十万大山地区构造演化和含油气评价

十万大山盆地地构造演化过程为：在华夏被动大陆边缘发育的弧间洋盆基础上,经东吴、印支和燕山期碰撞造山运动,形成晚古生代－中生代前陆盆地,又经过短暂的弧后陆内裂谷阶段,形成了喜马拉雅期右列张扭性盆地。共原型盆地经历了镀嵌、交错、披盖、再镶、交错、披盖、再镶嵌等四个叠置过程。其构造发展由正反转向负反转变化,以多次构造运动叠加后保留的基底部分卷入的冲断－推覆构造形成占主导,并发育典型的楔状前陆盆地、斜坡带     

遗迹化石与潮控滨线海泛面的识别及准层序相组合──以塔里木盆地下志留统塔塔埃尔塔格组为例

塔里木盆地下志留统塔塔埃尔塔格组主要由潮坪沉积组成。根据遗迹化石与沉积特征,固底控制的遗迹化石Ｇｙｒｏｌｉｔｈｅｓ常常与沉积性不连续面（海泛面）有关,潮控滨线中的准层序由三类岩相组成,其中含砾砂岩相（相Ａ）为潮道沉积,未见遗迹化石;含交错层理细砂岩相（相Ｂ）为砂坪沉积,仅见少量的遗迹化石Ｓｋｏｌｉｔｈｏｓ;强生物扰动粉砂岩、泥岩相（相Ｃ）为砂、泥混合坪沉积,发育有丰富的遗迹化石,代表Ｓｋｏｌｉｔｈｏｓ－Ｃｒｕｚｉａｎａ混合遗迹相。     

中亚干旱区的荒漠化与土地利用

笔者在实地考察、航片和卫星影像判读的基础上,参考国际上最新研究成果,以咸海盆地和古丝绸之路沿线地区为例,分析探讨了中亚干旱区荒漠化发生的过程、机制及其对自然和人文环境系统的影响和危害。由于大量从阿姆河和锡尔河引水扩大灌溉、浪费水源及单一农作物种植,使1960年时还为世界第四大湖的威海水面和蓄水大减,在干枯了的湖底和周围耕地上荒漠化快速发展,造成自然环境系统的严重退化和社会经济的巨大损失。虽然在我国丝绸之路沿线地区自古以来就有荒漠化现象,但荒漠化的规模在近40年来发生了根本性变化。塔里木河下游和克里雅河下游及玛纳斯河下游的湖泊干枯,植被退化甚至消失,不少野生动物灭绝。     

THE PALEOSEISMIC SURFACE RUPTURE AT SOUTH OF CENTRAL ALTYN TAGH FAULT AND ITS TECTONIC IMPLICATION

In this study, we described a 14km-long paleoearthquakes surface rupture across the salt flats of western Qaidam Basin, 10km south of the Xorkol segment of the central Altyn Tagh Fault, with satellite images interpretation and field investigation methods. The surface rupture strikes on average about N80°E sub-parallel to the main Altyn Tagh Fault, but is composed of several stepping segments with markedly different strike ranging from 68°N~87°E. The surface rupture is marked by pressure ridges, sub-fault strands, tension-gashes, pull-apart and faulted basins, likely caused by left-lateral strike-slip faulting. More than 30 pressure ridges can be distinguished with various rectangular, elliptical or elongated shapes. Most long axis of the ridges are oblique(90°N~140°E)to, but a few are nearly parallel to the surface rupture strike. The ridge sizes vary also, with heights from 1 to 15m, widths from several to 60m, and lengths from 10 to 100m. The overall size of these pressure ridges is similar to those found along the Altyn Tagh Fault, for instance, south of Pingding Shan or across Xorkol. Right-stepping 0.5~1m-deep gashes or sub-faults, with lengths from a few meters to several hundred meters, are distributed obliquely between ridges at an angle reaching 30°. The sub-faults are characterized with SE or NW facing 0.5~1m-high scarps. Several pull-apart and faulted basins are bounded by faults along the eastern part of the surface rupture. One large pull-apart basins are 6~7m deep and 400m wide. A faulted basin, 80m wide, 500m long and 3m deep, is bounded by 2 left-stepping left-lateral faults and 4 right-stepping normal faults. Two to three m-wide gashes are often seen on pressure ridges, and some ridges are left-laterally faulted and cut into several parts, probably owing to the occurrence of repetitive earthquakes. The OSL dating indicates that the most recent rupture might occur during Holocene.
Southwestwards the rupture trace disappears a few hundred meters north of a south dipping thrust scarp bounding uplifted and folded Plio-Quaternary sediments to the south. Thrust scarps can be followed southwestward for another 12km and suggest a connection with the south Pingding Shan Fault, a left-lateral splay of the main Altyn Tagh Fault. To the northeast the rupture trace progressively veers to the east and is seen cross-cutting the bajada south of Datonggou Nanshan and merging with active thrusts clearly outlined by south facing cumulative scarps across the fans. The geometry of this strike-slip fault trace and the clear young seismic geomorphology typifies the present and tectonically active link between left-lateral strike-slip faulting and thrusting along the eastern termination of the Altyn Tagh Fault, a process responsible for the growth of the Tibetan plateau at its northeastern margin. The discrete relation between thrusting and strike-slip faulting suggests discontinuous transfer of strain from strike-slip faulting to thrusting and thus stepwise northeastward slip-rate decrease along the Altyn Tagh Fault after each strike-slip/thrust junction.     

