三峡地区极短周期内剥蚀速率、下切速率及地表隆升速率对比研究

通过河流输沙量计算出三峡地区短周期的剥蚀速率为0.084 mm/a,将剥蚀速率、下切速率以及隆升速率对比研究,确定了长江流域三峡段极短周期内下切速率与地表隆升速率之间的线性关系,并得出侵蚀基准面及气候变化的约束系数大约是0.4.基于前人对三峡地区一级阶地的数据,计算出一级阶地的下切速率约为3.025 mm/a.现代地壳变形测量和GPS测量结果,发现黄陵穹隆现今地表相对于周边地区其地表隆升速率最大可达5～10 mm/a.取其平均值7.5 mm/a作为三峡地区极短周期的地表隆升速率,对比分析三峡地区剥蚀速率、下切速率与隆升速率,结果该区隆升速率大于剥蚀速率,大约是剥蚀速率的89倍;下切速率也大于剥蚀速率,大约是剥蚀速率的36倍;隆升速率同样大于下切速率,大约是下切速率的2.5倍.三峡地区隆升大于剥蚀,也大于下切速率,三峡地区地表仍然在不断地升高;而地表剥蚀速率小于下切速率,地表切割进一步加深,因此地貌出现高低起伏、山高谷深的形态,并有进一步加剧的趋势.     

乌梁素海沉积物沉积速率与粒度特征研究

为了获得乌梁素海沉积的历史过程以及环境演化特征,过对乌梁素海近岸区(WLSH-1)、入水口区(WLSH-2)、开阔湖区(WLSH-3)和退水口区(WLSH-4)采集的4个柱状沉积物的沉积速率、粒度参数和粒度分布频率曲线等特征进行了分析.乌梁素海4个样点的平均沉积速率并不相同,WLSH-1为0.49cm/a,WLSH-2为0.86cm/a,WLSH-3为0.95cm/a,WLSH-4为0.79cm/a.在最近的80a乌梁素海的平均沉积速率有缓慢增加的趋势,特别是进入21世纪之后沉积速率显著增加.根据210Pb法测年推算出柱状沉积物所属年代范围,4个柱状沉积物在垂向上均表现为阶段式沉积变化特征,除WLSH-4属两段式特征外,其余3个柱状样均属三段式特征。除WLSH-3柱状沉积物平均粒径自下而上呈"粗→细"规律外,其余3个柱状样均呈"细→粗→细"规律.     

穆格莱德盆地凯康坳陷西斜坡地层剥蚀与埋藏史研究

为深入了解穆格莱德盆地凯康坳陷西斜坡地区地层沉积和埋藏史情况,根据回剥法改进的"刘景彦模型",消除多剥蚀面盆地内上覆地层压实作用影响,并利用声波时差计算各剥蚀面剥蚀厚度,在综合分析地层残余厚度与剥蚀厚度的基础上恢复了研究区埋藏史.结果表明:①Baraka与Amal间剥蚀厚度最大,Abu Gabra与Bentiu间剥蚀厚度最小;②斜坡西部与南部剥蚀量大,东部与北部小;③受区域构造运动和沉降速率影响,北部地区沉降速度和沉积速率小,地层埋藏较浅,断层规模小,密度大,发育大量小型断块圈闭;④南部地区沉降速度和沉积速率较高,各组地层埋藏较深,烃源岩进入生油窗时间更早,大型同生断层发育,多见大型断块和断鼻圈闭,石油地质条件优于北部地区.     

