Occurrence of Cordaitales from lower Gondwana sediments of Ib-River Coalfield, Orissa, India: An Indian scenario

The Ib-River Coalfield in Orissa State is a part of Mahanadi Master Basin. Recent extensive investigations were conducted in this Coalfield to locate fossiliferous beds in the Lower Gondwana deposits and as a result a large cache of plant fossils were recovered from Lower Permian sediments (Barakar Formation) exposed in Jurabaga and Lajkura Collieries. The complete flora includes 23 genera representing nine orders viz., Lycopodiales, Equisetales, Sphenophyllales, Filicales, Cordaitales, Coniferales, Ginkgoales, Cycadales and Glossopteridales. Only the Cordaitales, represented by four genera i.e., Noeggerathiopsis, Cordaites, Euryphyllum and Kawizophyllum are discussed in this paper. Cordaitalean leaves are described for the first time from this coalfield; the remaining plant groups will be considered in a subsequent publication. Cordaitalean leaves attributable to Noeggerathiopsis hislopii, Noeggerathiopsis minor, Euryphyllum whittianum, Euryphyllum maithyi, Kawizophyllum dunpathriensis and Cordaites sp. constitute about 13.90% (111 specimens) of the total plant assemblage collected from this Coalfield. Of the cordaitaleans, N. hislopii is most abundant (47.75%; 53 specimens) followed by E. whittianum (40.54%; 45 specimens). A summary of the distribution of Cordaitales throughout the Indian Gondwana is also presented. Floristic composition varies stratigraphically at the two Barakar exposures (Lajkura and Jurabaga Collieries). Cordaitales are preserved only in the lowermost (4th) horizon (lower floral zone). Strata in these collieries have been assigned to the lower and upper Barakar Formation based on floristic content and an Early Permian (Artinskian) age is assigned.     

Palaeobotany of Gondwana basins of Orissa State, India: A bird's eye view

Gondwana basins of Orissa State constitute a major part of the Mahanadi Master Basin. These Gondwana sediments, ranging from Asselian to Albian in age, contain remnants of three basic floral assemblages i.e. Glossopteris Assemblage, Dicroidium Assemblage and Ptilophyllum Assemblage which can be recognized through the Permian, Triassic and Early Cretaceous, respectively. The megafloral assemblages of different basins of this state are discussed briefly. This report mainly deals with the plant species diversification in different lithological formations and the development of flora in the Gondwana basins of Orissa. A number of successive megafloras are recognized. Among those, leaves are the dominant part of the preserved flora, followed by fruits and roots. No wood parts are preserved in the major basins. These pre-angiospermic floras have been systematically analyzed to depict the evolutionary trends, and palaeofloristics of these basins. The distribution of plant fossils in different formations of these basins depicts provincialism in Gondwana flora within the Orissa.     

Similarity of palaeocurrent pattern of Lower Gondwana formations of the Talchir and the Ong-river basins of Orissa, India – An indication of dismemberment of a major Gondwana basin

In peninsular India, Gondwana strata are disposed linearly as strings of isolated basins conforming to the trend of the present day Koel–Damodar, Son–Mahanadi and Prahnita–Godavari river valleys. There are seven exposed and one concealed Gondwana basins/outliers in Orissa belonging to the Son–Mahanadi valley system. The present study is concerned with the consanguinity of the Talchir and Ong-river basins of Orissa. Similarity and dissimilarity of palaeocurrent population in these two basins were taken into consideration to test the consanguinity of the basins under consideration. Statistical analysis suggests that the sampled palaeocurrent data of the same formation belong to the same population when considered for both basins. In geologic terms, the basin parameters were identical when considered for either the Talchir or the Karharbari Formation that proves the consanguinity of both the basins and the possible existence of a master basin that encompassed other sister Gondwana basins in Orissa.     

