The new Ordovician stage standard as applied to the stratigraphic units of the western Altai–Sayan Folded Area

Data are provided on the new Ordovician stage standard of the International Stratigraphic Chart: Tremadocian, Floian, Dapingian, Darriwilian, Sandbian, Katian, and Hirnantian. Graptolite and conodont zonal and infrazonal successions are used for a precise estimation of the chrono- stratigraphic position of the boundaries of the previous and newly proposed Ordovician regional stratigraphic units (horizons) in the western Altai–Sayan Folded Area. The chronostratigraphic position of the boundaries of most of the Ordovician formations showing a wide lateral distribution in southern Siberia has been described in detail in terms of the new stage standard of the General Stratigraphic Scale of Russia.     

Regional tectonic and megadepositional cycles of the Paleozoic of northwestern and central Saudi Arabia

The Paleozoic succession of the Greater Arabian basin is severely affected by series of major tectonic and climatic events which have caused major stratigraphic breaks and pronounce facies change. The major tectonic movements have resulted in dividing the succession into pronounced megatectonic and depositional cycles. In more tectonically active areas, the succession is less preserved and boundaries between the cycles are more complicated due to longer periods of erosion by later movements and/or nondeposition. Minor stratigraphic breaks within the megacycles subdivide the cycles into smaller subcycles. Following the stabilization of the Arabian–Nubian shield, the Gondwana shelf went through a gentle uplift and tilt probably related to the Assyniyc tectonic movements and thick siliciclastics of the Saq and Qasim Formations were deposited. During Late Caradocian and following the deposition of the Qasim Formation, the area went through a gentle uplift and tilt probably related to the Taconic tectonic movements. Thick succession of the Qasim and Saq Formations were eroded and deep paleovalleys incised in the two formations and underlying basement. The movements were followed by drop of sea level due to glaciation events. Glacial and periglacial deposits of the Zarqa and/or Sarah Formations filled paleovalleys and rest on older units from Ordovician to Precambrian. The third main event occurred during Late Silurian where the preexisting successions, mainly on paleohighs, were affected by tectonic movements synchronous with the Acadian tectonic phase of the Caledonian tectonic movements. The Early Devonian Tawil Formation unconformably rests on eroded Silurian and Late Ordovician deposits of the Sharawra, Qusayba (Qusaiba), and Sarah Formations in the Qusayba Depression in central Arabia. The forth main event is a regional movement contemporaneous with the Hercynian tectonic movement which has reached its maximum phase in the Late Carboniferous. Earlier successions from Carboniferous to Precambrian were affected and the Permo-Carboniferous Shajra Formation unconformably rests on all underlying Paleozoic rock units toward the central Arabia arch and other paleohighs. The Shajra rests on the Devonian Jawbah (Jubah), Jawf (Jauf) and Tawil formations, the Silurian Sharawra, Qusayba, and Uqlah formations, the Ordovician Zarqa/Sarah, and Qasim formations, the Cambro-Ordovician Saq Formation, and finally rests on Precambrian Basement complex in Central Arabia. The tectonic movements played important role in shaping the structural framework of Arabia. The Paleozoic succession included source, reservoir, and seal rocks. Oil and gas have been discovered in sandstone and limestone reservoirs in these rocks in several oilfields in the basin.     

江西省震旦纪地层清理综述及问题探讨

通过《江西省地层多重划分对比研究》项目的工作,确立了我省正式岩石地层单位200个,其中震旦纪19个,包括群级单位2个,组级单位17个,本文总结了震旦纪地层研究工作新进展和主要成果,并对存在的主要问题进行探讨。     

浙江常山黄泥塘水库剖面的生物地层学

为有效保护我国第一个"金钉子"——浙江常山黄泥塘剖面的同时,又能较好地满足一般性补充研究的需求和普通大众对"金钉子"剖面化石的兴趣爱好,剖面保护单位在"金钉子"剖面附近水库边开辟了一条新剖面。该剖面地层序列完整,出露新鲜,自下而上包括印渚埠组上部、宁国组和胡乐组下部。剖面化石丰富,保存精美,除丰富的笔石外,还含有一些腕足动物、三叶虫、叶虾类和粪化石,自下而上可识别出Corymbograptus deflexus带、Azygograptus suecicus带、Exigraptus clavus带、Undulograptus austrodentatus带和Acrograptus ellesae带等笔石带。整个剖面的岩石和笔石序列与黄泥塘"金钉子"剖面一致,能进行良好对比,可作为"金钉子"剖面的一般性替代剖面,从而为进一步开展达瑞威尔阶的后层型研究提供了新的证据来源。     

