Planktic Foraminiferal Biostratigraphy of the Cretaceous Oceanic Red Beds in Kangmar, Southern Tibet, China
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Chuangde 形成的 planktic 有孔虫类(上面的白垩纪海洋的红床， CORB ) 是在 Tianbadong 节暴露了， Kangmar，南部的西藏第一被学习了为一为详细 biostratigraphy 详尽阐述详细说明了。一个富有、保存得很好的 planktic 有孔虫类从 Tianbadong 节和 Globotruncanita 的 Chuangde 形成被恢复 elevata， Globotruncana ventricosa， Radotruncana calcarata， Globotruncanella havanensis， Globotruncana aegyptiaca， Gansserina gansseri 和 Abathomphalus mayaroensis 地区被认出了。到到 Maastrichitian 的早 Campanian 的有孔虫目的集合点为东方北方 Tethyan 喜玛拉雅的亚带的 CORB 变老的 planktic，它也提供印度板的变的进步的更好的理解给北方和 Neotethyan 海洋的进化。Tianbadong 节的 Chuangde 形成的岩石层位学包括在登上继任观察的二个 lithological 序列：一个更低的单位(页岩成员) 主要紫色创作了(樱桃红，紫红) 有 interbedded siltstones 的页岩和硅质的岩石；并且上面的联合起来(石灰石成员) 使成杂色的石灰石。在 Tianbadong 节的 Chuangde 形成的阶层类似于在亚洲的北 Tethyan Himalaya 区域的另外的部分的 CORB (Gyangze， Sa'gya， Sangdanlin，北 Zanskar，等等) 。在学习的节(CORB ) 的 Chuangde 形成的石块内容北 Tethyan 喜玛拉雅的亚带和南部的 Tethyan 喜玛拉雅的亚带的上面的白垩纪为那些提供与带状配列计划的关联的一个工具。为迟了的白垩纪的 Paleogeographic 重建显示上面的白垩纪 Chuangde 形成(CORB ) 和在北 Zanskar 的 correlatable 阶层到 basinal 存款的斜坡是代表性的，它位于北 Tethyan 带。在 Spiti 和位于在对比的南部的 Tethyan 带的 Gamba 的 Correlatable 白垩纪阶层沿着 Tethyan 喜玛拉雅的被动边缘在架环境被扔。CORB 被 Fe (II )-enriched, 的氧化很可能形成分开了 oxic 的 chemocline 附近的缺氧的深海洋水海洋的表面从缺氧。Keywords:
Red beds
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Aptian
Biozone
Chemostratigraphy
Siliciclastic
Cenomanian
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Based on high resolution biostratigraphic analysis of planktic foraminifers, it is confirmed that the Bidart section (eastern margin of the Atlantic Ocean) represents a continuous Cretaceous–Paleogene (K-Pg) succession. Nevertheless, the foraminiferal species Plummerita hantkeninoides , regarded as a latest Maastrichtian marker species, is absent and Abathomphalus mayaroensis ranges to the top of the Maastrichtian (= K/Pg boundary). Pseudoguembelina hariaensis is present throughout the succession, and it is proposed herein to substitute Pl. hantkeninoides as the marker of the uppermost Maastrichtian. At least 53 out of 72 species became suddenly extinct at the K/Pg boundary, defined by the Ir anomaly (Bonte et al. 1984; Delacotte et al. 1982). The extinct species are represented by globotruncanids and large heterohelicids, characteristic of the tropical-subtropical deep photic sea water under the mesotrophic conditions of the Late Maastrichtian. The Lower Danian succession (the zones of Guembelitria cretacea , Parvularugoglobigerina eugubina , Parasubbotina pseudobulloides ) is less expanded than at El Kef (Tunisia) [the Global Stratotype Section and Point (GSSP) for the Cretaceous/Paleogene (K/Pg) boundary] or at Elles (Tunisia) [its auxiliary section].
Paleogene
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Marine transgression
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Chronostratigraphy
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The Upper Cretaceous Bolinxiala Formation,named by Guo Tie-ying et al.(1991) based on a type section at Bolin of Zanda,southwestern Tibet,mainly consists of marls and limestones.The basal Bolinxiala Formation consists of glauconitic limestones and conformably overlies the glauconitic quartze sandstones of the upper Gajie Formation.Planktonic foraminiferal fossil assemblages identified from the Bolinxiala Formation at Bolin,Zanda,southwestern Tibet,give an age of latest Albian to Maastrichitan.The fossil contents of the Bolinxiala Formation allow its correlation with successions across a platform-to-basin transect of the Late Cretaceous Tethyan Himalaya passive margin.The new planktic foraminiferal biostratigraphic data indicate that the Bolinxiala Formation in Zanda has a much longer duration than that of the Zongshan Formation.Therefore,the Bolinxiala Formaton should not be substituted by the Zongshan Formation.
