The Morris Bugt Group (Middle Ordovician - Silurian) of North Greenland and its correlatives M. Paul Smith, Martin Sønderholm and Simon J. Tul! The Morris Bugt Group, originally proposed in western North Greenland, is now extendcd across the whole of North Greenland. One new formation, the Kap Jackson Formation, is described; it includes two members, the Gonioceras Bay and Troedsson Cliff Members, which correspond to earlier formations of the same names. In the Washington Land - western Peary Land region the group comprises the Kap Jackson, Cape Calhoun and Aleqatsiaq Fjord Formations. The Børglum River and Turesø Formations of the Peary Land - Kronprins Christian Land region are here added to the group. New data on the age of the formations based on conodont biostratigraphy are given, and correlations with Arctic Canada, East Greenland and Svalbard are discussed. M. P. S., Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB23EQ, England. Present address: Geologisk Museum, øster Voldgade 5-7, DK-1350 København K, Denmark. M. S., Grønlands Geologiske Undersøgelse, øster Voldgade 10, DK-1350 København K, Denmark. S. J. T., Department ofGeology, University ofNoccingham, University Park, Notting­ ham NG72RD, England. Present address: Chapman & Hall, Il New Felter Lane, London EC4P 4EE, England. The Monis Bugt Group was erected by Peel & Hurst three members by Sønderholm & Harland (in prep.) (1980) to encompass the Gonioceras Bay, Troedsson who give full formal descriptions af these members. The Cliff, Cape Calhoun and Aleqatsiaq Fjord Formations. lower member of the Aleqatsiaq Fjord Formation cone­ These formations were originally described from Wash­ lates with the upper part of the Børglum River Forma­ ington Land (Troedsson, 1926, 1928; Koch, 1929a,b; tion. The upper two members af the Aleqatsiaq Fjord Hurst, 1980) but had also been recognised farther to the Formation show a gradual west-east change in litholog­ east in the Hall Land - Wulff Land region (Hurst & ical characteristics, and in western Peary Land grade Peel, 1979; Dawes & Peel, 1984) (figs 1, 2). The Børg­ into the Turesø Formation af Hurst (1984). As a conse­ lum River Formation in the Peary Land - Kronprins quence af this, the Turesø Formation is included in the Christian Land region was recognised to be a correlative extended Morris Bugt Group, despite the differences in of the Morris Bugt Group (Peel, 1982), but was not depositional environment of the two formations. included in the group in the absence of data from the intermediate areas. During 1984 and 1985 the Morris Geological setting Bugt Group was mapped in the Washington Land ­ Freuchen Land area in conjunction with an extensive The sediments of the Morris Bugt Group formed on a conodont sampling programme. FolIowing this, it be­ broad, stable carbonate platform fringing the southern came evident that the group could be extended farther margin of the Franklinian Basin in North Greenland eastwards into the Peary Land - Kronprins Christian (fig. 1). This stable platform, reeognised as stage 5 in Land region. The original division of the lower part of the evolution of the Franklinian Basin (Higgins et al., in the group into the Gonioceras Bay and Troedsson Cliff press), evolved as a consequenee of a regional eustatic Formations was, however, diffieult to recognise in same transgression during late Middle Ordovician time (For­ areas, and these two formations are here treated as tey, 1984) which affected shelf areas in the Canadian members af a new unit, the Kap Jackson Formation. Arctie Archipelago and North Greenland. Formations The Aleqatsiaq Fjord Formation is subdivided into of this stage ean easily be correlated throughout the Rdpp. Grcmlamls gt'ul. U"ders. J43. 