Upper Silurian and Lower Devonian Biostratigraphy, Royal Creek, Yukon Territory, Canada
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Abstract A limestone and shale sequence, some 1500 feet thick, apparently gradational from Silurian into Devonian, and made up of at least 300 feet of Ludlovian and possibly Pridoli equivalent (Upper Silurian) and 1200 feet of nearly complete Lower Devonian, is described from northern Yukon. The Upper Silurian is dominantly a graptolitic shale, but limestone bands in the upper part yielded a small brachiopod fauna including Atrypella cf. tenuis. The entire Lower Devonian part of the sequence is very fossiliferous and is one of considerable significance because of the alternation of shelly faunas with graptolites in the middle one-third. Brachiopods, of which more than one hundred species are recognized, are by far the most common fossils, and are dominated by atrypids, rhynchonellids, and orthids, but include pentamerids, strophomenids, athyrids, and spiriferids. The brachiopods at the genus, and to some extent the species, level, show affinities to the Nevada sequence and particularly to the Old World Province of the Uralian-Bohemian region; they bear no relationship to the Lower Devonian of the Appalachian Province, or to the Rhenish Community of northwestern Europe. The northern Yukon region, therefore, provides an intermediate point in possible migration routes of brachiopods between the widely separated regions of the American Great Basin and the Urals and Siberia. The Upper Silurian and Lower Devonian stages recognized, and their six faunal subdivisions are as follows: Lower Ludlovian represented by the Monograptus nilssoni Zone; Middle or Upper Ludlovian, or possibly Pridoli equivalent: Atrypella cf. tenuis unit; Gedinnian: Gypidula cf. pelagica unit; lower Siegenian, represented by the Spirigerina cf. supramarginalis unit; upper Siegenian characterized by the Gypidula sp. 1 - Davidsoniatrypa unit; and lower Emsian: Nymphorhynchia pseudolivonica - Sieberella cf. weberi unit. The Zone of Monograptus yukonensis is concluded to be late Siegenian and early Emsian in age. Conodonts recovered from the sequence provide valuable additional information, and in general agree well with brachiopod correlations.Keywords:
Devonian
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Abstract Central Kazakhstan is of great interest as a region which, in Late Silurian and Early Devonian, was a route for faunal migration between the Atlantic and Pacific realms. In this region the Upper Silurian and Lower Devonian are represented by marine terrigenous deposits containing numerous faunal remains, among which more than 70 species of trilobites have been discriminated. Although endemic forms are predominant, about 20 percent of the species are analogous or close to west European ones (Barrandian, Harz) and about 30 per cent are close to known species from North America (New York, Appalachians). The Late Silurian trilobites of Central Kazakhstan have many features in common with trilobites of the Ludlovian and of the Barrandian (Phacops fecundus orientalis Z. Max., Cheirurus quenstedti orientalis Z. Max., etc.). In the first half of the Early Devonian (Pribalkhash horizon), the trilobites of Kazakhstan show a close resemblance to the trilobites found in the Helderbergian of North America (Phacops logani balchashensis Z. Max., Phacops saryarkensis Z. Max., etc.) The trilobites of the later half of the Early Devonian permit a firm correlation of the Sarzhal’sky horizon with the Pragian, (Phacops cephalotes Hawle et Corda, Crotalocephalus hexaspinus Z. Max. of the C. group, etc.). At the same time, the abundance of trilobite species close to those described from the Devonian of North America (Phacops cristata Hall group, the subgenus Crassiproetus Stumm, the genus Dechenellurus Z. Max., etc.) allows a correlation with the Oriskany, Schoharie and Lower Onondaga beds. Since, however, this comparison is based upon similarities rather than identities, a relatively detailed correlation is difficult. We may suppose that trilobites of this type appeared in the Early Devonian of Kazakhstan and later migrated to the east through the regions of Altai, Mongolian Altai, Transbaikal and the Far East, because their remains are observed in North America in higher deposits than the analogues of the Pragian stage.
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ABSTRACT A sequence of about 1,500 feet of limestone and shale, apparently gradational from Silurian into Devonian and representing Upper Silurian (Ludlovian) through upper Lower Devonian (Emsian), is present at the headwaters of Royal Creek, Yukon. Lower Devonian fossils which are abundant in parts of the sequence show affinities on the one hand to those of Nevada, and on the other hand to those of the Bohemia-Urals regions of the Old World. The Royal Creek succession falls into six more or less natural faunal units, each with a distinctive fauna, or with unique faunal elements, one or more of which is used to name the unit. The faunal units and their proposed ages are as follows: Monograptus nilssoni unit: Lower Ludlovian; Atrypella tenuis unit: possibly Middle or Upper Ludlovian; Gypidula cf. pelagica unit: Gedinnian; Spirigerina unit: Siegenian; Gypidula sp. 1--Biconostrophia unit, which falls within the Monograptus yukonensis Zone: Upper Siegenian and Lower Emsian; Nymphorhynchia pseudolivonica-Sieberella unit: Emsian.
