广东雷州半岛晚渐新世—早更新世孢粉共存因子分析及古气候变化重建     

张宗言  刘祥  李响  柯学  张楗钰  徐亚东 《地学前缘》2022,29(2):303-316

广东省雷州半岛新生代钻孔ZKA01揭露的地层序列自下向上为渐新统涠洲组、中新统下洋组、角尾组、灯楼角组、上新统望楼港组、下更新统湛江组和中更新统北海组,涠洲组—望楼港组为滨浅海沉积,湛江组和北海组为陆相河湖相沉积。本文在ZKA01钻孔地层中自下向上88个层位中获取的29311粒孢粉化石的81个属中,选取了常见的种子植物花粉种属42个,通过共存因子分析法,定量重建了研究区晚渐新世—早更新世的古气候参数,划分出晚渐新世—早中新世(25~17 Ma)、中中新世(17~13.5 Ma)、晚中新世—上新世初期(13.5~4 Ma)和上新世—早更新世(4~1.5 Ma)4个气候演化阶段。孢粉共存因子定量法重建的研究区晚渐新世—早更新世4个阶段的古气候变化过程能较好地与全球气候变化的趋势相匹配,晚渐新世—早中新世温度降低的时间拐点大致可与Mi1a气候变冷事件相吻合。中中新世可以与中中新世气候适宜期(MMCO)相对应,表现为炎热潮湿的气候特征。中中新世晚期的气温是下降的,在一定程度上响应了Mi3中中新世气候变冷事件。  相似文献   

准噶尔盆地阜东斜坡区中上侏罗统储集层特征差异及控制因素分析   总被引：1，自引：0，他引：1  

于景维  叶勇  柳妮  朱永才  文华国 《地质学报》2018,92(5):1070-1080

准噶尔盆地是中国西部地区最重要的含油气盆地之一,阜东斜坡区中上侏罗统头屯河组和齐古组是近期勘探重点。根据野外露头、钻井岩芯和分析化验资料,详细分析头屯河组和齐古组储集层特征差异,包括储集层岩矿特征和物性特征差异。岩矿特征中重点对碎屑、填隙物以及孔隙类型和结构特征进行对比分析,物性特征中重点对储集层类型进行研究,发现齐古组储集砂层储集质量总体上要好于头屯河组。通过综合分析,认为阜东斜坡区中上侏罗统储集层特征差异主要受构造、沉积相、异常压力和成岩作用复合控制,构造演化的差异是导致头屯河组和齐古组储集层特征差异的最关键因素,头屯河组物性最好储集层的微相类型为水下分流河道,齐古组物性最好储集层的微相类型为分流河道,异常压力对原生孔隙保存以及黏土矿物发育位置起到重要影响,成岩作用对于重点层位储集层物性好坏起到决定性作用,其中凝灰质的蚀变序列对于后期油气开发有重要参考价值。  相似文献   

Petrogenesis and geochronology of Mishao peraluminous I-type granites,Shalair valley area,NE Iraq     

Imad Kadhim Abdulzahra  Ayten Hadi  Yoshihiro Asahara  Hossein Azizi  Koshi Yamamoto 《Chemie der Erde / Geochemistry》2018,78(2):215-227

The Shalair area, which is located in northeastern Iraq, is considered to be part of the northern Sanandaj-Sirjan Zone (SaSZ) and contains several granitoid bodies. One of these bodies, the Mishao porphyritic-granite (MG), was crystallized at 111.6?±?2.4 Ma, based on its zircon U-Pb age. Its geochemical characteristics suggest that the MG rocks are calc-alkaline, peraluminous, I-type granites with microgranular mafic enclaves. They are enriched in SiO₂, Na₂O, Al₂O₃ and Zr and depleted in MgO, Fe₂O₃, Nb and Ti; in contrast, the enclave sample records lower SiO₂ content and higher contents of MgO and Fe₂O₃. These rocks show an enrichment of LREE relative to HREE, and pronounced negative Eu anomalies implying feldspar fractionation. The isotopic and geochemical characteristics of the MG samples suggest that these rocks are evolved through fractional crystallization. In the La/Nb-Nb diagram and Sm/Nd ratios, the MG rocks and the enclave samples exhibit strong evidence for crustal contamination. The MG rocks record high initial ⁸⁷Sr/⁸⁶Sr (0.70625–0.70740) and low ¹⁴³Nd/¹⁴⁴Nd(i) (0.51235–0.51274) ratios. These Sr-Nd isotopic data, combined with the presence of high Th/U and Rb/Sr ratios and significant depletions of Nb, Ta and Ti, show a relation of these bodies to an active continental margin regime. Based on the age and geochemical data of the MG, this study presents new information about the occurrence of Middle Cretaceous magmatic activities, which are related to the active continental margins in the SaSZ that run parallel to the Zagros Fold-Thrust Belt.  相似文献   

Early–Middle Ordovician volcanism along the eastern margin of the Xing’an Massif,Northeast China: constraints on the suture location between the Xing’an and Songnen–Zhangguangcai Range massifs     

