张家口-蓬莱断裂带渤海段晚第四纪活动特征

张家口-蓬莱断裂带是华北地区一条显著的地震带.利用最新获得的高分辨率浅层地震资料研究了渤海海域内该断裂带晚第四纪以来的活动特征.研究表明:在渤海,张家口-蓬莱断裂带主要由沙西断裂、埕北断裂、沙南断裂、沙东北断裂、柏各庄断裂、石臼坨3号断裂、渤中2号断裂和BZ29断裂等一系列NW走向断裂组成,走向在290°～310°之间;在浅层沉积物中各断裂由多条次级小断裂组成;晚第四纪以来主要表现出强烈的垂向运动特征,具有正断性质;海域各断裂的最新活动时代为晚更新世(Q3)末期-全新世(Q4)初期,并具有相同的活动趋势,在20 ka B.P.和60 ka B.P.左右活动强烈,统计计算显示平均垂向活动速率分别为0.15 mm/a和0.1 mm/a,近20 000 a以来的垂向活动速率超过0.06 mm/a.     

The sedimentation rates in the Okinawa Trough during the Late Quaternary

On the basis of accelerator mass spectrometer radiocarbon （AMS ^14C） dating, sedimentation rates of 11 cores collected from the northern to southern Okinawa Trough are discussed. The sedimentation rates in the Okinawa Trough roughly range from 11 to 39cm/ka, and the average is 23.0cm/ka. China＇s continental matter is the main sediment source of the middle Okinawa Trough and has important contribution to the northern and southern Okinawa Trough. The sedimentation rates during the marine oxygen isotope （MIS） 2 are uniformly higher than those during MIS 1 in the northern and middle Okinawa Trough while they are on the contrary in the southern Okinawa Trough. Sedimentation rates in the Okinawa Trough can be one of the proxies of sediment source and an indicator of cooling events.     

Paleoenvironmental changes of the Yellow Sea during the Late Quaternary

Based on stable isotope data and carbon and sulfur elemental analyses, the sedimentary environment of the Yellow Sea was significantly influenced by the sea level changes during the Late Quaternary. At the low sea level stand when the sea level was lower by 56?m, the salinity of seawater was reduced to about 7.6‰, and the sedimentation rate in the central part of the Yellow Sea was three times higher than the present rate. The high C/S ratio during the low sea level stand is strong evidence that sedimentation took place in a lower salinity environment than exists at present.     

Paleoenvironmental changes of the Yellow Sea during the Late Quaternary

 Based on stable isotope data and carbon and sulfur elemental analyses, the sedimentary environment of the Yellow Sea was significantly influenced by the sea level changes during the Late Quaternary. At the low sea level stand when the sea level was lower by 56 m, the salinity of seawater was reduced to about 7.6‰, and the sedimentation rate in the central part of the Yellow Sea was three times higher than the present rate. The high C/S ratio during the low sea level stand is strong evidence that sedimentation took place in a lower salinity environment than exists at present. Received: 25 September 1997 / Revision reveived: 15 June 1998     

九龙江河口平原晚第四纪孢粉组合及气候环境演变

本文运用有序系统聚类、对应聚点、最优分割三种数学地质方法,参照孢粉图式将九龙江河口平原海澄ＺＫ５孔剖面划分为８个孢粉带。结合其他钻孔有关资料,得出研究区９个综合分组合带,分别反映晚第不同阶段的不同气候环境。通过对应分析结果表明,本区晚第四纪被演替的决定因素中,湿度比温度更为重要。     

