Permian and Triassic Radiolaria from Northwest Thailand: paleogeographical implications

Well-preserved radiolarians were recovered from seven sections in the Mae Hong Son-Mae Sariang area, northwestern Thailand. 51 species assigned to 34 genera are identified, including 1 new species (Triassospongosphaera erici Feng sp. nov.) and 19 unidentified species. They are divided into the Late Permian, late Ladinian and middle Carnian radiolarian assemblages. Newly identified radiolarian assemblages, together with the published radiolarian biostratigraphic data from this region, indicate that there was a pelagic basin during the Late Paleozoic and Triassic. This basin was joined to the Chiang Dao and Changning-Menglian oceanic basins, and they represent the main oceanic basin of the Paleotethyan Archipelago Ocean. This main oceanic basin was situated in the traditional “Shan-Thai Block”. Therefore, “the Shan-Thai Block” was not a single block during that stage, but composed of the Paleotethyan Ocean and two continental terranes that were affiliated with the Gondwana and Cathaysian domains, respectively.     

Nonmarine ostracodes at the Permian–Triassic boundary of the central part of the East European Platform

Extensive geological and paleontological materials from the upper Permian and the Lower Triassic of the East European Platform had been accumulated by the end of the 20th century. Recently obtained new data indicate the stratigraphic continuity of the East European Permian–Triassic succession. The Permian–Triassic boundary is in many sections associated with the boundary between the Zhukovian and Vokhmian regional stages. New stratigraphic data have led to the revision of the temporal distribution of Zhukovian and Vokhmian ostracodes. In contrast to previous ideas, the rapid development of genus Gerdalia already began in the Zhukovian time rather than in the Vokhmian. At the same time, the first Darwinula of the Triassic type also appeared in the Zhukovian. A proportion of the Permian species were found to cross the boundary between Zhukovian and Vokhmian. The degree of similarity between the Permian and Triassic ostracode assemblages turns out to be much higher than previously recognized.     

豫西P–Tr之交的微生物成因构造与后生动物扰动构造的耦合变化及生态学意义*

豫西登封、济源、宜阳、荥阳和巩义等地发育一套连续的二叠纪–三叠纪之交的陆相地层孙家沟组、刘家沟组和和尚沟组,保存着有环境和生物信息的微生物成因构造以及后生动物扰动构造,对二者的深入研究对二叠纪–三叠纪之交的陆相微生物与环境以及早三叠世的生物复苏有着重要的意义。研究区5个剖面保存了丰富的微生物成因构造和后生动物扰动构造,其中微生物成因构造有3大类、25小类,后生动物扰动构造有6属13种。这些构造在地层自下而上有一定的变化规律:微生物成因构造自孙家沟组中上部出现到刘家沟组顶部消失;后生动物扰动构造自刘家沟组上部出现,到和尚沟组上部逐渐增多,至中三叠世油房庄组基本达到灾变事件前的生物水平;二者仅在刘家沟组共生。本研究表明研究区微生物成因构造和后生动物扰动构造在整体上具有负相关性与耦合变化关系。     

泰国和越南藓类新纪录

报道了越南藓类的２个新记录,即：海南花锦藓Ｃｈｉｏｎｏｓｔｏｍｕｍ ｈａｉｎａｎｅｎｓｉｓ Ｔａｎ ＆Ｊｉａ和毛齿匍灯藓Ｐｌａｇｉｏｍｎｉｕｍ ｔｅｚｕｋａｅ Ｔ．Ｋｏｐ．;泰国藓类的３个新纪录,即：糙叶梨果藓Ｍａｓｔｏｐｏｍａ ｓｃａｂ＃颍椋妫铮欤椋酰? Ｔａｎ ＆ Ｔ．Ｎｉｎｈ,毛尖狗尾藓Ｒｈａｐｉｄｏｓｔｉｃｈｕｍ ｐｉｌｉｆｅｒｕｍ Ｂｒｏｔｈ。,细枝羽藓Ｔｈｕｉｄｉｕｍ ｄｅｌｉｃａｔｕ     

