A restudy of Oryctocephalus indicus (Reed, 1910)

Restudy on morphology of Oryctocephalus indicus (Reed, 1910), based on specimens from Guizhou, China and Nevada USA, suggests that the subspecies regarded previously as Oryctocephalus indicus indicus (Reed, 1910), O. indicus latus Zhao et Yuan 2002, and O. indicus kobayashi Saito, 1934, are synonymous, and Oryctocephalus americanus Sundberg et McCollum, 2003 is a similar form of O. indicus. Oryctocephalus indicus is rediagnosed as having a glabella that is subconical in outline and tapering forward slightly; a thorax that comprises 12 segments, and a small pygidium that bears 2?3 axial rings with a terminal piece and a postaxial ridge. Oryctocephalus indicus is widely distributed in eastern Guizhou and ranges through a great interval of Kaili Formation. Its first appearance is almost identical with these events of trilobite extinction-recovery occurring at the end of the Early Cambrian, the alternation of acritach assemblages, the change of trace elements (REE) and stable isotopes (carbon) at the Wuliu-Zengjiaya section. As one of the key forms for defining the traditional Lower - Middle Cambrian boundary (the base of Cambrian Series 3 and Stage 5 in the new Cambrian chronstratigraphic standard), O. indicus has received detailed study and has more advantages than other species such as Ovatoryctocara granulata Tchernysheva, 1962 or Arthricocephalus chauveaui Bergeron, 1899.     

A restudy of Oryctocephalus indicus (Reed, 1910)

Restudy on morphology of Oryctocephalus indicus (Reed, 1910), based on specimens from Guizhou, China and Nevada USA, suggests that the subspecies regarded previously as Oryctocephalus indicus indicus (Reed, 1910), O. indicus latus Zhao et Yuan 2002, and O. indicus kobayashi Saito, 1934, are synonymous, and Oryctocephalus americanus Sundberg et McCollum, 2003 is a similar form of O. indicus. Oryctocephalus indicus is rediagnosed as having a glabella that is subconical in outline and tapering forward slightly; a thorax that comprises 12 segments, and a small pygidium that bears 2?3 axial rings with a terminal piece and a postaxial ridge. Oryctocephalus indicus is widely distributed in eastern Guizhou and ranges through a great interval of Kaili Formation. Its first appearance is almost identical with these events of trilobite extinction-recovery occurring at the end of the Early Cambrian, the alternation of acritach assemblages, the change of trace elements (REE) and stable isotopes (carbon) at the Wuliu-Zengjiaya section. As one of the key forms for defining the traditional Lower - Middle Cambrian boundary (the base of Cambrian Series 3 and Stage 5 in the new Cambrian chronstratigraphic standard), O. indicus has received detailed study and has more advantages than other species such as Ovatoryctocara granulata Tchernysheva, 1962 or Arthricocephalus chauveaui Bergeron, 1899.     

Proposal and prospects for the global Lower-Middle Cambrian boundary

In recent years paleontologists have been working on the global stratotype section and standard point (GSSP) for the Lower-Middle Cambrian boundary in North America, China, Morocco, Spain and Russia. Continually, they suggest the potential first appearance datum (FAD) of the Middle Cambrian, such as Oryctocephalus indicus, Ovatoryctocara granulata, Acadoparadoxides mureroensis, Hupeolenus and Arthricocephalus chauveaui as being relevant to the potential stratotype section for the Lower-Middle Cambrian boundary. There are only a few trilobites distributed widely enough in the Early to Middle Cambrian connection, so virtually no trilobite(s) can act as the FAD for the global Middle Cambrian. The easily identified Oryctocephalus indicus is widely distributed in three realms of the global Cambrian. Its first appearance position is linked to the extinction of old species coevolution of new ones. It appears to be a comparatively good FAD of Middle Cambrian. The continuous and unbroken Wuliu section (Balang, Taijiang County, Guizhou Province, China) includes O. indicus and co-occurs with many benthic and nektonic trilobites. The evolution of acritarchs in the section, the changed characteristics of trace elements (REE and C isotopes) are generally consistent with the evolution of trilobites both above and below the boundary. Strata above the boundary yield the famous Kaili Biota. The Wuliu section is easily accessible from a main highway.     