东秦岭中部奥陶系-志留系界线地层及腕足动物群

东秦岭中部晚奥陶世和早志留世地层分布较广,化石较丰富,尤其是腕足类,分为寺岗组、石燕河组、刘家坡组和张湾组。曾庆銮等(1993)根据腕足类及其群落的更替,把石燕河组和刘家坡组归於早志留世,因而引起较大争论。本文据岩性将寺岗组和石燕河组分别改称为石燕河组下段和上段,并据腕足类化石认为石燕河组和刘家坡组应归於晚奥陶世、张湾组为早志留世;另据上述地层生物群落的特征及群落的更替,认为从石燕河组到刘家坡组,以及刘家坡组至张湾组恰好反映了全球冰期引起的晚奥陶世海退和早志留世冰期结束引起的海侵,故本区奥陶系-志留系界线宜划在刘家坡组和张湾组之间。     

Ordovician successions in southern-central Xizang (Tibet), China—Refining the stratigraphy of the Himalayan and Lhasa terranes

The Ordovician stratigraphy of southern-central Xizang (Tibet) has been revised based on new conodont data recovered from 43 samples in four stratigraphic units and their integration with existing nautiloid and graptolite data. The Histiodella holodentata and Pygodus serra biozones have been identified respectively in the Alai and Jiaqu formations of the Chiatsun Group exposed near Alai village in Nyalam County within the Himalayan terrane, and the Yangtzeplacognathus foliaceus Subbiozone (lower part of the Pygodus serra Biozone) in the Sangqu Formation exposed at the Guyu section within Zayu County in the Lhasa terrane. Recognition of these biozones has increased the precision of correlation of the middle-upper Darriwilian strata in the region. Regional reassessment of the Ordovician stratigraphy permitted by new biostratigraphic data has allowed revised definitions for the Chiatsun and Keerduo groups and the Sangqu and Xainza formations. The Chiatsun Group is defined herein to include three lithologically distinctive formations in descending order, the Jiaqu, the Alai and the Adang formations. The stratigraphic age for the Jiaqu and Alai formations in the type area ranges from the middle Darriwilian (Histiodella holodentata Biozone) to middle Katian (Hamarodus brevirameus Biozone), but the age of the Adang Formation remains less certain.     

东川、滇中地区中元古代地层格架

东川、滇中地区是上扬子陆块出露元古代地层最广泛的地区,但露头又断续分布在不同的地点.由于缺乏古生物及年龄资料,在不同地区多以岩性进行地层划分与对比,而出现了"正层"与"倒层"观点之分歧.通过对东川及滇中地区地层中所夹的火山岩年龄测试及重要界面的观察与研究,发现东川地区黑山组凝灰岩中锆石U-PbSHRIMP年龄为1503...     

大兴安岭北段龙江盆地中生代火山岩 激光全熔40Ar/39Ar测年

现龙江组与光华组作为大兴安岭北段龙江盆地中的主要地层单元,二者的时代与含义仍存有争议.通过对二者的建组剖面进行野外调查,采用最新的激光全熔40Ar/39Ar测年对剖面及周边的7件火山岩样品进行了精细的定年研究,结果显示,现龙江工组年龄为125.1Ma±1.5Ma～117.0Ma±9.0Ma;光华组为125.4Ma±1.8Ma～121.6Ma±1.4Ma;甘河组为123.1Ma±1.1Ma～82.0Ma±4.0Ma.本区晚白垩世火山岩信息揭示龙江盆地可能发育大兴安岭北段晚白垩世孤山镇期火山岩.野外地质调查结果表明,现龙江组和光华组具有基本相同的火山喷发旋回,结合2个岩组相同的年龄结果,建议合并现龙江组与光华组,恢复为原龙江组,而不再使用从原龙江组上部划分出的光华组.从火山-沉积地层出露特征分析,龙江盆地与其北部的大杨树盆地具有一定的相似性,2个盆地具有相同的地质演化历史,表明龙江盆地可能是潜在的油气调查新区.     