Marl
Aptian
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Paleocene and Eocene marine sequences distributed in Rakhi Nala and Zinda Pir Anticline areas of the eastern part of the Sulaiman Range in Pakistan record the geological history and tectonic events during the last stage of collision between the Indian and Eurasian Plates and closure of the Tethyan Ocean. The Eocene sequences consist of siltstone and mudstone with some limestone intercalations, and are divided into the Shaheed Ghat, Baska and Kirthar Formations in ascending order. We studied the Eocene biostratigraphy of planktic foraminifers in this region to reveal the geological ages of the Eocene strata based on (international) correlation with standard tropical/subtropical zones. The planktic foraminiferal assemblages are composed of 78 species of 19 different genera, including many zonal markers of tropical to subtropical regions. We identified 8 biostratigraphic zones, Zone P7, Acarinina pentacamerata Partial Range Zone, Planorotalites palmerae Total Range Zone, A. soldadoensis Assemblage Zone, Zone P12, Zone P13, Orbulinoides beckmanni-Truncorotaloides rohri Interval Zone, and Truncorotaloides rohri-Turborotalia cerroazulensis cunialensis Interval Zone in ascending order. These zones correspond to Zones P7 to P15 of tropical/subtropical schemes. However, the upper part of Zone P10 to Zone P11 is not recognized because of an interval that is barren of planktic foraminifers in the Baska Formation.
The geological age of the Shaheed Ghat Formation is assigned to the Early Eocene through early Middle Eocene (Zones P7 to P10, 52.3~45.8 Ma). The Baska Formation is apparently equivalent to Zone P10 (early Middle Eocene), although its direct age is uncertain as it is barren of planktic foraminifers. The fossiliferous micritic limestone forming the lowermost part of the Kirthar Formation yielded recrystallized planktic foraminifers and calcareous nannoplankton indicating an early Middle Eocene age spanning calcareous nannoplankton Zones NP14 to NP15 (48.5~43.4 Ma), while the upper part of the Kirthar Formation ranges in age from middle Middle Eocene to early Late Eocene (Zones P12 to P15, 43.6~35.2 Ma). Hence the strata of the Kirthar Formation spans in age from early Middle Eocene through early Late Eocene based on recognition of the planktic foraminiferal Zones P10 to P15 (49~35.2 Ma).
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在东北突尼斯的 Fahdene 形成 outcropping 的更低的部分被远洋的序列代表并且由包括放散虫类的各类动物和 Allam 成员的器官富人的床的重要 siliciclastic 部分描绘了。Litho-biostratigraphic 分析基于 planktic 有孔虫类和 radiolaria 证明 Allam 成员的器官富人的床的那免职通过 Ticinella 报春属植物地区的更低的部分被限制到 Microhedbergella rischi 地区。诊断 radiolaria 从这些床恢复了的年龄被识别了抑制黑页岩免职的直接年龄。集合能与在年龄显示早 Albian 到早中间的 Albian 的放散虫类的各类动物 biochronozone U.A.1011 被相关。放散虫类的各类动物集合 U.A.10 biochronozone 的种类特征创作了(一。montisserei， D。gracilis ) 与属于 Costata 地区(U.A.9 Pseudoeucyrtis hanni 和 Thanarla pseudodecora ) 的放散虫类的各类动物 taxa 被联系，它能在爱奥尼亚的地区和 Vocontian 盆(法国的东南) 的 Paquier 水平与 Dercourt 成员一起被相关。Biostratigraphic 和丰富曲线分析表明了 cryptocephalic Nassellaria 和 Archaeodictyomitrae 的重要多样化，可能适应了描绘了 Aptian-Albian 转变的发育营养正常促进剂条件。生态的条件可能管理了许多大都会的 taxa 的 stratigraphic 范围(即， Pseudodictyomitrae lodogaensis ) 与 stratigraphic 分布相比，计划从另外的领域报导了。预定黑页岩免职由于本地 geodynamic 条件和 upwelling 水流分发是历时的。Allam 黑页岩是有被描绘由的海洋的缺氧的事件 OAE1b 的关联词在越过 Aptian-Albian 转变的地中海 Tethys 盆的 supraregionnally 器官富人的床普遍。
Radiolaria
Aptian
Siliciclastic
Micropaleontology
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Nannofossil biostratigraphy of the Lower Cretaceous Shadui Formation (Northern Tethyan Himalayas, Southern Tibet) Calcareous nannofossils of Aptian-Albian age were found in the basal part of the Shadui Formation, Northern Tethyan Himalayas, Southern Tibet. The predominantly shale strata are exposed near the northeastern tip of Yamdrock Tso Lake at the locality of Bangbu and they were previously considered to be of Late Cretaceous age. Occurrence of the nannofossil species Prediscosphaera columnata and Cribrosphaerella ehrenbergii indicates the Upper Aptian-Lower Albian Zone BC23. Nannofossil species of Late Albian, Cenomanian or younger Cretaceous age were not present in the studied part of the Shadui Formation. Nannofossils are badly preserved and hardly identifiable probably as a result of strong post mortem etching and dissolution during burial. The depositional setting of the Shadui Formation is interpreted as hemipelagic to pelagic. A horizon of dark shale in the lower part of the Shadui Formation may be stratigraphically correlated with ocean anoxic event OAE1b. The discovery of calcareous nannofossils at the Bangbu locality increases the stratigraphic precision in the correlation of Cretaceous strata between hemipelagic-pelagic facies and shelf depositional areas in the Tibetan Tethyan Himalayas.
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Cenomanian
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