中天山科克苏河地区隆升剥蚀历史——来自(U-Th)/He年龄的制约

天山是中亚造山带重要组成部分,其中-新生代构造热演化及隆升剥露史研究是认识中亚造山带构造变形过程与机制的关键.本文应用磷灰石(U-Th)/He技术重建中天山南缘科克苏河地区中-新生代构造热演化及隆升剥蚀过程.磷灰石(U-Th)/He数据综合解释及热演化史模拟表明该地区至少存在晚白垩世、早中新世、晚中新世3期快速隆升剥蚀事件,起始时间分别为~90Ma、~13Ma及~5Ma,且这3期隆升剥蚀事件在整个天山地区具有广泛的可对比性.相对于磷灰石裂变径迹,磷灰石(U-Th)/He年龄记录了中天山南缘地质演化史中更新和更近的热信息,即中天山在晚中新世(~5 Ma)快速隆升剥蚀,其剥蚀速率为~0.47mm·a~(-1),剥蚀厚度为~2300m.总体上,中天山科克苏地区隆升剥蚀起始时间从天山造山带向昭苏盆地(由南向北)逐渐变老,表明了中天山南缘隆升剥蚀存在不均一性,并发生了多期揭顶剥蚀事件.     

东海陆架盆地雁荡低凸起综合地球物理解释及其成因探讨

通过对东海陆架盆地西部地震和重磁资料的综合地球物理解释,对雁荡低凸起展布形态进行了细致刻画,凸起呈NE方向不连续展布于瓯江凹陷和闽江凹陷之间,长约170 km、宽约15~50 km.地震资料揭示雁荡低凸起上广泛发育了侏罗纪与白垩纪地层,厚度约为500~1500 m,展布面积约5000 km²,局部缺失中生界地层.凸起两侧中生代盆地结构差异明显,西侧瓯江凹陷为典型的断陷盆地,东断西超、断裂发育,半地堑、掀斜断块等中生界构造样式发育;东侧闽江凹陷为坳陷型盆地,断裂、火成岩不发育,挤压背斜、断背斜、反转构造等中生界构造样式发育.自由空间重力异常图与剩余重力异常图上,凸起表现为一系列NE向团块状重力高值区,而磁力异常ΔT图上则表现为深部磁场强度低的特征,火成岩影响部位可见磁力高值异常.综合凸起及邻域重磁震、莫霍面深度等地质地球物理资料,认为雁荡低凸起为一元古界组成的古隆起,区别于东部的台北低凸起.同时,结合区域构造演化及沉积特征,推测侏罗纪时期雁荡低凸起与浙闽隆起区可能连为一体,晚白垩世近东西向伸展作用下浙闽隆起发生裂陷进而形成了雁荡低凸起.     

Raised Holocene paleo-shorelines along the Capo Vaticano coast (western Calabria,Italy): Evidence of co-seismic and steady-state deformation

Detailed mapping of geomorphological and biological sea-level markers around the Capo Vaticano promontory (western Calabria, Italy), has documented the occurrence of four Holocene paleo-shorelines raised at different altitudes. The uppermost shoreline (PS1) is represented by a deeply eroded fossiliferous beach deposit, reaching an elevation of ∼2.2 m above the present sea-level, and by a notch whose roof is at ∼2.3 m. The subjacent shoreline PS2 is found at an elevation of ∼1.8 m and is represented by a Dendropoma rim, a barnacle band and by a wave-cut platform. Shoreline PS3 includes remnants of vermetid concretions, a barnacle band, a notch and a marine deposit, and reaches an elevation of ∼1.4 m. The lowermost paleo-shoreline (PS4) includes a wave-cut platform and a notch and reaches an elevation of ∼0.8 m. Radiocarbon dating of material from individual paleo-shorelines points to an average uplift rate of 1.2–1.4 mm/yr in the last ∼6 ka at Capo Vaticano. Our data suggest that Holocene uplift was asymmetric, with a greater magnitude in the south-west sector of the promontory, in a manner similar to the long-term deformation attested by Pleistocene terraces. The larger uplift in the south-western sector is possibly related to the additional contribution, onto a large-wavelength regional signal, of co-seismic deformation events, which are not registered to the north-east. We have recognized four co-seismic uplift events at 5.7–5.4 ka, 3.9–3.5 ka, ∼1.9 ka and <1.8 ka ago, superposed on a regional uplift that in the area, is occurring at a rate of ∼1 mm/yr. Our findings places new constrains on the recent activity of border faults south of the peninsula and on the location of the seismogenic source the 1905 destructive earthquake.     

