Geochemistry and mineralogy of the Al-rich shale from Baluti formation,Iraqi Kurdistan region: implications for weathering and provenance

The mineralogical and geochemical characteristics of the Upper Triassic Baluti shale from the Northern Thrust Zone (Sararu section) and High Folded Zone (Sarki section) Kurdistan Region, Iraq, have been investigated to constrain their paleoweathering, provenance, tectonic setting, and depositional redox conditions. The clay mineral assemblages are dominated by kaolinite, illite, mixed layers illite/smectite at Sararu section, and illite > smectite with traces of kaolinite at Sarki. Illite, to be noted, is within the zone of diagenesis. The non-clay minerals are dominated by calcite with minor amounts of quartz and muscovite in Sararu shale; and are dominated by dolomite with amounts of calcite and quartz in Sarki shale. Baluti shale is classified as Al-rich based on major and minor elements. The chemical index of alteration (CIA) is significantly higher in the Sararu than the Sarki shales, suggesting more intense weathering of the Sararu than the Sarki shales. The index of compositional variability (ICV) of the Sararu shale is less than 1 (suggesting it is compositionally mature and was deposited in a tectonically quiescent setting). More than 1 for Sarki shales (suggest it is less mature and deposited in a tectonically active setting). Most shale of the Baluti plot parallel and along the A-K line in A-CN-K plots suggest intense chemical weathering (high CIA) without any clear-cut evidence of K-metasomatism. Clay mineral data, Al enrichment, CIA values, and A-CN-K plot suggest that the source area experienced high degree of chemical weathering under warm and humid conditions, especially in Sararu. Elemental ratios critical of provenance (La/Sc, Th/Sc, Th/Cr, Th/Co, Ce/Ce*_PN, Eu/Eu*_PN, and Eu/Eu*_CN) shows slight difference between the Sararu and Sarki shales; and the ratios are similar to fine fractions derived from the weathering of mostly felsic rocks. The Eu/Eu^* _CN, Th/Sc, and low K₂O/Al₂O₃ ratios of most shales suggest weathering from mostly a granodiorite source rather than a granite source, consistent with a source from old upper continental crust. Discrimination diagrams based on major and trace element content point to a role of the felsic-intermediate sources for the deposition of Baluti Formation, and probably mixed with mafic source rocks at Sararu section. The chondrite-normalized rare earth elements (REE) patterns are similar to those of PAAS, with light REE enrichment, a negative Eu anomaly, and almost flat heavy REE pattern similar to those of a source rock with felsic components. The source of sediments for the Baluti Formation was likely the Rutba Uplift and/or the plutonic-metamorphic complexes of the Arabian Shield located to the southwest of the basin; whereas the Sararu shale was affected by the mafic rocks of the Bitlis-Avroman-Bisitoun Ridge to the northeast of Arabian Plate. The tectonic discrimination diagrams, as well as critical trace and REE characteristic parameters imply rift and active setting for the depositional basin of the shale of Baluti Formation. The geochemical parameters such as U/Th, V/Cr, V/Sc, and Cu/Zn ratios indicate that these shales were deposited under oxic environment and also show that Sarki shale was deposited under more oxic environment than Sararu.     

西藏措勤断块中—上三叠统嘎热扎地组的建立

在西藏措勤断块新建了中三叠统—上三叠统卡尼阶岩石地层单位——嘎热扎地组.在建组剖面上,嘎热扎地组厚约485 m,下部岩性以碎屑岩为主,上部岩性为碎屑岩夹灰岩.嘎热扎地组与下伏上二叠统—下三叠统木纠错组、上覆上三叠统诺利阶麦龙岗组均为整合接触关系.该组尚未发现指示地层时代的化石,但前人在其下伏的木纠错组中发现了早三叠世牙...     

