Initiation and Development of the Late Cenozoic Uplift of Daluo Mountains, Northeastern Margin of the Tibetan Plateau

Daluo Mountains lie at front of the arcuate tectonic belt at the northeastern margin of the Tibetan Plateau, and are the landform boundary zone between the active Tibetan Plateau and the stable North China Craton. Studying of the late Cenozoic uplift evolution of Daluo Mountains is important for understanding the expansion mechanism of the northeastern margin of the Tibetan Plateau and its influence on the western North China Craton. In this study, the late Cenozoic uplift of Daluo Mountains is constructed from the development of the late Cenozoic alluvial fan around Daluo Mountains. The entire sedimentary sequence and framework of the fan was revealed by the newly obtained drilling core data. The cosmogenic nuclide, optically stimulated luminescence, and detrital zircon U-Pb dating results provide new evidences for discussion about the initial timing of the late Cenozoic uplift of Daluo Mountains and the key stages of uplift during the Pleistocene. The late Cenozoic alluvial fan at front of Daluo Mountains overlies a set of fluvial-facies strata; therefore, development of the alluvial-fan marks the start of late Cenozoic uplift of Daluo Mountains. The timing of this event can be constrained to ~4.64 Ma. Two extensive gravel layers (dated to ca. 0.76–0.6 Ma and ~0.05 Ma) developed during the Pleistocene, indicating two episodes of considerable uplift. This study provides a new time scale for the uplift and expansion of the arcuate tectonic belt at the northeastern margin of the Tibetan Plateau.     

东非鲁伍马盆地深水X气藏海底扇储层构型研究:重力流—底流交互作用的指示意义*

底流在陆缘深水环境下广泛存在,可对深水沉积过程及砂体分布产生重要影响。前人对重力流与底流的交互作用机制及沉积产物开展了大量研究,但目前有关底流改造型的海底扇储层构型模式仍然研究不够深入。东非鲁伍马盆地是当前重力流—底流交互作用研究的热点地区,文中以其代表性的下始新统海底扇水道体系为例,综合岩心、测井及三维地震资料开展储层构型精细表征,建立重力流—底流交互作用下的海底扇水道体系构型模式。研究表明,目标水道体系内部发育水道、溢岸及朵叶3种构型要素,其中水道可分为水道复合体、单一水道及其内部不同级次的构型单元。底流对细粒物质的搬运可形成非对称的溢岸沉积,导致水道复合体之间呈逆底流侧向迁移叠置样式,其间泥岩隔层容易保存; 单一水道之间呈顺水道纵向迁移或逆底流侧向迁移样式,其中纵向迁移部位水道切叠连通,而侧向迁移部位容易保存泥质侧向隔挡体。受重力流沉积演化的影响,单一水道内部充填由砂泥交互型逐渐演化为富砂型,且在水道弯曲段的轴部砂体最为发育。     

准噶尔盆地乌尔禾油田百口泉组冲积扇沉积特征及油气勘探意义

通过分析岩心、铸体薄片及测井等资料,认为准噶尔盆地乌尔禾油田百口泉组发育一套典型的退积型冲积扇沉积。百口泉组中下部发育扇中亚相,上部发育扇缘亚相,反映研究区在三叠纪早期,湖平面逐渐升高,可容空间与沉积物补给速率比值（A/S比值）逐渐增大的沉积特征。沉积微相类型包括辫状河道充填、筛状沉积、泥石流沉积及片流沉积。综合构造、测试及试油等资料,认为扇中亚相辫状河道充填为油气富集的有利储集相带,控制了油气富集的规模与油藏边界。在有利相带控制油藏分布的结论指导下部署钻探的多口评价井在百口泉组均获得工业油流,有效地指导油田现场生产。     

Architecture and sedimentology of the Kerinitis Gilbert‐type fan delta,Corinth Rift,Greece

