Occurrence of cyclic palustrine and calcrete deposits within the lower Pliocene Hagul formation, East Cairo district, Egypt     

Fikry I. Khalaf  Ahmad S. Gaber 《Journal of African Earth Sciences》2008,51(5):298-312

A depositional model of the lower Pliocene Hagul formation, which is exposed in the East Cairo district (Egypt), is proposed with more than 10 depositional cycles recognized. Field occurrence, detailed petrographic investigation and geochemical analysis revealed that the sediments within each cycle are the result of three sequential sedimentological processes: (1) alluvial sedimentation, (2) calcretization, and (3) precipitation of palustrine carbonate. It was concluded that Hagul formation has been deposited within the distal part of an alluvial plain during three successive climatic conditions: a humid climate during which alluvial sediments were deposited, a semi-arid climate with episodic precipitation which was favorable for pedogenic calcrete development, and a sub-humid climate during which groundwater level was gradually elevated and groundwater calcrete accumulated. Rising groundwater level continued until shallow wetlands covered the area and palustrine limestone was precipitated. Variations in the thickness and the nature of the host sediment, calcrete and palustrine limestone cycle suggest that each of the sedimentation processes varied from cycle to cycle.  相似文献   

莱州湾南岸HLL01孔磁性地层定年   总被引：1，自引：1，他引：0  

姜兴钰  易亮  田立柱  施佩歆  陈永胜  王宏  王福  李建芬  商志文 《地质通报》2016,35(10):1669-1678

亚洲大陆边缘海在区域能量与物质交换及气候与环境演化中扮演了关键的角色,而磁性地层学方法是建立年代框架的有效手段。过去对于渤海地区的长钻孔研究主要集中在渤海湾及其北岸,莱州湾地区尚未有较长的公开发表的钻孔。利用莱州湾南岸新近钻取的孔深452m的HLL01孔沉积物样品,进行了详细的磁性地层学研究。结果表明,1HLL01孔共有272块样品用于建立钻孔的磁性地层序列,可识别出10个正极性时段和9个负极性时段;2通过与国际标准极性年表的对比,确定HLL01孔记录了正极性亚时C3An.2n~C1n(布容正极性时)的沉积,钻孔底部位于C3An.2n,年龄约为6.6Ma;3钻孔内中、上新世的界线位于340m,上新世与更新世的界线位于140m;4通过与渤海湾及其北岸的研究成果对比,发现莱州湾自晚中新世以来的环境演化过程与之存在一定的差异性。  相似文献   

Composition of Pliocene to Quaternary mixed terrigenous and calcareous sandy beds in contourite drift deposits at ODP Site 1119 off New Zealand: Insights into sandy drift development and drift petroleum reservoir characterization     

《Marine and Petroleum Geology》2016

ODP (Ocean Drilling Program) Site 1119 was drilled in drift successions deposited by northward flowing currents on the Canterbury slope, South Island, New Zealand. Pliocene (∼3.9 Ma) to Pleistocene drift accumulation was concomitant with tectonic uplift and sediment supply from the Alpine Fault plate boundary to the west, glacial development and eustatic sealevel change that created cyclicity in sandy input. Sand detrital and biogenic modes of very fine and fine sand fractions from 24 unconsolidated core samples (44 thin sections) were determined. Fine sand fractions contain an average of 52% bioclastic debris, with bioclasts making up 23% of the very fine sand fraction. Foraminifers are the dominant bioclasts, with pelagic more common than benthic varieties. The average proportions of monocrystalline quartz, plagioclase and potassium feldspar are similar in both size fractions (average QmKP of ∼25:12:63). In contrast, the very fine sand fractions have, on average, higher lithic (QFL%L of 16 vs. 3%), mica (Totalgrain%M of 10 vs. 6%), and dense mineral (Totalgrain%D of 8 vs. 5%) content as compared with the fine sand fractions. Younger clinoform drape (Unit I) and older mounded drift (Unit II) seismic facies showed no distinct detrital compositional differences in their sand fractions, though bioclast content ranges higher in the fine sand fraction of Unit II. Albite feldspar, metamorphic rock fragment, and chlorite components in the sand are consistent with a schist provenance. Other components such as biotite, plagioclase, and K-feldspar require a contribution from metasedimentary and volcanic rocks. Thus there is some along-slope mixing during sediment transport by south-to-north flowing currents. Cemented microporous sandstone at the base of the section provides some insight into contourite burial diagenesis. This work provides a better understanding of the compositional variability of sand components of drift successions which are potential hydrocarbon reservoirs elsewhere.  相似文献   