Influence of fluvial‐tidal interactions on the nature of cross‐stratified packages in a deltaic setting: examples from the Barakar Coal Measure (Permian), Satpura Gondwana Basin,central India

Nine different types of cross‐stratified packages from the coal‐bearing, deltaic succession of the Barakar Formation (Permian) of the Satpura Gondwana Basin, central India, are described. The deposits are characterized by periodic mudstone drapes, reactivation surfaces including all other features suggestive of deposition from periodically unsteady, tidally‐influenced flows. The inferred flow patterns varied from purely bidirectional to pulsating unidirectional. The different types of cross‐stratified packages are interpreted to have resulted from superimposition of ebb‐oriented, steady, unidirectional fluvial currents of variable strength on the tidal flow in a deltaic setting. The study helps to distinguish cross‐strata that may develop in settings where fluvial and tidal currents interact. Copyright © 2004 John Wiley & Sons, Ltd.     

Taxonomy and affinity of Early Mesoproterozoic megascopic helically coiled and related fossils from the Rohtas Formation, the Vindhyan Supergroup, India

A well preserved assemblage of compressed, straight, circular to sinuously coiled megascopic and helical carbonaceous fossils and other varied megascopic morphoforms are known from the Early Mesoproterozoic Rohtas Formation, Semri Group within Vindhyan Supergroup exposed in Katni district of central India. These megascopic remains are preserved as impressions, compressions, partially mineralized remains, and/or epi-relief. Some of the forms are typical filamentous empty sheaths and others are trichomes, with cell like entities under various stages of degradation. This study, based on fresh collections and also of the topotype material of the helically coiled megascopic fossils, straight forms and related fossilized remains occurring as epi-relief from Katni indicate that the two morphotaxa are distinct entities and possibly appear to be prokaryotes. Grypania spiralis and Katnia singhii are most likely of cyanobacterial origin. Spirally coiled and circular fossils, with epi-relief, and which probably represents a tissue grade organism, are considered as Spiroichnus beerii Mathur, 1983. Linear sheet-like carbonaceous solitary form has been placed in the morphotaxon Proterotainia and described as P. katniensis n. sp. Certain rare circular, carbonaceous forms are considered as Chuaria sp. A few circular disc-like forms found in the assemblage are treated as dubiofossils.     

Depositional Record of Tidal-Flat Sedimentation in the Permian Coal Measures of Central India: Barakar Formation, Mohpani Coalfield, Satpura Gondwana Basin

The Permian Barakar Formation in the Mohpani coalfield, Satpura Gondwana basin, is composed of three broad lithologies that occur repetitively and are iterdigitated: (1) several metres thick coarse- to medium-grained sandstone bodies with scoured bases, (2) 5-20 m thick medium- to fine-grained sandstone bodies and (3) 5-20 m thick mudstone-dominated packages with variable proportions of centimetre- to decimetre-scale, fine- to medium-grained sandstone, carbonaceous shale and coal. The Barakar strata were previously interpreted as deposits of braided rivers and associated inter-channel flood basin in a continental setting. However, this study recognizes signatures of tidal current from the mudstone-dominated packages implying marine influence during Barakar sedimentation.

The mudstone-dominated sediment bodies are the focus of this paper and comprise of three lithofacies that bear imprints of tidal processes during Barakar sedimentation: (1) heterolith, (2) sandstone, and (3) coal-carbonaceous shale, which alternate with one another within individual bodies. The heterolithic facies show interlayering of sandstone and claystone resembling flaser, wavy and lenticular bedding, as well as pinstripe stratification. Successive sandstone-mudstone couplets indicate periodic waxing and waning of flows. Within individual heterolithic packages, the sandstone:claystone ratio along with the bedding style, varies cyclically upwards giving rise to alternate sandstone-dominated and claystone-dominated intervals suggesting tidal velocity fluctuation reflective of spring-neap lunar cycle. Thickness plots of successive sand-mud couplets also reveal cyclic variation with a conspicuous periodicity of around 12 couplets per cycle, which corroborates the spring-neap-spring (or neap-spring-neap) lunar cycle. Presence of abundant desiccation cracks indicates periodic emergence and points towards an intertidal setting. The sandstone facies is characterized by a variety of wave-generated features such as bundled and chevron upbuilding of lamina, bi-directional foreset orientations, offshooting and draping laminae, scour-and-drape feature, swollen lens-like geometries suggesting their emplacement under storm-induced combined-flow on the tidal-flat. The coal-carbonaceous shale facies represent supratidal marsh environment.     