The Balang Fauna―A new early Cambrian Fauna from Kaili City, Guizhou Province

In April 2004, Wu Yishan, a teacher from Kaili No. 4 Middle School, took his students to Wenglingtang to con-duct popular science activities. They found fossils of trilo-bites and eocrinoids in gray and gray-greenish silty shale, and calcareous, silty mudrock in the upper part of the lower Cambrian Balang Formation. In May 2004, we were invited to investigate the new discovery. Through several field investigations, we measured the stratigraphic section and collected numerous trilobite and…     

Discovery of sponge body fossils from the late Meishucunian (Cambrian) at Jinsha, Guizhou, south China

Here we report discovery of a sponge body fossil Triticispongia sp. from the base of lower Cambrian Niutitang Formation at Jinsha, Guizhou. Stratigraphically, the fossil horizon is located below Ni-Mo ore layer with the Niutitang Biota above, and is equivalent to the late Meishucunian. The species is global in shape with skeletons composed of stauractins and monaxons. Triticispongia sp. reported here may be the earliest sponge body fossils of Cambrian, which provides new information for understanding early evolution and radiation of sponge animals.     

A Chengjiang-type fossil assemblage from the Hongjingshao Formation （Cambrian Stage 3） at Chenggong,Kunming, Yunnan

A new Chengjiang-type fossil assemblage is reported herein from the lower part of the Hongjingshao Formation at Xiazhuang village of Chenggong,Kunming,Yunnan.The fossil assemblage,named as Xiazhuang fossil assemblage,yields predominantly soft-bodied fossils,including arthropods,brachiopods,priapulids,lobopods and some problematic taxa,with arthropods being the most dominant group.Preservation and composition of the fossil assemblage are very similar to the typical Chengjiang biota,which is preserved in the middle Yu’anshan Formation in the large area of eastern Yunnan.The associated trilobites demonstrate that the soft-bodied fossil assemblage belongs to the late Qiongzhusian in age(Stage 3,Cambrian),suggesting that the Hongjingshao Formation is probably a diachronous lithostratigraphic unit ranging from the upper Qiongzhusian to the lower Canglangpuan stages in eastern Yunnan.The fossil assemblage from the Xiazhuang area fills up the missing link between the typical older Chengjiang biota and the younger Malong and Guanshan biotas,making eastern Yunnan a unique area in the world to reveal the early evolutionary history of animals and palaeocommunity dynamics during the‘‘Cambrian explosion’’.     

Affinities and functional morphology of the Middle Cambrian ornamented tubules from West Hunan, China

Problematic phosphatic tubular microfossils with ornamented sculptures are documented to exist in limestones of the upper Middle Cambrian Huaqiao Formation at the Paibi section and the Wangcun section in West Hunan, China. Two morphological patterns, including Ornamented Tube Form I and Ornamented Tube Form II are described. Based on the analysis of the preservation, wall structure and composition of the fossils, it is deduced that these ornamented tubes may represent carapace spines of some Cambrian arthropods with phosphatic carapaces, such as bradoriid crustaceans. Analysis of functional morphology indicates that the sclerites may rather be considered of a defensive than grasping function on the original organism body.     

Isotopic evolution of the terminal Neoproterozoic and early Cambrian carbon cycle on the northern Yangtze Platform, South China

Profound geotectonic, climatic and biological changes occur during the terminal Neoproterozoic and its transition into the early Cambrian. These are reflected in temporal variations of the chemical and isotopic composition of seawater. We are studying a sequence of sedimentary rocks at the Shatan section, northern Yangtze Platform, Sichuan Province of China. This succession comprises, in ascending stratigraphic order, predominantly calcareous sediments of the Sinian upper Dengying Formation and black shales of the lower Cambrian Guojiaba Formation (time equivalent of Niutitang Fm.). Paleoenvironmental setting represents shallow-water shelf deposits. The objective of our study is to provide temporal records for the isotopic compositions of organic and carbonate carbon throughout this time interval. Organic carbon isotope values display a range between -35.8‰ and -30.1‰ with clear stratigraphic variations. Carbonate carbon isotope data vary between -3.5‰ and +0.5‰. These secular variations are interpreted to reflect perturbations of the global carbon cycle, specifically changes in the fractional burial of organic carbon. However, local conditions have further affected the isotopic signals.     

