| 1. |
- Harper, David A.T., et al.
(författare)
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Early Cambrian brachiopod-dominated shell concentrations from North-East Greenland: Environmental and taphonomic implications
- 2021
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Ingår i: Global and Planetary Change. - : Elsevier BV. - 0921-8181 .- 1872-6364. ; 204, s. 103560-103560
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Tidskriftsartikel (refereegranskat)abstract
- The occurrence of a series of thin but persistent early Cambrian (Cambrian Age 4) brachiopod shell concentrations extending along a transect of some 150 km in NE Greenland, indicates the ability of the group to form widespread, skeletal pavements very early in the history of the phylum, its gregarious behaviour and ability to harness available nutrients. These extensive shell pavements within the Bastion Formation mark biological events within the basin, the abundance of shells perhaps associated with oscillating redox conditions prompting the dissolution of phosphate and its spread across the shelf. The shells were subsequently reworked and deposited by episodic distal storm surges with some winnowing.
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| 2. |
- Lehnert, Oliver, et al.
(författare)
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Conodont biostratigraphy in the Early to Middle Ordovician strata of the Oslobreen Group in Ny Friesland, Svalbard
- 2013
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Ingår i: Zeitschrift der Deutschen Gesellschaft fur Geowissenschaften. - : Schweizerbart. - 1860-1804. ; 164:1, s. 149-172
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Tidskriftsartikel (refereegranskat)abstract
- The remotely located Cambro-Ordovician strata in Ny Friesland, NE Spitsbergen, Svalbard, are referred to the Oslobreen Group, which is composed of the Tokammane, Kirtonryggen and Valhallfonna formations. Herein we record the conodont succession of the Kirtonryggen and Valhallfonna formations. Collections of well-preserved conodonts (CAI 1) have been recovered from the Lower to lower Middle Ordovician interval in the region. Eight regional conodont zones are established in this preliminary study of the Oslobreen Group exposed at Hinlopenstretet, NE Svalbard. In ascending order these zones are: Rossodus manitouensis, Macerodus dianae, Oneotodus costatus, Oepikodus communis, O. evae, O. intermedius, Periodon aff. flabellum-Periodon hankensis and Periodon macrodentatus. The yield is relatively poor for the Kirtonryggen Formation, but the oldest Ordovician conodont faunas span the Tremadocian Rossodus manitouesis through Macerodus dianae zones followed by the Floian Oepikodus communis Zone. The taxa are typical of the tropical North American Midcontinent faunal province that dominated the region until open marine associations invaded the shallow shelf (i.e. Evae transgression). The pandemic Oepikodus evae becomes frequent and is succeeded by O. intermedius in abundance in the lower Valhallfonna Formation (Olenidsletta Member). The upper strata are characterised by the Periodon-Paroistodus assemblage characteristic for outer shelf and slope environments around Laurentia. In total, this formation comprises the Floian and Dapingian stages and ends in the early Darriwilian Periodon macrodentatus Zone in this region. The Ny Friesland faunas show affinities to coeval assemblages from Northeast Greenland and West Newfoundland.
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| 3. |
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| 4. |
- Stouge, Svend, et al.
(författare)
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Lower palaeozoic stratigraphy of Murchisonfjorden and Sparreneset, Nordaustlandet, Svalbard
- 2011
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Ingår i: Geografiska Annaler. Series A, Physical Geography. - : Informa UK Limited. - 0435-3676 .- 1468-0459. ; 93:4, s. 209-226
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Tidskriftsartikel (refereegranskat)abstract
- The Lower Palaeozoic stratigraphy of the Kap Sparre Formation of Kulling (Hecla Hoek Succession) from Murchisonfjorden and eastern Nordaustlandet of Svalbard is described based on new field observations in the region. The investigated sedimentary succession is referred to the Upper quartzite series and Upper dolomite series of the Kap Sparre Formation. The observed sequence resembles that of the Oslobreen Group from central and northeastern Ny Friesland and the formal and well-established and more detailed stratigraphical framework used in Ny Friesland may apply for the strata at Sparreneset and in Murchisonfjorden, western Nordaustlandet. The lower Palaeozoic succession overlies the uppermost Precambrian sediments (Dracoisen Formation = the lower part of Kap Sparre Formation sensu Kulling) of the Polarisbreen Group with a cryptic unconformity, and a regional stratigraphical gap spanning the late Ediacaran developed on the platform. Additions to the previous descriptions of some of the existing units are presented. The new lithostratigraphical unit: Black shale and limestone unit is proposed informally. It is a Lower(?) to Middle Cambrian black shale with limestone nodules and lenses that is exposed on the northwest coast of Krossoya in Murchisonfjorden, Svalbard. In addition, a Dolostone-limestone unit, Middle(?) Cambrian to Lower Ordovician, composed of dolostone and dolomitized limestone and minor limestone, and a Limestone unit (Lower to Middle(?) Ordovician), which overlies the Upper dolomite series are added to the succession. The deposits as a whole show the development of an environmentally controlled carbonate platform that marked the transition from the inner to the outer shelf that evolved during the opening and spreading of the Iapetus Ocean.