Dimorphism in Placenticeras mintoi from the Upper Cretaceous Bagh Beds, central India

The Upper Cretaceous Bagh Beds yield many biota of which ammonoids are particularly well known. Previously Bagh ammonoids were grouped into many genera and species within several families. The present study, however, shows that failure to recognize dimorphism and a wide range of interspecific variation within the single genus Placenticeras perhaps results in taxonomic oversplitting. Specific dimorphism in P. mintoi has been established.     

The distribution of dimethylcarbazoles in oils from the Pearl River Mouth Basin, South China Sea

C2-carbazole isomers have been investigated in crude oils from the Hui-Liu Structure Ridge (HLSR) in the Pearl River Mouth Basin (PRMB), South China Sea. The NH shielded isomer, as well as the NH partially shielded isomers, was detected in high abundance and the NH exposed isomers in lower abundance. A small-enrichment trend of 1,8-dimethylcarbazole (DMC) was observed in crude oils along the western part of HLSR (WPHLSR), which may indicate little effect of migration on the C2-carbazole distributions. Two strikingly different distribution patterns of NH partially shielded isomers were observed in the reservoirs along the WPHLSR: one with a preference of 1,3- and 1,6-DMCs and the other with a preference of 1,4- and 1,5-DMCs. All of the oils occurring in the Upper reservoirs have a preference of 1,3- and 1,6-DMCs, whereas those trapped in the Lower reservoirs show a preference of 1,4- and 1,5-DMCs, which may indicate there are two petroleum migration systems in the WPHLSR.     

黑河下游额济纳盆地景观空间格局动态变化分析

基于1977、1993、2001和2005年4期Landsat遥感影像资料,选用面积、斑块数量、斑块平均大小、斑块面积标准差和面积加权平均斑块形状指数,对额济纳盆地景观空间格局的动态变化进行了分析。结果表明:乔木林面积持续减少,表现为绿洲外部及边缘的小斑块大量消失;灌木林在早期以斑块的萎缩和破碎化为主,随后因建群种演替为旱生生态型而趋于稳定,2001年后部分小斑块消失;草地在1977～1993年以小斑块的消失为主,1993～2001年以斑块的破碎化为主,2001年后斑块的团聚性增强,草地扩张;戈壁在1977～2001年斑块的破碎化程度增大,2001年后受草地恢复和巴丹吉林沙漠入侵的影响,总面积和斑块数量减少;沙地在研究期间持续扩张,1977～1993年表现为向植被的分散入侵,1993～2001年斑块的扩张和新小斑块的形成同步进行,2001年后以斑块的扩展和相互连通为主,团聚性增强。黑河输水量的变化是研究区景观空间格局动态变化的主要驱动力,在生态输水工程实施后,生态环境的恶化趋势得到了一定的扼制,但仍需采取措施提高输水的生态效果。     

青海通天河盆地古、新近纪沉积特征及其意义

通过对青海通天河盆地古、新近纪地层层序、沉积特征、物源区及沉积环境分析,建立其垂向相序,总结出该区具冲积扇相、三角洲相、湖泊相的特点,并得出通天河盆地古、新近纪物源区主要为北部开心岭隆起区的结论。根据石膏、灰岩夹层及粒度特征等环境标志推测:中始新世气候炎热湿润,晚始新世气候炎热干燥,渐新世气候炎热湿润,中中新世气候温暖潮湿;青藏高原的隆升具有阶段性。     

