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1.
Abstract: The Caiziyan Middle and Upper Devonian boundary section is located approximately 30 km northeast of Guilin. It hosts relatively abundant benthic and common–rare pelagic fossils, including brachiopods, corals, tentaculites, and conodonts, which may serve as a better suitable section for pelagic and neritic stratigraphic correlation. In this section, 10 “standard” conodont zones are recognized across the Givetian–Frasnian boundary, including, in descending order, the Lower hassi Zone, punctata Zone, transitans Zone, the Upper falsiovalis Zone, the Lower falsiovalis Zone, disparilis Zone, the Upper hermanni–cristatus Zone, the Lower hermanni–cristatus Zone, the Upper varcus Zone, and the Middle varcus Zone, all of which are defined by the first occurrence of their defining conodont species. The Middle–Upper Devonian (Givetian–Frasnian) boundary is defined by the first occurrence of Ancyrodella pristina in accordance with the Global Stratotype Section and Point (GSSP), which is assigned at 6.2m above the base of bed 19 in the Caiziyan section.  相似文献   

2.
The paper presents data on the composition of biomarkers from bitumen extracts and the chemical structure of kerogen from Corg-rich sedimentary rocks before and after hydrothermal treatment in an autoclave at 300°C. Samples selected for this study are kukersite and Ordovician Dictyonema shale from the Baltics, Domanik oil shale from the Ukhta region, Upper Permian brown coal from the Pre-Ural foredeep, carbonaceous shale from the Oxfordian horizon of the Russian plate, and Upper Jurassic oil shales from the Sysola oil shale bearing region. The rocks contain type I, II, III, and II-S kerogens. The highest yield of extractable bitumen is achieved for Type II-S kerogen, whereas Type III kerogen produces the lowest amount of bitumen. The stages of organic matter thermal maturation achieved during the experiments correspond to a transition from PC2–3 to MC1–2. The 13C NMR data on kerogen indicate that the aromatic structures of geopolymers underwent significant changes.  相似文献   

3.
Previous studies have shown that the oxidizing brines from the Early Permian Rotliegende sequence have influences on the organic matter of Kupferschiefer. However, inside the Rotliegende sequence there are two other black shales: the Lower and Upper Antracosia shales, which have not been studied as much in detail as in Kupferschiefer. In the present study 12 samples from the Lower and Upper Antracosia shales were analyzed by organic geochemical methods in order to clarify the influences of the oxidizing brines on organic matter. The results indicate that the organic matter of the samples from the Upper Antracosia shale and the bottom of the Lower Antracosia shale was oxidized under the influences of the oxidizing brines. The oxidation resulted in a depletion of saturated hydrocarbons and the alky Is of the aromatic compounds.  相似文献   

4.
A model is proposed for a fragment of the chemical structures of the geopolymers based on elemental analysis and the study of the composition of the pyrolysis products of kerogen from the Upper Jurassic and Devonian formations in the East European Platform. The Sorg/C ratio in kerogen from oil shales from J3v2 is 0.4 or higher, and this kerogen belongs to type II-S, while kerogen from the Domanik rocks does not contain S and belongs to type II. The composition of the pyrolysis products of the Upper Jurassic kerogen testifies to the presence of polysulfur-bound structures in this geopolymer, whose thermolysis results in disulfuric cyclic compounds. No structures of this type are contained in Domanik kerogen. Oxygen-bearing groups in J3v2 kerogen are thought to be partly concentrated on simple-ether bonds, whereas D3dm kerogen is likely dominated by compound-ether and carboxyl structures. Nitrogen-bearing structures in kerogen from Upper Jurassic and Domanik formations are of different genesis: while nitrogen-bearing structures in Jurassic kerogen are mostly aminoacids, Domanik kerogen contains chitin derivatives.  相似文献   