Growth of the Huoersuosi anticline （north Tianshan Mountains） by limb rotation since the late Miocene

The Huoerguosi anticline, located in the north Tianshan Mountains piedmont fold-and-thrust belt, is a trending east-west fault-related fold. In the cross section along the Jingou River, its south limb is composed of the pre-growth strata of the Anjihaihe （E2.3a）, the Shawan （（E3-N1）s）, the Taxihe （N1t） and the lower part of the Dushanzi （N2d） Formations, trending east-west and dipping to south 55°, and the growth strata of the upper part of the Dushanzi （N2d） and Xiyu （（N2-Q1）x） Formations, dips of which decrease from 55° at the base of the growth strata to 47° at the bottom of the Xiyu （（N2-Q1）x） Formation to -0° at the top of the Xiyu （（N2-Q1）x） Formation. The strata at the north limb of the anticline are vertical or over-turned, and are cut by the breakthrough thrusts to result in the drag fold. In the depth, the anticline is symmetric, and its core comprises the Cretaceous and the Jurassic coal-bearing beds. In the seismic profile, the seismic reflectors of pre-growth strata at the south limb of the anticline dip to south constantly, and ones of the growth strata fan southward, whose dips decrease upward. The geometry of the south limb growth strata outcropped along the Jingou River valley and the deep structure of the anticline shown in the seismic profile indicate that the Huoerguosi anticline is a detachment fold anticline growing by limb rotation. Based on the growth model and magnetostratigraphic age, during the growing process of the Huoerguosi anticline, the average shortening rate absorbed by the south limb is -0.46 mm/a, and the average uplifting rate of the anticline is -0.86 mm/a which exceeds the average deposition rate, which is in accordance with the fact that the top of the anticline is intensely eroded. Considering symmetric geometry of the Huoerguosi anticline and ignoring the breakthrough thrusts, the shortening of the whole anticline should be more than -0.92 mm/a, doubling the shortening rate determined from the growth at the south limb.     

A new section of Kaili Formation (Cambrian) and a biostratigraphic study of the boundary interval across the undefined Cambrian Series 2 and Series 3 at Jianshan, Jianhe County,China with a discussion of global correlation based on the first appearance datum of Oryctocephalus indicus(Reed,1910)

A trilobite biostratigraphic study of a new section of the Kaili Formation at Jianshan,Chuandong Village,Jianhe County,Guizhou is reported.Additional occurrences of key species associated with the Ovatoryctocara granulata-Bathynotus holopygus Zone and the overlying Oryctocephalus indicus Zone that were originally defined from the trilobite assemblages at the Wuliu-Zengjiayan section of the Kaili are reported from this new section.The first appearance datum (FAD) of Oryctocephalus indicus occurs at the 44.52 m above the base of the unit.Based on study of abundant specimens (n = 800) from the Kaili Formation,we argue that Oryctocephalus indicus is a widespread taxon with a global distribution.O.Reticulatus (Lermontova,1940) from the middle part of the Kounamkites Zone of the Amganian Stage in the Molodo River region of Siberia and O.Americanus (Sundberg and McCollum,2003) from Nevada,North America are similar to representatives of O.Indicus which occur in the O.Indicus Zone of the Kaili Formation.O.Reticulatus and O.Americanus are here synonymized with O.Indicus (Reed,1910).This study strengthens the Wuliu-Zengjiayan section of the Kaili Formation as a candidate section for a Global Stratotype for the base of the unnamed Cambrian Series 3.     

A restudy of Oryctocephalus indicus (Reed,1910)

Since both Chinese[1]and American Palaeontolo-gists[2]proposed separately to mark the beginning ofthe Middle Cambrian based on the first appearancedatum (FAD) ofOryctocephalus indicus[3]in thesame year ,the suggestion has been considered seri-ously and adoptedfrequently[4—18].The InternationalSubcommission on Cambrian Stratigraphy (ISCS) hasorganized the Working Group,chaired by L.B. Mc-Collum,to select candidate sections that bear poten-tial to become a GSSPfor the traditional Lowe…     

贵州剑河巴水崖、镇远朱砂凯里组研究--八郎潜在的国际中、下寒武统层型剖面的辅助剖面研究

贵州剑河县巴水崖和镇远县朱砂凯里组剖面中下部都有Oryctocephalus indicus的产出，说明Oryctocephalus indicus的分布具有普遍性。两个剖面中、下寒武统界线的划分和潜在的八郎鸟溜剖面中、下寒武统界线候选层型剖面的划分基本一致，可作为潜在的八郎鸟溜中、下寒武统层型剖面的辅助剖面。     

Cambrian trilobite Ovatoryctocara granulata Tchernysheva, 1962 and its biostratigraphic significance