西藏尼玛盆地古近纪湖相油页岩正构烷烃特征及其古环境与古气候意义

尼玛盆地地处青藏高原中部特殊区域,自新生代以来沉积了大套连续的湖相暗色油页岩,其富含生物分子化石,对重建青藏高原古气候和古环境具有重要意义。本文通过对尼玛盆地古近系牛堡组康嘎勒剖面正构烷烃及相关参数分布特征进行研究,结果显示,剖面油页岩正构烷烃分布从底到顶由单峰前峰型向单峰后峰型过渡,具2个旋回周期;碳优势指数相对稳定,但TAR、ACL、P_aq及nC_≤21/nC_≥25变化较大,表明湖泊沉积有机质由内源为主的低等藻类向高等水生植物和外源陆生高等植物转变,且区域气候环境由温凉湿润向炎热干旱逐步演化。综合分析认为,尼玛盆地在始新世的气候变化在很大程度上是受西风环流和季风系统的共同影响。且西风环流和季风的强度变化与全球气候存在一定的关系。即全球变暖时,西风环流势力减弱,西风环流和残余洋水汽为高原中部提供的有效降水减少,气候相对干旱;而在全球降温时,西风环流和印度季风增强,残余洋水汽的叠加又为高原中部提供了充足的有效降水,气候湿润。

     

Palaeoecology and taxonomy of Pentoxylales from the Albian of Antarctica

Reproductive pentoxylalean material from the Albian Triton Point Formation, Fossil Bluff Group of Alexander Island, Antarctica is the youngest record of this group globally. Leaves are referred to Taeniopteris daintreei McCoy, ovulate reproductive organs to Carnoconites cranwelli Harris, and stem material to Pentoxylon sp. Occurring in leaf litter layers on palaeosol surfaces the sedimentology suggests that pentoxylalean plants grew upon areas of the floodplain distal to the river channel, where they covered the forest floor in a similar habit to modern brambles. The forest floor was shared with Equisetales and liverworts, an abundance of ferns [Cladophlebis Brongniart, Gleichenites Goeppert, Phyllopteroides Medwell, Sphenopteris (Brongniart) Sternberg], as well as angiosperms. Bennettitales, Ginkgoites Seward and Nilssonia Brongniart were rare within these communities, as were coniferous trees.     

塔里木盆地塔河地区下石炭统巴楚组沉积演化

以塔里木盆地加里东期和海西两期构造运动为背景,结合现有的岩心、露头、测井、录井和地震资料,对巴楚组可识别出早期的辫状河三角洲沉积,中期的潟湖沉积和盐湖沉积,以及晚期的咸化潟湖沉积。本文分别从横向上和纵向上对塔河地区巴楚组沉积演化进行深入分析;总结了巴楚组构造运动与沉积响应之间的关系,以期为该地区的下石炭统巴楚组的进一步勘探提供科学依据。     

滇中川街盆地中侏罗世弓鲛(软骨鱼类)化石新材料

云南禄丰县川街盆地中侏罗统产出弓鲛鱼类化石后甸弓鲛(Hybodus houtienensis Young)、新庄弓鲛(新种)(Hybodus xinzhuangensis Sun)、川街弓鲛(新种)(Hybodus chuanjieensis Sun)。后甸弓鲛(Hybodus houtienensis Young)是中国发现最早的弓鲛鱼类之一,正型标本为破碎的鳍棘,副型标本为一枚牙齿齿冠。依据在川街盆地相同层位发现的新化石材料,对后甸弓鲛副型标本进行了增补,补充了描述,建立了2个弓鲛新种:新庄弓鲛与川街弓鲛,丰富了"后甸弓鲛带"弓鲛类群,并讨论了弓鲛属的生物地层、生活的古环境和地理分布特征。     