5.
广西六景泥盆纪吉维阶-弗拉斯阶界线层牙形石生物地层   总被引：2，自引：1，他引：1  
广西六景泥盆系剖面是我国泥盆系标准剖面之一 ,通过对其吉维阶 -弗拉斯阶界线上下地层进行详细的牙形石生物地层研究 ,自上而下识别出 12个牙形石带 :Palmatolepis jamieae带、Palmatolepis hassi带、Palmatolepispunctata带、Palmatolepistransitans带、上 Mesotaxisfalsiovalis带、下 Mesotaxisfalsiovalis带、Klapperina dispar-ilis带、上 Schmidtognathus hermanni- Polygnathus cristatus带、下 Schmidtognathus hermanni- Polygnathus cristatus带、上 Polygnathus varcus带、中 Polygnathus varcus带、下 Polygnathus varcus带。吉维阶 -弗拉斯阶界线 (即中 -上泥盆统界线 )由 Ancyrodella binodosa→ Ancyrodella rotundiloba early form→ Ancyrodella rotundiloba late form这一演化线系中的 Ancyrodella rotundiloba early form的首次出现确定 ,处于下 Mesotaxis falsiovalis带下部 ,在谷闭组底界之上 1.80 m处。  相似文献   

6.
A preliminary assessment of the source potential of the Jurassic section was obtained using organic geochemical data on samples collected from outcrops on Franz Josef Land and Svalbard archipelagoes as well as boreholes in the Barents Sea basin. The presence of organic-rich shale units with good source potential was reported for the first time within the studied section of Early to Middle Jurassic age, along with well-documented Upper Jurassic source rocks. The study provides an assessment of regional variations in the kerogen type, hydrocarbon generation potential, and maturation of organic matter from Jurassic sediments.  相似文献   

7.
The organic rich Safer shales exposed in the north-central part of onshore Marib-Shabowah Basin are evaluated and their depositional environments are interpreted. Total organic carbon contents (TOC) of the shales range from 1.02–16.8 wt%, and yield hydrogen index (HI) values ranging from 130 to 820 mg HC/g TOC, consistent with mainly Type II with minor contributions from Type I and mixed Types II–III kerogens. The Safer shale samples have vitrinite reflectance values in the range of 0.5–1.0 Ro%, indicating early mature to peak mature stage for oil generation. Tmax values range from 429–438 °C, which are in reasonably good agreement with vitrinite reflectance data. Kerogen microscopy shows that the Safer shales are characterized by high amounts of organic matter, consisting predominantly of yellow fluorescing amorphous organic matter and alginite of marine origin. This is supported by their high content of hydrogen rich Type II and I oil-prone kerogen.The biomarker distributions of the Upper Jurassic Safer extracts are characterized by dominant low to medium molecular weight compounds (n-C14 to n-C20), low Pr/Ph ratio (<1.0), high phytane/n-C18 ratios (0.82–2.68), and predominant regular sterane C27. All biomarker parameters clearly indicate that the organic matter was derived from marine algal inputs and deposited under anoxic (reducing) conditions. Hypersaline conditions also prevailed during deposition of these sediments, as indicated by the presence of gammacerane.  相似文献   

8.
A set of organic-rich shales of the upper Permian Longtan Formation, which is widely developed in the northeastern part of the Sichuan Basin, is a key formation for the next step of exploration and development. At present, most studies on this set of formations have focused on the reservoir characteristics and reservoir formation mechanism of the shales, and basic studies on the palaeoenvironment and organic matter(OM) enrichment mechanism have not been fully carried out. In this paper, we recov...  相似文献   

9.
Organic geochemical characterization of cutting samples from the Abu Hammad-1 and Matariya-1 wells elucidates the depositional environment and source rock potential of the Jurassic and Lower Cretaceous successions and the Middle Miocene to Pleistocene section in the southern and eastern Nile Delta Basin. The burial and thermal histories of the Mesozoic and Miocene sections were modeled using 1D basin modeling based on input data from the two wells. This study reveals fair to good gas-prone source rocks within the Upper Jurassic and Lower Cretaceous sections with total organic carbon (TOC) averaging 2.7% and hydrogen index (HI) up to 130 mg HC/g TOC. The pristane/n-C17 versus phytane/n-C18 correlation suggests mixed marine and terrestrial organic matter with predominant marine input. Burial and thermal history modeling reveals low thermal maturity due to low heat flow and thin overburden. These source rocks can generate gas in the western and northern parts of the basin where they are situated at deeper settings. In contrast, the thick Middle Miocene shows fair source rock quality (TOC averaging at 1.4%; HI maximizing at 183 mg HC/g TOC). The quality decreases towards the younger section where terrestrial organic matter is abundant. This section is similar to previously studied intervals in the eastern Nile Delta Basin but differs from equivalents in the central parts where the quality is better. Based on 1D modeling, the thick Middle Miocene source rocks just reached the oil generation stage, but microbial gas, however, is possible.  相似文献   