云南鲁史三合洞组地层时代讨论

云南兰坪盆地三合洞组的时代存在争议,有早古生代和中生代两种观点。本文通过对云南鲁史上三叠统三合洞组和挖鲁八组岩石地层、古生物化石、微体化石及碎屑锆石U-Pb年代学研究,认为三合洞组时代为晚三叠世。本区三合洞组生物碎屑灰岩、泥晶灰岩及白云质灰岩与挖鲁八组炭质板岩呈整合接触关系,与歪古村组砂质板岩呈逆断层接触关系,整体表现为倒转地层。挖鲁八组炭质板岩中采获叉皱海燕蛤、虚海燕蛤等晚三叠世化石,而三合洞组灰岩中的小欣德牙形刺、奥泽克刺、滑梯螺、长卵形槽花介等微体化石时代也为晚三叠世。笔者从挖鲁八组粉砂岩中获得碎屑锆石U-Pb年龄,其最小年龄为218 Ma,指示挖鲁八组的最晚沉积时代为晚三叠世。综合生物化石和同位素年代学资料,认为兰坪盆地三合洞组的时代为晚三叠世。     

ON MANGANIFEROUS FORMATIONS AND THE METALLOGENY OF MANGANESE,PAPER I. VOLCANOGENIC-SEDIMENTARY MANGANIFEROUS FORMATIONS

The article describes Carboniferous and Lower Liassic coal measures in Franz Josef Land, and a "2-ft coal bed" at the base of the Carboniferous motley sandstones observed by Fisher in Cook Cliffs at the south end of Prince George Land. Until recently the Cook Cliffs coal was identified by Dibner as "Paleozoic redeposited in Upper Triassic time." Later Dibner reassigned the coal and related beds to the Upper Triassic. Some doubt on this age is cast by the fact that the only coals on Spitzbergen are Lower Carboniferous. Ye. M. Andreyeva studied the coal's spores and found only Lower and Middle Carboniferous species. Traveling southeast of Wilczek Land in 1935, Yermolayev recovered coals he believed to be Paleozoic. Based on these finds, there is a strong likelihood of Paleozoic coals on Franz Josef Land. The Upper Triassic Vasil'yevsk Formation contains Noric to Rhaetic plants and spores. At Goristyy Cape (Champ Island) two brown coals occur; one is 1 m thick; 55 m higher is a 2-m bed coked at the top by an overlying basalt flow. The petrography of the coals is discussed. The Tegetthof Formation, based on its plant fossils, is Lower Liassic, compatible with sections on Spitzbergen. Next higher are Aalenian siltstones, Bathonian and sandy limestones with Volgian clams. Still higher are Lower Cretaceous volcanics with intercalated sandstones, shales and coals, divisible into the Tikhaya Cove Formation and Salisbury Formation. Altogether there are 13 coal beds in Franz Josef Land, ranging from Carboniferous up into the Lower Cretaceous (with 9 coal beds). Interesting petrographic details are included.—B. N. Cooper.     

Petrological and geochemical interpretation of Triassic–Jurassic boundary sections from northern Iraq

Triassic–Jurassic sedimentary successions (Baluti and Sarki formations) in northern Iraq record a variety of environmental changes that may be related to global Triassic–Jurassic (Tr/J) boundary events. The diversity of some benthic fauna decreases through the transitional boundary beds. The coastal marine environment of the lower part of the Baluti Formation is followed by shallower tidal flat and supratidal marginal marine environments at the transitional boundary with the Jurassic‐age Sarki Formation. The alternating calcareous mudrocks and dolomitic limestones of the transitional succession are overlain by a succession of calcareous mudrocks and dolomicrites that form a dolocrete bed in the latest Triassic. The early Jurassic carbonates (lower part of Sarki Formation) were deposited in a shallow‐marine to lagoonal environment. Geochemical evidence supports this interpretation. TOC% increases towards the Tr/J boundary and the lower part of the Sarki Formation. This increase can be interpreted as resulting from the primary precipitation of dolocrete as palaeosol horizons. The variations in the oxygen isotope ratios mainly reflect the facies and diagenetic effects. Th/K ratio is generally constant and shows an increase in the calcareous mudrock beds of the upper part of the Baluti Formation, possibly related to the degradation of K‐bearing clay minerals. Low Th/U ratios are due to the depletion in thorium, typical of many marine carbonates rather than to an increase in authigenic uranium. This explanation is also corroborated by the presence of abundant fossils in some of the studied carbonates. Copyright © 2013 John Wiley & Sons, Ltd.     