Microfossils from the Arymas and Debengda formations, the Riphean of the Olenek Uplift: Age and presumable nature

Studied assemblages of diverse organic-walled microfossils separated from the Arymas and Debengda formations of the Olenek Uplift include several paleobiological groups of microorganisms. Sufficiently large morphotypes of the first group are identified with remains of cyanobacteria. Morphotypes of variable spiral structure, which dwelt in association or in symbiosis with cyanobionts, are attributed to the same bacterial community. The other group includes a series of different acritarch genera whose characters suggest their affinity with green algae of the order Desmidiales. It is very likely that this group coexisted on siliciclastic shoals with large ancestral forms of the present-day brown algae. Several microfossil taxa have been known before from the Neoproterozoic deposits only. With due regard for the relatively gradual accumulation of sedimentary succession lacking large hiatuses and for the regular series of K-Ar dates characterizing three Riphean formations of the Olenek Uplift, it is possible to suggest that there was the Arymas-Debengda-Khaipakh cycle of long-lasted, almost uninterrupted sedimentation within the time span of 1250–900 Ma. It is also admissible that age ranges of some Late Precambrian microfossils are much larger than their distribution intervals postulated formerly.     

罗云山山前断裂带阶地调查研究及其构造意义

Located at the west of the Linfen basin, the Luoyunshan piedmont fault zone controls the western boundary of the basin. According to the measurements of the terraces in eight gullies along the Luoyunshan fault zone, five levels of terraces, namely T1～T5 have developed in these gullies. The heights of terraces T1, T2, T3, T4 and T5 are about 3m, 8～10m, about 20m, about 30m and 40～50m, respectively. The dating data of the terraces and investigation of the faulted landforms show that the Luoyunshan fault zone has experienced much activity since the Late Quaternary. The uplift rate of the terraces was 0.41mm/a since the Middle-Late Pleistocene, and 0.75mm/a since the Holocene. The increasing trend of uplift rate of the terraces along the Luoyunshan fault zone from the Middle-Late Pleistocene to Holocene indicates the tendency of gradual tectonic uplift of the fault zone since the late Quaternary. This is in good agreement with the increasing trend of subsidence rate of the Linfen basin from the Late Pleistocene to Holocene.     

Seismicity and neotectonic uplift in the Augrabies Falls National Park,Namaqualand,Northern Cape,South Africa

Gneissic rocks in the Augrabies Falls National Park are part of the Proterozoic Namaqua-Natal mobile belt. Finding neotectonic evidence in old terranes is always not an easy task. In South Africa, the mid-Miocene is believed to be the beginning of neotectonics. This study investigated the occurrence and recurrence of earthquake activity, occurrence of faulting, jointing, uplift, and potholes in the gneisses cropping out around the Augrabies Falls area that may account for neotectonics. A historic seismic event obtained from the United States Geological Survey(USGS), and seismic epicenters downloaded in October 2015 from IRIS earthquake browser and overlaid on a satellite image with digitised faults and lineaments,indicates that the area is seismically active and is a zone of seismic risk. Potholes occurring today on a dry surface at approximately 613 m above sea level are a direct consequence of the Griqualand-Transvaal neotectonic uplift,which generated a major fault along which water flows continuously. It is concluded that the Augrabies Falls National Park area is a zone of neotectonics. This zone should not be considered for the storage of nuclear wastes.     

