龙门山北段观雾山组地层时代分布、沉积充填及其古地理意义

自四川盆地西北部(川西北)泥盆系观雾山组油气勘探取得重要进展以来,观雾山组的沉积储层研究受到了广泛重视。然而,由于观雾山组地层划分方案的变动和地层的穿时性,导致目前对观雾山组的时代分布和充填过程认识不清,从而影响了沉积古地理格局的恢复。本文以四川广元西北乡、潜溪河剖面泥盆系观雾山组牙形石生物地层研究为基础,结合区域古生物地层资料,认为江油马角坝以北的观雾山组绝大多数沉积于晚泥盆世早—中弗拉期,且地层沉积时间自南西向北东逐渐变晚。龙门山北段观雾山组具有自西向东、自南向北地层厚度减薄和地层时代变新的特征,表明来自扬子地台西部的古特提斯洋海水向东侵入龙门山地区,因地形差异和渐进式海侵形成了自南西向北东的超覆沉积。由于岩相分异,超覆沉积形成的观雾山组与金宝石组在区域上既表现为上下叠置关系,也表现为同期异相的相变关系。该研究不仅对约束川西北地区观雾山组地层时代提供了可靠的古生物证据,而且对认识龙门山地区泥盆系的充填过程、沉积古地理格局均具有重要意义。     

Cretaceous Environments of Afghanistan:A Synthesis Based on Selected Sections

The Cretaceous of Afghanistan is marked by great facies diversity. The evolution of Cretaceous basins is part of a complex accretionary history involving three distinct tectonic units namely the Asian (Russian) Block separated from the Indian plate by a rather well defined transcurrent fault (Chaman-Nuski). The southwestern component is representedby the Iran-Afghanistan plate. The Lower Cretaceous of the Asian Block is represented by the Red-Grit Series which isconformable to the underlying Upper Jurassic sequences. The transition is marked by evaporitic facies dominated by salt,gypsum and marl deposits. In south Afghanistan volcanic rocks occur at Farah, with the emplacement of plutonics inwest-central Afghanistan. The Upper Cretaceous of north Afghanistan is marked by richly fossiliferous, lime stone-dominated sequences. The Upper Cretaceous of southern Afghanistan is marked by strong ophiolitic magrmatism.     

塔里木盆地亚科瑞克剖面奥陶系牙形石生物地层初步研究

塔里木盆地西北缘乌什县东南亚科瑞克剖面奥陶系发育，并且该剖面也是塔里木盆地上奥陶统沉积最为齐全的露头剖面之一，尤其是上奥陶统的中—上部发育了许多重要的牙形石属种。本文通过对剖面上灰岩层样品的系统采集和牙形石分析鉴定，将该剖面的奥陶系分为4个牙形石组合和2个牙形石带。自下而上依次为：Serratognathus diversus - Bergstroemognathus extensus 组合 , Protopanderodus calceatus - Periodon aculeatus 组合 ,A phelognathus sp. - Tasmanognathus sp. 组合, Belodina confluens- Phragmodus undatus 组合 , Yaoxianog-nathus neimengguensis 带和 A phelognathus pyramidalis带。其中，上奥陶统上部牙形石的重要属种A. pyramida-lis、A. politus、Y. yaoxianensis 和 A. neimengguensis以及上奥陶统上部的A．pyramidalis带与Y．neimengguensis带是首次在柯坪地层分区发现。这些发现初步解决了塔里木盆地覆盖区与露头区上奥陶统不能进行精细生物地层对比的问题。     

第三纪年代地层研究和中国第三纪年代地层表

主要介绍国际上第三纪年代地层和年代学研究最新简况 ,显示几个重要的年代地层表或年代表 ,并报道全国地层委员会 1999年 12月断代专业组工作会议关于建立中国年代地层表中第三纪年代地层构架讨论的初步方案。     