210Pb和137Cs法对比研究武汉东湖现代沉积速率

对采自东湖Ⅰ站和Ⅱ站的沉积物采用^210Pb和^137Cs相结合的方法测定沉积速率,^210Pb法测出东湖Ⅰ站和Ⅱ站的沉积速率为8．73mm／a和6．90mm／a,^137Cs测出东湖Ⅰ站和Ⅱ站的沉积速率为7．4mm／a和5．8mm／a．分析了两种方法测定结果差异产生的原因,并与以往的研究相对比,探讨东湖沉积速率空间分布的规律性,沉积速率变化与人类活动的关系、沉积速率与扰动的关系．     

应用宇宙成因核素10Be和26Al估算剥蚀面的暴露时间及剥蚀速率和剥蚀厚度

宇宙成因核素10 Be和2 6Al的浓度记录着岩层剥蚀面的暴露时间和岩石剥蚀速率等信息。利用数学换算法分析影响10 Be和2 6Al浓度的因素 ,并利用10 Be和2 6Al的半衰期的近似倍数关系建立联立方程组 ,从理论上得到了年轻地质体中遭受快速埋藏的剥蚀面的暴露时间和剥蚀速率的估算公式。在此基础上 ,对整个剥蚀区不同位置剥蚀速率进行了分析。通过分析可以更准确地估算出整个剥蚀区不同位置的剥蚀厚度 ,从而可恢复剥蚀面的古地貌。     

镜质组反射率在推算古地温和恢复地层剥蚀厚度方面的研究与进展

为进一步探讨镜质组反射率在沉积盆地演化过程中推算古地温和恢复地层剥蚀厚度的作用,通过查阅大量文献,对比分析了近年来国内外含煤及油气沉积盆地研究中常用的镜质组反射率方法及其适用性,阐述了各种镜质组反射率分析法的基本原理。研究结果表明,准确的测定方法是保证镜质组反射率数值正确的前提;采用镜质组反射率恢复地层剥蚀厚度,必须基于对研究区地质构造背景的完全理解,避免因其多解性造成分析结果错误;当油浸镜质组反射率值超过4.0%,原则上该参数不再适合于古地温推算及地层剥蚀厚度的恢复。将镜质组反射率方法用于含煤沉积盆地固体有机质演化阶段分析是一个值得探索的研究方向。     

辽河盆地西部凹陷北部地区古近系地层剥蚀量恢复

辽河盆地新近系(N)、古近系(E)之间不整合面形成于盆地由裂陷发育阶段向坳陷发育阶段转化的过渡时期,古近系地层在沉积后遭受了长期的非均衡剥蚀.通过地质分析及实践,选用地层结构趋势外延法和声波测井曲线法计算了研究区的地层剥蚀量,并在此基础之上,对原型盆地进行了恢复.从所得的两幅形态近似的剥蚀量等值线图上的剥蚀趋势得出:横向上剥蚀量自南西向北东逐渐增大,这种差异性剥蚀是古近纪末期台安—大洼断裂右旋走滑作用在本区形成的北西向褶皱格局所引起.从盆地原始沉积厚度等值线图也可以得出,不同时期原型盆地的形态和盆地的类型具有明显的阶段性差异.导致上述结果的根本原因则是郯庐断裂右旋走滑作用的影响.     

鄂尔多斯盆地延长组长7段沉积速率及其对烃源岩有机质丰度的影响

以鄂尔多斯盆地延长组长7段富有机质页岩为对象,基于米兰科维奇旋回理论,计算了该段3个小层的沉积速率,发现长7段的沉积速率整体较小(平均1.31 cm·a~(-1)),并且具有从长73到长71逐渐增大的特征。另外,利用△logR法对已经计算了沉积速率的井进行TOC含量测井预测,并结合沉积速率和TOC含量的数据建立了两者的相关关系。研究表明:当沉积速率小于1.35 cm·a~(-1)时,TOC含量与沉积速率没有明显的相关关系,沉积物中的有机质丰度主要受其他因素的控制,如古生产力条件和保存条件;当沉积速率大于1.35 cm·a~(-1)时,TOC含量具有随沉积速率变大而逐渐减小的趋势,说明沉积速率越大,沉积物中的有机质被稀释或破坏越严重,有机质丰度就越小。     

关于衡量气相沉积快慢的思考

在用气相沉积法制备薄膜时,为了表征薄膜沉积的快慢,定义了沉积速率。但是,由于实验条件的限制,沉积速率的计算大部分是通过测量的薄膜平均厚度除以沉积时间来获得,尽管在实际应用中并未遇到很大困难,但是由于沉积速率跟很多因素有关,有必要讨论跟沉积速率相关的参数,为今后进一步制备薄膜作一定铺按。     

