老挝万象地区的侏罗系

为了解老挝万象含盐盆地的形成与演化历史,在老挝万象平原钾镁盐矿勘查项目中,对该地区进行了区域地质调查。老挝万象地区的侏罗系为一套夹少量碳酸盐岩的红色陆源碎屑沉积,由上到下可划分为班辛黑组、南舍组、南立组;该地层的介形类分属Gomphocythere-Darwinula组合、Darwinula sarytirmenensi-Darwinula magnca组合,叶肢介属滇南古渔乡叶肢介动物群,腹足类具中侏罗世陆生动物群特征;本区侏罗系为一套以湖泊沉积为主的河湖相沉积,构成一个完整的Ⅲ级层序,可划分出低水位体系域、湖侵体系域、凝缩期沉积及高水位体系域。这3个组的岩石地层、生物地层及年代地层特征,可与我国滇西地区的漾江组、花开左组相对比。     

中国南方海、陆相侏罗系的划分与对比

对自21世纪以来中国南方海、陆相侏罗系的研究进展进行了总结,依据地层发育的总体特征,将中国南方侏罗系划分为4个地层区和14个地层分区,文中着重介绍了中国南方海、陆相侏罗纪年代地层划分、底界界线层型及各统之间的界线生物标志和与全球年代地层的对比关系.此外,对全球年代与生物地层的研究进展也作了扼要介绍.     

四川大邑,崇州,汶川,都江堰毗邻地区的侏罗系

龙门山中、南段的四川大邑、崇州、汶川、都江堰毗邻地区的侏罗系发育良好,呈ＮＥ－ＳＷ走向。地层划分出白田坝组、千佛岩组、沙溪庙组、遂宁组、莲花口组以及新建五龙沟砾岩５个正式组和１个非正式群级岩石地层单元。首次总结了岩石组合特征及相变,讨论了侏罗纪以电子自旋共振（ＥＳＲ）为依据的年代地层划分,并简要叙述了白田坝期－千佛岩期冲积扇－湖相、沙溪庙期－遂宁期的河流相、莲花口期和五龙沟砾岩的洪积扇（冲积扇相）     

中国北部陆相侏罗系与英国海陆交互相侏罗系的对比研究：兼论中国北部 …

通过中国北部陆相侏罗系与英国苏格兰西北部海,陆交互相大河口群叶肢介组合的对比和义县组底部与叶肢介共存的孔子鸟与德国索尔霍芬灰岩始祖鸟的对比,为中国北部陆相侏罗系与海相侏罗系的对应关系提供了三条对比等时线,并为陆相侏罗系的对比与时代提可靠的生物依据。     

四川大邑—崇州地区的白垩、第三系

四川大邑、崇州地区的白垩、第三系发育良好 ,地层呈北东—南西走向。在《万家坪幅》区域地质调研期间 ,对该区的白垩系、第三系测制了多条剖面 ,划分出了天马山组、夹关组、灌口组、名山组及大邑砾岩等岩石地层单元 ,总结了它的岩石特征相变情况 ,讨论了白垩、第三纪地的地质时代及划分对比 ,简述了这一时期沉积环境的演变是由冲积扇到河、湖相的划分依据     

甘肃西部侏罗系的划分与对比

玉门市旱峡煤矿中间沟剖面是甘肃西部一条有代表性的侏罗纪地层剖面。通过对中间沟剖面的研究,分析了甘肃西部侏罗系划分与对比存在的争纷,提出了新的划分与对比方案,新命名了中间沟组,修改了原大山口群和博罗群的涵义。     