中国北部新第三纪红层划分的岩石学标志及其意义

广布于我国北方的新第三纪红层多由中新统保德组和上新统静乐组组成，这两个组岩性相似，一般情况下难以区分。地层结构详细研究显示，两组中钙质结核赋存方式相差很大，前者呈层状产出，后者为星散状，地层形成时古气候条件的差别是导致该现象的主要原因。由于大气状况具有区域性特点，因而这一地层划分标志具有特定的地质意义及在大面积内具实用的价值     

奥陶系研究百余年:从英国标准到国际标准

英国学者Sedgwick、Murchison和Lapworth等早在19世纪便对奥陶系作出了先驱性的研究,包括创建了奥陶系。但百年来各国主要都集中于地区性的奥陶系研究,并建立了地区性的序列和标准,这在事实上一直都把英国的奥陶系划分作为国际间的对比标准。近三十年来,随着国际奥陶系分会不断推进各国奥陶系的研究工作,并在2007年完成了奥陶系三统七阶的全部全球层型剖面和点位(GSSP)的研究,建立了全球标准。为了便于运用,建议将奥陶系的三统七阶分为20个间隔段,以利于洲际对比,并把地区性的统与阶准确地对比到国际标准上去。同时附上与年代地层划分相一致的奥陶系全球碳同位素的变化曲线。     

Seismic stratigraphy based chronostratigraphy (SSBC) of the Serbian Banat region of the Pannonian Basin

Seismic stratigraphy based chronostratigraphic (SSBC) analysis of the Serbian Banat region allows the delineation of the spatial and stratigraphic relationships of the generally regressive and shallowing upward Neogene depositional fill of a tectonically unstable central portion of the Pannonian Basin. When geometrically restored in time and space, the sediment dispersal directions, sediment source directions, types of sedimentation breaks and the tectonic events influencing basin evolution can be delineated. For such an analysis the time-transgressive lithostratigraphic units used in the neighbouring Hungarian part of the Pannonian Basin are conveniently introduced based upon their characteristic seismic facies and constrained borehole log records as mappable seismic stratigraphic sequence units, termed “seismic operational sequences”. The respective Neogene stage and operational sequence equivalents (Hungarian lithostratigraphic units or formations) are the Middle Miocene (Badenian, Sarmatian), Upper Miocene-Lower Pliocene (Pannonian-Endrod and Szolnok Formations; Pontian- Algyo and Ujfalu Formations and Lower Pliocene- Zagyva Formation) and Upper Pliocene-Quaternary (Nagyalfold Formation). SSBC analysis greatly assists in the geological constraint or “geovalidation” of interpreted seismic stratigraphic relationships and provides potentially critical insight into stratigraphic and structural problems of non-unique interpretations. In the specific case, using such an approach on previously unpublished regional seismic lines, SSBC analysis reveals that the Banat region has undergone structural inversion. This may be related to changes in local stress directions along strike slip faults, which initiated in earliest Late Miocene (Endrod Formation), culminating in the reverse tilting and incipient shortening of the western graben. Therefore during the time interval that the Badenian through Endrod sediments were deposited in the graben, autocyclic progradation initiated from the Kikinda Szeged High in the East followed by Szolnok, Algyo, Ujfalu and younger units prograding from the West as the central high uplifted relative to the graben. Such tectonic inversion has substantial hydrocarbon potential implications for exploration in the region.     

鄂尔多斯盆地奥陶系层序地层格架

通过大量露头、钻井与地震层序地层学综合分析,建立了全盆地奥陶系层序地层格架。研究提出了“碳酸盐岩层序地层划分与对比五要素”分析方法。应用该分析方法在奥陶系识别出3个二级层序界面、6个三级层序界面,将奥陶系划分为2个二级层序和8个三级层序。盆地不同构造环境形成不同的层序地层格架:在盆地西部窄大陆边缘北部奥陶系发育层序 Osq3-层序Osq7五套地层,持续时间从早奥陶世弗洛阶到晚奥陶世桑比阶末,南部发育层序Osq1-层序Osq7七套地层,持续时间从早奥陶世特马道克阶到晚奥陶世桑比阶末,总体上西部地层西厚东薄,南北向条带状展布,向伊盟隆起-庆阳古隆起上超覆尖灭;在盆地南部宽大陆边缘奥陶系发育盆地所发现的8个层序,持续时间从早奥陶世弗洛阶到晚奥陶世凯特阶早期,地层南厚北薄,向庆阳古隆起上超覆尖灭;在盆地中东部台内洼陷奥陶系仅发育层序Osq3-层序Osq5 TST,以盆地东部洼陷东侧最厚向伊盟隆起-庆阳古隆起上超覆尖灭;盆地北部伊盟古隆起、西南部庆阳古隆起主体一直处于隆起剥蚀状态,二者的鞍部仅发育Osq4 TST层序,表明盆地西部的祁连海槽与盆地东部的华北海在中奥陶世晚期有过短暂连通。     