沉积速率对HfO_2薄膜应力和光学特性的影响

利用电子枪蒸镀法制备了HfO2薄膜,控制沉积速率分别为3.3/s、5.5/s和9.6/s.利用ZGYO干涉仪、UV3101-PC分光光度计、D/Max-ⅢA型X射线衍射仪和JSM-6700F冷场发射扫描电镜对样品进行了测试.结果表明:在本实验条件下制备的HfO2薄膜都是非晶态结构.样品的残余应力与本征应力变化趋势相同,都随沉积速率的加快先增后减,沉积速率为3.3/s时应力最小.不同沉积速率下制备样品的折射率都是正常色散,3.3/s沉积的样品色散较小并且有较好的表面平整度.这些结果为制备高性能HfO2薄膜提供参考.     

First discovery and characterizations of late Cretaceous seep carbonates from Xigaze in Tibet, China

Hydrocarbon seeps,widely occurring in continental margins,have become increasingly focused owing to their close relationships with gas hydrates,strong greenhouse gas methane,and biological resources in extreme environments.Ancient hydrocarbon seeps have already been recognized from Devonian to Quaternary strata worldwide based on seep carbonates or seep-related fossil chemosynthetic assemblages.However,seep-related deposits are rarely found from ancient strata in the mainland China.Here,we report the first discovery of an ancient seep deposit,specifically late Cretaceous seep carbonates from Xigaze in Tibet,China.Xigaze seep carbonates,occurring as nodules,are enclosed in upper Cretaceous turbidite strata in Xigaze forearc basin.These carbonates are composed of authigenic carbonate(56.2% on average),clastic quartz and feldspar(27.3% on average),and clay minerals(chlorite,illite and smectite,16.5% on average).Clotted micrites,peloids and framboid pyrites are frequently observed,all of which are common in modern seep carbonates.The carbonates have negative δ13 C values varying from 27.7‰ to 4.0‰(V-PDB),suggesting that thermogenic methane is the primary carbon source.Ce/Ce* values revised by eliminating La effects show no real Ce anomaly,indicating the carbonates were primarily precipitated in a weak reducing environment.Overall,these features provide unequivocal evidences that the seafloor of Xigaze forearc basin developed hydrocarbon seeps in late Cretaceous.     

Sedimentary environment of the Dajin conglomerate in Tibet, age of foraminiferan assemblages and their tectonic significance

The Dajin conglomerate, which is one of the most important sedimentary successions of the Xigaze forearc basin in Tibet, China, consists of deep-shallow marine tuffaceous turbidites and clastic rocks bearing Nummulites, Assilina, Alveolina and Lockhartia. These fossils are very similar to the foraminiferan in the Jialazi and Maila conglomerates, and those in Gangba and Dingri areas. They developed in the Eocene. By analyzing the spatial variation of Eocene sedimentary environments of Tibet Plateau and the foraminiferan in the Dajin conglomerate, we found that Eocene sedimentation should take place on both sides of the Yarlung Tsangpo suture, and the late Eocene tectonic uplifting should make the forearc basin expose out of the sea level and begin to receive nonmarine deposits.     

Sedimentation rates and provenance analysis in the Southwestern Okinawa Trough since the mid-Holocene

