Structural architecture of the Owen Conglomerate,West Coast Range,western Tasmania: field evidence for Late Cambrian extension.

The Owen Conglomerate comprises coarse-grained siliciclastics that were deposited in response to Late Cambrian extension. The identification of normal faults that host thickened accumulations of siliciclastics is used here to support interpretation of syn-fill extension. Local mapping and section construction have identified a series of north-trending, en échelon, segmented normal faults that exhibit changes in along-strike polarity. The Late Cambrian faults are adjacent to sedimentary packages that define half-graben geometries, with an unconformity that defines basal contacts with underlying Mt Read Volcanics and onlap geometries onto the opposing basin margin. Faults that were active during deposition of the Owen Conglomerate were subsequently reversed during D₁ Middle Devonian deformation, with reverse displacement controlling the development of inversion structures defined by north-trending fold structures. Pervasive northwest-trending D₂ deformation extensively overprints earlier deformation features, and has led to the spectacular development of type 1 interference patterns that largely control outcrop distributions along the West Coast Range. Field evidence is documented in support for a simple structural history that accounts for geometries associated with Late Cambrian extension, prior to Middle Devonian inversion (D₁) and subsequent shortening (D₂).     

埕南断裂带埕913砾岩体成藏地质条件及勘探开发实践

从圈闭特征、生油条件、盖层条件和砾岩体的储集条件等方面对济阳拗陷埕913区块进行了地质研究;细分了沉积微相,对砂砾岩扇体进行了精细描述,摸索出储层压裂改造方案,总结出一套砾岩复杂岩性油藏的研究思路和技术方法。     

甘肃平凉“崆峒山砾岩”地层时代的商榷

出露于甘肃省平凉市崆峒山国家地质公园的＂崆峒山砾岩＂岩性特殊,厚度巨大。但是其地层时代的归属问题60多年来一直存在着各种不同的认识。作者根据野外观察,结合区域地质构造研究后初步认为,＂崆峒山砾岩＂可与陕西省千阳县出露的芬芳河组对比,两者是同一套地层,时代应属晚侏罗世。并进一步推测＂崆峒山砾岩＂和鄂尔多斯盆地内部的安定组可能是同期异相沉积,前者是山麓洪积扇堆积,后者是河流—湖泊相沉积。     

甘肃玉门5.9级地震前周至数字化综合观测井的异常特征

2002年12月14日,甘肃玉门发生5．9级地震,震前,距离震中1000km的周至地震台地下水数字化综合观测井的地热、水位、流量三个测项都出现了明显的短临异常显示。本文介绍了震前周至井出现的短临异常变化。与该台历史手工观测结果对比,数字化观测更有利于捕捉短临前兆信息及其变化的完整过程。     

甘肃玉门地区第四纪晚期构造阶地的红外释光测年

光释光（ＯＳＬ）测年是近几年从热释光（ＴＬ）测年基础工起来的测定第四纪沉积物年龄的一种新技术，其原理与ＴＬ测年类似。不同的是：ＯＳＬ是单色光束激发品体中储存的电离辐射能使其以光的形式释放出来。当用近红外线束作为激光光源时称之为红外释光测年。与ＴＬ测年相比，ＩＳＬ测年可以不考虑残留的ＯＳＬ信号，而且测量具有简便，迅速且准确等优点。本文用细颗粒红外释放技术对玉门地区的构造阶地进行了年龄测定，初步结果表     

环境磁学反映的藏南沉错地区1300年来冷暖变化

塔里木西缘帕米尔-西昆仑山北麓和西南天山南麓前陆盆地中巨厚的晚新生代磨拉石建造在岩石地层上包括阿图什组、西域组、乌苏组和戈壁组.通过对这套磨拉石建造及其中生长地层和生长不整合的野外观测,结合磁性地层年代学,初步研究了西域砾岩(即西域组)和西域运动的起始年代以及西域运动可能的演化阶段,得到如下初步认识:1)研究区西域砾岩开始沉积于3.5～4 6 Ma B.P.之前,其底界具有穿时性,其年代从山体向前陆盆地一般逐渐变新;2)在上述前陆盆地分布着4～6排由晚新生代磨拉石建造组成的逆断层-褶皱带.各排褶皱带均发育有生长地层及生长不整合,生长地层的开始沉积指示了该排褶皱和相应生长不整合的开始形成.从最靠山体一排褶皱带生长地层开始沉积的年代,初步判定西域运动的起始年代在西昆仑山叶城附近约为3.6 Ma B.P.,在西南天山喀什附近显然早于2.4 Ma B P.此后该运动可能经历了4～6个活动阶段,每一阶段又由若干个相对活跃期和相对稳定期组成.它们可通过各排褶皱带内生长地层的产状、组成和年代测定来确定.本文还探讨了生长地层和生长不整合形成过程中构造变形与侵蚀-剥蚀和沉积作用间的相互关系.     

