Late Ordovician-Early Silurian Trace Fossils from the Matapedia Group, Tobique River, Western New Brunswick, Canada

LATE ORDOVICIAN-EARLY SILURIAN TRACE FOSSILS FROM THE MATAPEDIA GROUP, TOBIQUE RIVER, WESTERN NEW BRUNSWICK, CANADA R.K. Pi ekeri 11 Department of Geology, U niversity of New Brunswick Fredericton, New Brunswick, E3B 5A3 L.R. Fyffe Department of Forest, Mines and Energy, Mineral Resources D ivision Fredericton, New Brunswick, E3B 5H1 W.H. Forbes Department of Geology, U niversity of Maine at Presque Isle Maine 04769 Date Received November 1, 1986 Date Accepted February 8, 1987 Late Ordovician-Early Silurian flysch slope deposits of the Matapedia Group of the Matapedia Basin on the lobique River, western New Brunswick. Canada, contain 13 ichnogenera (15 ichnospecies), namely:- Chondrites ichnospp.. Cochi ichnus anguineus, Dictyodora scotica, Dictyodora tenuis, Dimorphichnus ichnosp., Ciockerichnus ichnosp., Cordia marina, Helminthopsis ichnosp., Muensteria ichnosp., Neonereites uniserialis, Nereites jacksoni, Paiaeophycus tubularis, Syncoprulus pharmaceus and Yakutatia emersoni. Of these, Dimorphichnus, Muensteria and Dictyodora have never previously been recorded in the Matapedia Basin and Dictyodora is recorded for the first time in North America. The total assemblage represents the most diverse ichnocoenosis yet recorded from Paleozoic slope deposits. Sin: la rlviAre Tobique, dans l'ouest du Nouveau-Brunswick, au Canada, les flyschs du Groupe de MatapAdia appartenant au Bassin de MatapAdia, dAposAs en contexte de talus et d'age tardiordovicien A Aosilurien, ont livrA 13 ichnogenres (15 ichnoespAces), savoir; Chondrites ichnospp., Cochlichnus anguineus, Dictyodora scotica, Dictyodora tenuis, Dimorphichnus ichnosp., Ciockerichnus ichnosp., Gordia marina, Helminthopsis ichnosp., Muensteria ichnosp., Neonereites uniseriai is, Nereites jacksoni, Paiaeophycus tubularis, Syncoprulus pharmaceus and Yakutatia emersoni. Parmi ceux-ci, Dimophichnus, Muensteria et Dictyodora n'ont jamais AtA signalAs dans le Bassin de MatapAdia; il sagit, de plus, de la premier decouverte de Dictyodora en AmArique du Nord. Au total, 1 1 assemblage reprAsente 1'ichnocAnose la plus diverse jamais docuraentAe dans les dApots de talus de PalAozoique. [Traduit par le journal] INTRODUCTION on the planned location of a trout and salmon aquaculture center, construction of which is Detailed systematic ichnological studies of deep imminent and will result in coverage of the exposed water flysch strata of Mesozoic age have been strata. In view of this, the purpose of this paper undertaken in several parts of the world (e.g., is therefore to document, particularly taxonomi- Macsotay, 1967; Ksiazkiewicz, 1970, 1977; Tanaka, cally, the trace fossils discovered at the site and 1971; Kern and Warme, 1974; Crimes et el., 1981; to comment on their importance not only with etc.). In contrast. Paleozoic, particularly lower respect to strata of the Matapedia Basin but also Paleozoic studies remain poorly documented, with with respect to previous studies in coeval strata the notable exceptions of, for example, Crimes and trace fossil diversity models. (1970), Acenolaza (1978), Pickerill (1981), and Benton (1982a). The importance of detailed taxo LOCATION AND GEOLOGICAL BACKGROUND nomic studies of deep-water lower Paleozoic trace fossils cannot be overemphasized. For example, the The Matapedia Basin of Fyffe et a l. (1981), paucity of such studies, as noted by Pickerill previously termed the Aroostook-Matapedia Carbonate (1980), has resulted in Phanerozoic trace fossil Belt by Ayrton et a l. (1969) and the Aroostook diversity models (Seilacher, 1974, 1977; Frey and Anticlinorium by Pavlides (1968) and Rodgers Seilacher, 1980) which are not in accord with the (1970), is a narrow tectonostratigraphic zone observed data. Over the last decade one of us extending from eastern Gaspe through New Brunswick (R.K.P.) has been involved with the collection and and into northeastern Maine (Fig. 1) where it description of trace fossils from the middle merges with the Merrimack Trough (Bradley, 1983). Ordovician to lower Silurian flysch succession of Strata in this basin are middle Ordovician-Early the Matapedia Basin (see below) of New Brunswick Silurian in age and have been assigned various and Quebec. Recent work in part of this basin in group and, or, formational names at different loca the Perth-Andover area of New Brunswick (Fig. 1, tions along its length. In Gaspe, strata are Pickerill, 1986) revealed an extremely important referred to the late middle Ordovician-Early site with respect to trace fossils contained in Silurian Honorat and Matapedia groups, the latter these strata. Unfortunately, the site is situated including the Late Ordovician-Early Silurian White MARITIME SEDIMENTS AND ATLANTIC GEOLOGY 23. 