Kane Fracture Zone

The Kane Fracture Zone probably is better covered by geophysical survey data, acquired both by design and incidentally, than any other fracture zone in the North Atlantic Ocean. We have used this data to map the basement morphology of the fracture zone and the adjacent crust for nearly 5700 km, from near Cape Hatteras to the middle of the Mesozoic magnetic anomalies west of Cap Blanc, northwest Africa. We use the trends of the Kane transform valley and its inactive fracture valley to determine the record of plate-motion changes, and we interpret the basement structural data to examine how the Kane transform evolved in response to changes in plate motion. Prior to about 133 Ma the Kane was a small-offset transform and its fracture valley is structurally expressed only as a shallow ( < 0.5 km) trough. In younger crust, the offset may have increased to as much as 190 km (present offset 150 km) and the fracture valley typically is up to 1.2 km deep. This part of the fracture valley records significant changes in direction of relative plate motion (5°–30°) near 102 Ma, 92 Ma, 59 Ma, 22 Ma, and 17 Ma. Each change corresponds to a major reorganization of plate boundaries in areas around the Atlantic, and the fracture-zone orientation appears to be a sensitive recorder of these events. The Kane transform has exhibited characteristic responses to changes in relative plate motion. Counterclockwise plate-motion changes put the left-lateral transform offset into extension, and the response was for ridge tips at the ridge-transform intersections to propagate across the transform valley and against the truncating lithosphere. Heating of this lithosphere appears to have produced uplift and formation of a well developed transverse ridge that bounds the inactive fracture valley on its older side. The propagating ridge tips also rotated toward the transform fault in response to the local stress field, forming prominent hooked ridges that now extend into or across the inactive fracture valley. Clockwise (compressional) changes in relative plate motion produced none of these features, and the resulting fracture valleys typically have a wide-V shape. The Kane transform experienced severe adaptions to the changes in relative plate motion at about 102 Ma (compressional shift) and 92 Ma (extensional shift), and new transform faults were formed in crust outside the contemporary transform valley. Subsequently, the transform offset has been smaller and the rates of change in plate motion have been more gradual, so transform-fault adjustment has been contained within the transform valley. The fracture-valley structure formed during extensional and compressional changes in relative plate motion can be decidedly asymmetrical in conjugate limbs of the fracture zone. This asymmetry appears to be related to the ‘absolute’ motion of the plate boundary with respect to the asthenosphere.     

Late Quaternary sedimentation in the Kadeok region, Korea

Analyses of high-resolution seismic-reflection data and geological samples revealed the characteristics of Quaternary sedimentation in the Kadeok region at the opening of the Nakdong River. The sediments comprise two layers, i.e., a 20- to 45-m-thick Holocene mud layer, and a coarser late-Pleistocene layer deposited in a fluvial environment. Sedimentological variations in the late-Pleistocene layer to the west and east of Kadeok Island are due to differences in channel maturity prior to the Holocene transgression. Holocene mud in the sea to the west of Kadeok Island was transported through a passway north of the island. Received: 26 October 1999 / Revision accepted: 7 February 2000     

辽东湾晚第四纪层序地层

通过对辽东湾高分辨率浅地层剖面声学地层与典型钻孔沉积地层的对比分析,揭示了研究区晚第四纪MIS5以来的地层层序。辽东湾高分辨率浅地层剖面自下而上划定的6个声学地层单元(SU₅、SU₄、SU₃、SU₂、SU₁²、SU₁¹)与钻孔岩芯划分的6个沉积地层单元(DU₅、DU₄、DU₃、DU₂、DU₁²、DU₁¹)具有良好的对应关系。分别与MIS4期、MIS2期低海面时期的沉积间断密切相关的两个层序界面R5、R3,将辽东湾识别出的地层单元自下而上划分为3个层序(SQ3、SQ2、SQ1)。其中SQ3仅识别出上部的海侵体系域与高水位体系域,对应MIS5期海平面相对较高时期的滨浅海相沉积(DU₅);SQ2自下而上由低水位体系域(MIS...     

渤海地区晚第四纪环境演化与第四纪滨海相地下卤水的形成

由于气候变化和新构造运动,渤海曾发生多次海陆演化,从而形成了第四纪地下卤水。间冰期的海侵提供了形成地下卤水的水源,气候波动产生了海水浓缩的条件,而冰期海退过程中,陆源物质覆盖于海相沉积上,保存了地下卤水。对环境演化在“潮滩生卤”和“冰冻生卤”过程中重要作用的分析结果表明,在第四纪环境演变的过程中,两种生卤作用在地质时期卤水矿床形成中均具有重要意义,并且只要存在海水物源,就有可能形成地下卤水。     

南沙群岛海区晚第四纪碳酸盐沉积

本文研究了五个柱状沉积物的碳酸盐沉积。根据沉积物的陆源碎屑和生物骨屑ＣａＣＯ３沉积作用的特点，把本区沉积物分为五种沉积类；碳酸盐生物组成的门类较多，以有孔虫为主，其次为珊瑚，腹足类等；碳酸盐矿物以低镁方解石为主，还有高镁方解石和文石；与沉积物中ＣａＣＯ３有关的化学元素１０多种。这些元素和稀土元素的含量，比值等，是区分礁相，礁体过渡带和非礁相的标志。所有这些碳酸盐沉积作用的特点表明，区内存在着五种沉     

