Late Viséan–Serpukhovian foraminiferans and calcareous algae from the Adarouch region (central Morocco), North Africa

Three Upper Viséan to Serpukhovian limestone formations from the Adarouch region (central Morocco), North Africa, have been dated precisely using foraminiferans and calcareous algae. The lower and middle part of the oldest formation, the Tizra Formation (Fm), is assigned to the latest Asbian (upper Cf6γ Subzone), and its upper part to the Early Brigantian (lower Cf6δ Subzone). The topmost beds of this formation are assigned to the Late Brigantian (upper Cf6δ Subzone). The lower part of the succeeding Mouarhaz Fm is also assigned to the Late Brigantian (upper Cf6δ Subzone). The Akerchi Fm is younger than the other formations within the region, ranging from the latest Brigantian (uppermost Cf6δ Subzone) up to the Serpukhovian (E₁–E₂). The base of the Serpukhovian (Pendleian Substage, E₁) is repositioned, to coincide with the appearance of a suite of foraminiferans including Archaediscus at tenuis stage, Endothyranopsis plana, Eostaffella pseudostruvei, Loeblichia ukrainica, Loeblichia aff. minima and Biseriella? sp. 1. The upper Serpukhovian (Arnsbergian Substage, E₂) is marked by the first appearance of Eostaffellina ex. gr. paraprotvae and Globoomphalotis aff. pseudosamarica. The biostratigraphical scheme used for the reassessment of the foraminiferal zones and subzones in the Adarouch area closely compares with that for the British succession in northern England (Pennine Region), where the stratotypes of the Upper Viséan (Asbian and Brigantian) and Early Serpukhovian (Pendleian) substages are located. Thus, a succession equivalent to an interval from the Melmerby Scar Limestone to the Great (or Little) Limestone is recognized. These assemblages are also compared to other foraminiferal zones proposed in other regions of Morocco. Several foraminiferans have been identified that are proposed as potential Serpukhovian markers for other basins in Western Europe, and compared to sequences in Russia and the Donets Basin, Ukraine. Copyright © 2008 John Wiley & Sons, Ltd.     

Early Cretaceous radiolarians of the Amur River lower stream area (Russia Far East) and their tectonic significance

The results of lithological-biostratigraphic study of volcanogenic–chert rocks developed on the left side of the Machtovaya River, a right tributary of the Amur River, are given. The composition, structure, and age of these strata and the rocks constituting the Kiselevka–Manoma accretionary complex are different, which indicates their different tectonic origins.     

冀北张家口组、大北沟组的岩石地层学、生物地层学特征及其在东北亚地层划分对比中的意义

冀北张家口组、大北沟组及内蒙古相当地层的岩石地层、生物地层的综合对比研究表明：大北沟组与典型的张家口盆地的张家口组上部相当。大北沟组可以区分出一个Nestoria pissovi叶肢介组合和Ambonella lepida－Jibeilimnadia ovata亚组合、Keratestheria gigantean－Abrestheria rotunda亚组合;介形类可以区分出Luanpingella－Torinina－Eoparacypris组合和Luanpingella postacuta亚组合、Torinina obesa亚组合。生物组合、亚组合的识别为区域地层的划分、对比树立了标准和提供了有效手段。     

Middle Permian Seamount from Xiahe Area, Gansu Province, Northwest China: Zircon U-Pb Age, Biostratigraphy and Tectonic Implications

The well-preserved seamount buildups are documented from the northwestern Qinling (秦岭) orogenic belts, Northwest China. The study sections are located in the Ganjia (甘加) area of the Xiahe (夏河) County, Gansu (甘肃) Province. The dark basalt and overlying massive reef carbonate characterize the Xiahe seamount buildup. Basalts are dominated by the olivine type of rocks and bear distinct porphyritic textures, and fumarole and amygdaloidal structures. The basaits are dominated by SiO2(up to 48.49 wt.%-52.29 wt.%) followed by (Na2O+ K2O) (3.80 wt.%-4.96 wt.%) and TiO2 (2.04 wt.%-2.52 wt.%). They are featured by considerably high content of Ti. The tholeilteseries rocks dominate the basalts, while calc-alkali-series rocks are also present. The REE of the basalts shows the LREE-enrichment type with distinct positive Eu abnormal. The trace elements of the basalts are characterized by the lack of P and high content of Ti. These geochemical signals suggest that the Xiahe basalts were formed in an ocean-island setting. The LA ICP-MS zircon U-Pb age of the basalts is 267.6±5 Ma, which is reinforced by the presnce of the fusuHnid Neoschwagerina Zone of the Wordian (Middle Permian) in the limestone interbeds of the basalts. Integration of petrological and geochemical studies of seamount basaits and lateral correlation of seamount buildups reveals that the Qinling-qilian-Kunlun orogenic belts were probably the archipelagtc oceans during the Permian.     

