珠江三角洲西缘晚第四纪沉积演化和最大海侵古岸线的重建

第四纪以来,受全球气候和海平面变化影响,海岸带地区发生了一系列强烈的海陆相互作用和海侵—海退等地质事件,包含了丰富的沉积环境演化和海平面变化等信息.选用珠江三角洲西缘台山地区的30个地质钻孔,通过14C、光释光、地球化学特征、底栖有孔虫、磁化率数据,建立了晚更新世以来的地层框架,重建了最大海侵古岸线的位置.研究结果表明...     

Quaternary interaction of cryospheric and oceanographic processes along the central‐east Greenland margin

The east Greenland margin has been influenced by oceanographic and cryospheric processes since the late Miocene, when the southwards flow of the East Greenland Current (EGC) initiated and ice sheets first advanced across the margin. However, the relative importance of these processes, and their influence on the sedimentation of the margin through time remains poorly understood. High‐resolution single‐channel seismic, chirp sub‐bottom profiles and swath bathymetry data were acquired along the middle/lower slope and proximal basinal area off Liverpool Land, central‐east Greenland margin. In this study, seismic‐stratigraphical and morphological analyses allowed us to distinguish between the major sedimentary processes that influenced this margin during the Quaternary. The stratigraphical architecture reveals mass transport deposits (MTDs) related to glacially influenced down‐slope sedimentation. These are intercalated with buried contourite systems associated with bottom‐current controlled along‐slope sedimentation. The distribution of the MTDs suggests the influence of two distinct ice‐stream systems. Initial phases of down‐slope deposition during the early‐middle Quaternary appears to be related to distal deposition fed by an ice stream from the Scoresby Sund area in the south. Shallow sedimentary processes, together with morphological analysis of the sea floor, show that the most recent activity of down‐slope processes during the latest Quaternary has occurred in the north, linked to an ice stream from the Kong Oscar Fjord area. These observations document a temporal shift in the relative dominance of the Scoresby Sund and Kong Oscar Fjord ice‐stream systems. The glacial influence on the margin has been interrupted by periods of stronger activity of along‐slope bottom‐current flow, demonstrating that the EGC periodically controlled sedimentation on the continental margin.     

惠民凹陷南坡古中生代沉积体系特征及时空演化

笔者通过胜利油区惠民凹陷南坡地区古生代地层的沉积相发育与分布特点的研究，并结合区域构造运动，揭示了该地区古生代奥陶纪到中生代侏罗纪的构造和沉积体系发展演化规律。结果表明，整个研究区在早古生代发育了一套碳酸盐潮坪体系，晚古生代为海陆过渡的三角洲沉积体系，中生代为一套陆相河流体系。三角洲体系又包括了石炭纪的海相三角洲和二叠纪的陆相湖泊三角洲。该区在古生代和中生代经历着多期次、多类型的构造－沉积演化，从整个演化过程来看，总体上体现了从海到陆的过程。在空间上，除了在早古生代沉积相对稳定外，晚 古生代和中生代均表现了较明显的沉降差异性。     

东北地区二叠纪沉积特征及原型盆地分析

东北地区二叠系分布广泛,沉积相类型主要为半深海相、滨浅海相、滨浅湖相和半深湖相等。早二叠世-中二叠世东北地区主要处于大陆边缘浅海沉积环境,面积大,沉积中心位于南部温都尔庙-西拉木伦河东西向条带区。晚二叠世东北地区为大型坳陷型盆地,东北地区各缝合线均已闭合,随着地壳抬升,海水退出,大部分地区为陆相沉积,局部有残留海相沉积,总体上具有从早二叠世到晚二叠世由海相向陆相逐渐转变的规律。西拉木伦河缝合带对晚古生代沉积起控制作用,在二叠纪整个缝合带由西向东逐渐拼合,直至晚二叠世,两板块拼合完成,闭合时间具有西早东晚的特点。     

河北唐山西部PZK14孔晚新生代沉积演化特征

为查明唐山西部平原区晚新生代以来松散堆积物的沉积演化特征,依托鸦鸿桥幅1∶5万区域地质调查工作,对唐山西部PZK14孔进行色度、粒度、视电阻率测井、自然伽马测井等研究,划分沉积相并计算各时段的沉积速率,结果表明：该地区新生代晚期主要发育湖泊相、三角洲相和河流相。早更新世初始发育三角洲相,随着气候转暖,古滦河冲积扇退积,三角洲相转变为河流相;早更新世中—晚期,发育3个湖泊-三角洲相沉积旋回;中更新世发育一个湖泊-三角洲相沉积旋回;晚更新世初沉积了巨厚的湖相层,随着气候转冷,渤海湾沿岸海侵结束,湖盆开始萎缩,转变为河流相;全新世则以河间洼地沉积为主。沉积速率-年龄曲线表明：第四纪以来构造作用对该地区沉积速率控制较弱,气候为影响沉积相发育的主要因素。第四纪各个时期的沉积速率均较快,奥杜威极性亚时(1.95～1.77 Ma)沉积速率最大,约为194.0 m/Ma; 2.52～1.95 Ma沉积速率最小,约为111.2 m/Ma。研究成果对恢复该区域古地理演化、水工环地质勘查等具有重要意义。     