Late Quaternary chronology of the southern Black Sea basin

During New Euxinian time when sea level dropped below the sill connecting the Black and Marmara seas, the Black Sea became isolated and freshwater sediments were deposited. Now it is a semieuxinic basin with the oxic/anoxic boundary at 100–150 m. The seasonal changes in sedimentation are preserved in the form of laminated sequences. The counting of varves in southeastern Black Sea cores show the chronology of the O₂/H₂S interface. The age of the Holocene sapropel along the eastern margin ranges from 4000 to 1000 yr BP in deep water and 2500—1000 yr BP in shallower water. Sapropel formation started at 3650 yr BP at a water depth of 2200 m.     

Late Quaternary Seismic Stratigraphy of the Eastern Bengal Shelf

An ultra-high-resolution seismic study of the eastern Bengal Shelf with the parametric narrow-beam echosounder Parasound allows the interpretation of late Quaternary depositional patterns in terms of seismic stratigraphy. Accommodation space was still present on the outer shelf during the last lowstand, where a prograding delta developed in the western survey area. Oolitic beach ridges were later formed on top of this lowstand delta. Farther east, large parts of the shelf were exposed to subaerial erosion and a river system extended seaward across the area. A subaqueous highstand delta prograded southwards following the maximum transgression about 7,000 years ago. Its foreset beds exhibit acoustic voids very likely generated by sediment liquefaction, possibly caused by episodic energetic events such as major cyclones and/or earthquakes. Bottomset sediments extend seaward close to the shelf break in the west, whereas no Holocene sediments cover the outer shelf in the east.     

Late Quaternary polycystine radiolarian datum events in the Sea of Okhotsk

Five radiolarian datum events have been recorded in the Late Quaternary sediment section from the Sea of Okhotsk, using age assignments based on oxygen-isotope stratigraphy: the last occurrence datum (LOD) of Stylacontarium acquilonium (at about 329 ka), the LOD of Spongodiscus sp. (at about 287 ka), the LOD of Amphimelissa setosa (at about 72 ka), the LOD of Lychnocanoma nipponica sakaii (at about 28 ka), and the L. nipponica sakaii acme event (at about 72 ka). The LODs of S. acquilonium, Spongodiscus sp. and A. setosa appear to be synchronous in comparison with those in the Subarctic North Pacific, but the LOD and the acme event of L. nipponica sakaii show an apparent diachroneity with the corresponding North Pacific events.     

Morphology and Late Quaternary sedimentation in the Gulf of Oman Basin

The morphology of the Gulf of Oman Basin, a 3,400 m deep oceanic basin between Oman and southern Pakistan and southern Iran, ranges from a convergent margin (Makran margin) along the north side, a passive type (Oman margin) along the south side, translation types along the basin's west (Zendan Fault-Oman Line) and east (Murray Ridge) sides and a narrow continental rise and a wide abyssal plain in the centre of the basin. Sediment input into the basin during the Late Quaternary has been mainly from the north as a result of the uplift of the Coast Makran Mountains in the Late Miocene-Pliocene. Today most of this detritrus is deposited on the shelf and upper continental slope and perched basins behind the fold/fault ridges on the lower slope. The presence of fans and channels on the continental rise on the north side of the basin indicate, however, that continental derived debris was, and possibly is, being transported to the deep-sea by turbidity currents via gaps in the ridges on the lower slope. In addition to land derived terrigenous sediments, the basin deposits also contain biogenic (organic matter and calcium carbonate), eolian detritus and hydrates and authigenic carbonates from the tectonic dewatering of the Makran accretionary wedge. The eolian sediment is carried into the Gulf of Oman Basin from Arabia and the Mesopotamia Valley by the northwesterly Shamal winds. This type of detritus was particularly abundant during the glacial arid periods 21,000–20,000 and 11,000 (Younger Dryas) years ago when exposure of the Persian (Arabian) Gulf increased the area of dust entrainment and shifted the position of the source of the eolian sediments closer to the basin.     