As a high-sedimentation rate depocenter along the path of the Kuroshio Current, the southwesternmost part of the Okinawa Trough is a key area to understand the Kuroshio history and sediments transpor-tation. A 34.17-m-long sediment core was obtained by the advanced piston corer of Marco Polo/IMAGES XII MARION DUFRESNE during the May 2005 from the Southern Okinawa Trough at site MD05-2908. The recovered sediments were analyzed by AMS ¹⁴C dating, coarse size fraction (>63 μm) extraction and moisture content determination in order to study its sedimentation flux and provenance. The depth-age relationship of core MD05-2908 was well constrained by 17 ¹⁴C dating points. The sediments span across the mid-Holocene (6.8 ka B.P.) and have remarkablely high sedimentation rates between 1.8 and 21.2 m ka^-1, which is well consistent with the modern observations from sediment traps. We identified five 70―200 a periods of abnormally rapid sedimentation events at 6790―6600 a B.P., 5690―5600 a B.P., 4820―4720 a B.P., 1090―880 a B.P., and 260―190 a B.P., during which the highest sedimentation rate is up to 21.2 m/ka. In general, the lithology of the sediments were dominated by silt and clay, associated with less than 5% coarse size fraction (>63 μm). As the most significant sediment source, the Lanyang River in northeastern Taiwan annually deliver about 10Mt materials to the coastal and offshore region of northeast Taiwan, a portion of which could be carried northward by currents toward the study area. Therefore, we concluded that the 5 abnormally rapid sedimentation events may be related to intensified rainfall in Taiwan and thus increased materials to our study area at that time. However, a few ex-treme-rapid sedimentation events cannot be explained by normal river runoff alone. The large earth-quakes or typhoons induced hyperpycnal discharge of fluvial sediment to the ocean may also act as a potential source supply to the Okinawa Trough.     

中新世以来滇西高原内红河流域区的古高程反演

流经滇西高原的红河水系将高原内被剥蚀下来的物质输送到莺歌海盆地与琼东南盆地中堆积.滇西高原隆升剥蚀区与莺歌海盆地和琼东南盆地堆积区构成了一个相对封闭系统.采用质量平衡法,将莺-琼盆地内的堆积物回剥至隆升剥蚀区,重建了中新世以来滇西高原内红河流域区所达到的可能高程.16.2～19.6 Ma前红河流域区海拔高度低于560 m,16.2～11 Ma前的隆升使高程升至860～950 m.经过11～5.3 Ma前的剥蚀夷平后,海拔高度降为800m.距今5.3～1.6 Ma前的快速隆升,使海拔高度曾达到2600～2725 m,隆升幅度达1800～1925 m,滇西高原形成.近1.6 Ma以来则主要是剥蚀削低,海拔高度从2560 m降为2300m.中新世以来红河流域区被剥蚀掉约3900 m.     

西藏南部雅鲁藏布江缝合带的沉积－构造演化

西藏南部雅鲁藏布江缝合带从晚侏罗世至今可能经历了新特提斯洋的两期俯冲作用,早期俯冲从晚侏罗世至早白垩世,以桑日群和恰布林组为代表,雅鲁藏布江古蛇绿岩在此期形成;而晚期俯冲从中白垩世至始新世,以混杂岩、雅鲁藏布江蛇绿岩和日喀则为代表,拉孜－浪卡子断裂可能代表了印度大陆与亚洲大陆碰撞的实际地表位置,由此提出包括新特提斯洋两期俯冲作用在内的五个阶段的雅鲁藏布江缝合带沉积－构造演化过程。     

辽南地区末次冰期以来的环境变化

本文通过对大连七顶山黄土剖面的光释光(OSL)年代、磁化率、地球化学元素、粒度特征等数据,综合分析辽南地区末次冰期以来的环境变化过程,研究结果显示:相当于黄土高原马兰黄土的堆积形成时代为距今125ka。在末次冰期早期(MIS4-5d),86-113ka,沉积物质量磁化率介于6.97-24.14×10-8m3kg-1之间,平均值为14.699×10-8m3kg-1;颗粒粒径较细(3.89-5.22准);硅铝率平均值6.756;风化淋溶系数0.4-0.73之间;退碱系数均值0.333;镁铝比均值22.901。与末次冰期晚期相比,质量磁化率值较高,化学元素各项指标值较低,明了该阶段辽南整体气候环境较为干冷,但并未达到末次冰期晚期程度。而在末次冰盛期时(22-31ka,MIS2),磁化率平均值为6.974×10-8m3kg-1,明显低于末次冰期早期,粒度均值处于3.47准-4.77准之间,主要以颗粒较粗的细砂、粗粉砂为主,粒度明显变粗,硅铝率平均为6.998;风化淋溶系数均值为0.829,退碱系数值0.66,镁铝比值均值28.725,各参数比较一致地表明该阶段研究区整体处于干冷的气候环境之下,堆积作用较活跃。而在末次冰期中期(MIS3)时,OSL年代31-86ka,该区气候条件以温暖湿润为主,黄土遭到侵蚀。     