The genus Ovatoryctocara Tchernysheva, 1962 and its key species Ovatoryctocara granulata Tchernysheva, 1962 are revised. Ovatoryctocara granulata occurs near the base of the Ovatoryctocara Zone and ranges up into the lower portion of the Kounamkites Zone in the Siberian Platform. O. granulata also appears in southeastern Guizhou, South China, but, O. granulata in northern Greenland may represent an indefinite species. Specimens of Ovatoryctocara from Newfoundland cannot be identified to species level. Specimens including two cranidia and three pygidia from the lower part of the Aoxi Formation at Yaxi Village, Shizhu Town, eastern Tongren, northeastern Guizhou, were previously assigned to O. granulata , which is now reassigned as a new species O. yaxiensis sp. nov. It bears following main features: glabella club-shaped, slightly expanded medially, with 4 pairs of lateral furrows, of which S1-S3 triangular pits, S4 shallow , connecting with axial furrow; shorter palpebral lobe situated a little anterior to midway of facial suture across the fixigenae, longer posterolateral area (exsag.); semielliptical pygidium consisting of seven axial rings with a terminal piece and with eight pairs of marginal tips giving a sawtooth-like shape of the lateral margins in dorsal view. Although O. granulata is a widely distributed species, the FAD of O. granulata, for a global stage boundary has still some disadvantages. First, its distribution is not as wide as that of Oryctocephalus indicus (Reed, 1910). Second, specimens of O. granulata are only common in Siberia. Third, the stratigraphic range of the species has not been studied in detail in all continents. Fourth, O. granulata is relatively small and easily affected by post-burial distortion. Last but not least, there exists obviously a facies change between the Ovatoryctocara Zone ( lower Amgan Stage; deeper water facies) and underlying Anabaraspis splendens Zone (Toyonian Stage; shallow water facies) in Siberian Platform. Nevertheless, the stratigraphic correlation utility of O. granulata in South China and Siberia is discussed.     

New data regarding acritarch biostratigraphy from the Early-Middle Cambrian Kaili Formation in Chuandong, Guizhou Province, China

Previous studies have evaluated acritarchs from the Balang and Pingzhai sections of the Early-Middle Cambrian Kaili Formation in east Guizhou, China. The results of these studies suggest that the acritarchs in these sections have potential biostratigraphic significance. More recently, 34 samples collected from 83m lower part of the Lower-Middle cambrian Kaili Formation in the Jianshan section of Chuandong, Guizhou Province were prepared for palynological analysis. Analysis of these samples revealed a distinct change in the acritarch assemblages at the bed, which was approximately 46m above the bottom of the Kaili Formation. These findings suggest a boundary represented by an important alteration of the ecological environment. In addition, the position of the acritarch biostratigraphic change is somewhat higher than the boundary between Cambrian Series 2 and Series 3 based on trilobites found in the same section. This indicates that the distinct change in acritarch assemblages is similar to the change in trilobite assemblages that occurs around the boundary between Cambrian Series 2 and Series 3. Therefore, acritarch biostratigraphy can provide data that can be used to define the base of Cambrian Series 3 in this region, and possibly worldwide.     

下寒武统宽背虫(Bathynotus)的灭绝过程——以贵州剑河八郎凯里组的Bathynotus kueichouensis为例

宽背虫(Bathynotus)这一传统早寒武世或寒武纪第2世晚期最重要的三叶虫属,广泛分布于全球寒武纪3个生物大区,为区域地层对比的标准化石.Bathynotus在贵州剑河八郎乌溜-曾家崖剖面凯里组下部极为丰富.该剖面已成为全球寒武系第2统和第3统界线层型候选剖面,表明凯里组是一个穿时的地层单元,其3个三叶虫带最下部一个带为Bathynotus holopygus-Ovatoryctocara granulata.经过逐层大量的化石标本采集统计证实,乌溜-曾家崖剖面宽背虫(Bathynotus)在距凯里组底部51.60 m处骤然绝灭,距寒武系第2统的顶界(距凯里组底52.80 m)只有1.20 m.本文就乌溜-曾家崖剖面凯里组下部宽背虫(Bathynotus)的数量分布变化认为其灭绝过程是逐步的.     

贵州黔东地区中-下寒武统凯里组发育特征

贵州黔东地区中－下寒武统凯里组主要由粉砂质泥岩，页岩及灰岩组成，富产三叶虫，其中台江八郎乌溜－曾家岩的凯时组含著名的中寒武世凯里生物群、早寒武世台江生物群，2001年成为国际中－下寒武统层型界线候选部，对其深入研究具有重大科学和实用意义。就我省黔东地区凯里组的岩石地层，生物地层，年代地层，沉积环境等进行研究及总结，亦确认黔东凯里组是一个十分重要的地层单位。