The Maesan fan delta, Miocene Pohang Basin, SE Korea: architecture and depositional processes of a high-gradient fan-delta-fed slope system

The Maesan fan-delta-fed slope system in the Miocene Pohang Basin occurs between two Gilbert-type fan deltas. Detailed analysis of sedimentary facies and bed geometry reveals that the sequence is represented by 13 sedimentary facies. These facies can be organized into three facies associations, representing distinct depositional environments: alluvial fan (facies association I), steep-faced slope (facies association II), and basin plain (facies association III). Subaerial debris flows and dense, inertia-dominated currents were transformed into subaqueous sediment gravity flows in steep-faced slope environments. Further downslope, these flows were channelized and formed lobate conglomerate and sandstone bodies at the terminal edge of the channels (or chutes). Interchannel and interlobe areas were dominated by homogeneous mudstone and muddy sandstone, deposited by suspension settling of fine-grained materials. Part of the steep-faced slope deposits experienced large-scale slides and slumps. The chutes/channels, lobes and splays on the steep-faced slope of the Maesan system are similar to those in modern subaqueous coarse-grained fan-delta systems.     

德令哈盆地早侏罗世冲积扇—扇三角洲沉积体系及其马尔科夫链分析

德令哈盆地下侏罗统含煤磨拉石盆地组合是在以冲积扇—扇三角洲沉积体系为主的沉积环境下发育起来的。简要报道研究区冲积扇—扇三角洲体系沉积及其组合特征 ,在此基础上借助马尔科夫链建立冲积扇—扇三角洲体系沉积旋回的结构模式 ,并探讨该结构模式的地质意义。     

川西复理石区填图方法的新进展

四川区调队在近年的区调中,应用基本层序、层序地层、海底浊积扇等理论和方法,对川西松潘－甘孜造山带复理石区的填图方法进行了新的探索。本文对其进行了初步总结。     

辽中凹陷北部湖底扇沉积模式及地震响应特征

综合利用辽中凹陷钻井和地球物理资料进行井—震标定、地震地层学解释和地震相分析.在东营组二段(简称东二段)沉积时期,该区分布多个NE向古辽河水系发育的三角洲沉积体系,存在前缘相带砂体整体滑塌并近距离搬运而形成的湖底扇沉积.湖底扇具有期次多、数量大和横向展布范围广等特点,不同沉积亚相(内扇、中扇、外扇)具有敏感的地震响应特征.分析锦州20构造测井资料的岩—电组合特征,探讨湖底扇形成条件,建立湖底扇的沉积模式,识别湖底扇沉积各亚相的地震响应特征;基于井—震标定技术,利用地震相干体和地震属性方法,研究2期湖底扇沉积横向展布特征,精细刻画有良好油气发现的Ⅱ期湖底扇中扇亚相储层发育边界.结果表明:应用湖底扇沉积模式和地震响应特征,在辽中凹陷北部东二段发现多个湖底扇沉积体,是有利的岩性油气勘探目标,对渤海海域岩性油气藏勘探具有指导意义.     

Catchment lithology as a major control on alluvial megafan development,Kohrud Mountain range,central Iran

The relative importance of tectonics, climate, base level and source lithology as primary factors on alluvial‐fan evolution, fan morphology and sedimentary style remain in question. This study examines the role of catchment lithology on development and evolution of alluvial megafans (>30 km in length), along the flanks of the Kohrud Mountain range, NE Esfahan, central Iran. These fans toe out at axial basin river and playa‐fringe sediments towards the centre of basin and tectonics, climatic change and base‐level fluctuations, were consistent for their development. They formed in a tectonically active basin, under arid to semiarid climate and a long term (Plio‐Pleistocene to Recent) change from wetter to drier conditions. The key differences between two of these fans, Soh and Zefreh fans, along the west and south flanks of this mountain range, is that their catchments are underlain by dissimilar bedrock types. The source‐area lithologies of the Soh and Zefreh fans are in sedimentary and igneous terrains, respectively, and these fans developed their geometry mainly in response to different weathering intensities of their catchment bedrock lithologies. Fan surface mapping (based on 1/50000 topographic maps, satellite images, and fieldwork), reveals that the geomorphic evolution of these fans differs in that the relatively large‐scale incision and through trenching of the Soh fan is absent in the Zefreh fan. Whereas the limited sediment supply of the Soh fan has resulted in a deep incised channel, the Zefreh fan has remained aggradational with little or no trenching into proximal to medial fan surface due to its catchment bedrock geology, composed mainly by physically weathered volcaniclastic lithology and characterized by high sediment supply for delivery during episodic flash floods. Sediment supply, which is mainly a function of climate and source lithology, is a dominant driver behind the development of fan sequences in alluvial megafans. Copyright © 2012 John Wiley & Sons, Ltd.     