安徽巢湖孤峰组的放射虫化石

安徽巢湖下二叠统孤峰组含有极其丰富的放射虫化石,这些化石主要由阿尔拜虫类(albaillellids),球形多囊虫类(spherical polycystine)和十字多囊虫类(stauraxon polycystime)所组成,其中以oalbail-lella scalprata,P.longtanensis,P.sp.cf.P.longicornis,Phaenicosphaera mammilla,P.sp.A,Ruzhence-vispongus uralicus,R.sp.A和R.sp.B占绝对优势.对这3类化石进行了较为系统的描述,建立两个新种Latentifistula triradiata,Quadriremis flata,和两个组合带,即Pseudoalbaillella scalprata-P.sp.cf.P.longicornis和Phaenicosphaera mammilla-Ruzhencevispongus uralicus组合带,并且将这两个带与国内外相应时代的组合带进行了比较,讨论了这两个带的时代.     

Middle Permian Ostracods from Tak Fa Limestone, Phetchabun Province, Central Thailand

This paper presents the first Permian ostracod fauna discovered in Thailand. The ostracods are recovered from the Tak Fa Limestone (Middle Permian) in Phetchabun province, central Thailand. The ostracods belong to eight genera and 15 species. Four species are newly described: Sargentina phetchabunensis nov. sp., Geffenina bungsamphanensis nov. sp., Reviya subsompongensis nov. sp. and Bairdia takfaensis nov. sp. The ostracod assemblages characterize a shallow marine, near shore environment at the time of deposition. Except for one species, which shows palaeobiogeographical links between Central Thailand and South China, all the other species are endemic.     

西秦岭甘南地区二叠纪–三叠纪遗迹化石及其古环境意义

西秦岭甘南地区晚二叠世–中三叠世半深海–深海相地层中赋存丰富的遗迹化石,出现了居住迹、觅食迹、停歇迹和牧食迹4大类,14属,包括:Arenicolites、Chondrites、Dictyodora、Diplichnites、Diplopodichnus、Helminthopsis、Laevicyclus、Lockeia、Nereites、Palaeophycus、?Phycodes、Planolites、Protovirgularia、Scolicia。二叠纪乐平统毛毛隆组主要包括Protovirgularia组合、 Dictyodora–Helminthopsis组合和Diplichnites–Palaeophycus组合,上述3个遗迹化石组合主要由牧食迹和觅食迹组成,结合沉积相标志,指示了斜坡相沉积环境。早三叠世山尕岭群识出现了Diplopodichnus–Planolites组合,结合相应岩性及沉积相标志,反映了斜坡–盆地的深海沉积环境。中三叠世古浪堤组出现了Laevicyclus组合和丰富多样的沉积构造,指示了浊积扇的内扇环境。     

Microbialite concretions in a dolostone crust at the Permian–Triassic boundary of the Xishan section in Jiangsu Province,South China

Carbonate concretions with structures and fossil groups associated with microbialite developed in a dolostone crust at the Permian–Triassic boundary of the Xishan section in Jiangsu Province, South China. These structures include clotted fabrics and laminated carbonate needles, as well as abundant carbonate crystal fans. Fossil groups associated with microbialite include microconchids, small gastropods, and small foraminifers. These fabrics and fossils suggest that the concretions are carbonate microbialite blocks developed in the dolostone crust. On the basis of the analysis of the microfabrics and the fossil groups together with a comparison to modern analogues, we attribute the formation of the micritic patches in the microbialite concretions to the calcification of cyanobacterial mats via carbonate nanoparticles and we attribute the carbonate crystal fans to the direct recrystallization of micritic carbonates. The sparitic patches were interpreted as either the direct recrystallization of micritic carbonates or the precipitation of carbonate spars in the inter-/intra-spaces of metazoan shells together with the recrystallization of these shells. The similarities to modern stromatolites, both in morphology and in internal texture, suggest that the laminated carbonate needles are stromatolite laminae built by filamentous cyanobacteria. The preservation of these microbialite microfabrics indicates that early lithification by carbonate precipitation was widespread and intense following the end-Permian boundary events. The weak development of microbialites as small concretions may be attributed to the deeper water depth and the lower water energy in the Xishan area during the earliest Triassic.     