10.
The first results of U/Pb isotopic dating (LA ICP MS) of detrital zircons from sands from the Middle Cambrian Sablinka Formation, Upper Cambrian Ladoga Formation, Low Ordovician Tosna Formation, and calcareous sands from Syas’ Formation (Sargaevskii horizon of the Upper Frasnian) from Baltica-Ladoga Glint (BLG) of the Southern Ladoga area are presented. The obtained ages of detrital zircons span the intervals 492.7 ± 5.1-3196.4 ± 5.1 Ma (Sablino Formation); 577.9 ± 7–2972.6 ± 13.4 Ma (Ladoga Formation); 509.4 ± 8.5–3247.6 ± 10.1 Ma (Tosna Formation); 451.1 ± 14.7–2442.2 ± 6.9 Ma (Syas’ Formation). A comparison of the obtained isotopic ages of detrital zircons to ages of crystalline complexes composing the Kola-Karelian, Svecofennian, and Sveconorwegian domains of Baltic Shield and Pre-Uralian-Timanian structures of Subpolar and Polar Urals and basement of Pechora Basin was carried out. It is proposed that the Middle Paleozoic sedimentary basin accumulated Upper Frasnian rocks of Syas’ Formation. The basin ranged northward from the present-day BLG and occupied the eastern part of the Baltic Shield.  相似文献   

11.
The hydrocarbon concentrations in rocks of Frasnian, Givetian, and Famennian age are considerably higher than the concentrations in other units in the Devonian section of the Volga-Ural province, U. S. S. R. The maximum hydrocarbon concentration occurs in the Domanik, which is the host for the largest accumulation of ancient organic material on the Russian platform.

The correlation of hydrocarbon A with oils and other hydrocarbons and with organic carbon is very low. Trace elements are distributed uniformly throughout clastic sediments and differentially in precipitates, including clays, marls, and limestones. Iron, manganese, phosphorus, copper, and strontium concentrations increase as the host rocks become more clastic; chromium, niobium, and cobalt decrease. This difference is an additional criterion for mapping ancient pelagic zones and shoreline. However, weathering may lead to artificial concentrations for the various elements.  相似文献   

12.
The Upper Jurassic Madbi Formation, located in the Masila Basin, eastern Yemen, represents the major source rock in this basin. Organic rich shales from two oilfields (Kharir and Wadi Taribah) were analysed to evaluate the type and origin of the organic matter and to determine the factors controlling its deposition. This study is based on geochemical analyses of whole rock (total organic carbon content, Rock-Eval pyrolysis and carbon isotope data) and petrographic analyses on organic matter (kerogen maceral composition and palynofacies) by optical and scanning electron microscopy. Organic petrographic composition of kerogen shows that the Madbi shale is characterized by high amounts of organic matter, consisting predominantly of yellow fluorescing amorphous organic matter and alginite of marine origin. Terrigenous organic materials such as vitrinite, spores and pollen are present in low quantities. The predominance of marine plankton, as indicated by visual kerogen analysis, is consistent with reported carbon isotopic values. It appears that the high amounts of organic matter in the Madbi shale succession might be mainly due to good preservation under suboxic–anoxic conditions. Consequently the Madbi shales possess very good petroleum generative potential, owing to high content of hydrogen rich Type II and I oil prone kerogen.  相似文献   

13.
The Mobarak Formation is near the town of Kiyasar in the south-east of Sari city, northern Iran. This formation conformably overlies the Geirud Formation (Upper Devonian). The lower part of the Mobarak Formation consisting of shales and thin- to medium-bedded limestone toward the top of these sequences changes into alternations of dark limestone and interbedded gray to black shales. Weathered yellow thick-bedded shales are observed at the top of the section. This formation is covered unconformably by sandstones attributed to the Dorud Formation (Lower Permian). The thickness of the formation in this region is 250 m. Four rock units have been recognized in this section. Foraminiferal biostratigraphy shows that the age of the Mobarak Formation in the Kiaysar region ranges from Lower Tournaisian to Early Middle Visean. The foraminifer Zones FAZ1 and FAZ2 are correlated with the Lower Tournaisian and Upper Tournaisian, whereas Zones FAZ3 and FAZ4 correlate with the Visean. Affinities exist between specimens recorded in the Kiyasar section with species known from other regions in eastern and Central Alborz, but there are important differences in their appearance.  相似文献   