珠江口盆地番禺低隆起轻质原油地球化学特征及其对比研究

珠江口盆地番禺低隆起轻质原油的密度小于0.83 g/cm3,饱和烃质量分数高(71%～93%),不含沥青质等.从原油族组成、轻烃特征、碳同位素、生物标记化合物等方面综合分析了原油的地球化学特征.轻质原油的姥鲛烷/植烷峰面积比值高(6.1～7.4),碳同位素较重(-27.09‰～-26.48‰)、重排甾烷相对含量较高、重排甾烷/规则甾烷峰面积比值为0.65～0.95,C304-甲基甾烷相对含量较低,双环倍半萜烷相对含量较高,双环倍半萜烷/五环三萜烷峰面积比值为3.33～18.09.研究表明轻质原油的成熟度较高(镜质体反射率Ro＞1.0%),原油母岩的沉积环境为弱氧化条件,母质以陆源高等植物输入为主,细菌和藻类也有少量贡献;运用轻烃参数,金刚烷化合物、生物标记化合物的相对含量和碳同位素值及系列指标进行的油油和油源对比研究表明,轻质原油具有相同母源和成因,油源可能主要为珠江口盆地白云凹陷渐新统恩平组煤系烃源岩.     

柴达木盆地昆特依地区晚更新世正构烷烃分布特征及其环境变迁

为探讨柴达木盆地晚更新世的环境变迁,同时为青藏高原隆升对气候变化的影响提供基础资料,对柴达木盆地昆特依地区ZK1404钻孔沉积物中的正构烷烃分布特征以及ASM¹⁴C测年数据进行了分析。结果显示,昆特依地区晚更新世沉积物的正构烷烃总体上呈现以高碳数为主的分布特征,多数样品以nC₂₇、nC₂₉为主峰,部分以nC₃₁为主峰,呈现出显著的奇碳优势。少数样品中低于nC₂₁的短链正构烷烃相对丰度较高,主要以nC₁₇、nC₂₀为主峰碳数,无明显的奇偶优势。根据正构烷烃分布特征、AMS¹⁴C测年数据、区域地质调查资料及沉积环境判断,柴达木盆地昆特依地区晚更新世（33600~26370a B.P.）气候环境以温凉干旱与温凉干旱偏湿交替出现为特征,与现代大陆性干旱荒漠气候截然不同。     

The age of the Cuddapah and Kurnool systems,southern India

In southern India the older Precambrian is overlain unconformably in the Cuddapah Basin by the Cuddapah and Kurnool Systems. The former is tilted and unmetamorphosed in the west but eastwards becomes strongly folded and metamorphosed. It contains lavas and sills, particularly in the lower two groups, is intruded by dolerites and at Chelima by diatremes of kimberlitic affinities related to those intruding the older gneisses west of the Cuddapah Basin in the Wajrakarur area. The Kurnool System lacks any igneous rocks; its basal conglomerate is diamondi‐ferous.

Rb‐Sr dating of lava samples from the lowest group of the Cuddapah System shows that the age of the base of the system may be as great as 1,700 m.y. Together with data for a granite which intrudes probable Cuddapah rocks near the disturbed eastern margin of the basin the data imply that the base is unlikely to be younger than 1,555 m.y. Metamorphism affected some lavas at about 1,360 m.y. The diatremes have two ages of intrusion, about 1,225 m.y. and 1,140 m.y., the latter being the age of the Majhgawan pipe near Panna in northern India. Pre‐Kurnool dolerites have an age of 980 ±110 m.y.

The lavas and dolerites show a range of initial ⁸⁷Sr/⁸⁶Rb ratios from about 0.704 to 0.708 and possibly 0.712.

The age data suggest that no simple correlation can be made with other Precambrian sequences in northern peninsular India. Deposition of the Cuddapah System appears to have started well before the start of the deposition of the Vindhyan System, while the Kurnool System is coeval with only part of the Upper Vindhyan. The data also suggest that present interpretations of the structural development of the Cuddapah Basin may need some revision.     