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Abstract The Devonian in the eastern portion of Siberia is represented by its three series and forms, with the Silurian and Lower Carboniferous, a single sedimentary cycle. The study of the included organic remains has enabled the subdivision of the Devonian into local zones. In lithologically uniform deposits one may distinguish a lower Devonian with Favosites porfirievi var. oldoica Dubat. and Phacops logani asiaticus Z. Max. and an upper Lower Devonian with Pleurodictyum mongolicum Tchern., Rhitistrophia beckii Hall, Delthyris perlamellosus Hall and Phacops cristata Hall. Most widely distributed are the Middle Devonian deposits, particularly the Givetian, along with the Early Frasnian. The lower half of the Middle Devonian (corresponding to the Onondaga of eastern North America) is characterized by reef limestones with corals, bryozoa and crinoids. They form a favosites halanerisis Dubat—Stenophyllum spinulosum Shosh. assemblage-zone. Synchronous terrigenous deposits contain the remains of brachiopods, trilobites and some other organisms. Most notable as guide fossils are Fimbrispirifer divaricatus Hall and Delthyris missouriensis Tansey. It is difficult to distinguish the Givetian from Early Frasnian deposits on a lithological basis. They are considered, therefore, as a single subdivision, though, on the basis of rich assemblages of organic remains, they may be subdivided into a lower unit with Spinocyrtia martianofi Stuck., Mucrospirifer mucronatus Conr., Euryspirifer ex gr. cheehiel Kon. and an upper unit with Cyrtospirifer achmet Nal. and Spinocyrtia ali Nal. The Upper Devonian comprises three units—lower beds with Cyrtospirifer achmet Nal.—middle beds with Atrypa, Cyrtospirifer ex gr. verneuili Mureh., Mucrospirifer posterus H. et Cl., and upper beds with Cyrtospirifer sulcifer, H. et Cl., C. ex gr. disjunctus Sow., and Platycrinus; they embrace the Frasnian and Famennian Stages and are equivalent to the Seneca and Chautauqua series of North America (New York State). The Devonian fauna of the Far East and the Transbaikal region, apart from endemic features peculiar to Mongolo-Okhotsk province, possesses some of the peculiarities of the Dzungaro-Balk hash and Altai-Sayan provinces and belongs to the Pacific Zoogeographie region.
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ABSTRAcr-Devonian tentaculitids (Mollusca: Cricoconarida) are described for the first time from Alaska. The tentaculitids are from the Salmontrout Limestone and the limestone and shale member of the McCann Hill Chert in east-central Alaska. The Salmontrout Limestone, which contains mostly thin-shelled tentaculitids, is Lower Devonian (upper Siegenian through upper Emsian). The limestone and shale member of the McCann Hill Chert, which contains mostly thick-shelled types, is upper Lower Devonian (Emsian). The similarity in succession of tentaculitids in Alaska to the tentaculitid zones established in Europe, and their association in Alaska with graptolites and other fossils similar to those found in correlative tentaculitid zones in Europe, shows that they can be used for precise and reliable longrange correlation. One new genus, Semicyclus, and five new species, Dicricoconus dutroi, Dicricoconus triannulatus, Uniconus orbiculus, Semicyches brabbi, and Nowakia parabarrandei, are established.
