Forced regressive shoreface sandstone from Himalayan foreland: Implications to early Himalayan tectonic evolution

Sedimentology and sequence stratigraphic analysis of the ∼ 31 Ma old marker White sandstone unit from the Subathu Sub-basin, NW Himalayan foreland, suggest it to be a forced regressive wedge (FRW) formed during the transition from the marine Subathu Formation to the continental Dagshai Formation. The FRW is bounded between the “Surf diastem” below and type 1 unconformity at the top and differs from RSME (regressive surface of marine erosion, occurring below) bounded FRWs described from other classical coastal/foreland settings. Correct identification of bounding surfaces of a FRW has an important implication to the estimation of rate of relative sea-level (RSL) fall. A faster rate of RSL fall, higher than the sedimentation rate, has been postulated for the erosion of the lower shoreface and RSME. Using the logged thickness of the Subathu/Dagshai transition zone including the White sandstone (bounded between the “Surf diastem” and unconformity), available chronology and eustatic sea-level fall (0.023 mm/year at 31 Ma), a higher RSL fall than the sedimentation rate (0.07 mm/year) has been inferred during the deposition of the White sandstone. Petrography of sandstones and their Sr and Nd isotopic compositions indicate a major provenance switch-over from dominant mafic/ultramafic to metamorphic source from White sandstone (∼ 31 Ma) onwards attesting the link between hinterland tectonics, provenance and forced regression. The provenance switch-over at 31 Ma was earlier inferred to be driven by proto-Himalayan thrust propagation in the foreland. Using a simple isostatic model, on the contrary, a mechanism of accelerated surface uplift (at a rate of > 0.10-0.15 mm/year) is suggested for both provenance change and forced regression.     

雅鲁藏布江大拐弯北段区域工程地质及其对地质灾害发育的影响

川藏公路然乌-鲁朗段位于雅鲁藏布江大拐弯北部,是地质灾害频发的地区,而地质灾害的发生受当地的地质、气候、水文、人类活动等多种因素的影响,其中地质条件是控制因素。研究区位于东喜马拉雅构造结北缘,是地质构造活动最强烈的地区。在地质构造上,东喜马拉雅构造结属于冈底斯、雅鲁藏布和喜马拉雅三个构造单元。区内构造的形成经历了3个时期7个阶段。川藏公路然乌-鲁朗段的地层属于冈底斯-念青唐古拉区中的拉萨-波密分区,第四纪冰碛发育。由于强烈的地质构造活动,区内断层、褶皱等构造发育,许多断裂仍在活动,尤其是嘉黎断裂。由于地质灾害的形成需要一定的条件,并受地质条件控制,因此区内地质灾害的分布具有明显的空间特征。     

粤港澳大湾区港口供应链优化研究

为充分发挥粤港澳大湾区港口的竞争优势,促进港口经济的协调发展,文章基于粤港澳大湾区主要港口的实际情况,构建供应链博弈模型并进行数值仿真,研究相关因素对深圳港和香港港绩效的影响。研究结果表明:随着商品价格和库存成本的提高,货物从深圳港向香港港转移,但转移幅度逐渐趋缓;深圳港在中低端商品的货源收集方面具有明显的竞争优势,而香港港对高端商品的吸引力更强;货运结构逐渐向中高端商品过渡对于提高港口收益具有促进作用,其中深圳港应通过降低商品库存成本而降低经营风险;深中通道和港珠澳大桥通车有效缩短腹地运输时间,对于绝大部分商品价格和库存成本组合都将提高粤港澳大湾区港口的总收益。     

Author Index for Journal of Mountain Science Volume 11,2014,pp 1-1656

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Sequence stratigraphic modelling and reservoir architecture of the shallow marine successions of Baram field,West Baram Delta,offshore Sarawak,East Malaysia

The Baram Delta Province is located in the northern part of Sarawak (West Baram Delta) and extends north-eastward into Brunei and further into the south-western part of Sabah (East Baram Delta). The delta is a Neogene basin which developed over an accretionary wedge implying Cretaceous to Eocene sediments during the Late Eocene to Late Miocene times (Tongkul, 1991; Hutchison et al., 2000; Morley et al., 2003; Sapin et al., 2011).Facies and well log analyses were carried out on core and well data for the Late Miocene successions of Baram field, a medium-sized oilfield located in the north-eastern flank of the Baram Delta Oil Province, offshore Sarawak. A numerical model of sea-level fluctuations and progradational basin-fill was generated using the Clastic Modeling Program (Hardy and Waltham, 1992a and 1992b; Waltham, 1992) software to evaluate the possible controls of sea-level changes in the development of the siliciclastic successions and their bounding surfaces. This model was based on four lines of evidence, namely core data, fieldwide wireline logs correlation, seismic sections and average thickness variations across the field.Cored intervals of the Upper Cycle V (Late Miocene) display reservoir successions dominated by thick swaley cross-stratified (SCS) sandstones, thin hummocky cross-stratified sandstones and other shallow marine, wave and storm-dominated facies, interbedded with laminated shelfal mudstones. The vertical facies organisation suggests deposition during shoreface progradation associated with a fall of relative sea level.Analysis and correlation of well logs reveal stacking patterns comprising three scales of depositional cyclicity: the parasequences (∼10–∼30 m thick), the parasequence sets (∼45–∼130 m thick) and the major cycles (∼600–800 m thick).Field-wide, dip-oriented seismic sections show very well-developed horizontal to slightly upward convex layers traceable over great distances, which suggests a ramp-type margin, in which the basin floor dipped gradually seaward and lacked a distinct shelf-slope margin.The evidences gathered demonstrate that the deposition and build-up stratigraphy of the Late Miocene sedimentary successions could have been strongly controlled by superimposed short-term, medium-term and long-term sea-level changes.The simulated sea level and sedimentary basin-fill model, generated by the Clastic Modelling Program, match to the well log correlation. This model illustrates that high frequency sea-level fluctuations enable sands to be distributed over large areas within a shallow, low gradient shelf. Our study shows that integrated studies incorporating cores, well logs, seismic sections and simulated models can be employed as important tools for correlation and reservoir modelling.     

