ARCTIC WL. 43, NO. 4 (DECEMBER 1990) P. 393-403 Beaufort Formation (Late Tertiary) as Seen from Prince Patrick Island, Arctic Canada’ JOHN G. FYLES’ (Received 20 March 1990; accepted in revked form 14 June 1990) ABSTRACT. The Beaufort Formation, in its typearea on Prince Patrick Island, is a single lithostratigraphicunit, a few tens of metres thick, consisting of unlithified sandy deposits of braided rivers. Organicbeds in the sand have yielded more than 200 species of plants and insects and probably originated during the Pliocene, when the area supported coniferous forest. ThisBeaufort unit forms the thin eastern edge of a northwest-thickeningwedge of sand and gravel beneath the western part of the island. These largely unexposed beds,up to several hundred metres thick, include the Beaufort unit and perhaps other older or younger deposits.On the islands northeast and southwest of PrincePatrick Island (MeighenIsland to Banks Island),the name BeaufortFormation has been appliedto similar deposits of late Rrtiary age. Most recorded Beaufort beds on these islands are stratigraphically and paleontologically equivalentto the “type” Beaufort, but a few sites that have been called Beaufort (suchas Duck Hawk Bluffsand the lower unit at Ballast Brook,on Banks Island) differ stratigraphicallyand paleontologically from the “type” Beaufort. This paper recommends that these deposits (probably middle Miocene) and others like them be assigned new stratigraphic names and not be included in the Beaufort Formation as now defined. Informal names Mary Sachs gravel (Duck HawkBluffs) and Ballast Brookbeds are proposed as an initial step. Formal use of the name Beaufort Formation shouldrestricted be to the western Arctic Islands. Key words: Beaufort Formation, Prince Patrick Island, arcticCanada, late Tertiary, Pliocene, plant fossils, paleo-environment, fluvial sediments, stratigraphic nomenclature F&SUM&. La formation de Beaufort, dans sa rtgion type de l’îlePrince Patrick, est uneunitt lithostratigraphiqueunique, de quelques dizaines de mktres d’tpaisseur, composte de stdiments sableux non lithifiCs de cours d’eau anastomosts. Les couches organiques dans le sable ont produit plus de 200 esfices de plantes et d’insectes datant probablement du Pliocbne lorsque la rtgion supportait une foret de conifkres. Cette unitt de Beaufort forme la mince extrtmitt orientale d’un coin de sable et de gravier s’tpaississant vers le nord-ouest au-dessous de la partie occidentale del’île. Cescouches qui affleurent trks peu et qui mesurent jusqu’h plusieurs centainesmktres de d’tpaisseur, comprennent I’unitt de Beaufort et peut-&re d’autresdtpats plus anciens ou plus rkents. Dans les îles au nord-est et au sud-ouest de l’îlePrince Patrick (de ale Meighen h l’île Banks), le nomformation de Beaufort a &t attribut h des dtpdts semblables du ‘Ikrtiairetardif. La plupart des couches de Beaufort relevtsdans ces îles sont stratigraphiquementet paleontologiquement tquivalents au “type” Beaufort, mais quelques sites que l’on a appelts Beaufort (comme les falaises Duck Hawket I’unitt inftrieure au ruisseau Ballastdans l’île Banks) diffkrentpar leur stratigraphie et leur palbntologie due ‘‘type”Beaufort. I1 est recommand6 dans le prhtdocument que ces dCpats et d’autres semblables changent d’appellations stratigraphiqueset soient exclues dela formation de Beaufort. En premiere&ape, il estpropost d’adopter commeappellations non officielles gravier de Mary Sachs (falaises Duck Hawk) et couches du ruisseau Ballast. L’emploi officiel de formation de Beaufort devrait être limit6 aux îles arctiques occidentales. Mots cl&. Formation de Beaufort, île Prince Patrick, Arctique canadien, Rrtiaire tardif, Pliocbne, plantes fossiles, palto-environnement, sediments fluviatiles, nomenclature stratigraphique PEaEPAT. Uwpuawn 6o@opTa Odpa~yerB c-tl mnoeotl odnacrn na ocrpoee npnnc naTpnK ennnoe nnToc7pamrpa@n~ecKoe IlOflpWWleHElG MOUHOCTblo HeCKOflbKO P8C5ITKOB MmOB. COCTOIIuleB U3 HWMTti@HUHpoMHHbIX n8CrlaHbIX OTflOXeHHB pa3BelBmHHbIX pa. BXOIlllUHX B COCTaB 3THX OTflOXeHHfi CIK)IIX OpraHHrlecrMXOCTaTKOB o6HapyXe-HO 60fl- 200 BHLlOB pacrenntl n HaœKouux. 31n cnon @opunpoeanncb. orlBB)tom. B nnnouene. Korna B TOM patlone npon~pacrannxrrotlnbre neca. 