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Abstract The Lower and Middle Devonian marine sequence of Central Kazakhstan, in a highly fossiliferous clastic facies, forms a continuous sequence with the Silurian. The Lower Devonian is divided into two units - the Balkhash Land and Sardjal divisions, tentatively correlated with Gedinnian, Siegenian, and Emsian. In the Balkhash Land unit, Devonian Heliophyllum, Stenophyllum, Anoplotheca, Euryspirifer inelegans (Hall), Howellella mercuri (Gos.) etc., make their appearance, in association with Silurian species. In the Sardjal division Acrospirifer primaevus kasachstanica Kap., Rhytistrophia beckii (Hall), Crotalocephalus gibbus hexaspinus Z. Max., etc. occur. In the Middle Devonian, the Kazakh, Besoba and Aidarly divisions, tentatively correlated with “Lower Eifelian”, “Upper Eifelian” and Givetian, have been distinguished. In the Lower Devonian genera and species as Hexacrinus, Decacrinus, Isorthis pertermedius (Schn.), and E. supraspeciosus Lotze appear. In the “Upper Eifelian” Calceola sandalina Lam., Grypophyllum striatum Spassky, and Striatopora schandiensis Dubat. are diagnostic. The Givetian Stage is characterized by the presence of the Mucrospirifer mucronatus (Hall) group of brachiopods. In the Lower Devonian and “Lower Eifelian”, the marine basin occupied a vast territory. By the end of the “Lower Eifelian”, the sea had regressed so that a major part of the region was emergent. Marine sedimentation continued through the Middle Devonian only in the southeast. The marine basin of central Kazakhstan was a peculiar palaeozoogeographical province, comprising western European, North American, and local faunas. The brachiopod fauna in Lower Devonian and “Lower Eifelian” differs sharply from the contemporaneous fauna of the Urals, Kuznetzk basin and central Asia. Not until the “Upper Eifelian” is the fauna comparable with contemporaneous associations of one of the other regions mentioned above.
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The ammonoid successions in the Devonian rocks of the Torquay, Chudleigh, and Padstow areas of Devon and Cornwall are described and it is shown that representatives of all the German Devonian ammonoid Stufen occur in south-west England. The ammonoid successions demonstrate significant facies changes within the Middle and Upper Devonian among the areas discussed. In the Torquay area the zone of Anarcestes lateseptatus is recognizable in the Calceola Shales, and in the massive Givetian limestones two ammonoid faunas occur, a lower zone with Maenioceras molarium and an upper zone with M. terebratum. The main Lummaton Shell Bed includes the fauna of the terebratum Zone. Limestone sedimentation probably continued into the Lower Frasnian, but the Manticoceras cordatum and Crickites holzapfeli zones are represented at Saltern Cove by thick argillaceous developments: it appears that at Torquay these zones may be reduced in thickness. An ostracodslate facies follows immediately above the holzapfeli Zone; ostracod evidence shows that this facies continues into the Upper Famennian. A similar Middle Devonian succession, but without ammonoids, is developed at Chudleigh, but the Upper Devonian sequence is a reduced one of nodular limestones and slates with nodules in which the Manticoceras, Cheiloceras, Platyclymenia, Clymenia, and Wocklumeria Stufen occur. The name Mount Pleasant Series is proposed for the Famennian sequence, which is 170 ft in thickness. This Upper Devonian facies is thought to be comparable with the German schwellen facies in contradistinction to that at Torquay, which is of becken type. The Middle Devonian in the Padstow area is predominantly of slate facies with minor calcareous developments in the Eifelian and Givetian. Three main goniatite faunas can be recognized within the Middle Devonian. Good goniatite faunas of the Frasnian cordatum Zone occur in banded slate facies and these are overlain by a thick series of ostracod-bearing slates. It is evident that the ostracod facies enters at a lower level than at Torquay. The following new species of goniatites are described: Archoceras ussheri, Ponticeras pedderi, and Protornoceras foxi.
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Two Silurian sections were re-measured, one being situated on the northern bank of the Yinshuihe River and the other on the northern bank of the Shouxinghu Lake of the Lazhuglung area of Doima, Rutog, NW Tibet. The lower part of the Shouxinghu Formation is composed of grey-black carbonaceous shales and slates, which contain graptolites Spirograptus sp. and chitinozoans Ancyrochitina brevicollis and Conochitina sp., indicating a Llandovery age, rather than the Upper Ordovician mentioned previously. Real Ordovician rocks have not been found until now there. The Silurian rocks in that area were divided in ascending order into the Llandovery Yinshuihe and Shouxinghu Formations, the Wenlock Pur Co Formation and the Ludlow-Pridoli Yeniupo Formation, a new lithostratigraphic unit here established, on the basis of diversified faunas. The lowermost beds correspond to the Llandovery Spirograptus turriculatus and Streptograptus crispus graptolite zones, and the uppermost beds to the Kopaninoceras juncudum cephalopod zone and its coeval Neoprioniodus latidentatus-Ligonodina siluria conodont assemblage. So far the Lazhuglung sections have been known to be the best sections in North Tibet in both outcrop-completeness and fossil abundance. The erectness of the Silurian sequence there provides important data for the reconstruction of Tibetan Early Plaeozoic history and the Silurian correlation of Qinghai-Xizang Plateau.