77-88 (1987) 0711-1150/87/020077-12$2.80/0 78 PICKERILL ET AL. LEGEND LOWER OEVON1 AN - Wopske Formation ry"77| Interbedded medium grey siItstone and light grey, parallel, and cross- laminated quortzose sandstone S ILU R IAN -Perham Group [—r~— i Green ond grey calcareous to non- i i I calcareous siltstoneand sandstone with thin orgillites UPPER ORDOVICIAN TO LOWER S IL U R IA N - Matopedia Group ll | | Thinly interbedded grey calcareous PI "I" I slate,grey to black ophanitic lime stone ond fine-grained sandstone 4y y Bedding, tops known (overturned) / / Bedding, tops unknown ( inclined, ve rtico l} y f Slaty cleovoge {inclined, vertical) 'v Fau it © Fossil locality (HE) Route number 0 12 3 km Fig. 1. Location and simplified geological map of the Perth-Andover area, western New Brunswick. Note that in the small inset map, the Matapedia Basin is outlined by a stippled ornament. Head and Pabos formations (Nowlan, 1983). In New thick ankeritic limestones which are generally Brunswick the strata include the late middle massive but rarely are parallel-laminated. On Ordovician-Early Silurian Grog Brook and Matapedia outcrop scale these interbeds are apparently groups (St. Peter, 1977; Nowlan, 1983) while in laterally continuous though may be attenuated due Maine they are referred to as the Madawaska Lake to tectonism. They are sharp-based and exhibit Formation of at least middle Ordovician age (Roy sharp and clearly defined upper surfaces. Rare and Mencher, 1976) and an overlying Carys Mills interbeds of slightly more coarser grained, less Formation of latest Ashgillian or earliest Silurian calcareous siltstones or fine-grained sandstones age (Rickards and Riva, 1981). Trace fossils are also present and are parallel- or cross- described in this paper were located in western New laminated. The internal arrangement of laminae, Brunswick just north of the Perth-Andover area parallel-laminated passing vertically into cross- (Fig. 1) and were collected from the Matapedia laminated sets, indicates deposition of such units Group whose equivalent to the west in eastern Maine from decelerating flows. Some of these units are is the Carys Mills Formation. The location of the normally graded and several are composite. The site is on the eastern bank of the Tobique River units are planar based but with no obvious erosive approximately 1.5 km upstream from its confluence features and exhibit sharply defined upper with the Saint John River (Fig. 1), though as noted surfaces. The relative importance of the three in the introduction, this site will be unavailable lithotypes is difficult to estimate, even semi- in the near future as a consequence of construction quantitatively, because of structural, exposure and of an acquaculture center. No fossils are present weathering problems; however, calcareous argillites in the Matapedia Group at this location and there and interbedded ankeritic limestones are very fore the assignment of a Late Ordovician predominent with only rare interbeds of calcareous (Ashgillian) to Early Silurian age is based on siltstones. correlation with equivalent graptolite-bearing To date no systematic or detailed sedimentologi- strata found elsewhere in the Matapedia Basin cal studies of the Matapedia Group have been under (e.g., Rickards and Riva, 1981). taken, although existing literature suggests The Matapedia Group consists of delicately deposition of the strata in a deep-water marine laminated calcareous argillites, individual laminae environment. St. Peter (1977) suggested deposition typically being <1 mm in thickness, laterally in a bathyal or abyssal environment whereas persistent or (very rarely) impersistent, rarely Stringer and Pickerill (1980) suggested deposition lenticular, and separated by <2 cm=thick (typically on a slope marginal to the northeast trending <1 cm-thick) dark, relatively calcite- and Miramichi Anticlinorium (see Fyffe et a l., 1981) to ankerite-poor argillites. Interbedded with these the southeast. The more thickly bedded calcareous parallel-laminated calcareous argillites are 1-2 cm siltstones exhibit evidence of deposition from MARITIME SEDIMENTS AND ATLANTIC GEOLOGY 79 decelerating flows, probably turbidite flows. The Muensteria ichnosp.; Neonereites uniseralis trace fossils indicate deposition in deep-water, Seilacher, I960; Nereites jacksoni Emmons, 1844; but most have previously been reported from other Palaeophycus tubular is Hall, 1847; Syncoprulus sequences in both slope and basinal regimes. The pharmaceus Richter and Richter, 1939; Yakutatia interbedded calcareous argillites and ankeritic emersoni (Ulrich, 1904). The trace fossils were limestones are not indicative of any specific collected from the extensive talus material at the depositional environment, as they do not possess site and therefore were not located in situ, though

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