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M~Inpennaraeu naTb STHN n npyrnu nono6nbIu OTfloxeHnnu mBbIe crpamrpa@nsecwne na3Bannn n ne Btmownb nx e @opuaum 6O@OpTa npn ee nbuianeu onpenemnnn. B KavecTee neprroro uara npennaraeTcn npnnnme Taxm neo@nunanbnslx na3mnnfi. Kale ‘rpawtl M3pn Cauc’ CYT~CAaK XOK 6na@@c) n ‘mon 6annac~ BpyK‘. npnuenenne H~JBILHM ‘tQopuaunnBO@Opra’ cneayer o@nunanbHo orpannqnrb sana,nnMun ocrpomun KanancKoro Apvrnsecworo apxnnenara. KnloqeabIe mom: @opuaunn 6O@OpTa. ocrpoe npnnc-naTpnK.KanwcKaa Aplcrnra. one eu Tpernsmro nepnona.nnn-ouen. pacmTenbnsle omarm. naneocpena, pesnue ocamn. crpamrpa@nqecKu HouenmaTypa. INTRODUCTION Patrick Island. From his original description,is clear it that Tozer intended the name Beaufort Formationto apply also The Beaufort Formation is of current interest as a source to comparable deposits on other islands. of information on the climate and environment of arctic During the succeeding decade, largely as a result of recon- North America shortly before the onsetof the “arctic” con- naissance surveys byTozer and Thorsteinsson, the name ditions thatnow characterize the region. The presence of theseBeaufort Formationwas indeed appliedto generally similar sands and gravels, containing abundant evidence of former strata on all the islands facing the Arctic Ocean 1)(Fig. from forest conditions,was recognized by explorers the in mid-19th Meighen Islandat Latitude 80°N to the southwesterntip of century. The deposits were formally namedthe Beaufort For- Banks Island at Latitude 72ON (Thorsteinsson, 1961; Thor- mation by Tozer (1956) in the Mould Bay area of Prince steinsson and Tozer, 1959, 1962; Tozer and Thorsteinsson, ‘Geological Survey of Canada Contribution 17090 ’Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario, Canada K1A OE8 @Minister of Supply and Services, Canada, 1990 1 io0 1. DuckHawk Bluffs 2. Ballast Brook 3. Mould Bay 4. DuVernet River Ellesmere Is. Axel Heiberg l\&g Prince I Patrick Is. L 1964). More recently, following paleobotanical assignment Against this background, the present paper reports on of the Beaufort deposits on Banks Island to the Miocene results of investigations designed to improve knowledge of (Hills and Ogilvie,1970; Hills et al., 1974), the name Beaufort the Beaufort Formation in its type area on Prince Patrick Formationhas been extended to Miocene or Neogene Island and makes preliminary comments on correlation. sedimentsin and around the Mackenzie-Beaufortbasin As a consequence of this focus on the type area, where southwest of the original belt and on Ellesmere and Axel the Beaufort Formation is a single distinctive stratigraphic Heiberg islandsto the northeast. In the Mackenzie-Beaufort unit, this paper takesa position on use of the name Beaufort region, the term Beaufort has been appliedby various authors Formation that is more restricted than that taken in some to largely deltaic (marine) sediments of Miocene to Plio- earlier publications. Thus, this paper recommends that the Pleistocene age. In a stratigraphic report on that region, name Beaufort Formation should not be used forErtiary late Dietrich et al. (1985: 617) point out that “use of this term deposits thatare not stratigraphically equivalentto the “type” [i.e., Beaufort Formation]is fraught with many problems,” Beaufort and that other names be used instead. I recognize that “unfortunately no definitiveages have ever been that this proposal is only a first step in rationalizing the determined at the type section” and that “the relationship nomenclature and that there are different conceptsof “the between the Banks Island Beaufort and the type section Beaufort” as seen from other islands (distant from the type remains obscure.” section). L THE BEAUFORT FORMATION / 395 GENERAL CHARACTER OF THE BEAUFORT DEPOSITS woody detritus; 6, clay-rich mud (overbanksuspension deposits); and 7, woody plant detritus,beds of flat-lying logs, The depositsto which Tozer and Thorsteinsson and other sticks, twigs, wood chips, bark,leaves, moss, seeds, rare cones, early workers applied the name Beaufort Formation in the insects (overbank deposits).The facies are interpreted to be western Arctic Islands consist typicallyof unlithified, flat- sandy braided-river deposits. Facies 1 to 4 represent bar and lying quartz-rich sand and gravel and are characterized by channel deposits, with facies 2 the most abundant. Facies the presence of abundant unaltered wood. They