Multi-sourced depositional sequences in the Neogene to Quaternary succession of the Venice area (northern Italy)

The Plio-Pleistocene succession of the Venice area represents part of the infill of a foreland region located between three mountain chains: the Northern Apennines, the Southern Alps and the Dinarides. This structural setting favored the development of a complex stratigraphic architecture of the succession, mostly due to the conveying of sediments from the Southern Alps to the north and the Northern Apennines to the south, in particular since the activation of strong subsidence related to the NE-ward migration of the Apennine foredeep in the early Pleistocene. Accordingly, the studied succession is composed of five third-order sequences mostly controlled by tectonics, the most recent of which display complex patterns due to the interfingering of sedimentary bodies showing contrasting directions of progradation and pinch-out. Despite this, the sequence stratigraphic method still can be applied in the present context, allowing to recognize diagnostic stratal architectures and reconstruct the relative sea-level history of the region. Moreover, the recognized peculiar stratigraphic architecture of the basin fill may serve as an analogue that needs to be taken into account to predict the distribution of porous coarse-grained sedimentary units in similar contexts, aiding for a profitable exploration and production of reservoirs and source/sealing rocks.     

3D architecture of Quaternary sediment along the NW Atlantic Moroccan Rharb continental shelf: A stratal pattern under the dual control of tectonics and climatic variations

This study focuses on the evolution of the Atlantic NW Moroccan Rharb continental shelf during the Neogene and Quaternary. This region is part of a foreland basin bounded by the Rif mountain belt and thus provides an interesting geological setting to study the interactions between eustasy and tectonics and the driving mechanisms controlling stratigraphic patterns. The results are supported by an interpretation of new data including high-resolution seismic lines coupled with an interpretation of industrial seismic lines and detailed logs of industrial wells completed by micropaleontologic analysis of cuttings. The stratigraphy reveals a succession of three mega sequences related to the transition from an underfilled to an overfilled stage reflecting the long-term evolution of the foreland system. Moreover, evidence of cyclical sea-level changes are visible in the upper megasequence composed of three depositional sequences assumed to be fourth-order sequences generated in response to the most recent 100-ka glacio–eustatic cycles. This study also shows the peripheral deformation of the Rharb shelf responsible for changes in the geometry of the deposits and thicknesses of the sedimentary fill during the Pliocene and Pleistocene. The most important change was triggered by the uplift of the Lallah Zahra Ridge corresponding to a major Quaternary kinematic boundary and the broad uplift of the southern shelf interpreted as a flexural uplift of the forebulge domain. The deformation-controlled sediment dispersal pattern consists of a progressive growth of the shelf accompanied with a progressive shift of depocenters from the North East to the South West and a general progradation to the North West along the southern border. This progressive filling has led to the confinement of the Rharb paleo-valley across the continental shelf. The complete filling of the palaeo-valley was followed by the development of a more than 70-m thick prodeltaic lobe at the front of the Oued Sebou river mouth during the Holocene.     

A tree-ring based precipitation reconstruction for the Mohe region in the northern Greater Higgnan Mountains,China, since AD 1724

August–July precipitation has been reconstructed back to AD 1724 for the Mohe region in the northern Greater Higgnan Mountains, China, using Pinus sylvestris var. mongolica tree-ring width. The reconstruction explains 39% of the variance in the precipitation observed from AD 1960–2008. Some droughts noted in historical documents are precisely captured in our reconstruction. Wet periods occurred during the periods of AD 1734–1785, AD 1805–1830, AD 1863–1880, AD 1922–1961, and AD 1983–1998; while the periods of AD 1786–1804, AD 1831–1862, AD 1881–1921, and AD 1962–1982 were relatively dry. Power spectral and wavelet analyses demonstrated the existence of significant 24-yr, 12-yr, and 2-yr cycles of variability. The results of the spatial correlations suggest that our reconstruction contains climatic signals for the southern Stanovoy Range and the northern Greater Higgnan Mountains. The positive correlations between the new reconstructed precipitation series and two precipitation reconstructions indicate that our precipitation reconstruction captures broad-scale regional climatic variations. A comparison between the weakening tendency of summer monsoon and the dry period of our reconstruction reveals that the annual precipitation in the Mohe region is partly influenced by the East Asian Summer Monsoon.     

粤港澳大湾区水路客运网络特征

以粤港澳大湾区水路客运班线为数据来源,运用复杂网络分析方法,分析水路客运网络的基本特征,评估其小世界特性与无标度特征,分析各节点的重要性,测试其鲁棒性与脆弱性,结果发现：1）大湾区水路客运网络基本健全,节点之间能够自由流动,但网络的层级单一,可达性较低的节点占据多数;2）大湾区水路客运网络具有部分小世界网络特性和无标度特性,节点分布呈现马太效应;3）深圳蛇口港在复杂网络中的综合重要性最为突出,比较重要的节点还有香港中港码头、香港国际机场、珠海九州港、澳门外港;4）大湾区南部的水路客运网络相比北部发达,东部比西部发达,空间发展不均衡;5）大湾区水路客运网络具有鲁棒性,生存能力较强,但网络发育不够完善,稳定性较差,难以经受蓄意攻击。整体上,大湾区水路客运网络还有较大的优化提升空间,应加大核心节点保障能力,增强边缘节点的连通性,提升大湾区北部的水路客运能力。