Yu Li  Feng Wang  Jie Tang  Chen-Yang Sun  Zi-Jin Wang 《International Geology Review》2018,60(16):2046-2062

We present new zircon U–Pb and Hf isotopic as well as whole-rock geochemical data for volcanic rocks from the eastern margin of the Xing’an Massif, Northeast China, in order to further our understanding of the suture location between the Xing’an and Songnen–Zhangguangcai Range massifs. Zircon secondary ion mass spectrometry U–Pb dating indicates that the volcanic rocks formed during the Early–Middle Ordovician (473–463 Ma). Compared with the coeval Moguqi basalts (rare earth element [REE] = 171–183 ppm; εHf_(t) = +0.3 to +2.7; T_DM1 = 1074–977 Ma), the Duobaoshan andesites exhibit lower overall REE abundances (109–131 ppm) with relatively high heavy REE contents, stronger high-field-strength element depletion, higher εHf_(t) values (+13.0 to +14.8), and much younger T_DM1 ages (559–484 Ma). This suggests that the primary magma for the andesites was generated by the partial melting of a relatively depleted mantle wedge that was metasomatized by subduction-related fluids. The primary magma for the basalts in the Moguqi area was probably derived from the partial melting of a relatively enriched lithospheric mantle that was also modified by fluids sourced from a subducted slab. These interpretations suggest that the andesites in Duobaoshan formed in a newly accreted island arc setting, whereas the coeval basalts in Moguqi formed along an active continental margin. We therefore attribute the Early–Middle Ordovician volcanism along the eastern margin of the Xing’an Massif to the northwestward subduction of the Nenjiang–Heihe oceanic plate beneath the Xing’an Massif. Furthermore, considering coeval igneous activity in the southern parts of the Xing’an Massif, we suggest that a magmatic arc existed along the margin of the Xing’an Massif in the early Palaeozoic (490–420 Ma). We conclude that the location of the suture between the Xing’an and Songnen–Zhangguangcai Range massifs runs from Airgin Sum, via south of Xilinhot, to Ulanhot, Moguqi, Nenjiang, and finally Heihe.  相似文献   

The Middle Pleistocene terraces of the central Waveney valley,Earsham, south Norfolk,UK     

Philippa Holmes  James Rose  Jonathan R. Lee  Rene Barendregt  Ian Candy  James B. Riding  Mark Lewis 《Proceedings of the Geologists' Association. Geologists' Association》2018,129(1):70-88

Although substantial work has been done on the pre-glacial terraces of East Anglia, very little systematic work has been done to understand the origin of river terraces in East Anglia that have formed since ice last covered the region. This paper records the results of studies of exposures and borehole records in ‘classical’ Quaternary terrace landforms that are considered to have formed since the Anglian (MIS 12) Glaciation, in the middle Waveney Valley. These features have been examined in terms of their morphological and sedimentological properties, in order to provide a detailed record of their form and composition, understand their processes of formation, and identify their stratigraphical status. The results show that the main body of the highest terrace (Homersfield Terrace, Terrace 3) is not composed of river sediments, but of shallow marine sediments, and is a remnant of early Middle Pleistocene Wroxham Crag. River sediments, in the form of Anglian age (MIS 12) glaciofluvial Aldeby Sands and Gravels also exist in the area as a channel fill, cut through the Wroxham Crag, and reflect outwash erosion and sedimentation from a relatively proximal ice margin to the west. The results mean that the interpretations previously presented for the terrace landforms of the middle Waveney valley are not applicable. The issue of why the terrace stratigraphy, hitherto identified in East Anglia cannot be related to that for the River Thames to the south and the rivers of Midland England to the west, still requires further research.  相似文献   

Fault zone characteristics,fracture systems and permeability implications of Middle Triassic Muschelkalk in Southwest Germany     

《Journal of Structural Geology》2015

Fault zone structure and lithology affect permeability of Triassic Muschelkalk limestone-marl-alternations in Southwest Germany, a region characterized by a complex tectonic history. Field studies of eight fault zones provide insights into fracture system parameters (orientation, density, aperture, connectivity, vertical extension) within fault zone units (fault core, damage zone). Results show decreasing fracture lengths with distances to the fault cores in well-developed damage zones. Fracture connectivity at fracture tips is enhanced in proximity to the slip surfaces, particularly caused by shorter fractures. Different mechanical properties of limestone and marl layers obviously affect fracture propagation and thus fracture system connectivity and permeability. Fracture apertures are largest parallel and subparallel to fault zones and prominent regional structures (e.g., Upper Rhine Graben) leading to enhanced fracture-induced permeabilities. Mineralized fractures and mineralizations in fault cores indicate past fluid flow. Permeability is increased by the development of hydraulically active pathways across several beds (non-stratabound fractures) to a higher degree than by the formation of fractures interconnected at fracture tips. We conclude that there is an increase of interconnected fractures and fracture densities in proximity to the fault cores. This is particularly clear in more homogenous rocks. The results help to better understand permeability in Muschelkalk rocks.  相似文献   