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Vertebrate microscopic remains of twenty-six taxa of thelodonts, heterostracans, osteostracans, anaspids, acanthodians and chondrichthyans are described from limestone beds in two localities of Late Silurian - Early Devonian age of the Chester Bjerg Formation, Hall Land, North Greenland. The limestone beds form a minor part of a monotonous calcareous sandstone-siltstone-mudstone sequence at the top of the Franklinian Basin succession.Stratigraphical recognition using several thelodont and acanthodian taxa, supported by regional geological and structural trends, suggests a Silurian-Devonian boundary interval between beds of the Halls Grav and Monument localities. This possible resolution of the previous problematic correlation between the two distant sections of monotonous nature demonstrates the potential biostratigraphic utility of thelodonts in Silurian -Devonian marine successions.The Chester Bjerg Formation thelodont assemblage is unique with several new endemic taxa, but Loganellia cf. L. tuvaensis is very similar to the type material of the Tuva region south of Siberia, Russia and indicates a Late Silurian age for the beds of the Halls Grav locality. Canonia cf. C. grossi suggests an Early Devonian age for the Monument locality, since Canonia is so far only found in Lower Devonian marine strata of Arctic Canada and Russia. Fragments of cosmopolitan acanthodian genera such as Poracanthodes, Gomphonchus and Nostolepis are found together with heterostracans, osteostracans, anaspids and chondrichthyans at both localities but do not give a more exact age determination than Late Silurian - Early Devonian. New thelodont taxa are Loganellia almgreeni sp. nov., Paralogania foliala sp. nov., Praetrilogania grabion gen. et sp. nov. and Thulolepis striaspina gen. et sp. nov. Nostolepis halli sp. nov. is a new acanthodian species.
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ABSTRACT Graptolites and trilobites from the lower part of the Sunblood Formation extend the age of that unit to include Early Ordovician (Arenig). The overlying Whittaker and Delorme Formations contain all series from Middle Ordovician through Lower Devonian. The Delorme Formation has yielded early Lower Devonian (Lochkovian) graptolites, and a rich brachiopod fauna that suggests correlation with the Lower Devonian Borszczow Stage of Podolia.
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Research Article| May 01, 2007 Uppermost Silurian to Lower Devonian radiolarians from the Hitoegane area of the Hida-gaien terrane, central Japan Toshiyuki Kurihara Toshiyuki Kurihara Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan email: tosiyuki@rj8.so-net.ne.jp Search for other works by this author on: GSW Google Scholar Author and Article Information Toshiyuki Kurihara Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan email: tosiyuki@rj8.so-net.ne.jp Publisher: Micropaleontology Press Received: 28 Apr 2007 Accepted: 15 May 2007 First Online: 06 Mar 2017 Online ISSN: 0026-2803 Print ISSN: 1937-2795 © 2007 The Micropaleontology Project, Inc. Micropaleontology (2007) 53 (3): 221–238. https://doi.org/10.2113/gsmicropal.53.3.221 Article history Received: 28 Apr 2007 Accepted: 15 May 2007 First Online: 06 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Toshiyuki Kurihara; Uppermost Silurian to Lower Devonian radiolarians from the Hitoegane area of the Hida-gaien terrane, central Japan. Micropaleontology 2007;; 53 (3): 221–238. doi: https://doi.org/10.2113/gsmicropal.53.3.221 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyMicropaleontology Search Advanced Search Abstract Two distinctive uppermost Silurian to Lower Devonian radiolarian assemblages, the Pseudospongoprunum tauversi Assemblage and the Futobari solidus-Zadrappolus tenuis Assemblage, occur in new localities of felsic tuffaceous strata in the Hitoegane area of the Hida-gaien terrane of central Japan. The first is characterized by the presence of P. tauversi and diverse inaniguttids, which can be correlated with the well-constrained Pridolian radiolarian zonal fauna defined in west Texas. The second occurs stratigraphically above beds containing the P. tauversi Assemblage and in strata correlative to beds from which a probably Lower Devonian flora has been recovered. These occurrences indicate that the F. solidus-Z. tenuis Assemblage ranges from uppermost Silurian to Lower Devonian. Based on the stratigraphic context for the underlying Pridolian P. tauversi Assemblage, the probably Lower Devonian flora, and the reinterpretation of the previously dated zircon U/Pb age, the F. solidus-Z. tenuis Assemblage is the first confirmed radiolarian assemblage from the lowermost Devonian. Previous workers have suggested that entactiniid radiolarians became increasingly dominant in the latest Silurian to Early Devonian, but the present study shows that inaniguttids such as Futobari and Zadrappolus were dominant in the early to probably middle Early Devonian. A new inaniguttid species is described: Zadrappolus (?) nudus n. sp. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
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