14.
The well-developed continental shale sequences in the Western Sichuan Depression are characterised by extremely low porosity and permeability, complex lithologies and strong lateral facies changes. The overall lack of proper characterisation of the shale properties has restricted gas exploration and development in the region. In this study, shales from the fifth member of the Xujiahe Formation of the Upper Triassic (T3x5) are comprehensively characterised in terms of their organic geochemistry, mineral composition, microscopic pore structure and gas content. In addition, the influence of various geological factors on the adsorbed gas content is investigated. We proposed a new model for predicting the adsorption gas content of continental shale. The T3x5 shale sequence is found to be rich in organic matter but with variable mineral compositions, pore types and reservoir physical properties. The porosity and permeability of shales are better than those of siltstones and fine sandstones interbedded with the shale under an overall densification background. Mesopores (2–50 nm) are common in the shale sequence, followed by micropores and then macropores. The gas-adsorption capacity of organic-rich shales increases with increasing TOC and clay-mineral contents, maturity and pressure, but decreases with increasing quartz content, carbonate minerals and temperature. The gas-adsorption capacity can thus be expressed as a function of organic matter, clay-mineral content, temperature and pressure. The calculated results are in good agreement with the experiment results and indicate that adsorption gas in the studied shales accounts for 78.9% of the total gas content.  相似文献   

15.
湘西黑色岩系沉积演化与含矿序列   总被引：10，自引：0，他引：10  
研究了湘西晚震旦世-早寒武世形成黑色页岩的沉积环境和含矿性.黑色岩系形成于沉积盆地斜坡或以下地带,与海平面上升有关.晚震旦世到早寒武世早中期的沉积层序可划分为三个II级层序.海平面上升的结果使下层海水成为还原环境,有机质得以保存,沉积了大面积的黑色岩系.湘西上震旦统、下寒武统分别构成了黑色页岩 磷块岩 硅质岩组合和磷结核 重晶石 石煤 多金属富集层两个成矿系列,含矿层段集中发育于海平面上升期和凝缩层沉积中,在受海底火山、喷泉活动提供丰富物源的背景条件下,有机质参与元素的迁移、富集作用,经成岩期的转化富集成黑色岩系型矿床.  相似文献   

16.
The upper part of Madbi Formation organic-rich shale is considered an important regional source rock in the Masila Basin, Yemen. Ten cutting samples from this Upper Jurassic organic-rich shale were collected from wells drilled in the Kharir Oilfield, Masila Basin in order to geochemically assess the type of organic matter, thermal maturity and depositional environment conditions. Results reveal that Upper Jurassic organic-rich shale samples contain high organic matter more than 2.0 wt.% TOC and have very good to excellent hydrocarbon potential. Marine algae organic matter is the main source input for the Upper Jurassic shale sequence studied. This has been identified from organic petrographic characteristics and from the n-alkane distributions, which dominated by n-C14-n-C20 alkanes. This is supported by the high value of the biomarker sterane/hopane ratio that approaches unity, as well as the relatively high C27 sterane concentrations. A mainly suboxic depositional environment is inferred from pr/ph ratios (1.75–2.38). This is further supported by relatively high homohopane value, which is dominated by low carbon numbers and decrease towards the C35 homohopane. The concentrations of C35 homohopane are very low. The depositional environment conditions are confirmed by some petrographic characteristics (e.g. palynofacies). Detailed palynofacies analysis of Madbi shales shows that the Madbi shale formation is characterised by a mix of amorphous organic matter, dinoflagellates cysts and phytoclasts, representing a suboxic, open marine setting. The Upper Jurassic marine shale sequence in the Masila Basin is thermally mature for hydrocarbon generation as indicated by biomarker thermal maturity parameters. The 22 S/22 S + 22R C32 homohopane has reached equilibrium, with values range from 0.58 to 0.62 which suggest that the Upper Jurassic shales are thermally mature and that the oil window has been reached. 20 S/(20 S + 20R) and ββ/(ββ + αα) C29 sterane ratios suggest a similar interpretation, as do the moretane/hopane ratio. This is supported by vitrinite reflectance data ranging from 0.74% to 0.90%Ro and thermal alteration of pollen and spore. The thermal alteration index value is around 2.6–3.0, corresponding to a palaeotemperature range of 60–120°C. These are the optimum oil-generating strata. On the basis of this study, the Madbi source rock was deposited under suboxic conditions in an open marine environment and this source rock is still within the oil window maturity range.  相似文献   