澳大利亚寒武系生物地层研究新进展(英文)

澳大利亚寒武系集中分布在一南北向分布的从澳大利亚的北部、中部直到南澳大利亚克拉通地块上,少量寒武纪地层分布在新南威尔士、维多利亚和塔斯马尼亚。寒武系的底在中澳大利亚的Amadeus盆地出露得最好。下寒武统(大致相当于纽芬兰统和第二统)在澳大利亚北部大多数是不含化石的火山岩,而在澳大利亚中部和南澳大利亚的盆地中,其中最有名的是南澳大利亚的Arrowie和Stansbury盆地则是各种含化石的巨厚沉积序列。澳大利亚的下寒武统没有分阶方案,尽管在生物地层研究上最近取得很大进展,现在可以利用疑源类、遗迹化石、古杯类、三叶虫、腕足类、软体动物和其他小壳化石进行化石带的划分。很长一段时间内澳大利亚中部和北部的Ord-ian阶被认为是中寒武世最早期的,现在证明它可能相当于第二统的全部或者一部分;含化石的中寒武统和芙蓉统(或上寒武统)在Georgina盆地东部发育非常完整,在中澳大利亚、新南威尔士、维多利亚和塔斯马尼亚也可见到,都可以划分到阶。芙蓉统的底大致与Idamean阶的底相当。化石带的建立主要综合考虑球接子三叶虫、多节类三叶虫,自Iverian期晚期起再加上牙形类化石。寒武系的顶大致相当于Warendan阶的底,相关地层在Georgina盆地东部发育得很好。     

湖北兴山寒武系覃家庙群底部三叶虫化石的地层学意义

三峡地区覃家庙群以一套缺乏化石的薄层白云岩沉积为特征。新近在湖北兴山古洞口剖面覃家庙群底部发现Kaotaia gedongensis Yuan & Zhao,Kunmingaspis yunnanensis Chang,Chittidilla sp.等三叶虫。依据三叶虫生物地层学对比结果,结合研究剖面与覃家庙群标准剖面和参考剖面岩石地层学对比,认为三峡地区覃家庙群为跨传统下、中寒武统的地层单元。     

北美西部陆相白垩系-古近系界线孢粉学特征简介——兼评中国东部白垩系-古近系界线研究

已经报道的北美西部陆相白垩系-古近系界线剖面已达近百处,这些剖面分布在阿拉斯加南部向南经加拿大直到美国南部的新墨西哥州北部的广大北美西部内陆地区,其中很多属迄今所知全球很好的陆相白垩系-古近系界线剖面。这些剖面常有标志性的界线黏土,并伴有其他地球化学、生物地层学特征。因为这些剖面所在地当时都在湿润或半干旱地区内,有利于生物化石,特别是孢粉化石的保存,易于开展孢粉学研究。经过近四十年不懈努力,孢粉学已经成为北美精确确定陆相白垩系-古近系界线最重要的、也是迄今为止所知最为有效的古生物学工具。孢粉植物群在界线上下特征差别显著,容易区分。界线之下含有大量主要繁盛于白垩纪的被子植物花粉,而在临近界线时则突然消失或仅零星出现,界线附近则以一层孢子异常丰富层为古近系底部特征。进入古近纪之后,虽然被子植物花粉有所恢复,但是繁盛于白垩纪的成分却很少出现。北美和新西兰、日本白垩系-古近系界线附近在沉积岩和孢粉学方面的相似性表明这一事件可能是全球性事件。简要回顾和讨论了我国与孢粉学相关的几个热点地区陆相白垩系-古近系界线的研究概况,我国东北及江苏北部和北美西部大部分地区白垩系-古近系界线附近的孢粉植物群及其沉积环境比较类似,在苏北到东北地区范围内首次发现陆相白垩系-古近系界线地层的可能性比其他地区大。     