闽粤台琼海岸大震构造的定量标志：兼论定性标志

本文论述闽粤台琼海岸大震区的莫霍面隆起幅度、第四纪抬升幅度和晚全新世海岸抬升幅度为主的大震构造的定量标志,以及某些定性标志。另外,对地表隆起带的定量标志研究方法作了简要地叙述。我国台湾是世界著名的新构造带和大震区.福建、广东和海南各有一个海岸大震区。这些大震区海岸必然遗留下许多地壳活动的遗迹。其中海岸活动遗迹,由于海平面作标志面,则可确定某一个时期的海岸升降幅度,甚至正反向的升降周期和升降速率。     

下扬子区三叠纪古地理演化

下扬子区在三叠纪期间接受了早-中三叠世海相碳酸盐沉积、中-晚三叠世海陆交互相和陆相湖沼沉积.沉积相带的空间分布和古地理格局的变迁明显地受到区域构造的控制.区内盆地发育与演化是在华南板块与扬子板块、扬子板块与华北板块相互作用的背景下进行的.早-中三叠世末期的印支运动是下扬子区构造-古地理格局改变的决定性因素,使下扬子海盆闭合,沉积类型由海相沉积变为陆相沉积.下扬子区三叠纪古地理的演化特征也为板块碰撞提供了沉积证据.     

Utility of clay Minerals in the Determination of Sedimentary Transport Patterns in the Bay of Cadiz and the Adjoining Continental Shelf (SW-Spain)

The contents and the distribution of clay minerals in modern sediments of the Cadiz bay and the continental shelf have been studied aiming to establish the sedimentary exchange model and the pathways followed by the clay fraction between the bay and the adjoining continental shelf. The most abundant clay minerals in the muddy sediments consist mainly of illite, smectite, interstratified illite-smectite, kaolinite and chlorite. The application of factor analysis method (PCA) to clay minerals data are considered to be useful in the determination of sedimentary transport patterns. The data from clay mineral assemblages, and their distribution map, make possible to establish the fine sediments transport paths in the study area using clay mineral as natural tracers. This model of transport takes in consideration the facies distribution, the supplies sources and the way of fine sediments are incorporated to the marine environment.

Two flows paths have been established: the outflows coming from Cadiz bay and the littoral zones; and the inflows coming from external marine zones of the bay. These flows are controlled by tidal currents and the morphology of the coast. The action of surge and the marine currents, specially the Atlantic Surface Water flow, are also important in the transport of fine sediments coming from sources located to the north of the study zone.     

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.     

Holocene stratigraphy and geomorphological evolution of the Aegean coastal plains of Anatolia

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.     

Tectonic Uplift of the Yili Basin during the Last Stage of the Late Pleistocene: Evidence from ESR and OSL Dating of Sediments in the Huocheng Area, Xinjiang

The Quaternary sediments in the Yili Basin can serve as archives for studying the Cenozoic basin–mountain relationship. In this study, based on typical natural sections and boreholes, the surficial sediments of the Huocheng area were studied, and their sedimentary ages were obtained using the optically stimulated luminescence(OSL) and electron spin resonance(ESR) dating methods. These dates, combined with changes in the sedimentary facies, provided details of the neotectonic movement in the Yili Basin and adjacent areas. By dating sediments from five sections and three boreholes, we determined that the surficial sediments of the Huocheng area were mainly formed in the Late Pleistocene, with scattered instances of Holocene sediments. The surficial sediments mainly consisted of alluvial fan facies, fluvial facies, lacustrine facies, and desert facies. Based on the activity on the Hongshanzui fault and the northern margin fault of the Wusun Mountains, the Huocheng area was uplifted synchronously with the Tianshan Mountains during the last stage of the Late Pleistocene, causing the desert facies sediments to be superimposed on the former paleo–lake sediments.     