2002年12月14日甘肃省玉门市5.9级地震概述

2002年12月14日，甘肃省玉门市发生5．9级地震，这是继2001年7月11日肃南5．3级地震后，在祁连山西段发生的又一次破坏性地震。极震区烈度为Ⅶ度，地震造成灾害损失达7000万人民币。文章对该震的基本参数、震源机制、地震序列、地震背景、震害损失评估及地震应急等作了概述。     

The Age and Character of the Yu''erhong Flora from Yumen, Gansu

From a fresh field investigation, it has been ascertained that the Late Palaeozoic Yu'erhong (Yuernhung) flora from Yu'erhong, Yumen, Gansu, northwestern China, studied by Bohlin in 1971 includes plants from the Westphalian Yangfukou Formation and the Stephanian to Sakmarian Taiyuan Formation. The Yu'erhong flora from the Yanghukou Formation is dominated by Euramerican elements with a few elements of the Cathaysian flora. No Angarian elements have be found in this section for lack of Late Permian strata. The specimens studied by Bohlin might possibly come from the upper part of the Upper Permian at tne southeastern corner . of the Yu'erhong basin. Those fossils from different horizons and localities might be mixed with each other during collection ;so they fail to reflect the exact horizon of certain plant fossils.     

吉林省珲春市黄松甸子砾岩型金矿床地质特征

黄松甸子砾岩型金矿床位于中新生代滨太平洋活动带，长白－春化裂谷的北端春化盆地内。矿体赋存于第三纪冲洪积层底部粗碎屑沉积中，为一河流冲积扇沉积矿床。成矿物质来原为中性－中酸性岩类及赋存于其中的热液脉金矿化体。重砂矿物除自然金外还见有３０余种其它矿物，并伴生可供综合利用的有益矿物钛铁矿和锆石。     

Volcanic facies architecture of an intra-arc strike-slip basin, Santa Rita Mountains, Southern Arizona

The three-dimensional arrangement of volcanic deposits in strike-slip basins is not only the product of volcanic processes, but also of tectonic processes. We use a strike-slip basin within the Jurassic arc of southern Arizona (Santa Rita Glance Conglomerate) to construct a facies model for a strike-slip basin dominated by volcanism. This model is applicable to releasing-bend strike-slip basins, bounded on one side by a curved and dipping strike-slip fault, and on the other by curved normal faults. Numerous, very deep unconformities are formed during localized uplift in the basin as it passes through smaller restraining bends along the strike-slip fault. In our facies model, the basin fill thins and volcanism decreases markedly away from the master strike-slip fault (“deep” end), where subsidence is greatest, toward the basin-bounding normal faults (“shallow” end). Talus cone-alluvial fan deposits are largely restricted to the master fault-proximal (deep) end of the basin. Volcanic centers are sited along the master fault and along splays of it within the master fault-proximal (deep) end of the basin. To a lesser degree, volcanic centers also form along the curved faults that form structural highs between sub-basins and those that bound the distal ends of the basin. Abundant volcanism along the master fault and its splays kept the deep (master fault-proximal) end of the basin overfilled, so that it could not provide accommodation for reworked tuffs and extrabasinally-sourced ignimbrites that dominate the shallow (underfilled) end of the basin. This pattern of basin fill contrasts markedly with that of nonvolcanic strike-slip basins on transform margins, where clastic sedimentation commonly cannot keep pace with subsidence in the master fault-proximal end. Volcanic and subvolcanic rocks in the strike-slip basin largely record polygenetic (explosive and effusive) small-volume eruptions from many vents in the complexly faulted basin, referred to here as multi-vent complexes. Multi-vent complexes like these reflect proximity to a continuously active fault zone, where numerous strands of the fault frequently plumb small batches of magma to the surface. Releasing-bend extension promotes small, multivent styles of volcanism in preference to caldera collapse, which is more likely to form at releasing step-overs along a strike-slip fault. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.