Early Jurassic palaeoenvironments in the Surat Basin,Australia – marine incursion into eastern Gondwana     

Andrew D. La Croix  Jianhua He  Valeria Bianchi  Jiahao Wang  Sebastian Gonzalez  Jim R. Undershultz 《Sedimentology》2020,67(1):457-485

Interpretations of palaeodepositional environments are important for reconstructing Earth history. Only a few maps showing the Jurassic depositional environments in eastern Australia currently exist. Consequently, a detailed understanding of the setting of Australia in Gondwana is lacking. Core, wireline logs, two-dimensional and three-dimensional seismic from the Precipice Sandstone and Evergreen Formation in the Surat Basin have been used to construct maps showing the evolution of depositional environments through the Early Jurassic. The results indicate the succession consists of three third-order sequences (Sequence 1 to Sequence 3) that were controlled by eustatic sea level. The lowstand systems tract in Sequence 1 comprises braidplain deposits, confined to a fairway that parallels the basin centre. The strata were initially deposited in two sub-basins, with rivers flowing in different orientations in each sub-basin. The transgressive systems tract of Sequence 1 to lowstand systems tract of Sequence 3 is dominated by fluvio–deltaic systems infilling a single merged basin centre. Finally, the transgressive and highstand systems tracts of Sequence 3 show nearshore environments depositing sediment into a shallow marine basin. In the youngest part of this interval, ironstone shoals are the most conspicuous facies, the thickness and number of which increase towards the north and east. This study interprets a corridor to the open ocean through the Clarence–Moreton Basin, or the Carpentaria and Papuan basins, evidence of which has been eroded. These results challenge a commonly held view that eastern Australia was not influenced by eustasy, and propose a more dynamic palaeogeographic setting comprising a mixture of fluvial, deltaic and shallow marine sedimentary environments. This work can be used to unravel the stratigraphic relationships between Mesozoic eastern Australian basins, or in other basins globally as an analogue for understanding the complex interplay of paralic depositional systems in data poor areas.  相似文献   

A palaeomagnetic study of Devonian sandstone from Central Spitsbergen     

M. Jele&#;ska  M. Lewandowski 《Geophysical Journal International》1986,87(2):617-632

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Provenance, diagenesis, tectonic setting and geochemistry of Tawil Sandstone (Lower Devonian) in Central Saudi Arabia     

Omar A. Al-Harbi  M. Mujtaba Khan 《Journal of Asian Earth Sciences》2008,33(3-4):278-287

The Tawil Sandstone (Lower Devonian) in Central Saudi Arabia overlies the Sharwara Member of the Tayyarat Formation (Silurian) and succeeded conformly by the Shaiba Member of the Jauf Formation. Petrographical data reveal that the Tawil Sandstone comprises 96% quartz, 3% feldspar, and 1% rock fragments and all samples are classified as quartz arenites. The presence of well sorted, altered to fresh feldspar, and discriminate function analysis suggests that the sediments have been subjected to substartial reworking resulting in a high level of maturity. Modal analysis data (Q–F–L) suggest a stable cratonic provenance for the sediments and accumulation in a passive margin basin is indicated (binary plot of SiO₂ vs K₂O/Na₂O). Diagenetic features include dissolution of feldspar and rock fragments, compaction, reduction of the existing pore space through rearrangements, and rotation and fragmentation of grains resulting in dissolution of quartz grains and cementation.  相似文献   

新疆皮山杜瓦普司格组晚二叠世孢粉的发现   总被引：1，自引：1，他引：1  

朱怀诚 《地层学杂志》1997,21(3):219-223,T001

新疆皮山杜瓦剖面普司格组中、上部含丰富的孢子花粉化石，并以双气囊花粉数量占优势为特征。Ｌｕｅｃｋｉｓｐｏｒｉｔｅｓｖｉｒｋｋｉａｅ、Ｔａｅｎｉａｅｓｐｏｒｉｔｅｓｓｐｐ．和Ｇａｒｄｅｎａｓｐｏｒｉｔｅｓｘｉｎｊｉａｎｇｅｎｓｉｓ等国内外晚二叠世典型分子在该组合内出现，表明普司格组的时代并非仅限于以往所普遍认为的早二叠世，亦应包括部分晚二叠世。结合对普司格组上覆和下伏地层的古生物群分析，普司格组的时代为早二叠世中期至晚二叠世中期。  相似文献   