The sandy channel-lobe depositional systems in the Gulf of Cadiz: Gravity processes forced by contour current processes

The sedimentation in the Gulf of Cadiz (NE Atlantic Ocean) is significantly controlled by the Mediterranean Outflow Water (MOW). Along its pathway onto the continental slope, the MOW is canalized by contourite channels, some of them feeding gravity sandy channel-lobe depositional systems firstly recognized in previous study [Habgood et al., 2003. Deep-water sediment wave fields, bottom current sand channels and gravity flow channel-lobe systems: Gulf of Cadiz, NE Atlantic. Sedimentology 50(3), 483-510.].Using very high resolution acoustic data and cores, a detailed characterization and a new evolution pattern of these channel-lobe depositional systems is established. Complex internal geometry of the lobes shows several depositional units revealing a polyphase evolution of these systems, with a general progradation punctuated by retrogradation and avulsion phases. A gravity origin controlled by contouritic processes and climatic changes is demonstrated for the feeding and the evolution of these sandy channel-lobe depositional systems. Climate oscillations, via the MOW variations, act as a major forcing of the activity of the channel-lobe depositional systems during the Late Quaternary.     

Some regional indicators of the Tertiary–Quaternary geodynamics in the paleocoastal part of the Bengal basin (India)

Sedimentary processes in the paleocoastal part of the Bengal basin that occured in the Tertiary and Quaternary have been addressed. Three indicators were used: sedimentary bedding forms, microstructure of the sediment, and trace fossils. Various forms of sedimentary structures developed under the influence of dynamic geomorphic processes in the study area in the Quaternary. The microstructure analysis of the sedimentary materials was made by two methods: microphotography and Digital Color Analysis (DCA). The microstructure analysis shows that the geomorphic process remained very dynamic in the Quaternary, influencing the form, thickness, and mineral composition of the sediment strata. The enrichment of the sediments in heavy minerals evidences either oscillating or combined flow sedimentation, while under stable conditions light-mineral deposition took place. The digital data of microfabric study by the DCA method also show that larger particles deposited in the oscillating or high-flow environment and evidence a greater amount of heavy minerals like ferruginous materials. Trace fossils found in the sediments of this area also strongly support the concept that the environment remained dynamic during the Tertiary and Quaternary. The Late Tertiary deposition shows that, during these periods, the sediments were transported from tide-dominated marine coast with low flow energy, which is typical of hot and humid conditions. From Late Tertiary to Early Quaternary, the macrotidal coast became mesotidal (wave-dominated). The second phase is the Middle Pleistocene, when the environment was stable, favoring the continuous deposition of finer particles under low- to medium-flow energy conditions. The third phase, the Recent, is marked by the shoreline shift and modification of the environment. In the Early–Middle Holocene, the shoreline started to shift, which modified the geomorphic conditions of this place from coastal to estuarine and, finally, inland fluvial.     

江汉盆地新构造运动对第四纪沉积环境演化的制约

以江汉盆地周缘区露头剖面及沉积中心区第四纪钻孔岩芯资料为研究载体,通过第四纪地层横向对比分析,恢复了江汉盆地第四纪各时期的沉积环境,讨论了江汉盆地新构造运动的特点及对江汉平原第四纪沉积环境演化的控制作用。研究表明,早中更新世江汉盆地大部处于掀升状态,盆地周缘地带遭受剥蚀;晚更新世地壳显现不等量运动,盆地自北西向中南部表现为徐缓掀升与下沉并存;全新世,盆地周缘及波状地形区掀升和低平原区强烈沉降进一步突显,全新世中晚期湖泊范围达到最大。      

The impact of glaciation, river-discharge and sea-level change on Late Quaternary environments in the southwestern Kara Sea

Sedimentary records from the southwestern Kara Sea were investigated to better understand the extent of the last glaciation on the Eurasian Arctic shelf, sea-level change, and history of the Ob' and Yenisey river discharge. Sediment-core and seismic-reflection data indicate that the Quaternary depositional sequence in the southwestern Kara Sea consists of glacial, glaciomarine, and marine sedimentary units. Glaciogenic sediments in the deep Novaya Zemlya Trough are presumably related to the Last Glacial Maximum (LGM), whereas further east they may represent an earlier glaciation. Thus, it is inferred that the southeastern margin of the LGM Barents-Kara ice sheet was contained in the southwestern Kara Sea east of the Novaya Zemlya Trough. Changes in mineralogical, foraminiferal, and stable-isotopic composition of sediment cores indicate that riverine discharge strongly influenced sedimentary and biotic environments in the study area during the Late Weichselian and early Holocene until ca. 9 ka, consistent with lowered sea levels. Subsequent proxy records reflect minor changes in the Holocene hydrographic regime, generally characterized by reduced riverine inputs.     

