The Biostratigraphy of Middle and Late Cambrian Faunas of Northern Victoria Land, Antarctica

Most of the material refers to northern Victoria Land and was collected over two summer seasons (1974-75 with NZARP and in 1981-82 as part of the International North Victoria Land Expedition which was supported by ANARE). As shown on the maps in the publications the area of collection is bounded by latitudes 71 to 73 degrees S and 162 to 166 degrees E. Altitude was generally between 1500 and 2500 metres. From the abstracts of some of the referenced papers:New evidence bearing on the age and correlation of the Cambrian-Ordovician Bowers Supergroup of northern Victoria Land is outlined. Constraints in the age range of the lower unity, the Sledgers Group are derived from a variety of fossils including a small assemblage of polymerid trilobites in a limestone clast from conglomerate; an age range within the middle Cambrian older than the late Middle Cambrian Boomerangian Stage is most probable. Clastic sedimentation infilling the Bowers depositional depression thus commenced in about the early Middle Cambrian, considerably later than the late Precambrian to Early Cambrian age previously inferred. Similarly, the basaltic volcanism represented by the Glasgow Formation is now known to be of Middle Cambrian age rather than Vendian to Early Cambrian. The conformably overlying Mariner Group is now well dated by trilobites and ranges from late Middle Cambrian (Undillan or Boomerangian) to Late Cambrian (late Idamean or early post-Idamean) in age. The youngest unit, the predominantly fluviatile Leap Year Group, contains a trace fossil assemblage consistent with a Late Cambrian to Ordovician age. The Bowers Supergroup, is thought to have formed part of a zone of Cambrian rifting, subsidence, rapid sedimentation and volcanism that extended through Western Tasmania, providing a link between the Antarctic and Australian segments of Gondwanaland in Cambrian time.New stratigraphical and palaeontological data from Early Palaeozoic Bowers Group of northern Victoria Land indicates that its depositional basin was probably closely linked with the Dundas Trough of western Tasmania. On the basis of these data, a revised reassembly of the Australo-Antarctic portion of Gondwanaland is proposed.54 trilobite taxa from 15 new localities in the Bowers Terrane of Northern Victoria Land, including the first fossils from Molar Formation, are described. The fossils indicate an age range from late Middle Cambrian (Boomerangian or older) to mid Late Cambrian (late Idamean). At Reilly Ridge, the Spurs Formation crops out in a number of fault-bounded slices; the new fossils indicate marked lateral facies contrasts between slices and suggest considerable lateral displacement along the bounding faults. At Houliston Glacier, trilobites of Mindyallan age in Molar Formation imply that the boundary between the Molar and Spurs Formations is strongly time transgressive. New specied described in this paper are Reillopleura braddocki gen. et sp. nov. and Notoaphelaspis horizontalis sp. nov. Faunal affinites are mainly with the Ellsworth Mountains (West Antarctica), western Queensland, and China.Middle Cambrian, or probably Middle Cambrian, trilobites were collected at six localities in the Heritage Range of the Ellsworth Mountains, including Yochelson Ridge, Drake Icefall area, Edson Hills, Liberty Hills (two locations), and Marble Hills. The total fauna includes 14 genera (2 new) and 32 species (5 new). Due to original preservation and/or deformation, a number of the forms are not assignable to specific taxa. The new taxa described herein are Peronopsis deons sp. nove., Pagetia edsonensis sp. nov., Sohopleura drakensis gen. et. sp nov., Pseudobergeronites spinosa gen. et sp. nov., and Blountia perplexa sp. nov. The trilobites were found in formations of the upper Heritage Group (springer Peak Formation, Drake Icefall Formation, and Liberty Hills Formation). The trilobite faunas described show affinities with faunas from northern Victoria Land (Antarctica), Tasmania, Queensland, China, Kazakhstan, and North America. All faunas are probably Middle Cambrian in age (Templetonian and Boomerangian on the Australian biochronological scale).