17.
韩迎建 《地球学报》1987,9(3):171-197
笔者在广西象州中坪马鞍山剖面上泥盆统“融县组”中部,首次发现了地层连续、岩性均一、牙形石带齐全的弗拉斯阶/法门阶界线层。这一界线层完全符合国际泥盆纪地层分会(SDS 1983)作出的关于划分弗拉斯阶/法门阶界线条件的决议。并与被誉为盆地相最佳剖面的西德Schmidt剖面(SDS Newsl.1986,no.1,Doc.C)的牙形石序列基本一致。无论是从岩石的均一性或是牙形石生物的连续性上,马鞍山剖面完全可与西德Schmidt剖面媲美,它是目前国内研究弗拉斯阶/法门阶界线的理想剖面之一。本文除了对这一界线进  相似文献   

18.
田巍  王传尚  白云山  李培军 《地球科学》2019,44(11):3794-3811
上泥盆统佘田桥组是湘中地区页岩气勘探的重要层系之一.为了探讨湘中地区涟源凹陷上泥盆统佘田桥组黑色泥页岩有机质富集机理,系统采集了区内湘新地3井佘田桥组20个泥页岩岩心样品,开展有机碳含量、主量元素、微量元素以及稀土元素等地球化学特征测试,分析佘田桥组页岩的古盐度、古气候、古氧化还原条件和古生产力等古沉积环境.结果表明:佘田桥组底部层段有机碳含量较高（1.28%~2.68%）,平均值为1.69%.页岩主要成分为SiO2（50.27%）、Al2O3（13.66%）、CaO（11.55%）.微量元素Rb、Sr和Zr富集而Co、Mo、Sc和Hf亏损.Sr/Ba、化学蚀变指数（CIA）、Th/U、V/Sc、V/Cr、δU比值表明佘田桥组富有机质页岩段沉积环境为淡水-半咸水、干旱的贫氧-次富氧环境,贫有机质页岩段为咸水、干旱-半干旱的富氧环境.结合区域层序地层特征,综合对比佘田桥组有机碳含量（TOC）与古氧化还原条件、古生产力条件的相关性,揭示出涟源凹陷佘田桥组富有机质页岩段有机质富集的主控因素为古氧化还原环境,而贫有机质页岩段有机质主要来源于陆源供给.   相似文献   

19.
庄汉平  卢家烂 《地质论评》1997,43(4):373-380
白果园银（钒）矿产于震旦系陡山沱组黑色色岩系中。矿床的地球化学和有机地球化学研究表明，黑色页岩含丰富以低等海生生物为主的腐泥型有机质，黑色页岩形成于局限的滞留海盆。  相似文献   

20.
湘西震旦—寒武纪交替时期古海洋环境的恢复   总被引：6，自引：0，他引：6  
前寒武纪至寒武纪的交替时期是地质史和生命史的重要转折。中国南方地区广泛发育了上震旦统、下寒武统的黑色岩系。文中运用沉积学和沉积地球化学的理论和方法对湘西黑色岩系的岩石类型、矿物组成、元素地球化学特征、干酪根的结构以及碳同位素的组成等方面进行了研究 ,讨论了黑色岩系的形成条件 ,恢复了震旦纪 /寒武纪地史转折期的古环境。研究认为 ,湘西地区在晚震旦世和早寒武世地史转折期的生物爆发和高有机质的产率是形成缺氧环境的重要因素之一。  相似文献   

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