1∶25万玉门镇幅区调修测主要进展及成果

1∶25万玉门镇幅(K47C004001)区域地质调查项目的主要进展如下:敦煌岩群总体为一套孔兹岩系组合,时代厘定为古元古代,从中新解体出了一套浅变质火山岩组合和浅变质细碎屑岩及碳酸盐岩组合,获得了大量微古化石,分别厘定为长城纪铅炉子沟群和蓟县纪平头山组、野马街组。对区内韧性剪切带进行了详细剖析,创新了有限应变测量的技术方法,识别出了敦煌岩群的5次变形事件。通过对昌马洪积扇不同沉积物粒度的统计分析,识别出7次粒度变粗事件,结合大量ESR测年数据,揭示了沉积物粒度突变事件与高原隆升期的必然联系。查明了区内侵入岩的时空分布和演化序列,将侵入岩划分为同源、异源、构造混杂、变质混杂4种类型。     

准噶尔盆地南缘四棵树剖面八道湾组扇三角洲沉积特征

在野外露头观察与实测的基础上,运用沉积学与层序地层的相关理论,对准噶尔盆地南缘四棵树剖面八道湾组沉积特征进行了详细研究。该剖面八道湾组为扇三角洲沉积,扇三角洲平原与扇三角洲前缘亚相均比较发育。运用层序地层学中基准面变化的原理,将八道湾组划分为2个长期旋回,并细分为3个中期旋回以及若干短期旋回。总结了露头区八道湾组A/S比值与地层叠加样式之间的响应关系：低A/S比值条件下,易形成连通性好的厚层叠加砂体,沉积微相类型较单一;中A/S比值条件下,易形成单层厚度较薄的、似毯状的、垂向上紧凑叠加的多层状砂体;高A/S比值条件下,泥岩更为发育,而砂体多呈孤立状,呈现厚层泥与薄层砂的沉积特点。通过详细解剖露头剖面八道湾组的沉积特征,最终建立了该区八道湾组扇三角洲沉积模式,为准噶尔盆地南缘扇三角洲油气储层的研究提供了借鉴。     

基于多源多时相数据集的喀什市近70a城区空间扩展遥感研究

使用民国34年（1945年）1∶1×10⁴地形图、1968年CORONA影像及近期Landsat5和2015年GE影像数据,使用遥感技术以多元多时相遥感数据融合和GIS挖掘技术为支撑,采用等扇分析法和重心转移矩阵分析了喀什市70a城市空间形态整体扩展特征,各方向上的扩展速度、强度以及空间重心转移的方向、强度。结果表明：1945-2015年间喀什市空间形态经历了带状扩展向团状扩展的转变,城市整体空间扩展强度不断加剧,空间扩展速度呈先上升后下降再上升的趋势,空间重心向东南方向绿洲腹地转移1009m,侵占甚多绿洲耕地,城市空间扩展模式粗放,亟待调整。     

Emergent geomorphic–vegetation interactions on a subalpine alluvial fan

Following perturbation, an ecosystem (flora, fauna, soil) should evolve as a function of time at a rate conditioned by external variables (relief, climate, geology). More recently, biogeomorphologists have focused upon the notion of co‐development of geomorphic processes with ecosystems over very short through to very long (evolutionary) timescales. Alpine environments have been a particular focus of this co‐development. However, work in this field has tended to adopt a simplified view of the relationship between perturbation and succession, including: how the landform and ecosystem itself conditions the impact of a perturbation to create a complex spatial response impact; and how perturbations are not simply ecosystem destroyers but can be a significant source of ecosystem resources. What this means is that at the within landform scale, there may well be a complex and dynamic topographic and sedimentological template that co‐develops with soil, flora and fauna. Here, we present and test a conceptual model of this template for a subalpine alluvial fan. We combine detailed floristic inventory with soil inventory, determination of edaphic variables and analysis of historical aerial imagery. Spatial variation in the probability of perturbation of sites on the fan surface was associated with down fan variability in the across‐fan distribution of fan ages, fan surface channel characteristics and fan surface sedimentology. Floristic survey confirmed that these edaphic factors distinguished site floristic richness and plant communities up until the point that the soil–vegetation system was sufficiently developed to sustain plant communities regardless of edaphic conditions. Thus, the primary explanatory variable was the estimated age of each site, which could be tied back into perturbation history and its spatial expression due to the geometry of the fan: distinct plant communities were emergent both across fan and down fan, a distribution maintained by the way in which the fan dissipates potentially perturbing events. Copyright © 2015 John Wiley & Sons, Ltd.