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| 5. |
- Terfelt, Fredrik, et al.
(författare)
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Re-evaluation of the conodont Iapetognathus and implications for the base of the Ordovician System GSSP
- 2011
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Ingår i: Lethaia. - : Scandinavian University Press / Universitetsforlaget AS. - 0024-1164. ; 45:2, s. 227-237
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Tidskriftsartikel (refereegranskat)abstract
- In 2000, the International Union of Geological Sciences (IUGS) ratified the decision from the International Working Group on the Cambrian–Ordovician Boundary (COBWG) to place the Global boundary Stratotype Section and Point (GSSP) for the base of the Ordovician System in the Green Point section, Newfoundland, Canada, at a point coinciding with the first appearance of the conodont Iapetognathus fluctivagus. However, a restudy of the conodont successions from Green Point shows that this species is not present at the boundary interval, and as a consequence the section does not fulfil the biostratigraphical requirements of a GSSP. The GSSP horizon as now defined is based on a level part-way through the range of I. preaengensis – a species with lower first appearance datum (FAD). The true FAD of I. fluctivagus is above the FAD of planktonic graptolites and well above the FAD of I. preaengensis. As a consequence of these problems, a restudy of the GSSP section and the other sections in the Cow Head Group is necessary. A redefinition of the GSSP horizon is suggested. The following four alternative horizons have potential as new horizons for the GSSP level: the FAD of Cordylodus intermedius; the FAD of Cordylodus andresi; the FAD of Eoconodontus notchpeakensis; and the FAD of the agnostoid Lotagnostus americanus.
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| 6. |
- Wu, Rong Chang, et al.
(författare)
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Conodont faunal dynamics across the middle and upper ordovician boundary in the Yichang area, western Hubei province, South China
- 2016
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Ingår i: Canadian Journal of Earth Sciences. - : Canadian Science Publishing. - 0008-4077 .- 1480-3313. ; 53:8, s. 856-864
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Tidskriftsartikel (refereegranskat)abstract
- A total of 6094 conodont specimens, assigned to 18 genera and 27 species, have been recovered from the uppermost Kuniutan and Miaopo formations, spanning the latest Darriwilian - early Sandbian in age, at the Jieling section, Yichang, Hubei Province. Three conodont zones have been recognized, i.e., in ascending order, the Pygodus serra Zone, the Pygodus anserinus - Yangtzeplacognathus jianyeensis Zone, and the Baltoniodus alobatus Zone. The conodont biodiversity in the Miaopo Formation shows a decreasing trend at Jieling. Multivariate statistical analysis of the conodont fauna from the Jieling section shows that the Baltoniodus and Periodon biofacies are present in the uppermost Kuniutan Formation, and the Periodon and Scabbardella biofacies can be recognized in the Miaopo Formation.
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| 7. |
- Wu, Rongchang, et al.
(författare)
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Early-Middle Ordovician conodont biofacies on the Yangtze Platform margin, South China: Applications to palaeoenvironment and sea-level changes
- 2014
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Ingår i: Journal of Asian Earth Sciences. - : Elsevier BV. - 1367-9120. ; 96, s. 194-204
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Tidskriftsartikel (refereegranskat)abstract
- 9172 Conodonts have been recovered from the uppermost Hunghuayuan Formation and the Zitai Formation at two sections in Shitai County, southern Anhui Province, South China, which was situated close to the margin of the Lower Yangtze Platform during the Early to Middle Ordovician. Systematic and multivariate statistical studies on these conodonts permit recognition of seven conodont biofacies: Tropodus biofacies, Diaphorodus biofacies, Oepikodus biofacies, Baltoniodus biofacies, Paroistodus biofacies, Periodon biofacies and Protopanderodus biofacies. Each biofacies is restricted to a particular lithofacies and stratal position and shows a consistent order and/or position within the succession. Turnover of these conodont biofacies is related to sea-level changes. The transgressive-regressive patterns demonstrated by the conodont biofacies compare closely to published sea level curves for South China, and highlight the utility of conodont biofacies as a means of confirming sedimentological evidence of relative sea-level change. (C) 2014 Elsevier Ltd. All rights reserved.
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