柴达木盆地昆2井古近系下干柴沟组上、下段分界探讨

青海油田和中国石油大学（北京）合作,在柴达木盆地昆2井井深5120～5140 m发现南星介化石带。通过对比柴西地区和柴北缘地区南星介化石带的发现层位,并将该化石带顶界在地震剖面上进行标定追索,认为南星介（Austrocypris）是柴达木盆地下干柴沟组下段上部的标准化石。从发现南星介化石并标定有T4反射界面的冷科1井（或深88井）开始,沿地震测线向昆2井进行追索,经时深转换,将昆2井5040 m处标定为下干柴沟组上段与下段的分界。两井之间T4（下干柴沟组上、下段分界）、南星介化石带顶界和T5 （下干柴沟组底）呈3条平行线,表明其得到闭合验证,下干柴沟组上、下段的分界划分合理。因此,生物地层学与地震地层学相结合,可以有效地对比柴达木盆地陆相新生界红色碎屑岩区的地层。     

Sequence and isotope stratigraphy of Late Triassic distal periplatform limestones from the Northern Calcareous Alps (Kälberstein Quarry, Berchtesgaden Hallstatt Zone)

Received: 24 September 1998 / Accepted: 14 November 1999     

Reply to discussion of Jamaican cenozoic ichnology: review and prospectus: (v. 50, p. 364–382)

Mitchell and Ramsook comment on the lithostratigraphic assignment of Jamaican Cenozoic ichnofossils discussed in Donovan et al. They argue that the Paleogene Richmond Formation should be subdivided to produce a ‘Moore Town formation’ in eastern Jamaica, but the latter remains undefined as a lithostratigraphic unit and no new lithostratigraphic evidence is produced to support their supposition. Further, their use of a flawed table of trace fossil distributions does not support their thesis. The distribution of trace fossils in the White Limestone Group presented by Donovan et al. follows the lithostratigraphic scheme that was current at the time that the research was originally undertaken in the early 2000s. Yet, whatever lithostratigraphic scheme is utilised for the island, it is apparent that the more accurate data is provided by the biostratigraphy of the larger benthic foraminifers. Copyright © 2015 John Wiley & Sons, Ltd.     

Calcareous nannofossil biostratigraphic study of forearc basin sediments: Lower to Upper Cretaceous Budden Canyon Formation (Great Valley Group), northern California,USA

The results of a calcareous nannofossil biostratigraphic investigation of the North Fork Cottonwood Creek section of the Budden Canyon Formation (BCF; Hauterivian–Turonian) in northern California are summarized using the Boreal – cosmopolitan Boreal Nannofossil Biostratigraphy (BC) – Upper Cretaceous Nannofossil Biostratigraphy (UC) nannofossil zonal schemes of Bown et al. and Burnett et al. Sixteen intervals, ranging from the BC15 to UC8 zones, were established in the section. Combined biostratigraphic and magnetostratigraphic studies suggest a Hauterivian to mid‐Turonian age for the studied sequence. The Hauterivian–Barremian, Barremian–Aptian, Aptian–Albian, Albian–Cenomanian, and Cenomanian–Turonian stage boundaries were delineated near the top of the Ogo Member, below the Huling Sandstone Member, within the upper Chickabally Member, in the upper portion of the Bald Hills Member and within the Gas Point Member, respectively. Unconformities probably exist at the base of the Huling Sandstone Member and the upper part of the upper Chickabally Member. The nannofossil assemblage in the North Fork Cottonwood Creek suggests that the study area was under the influence of cold‐water conditions during the Barremian to Lower Aptian interval, shifting to tropical/warm‐water conditions during the Albian to Turonian interval as a result of the mid‐Cretaceous global warming. Although oceanic anoxic events have not yet been reported in the BCF, preliminary total organic carbon, along with nannofossil data, suggest the presence of the global Cenomanian–Turonian boundary oceanic anoxic event 2.     

贵州安顺长兴阶顶部三叶虫化石

三叶虫是二叠纪末生物集群灭绝中消失的生物门类之一,但是关于该门类生物化石在中国消失的确切层位未见报道。贵州安顺新民剖面大隆组顶部的三叶虫化石Pseudophillipsia sp.产于火山成因的黏土岩之炭质泥岩夹层中,相邻的泥灰岩结核中产牙形石化石Clarkina meishanensis。该黏土岩及炭质泥岩夹层可以与浙江长兴煤山D剖面的第25层对比,这说明三叶虫延续到了主灭绝事件层位,对研究二叠纪末生物集群灭绝的原因具有一定的意义。