Early Carboniferous radiolarians from north-west Thailand: palaeogeographical implications

Moderately well-preserved radiolarian assemblages are described from bedded cherts south of Mae Hong Son, north-west Thailand. Twenty species and subspecies are identified, including one new species ( Archocyrtium sashidai Feng sp. nov.). The assemblages belong to the middle Early Carboniferous Albaillella indensis and Eostylodictya rota zones. The new data suggest that there was a pelagic basin between the Shan-Thai terrane and Gondwana during the Early Carboniferous. This implies, contrary to previous interpretations, that the Shan-Thai terrane had already rifted apart from Gondwana during the Early Carboniferous.     

Stromatolite-dominated microbialites at the Permian–Triassic boundary of the Xikou section on South Qinling Block,China

Permian–Triassic boundary microbialites (PTBMs) are organosedimentary carbonates formed immediately after the end-Permian mass extinction. All those reported PTBMs constrained by convincing conodont biozones are present stratigraphycally not higher than the Hindeodus parvus zone and most of them are dominated by thrombolites. This paper provides the first record of a brief, but spectacular development of stromatolite-dominated PTBMs within the basal Isarcicella isarcica conodont zone of the earliest Triassic from the Xikou section of South Qinling Block that was at the margin of the North China Block during the Permian–Triassic transition and was geographically separated from the major occurrence of post-extinction microbialites in the South China Block. This stromatolite cap overlies a 3.7-m-thick oolitic limestone and is composed of a lower 0.2-m-thick bed and an upper 0.5-m-thick bed, separated by a 0.2-m-thick greyish green siliciclastic mudstone. These two stromatolite beds mainly consist of columnar stromatolites with subordinate domal stromatolites. The intercolumn and interstitial spaces within the stromatolites are filled with oolitic grainstones. At the microscopic scale, laminoid structures in stromatolites comprise wavy, millimetric-domical and tangled laminae. The increased grain and fossil contents and/or bioturbation in the domical and tangled laminae indicate that the formation of these laminae is likely related to an increase in the populations and the disruptions by benthic metazoans, as well as an influx of sediment grains. The δ¹³C_carb values fluctuate between 2‰ and 3‰ in the uppermost Permian strata; a distinct negative shift of 1.9‰ occurs at the topmost oolitic grainstone, just below the lower stromatolite bed, and the lowest value of −0.1‰ is located at the base of the upper stromatolite bed. The stratigraphic succession from stromatolites to thrombolites of the PTBMs may represent a transgressive succession and/or a transient ecosystem recovery immediately after the end-Permian mass extinction. The thrombolites-dominated PTBMs mainly developed in near-equator shallow marine geographic locations, and stromatolite-dominated PTBMs mainly developed at higher latitude settings, which probably indicates that a relatively lower diversity and abundance of marine benthic metazoans existed at higher latitudes after the end-Permian mass extinction.     

New Late Triassic gastropods from the wallowa Terrane (Idaho) and their biogeographic significance

Summary Two characteristic new species and one new genus are described from the Late Triassic of Idaho (Wallowa Terrane):Brochidiella idahoensis n. gen., n. sp. andPtychostoma ornata n. sp.Brochidiella is only known from western North America.Ptychostoma is present in the Carnian of the European Alps (Tethys) and is widespread in the western part of the North American continent (Panthalassa). Late Triassic gastropod faunas from the accreted terranes of North America are poorly known but hold a great potential for future palaeobiogeographic reconstructions.     

Latest Permian Palaeolithocycliidae (Radiolaria) from South China

The family Palaeolithocycliidae Kozur and Mostler was formerly thought to be ranging from Devonian to Carboniferous. However, a lot of radiolarians assignable to this family were discovered in the late Changhsingian (Latest Permian) of South China. Six species, including Palaeolithocyclia pilata n. sp., Palaeolithocyclia platta n. sp., Paramphibrachium woni n. sp., Klaengspongus spinosus Sashida, Klaengspongus formosus n. sp. and Klaengspongus umbilicatus n. sp., have been identified. In this paper, these species are illustrated and described.     