Transgressions-régressions, variations eustatiques et influences tectoniques de l'Aptien au Maastrichtien dans le Bassin de Paris occidental et sur la bordure du Massif armoricain

La série sédimentaire du Crétacé moyen et supérieur étudiée dans l'Ouest du Bassin de Paris et sur la bordure du Massif armoricain comporte sept pulsations transgressives qui peuvent être reconnues en fonction de la disposition géomètrique des dépôts et de l'enchaînement vertical des faciès.Les épisodes transgressifs atteignent leur phase paroxysmale, en alternance avec des stades de régression, successivement:

1. (1) à la fin de l'Aptien supérieur —(régression début Albien)

2. (2) au milieu de l'Albien supérieur —(régression fin Albien-début Cénomanien)

3. (3) au milieu du Cénomanien inférieur —(régression fin Cénomanien inférieur)

4. (4) à la fin du Cénomanien moyen —(régression fin Cénomanien)

5. (5) au milieu du Turonien inférieur —(régression du Coniacien)

6. (6) au Santonien puis Campanien —(régression fin Campanien)

7. (7) au Maestrichtien —(régression fin Maastrichtien)

Ces dépôts crétacés présentent une succession de séquences séparées par des discontinuités et des surfaces d'érosion plus ou moins marquées. Les caractères et la répartition de ces séquences sont analysés en domaine de sédimentation terrigène littorale et dans le bassin envahi par la craie. Il est alors tenté d'interpréter les variations bathymétriques d'une part en fonction d'évènements tectoniques locaux, d'autre part en relation avec des variations eustatiques plus générales.Middle and Upper Cretaceous deposits studied in the western Paris Basin and on the Armorican Massif margin show seven transgressive pulses that can be detected in the geometrical arrangement of the sedimentary bodies and the vertical succession of facies.The transgressive episodes, each delimited by a regressive phase, reached their peak during:

1. (1) late Late Aptian —(Early Albian regression)

2. (2) mid Late Albian —(Late Albian-Early Cenomanian regression)

3. (3) mid Early Cenomanian —(late Early Cenomanian regression)

4. (4) late Middle Cenomanian —(Late Cenomanian regression)

5. (5) mid Early Turonian —(Coniacian regression)

6. (6) Santonian-Campanian —(Late Campanian regression)

7. (7) Maastrichtian —(Late Maastrichtian regression)

The Cretaceous sediments occur as a series of sequences, separated by more or less important discontinuities and erosion surfaces. The features and distribution of these sequences have been studied in the nearshore region of terrigenous sedimentation and in the Chalk basin. An attempt is made to relate the bathymetric changes to either tectonic movements or more widespread eustatic oscillations.     

Cretaceous transgressions and regressions on the Russian Platform, in Crimea and Central Asia

This paper is a brief explanation of the diagrams of the Cretaceous transgressions and regressions on the Russian Platform, in the Crimea (Figures 1–3) and some regions of central Asia—the western flanks of the Tien Shan mountains, the Fergana basin, the Zeravshan-Gissar and Alaj mountains, and the Northern Pamirs (Figures 5–7).Internationally recognized stages are employed. They are interpreted by Sasonova (1967) for the Lower Cretaceous (K₁) of the Russian Platform, by Naidin (1977) for the Upper Cretaceous (K₂) of the Platform and the Crimea, by Djalilov (1971) and Pojarkova (1976) for the Upper Cretaceous of central Asia. General data on the stratigraphy of the Cretaceous of central Asia may be found in Anon 1977.     