广西柳桥地区上二叠统礁灰岩中发现沥青

研究区位于广西扶绥县东门镇和柳桥镇之间,主要分布上二叠统和下三叠统地层.上二叠统包括合山组、上二叠统礁灰岩和大隆组.下三叠统罗楼组由泥岩和灰岩组成.大隆组主要为放射虫硅质岩和泥岩,含有丰富的放射虫、有孔虫、介形虫、菌藻类、腕足类、菊石类和双壳类化石,是好的烃源岩层.礁灰岩具有大量裂隙和孔洞,是好的储集层.在柳桥地区东攀剖面、岜陇剖面和岜料剖面,礁灰岩裂隙和孔洞普遍被沥青充填.研究区上二叠统礁灰岩是值得注意的油气勘探远景区.     

Palynofacies and hydrocarbon generation potential of the upper Triassic Kurrachine Formation and lower part of the Baluti Formation, Mosul Block, Northwestern Iraq

Three exploration wells were selected near Mosul city (Az-29, Bm-15, and Kd-1) to study the palynozones and hydrocarbon generation potential of the Upper Triassic Baluti and Kurrachine Formations. This study was completed in two phases: The first was a study of palynofacies and their paleoenvironmental indications, degree of preservation, diversity of palynomorphs, and organic maturity of the rocks according to palynomorphs’ color using a refracted light microscope. More than 80 slides of organic matter were used for this study. Four palynofacies were tentatively recognized. (1) The first palynofacies is diagnostic of the Baluti Formation in the Az-29 and Kd-1 wells; (2) The second palynofacies appeared at different depths in the Kurrachine Formation in three wells. (3) The third was only found between the depths of 4,534 to 4,685 m in the well Az-29. (4) The fourth was only found between 3,500- and 3590-m depth in the well Bm-15. A distal coastal marine environment is suggested for the Baluti Formation and restricted lagoonal environment for the Kurrachine Formation. The second phase used organic geochemical analyses to confirm the suggested paleoenvironmental and hydrocarbon generation material. Three techniques were used, namely total organic carbon, pyrolysis, and pyrolysis gas chromatography, on more than 35 samples from different depths in three wells. The analyses proved that a sufficient quantity of organic matter occurs that and has suitable maturity for hydrocarbon generation potential of oil and gas.     

西藏边坝-洛隆地区下白垩统边坝组的建立及其意义

边坝组是新建立的一个岩石地层单位。该组与下伏下白垩统多尼组呈整合接触,与上覆上白垩统宗给组呈角度不整合接触关系。岩性以紫红色深灰色粉砂质泥岩夹薄层白云岩为特征,深灰色薄层粉砂质泥岩中产丰富的双壳类化石Trigonioides(Diversitrigonioides)xizangensis-Pleuromya spitiensis组合。边坝组的建立完善了该地区下白垩统地层系统,对冈底斯北缘弧后前陆盆地白垩纪岩相古地理研究具有重要意义。     

Planktic Foraminiferal Biostratigraphy of the Cretaceous Oceanic Red Beds in Kangmar,Southern Tibet,China

The planktic foraminifera of the Chuangde Formation (Upper Cretaceous Oceanic Red Beds, CORBs) as exposed at Tianbadong section, Kangmar, southern Tibet has been firstly studied for a detailed for a detailed biostratigraphy elaboration. A rich and well-preserved planktic foraminifera were recovered from the Chuangde Formation of the Tianbadong section and the Globotruncanita elevata, Globotruncana ventricosa, Radotruncana calcarata, Globotruncanella havanensis, Globotruncana aegyptiaca, Gansserina gansseri and Abathomphalus mayaroensis zones have been recognized. The planktic foraminiferal assemblage points to an early Campanian to Maastrichitian age for the CORBs of the eastern North Tethyan Himalayan sub-belt, which also provides a better understanding of the shifting progress of the Indian Plate to the north and the evolution of the Neotethyan ocean. The lithostratigraphy of the Chuangde Formation of the Tianbadong section comprises two lithological sequences observed in ascending succession: a lower unit (the Shale Member) mainly composed of purple (cherry-red, violet-red) shales with interbedded siltstones and siliceous rocks; and an upper unit (the Limestone Member) of variegated limestones. The strata of the Chuangde Formation in the Tianbadong section are similar to CORBs in other parts of the northern Tethyan Himalaya area of Asia (Gyangze, Sa’gya, Sangdanlin, northern Zanskar, etc.). The fossil contents of the Chuangde Formation in the sections (CORBs) studied provide a means of correlation with the zonation schemes for those of the northern Tethyan Himalayan sub-belt and the Upper Cretaceous of the southern Tethyan Himalayan sub-belt. Paleogeographic reconstruction for the Late Cretaceous indicates that the Upper Cretaceous Chuangde Formation (CORBs) and correlatable strata in northern Zanskar were representative of slope to basinal deposits, which were situated in the northern Tethyan Belt. Correlatable Cretaceous strata in Spiti and Gamba situated in the southern Tethyan Belt in contrast were deposited in shelf environments along the Tethyan Himalayan passive margin. CORBs are most likely formed by the oxidation of Fe(II)-enriched, anoxic deep ocean water near the chemocline that separated the oxic oceanic surface from the anoxic.     