福建九龙江河口第四纪沉积物特征及沉积环境演变

根据福建九龙江河口ZK1孔及ZK7孔沉积物AMS(Accelerator Mass Spectrometry,加速器质谱测年技术) ¹⁴C测年、古地磁和剖面特征分析,进行该地区的第四纪地层划分,依据粒度特征,结合磁化率、微体古生物和Sr/Ba等环境代用指标进行沉积相分析,重建了该区晚第四纪的古环境演变历史。结果表明:(1)九龙江河口第四纪沉积时代为晚更新世中期至全新世晚期。(2)上更新统沉积可划分为下部龙海组洪冲积相和上部东山组河漫滩相沉积,中间有10 ka的沉积间断,末次冰期又再遭受风化剥蚀作用,推测有5～6 ka的风化剥蚀期。(3)全新统最早沉积年代约为14 ka BP,依次出现河口湾相、河口砂坝—分汊河道相、潮滩相沉积。(4)根据年代学数据和沉积相变化,重塑了该区晚第四纪沉积环境变化过程,为该区的第四纪研究和工程地质工作提供了参考依据。     

关于福建和台湾晚更新世存在陆桥之说质疑

据近年来福建沿海大陆架和相邻的浙江宁波发现的晚更新世海相、海－陆过渡相地层和新构造期活动断裂的研究成果,对前人提出的福建台湾晚更新世存在陆桥之说进行探讨。     

Late Quaternary landscape development along the Rancho Marino coastal range front (south‐central Pacific Coast Ranges,California, USA)

Late Quaternary landscape development along the Rancho Marino coastal range front in the central‐southern Pacific Coast Ranges of California has been documented using field mapping, surveying, sedimentary facies analysis and a luminescence age determination. Late Quaternary sediments along the base of the range front form a single composite marine terrace buried by alluvial fans. Marine terrace sediments overlie two palaeoshore platforms at 5 m and 0 m altitude. Correlation with the nearby Cayucos and San Simeon sites links platform and marine terrace development to the 125 ka and 105 ka sea‐level highstands. Uplift rate estimates based on the 125 ka shoreline angle are 0.01–0.09 m ka^?1 (mean 0.04 m ka^?1), and suggest an increase in regional uplift along the coast towards the NW where the San Simeon fault zone intersects the coastline. Furthermore, such low rates suggest that pre‐125 ka uplift was responsible for most of the relief generation at Rancho Marino. The coastal range front landscape development is, thus, primarily controlled by post 125 ka climatic and sea‐level changes. Post 125 ka sea‐level lowering expanded the range front piedmont area to a width of 7.5 km by the 18 ka Last Glacial Maximum lowstand. This sea‐level lowering created space for alluvial fan building along the range front. A 45 ± 3 ka optically stimulated luminescence (OSL) age provides a basal age for alluvial fan building or marks the time by which distal alluvial fan sedimentation has reached 300 m from the range front slope. Fan sedimentation is related to climatic change, with increased sediment supply to the range front occurring during (1) glacial period cold stage maxima and/or (2) the Late Pleistocene–Holocene transition, when respective increases in precipitation and/or storminess resulted in hillslope erosion. Sea‐level rise after the 18 ka lowstand resulted in range front erosion, with elevated localised erosion linked to the higher relief and steeper slopes in the SE. This study demonstrates that late Quaternary coastal range front landscape development is driven by interplay of tectonics, climatic and sea‐level change. In areas of low tectonic activity, climatic and sea‐level changes dominate coastal landscape development. When the sea‐level controlled shoreline is in close proximity to the coastal range front, localised patterns of sedimentation and erosion are passively influenced by the pre‐125 ka topography. Copyright © 2008 John Wiley & Sons, Ltd.     

杭州湾晚第四纪沉积与古环境演变

通过对杭州湾第四系钻孔的年代地层学、沉积学、古环境学等多学科综合分析,认为XZK169孔全新世沉积始于孔深17.35m处(年代约为10～9kaBP),其下至孔深86.40m沉积属晚更新世。整个沉积层中可分出3个海进—海退旋回晚更新世早期以陆相沉积为主,出现河湖相—滨海湖泊相—河湖相沉积,气候为温凉干燥—温暖湿润—温凉干燥;晚更新世中晚期出现河湖相—潮滩湖相—浅海相—河口湾相沉积,气候为温凉干燥—寒冷干燥—温凉—暖热湿润—温热湿润;经历了末次冰期侵蚀后,全新世出现浅海相—河口湾相沉积,气候以暖热湿润—温暖湿润为主。约在5kaBP,杭州湾与长江口分离。     

塔城地区晚泥盆世沉积特征及其构造古地理意义

通过对实测剖面层序和沉积特征的详细分析,将塔城北部晚泥盆世塔尔巴哈台组下亚组由下向上分为四个沉积相组合,分别为浊积岩相、浅海陆棚相、滨海相及海陆交互相,构成向上变粗变浅的沉积序列。古流向和沉积演化分析表明,塔城北部地区晚古生代初期位于成吉思-塔尔巴哈台褶皱隆起带以北,其性质为向北开放的大陆边缘,发育晚古生代塔尔巴哈台组深海、浅海、滨海到海陆交互相的沉积体系。准噶尔西北塔城地区晚古生代早期古地理格局可能由南部成吉思-塔尔巴哈台早古生代褶皱带形成的隆起区和其北的向北开放的大陆边缘构成。