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Upper Llandovery and Wenlock Cyrtograptus from the Silurian Peary L~Nd Group, North Greenland GEUS Report File No

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Upper Llandovery and Wenlock Cyrtograptus from the Silurian Peary L~Nd Group, North Greenland GEUS Report File No Upper Llandovery and Wenlock Cyrtograptus from the Silurian Peary L~nd Group, North Greenland GEUS Report file no. 22315 Merete BjerresKOV GRØNLANDS GEOLOGISKE UNDERSØGELSE Bulletin 163 1992 GRØNLANDS GEOLOGISKE UNDERSØGELSE Bulletin 163 Upper Llandovery and Wenlock Cyrtograptus from the Silurian Peary Land Group, \I (;) North Greenland ~() Merete Bj erreskov 1992 Bjerreskov, M. 1992: Upper Llandovery and Wenlock dillera, and especiaIly from the eastern part of the Cyrtograptus from the Silurian Peary Land Group, Franklinian Basin in Arctic Canada, allowa good corre­ North Greenland. Bul!. Grønlands geol. Unders. 163, lation with the established graptolite zones in these 31 pp. areas. The folIowing graptolite biozonallevels are rep­ resented in North Greenland: the latest Llandovery C. Recent collections of graptolites from the Silurian Peary sakmaricus Zone, the early Wenlock C. centrifugus - C. Land Group in North Greenland have yielded several insectus Zone, possibly the C. murchisoni Zone, the M. samples of Cyrtograptus. From this material 16 species instrenuus - C. kolobus Zone, the C. perneri - M. and subspecies are described, and one new species, opimus Zone and the C. lundgreni - M. testis Zone. Cyrtograptus multibrachiatus, is erected. The described material represents a time span from the uppermost Llandovery to the uppermost Wenlock. The similarities Author's address: between the graptolite faunas from North Greenland Geological Museum, øster Voldgade 5-7, DK-BSD and those described from the Northern Canadian Cor- Copenhagen K, Denmark. Grønlands Geologiske Undersøgelse Ujarassiortut Kalaallit Nunaanni Misissuisoqarfiat Geological Survey of Greenland The Geological Survey of Greenland (GGU) is a research institute affiliated to the Mineral Resources Administration for Greenland (MRA) within the Danish Ministry of Energy. As with all other activities involving the non-living resources in Greenland, GGU's investigations are carried out within the frarnework of the policies decided jointiy by the Greenland Home Rule Authority and the Danish State. © GGU, Copenhagen, 1992 ISSN 0105-3507 Contents Introduction. ...................................... 5 Cyrtograptus lapworthi n. ssp. Melchin, 1987. ....... 16 Lithostratigraphy and basin development ............. 5 Cyrtograptus multibrachiatus n. sp.. ................ 16 Biostratigraphy .................................... 8 Cyrtograptus muitiramis Tornquist, 1910 ............ 18 Cyrtograptus sakmaricus Zone. .................... 10 Cyrtograptus murchisoni murchisoni Cyrtograptus centrifugus Zone. .................... 10 Carruthers, 1867. 20 Cyrtograptus murchisoni Zone. .................... 10 Cyrtograptus murchisoni bohemicus Boucek, 1931? .. 22 Monograptus instrenuus - Cyrtograptus Cyrtograptus polyrameus Fu & Song, 1983 .......... 22 kolobus Zone "........................... 10 Cyrtograptus pseudomancki Lenz & Melchin, 1991. .. 25 Cyrtograptus perneri - Monograptus opimus Zone ... 10 Cyrtograptus sakmaricus Koren', 1968... ..... .. .. 26 Cyrtograptus lundgreni - Monograptus testis Zone ... 11 Cyrtograptus tul/bergi Boucek, 1933? ............... 27 Biogeography ..................................... 11 Cyrtograptus sp. 1 28 Systematic descriptions ............................. 12 Cyrtograptus sp. 2 28 Cyrtograptus centrifugus Boucek, 1931. ............. 13 Cyrtograptus? sp. ".............................. 28 Cyrtograptus sp. cf. C. insectus Boucek, 1931 14 Acknowledgements ................................ 29 Cyrtograptus kolobus Lenz & Melchin, 1991 15 References. ....................................... 29 Cyrtograptus lapworthi Tullberg, 1883? ............. 15 Dansk sammendrag Nye samlinger af graptolitter fra den silure Peary niske Bassin i arktisk Canada. Ved korrelation er føl­ Land Gruppe i Nordgrønland indeholder adskillige ek­ gende graptolitzoner fundet repræsenteret i Nordgrøn­ semplarer af Cyrtograptus. Seksten arter og underarter land: C. sakmaricus Zonen (seneste LIandovery), og fra er beskrevet, og der er oprettet en ny art: Cyrtograptus tidlig til sen Wenlock: C. centrifugus - C. insectus Zo­ multibrachiatus. Det nordgrønlandske materiale har nen, muligvis C. murchisoni Zonen, M. instrenuus - C. stor lighed med graptolitfaunaer fra de nordlige cana­ kolobus Zonen, C. perneri - M. opimus Zonen og C. diske Cordillerer og fra den østlige del af det Frankli- lundgreni - M. testis Zonen. Imaqarnersiuineq Avannaarsuani ujaqqani ataatsimut Peary Land Cordillerinik taagutilinni Canadallu Issittortaani Fran­ Gruppe-mik taaguuteqartuni, ukiut 439--409 milliunit kliniske Bassin-imi graptolittinut assingusorujussuup­ matumatu siornatigut pinngorsimasuni, graptolittini put. Avannaarsuani graptolitteqarfiit makua nalunaar­ ataatsimoortuni immikkoortut Cyrtograptus-imik taagu­ sorneqarsimapput. C. sakmaricus Zonen, C. centrifugus utilinnik arlalinnik ilaqarput. Assigiinngitsut arfersanil­ - C. insectus Zonen, qularnanngitsumillu C. murchisoni lit allaaserineqarput, immikkoortorlu nutaaq taaguuser­ Zonen, M. instrenuus - C. kolobus Zonen, C. perneri ­ neqarsimavoq, Cyrtograptus multibrachiatus. Avan­ M. opimus Zonen aamma C. lundgreni - M. testis Zo­ naarsuani graptolittit Canadap avannaani qaqqarsuani nen. Introduetion During the last 15 years numerous graptolites have Llandovery and Wenlock graptolite faunas collected been collected from the upper Llandovery and Wenlock during GGU expeditions to North Greenland were re­ of North Greenland in connection with a major geol­ ported in Dawes (1976), Hurst & Peel (1979), Lane & ogical mapping project organised by the Geological Sur­ Thomas (1979), Lane & Peel (1980), Hurst (1980), Sur­ vey of Greenland (Grønlands Geologiske Undersø­ lyk et al. (1980), Hurst & Surlyk (1982), Dawes & Peel gelse, GGU). The considerable graptolite material in­ (1984) Higgins & Sober (1985), Larsen & Escher cludes many specimens of Cyrtograptus. Previous (1985), Escher & Larsen (1986), Bjerreskov (1986, systematic descriptions of Silurian graptolites from 1989, 1990), Larsen & Escher (1987), Surlyk & Ineson North Greenland are few and only a very limited num­ (1987), and Larsen & Escher (1991). ber of specimens of Cyrtograptus have been described. The faunallists in the above mentioned papers were The earliest reports of Siluriall graptolites are expedi­ all based on the provisional investigations by the pre­ tion records by Etheridge (1878) and Koch (1920), fol­ sent author. Systematic descriptions have been made of lowed by the lists of middle Llandovery faunas from the Silurian graptolite faunas from Washington Land Washington Land by Poulsen (1934). Norford (1967, (Bjerreskov, 1981) including a very few cyrtograptids. 1972) summarised the graptolites recorded during a co­ The present paper deals with the description of the total operative venture between the Geological Survey of material of late Llandovery and Wenlock Cyrtograptus Canada and GGU in Ellesmere Island and western recorded in the collections made by J. M. Hurst, F. North Greenland, and a few cyrtograptids from these Surlyk, P.-H. Larsen, J. C. Escher, F. G. Christensen faunas were described by Jackson & Etherington and J. S. Peel. In addition the graptolite faunas listed in (1969). Wenlock graptolites from Kronprins Christian Norford (1972) and subsequently donated to GGU have Land were mentioned by Lane (1972) and graptolites of been revised. Pridoli age from Hall Land were reported by Berry et al. (1974). Lithostratigraphy and basin development The Lower Palaeozoic Franklinian Basin extended The Peary Land Group was initiated at the Ordo­ from Alaska through the Canadian Arctic Islands and vician-Silurian transition by the onset of the deposition into North Greenland. A deep-water trough within this of westward transported turbidites in the deep-water basin was situated along the northern coast of Green­ trough of the Franklinian Basin succession in North land and was fringed to the south by a shallow shelf Greenland. The turbidites may have derived from the dominated by carbonate sediments. rising Caledonides to the east (Surlyk & Hurst, 1983 The Silurian deep-water c1astic rocks of the Frank­ and Higgins et al. 1991) or from Siberia (McKerrow et linian Basin in North Greenland are inc1uded in the al., 1991). In the late Llandovery the trough expanded Peary Land Group (Fig. 1) which outcrops for 800 km and about 30 000 km2 of carbonate shelf foundered and from Washington Land in the west to Kronprins Chris­ was inundated. The extensive submergence resuited in tian Land in the east. It was erected by Hurst (1980) and the deposition of uniform sequences of hemipelagic described in detail by Hurst & Surlyk (1982). The in­ mudstones and siltstone turbidites covering the shelf formal units employed by Dawes & Peel (1984) and carbonates (Fig. 2). These are referred to the Thors Larsen & Escher (1985) lead to a redefinition in Larsen Fjord Member of the Wulff Land Formation in central & Escher (1987). The lithostratigraphic subdivisions of North Greenland ·and the eastern part of western North the Peary Land Group in the latter paper are these Greenland, the Profilfjeldet Member of the Lauge followed here (Fig. 2; see also Higgins et al., 1991). Koch Land Formation in the east, restricted to Kron- 5'0' 30' Ellesmere Island central North Greenland SHELF DEEP-WATER TROUGH Washington Land Group (Silurian) D Peary Land Group (Silurian) Morris Bugt Group (M. Ord. - L. Sil.) r/J)I Cambro - Ordovician trough sequence Lower Cambrian to Middle PRE- AND POST- FRANKLINIAN Ordovician shelf
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