积环境,平均沉积速率仅约0. 02~0. 05cm/a。全新世晚期约1500a cal BP以来,由于人类活动导致水土流失,河流输砂量增加,研究区开始了快速加积过程,平均沉积速率约0. 9~1. 2cm/a,下辽河平原被快速充填,开始成陆。与全球海面变化时空分布特征的对比,推断辽东湾的第II海相层发育于MIS 5- MIS 3早期,第I海相层发育于MIS 1阶段高海面时期。晚更新世以来频繁的海面升降是辽东湾泥质海岸带地层和环境演化的主要控制因素。     

MIS 3阶段以来河北黄骅北部地区海侵与气候期对比

依据渤海湾顶南侧、河北省黄骅北部地区4个钻孔岩芯样品微体古生物学、孢粉地层学研究以及沉积构造与地球化学背景分析,讨论了该地区MIS3阶段以来海侵期与气候期对比、海侵层中潮坪与浅海沉积单元的判别、沉积作用对孢粉和海侵记录的影响。依据海相世系微体生物出现确定的海侵层,可分为滨岸浅海～河口湾、潮坪、泻湖、分支河道、边滩、滨海低地、河间地～洪泛盆地等不同环境;含有孔虫或广盐海相介形类的地层,除了局部河流进积～退积作用,尚不能排除风、水、鸟的搬运,包括风暴潮的影响,并非是与海水体积变化有关的海平面变化;海侵层中的潮坪～浅海沉积单元才与海水深度有关,其他海水之上形成的地层所见海相微体生物,是地壳沉降背景下风暴潮和其他动力搬运的埋葬群,与海面变化无关,甚至仅是在东部沿海大平原构造沉降背景下河口位置向陆地移动的结果;海侵的发生与海域的扩大以及夏季风强度增大,物源区植被状况好转,造成海侵层出现乔木花粉,但是为异地埋藏。一般说来,还原背景下的沉积地层孢粉记录丰富;弱氧化～弱还原背景下的沉积地层孢粉相对较少,但也可能出现孢粉丰富的特例,氧化背景下沉积地层孢粉更稀少,全新世大暖期结束于约5kaB.P.。沉积学研究,包括对同期异相和突发事件沉积作用的理解,对晚第四纪研究是十分重要的。     

Pleistocene marine deposits in the coastal areas of Kola Peninsula (Russia)

On the basis of field data, datings from both electron spin resonance – and optically stimulated luminescence, and micro- and macrofauna, in addition to presence of diatoms, three Late Pleistocene marine units have been identified in the coastal areas of the Kola Peninsula. The stratigraphically lowest sequence is correlated to the Ponoi Beds and the Boreal transgression, attributed to the marine isotope stages (MIS) 5e to 5d in the White Sea depression and to MIS 5e to 5c in the Barents Sea. Thermophilic fauna and diatoms indicate normal water salinity and a water temperature above zero. The second marine unit, referred as the Strel'na Beds, can be correlated with the Early Weischselian transgression, termed the Belomorian transgression. With low water salinity and a water temperature similar or colder than the present times, Belomorian transgressions are reliably detected in the White Sea and are not clearly found in the Barents Sea. The results obtained from the sediments of the Ponoi and Strel'na Beds indicate a continuously existing marine reservoir from 130 to 80–70 ka ago (entire MIS 5) in the White Sea depression. The early Middle Weichselian Barents–Kara ice-sheet invasion and its recession might have caused the glacioeustatic Middle Weichselian (MIS 3) transgression, and the third Late Pleistocene marine sequence has been deposited in the regressing shallow cold sea with less saline waters. The results help in the understanding of the history of Late Quaternary ice sheets in North Eurasia and provide evidence for the debatable Early and Middle Weichselian marine events.     