Exceptions to the temperature–size rule: no Lilliput Effect in end-Permian ostracods (Crustacea) from Aras Valley (northwest Iran)

The body size of marine ectotherms is often negatively correlated with ambient water temperature, as seen in many clades during the hyperthermal crisis of the end-Permian mass extinction (c. 252 Ma). However, in the case of ostracods, size changes during ancient hyperthermal events are rarely quantified. In this study, we evaluate the body size changes of ostracods in the Aras Valley section (northwest Iran) in response to the drastic warming during the end-Permian mass extinction at three taxonomic levels: class, order, species. At the assemblage level, the warming triggers a complete species turnover in the Aras Valley section, with larger, newly emerging species dominating the immediate post-extinction assemblage for a short time. Individual ostracod species and instars do not show dwarfing or a change in body size as an adaptation to the temperature stress during the end-Permian crisis. This may indicate that the ostracods in the Aras Valley section might have been exceptions to the temperature–size rule (TSR), using an adaptation mechanism that does not involve a decrease in body size. This adaptation might be similar to the accelerated development despite constant instar body sizes that can be observed in some recent experimental studies of ostracod responses to thermal stress.     

A new study of Olenekian–Anisian boundary conodont biostratigraphy of the Tulong section in Himalaya Terrane,southern Tibet

The Himalaya Terrane of southern Tibet exposes successive shallow-marine carbonate deposits from the Lower to Upper Triassic, and is a key region for studying the Triassic conodont biostratigraphy at the northern margin of the Indian Plate. On the basis of newly collected samples from the Kangshare and Laibuxi formations at the Tulong section, 11 conodont species of 7 genera were identified, and four conodont zones were established, namely, the Novispathodus abruptus Zone (lower Spathian, first reported in Tibet), the Columbitella jubata Zone (middle Spathian), the Triassospathodus symmetricus Zone (upper Spathian), and the Chiosella timorensis Zone (lowermost Anisian) in ascending order. The first occurrence (FO) of Chiosella timorensis indicates the Olenekian–Anisian boundary (OAB) at Bed 25, upper part of the Kangshare Formation. The regional and global correlation of these conodont zones is synthesized.     

Trimeridianellidae nov. fam., a Triassic spumellarian radiolarian family with simple initial skeleton and pyloniacean mode of growth

Based on several samples of Middle and Late Triassic age, the authors describe a new family of spumellarian Radiolaria – Trimeridianellidae Dumitrica and Tekin, characterized by a three-fold symmetry, a first shell of triangular prism type with 6 primary rays originated at the edges of two bases of the prism, or 3 meridian arches with 3 equatorial rays, and growth of pyloniacean type. The family comprises 4 monospecific new genera (Enneacladus Dumitrica, Endoprisma Dumitrica, Trimeridianella Dumitrica and Tekin, and Tristylopyle Dumitrica), 4 new species and one left in open nomenclature. In spite of their spotty occurrences and low diversity, the authors attempt to trace the evolution of the family, which is considered to be the result of heterochrony in ontogenetic growth, mostly of paedomorphic type. The family seems to be related to the Middle Triassic family Patruliidae Dumitrica with which it shares in common the simple microsphere with 6 primary rays and the pyloniacean mode of growth.     

Ladinian radiolarian fauna from West Sichuan, China

A poorly preserved, but diversified radiolarian fauna was recovered from thin-bedded cherts occurring in the southeast of Daofu, Sichuan Province, southwestern China. Twenty-two radiolarian species belonging to 10 genera are identified and three new species (Paroertlispongus daofuensis n. sp., Falcispongus heinzi n. sp., Falcispongus pauliani n. sp.) are described. Falcispongus heinzi represents a transitional species between genera Oertlispongus inaequispinosus Dumitrica, Kozur and Mostler and Falcispongus Dumitrica. The fauna is divided into two assemblages, namely Muelleritortis cochleata and Oertlispongus inaequispinosus assemblages, which can be well correlated with the Ladinian radiolarian zones from Europe. The fauna indicates that basaltic rocks occurring in the Xianshuihe Belt were formed mainly during the Middle Triassic. Our results thus extend the previously known geological age of the Xianshuihe Belt to the Middle and Late Triassic interval.