Classification of rock weathering at writing-on-stone Provincial Park,Alberta, Canada: A study in applied geomorphology     

Ian A. Campbell 《地球表面变化过程与地形》1991,16(8):701-711

At Writing-On-Stone Provincial Park in southern Alberta, Canada, weathering is causing deterioration and loss of archaeologically important Indian rock art. A procedure devised for the use of park personnel identified four classes of weathering ranging from largely unweathered rock to severely weathered. The technique employed simple visual, qualitative assessment and photo interpretation of 50 sample sections of sandstone cliff face covering a total area of 354 m². Schmidt hammer tests indicated large variations in rock strength and provided a numerical basis for the visual assessment. About 43 per cent of the cliffs are severely to completely weathered, 41 per cent show moderate weathering.  相似文献   

Remote detection of fluid-related diagenetic mineralogical variations in the Wingate Sandstone at different spatial and spectral resolutions     

《International Journal of Applied Earth Observation and Geoinformation》2016

Well-exposed eolian units of the Jurassic system on the Colorado Plateau including the Wingate Sandstone, show prominent color variations throughout southeastern Utah due to diagenetic changes that include precipitation and/or removal of iron oxide, clay, and carbonate cement. Spatially variable characteristic diagenetic changes suggest fluid-rock interactions through the sandstone. Distinctive spectral signatures of diagenetic minerals can be used to map diagenetic mineral variability and possibly fluid-flow pathways. The main objective of this work was to identify characteristic diagenetic minerals, and map their spatial variability from regional to outcrop scale in Wingate Sandstone exposures of Lisbon Valley, Utah. Laboratory reflectance spectroscopy analysis of the samples facilitated identification of diagnostic spectral characteristics of the common diagenetic minerals and their relative abundances between altered and unaltered Wingate Sandstone. Comparison of reflectance spectroscopy with satellite, airborne, and ground-based imaging spectroscopy data provided a method for mapping and evaluating spatial variations of diagenetic minerals. The Feature-oriented Principal Component Selection method was used on Advanced Spaceborne Thermal Emission and Reflection Radiometer data so as to map common mineral groups throughout the broader Wingate Sandstone exposure in the area. The Minimum Noise Fraction and Spectral Angle Mapper methods were applied on airborne HyMap and ground-based hyperspectral imaging data to identify and map mineralogical changes. The satellite and airborne data showed that out of 25.55 km² total exposure of Wingate Sandstone in Lisbon Valley, unaltered sandstone cover 12.55 km², and altered sandstone cover 8.90 km² in the northwest flank and 5.09 km² in the southern flank of the anticline. The ground-based hyperspectral data demonstrated the ability to identify and map mineral assemblages with two-dimensional lateral continuity on near-vertical rock faces. The results showed that 39.71% of the scanned outcrop is bleached and 20.60% is unbleached while 6.33% remain unclassified, and 33.36% is masked-out as vegetation. The bleached and unbleached areas are alternating throughout the vertical face of the outcrop. The relative hematite abundance observed in the unbleached areas are somewhat symmetrical. This indicates fairly similar reaction intensities along the upper and lower reaction fronts observed in the vertical section. The distribution geometry and relative abundances of diagenetic minerals not only suggest multiple paths of fluid-flow in Wingate Sandstone but also provides some insight about relative direction of past fluid-flow.  相似文献   