河流输沙与中国海岸线变化

我国沿海地区构造升降使入海河流沉积物分布不均，９５％于构造下降地区入海，构造上升区接纳的河流泥沙不足５％，入海河流泥沙分布不均是我国海岸基本类型和海岸线变化差别的主要原因。在此基础上讨论了最大海侵的范围及时间，海岸线变化的趋势、速度和周期以及河流输沙对未来海岸线变化预测的影响。     

渤海湾西岸晚第四纪海相地层划分及地质意义

BT113孔和BT114孔是位于渤海湾西岸地区的2个80 m全取心钻孔。通过对钻孔岩心的岩性、沉积构造及生物组合等特征分析,结合AMS¹⁴C和OSL（光释光）测年结果,揭示中更新世晚期以来本地区主要发育3个海相地层：自下而上为中更新统上部的第三海相地层（简称“海三”）、上更新统的第二海相地层（简称“海二”）和全新统的第一海相地层（简称“海一”）,指示中更新世晚期以来研究区发生的3次主要海面波动。与全球海面变化曲线对比,海三,海二和海一分别发育于MIS（深海氧同位素阶段）7、MIS5和MIS1的高海面时期,说明渤海湾西岸中更新晚期以来地层记录的海面变化趋势与全球变化一致。与前人的传统认识不同,认为受全球海面及渤海海峡地貌共同影响,MIS3时期研究区并未发生大范围海侵。通过多个钻孔的对比分析,3个海相地层在渤海湾西岸地区的分布较广,具有良好的可对比性,不同钻孔之间同一海相地层的高程和厚度的较大差异指示本地区在晚更新世期间发生较强的差异性沉降活动。     

Structural and physiographic control on the Holocene marine sedimentation in the bay of Cadiz (SW Spain)

The Quaternary tectonic activity in the Gulf of Cadiz has considerably influenced the depositional regime and distribution of Holocene marine deposits. The aim of this work is to determine the nature of the recent sedimentary filling in the Bay of Cadiz sea bottom and adjacent continental shelf and to establish the main controlling factors on the Holocene marine sedimentation.

The sedimentary record indicates siliciclastic sedimentation supplied from the continent, with alternating episodes of high and low sedimentation rates. The recent sedimentary evolution of this marine area was controlled by the Late Quaternary eustatic fluctuations. Bathymetric, geophysical and drilling data have been employed to prepare a detailed isopach map of the non-consolidated recent sedimentary cover. Thickness distribution shows significant variations related to the infilling of former fluvial palaeochannels incised during the Late Pleistocene lowstand, and highly controlled by the structural neotectonic trends of faults and joints: NNW-SSE, NNE-SSW and ENE-WSW. The general distribution of isopachs in this area is clearly influenced by these morphostructural lines, which controlled the sedimentary processes during the Holocene. These results are coherent with the main regional neotectonic structures previously described in the nearby continental area, and confirm their prolongation towards the marine domain.     

基于沉积成因地化元素指标的闽北海湾晚更新世海侵地层辨识及其意义*

福建沿岸晚更新世地层中微体古生物化石较为缺乏,极大限制了对该区晚第四纪海侵过程的深入研究。针对这一问题,本研究以闽北2个海湾内的第四纪钻孔为研究对象,通过有孔虫化石以及沉积成因的地球化学元素(Sr/Ba、Mn/Fe)分析,结合三沙湾表层沉积物相应指标,探讨沉积成因的地球化学元素指示海侵地层的可行性。结果显示,2个海湾钻孔的晚第四纪地层中均发育3套疑似海相深灰色黏土层,其中开放海湾霞浦湾钻孔底部黏土层中缺失有孔虫,半封闭海湾三沙湾钻孔中有孔虫仅出现于顶部黏土层中。这3层黏土层的Sr/ Ba值远大于1,和现代潮滩—河口湾体系相近,且出现的海相沟鞭藻和自生黄铁矿为典型的海相地层特征。基于已有的OSL和AMS¹⁴C年龄框架,这3层海侵层分别对应于MIS5、MIS3和MIS1期,Sr/Ba和Mn/Fe均值从MIS5到MIS1期不断增大,结合现代潮滩-河口湾体系指标,表明从MIS5到MIS1期海侵强度的增加。由此可见,沉积成因地球化学元素指标可以有效辨识闽北海湾晚更新世海侵地层,这将有助于进一步了解该区晚第四纪海侵过程及其控制因素。     

Late Quaternary valley-fill succession of the Lower Tagus Valley, Portugal

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.