The Kerinitis Delta in the Corinth Rift, Greece, is a footwall derived, coarse‐grained, Gilbert‐type fan delta deposited in the hangingwall of a linked normal fault system. This giant Gilbert‐type delta (radius 3·8 km, thickness > 600 m) was supplied by an antecedent river and built into a brackish to marine basin. Although as yet poorly dated, correlation with neighbouring deltas suggests that the Kerinitis Delta was deposited during a period of 500 to 800 ka in the Early to early Middle Pleistocene. Facies characterizing a range of depositional processes are assigned to four facies associations (topset, foreset, bottomset and prodelta). The dominantly fluvial topset facies association has locally developed shallow marine (limestone) and fluvial‐shoreface sub‐associations. This delta represents a subsidence‐dominated system in which high fault displacement overwhelmed base‐level falls (creation of accommodation predominantly ≥ 0). Stratal geometries and facies stacking patterns were used to identify 11 key stratal surfaces separating 11 stratal units. Each key stratal surface records a landward shift in the topset breakpoint path, indicating a rapid increase in accommodation/sediment supply. Each stratal unit records a gradual decrease in accommodation/sediment supply during deposition. The cyclic stratal units and key stratal surfaces are interpreted as recording eustatic falls and rises, respectively. A 30 m thick package of foresets below the main delta records the nucleation of a small Proto‐delta probably on an early relay ramp. Based on changes in stratal unit geometries, the main delta is divided into three packages, interpreted as recording the initiation, growth and death of the controlling fault system. The Lower delta comprises stacked, relatively thin, progradational stratal units recording low displacement on the young fault system (relay ramp). The Middle delta comprises vertically stacked stratal units, each recording initial aggradation–progradation followed by progradation; their aggradational component increases up through the Middle delta, which records the main phase of increasing rate of fault displacement. The Upper delta records pure progradation, recording abrupt cessation of movement on the fault. A major erosion surface incising basinward 120 m through the Lower and Middle delta records an exceptional submarine erosion process (canyon or delta collapse).     

新疆柴窝堡盆地地下水化学及稳定同位素研究

地下水是维持乌鲁木齐河流域社会经济发展和生态系统的最重要的水源,尤其是柴窝堡盆地因大量开采使得地下水水位下降、湖面萎缩,地下水系统动态特征发生了变化,所以研究区内地下水水流系统及其补径排关系对于深入研究盆地地下水流系统特征和合理开发利用地下水水资源能够提供重要的基础资料,尤其是对调整地下水资源的开采布局具有现实意义。本次研究主要以地质、水文地质背景资料为基础,结合地下水补给环境的差异,利用水化学和水的稳定同位素进行示踪研究,确定了柴窝堡盆地地下水的补给来源和排泄途径,区分出盆地排泄带不同点的补给区,包括东山、南山和西山补给区,对同一补给区又细分出不同的水流系统。     

TEM中心回线中—远带响应特征

近20年来,中心回线观测已进入全域时段,然而有关中—远带响应特征的文章极为少见,致使用户困惑,比如晚延时响应值大于早延时响应值(ε-上凸)、在同一测点2种仪器系统观测结果相差太大等。对此笔者做了详细分析。结果表明,中—远带响应特征基本为4种,ε-上凸只是其中之一,导致所测响应出现差别的主要原因是接收线圈延时。因此,若工作于中—远带,必须确切测定线圈延时,合理选择发射回线边长。     