侏罗系、白垩系界线问题及对中国北方陆相界线的思考

侏罗系、白垩系间是显生宙唯一还没有定义系级GSSP的界线。生物演替在Thithonian期与Berriasian期之间不存在明显变化,很难找到可以进行全球对比的标志。作为中生代生物年代地层学主要划分依据的菊石类生物,亦受生物区系影响而难作为侏罗系、白垩系界线的标志。微体化石具有优势。近期,国际上趋于将瓮虫类Calpionella alpina带之底、钙质超微化石Nannoconus steinmannii minor和N.kamptneri minor二者的始现面作为侏罗系、白垩系界线,对应于极性带M19n.2n内部,年龄为145 Ma。国际地层划分与对比以海相为标准。中国侏罗系、白垩系以陆相地层发育为特征,与海相对比颇具难度。以陆相生物为标志的界线划分产生了地区性的生物年代地层格架,也形成了地方生物地层与国际年代地层对比的错位,导致中国陆相侏罗系、白垩系界线成为地学界争议的问题。本文认为,在综合考虑不同学科研究结果的同时,问题解决的实质是客观认识陆相生物对比的缺陷,结合考虑非生物的标准,如磁性地层、旋回地层和同位素测年的精度,获得超越相区的对比结果。基于陆相生物特点,着眼于宏观演化阶段来识别界线位置是问题解决的初期阶段。燕辽生物群与热河生物群是代表侏罗纪和白垩纪的两大生物演化类群,其间年龄可为土城子组顶部的139 Ma。这是为全方位研究而铺设的临时工作界线。今后将土城子组作为侏罗纪、白垩纪过渡地层而加大研究力度,有可能在该组顶部或其内部发现界线生物标志和同层位绝对年龄值,或许会使其向目前国际推荐年龄(145 Ma)更靠近一步;也不排除GSSP未定的国际侏罗系、白垩系界线年龄会向年轻方向变化,趋于139 Ma的Valanginian阶底界位置。     

冀中地区的侏罗系

冀中地区侏罗系为一套杂色含煤碎屑岩层系 ,自下而上发育有 Osmundacidites- Cyathidites- Gleicheniidites-Protoconiferus、L eiotriletes- Cycadopites- Quadraeculina- Classopollis及 Granulatisporites- L eiotriletes- Cyathidites- Cy-cadopites等 3个孢粉化石组合。冀中地区侏罗系岩性组成及化石组合特征与周边地区具有一定可对比性 ,但因其岩性具有明显的特殊性 ,故自下而上新建葛渔城组、杨村组和苏桥组。同时对冀中地区侏罗纪岩石地层系统的区域对比关系和地质时代进行了初步讨论。     

草湖地区侏罗系层序地层及沉积体系特征

基于测录井资料对比,结合区域构造演化特征,将草湖凹陷侏罗系划分为两个三级层序J-SQ1与J-SQ2。J-SQ1时期气候温暖潮湿,层序发育完整的上升半旋回和下降半旋回沉积,发育辫状河体系和湖泊体系;J-SQ2时期气候逐渐转为炎热半干旱,层序发育不完整,只发育上升半旋回沉积,主要由氧化型湖泊体系构成,发育滨浅湖砂滩、泥滩互层沉积。其中,J-SQ1早期辫状河河道砂体叠置厚度大,储层物性好,上覆中厚层湖相泥岩沉积,是本区有利的储集层段。     

黑龙江省绥滨、集贤地区的侏罗—白垩系界线地层

<正> 黑龙江省东部的绥滨、集贤、双鸭山等地是我国东部地区中生代含煤地层较为发育的地区,地层剖面连续,化石丰富。一一○勘探队在该地陆相含煤地层中及其下新发现的一套海相地层,采到丰富的动、植物化石(图1)。     