塔北隆起古生代构造样式和构造反演

塔北隆起是塔里木盆地的主要含油气区,笔者利用地震剖面解释和平衡剖面技术对塔北隆起构造变形和构造演化进行了研究.塔北隆起构造变形存在明显的构造差异,西部英买力地区主要发育盖层滑脱式逆冲断层褶皱和"y"型压扭断层,而其东部主要发育基底卷入式逆断层及断层传播褶皱和反冲断层构造.造成塔北隆起东、西构造样式差异的机理主要有两点:一是东部地区对震旦纪一早奥陶世正断层在后期挤压作用下反转,二是英买力地区中寒武统盐层的发育.塔北隆起地区古生代构造演化也存在着一定的差异,塔北隆起东部震旦纪一早奥陶世发育大型正断层构造,而英买力地区为稳定碳酸盐岩台地;晚奥陶世至泥盆纪,塔北隆起东部牙哈断层发生反转,轮台凸起隆升,而英买力地区位于隆起的斜坡部位;石炭纪至二叠纪,塔北隆起东部大规模抬升,剥蚀严重,出露变质基底,英买力地区接受强烈的变形作用,主要发育盖层滑脱式逆断层和褶皱构造.     

OSL chronology of Quaternary terraced deposits outcropping between Mt. Etna volcano and the Catania Plain (Sicily,southern Italy)

In this paper we tested the applicability of the Optically Stimulated Luminescence (OSL) technique through Single-Aliquot Regenerative-dose (SAR) protocol, on single grain quartz extracted from alluvial–coastal sediments. Five samples were collected from deposits belonging to a flight of seven orders of coastal–alluvial terraces outcropping in the area between Mt. Etna volcano and the Catania Plain (Sicily, southern Italy), at the front of the Sicilian fold and thrust system. After various performance tests, we obtained OSL ages ranging between 240 ± 12 and 80 ± 4 ka, consistent with the normal evolutionary model of a terraced sequence, moving from the highest to the lowest elevation. Obtained data allowed us to determine a mean uplift rate of 1.2 mm/year during the last 240 ka, mostly related to regional uplift processes coupled with sea-level changes. Moreover, terraces belonging to the two highest orders are folded, forming a large anticline. According to our results, the frontal thrust of the Sicilian chain was active between 236 and 197 ka ago, even though seismological and geodetic data suggest current activity to the back.     

四川盆地南部地区新生代隆升剥露研究——低温热年代学证据

本文通过背斜褶皱变形与低温热年代学年龄(磷灰石和锆石(U-Th)/He、磷灰石裂变径迹)端元模型研究,约束低起伏度、低斜率地貌特征的四川盆地南部地区新生代隆升剥露过程.四川盆地南部沐川和桑木场背斜地区新生代渐新世-中新世发生了相似的快速隆升剥露过程(速率为~0.1 mm/a、现今地表剥蚀厚度1.0~2.0 km),反映出盆地克拉通基底对区域均一性快速抬升冷却过程的控制作用.川南沐川地区磷灰石(U-Th)/He年龄值为~10-28.6 Ma, 样品年龄与古深度具有明显的线性关系,揭示新生代~10-30 Ma以速率为0.12±0.02 mm/a的稳态隆升剥露过程.桑木场背斜地区磷灰石裂变径迹年龄为~36-52 Ma,古深度空间上样品AFT年龄变化不明显(~50 Ma)、且具有相似的径迹长度(~12.0 μm).磷灰石裂变径迹热演化史模拟表明桑木场地区经历三个阶段热演化过程:埋深增温阶段(~80 Ma以前)、缓慢抬升冷却阶段(80-20 Ma)和快速隆升剥露阶段(~20 Ma-现今),新生代隆升剥露速率大致分别为~0.025 mm/a和~0.1 mm/a.新生代青藏高原大规模地壳物质东向运动与四川盆地克拉通基底挤压,受板缘边界主断裂带差异性构造特征控制造就了青藏高原东缘不同的边界地貌特征.     

塔北隆起雅克拉油气田原油成因特征

针对雅克拉油气田多个含油气层位的原油,进行了一系列的地球化学测试分析,对雅克拉油气田原油的地球化学特征、成因特征进行了解剖。研究结果表明,雅克拉油气田深浅不同层位原油轻烃组成与轻烃单体烃碳同位素、类异戊二烯烷烃组成以及原油与馏分碳同位素组成具有明显的海相原油特征;深浅层原油三环萜烷、C₂₈甾烷、三芳甾烷和甲基三芳甾烷以及原油与馏分碳同位素组成皆具有典型上奥陶统来源油的特征,与寒武-下奥陶统来源油特征差异明显,暗示雅克拉油气田原油来源于上奥陶统烃源层。