全球维宪阶与谢尔普霍夫阶界线层的生物地层研究进展及展望

牙形刺、有孔虫和菊石是全球维宪阶与谢尔普霍夫阶界线层生物地层研究的重要化石门类。该界线定义及其候选层型剖面目前均未正式确立。详细介绍并讨论以牙形刺或有孔虫作为界线定义的可能方案 ,指出潜在的候选层型剖面存在于南乌拉尔的 Verkhnyaya Kardailovka、北美犹太州中西部的 Chainm an组等 ,我国具有潜在研究价值的剖面有广西忻城里苗剖面、贵州水城滥坝老街水库剖面和罗甸纳水剖面     

东海陆架盆地台北坳陷月桂峰组生物地层及古环境

月桂峰组分布于台北坳陷西带,上覆灵峰组、下伏石门潭组,由灰黑色泥岩、砂岩组成。在微体古生物和地球化学微量元素详细分析的基础上,确立它属古近纪古新世沉积,推测可能为古新世早期,该地层相当于苏北盆地阜宁组一段。月桂峰组所含孢粉、藻类化石组合及地球化学微量元素特征表明月桂峰组当时的沉积环境以淡水湖相为主,局部时期(晚期)可能演变成海陆交互相,或者受到海水的影响。     

High-resolution magnetostratigraphy and micropalaeontology across the J/K boundary strata at Brodno near ilina, western Slovakia: summary of results

This study summarizes the final results of magnetostratigraphic and micropalaeontological investigations of the Tithonian/Berriasian boundary (J/K) limestones at the locality of Brodno near ilina, Western Carpathians, West Slovakia. The aim is to prepare the background for correlation of a Late Tithonian and Early Berriasian biostratigraphic zonation with global magnetoevents (manifested in detailed magnetostratigraphic profiles) between the Tethyan realm and other regions, particularly the Boreal and Pacific realms. Suitable physical properties of the limestones studied, a favourable geological setting and rich microfossil assemblages (calpionellids) at Brodno (magnetozones M21r to M18r) allowed a systematic collection of new data on the original synoptic section, which now has the character of a high-resolution profile across the J/K boundary. Two reverse subzones detected within magnetozones M20n and M19n are named ‘Kysuca Subzone’ and ‘Brodno Subzone’, respectively. Both can be correlated with analogous subzones in the M-sequence of marine anomalies. Their existence can also be confirmed in the Bosso Valley section in Umbria, central Italy. A detailed study of the interval between magnetozones M20n and M17r in the Bosso Valley profile is presently in its final stage. Both magnetostratigraphic profiles, from the Brodno and Bosso Valley localities, were thoroughly investigated in the intervals close to the J/K boundary and are still unique among continent-based profiles in the detection and precise definition of both reverse subzones within M20n and M19n. Samples collected from the boundary strata of the reverse Kysuca Subzone at Brodno indicated a transition from N (R) to R (N) polarity of the Earth's palaeomagnetic field within a time interval of c. ±5 ka. Limestone samples (total number N=368) were subjected to progressive thermal demagnetization in 10–12 thermal fields and to subsequent multi-component analysis of remanence. The C-component, as the carrier of palaeomagnetic directions, was determined in the temperature interval of 300° to 540°, or possibly 580°C. Magnetomineralogical analyses of pilot samples and unblocking temperatures determined for all samples showed that magnetite is the carrier of remanent magnetization. The positions of the individual events of calpionellid stratigraphy relative to the global magnetic polarity timescale are precisely defined. The base of the Calpionella Standard Zone, which is considered a provisional J/K boundary indicator in ammonite-free sections in the Tethyan realm, lies within magnetozone M19n at the level of 35% of its local thickness. None of the boundaries in the calpionellid zonation coincides precisely with any of those in the palaeomagnetic zonation, but the first appearance ofCalpionella grandalpina , indicating the base of the Intermedia Subzone, lies in close proximity to the base of magnetozone M19r.