三峡水库干流典型消落带泥沙沉积过程

 选择三峡水库中游干流典型消落带断面,现场调查泥沙沉积速率随高程分布,探讨三峡水库特定水位调节模式和长江上游泥沙输移的季节性特征对消落带泥沙沉积的影响。结果表明,消落带泥沙净沉积主要发生在145~168 m 高程,2010年累积净沉积厚度为1.1~39.9 cm,随高程增加逐渐减小,145~155 m 平均泥沙沉积厚度为14.9 cm,155~168 m 平均泥沙沉积厚度为2.6 cm;2013年累积净沉积厚度为3~80 cm,表明三峡水库干流消落带泥沙沉积过程迅速。泥沙粒径随高程增加逐渐变粗,体现在砂粒体积分数和中值粒径逐渐增大。消落带下部沉积泥沙颗粒组成与干流悬移质泥沙接近,而消落带上部沉积泥沙明显粗于干流悬浮泥沙。消落带泥沙沉积速率与水库水位调节密切相关,雨季水库低水位运行,长江悬移质输沙量的增加导致了消落带下部大量泥沙沉积;旱季水库高水位运行,长江悬移质输沙量减少导致消落带上部泥沙沉积速率降低,消落带河岸侵蚀对沉积泥沙贡献逐渐增大。消落带淹水时间随高程增加而缩短,长时间淹没有利于消落带下部泥沙沉积。综合推断,三峡水库干流消落带下部泥沙主要来源于雨季河流悬移质泥沙的沉积,而消落带上部沉积泥沙主要来自旱季消落带河岸侵蚀产沙。     

云南江川星云湖盆现代沉积的研究

本文通过对江川盆地和星云湖现代沉积作用的研究,划分了湖周围晚新生代沉积的三种相组合,并讨论了构造、气候对沉积作用的控制和盆地发育特点及其在石油地质方面的启示。     

Geothermal field and its relation with coalbed methane distribution of the Qinshui Basin

The average geothermal gradient in the Qin-shui Basin, Shanxi Province, North China, estimated from temperature logging data of 20 boreholes is 28.2±1.03℃/km. The thermal conductivities of 39 rock samples are measured and 20 heat flow values are obtained. The estimated heat flow ranges from 44.75 mW7m2 to 101.81 mW/m2, with a mean of 62.69±15.20 mW/m2. The thermal history reconstruction from the inversion of vitrinite data, using Ther-model for Windows 2004, reveals that the average paleo-heat flow at the time of maximum burial in late Jurassic to early Cretaceous is 158.41 mW/m2 for the north part, 119.57 mW/m2 for the central part and 169.43 mW/m2for the south part of the basin respectively. The reconstruction of the buried history of the strata indicates that the age for the end of sedimentation and the beginning of erosion for the basin is 108-156 Ma, and that the eroded thickness of the strata is 2603 m in the north, 2291 m in the central, and 2528.9 m in the south of the basin respectively. The "higher in the north and the south, lower in the central" distribution pattern of the paleo-heat flow coincides with the distribution of the coal-bed methane spatially and temporally, which shows that the coal-bed methane is controlled by the paleo-geotem-perature field in the basin.     

长江下游巢湖湖泊沉积物的粒度特征与沉积环境

在巢湖取得3个有代表性的沉积物柱样,用激光粒度仪对其进行粒度分析,并用137Cs法测定了沉积速率.结果表明,沉积物的粒度特征随着湖区的水动力条件的波动而发生有规律的变化.近百年来湖区的沉积环境基本上比较稳定,C1、C2和C3三个研究区的沉积速率分别为0.29cm/a,0.35cm/a和0.24cm/a.根据粒度和沉积速率特征,两百多年来,巢湖存在两个洪水期和两个平水期,这些变化与巢湖自然环境和人类活动有着密切关系.