西藏吉隆沟石炭纪沉积相与层序地层特征

西藏北喜马拉雅地层分区石炭纪仅发育杜内期一维宪期沉积，时间跨度约30Ma，含亚里组与纳兴组两个岩石地层单位。据吉隆沟地层的特征可识别出潮坪、三角洲及浅海陆棚等沉积相。由层序界面性质与地层结构特征划分为2个Ⅰ型层序、7个Ⅱ型层序、2个层序组，属1个超层序。多数层序仅由海侵体系域(TST)和高水位体系域(HST)两部分组成。     

Materials for refining the stratigraphic chart of the Berriasian–Lower Aptian in West Siberia with regard to the clinoform subsurface structure

In light of the new clinoform model of the Neocomian, introduced at the last stratigraphic meeting, it is suggested to distinguish clinoform units instead of formations in the clinoform zone. Formations (12 in number) remain only west of the central part of the Neocomian basin (east-dipping clinoforms). In the eastern and southeastern parts of the basin, all the formations beyond the clinoform zone, which consist mostly of continental sediments, should be united into the Ust’-Taz Group.     

Geologic framework for the coal-bearing rocks of the Central Appalachian Basin

Coal production has been an important economic factor in the Central Appalachian Basin. However, regional stratigraphic and structural relationships of the coal-bearing rocks of the basin have been poorly understood due to numerous separate nomenclatural schemes employed by various states. In order to estimate coal resources and understand mechanisms controlling the distribution of coal within the basin, a reliable geologic framework is necessary. Seven detailed cross sections across the Central Appalachian Basin were constructed in order to examine the stratigraphic and structural framework of the coal-bearing rocks in the basin. The cross sections were based on more than 1000 oil and gas well logs, measured sections, and borehole information from Kentucky, Ohio, Tennessee, Virginia and West Virginia.The cross sections revealed three main points discussed here: southeast thickening of the Pennsylvanian strata, uncomfortable northwestward onlapping relationship of Lower Pennsylvanian strata over underlying Lower Pennsylvanian and Mississippian strata and regional continuity of beds. The cross sections, geologic mapping, coal-resource studies, extensive new highway exposures and the occurrence of tonstein beds indicate that many coal beds and marine strata are laterally extensive, albeit locally variable across the basin. Certain quartzose sandstone bodies are also extensive over large areas of the basin.Existing stratigraphic nomenclature schemes obscured the geologic framework of the basin, so a new unified nomenclature scheme was devised to better describe stratigraphic features of the basin. The new stratigraphic nomenclature, now only formalized for Kentucky, was based on key stratigraphic units that proved to be extensive across the basin. Lower and Middle Pennsylvanian rocks are now recognized as the Breathitt Group (the Breathitt Formation was elevated to group rank). The Breathitt Group was subdivided into eight coal-bearing formations by relatively thick marine strata, and, in the lower part of the Breathitt Group, by quartzose sandstone formations. The new coal-bearing units are formally ranked as formations and, in ascending order, are the Pocahontas, Bottom Creek, Alvy Creek, Grundy, Pikeville, Hyden, Four Corners and Princess Formations. The quartzose sandstone units are also formally ranked as formations and are, in ascending order, the Warren Point, Sewanee, Bee Rock and Corbin Sandstones. The sandstone formations were previously recognized units in some states, but have been extended (formally in Kentucky) across the basin. The key stratigraphic marine units are formally ranked as members, and are, in ascending order, the Betsie Shale Member, the Kendrick Shale Member, Magoffin Member and Stoney Fork Member.     