5-20 (/9891 60'W 50' 4 30 20'W 8.3'N 82'N o ~ \ '/~---"'" , ~\ r- ~, ~~ W ./ ~Kronprin~ 81' N 'Christian 82' N Land ,-' J JÆ,~ central " western eastern 81'N SHELF TROUGH / ~ Silurian shell j:::<:<::! Silurian trough Store Canyon Mb. Pm:::::::::::::1 Cambrian - Ordovician Irough r Aleqatsiaq Fjord Fm. Kap Ammen Mb. { _ Morris Bugt Group 1Cape Calhoun Fm. Newman Bugt Mb. PRE- AND POST FRANKLINIAN ROCKS , Kap Jackson Fm. f Troedsson Cill Mb. l Gonioceras Bay Mb. Wandel Sea Basin ~ Morris Bugt Group Turesø Fm. (Carbonilerous - Tertiary) { Børglum River Fm. - Proterozoic sediments and basalts ~ Early Cambrian - Middle Ordovician shelf and slope t<:;;:··~~:J Cryslalline basement -./ lault 100 km -"- Lale Ordovician platform margin ~ thrusl ...... ice Fig. I. Simplified geological map of North Greenland, with plaee names used in the tex!. F: Freuchen Land; lCC: J. C. Christensen Land; L: Lauge Koeh Land; ME: Mylius-Erichsen Land; VG: Valdemar Gliickstadt Land; W: Warming Land. 1: Gonioceras Bugt; 2: Troedsson Klipper; 3: Kap Jackson; 4: Kap Calhoun; 5: Moeris Bugt; 6: Aleqatsiaq Fjord; 7: Pentamerus Bjerge; 8: Bessels Fjord; 9: Kap Eisendecher; 10: Kap Ammen; 11: Newman Bugt; 12: Nordenskiold Fjord; 13: J. P. Koch Fjord; 14: Navarana Fjord; 15: Hans Tavsen Iskappe; 16: Odin Fjord; 17: Turesø; 18: Børglum Elv; 19: G. B. Schley Fjord. 7 Franklinian Basin (Christie & Peel, 1977; Peel & Chris­ Morris Bugt Group tie, 1982). The generally dark, monotonously devel­ oped limestones of quiet, relatively deep water, open revised marine aspect referred to the Morris Bugt Group every­ where overlie paie, restricted shaIlow water carbonates History. The Morris Bugt Group was established by which are locally evaporitic and referred to the Ryder Peel & Hurst (1980) to include the Gonioceras Bay, Gletscher Group (fig. 2). The carbonate platform mar­ Troedsson Cliff, Cape Calhoun and Aleqatsiaq Fjord gin to the north (fig. 1) was a scarp-like feature, the Formations in western North Greenland_ The Børglum Navarana Fjord Escarpment (fig_ 1), and separated the River and Turesø Formations of central and eastern platform from a broad slope, which only received very North Greenland, described by Christie & Peel (1977) smaIl amounts of sediment. In the deep water trough and Hurst (1984), are added to the group. The 'dark north of the escarpment, sediments are dominated by weathering limestone and dolomite unit' of Christie & mud and silicious ooze interlayered with turbidites and Ineson (1979) represents the group in the area around carbonate conglomerates (Higgins et al., in press). G. B. Schley Fjord, eastern Peary Land. Peel & Hurst, 1980 THIS PAPER Hurst, 1980 Washington Land - Peary Land - Kronprins western Peary Land Washington Land - Wulff Land Christian Land Peary Ld Gp & Peary Land & >. ~ Washington Washington Land Gp > ... Washington Land Groups r Q) Land Group Øl ~ c: > :J cu o C. ~ .-= "O o ~ c: Store < il)' en cu ::o~ :::J :J w Canyon Mbr ---?