三江北段东莫扎抓矿区构造变形特征

已有关于青藏高原隆升的各种构造模型多重视新生代变形而忽略了早期构造变形的限制.本文以三江北段东莫扎抓矿区为研究对象,通过详细的构造-岩相填图,恢复了矿区二叠纪以来变形序列,结合区域资料讨论了变形事件的大地构造背景.研究表明矿区发育中-下二叠统九十道班组灰岩、上二叠统那益雄组碎屑岩、上三叠统结扎群甲丕拉组碎屑岩和上三叠统结扎群波里拉组灰岩4套地层系统,二叠系与三叠系之间为不整合接触,局部被近南北向逆断层代替.北西向逆断层横亘矿区,断层上盘三叠纪碎屑岩和灰岩整体北倾,断层下盘三叠纪岩石被左右两条走滑断层夹持向南挤出.在图面和露头尺度上矿区叠加褶皱明显,南北向剖面上多见紧闭的倾伏褶皱,近东西向剖面上则为开阔水平的斜歪褶皱,表明南北向剖面上观察到的是已被叠加的早期褶皱,为矿区第一期变形,其形成与三叠纪末古特提斯洋盆闭合有关.始新世晚期印-亚大陆碰撞地壳缩短形成矿区第二期构造,即北西向逆断层和褶皱叠加.第三期近南北向逆断层可能形成于始新世末,与印-亚大陆碰撞引起的侧向旋转有关.     

1∶25万帕度错幅、昂达尔错幅成果与进展

新建9个正式岩石地层单位、4个非正式地层单位;将上三叠统日干配错群解体为6个岩石地层单元;解体中上侏罗统雁石坪群;将色哇组分为三段;将班公湖怒江带木嘎岗日群解体为4个岩石地层单元;在西藏首次发现(上三叠统姜钟组)纳拉菁耳羽叶;在羌塘盆地首次发现(下—中侏罗统色哇组)辐鳍鱼类化石;新建8个侵入岩填图单位,时代为晚侏罗世—新近纪末期;在班 怒结合带塔仁本一带首次发现了洋岛型玄武岩;新发现了一系列新生代岩浆岩;在班怒带及南羌塘盆地中发现一些呈串珠状分布的小型斑岩体;发现班 怒带上时代最新的枕状玄武岩。     

川西北若尔盖一带三叠系层序及沉积环境分析

川西北地区三叠系广泛发育，其地层层序及岩性特征与相邻的西秦岭南部一带十分相似。根据若尔盖—南坪实测地层剖面资料的对比研究，将该区三叠系划分为：中三叠统光盖山组和上三叠统咀朗组、纳鲁组、卡车组４个岩石地层单位。通过沉积相标志的综合分析，该区中—晚三叠世时期主要有以下几种沉积类型：碳酸盐岩碎屑流沉积，等深流沉积，陆源碎屑浊流沉积，非重力流正常深海盆碳酸盐岩及碎屑岩沉积。表明该区为大陆斜坡至深海盆地环境     