Oceanic crust thickens approaching the Clipperton Fracture Zone

A multi-channel seismic reflection image shows the reflection Moho dipping toward the Clipperton Fracture Zone in crust 1.4 my old. This seismic line crosses the fracture zone at its eastern intersection with the East Pacific Rise. The seismic observations are made in travel time, not depth. To establish constraints on crustal structure despite the absence of direct velocity determinations in this region, the possible effects of temperature, tectonism, and anomalous lithospheric structure have been considered. Conductive, advective, and frictional heating of the old crust proximal to the ridge-transform intersection can explain <20% of the observed travel-time increase. Heating has a negligible effect on crustal seismic velocity beyond ~10 km from the ridge tip. The transform tectonized zone extends only 6 km from the ridge tip. Serpentinization is unlikely to have thickened the seafloor-to-reflection Moho section in this case. It is concluded that, contrary to conventional wisdom, the 1.4 my old Cocos Plate crust thickens approaching the eastern Clipperton Ridge-Transform Intersection. Increase in thickness must be at least 0.9 km between 22 and 3 km from the fracture zone.     

Late Quaternary Seasonal Sea-Ice History of the Northeastern Japan Sea

The Late Quaternary sea-ice history of the northeastern Japan Sea is discussed on the basis of the occurrence of dropstones and ice-rafted debris (IRD) in fine sediment cores. IRD was found in all strata except those from the Holocene and oxygen isotope stage 5.5. The largest expansion of sea ice was recognized at the last glacial maximum (LGM; oxygen isotope stage 2), when the southern margin of seasonal sea ice was probably located in the vicinity of the Matsumae Plateau. The margin might occasionally have expanded further southward to off the Oga Peninsula. Sea ice expanded southward from mid-stage 5 to the LGM in response to global cooling, but with much fluctuation. Sea ice remained during deglaciation until around 10 ka, but after 10 ka it retreated northward rapidly in response to global warming and changes in surface water conditions. Greater fluctuations in IRD were found in core GH95-1208 collected from off Rumoi, Hokkaido, Japan. More IRD was found in sediments from late stage 3, late stage 5, and early stage 6. The fluctuations were not concordant with global climate changes (based on the standard oxygen isotope curve), and may have been controlled by regional climate factors such as the strength of the winter monsoon, which is related in turn to high-latitude atmospheric circulation. This revised version was published online in July 2006 with corrections to the Cover Date.     

Benthic foraminiferal successions across Late Quaternary Mediterranean sapropels

Benthic foraminiferal records across Late Quaternary Mediterranean sapropels S6, S5 and S1 are reviewed and re-considered in the light of recent advances in foraminiferal ecology. It is suggested that the main factor controlling the foraminiferal successions that occur immediately before and after sapropel deposition is the amount of time involved in the onset of anoxic conditions and in the re-oxygenation of the benthic environment. Faunas dominated by deep infaunal taxa such as Globobulimina and Chilostomella reflect a very gradual decrease or increase of bottom water oxygenation. Post-sapropel faunas dominated by small biconvex, trochospiral taxa, which are inferred to have a much more opportunistic life strategy, are typical of a very rapid re-oxygenation of the benthic environment after sapropel deposition. The time involved in re-oxygenation depends upon the mechanism causing sapropel formation. The faunal succession found above sapropel S5 suggests a basin with a strong density gradient in the upper part of the water column during sapropel deposition, followed by a rapid turnover of the following column and quick re-oxygenation of the benthic environment. In contrast, the faunal succession above sapropel S6 suggests a water column with a more gradual density gradient deeper in the basin, a progressive deepening of the halocline, and a very slow increase of bottom water oxygenation.     

冲绳海槽晚第四纪硅藻生物地层划分与对比

本文对冲绳海槽中段B孔岩芯中的沉积硅藻进行了分析。共鉴定出52属166种和变种．根据硅藻属种组成、热带远洋种的相对含量以及整个硅藻植物群的变化特征共划分出9个组合带，并对它们的特征进行了描述；结合^14C测年数据。对该岩芯的地层年代归属进行了确定，全新世与晚更新世的界线位于该孔125cm处．上部地层为全新统，下部地层为上更新统；同时与邻近DGKS9603钻孔的硅藻生物地层进行了对比．     

台湾海峡西部海域第四纪晚期沉积速率的变化

本文利用台湾海峡西部海域第四纪晚期沉积物的沉积速率，研究了沉积速率随环境和年代不同而变化的规律，指出第四纪晚近时期沉积物沉积速率上升的趋势和原因，说明人类的活动，尤其是不合理的开发是引起学积物沉积速率与日俱增的重要原因，应当引起足够的重视。