米仓山南缘中志留统罗惹坪组风暴岩沉积特征及其意义     

白志强  刘树根  宋金民  彭瀚霖  林彤  柳存喜 《沉积学报》2015,33(2):226-231

通过野外剖面实测和镜下薄片观察,笔者发现米仓山南缘志留系罗惹坪组顶部发育多套风暴沉积,典型的风暴沉积构造,包括侵蚀构造、砾屑结构、粒序层理等发育,岩性主要为灰绿色泥页岩、浅灰色或灰色微晶灰岩和生屑微晶灰岩。该区风暴岩发育3种风暴沉积序列,且具有一定的继承性,为远源型,沉积环境为浅水陆棚;风暴岩的发现解释了该区罗惹坪组生物灰岩透镜体的成因,为区域地层等时对比提供了新的标尺,对于研究区古地理、古气候以及古扬子海盆演化提供了依据。研究表明南江地区在志留系罗惹坪组晚期沉积时,曾处于风暴频发低纬度地区。  相似文献   

内蒙古查干敖包地区上石炭—下二叠统宝力高庙组特征及时代   总被引：1，自引：1，他引：0       下载免费PDF全文

武跃勇鞠文信  邵永旭姜海蛟 《中国地质》2015,(4):937-947

提要：笔者在查干敖包地区开展1∶5万区域地质调查工作时,发现本区出露的宝力高庙组层序齐全、植物化石丰富、划分标志明显,通过路线调查、剖面测量对其进行了重新划分,即据岩性组合、生物面貌等特征划分为4个岩性段,一段为河湖相灰色、灰绿色碎屑岩夹少量中性火山岩,在粉砂岩中采到了大量安格拉植物化石;二段为中偏碱性-酸性砖红色、紫色火山岩夹砂（砾）岩,其中粗面岩获得锆石U-Pb同位素年龄为(297.0±1.2) Ma;三段为灰色、灰紫色安山质火山岩夹碎屑;四段以灰白色流纹质火山岩为特征,夹砂岩、泥灰岩等,在砂岩中采到了大量安格拉植物群化石。据植物化石鉴定结果、同位素年龄资料将其形成时代确定为晚石炭—早二叠世。  相似文献   

植物胶冲洗液在东乌旗阿吉勒铅锌矿钻探施工中的应用          下载免费PDF全文

赵浩  何涛  李强  尹飞 《探矿工程》2015,42(8):35-38

内蒙古东乌旗阿吉勒铅锌矿区地层复杂,钻进过程中经常遇到多个构造破碎带,以凝灰岩和碳质板岩为主,蚀变发育,在泥质、硅质胶结段极易遇水膨胀、水化分散,造成坍塌、缩径等护壁难题。在采用多种冲洗液效果不理想的情况下,试验应用了植物胶低固相冲洗液,达到较好的防塌效果,且适应性强、粘度适中,形成的泥饼薄而致密且有韧性,成功地解决该矿区钻孔护壁难题。以ZK1507钻孔为例,阐明了所采用的冲洗液在水敏性地层取得明显的防塌效果。  相似文献   

Analysis of geological effects on methane adsorption capacity of continental shale: a case study of the Jurassic shale in the Tarim Basin,northwestern China     

Xiaoyue Gao  Luofu Liu  Fujie Jiang  Ying Wang  Fei Xiao  Zeying Ren  Zhengyang Xiao 《Geological Journal》2016,51(6):936-948

The Jurassic shale is an important source rock for the found gas reservoirs in the Tarim Basin, northwestern China, but has never been researched for shale gas potential. The geological effects on methane adsorption capacity for the gas shale have been investigated in this paper through the geochemical, mineralogical and adsorption analyses on samples from wells and sections. The methane adsorption capacity ranges from 0.58 to 16.57 cm³/g, and the total organic carbon (TOC) content is between 0.5 and 13.5 wt%. The organic maturity measured by T_max is between 410 °C (immature) and 499 °C (overmature). The methane adsorption capacity of the Jurassic continental shale in the Tarim Basin is affected by many geological factors, including the TOC content, organic matter maturity, mineral composition, surface area and pore size distribution. The TOC content is the most significant factor with a positive effect on the adsorption capacity of the Jurassic shale, and the influence varies piecewise according to the TOC content. The TOC content contributes much more to the methane adsorption capacity of organic‐rich shale samples (TOC content > 0.7 wt%) than to the organic‐lean samples (TOC content < 0.7 wt%). The mineral composition is a secondary factor, and the abundance of clay content has a positive effect on the methane adsorption capacity despite its relatively weaker adsorption ability compared to TOC. The pore size distribution has different effects on surface area and pore volume. Mesopores and micropores provide the major surface area and are mainly derived from TOC and illite, which has a positive influence on the adsorption capacity. Mesopores and macropores offer the major pore volume and are mainly formed by illite, which is the major contributor for pore volume rather than surface area. In addition, the TOC and illite contents of the Jurassic shale in the Tarim Basin are closely related to the origin, maturity and diagenesis evolution of the shale: (1) both TOC and illite content variations are related to the different provenances and depositional environments of shale; (2) the decrease of TOC content with increasing maturity is also partly attributed to hydrocarbon generation; and (3) the increase of illite content with increasing maturity is due to illitization in the diagenesis of shale. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献