中国东南沿海晚白垩世长屿火山的活动过程与古环境意义SCIEI北大核心CSCD

火山是唯一能够直接反映地球深部存在岩浆的地球动力学现象,对于地球气候演变和宜居性具有重要影响。相比年轻火山,古老火山因其活动过程完整、且可能剥蚀出露多阶段火山喷发产物及岩浆通道、岩浆房等,从而为揭示火山岩浆系统演化和火山活动过程提供重要的研究窗口。本文选择中国东南沿海晚白垩世长屿破火山为研究对象,对其开展火山地质、岩石学、年代学及地球化学研究,以期揭示其火山活动历史及其对中国东南沿海白垩纪古环境的启示意义。长屿火山出露面积约100km^(2),呈近圆形分布,具有较厚的火山地层厚度(总厚度约570m),类似于破火山内的火山堆积特点。由早至晚三个喷发阶段形成的流纹质角砾凝灰岩都显示了典型的火山碎屑流相的特点,发育典型的条纹斑状结构,但表现出不同的晶屑、玻屑及岩屑含量以及熔结程度等岩相学特征,反映火山喷发从初始到高峰、再到减弱的过程,最后岩浆沿火山通道侵出形成流纹斑岩穹隆,标志着火山活动的结束。长屿火山的火山碎屑流式喷发伴随着快速的岩浆房塌陷,以及缺少普林尼式空落堆积,反映了火山活动发生在伸展的构造背景。系统的LA-ICP-MS锆石U-Pb年代学研究获得了不同阶段火山岩一致的形成年龄(97~96Ma),暗示它们具有较短的形成时限,是由同期火山岩浆活动先后喷发形成的。长屿火山岩高的SiO_(2)含量(67%~76%)以及分异的锆石微量元素地球化学特征,表明喷发岩浆来自晶粥提取的熔体,并有晶粥来源晶体的混入。此外,我们在长屿火山岩中发现了南洋杉型丝炭化木(贝壳杉型木属),暗示晚白垩世中国东南沿海地区可能为温暖湿润的亚热带山地气候环境,表明中国东南沿海白垩纪大规模火山活动,在古武夷山脉以东地区形成了地形高耸的海岸山脉。     

Structural geology of the Upper Cretaceous Chalk Central Mass, Isle of Wight, U.K.

Remapping the Chalk of the Central Chalk Mass of the Isle of Wight between Carisbrooke (Newport), Calbourne and Shalcombe, including the Bowcombe Valley, has identified a complex series of tectonic ‘rolls’ and ‘flats’ in a region that has been interpreted to be a relay ramp between the Needles and the Sandown faults. A major new WNW trending fault at Cheverton throws the Chalk down by >50 m to the SW in a 80-100 m wide zone of faulting within which some chalk blocks have near vertical dips. The fault location and trend closely follows the edge of the Cranbourne-Fordingbridge High and could also reflect, for the first time, the surface expression of part of the Needles Fault, a major inversion reverse fault. Located along this fault zone deep Quaternary weathering of the Chalk and Quaternary gravel deposits are present. The trend of the Cheverton Fault brings it towards Gotten Leaze where a groundwater pumping station is located and groundwater springs regularly cause flooding on the Brighstone-Calbourne Road. Analyses of the jointing in the Chalk show that stratabound fracture patterns typical of the Chalk formations elsewhere in Southern England are present in the Central Mass. In addition, there are numerous small faults along which valleys have formed. Tectonic structure and lithology have had a profound influence on the geomorphology and groundwater flow in the Chalk in the Central Mass.     

藏东南地区早白垩世的安第斯型弧火

首次在藏东南发现一套早白垩世的陆相火山岩, 称雅则火山岩, 全岩 Ｒｂ Ｓｒ 等时线年龄１０７４ Ｍａ。其主体是高钾的安山岩系, 以强亏损高场强元素、富集大离子亲石元素和轻稀土、 Ｌａ／ Ｎｂ 比值 ＞ ２ 为特征, 属活动大陆边缘火山岩; 微量元素等指示它产出在安第斯型陆缘环境。其南延即滇西南的腾冲 铁窑山 大松坡消减型花岗岩带 （１００～１１２ Ｍａ）, 反映新特提斯洋在早白垩世有过一次重要的消减过程;晚白垩世的花岗岩具不同的岩石组合和成矿特征,记录了消减后的陆 弧碰撞事件。     

Revision of the Conchostracan Genus Tenuestheria from the Upper Cretaceous Lanxi Formation in Zhejiang and Its Biostratigraphic Significance in Southeast China

The diagnosis of the conchostracan genus Tenuestheria from the Lanxi Formation in Jinhua, Zhejiang Province in Southeast China is revised following an examination of the type species under a scanning electron microscope, which revealed some morphological features on the carapace that had not been recognized previously. The importance of the Tenuestheria Fauna is considered in the context of correlation of six Turonian–Santonian formations in this region of China. The value of the Cenomanian Nemestheria and Turonian Linhaiella faunas in correlating the underlying early Late Cretaceous formations is also noted.     

