Assessment of tafoni distribution and environmental factors on a sandstone djinn block above Petra,Jordan     

《Applied geography (Sevenoaks, England)》2013

Through the measurement of tafoni dimensions on an isolated, and unrecorded ‘djinn block’ in Petra's Ordovician Disi Sandstone, minimum surface recession were prevalent on eastern and western faces ranging from 10 to 127 mm/millennia. Moderate tafoni development was identified on northern aspects ranging from 105 to 110 mm/millennia. While on southern vertical faces, the greatest development ranged from 120 to 220 mm/millennia. Solar flux was correlated to the measured tafoni cell dimensions and revealed a minimal recession rate (and depth) of approximately 10–45 mm/millennia above which northern influences increased deterioration ‘moderately’ up to 110 mm/millennia, and southern influences had the greatest exacerbating effect with a maximum recessional rate of 220 mm/millennia – producing the greatest recession of nearly one inch (22 mm) each century. It is speculated that weathering accelerated on shaded (northern) faces through more frequent and longer spans of wetting and drying cycles, in addition to the effects of lichen and cyanobacteria overgrowth. While on regularly sunlit surfaces (southern), increased solar flux (up to ∼3000 MJ/m²/year) accelerated deterioration though more rapid, and extreme heating and cooling cycles. As rarely documented, tafoni on eastern faces were the smallest, and they were only slightly larger on western faces. Slightly increased heating from afternoon temperatures, in tandem with the incidence of frontal precipitation is attributed to the only slightly larger tafoni found on western faces (than on eastern aspects).  相似文献   

砂岩储层AVO特征影响因素的不确定性研究   总被引：3，自引：2，他引：1       下载免费PDF全文

何涛  史謌  邹长春  任科英  裴发根 《地球物理学报》2011,54(6):1584-1591

传统的地震AVO正演研究多采用参数固定的岩石物理模型,而实际地层属性参数在勘探范围内具有不确定性.本研究以目标地层岩芯样品的实验室测试数据为基础,通过样品孔隙度和干燥状态下纵、横波阻抗的高度线性关系对岩石物理模型进行了简化,并结合实验测量和测井解释建立了主要模型参数的概率密度函数.采用Monte-Carlo随机正演和G...  相似文献   

牛圈湖油田西山窑组水驱油效率影响因素研究     

吴彦君  孙卫  杨希濮  屈乐  QU Le 《云南地质》2011,30(2):242-245,237

物性较好且孔隙结构分选和连通性较好的储层,其驱油效率较高;在注水开发初期,提高注入压力和增加注入量,对驱油效率的影响较明显,当注入量超过3Pv之后,二者的增加对驱油效率的影响将明显减弱。  相似文献   

神木—双山地区太原组桥头砂岩沉积特征及演化     

宋雪娟  李壮福  黄金连 《中国煤炭地质》2011,(4):14-18

在对砂岩的岩石学、粒度分析、地球化学、沉积构造、垂向层序、测井曲线及沉积体系展布等资料分析的基础上,研究了鄂尔多斯盆地神木-双山地区太原组桥头砂岩沉积特征,探讨了砂体沉积演化过程,建立了桥头砂岩沉积模式。桥头砂岩形成于相对海平面下降时期的辫状河-浅水三角洲沉积体系,陆源碎屑物质被河流不断向南搬运充填入盆地中,形成辫状河、浅水三角洲、障壁砂坝-潟湖-潮坪、陆表浅海在空间上共存的岩相古地理格局。  相似文献   

Extensive carbonate cementation of fluvial sandstones: An integrated outcrop and petrographic analysis from the Upper Cretaceous, Book Cliffs, Utah   总被引：1，自引：0，他引：1  

Kevin G. Taylor  Philip G. Machent 《Marine and Petroleum Geology》2011,28(8):1461-1474