First Valanginian Polacanthus foxii (Dinosauria,Ankylosauria) from England,from the Lower Cretaceous of Bexhill,Sussex

A new partial skeleton of the armoured ornithischian dinosaur Polacanthus found in the Wadhurst Clay Formation (Valanginian stage) of Bexhill, Sussex is the oldest recorded occurrence of this taxon. Previous discoveries suggested that at least two armoured ornithischians occur in the Wealden succession: Polacanthus, which was mostly restricted to the Barremian, and Hylaeosaurus, which was recorded as present only in the Valanginian. The new discovery extends the stratigraphic range of Polacanthus into the Valanginian. Although these two taxa appear to be closely similar anatomically, their osteology now suggests they are not synonymous. The new specimen includes the first known jugal as well as a comparatively rare polacanthid plate/spine (splate) which probably comes from the shoulder (pectoral) area of these animals.     

Trace elements and their variation along seam profiles of certain coal seams of Middle and Upper Barakar formations (Lower Permian) in East Bokaro coalfield,district Hazaribagh,Bihar, India

Trace-element data are presented for the first time for any coal seam in India, across a full working section, based on systematically collected channel samples of coal, together with their maceral composition. The trace-element variation curves along the seam profile are presented together with group maceral compositions of Kargali Bottom, Kargali Top, Kargali, Kathara, Uchitdih, Jarangdih Bottom, Jarangdih, and Jarangdih Top seams, East Bokaro coalfield. The Kathara and Uchitdih seams have also been sampled at two other localities and lateral variation in data in their trace-element and maceral compositions is also evaluated.The East Bokaro coals have: Ba and Sr > 1000 ppm; Mn < 450 ppm; Zr < 400 ppm; Ni and V < 250 ppm; Cr < 185 ppm; La < 165 ppm; Cu, Nb, and B < 125 ppm; Pb, Co and Y < 75 ppm; Ga, Sn, Mo, In and Yb < 15 ppm; Ag 2 ppm; and Ge 7 ppm. Petrographically, the coals are dominant in vitrinite (33–97%), rare in exinite (<15%), and semifusinite (0.8–49%) is the dominant inertinite maceral, with variable mineral and shaly matter (11–30%), graphic representation of trace elements versus vitrinite, inertinite, and coal ash indicates the affinity of (a) vitrinite with Cu, Ni, Co, V, Ga and B; (b) inertinite with Nb and B; and (c) coal ash (mineral matter) with Pb, Cu, Ni, La, Mn and Y; Ba, Cr, Sr, Zr, Cu and Ni are of organic as well as inorganic origins.The trend of the variation patterns and average compositions of the different seams are shown to be distinct and different. The variation along the same profile is inferred to be different for different seams of the coalfield.Trace-element data for certain coals of seams from different coalfields in the Gondwana basins of India are presented. There is a wide difference for each of these basins with respect to certain elements. This is suggestive of the proportions of Cu, Ni, V, Y, Ba, Sr, Cr, B, Zr and Ag, characterizing the different Gondwana Basins.     

豫西地区下二叠统太原组遗迹组构及其沉积环境

豫西下二叠统太原组中发育丰富的遗迹化石,常见有Zoophycos,Taenidium,Thalassinoides,Teichichnus,Gordia,Nereites,Chondrites和Planolites等,部分灰岩层中还发育生物扰动构造。根据遗迹化石的形态、组成、产状、分布特征以及丰度、分异度、生物扰动程度的不同,在研究区太原组碳酸盐岩中共识别出5种遗迹组构,包括类型A--Gordia-Planolites遗迹组构、类型B--Rhizocorallium-Thalassinoides遗迹组构、类型C--Zoophycos-Taenidium遗迹组构、类型D--Zoophycos-Speckle burrow强生物扰动遗迹组构、类型E--Chondrites-Nereites遗迹组构。其中类型C根据Zoophycos在剖面上所展现的各种特征,又可细分为3种类型,即类型C-1,C-2和C-3。通过分析宿主岩的沉积特征,表明太原组碳酸盐岩中的遗迹组构主要分布于潟湖潮坪和台内浅滩(类型A)、正常天气浪基面之上的浅海上部或局限台地(类型B,类型C-1和类型C-2)、正常天气浪基面之下的开阔台地(类型C-3,类型D)和风暴浪基面之下的浅海下部或水动力条件类似的较闭塞的沉积环境中(类型E)。