The Triassic of Timor: Lithostratigraphy, chronostratigraphy and palaeogeography

The palaeontologically rich and lithologically diverse Triassic successions of Timor provide a key stratigraphic and palaeontological link between northwestern Australia and other terranes of former eastern Gondwana (present-day Southeast Asia). Timor is now located in the zone of collision between the northern margin of the Australian continent and island arc terranes bordering the Eurasian plate, with the Triassic successions exposed in a fold-and-thrust belt and an extensive mélange complex. Three formal lithostratigraphic units have been defined previously within the main Triassic succession in Timor (Niof, Aitutu and Babulu formations), with a fourth, the Wai Luli Formation, primarily Jurassic in age but extending down into the Triassic. The Niof Formation (Anisian to Ladinian, possibly also Early Triassic) is a fine-grained deepwater succession, succeeded conformably by the Aitutu and Babulu formations (Ladinian to Norian/Rhaetian), which were deposited contemporaneously, with the Aitutu Formation continuing locally into the Lower Jurassic. The Aitutu Formation consists of deep shelf limestones interbedded with shales and marls, while the Babulu Formation is a deltaic to turbiditic siliciclastic succession. The Late Triassic to Jurassic Wai Luli Formation is characterised by marine shales and marls.Informal stratigraphic units include the Cephalopod Limestone Facies, a Rosso Ammonitico-type deposit, which contains an extremely rich fossil fauna (particularly ammonoids) and ranges through the entire Triassic; and the Fatu Limestone and Pualaca Facies which consists of shallow to marginal marine carbonates (mud mounds, oolitic limestones and reefs) restricted to the Late Triassic. Facies diversity was low during the Early Triassic and Anisian, but became more pronounced from the Ladinian and continuing through the Late Triassic, probably as a consequence of renewed tectonic extension. Triassic extension was not associated with major volcanism, unlike a previous phase of extension in the Early Permian.The Cablac Limestone Formation, originally defined as a Miocene stratigraphic element, is now recognised to be at least partly Late Triassic–Early Jurassic in age, with lithologies comparable to parts of the Fatu Limestone. The stratigraphy of these shallow marine carbonate sequences is clearly in need of rigorous revision, but it is not yet possible to suggest appropriate redefined formations.     

论西藏扎达上白垩统波林夏拉组

上白垩统波林夏拉组的命名地点位于西藏西南部扎达波林,是一套以泥灰岩及灰岩为主的地层,底部以含海绿石灰岩与下伏下白垩统嘎姐组含海绿石石英砂岩整合接触,未见顶。波林夏拉组的时代据其所含丰富浮游有孔虫可被确定为晚白垩世Albian晚期至Maastrichtian晚期,其所含化石组合可以与晚白垩世特提斯喜马拉雅从台地到盆地的同...     

Detrital carbonate grains as provenance indicators in the Upper Cretaceous Pietraforte Formation (northern Apennines)

The Upper Cretaceous Pietraforte Formation, an allochthonous unit of the Ligurian domain in the northern Apennines, provides a case study of the importance of detrital carbonate grains for provenance determination in sandstones. The Pietraforte Formation is composed of turbidite sandstones with subordinate conglomerate, deposited in an external sector of the Ligurian ocean, close to the Adriatic margin. The sandstones have a lithic composition, characterized by abundant sedimentary and metasedimentary rock fragments (35–56% of the terrigenous framework), little feldspar (<7%) that is almost exclusively plagioclase, and a high ratio of fine- to coarse-grained polycrystalline quartzose grains to total quartzose grains (average Q_p/Q_t=0.37). Carbonate rock fragments dominate the lithic association of both sandstones and conglomerates and provide the most detailed information for provenance determination. They are composed primarily of dolostones and a wide variety of limestones containing identifiable age-diagnostic microfossils. Fossils and rock textures of carbonate clasts document the erosion of Upper Triassic to Lower Cretaceous shelf and pelagic carbonate units which can be matched with Mesozoic rock types present in the Tuscan domain of the northern Apennines. Compositional results constrain the source of the Pietraforte Formation sandstones to the western margin of the Adriatic plate, from uplifted sedimentary and metasedimentary rocks of the Tuscan domain and its low-grade metamorphic basement. Coeval intrabasinal sources provided additional supplies to the depositional basin of the Pietraforte Formation; this intrabasinal supply consists of shelf carbonate allochems, planktonic foraminifera and argillaceous rip-up clasts. The presence of carbonate grains from shallow-water environments may indicate the existence during deposition of marginal shelf areas favourable for carbonate allochem production.     