-- 0'< AleQatsiaQ AleQatsiaQ Kap Ammen Turesø Fjord Fjord Mbr r--?--- c;) I- c. Newman :J ~ ::o o Bugt o ~g ... ~ I-g Cape Mbr (ij" s- 2 ""SJ Calhoun ~ :::J cu :J tIl < ~ ....J ID c: Cape Calhoun '9. t- ~. (I) / .-= ..,c;) ...o rn o O c: ~ Børglum c: _!!1 "O O Troedsson Troedsson River o.. .!:! o > Cliff Cliff en < o o' "E Mbr t--s::: il)' Ag. :::J O Kap I-:eØl Jackson I-::o A_. - Øl Gonioceras :::J a:: tIl ID Q) Bay ------- ::o =o ...... "O - ~ Gonioceras ) :E Bay Mbr r ~ Cape Webster ;= 1-'"o Ryder Gletscher Group o A s::: il)' Cape Webster I Wandel Valley I Sjælland Fjelde :::J Fig. 2. Stratigraphic correlation scheme for the Morris Bugt Group of North Greenland. A: Aeronian; BR: Black Riveran; ED: Edenian; G: Gamachian; K: Kirkfieldian; MV: Maysvillian; R: Rocklandian; RD: Rhuddanian; RM: Richmondian; S: Sherma­ nian; E: Early; M: Middle; L: Late. 8 Name. After the b.IY. Morris Bugt, on thc west roast of Domimml lilllology. Thc group is prcdominantly com­ WashinglOn Land (fig. I). posed of dark weathcring. cliff-forming. grey-brown monied. dolomitic skeletal limcslOncs (Kap Jackson. TYl" ureu. The coast:11 cliffs around Morris Bugt. Aleqatsiaq Fjord and Børglum Rivcr Fonnations). In the middlc of the group in thc WashinglOn Land ­ ThicklltJS. In Washington Land thc group aHains thick­ Lauge Koch Land area is a recessive unit. the Cape nesses betwccn 700 and 760 m (Hurst. 1980; Peel & Calhoun Formation. which compri.ses greenish weather­ Hurst. 1980). East of Washington Land lhicknesses val)' ing silty limcsloncs. In the Pcary Land - Kronprins betwccn 480 m and 580 m. In Kronprins Christian Land Christian Land region. tne top of the group is romposed a minimum thickncss of approximately 600 m has been of medium-to thick·bcddcd, grey weathering dolomiles rcportcd (Peel. 1985). and limy dolomites, tne Turesa Formation. A hg. J A: Thc Morris Bugl Gmup (Mil) :'1 KOlp Eiscn­ deeher. "CSlern eoasl of Unll L:md. AF: Aleq;.lsiaq Fjord For· mallon: CC: C;,pc C;,lhoun For· m:llion: GB: Goniocer:ls Bay Membcr: KA: Kap Ammen Merntx:r: KJ: Kap Jackson For· malion: NB: Newman Bugl Membcr: RG: Ryder Glelscher Group: SC: Slore C;myon Mem­ her: TC: TrocdS)(Jn Cliff Mem· bcr: WG: Wa~hmglon Land Group. Ilcighl of cliff appro.~i· rnatel) 900 m. B: Alcqalsinq Fjord Fonnalion al Ib eaSlernlTlO51 oUlcrop in Ihc "c~l-f:'cing cliff~ of J. r. Koch Fjord. AF: Alcq:usiaq Fjord Formalion: KJ: Kap Jackson Formalion: WG: Washlllglon und Gmup \VV: Wandel Valley Formalion. Height of cliffs left of glae.er. apprO~lmalel} 850 m. 9 &wrdaries. The group rests ronformably upon the may be divided into Ihe Gonioceras Bay and Troedsson Cape Webster Formalion throughout lhe Washington om Members (formerly formations). Ihe Cape Cal­ Land - western Freuchen Land area. In the Lauge Koch houn Formation and lhe Aleqalsiaq Fjord Formation. Land - Peary Land region it ronformably overlies the which is divided inlo the Newman Bugt. Kap Ammen Vestervig Elv Membcr of lhe Wandel Valley Formalion and Store Canyon Membcrs (Sonderholm & Harland. (Sonderholm & Due. 1985: Peel & Smilh. 1988) whilsl in prcp.). The Cape Calhoun Formalion Ihins easlwards in Valdemar GlUcksladt Land and Kronprins Chrislian and wedges oul in the region of Nordenski61d Fjord: in Land Ihe group rests ronformably upon the Sjælland Freuchen Land and western Peary Land Ihe Aleqatsiaq Fjelde Formation (Ineson el al.• 1986).