鄂尔多斯盆地北部砂岩铀矿床粘土矿物与氧化带成因关系研究          下载免费PDF全文

李华明 李 玲彭云彪  剡鹏兵易 超 《地质科学》2021,56(1):303-320

对鄂尔多斯盆地北部铀成矿带产铀层位中侏罗统直罗组砂岩进行系统采样和分析,以探讨砂岩中粘土矿物特征与氧化带成因之间的关系。采用X?射线粉晶衍射、电子探针分析等现代分析手段,测定粘土矿物相对含量、微观形貌特征。结果表明:研究区古层间氧化的演变序列为砂体原始灰色→古氧化作用(红色或黄色)→碳酸盐化(残留了部分红色)→后期还原作用(绿色),对应的岩石蚀变期次为早期氧化酸性蚀变→氧化期后弱碱性蚀变→晚期还原弱碱性蚀变;早期氧化砂岩在还原性气体作用下,Fe³⁺还原转化为Fe²⁺,高岭石在有Fe2+存在的条件下会向绿泥石转化,这一反应在碎屑颗粒表面,形成许多极细小的针叶状绿泥石,从而使古层间氧化亚带呈现特征的绿色。  相似文献   

云南江城岩脚铅锌矿控矿因素     

董诗位  田宗春  刘相琴 《云南地质》2010,29(4):424-428

矿床位于江城中新生代拗陷盆地,铅锌矿赋存于F1断层两侧景星组下段一、三、五岩段中,分砂岩型和角砾岩型。存在三种矿物组合,受盆地演化、构造、岩性控制明显。  相似文献   

Diagenetic alterations related to marine transgression and regression in fluvial and shallow marine sandstones of the Triassic Buntsandstein and Keuper sequence,the Paris Basin,France   总被引：1，自引：0，他引：1  

M.A.K. El-ghali  S. Morad  H. Mansurbeg  Miguel A. Caja  M. Sirat  N. Ogle 《Marine and Petroleum Geology》2009

The distribution of diagenetic alterations in Triassic fluvio-deltaic, quartzarenitic to sublitharenitic, lowstand systems tract (LST) sandstones of the Grès á Voltzia Formation, anastomosing fluvial, quartzarenitic transgressive systems tract (TST) sandstones of the Grès á Roseaux Formation, and shallow marine, quartzarenitic to sublitharenitic, TST sandstones of the Grès Coquiller Formation, the Paris Basin (France), can be linked to transgression and regression events, and thus to the sequence stratigraphic context. Near-surface eogenetic alterations, which display a fairly systematic link to the depositional facies and sequence stratigraphic framework, include: (i) cementation by meteoric water calcite (δ¹⁸O=−8.9‰ and δ¹³C=−9.1‰) in the fluvio-deltaic, LST sandstones, (ii) cementation by mixed marine–meteoric calcite (δ¹⁸O=−5.3‰ to −2.6‰ and δ¹³C=−3.9‰ to −1.3‰) and dolomite (δ¹⁸O=−4.6‰ to −2.6‰ and δ¹³C=−2.9‰ to −2.3‰) in the foreshore, TST sandstones and below parasequence boundaries (PB), and transgressive surface (TS), and in the shoreface, TST sandstones below maximum flooding surfaces (MFS), being facilitated by the presence of carbonate bioclasts, (iii) dissolution of detrital silicates and precipitation of K-feldspar overgrowths and kaolinite, particularly in the fluvio-deltaic, LST sandstones owing to effective meteoric water circulation, and (vi) formation of autochthonous glauconite, which is increases in abundance towards the top of the fluvio-deltaic, LST sandstones, and along TS, and in the shoreface, TST sandstones, by alteration of micas owing to the flux of seawaters into the sandstones during transgression, whereas parautochthonous glauconite is restricted to the TS sandstones owing to marine reworking. Mesogenetic alterations, which include cementation by quartz overgrowths and illite, display fairly systematic link to fluvio-deltaic, LST sandstones. This study has revealed that linking of diagenesis to transgression and regression events enables a better understanding of the parameters that control the spatial and temporal distribution of diagenetic alterations in sandstones and of their impact on reservoir quality evolution.  相似文献   

512可地浸砂岩型铀矿床地质特征和远景评价     

程明高  简晓飞 《铀矿地质》1995,11(1):11-18

本文介绍了５１２矿床区域地质背景、矿床基本特征、近期勘探成果、地浸效果和矿区远景评价。该矿床的成矿条件有利，属层间氧化带砂岩型，有可能发展成可地浸的、低品位的万吨级矿床，其矿田远景将更为可观。  相似文献