元谋盆地新第三纪地层兼论“甘棠组”     

宗冠福 《地层学杂志》1995,19(3):237-240,F003

元谋盆地南部的甘棠村西剖面和沙沟村西剖面的岩性岩相及其所含生物化石性质,应属同时同相的地质体,沙沟组已具“甘棠组”的内涵,后者应予废除。北部的小河组与沙沟组,不仅是截然不同性质的两个地质体,其中含有的生物化石也不同,小河组的层位低于沙沟组,故把小河地区合古猿化石层（小河组）划归沙沟组不妥。  相似文献   

⁴⁰Ar-³⁹Ar Spectra of Alunite from Phreatic Craters in the Muine Volcano, Hokkaido, Japan     

Yasushi Watanabe 《Resource Geology》2003,53(3):221-226

Abstract. ⁴⁰Ar-³⁹Ar analyses of two alunite samples from phreatic craters in the Pliocene Muine volcano in southwest Hokkaido, Japan, were carried out. The alunite with 17.4 permil δ³⁴S_{V_CDT} value in hydrothermal breccia from the Nagaoyama crater and that with 14.3 permil δ³⁴S_{V_CDT} value in silicified andesite from the Konuma crater give total fusion ages of 1.40 ± 0.04 Ma (la uncertainty) and 1.24 ± 0.08 Ma, respectively. However, the spectra of these samples indicate they have been effected by thermal overprinting and/or the existence of excess argon. These preliminary ⁴⁰Ar-³⁹A analyses suggest that the alunite underwent multiple hydrothermal activity by magmatic gas and vapor subsequent to the main hydrothermal activity.  相似文献   

北部湾R1钻孔岩心上新世以来的沉积环境演变史研究   总被引：2，自引：0，他引：2  

苍树溪  陈丽蓉 《海洋地质与第四纪地质》1992,12(4):53-58

本文综述北部湾东北部R_1孔岩心记录。R_1孔岩心长度100m,水深42m。在粒度分析、矿物分析及微体古生物分析的基础上,认为该区在上新世时,为浅海相沉积,更新世则以陆相为主,仅在晚更新世时出现两个滨海相沉积层,全新世为浅海相沉积。  相似文献   

关中盆地上新世地层形成时代、层序划分及沉积相特征研究          下载免费PDF全文

谢青  曾忠诚  张若愚  王天毅 《地质找矿论丛》2018,33(3):434-440

关中盆地位于华北板块西南缘,为一新生代断陷盆地,具典型地堑形态,沉积巨厚的新生代地层。针对盆地新近纪上新世地层形成时代有争议、地层层序划分不明确、沉积相界定较笼统等问题,利用钻测井资料及野外调研,结合前人研究成果,对盆地新生代地层进行了重新划分,明确了上新世各地层形成时代及其地层层序划分和沉积相类型。研究结果表明,上新统可划分为蓝田组(11Ma—7 Ma)、灞河组(7.3 Ma—2.6 Ma)、张家坡组(3.4 Ma—2.6 Ma);新生代层序地层可划分为古近系构造层序、中新统构造层序、上新统构造层序和第四系构造层序等4个一级层序,存在6个构造层序界面。蓝田组以"三趾马红黏土"的风成沉积为特征。灞河组沉积时期,关中盆地的西安凹陷为一套冲(洪)积相、河流、三角洲相沉积,固市凹陷为一套冲(洪)积、河流、三角洲及滨浅湖相沉积;盆地边部开始出现小范围的风成黏土沉积。张家坡组以河湖相沉积为主,沉积中心向南移;盆地南北两侧或边部为冲(洪)积扇相、河流相及三角洲相沉积,边部也有小范围的风成黏土沉积。  相似文献   

Latest Neogene Paleoclimate Variation in Yunnan,Southwest China,Revealed by Fossil Leaf Physiognomy     

DAI Jing  CHEN Weizhao  HUANG Liang  ZHANG Yi’nan 《《地质学报》英文版》2023,97(4):1268-1281

Yunnan Province, located in the southeastern margin of the Tibetan Plateau, can provide important information on how climate change was influenced by global cooling. However, its variation patterns in temperature and precipitation during the latest Neogene are not well-understood. Based on the 357 specimens assigned to 31 morphotypes of plant fossils from the upper Pliocene Ciying Formation in Yiliang County, Yunnan Province, Southwest China, paleoclimate was estimated by Leaf Margin Analysis an...  相似文献   