川西坳陷中段上三叠统须家河组二段层序地层初析

须家河组二段是川西坳陷中的区域气层。长期以来，地质分层采用岩石地层单位界面。这一界面的穿时性，造成了构造演化分析中的误差。笔者以钻井、测井和地震资料为主要研究对象，在引入地震反射“等时”约束条件的前提下，通过对须家河组长期基准面旋回层序及须二段中期基准面旋回层序的划分和对比，在建立高分辨率时间一地层格架的基础上，经过地震微相特征的仔细分析，确认须二段顶面属Ⅲ级整合界面。     

西藏1∶5万改则县北亭贡南部地区地质矿产调查主要成果

西藏1∶5万改则县北亭贡南部地区地质矿产调查项目取得的主要成果有:①通过采集到的古生物化石依据,新建上三叠统嘎拉弄组,厘定上侏罗统吐卡日组;②通过精准锆石U-Pb测年,得出闪长岩体年龄值为(120±0.7) Ma,下白垩统美日切错组年龄值为(121.9±1.6) Ma,证实早白垩世是测区最为剧烈火山作用时期,与班公湖-怒江洋的俯冲有关。     

青藏高原东北缘祁连山地区古地震记录与区域构造意义

青藏高原东北缘的地质地貌特征与基本构造格架受阿尔金左行走滑断裂、东昆仑左行走滑断裂和海源左行走滑断裂控制,在青藏高原的碰撞造山过程中地震作用贯穿始终.2011至2012年,作者对青藏高原东北缘东起靖远(海原断裂东段)西至昌马盆地(阿尔金断裂东南)的软沉积物变形(震积岩)进行的系统调研表明,青藏高原东北缘祁连山地区从三叠纪至第四纪各时代(侏罗纪以外)的地层中,均发现丰富的古地震纪录(震积岩).代表性震积岩发现点和层位有:靖远宝积山上三叠统、靖远糜滩乡下白垩统、昌马盆地下白垩统以及赤金堡和酒泉磁窑口附近的第四系.主要的震积岩类型有:液化脉、负载、球-枕构造、液化卷曲、层间微断裂等.根据区域地质资料分析,这些震积岩均分布于区域性大断裂附近.本文简单讨论了主要震积岩发现点与其相邻的区域构造(地震)活动之间的关系,根据靖远附近上三叠统普遍发育震积岩,提出海原断裂带的初始活动时间很可能就在晚三叠世,与青藏高原东缘龙门山地区印支期的造山地震同时期.     

西藏措勤打加错地区上三叠统江让组的发现及其地质意义

在西藏措勤打加错地区新发现上三叠统江让组,其为一套海相碎屑岩及碳酸盐岩沉积建造,岩性主要为不等厚层状石英质砾岩、深灰色薄层状—块状生物碎屑微晶灰岩、含砂粉砂质微晶灰岩、含石英砾质生物碎屑灰岩、砂屑灰岩夹钙质细砂岩,产珊瑚Distichophyllia sp.,Volzeia sp.,Montlivaltia sp.,M.cf.xainzaensis、海绵:Hartmanina sp.和双壳类Xenocardita?sp.,时代为晚三叠世卡尼期-诺利期,与下二叠统昂杰组呈角度不整合接触。江让组在该地区的发现,完善了冈底斯西部三叠纪的地层系统,为研究印支运动对冈底斯西部的影响和古特提斯洋的演化提供了依据。     

Palynological evidence for Jurassic strata in the Panagarh area, West Bengal, India

The Rajmahal Traps were discovered in the Panagarh area, West Bengal, during the exploration for coal resources. A Gondwana succession was found beneath the traps, consisting of the Early Cretaceous Intratrappean Rajmahal Formation, the Early Triassic Panchet Formation and the Late Permian coal-bearing Raniganj Formation. The present palynological study was aimed at confirming the age of the Panchet Formation. As a result of this study it has been found that Jurassic sediments are also included in the Panchet Formation. The study has revealed that the Panchet Formation, defined on a lithological basis, is a time-transgressive unit extending from the Early Triassic to the Late Jurassic, with a phase of non-deposition between the Middle Triassic and Middle Jurassic.