本数据集大部分资料源自北维多利亚地（northern Victoria Land），采集工作历经两个夏季科考季：1974-1975年依托新西兰南极研究计划（NZARP）开展，1981-1982年作为由澳大利亚国家南极考察队（ANARE）支持的国际北维多利亚地科考队的一部分完成。如出版物所载地图所示，采集区域的纬度范围为南纬71°至73°，经度范围为东经162°至166°，海拔普遍介于1500至2500米之间。据部分参考文献的摘要显示：本文概述了有关北维多利亚地寒武纪-奥陶纪鲍尔斯超群（Bowers Supergroup）年代与对比关系的新证据。下伏单元斯莱杰群（Sledgers Group）的年代范围约束可通过多种化石推导得出，其中包括来自砾岩灰岩岩块中的小型聚合三叶虫组合；其最可能的年代范围为中寒武世，且晚于中寒武世晚期的博默朗吉亚期（Boomerangian Stage）。因此，充填鲍尔斯沉积凹陷的碎屑沉积作用大约始于早中寒武世，远晚于此前推断的新元古代晚期至早寒武世年代。同理，以格拉斯组（Glasgow Formation）为代表的玄武质火山作用，现已确定其年代为中寒武世，而非埃迪卡拉纪至早寒武世。整合覆于其上的海员群（Mariner Group）现已通过三叶虫精确定年，其年代范围从中寒武世晚期（翁迪兰期或博默朗吉亚期）至晚寒武世晚期（伊达梅亚晚期或伊达梅亚早期后阶段）。最年轻的单元为以河流沉积为主的闰年群（Leap Year Group），其所含的遗迹化石组合与晚寒武世至奥陶纪的年代范围相符。鲍尔斯超群被认为是寒武纪裂谷、沉降、快速沉积与火山作用带的一部分，该带延伸至西塔斯马尼亚，为寒武纪时期冈瓦纳大陆（Gondwanaland）的南极与澳大利亚板块提供了连接纽带。来自北维多利亚地早古生代鲍尔斯群的新地层学与古生物学数据表明，其沉积盆地可能与西塔斯马尼亚的邓达斯海槽（Dundas Trough）紧密相关。基于上述数据，本文提出了冈瓦纳大陆澳南极区域的修正重建方案。本文描述了北维多利亚地鲍尔斯地体（Bowers Terrane）15个新采集点的54个三叶虫分类单元，其中包括摩尔组（Molar Formation）的首批化石。这些化石的年代范围从中寒武世晚期（博默朗吉亚期或更早）至晚寒武世中期（伊达梅亚晚期）。在赖利岭（Reilly Ridge），斯帕斯组（Spurs Formation）出露于多个受断层约束的岩片中；新化石表明岩片之间存在显著的侧向相差异，并暗示边界断层存在较大的侧向位移。在胡利斯顿冰川（Houliston Glacier），摩尔组产出的明迪阿兰期（Mindyallan）三叶虫表明，摩尔组与斯帕斯组的界限具有强烈的穿时性。本文描述的新物种包括雷利褶盾虫（Reillopleura braddocki）新属新种（gen. et sp. nov.）与水平诺托阿菲莱三叶虫（Notoaphelaspis horizontalis）新种（sp. nov.）。该动物群的亲缘关系主要与埃尔斯沃思山脉（西南极洲）、昆士兰州西部以及中国的动物群一致。在埃尔斯沃思山脉的遗产山脉（Heritage Range）的6个采集点中，发现了中寒武世（或疑似中寒武世）的三叶虫，采样点包括约赫尔逊岭、德雷克冰瀑区、埃德森山、自由山（2个点位）以及大理石山。该动物群总计包含14个属（2个新属）与32个种（5个新种）。由于原始保存状况和/或变形作用的影响，部分标本无法归入特定的分类单元。本文描述的新分类单元包括：德翁佩雷三叶虫（Peronopsis deons）新种、埃德森佩奇三叶虫（Pagetia edsonensis）新种、德雷克索褶盾虫（Sohopleura drakensis）新属新种、刺伪伯杰龙三叶虫（Pseudobergeronites spinosa）新属新种，以及困惑布朗特三叶虫（Blountia perplexa）新种。这些三叶虫发现于遗产群上部的地层中，包括施普林格峰组（Springer Peak Formation）、德雷克冰瀑组（Drake Icefall Formation）与自由山组（Liberty Hills Formation）。本文描述的三叶虫动物群与北维多利亚地（南极洲）、塔斯马尼亚、昆士兰州、中国、哈萨克斯坦以及北美的动物群具有亲缘关系。所有动物群的年代大概率为中寒武世（在澳大利亚生物年代学标尺上为坦普尔顿期与博默朗吉亚期）。