塔里木盆地西部鸟山-古董山地区断裂构造分析          下载免费PDF全文

杨海军  李曰俊  曾昌民  冯晓军  陈才  张亮  文磊  张强  梁华  姜红  贾铁干 《地质科学》2015,(4):1023-1043

鸟山-古董山地区位于塔里木盆地西部, 巴楚隆起与麦盖提斜坡之间, 鸟山、玛南、玛扎塔格、古董山和罗斯塔格构造带在此交汇, 附近还发育与之密切相关的沙陇断裂, 十分引人注目。鸟山-古董山地区的主干断裂形成于晚白垩世, 包括鸟山、罗斯塔格和玛扎塔格晚白垩世冲断构造带和玛南晚白垩世走滑断裂带, 玛南断裂是玛扎塔格构造带与鸟山和罗斯塔格构造带之间的调节断层。该期构造变形受控于南羌塘和拉萨地块与亚洲大陆之间的碰撞造山作用。鸟山-古董山地区的断裂构造于中新世末基本定型。因帕米尔突刺楔入于塔里木和卡拉库姆之间, 在塔西南地区形成一系列走滑断裂, 包括玛扎塔格-罗斯塔格中新世末走滑断裂, 古董山断裂是其派生断层。晚白垩世是研究区构造和圈闭的关键形成期, 上新世晚期-全新世早期以古近系底部膏盐层为主滑脱面的滑脱-冲断构造保护早期形成的圈闭和油气藏。鸟山和玛扎塔格构造带是研究区最有利的油气勘探区带, 玛南构造带是重要的油气运移通道。  相似文献   

Paleoenvironmental evolution of the Pliocene Villarroya Lake, northern Spain, from stable isotopes and trace-element geochemistry of ostracods and molluscs     

P. Anadón  R. Utrilla  A. Vázquez  M. Martín-Rubio  J. Rodriguez-Lázaro  F. Robles 《Journal of Paleolimnology》2008,39(3):399-419

Stable isotopes and trace-element content of calcite ostracod valves and aragonite mollusc shells from the Pliocene lacustrine succession of Villarroya allow depicting the geochemical record of environmental changes and to compare our data to the paleoenvironmental reconstruction obtained from other proxies. The lower sequences (A and B) are characterized by relatively high isotopic and Me/Ca values in the biogenic carbonates. The recorded large variations of δ¹⁸O in these carbonates mainly reflect variations in the δ¹⁸O_w due to precipitation–evaporation processes and, to a lesser extent, variations in temperature of calcification. The δ¹³C data inform about changes in DIC although they are probably biased by the vital effects of the studied taxa. Minor and trace element contents in ostracod (Mg/Ca, Sr/Ca) and mollusc shells (Sr/Ca) are mainly linked to the Me/Ca of the lake water (Me/Ca_w), and to a lesser extent to temperature and to uptake kinetic effects. Several possible mechanisms may make the Me/Ca_w to vary: long periods of Ca-carbonate (calcite, aragonite) deposition after charophyte development, and different inputs for Ca and Mg to the lake due to changes in drainage area configurations through time, including the changes in saline inputs (Na-Cl type) to the lake. The stable isotopes and the calculated Sr/Ca_w and Mg/Ca_w from sequence C display lower values than those from sequences A and B. The isotopic values from biogenic carbonates of unit C indicate isotopically diluted waters in a hydrologically open lacustrine environment. Distinct δ¹³C and δ¹⁸O plots for molluscs from unit C reflect the different biotopes and metabolism type. For several intervals of the Villarroya succession there is no direct relationships among: (i) salinity changes inferred from invertebrate paleoecology, (ii) paleoenvironmental slices based on isotopic signatures and Me/Ca_w calculations (from biogenic carbonate geochemistry) and (iii) climate in the hinterland deduced from pollen data. Lakes where geochemical behaviour is constrained by sporadic saline inputs and/or relative depletion in Ca due to long periods of Ca-carbonate precipitation or biomineralization, like the Pliocene Villarroya lake was, do not show clear correlation patterns between geochemical signals and climate proxies. In these lakes only major environmental trends display unambiguous geochemical signatures, and only some main shifts in the geochemical signature profiles may be correlated with significant global and/or regional environmental changes that have been reported from other paleoenvironmental records. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献