准噶尔盆地乌夏逆冲断裂带三叠纪-侏罗纪构造控扇规律及时空演化

通过研究准噶尔盆地西北缘乌夏逆冲断裂带三叠系-侏罗系构造层序、沉积相及断裂特征,认为三叠纪-侏罗纪时期是在二叠纪前陆盆地完全消亡、洋壳俯冲彻底结束后发育的板内挤压陆内坳陷盆地,主要发育冲积扇-扇三角洲-辫状河-湖泊沉积体系,其中扇体发育代表了最典型的沉积特征,反映了构造活动的期次和强度,具有"构造指相性",从下至上划分为三叠系亚构造层序、侏罗系八道湾组-西山窑组亚构造层序和侏罗纪头屯河组-齐古组亚构造层序。分析表明三叠纪-侏罗纪扇体叠置迁移的总体趋势为:T1b-J1b期在扇体总体由盆内向盆缘退缩的背景下,呈现并夹杂两个短期内由盆缘向盆内再盆缘的进退波动变化(T1b-T2k1期、T3b2-J1b1期),即三叠纪-侏罗纪扇体的沉积展布具后退式夹短暂推进式叠置迁移特点。相应地,三叠纪-侏罗纪以形成近东西向和东西向断裂为主,并从盆地内向山前方向依次后展式发育,其间夹杂短暂的前展式发育特征,构造活动强度逐渐由南向北、由西向东迁移。因此,绝大多数同生断裂控制了扇体的沉积边界和分布,部分控制了其厚度和发育方向,扇体的迁移与控扇断裂的活动迁移具有很好的吻合性,断裂活动是控制乌夏地区沉积的主要因素。最终建立了三叠纪-侏罗纪构造控扇响应模式,并划分为三个发育阶段:早三叠世坳陷初期旱地扇发育阶段、中晚三叠世坳陷鼎盛期湿地扇发育阶段、扇三角洲发育阶段和侏罗纪的坳陷填充期陆上平原发育阶段,从早至晚,气候经历了一个由干旱到潮湿,由潮湿变干旱再到潮湿的旋回过程。     

秦岭北麓断裂带晚第四纪活动的地貌表现

本区地貌特征反映秦岭北麓断裂带的活动特点是：①第四纪以来主要发生垂直运动，其活动性质与程度有差异性、阶段性。第一、二级阶地的形态和年代资料表征秦岭北麓断裂带晚更新世和全新世垂直位错幅度和平均速率。②河流阶地在上升盘出口处高度大，而向上游逐渐减小，反映第四纪以来，秦岭断块山地继续发生由北向南的掀斜运动。③被断层切割的冲洪积扇体的结构和堆积层的产状特征，反映出山麓带多发育铲形断层。     

Subaerial terminoglacial fans II: a semi-quantitative sedimentological analysis of the middle and distal environments

Twenty-five fans in NE Poland, formed under subaerial terminoglacial (previously called ice-contact) conditions, were investigated to model the dominant genetic processes involved. These fans show, as do other types, a proximal, a middle and a distal subenvironment. It is found, however, that the characteristics of these subenvironments as present in subaerial terminoglacial fans differ in several respects from those in fans formed under other climatic conditions. The present study deals with the middle and distal subenvironments. These appear to be much less complex than the proximal subenvironment in this type of fan. The middle terminoglacial fan comprises two sandy facies, characterized by unchannelized transport (mainly sheet floods) and stream flows. The distal terminoglacial fan is characterized by one (sandy/silty) facies, resulting from unchannelized currents and from settling in ephemeral ponds; braided streams play a secondary part in this fan subenvironment. The characteristics of the middle and distal fan subenvironments are described and illustrated, as is the facies from the distal subenvironment. Their vertical and lateral relationships are presented in a facies model.     

Water table variations in Atacama Desert alluvial fans: discussion of “Evidence of short-term groundwater recharge signal propagation from the Andes to the central Atacama Desert: a singular spectrum analysis approach”*

ABSTRACT

Using a statistical approach, Scheihing attempts to demonstrate the direct influence of recharge events in the Precordillera and the Andean Piedmont on water table variations in downstream alluvial fans. The author “unquestionably” discards the existence of ephemeral recharge processes in alluvial fans although they are frequently impacted by major floods. However, the author does not consider previous publications about recharge processes in arid alluvial fans, the hydraulic setting of the Pampa del Tamarugal Aquifer (PTA) and anthropogenic pressure changes in the PTA. Because the sustainable management of groundwater resources in drylands depends on a good understanding of hydrogeological processes, we propose a thorough reinterpretation of the short- and long-term PTA water table variations addressed by the author. In this comment, we illustrate the limits of the sole use of a statistical approach for characterizing both recharge processes and factors controlling the water table variations in the Atacama Desert.