对西藏岗巴上白垩统的新认识

在前人研究的基础上对岗巴地区上白垩统的划分做了厘定 ,进一步建立了晚白垩世的 1 2个浮游有孔虫化石带。根据岩性特征及化石带的研究 ,上白垩统被划分为赛诺曼期至土仑早期的冷青热组 ;土仑中期至三冬期的岗巴村口组和康潘期至马斯特里赫特期的宗山组。该区赛诺曼期与土仑期的界线位于冷青热组上部 ,以 H elvetoglobotruncana praehelvetica的初现为标志。     

Integrated biostratigraphic and sequence stratigraphic framework for Upper Cretaceous strata of the eastern Gulf Coastal Plain, USA

Upper Cretaceous (Santonian-Maastrichtian stages) strata of the eastern US Gulf Coastal Plain represent a relatively complete section of marine to nonmarine mixed siliciclastic and carbonate sediments. This section includes three depositional sequences which display characteristic systems tracts and distinct physical defining surfaces. The marine lithofacies are rich in calcareous nannoplankton and planktonic foraminifera which can be used for biostratigraphic zonation. Integration of this zonation with the lithostratigraphy and sequence stratigraphy of these strata results in a framework that can be used for local and regional intrabasin correlation and potentially for global interbasin correlation. Only the synchronous maximum flooding surfaces of these depositional sequences, however, have chronostratigraphic significance. The sequence boundaries and initial flooding surfaces are diachronous, and their use for correlation can produce conflicting results. The availability of high resolution biostratigraphy is critical for global correlation of depositional sequences.     

Two–stage Cretaceous Exhumation of Hengshan Complex in Hunan Province,SE China: Constraints Arising from ~(40)Ar–~(39)Ar Geochronology and Cretaceous Tectonic Implications

The Hengshan complex is located in the central part of SE China, which underwent rapid tectonic uplift in the Cretaceous just like many other complexes on the continent. (40)~Ar–(39)~Ar geochronological data from the Hengshan complex suggest that two episodes of crustal cooling/extension took place in this part of the continent during the Cretaceous time. The first stage of exhumation was active during ca. 136–125 Ma, with a cooling rate of 10 °C/Ma. The second stage of exhumation happened at ca. 98–93 Ma, with a cooling rate of 10 °C/Ma. Considering the folding in the Lower Cretaceous sedimentary rocks and the regional unconformity underneath the Upper Cretaceous red beds, it is believed that the Cretaceous crustal extension in SE China was interrupted by a compressional event. The reversion to extension, shortly after this middle Cretaceous compression, led to the rapid cooling/exhumation of the Hengshan complex at ca. 98–93 Ma. The Cretaceous tectonic processes in the hinterland of SE China could be controlled by interactions between the continental margin and the Paleo–pacific plate.     

闽西武夷山建宁—泰宁地区白垩纪火山-沉积序列:对华南东部晚中生代构造演化的制约

闽西武夷山建宁—泰宁地区发育2套白垩纪火山-沉积序列,构成2个火山-沉积旋回,每套序列由下部火山岩和上部沉积岩地层组成.锆石U-Pb年代学和地球化学分析显示,早期中酸性火山岩喷发时代为早白垩世141～135 Ma,具有陆缘火山弧的地球化学亲缘性,并富集Hf同位素(-20.2～1.9);而晚期火山岩活动集中在早、晚白垩世...     

大兴安岭中北部晚侏罗世-早白垩世地层新认识

根据大兴安岭中北部地区晚侏罗世火山岩正常沉积夹层中所含叶肢介化石的研究成果和同位素年龄新资料，认为大兴安岭北部西坡被归入白音高老组中的“含Eosestheria的酸性、酸碱性火山碎屑岩和熔岩”不是白音高老组，应归入龙江组，层位与辽西义县组对比。大兴安岭主脊火山岩（满克头鄂博组、玛尼吐组、白音高老组）从南到北是同期火山活动作用的结果，不存在“穿时”现象，形成于晚侏罗世早中期，层位与冀北大北沟组对比。