Theoretical analysis of telluric anomaly of a basin structure

The solution of a boundary value problem modelling a two-dimensional basin structure has been obtained by using the Schwartz-Christoffel conformal transformation technique and numerical methods of solving non-linear differential equations. Utilizing this solution, the telluric field and its first horizontal derivative have been theoretically computed for field directions perpendicular to the strike of the structure. On the basis of systematic analysis of a large number of such anomaly curves, two nomograms have been prepared to be used in the quantitative interpretation of telluric data. An interpretation procedure to evaluate the geometric parameters of the basin from the observed telluric data is outlined. This procedure is demonstrated on an actual field example.     

Correlation of T-log with E-log in coal-bearing formations

The profile of temperature gradient versus depth (T-log) has been found to be very useful for correlation with electrical resistivity log (E-log) in coal-bearing formations. A positive correlation between electrical resistivity and thermal resistivity is observed in coal sections whereas a negative correlation is found in sandstone/shale beds, thus helping in coal prospect evaluation. T logs have been used to correct the location of coal bed which had apparently been misinterpreted by the E-log. Hole to hole correlation of T-log and E-log is found to be excellent and it is observed that thermal resistivity characteristics of given formations remain fairly uniform. A rough estimation of coal grade is possible from the detailed study of the T-logs. Abrupt changes of temperature gradient as also its reversals have been observed in burnt coal sections.     

Atmospheric noble gases in volcanic glasses from the southern Lau Basin: origin from the subducting slab?

Noble gas concentrations and isotopic compositions have been determined for four submarine volcanic glasses from the Valu Fa Ridge (VFR) in the southern Lau Basin. The samples are the least differentiated ones from this area, and they display enrichments in fluid-mobile elements similar to the nearby island arc. ³He/⁴He ratios are slightly below average MORB (6.8–7.8 times atmospheric), whereas Ne, Ar, Kr, and Xe have isotopic compositions very similar to air. Together with previously published data from the Valu Fa Ridge and other spreading segments in the Lau Basin, our data show a systematic latitudinal variation of increasing Ne, Ar, Kr, and Xe abundances from north to south as well as Ne and Ar isotopic compositions changing from MORB-like to atmosphere-like in the same direction. Moreover, isotopic compositions and noble gas abundances of the lavas correlate strongly with Ba/Nb ratios and H₂O concentrations. Based on these observations and mass balance arguments, we propose that the atmospheric noble gases come from the subducting oceanic crust and are not due to shallow contamination with air dissolved in seawater or assimilation of old crust. Our data suggest that the noble gases released from the subducting slab are atmospheric and thus contain little or no solar He and Ne. In addition to the fact that ratios of He to heavy noble gases are small in aged ocean crust, He has possibly fractionated from the other noble gases due to its higher diffusivity, and thus He transport from the subducting slab into the mantle wedge is probably insignificant. We propose that the ³He/⁴He ratios lower than MORB observed in the VFR lavas result from radiogenic ingrowth of He in a highly depleted, and hence degassed, mantle wedge after the enrichment of U and Th released from the downgoing slab.     

Impact of climate change on 24‐h design rainfall depth estimation in Qiantang River Basin,East China

The frequency and magnitude of extreme meteorological or hydrological events such as floods and droughts in China have been influenced by global climate change. The water problem due to increasing frequency and magnitude of extreme events in the humid areas has gained great attention in recent years. However, the main challenge in the evaluation of climate change impact on extreme events is that large uncertainty could exist. Therefore, this paper first aims to model possible impacts of climate change on regional extreme precipitation (indicated by 24‐h design rainfall depth) at seven rainfall gauge stations in the Qiantang River Basin, East China. The Long Ashton Research Station‐Weather Generator is adopted to downscale the global projections obtained from general circulation models (GCMs) to regional climate data at site scale. The weather generator is also checked for its performance through three approaches, namely Kolmogorov–Smirnov test, comparison of L‐moment statistics and 24‐h design rainfall depths. Future 24‐h design rainfall depths at seven stations are estimated using Pearson Type III distribution and L‐moment approach. Second, uncertainty caused by three GCMs under various greenhouse gas emission scenarios for the future periods 2020s (2011–2030), 2055s (2046–2065) and 2090s (2080–2099) is investigated. The final results show that 24‐h design rainfall depth increases in most stations under the three GCMs and emission scenarios. However, there are large uncertainties involved in the estimations of 24‐h design rainfall depths at seven stations because of GCM, emission scenario and other uncertainty sources. At Hangzhou Station, a relative change of ?16% to 113% can be observed in 100y design rainfall depths. Copyright © 2012 John Wiley & Sons, Ltd.