鄂尔多斯盆地东部奥陶系风化壳岩溶古地貌特征及综合地质模型

密切结合勘探实际,以钻井、测井等地质资料为主要依据,以鄂尔多斯盆地东部奥陶系风化壳为对象,以多学科的地质理论与技术方法为指导,结合盆地构造演化,通过对奥陶系不整合侵蚀面上下地层组合情况的深入分析,把印模法与残厚法结果有机结合,深入探讨了奥陶系风化壳古地貌恢复的方法思路及其古地貌发育特征,探索了古地貌恢复的新方法--综合法,建立了解释和恢复古地貌单元属性的综合地质模型。研究结果表明：盆地东部奥陶系侵蚀不整合面上下的地层组合可以分别被划分为上薄下薄、上厚下厚、上厚下薄、上薄下厚4种基本型式以及上次厚下次薄、上次薄下次薄、上次薄下次厚、上次厚下次厚等8种子模型;相应的古地貌解释包括了岩溶高地、岩溶斜坡、岩溶盆地3个二级古地貌单元以及残丘、台地、残台、阶坪、沟谷、浅洼、深洼等11个三级古地貌单元。岩溶高地出现于研究区西南角,分布局限;岩溶斜坡占据了研究区的大部分,其主力地貌单元为斜坡台地与斜坡阶坪;岩溶盆地位于研究区东部,其主力地貌单元为盆地浅洼。     

论宁国组和胡乐组

<正> 宁国组和胡乐组系许杰(1934)研究皖南宁国县胡乐地区奥陶系时建立的二个地层单位宁国页岩和胡乐页岩沿革而来。宁国页岩下部为“各种颜色之泥质页岩(下部作绿色,中部暗兰色,顶部棕黄色),厚约一百一十米”,产 Didymograptus hirundo,D. abnormis等对笔石、四笔石、叶笔石、雕笔石化石。上部“为淡黄色、柔软之泥质页岩,计厚三十一米”,笔石丰富,有 Amplexograptus confertus, Didymograptus acutidus,D. ellesae,     

Lithostratigraphy of the Cretaceous Strata of West James Ross Island,Antarctica

As a result of recent field work, a new lithostratigraphic group is defined on the west coast of James Ross Island, Antarctica. Characterised by comparatively coarse-grained sediments, the Gustav Group is 2300 m thick and has an approximate age range of Barremian-Santonian. Four formations are recognised within the group (the Lagrelius Point, Kotick Point, Whisky Bay and Hidden Lake Formations), and of these, the Whisky Bay Formation is further subdivided into six local members. Type sections are erected for each of these stratigraphic units and representative lithologies and faunas described.     

藏南康马地区石炭系及其下伏变质构造地层序列

西藏康马地区位于拉轨岗日构造带南缘中部。前人对该地区的康马穹窿及周围地层进行了大量研究,但长期以来对该区石炭系及以下变质构造地层的层序及时代认识不清,致使拉轨岗日构造带前石炭纪的地质演化史成为空白。根据1∶25万江孜县幅、亚东县幅区域地质调查工作取得的地层学资料及古生物、岩石组合特征,对康马附近石炭系及其以下地层进行了重新厘定。厘定后的地层单元分别为前奥陶系郎巴群（POl）、奥陶系则果群（Oz）、下石炭统雇孜组（C₁g）。下石炭统雇孜组（C₁g）与上覆早二叠世破林浦组（P₁p）之间为伸展不整合接触,与奥陶系则果群（Oz）之间为伸展拆离断层接触,前奥陶系郎巴组（POl）与奥陶系则果群（Oz）之间为伸展不整合接触,与下伏康马岩体为伸展拆离断层接触。     

塔中地区中—上奥陶统内波内潮汐沉积与油气勘探

现代海底普遍发育由内波、内潮汐引起的深水牵引流,内波、内潮汐不仅可形成各种小规模、分散的深水牵引流沉积,而且还可建造千米级的大型沉积物波。在古代地层记录中已发现各种厘米级的内波、内潮汐沉积单元,但尚未发现内波成因的大型沉积物波。通过对塔中地区中—上奥陶统碎屑岩段岩心观察和地震剖面的系统分析,发现了该岩段内由内波和内潮汐作用形成的各种牵引流沉积构造单元。已识别出4种内波、内潮汐沉积微相类型及5种基本垂向沉积层序,同时还在研究区中一上奥陶统陆坡相中识别出了内波成因的大型沉积物波。这些内波、内潮汐沉积具有较好的油气潜能,是该区中—上奥陶统潜在的油气勘探新领域。