Extensive, large-scale pervasive cementation in the form of cement bodies within fluvial strata has rarely been documented although fluvial strata commonly act as important hydrocarbon reservoirs, as well as groundwater aquifers. Here, we present outcrop, petrographic and geochemical data for pervasive ferroan dolomite cement bodies up to 250 m in size from Upper Cretaceous Desert Member and Castlegate Sandstone fluvial strata exposed in the Book Cliffs in Utah. These cement bodies are present with coastal plain fluvial strata within both the Desert and Castlegate lowstand sandstones and are most abundant in the thin, distal fluvial strata. Cement bodies are almost entirely absent in updip, thicker, fluvial strata. Petrographic observations suggest a predominantly early diagenetic timing to the mildly ferroan dolomite, with a component of later burial origin. δ¹³C values for the cement (+4.8 to −5.7‰ V-PDB) suggest a marine-derived source for the earliest phase with a burial organic matter source for later cement. δ¹⁸O data (−6.3 to −11.8‰ V-PDB) suggest precipitation from freshwater dominated fluids. It is proposed here that dolomite was derived from leaching of detrital dolomite under lowstand coals and cementation took place in coastal aquifers experiencing mixed meteoric-marine fluids as a result of base-level fluctuations. This data presented here shows that large cement bodies can be an important component within fluvial sandstones with a potentially significant impact upon both reservoir quality and fluid flow within reservoirs, especially at the marine-non-marine interface.  相似文献   

层间氧化带砂岩型铀矿区域预测准则及其在新疆准噶尔盆地东部的运用   总被引：5，自引：1，他引：5  

韩德仁  林双幸 《铀矿地质》1995,11(3):129-139

在层间氧化带砂岩型铀矿找矿工作中，区域预测具有非常重要的作用。本文据作者的研究结合与乌兹别克斯坦共和国国家矿产资源委员会“红色丘陵地质联合企业”合作开展的《新疆准噶尔盆地东部１：２０００００地质预测》工作，提出了区域预测准则。旨在对我国中新生代盆地层间氧化带砂岩型铀矿找矿工作有所助益。  相似文献   

An excellent fossil wood cell texture with primary uranium minerals at a sandstone-hosted roll-type uranium deposit, NW China     

M. -Z. Min  X. -Z. Luo  S. -L. Mao  Z. -Q. Wang  R. C. Wang  L. -F. Qin  X. -L. Tan 《Ore Geology Reviews》2001,17(4)

A fossil wood cell texture with pitchblende and coffinite found at a sandstone-hosted roll-type uranium deposit, Xinjiang, NW China, is first reported here for the country. In the mineralized sandstone, detrital grains consisting of quartz, feldspar, rock fragments, carbonaceous trashes, mica and accessory minerals were deposited in early Turassic time and were cemented by clays and minor authigenic calcite and quartz. Pitchblende and minor coffinite are principal ore minerals at the deposit, and selectively replaced carbonized fossil wood remnants or filled fossil wood cells. An excellent fossil wood cell texture with primary uranium minerals formed. Replacement of organic debris by primary uranium minerals may be due to a local reducing environment resulting from the production of CH₄, H₂S or H₂SO₃ in its decomposition, and a biochemical reaction indicated by the common presence of framboidal pyrite.  相似文献   

Early Devonian (pre-Acadian) magnetization directions in Lower Old Red Sandstone of south Wales (UK)   总被引：1，自引：0，他引：1  

J. E. T. Channell  C. McCabe  N. H. Woodcock 《Geophysical Journal International》1992,108(3):883-894

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第四纪碎屑沉积层中的铀矿     

程国清 《铀矿地质》1990,6(2):72-76,120

本文阐述了某第四纪盆地108矿床的区域地质、矿床地质特征,提出了第四纪盆地铀成矿的四个方面的地质条件并对铀矿床的成因进行了探讨。  相似文献   

The weathering rates of some sandstone cliffs central Weald,England     

Allan Pentecost 《地球表面变化过程与地形》1991,16(1):83-91

Short-term (1-30 months) weathering rates were obtained for steep cliffs of Cretaceous Ardingly Sandstone in southern England, using a new photographic method. Mean rates for an exposed and a sheltered outcrop were 0.11 and 0.033 mm a^?1 respectively. Significant (p < 0.1) positive correlations were obtained with illumination and algal biomass and a significant negative correlation (p < 0.05) with slope angle. There was no correlation with grain size, porosity, or mean surface temperature. Highest weathering rates were observed on south- and west-facing exposed cliffs. The results are discussed with reference to algal growth, climate, and wind direction.  相似文献