Systematic ichnology of the Mabou and Cumberland groups (Carboniferous) of western Cape Breton Island, eastern Canada, 2: surface markings

Abstract

Carboniferous (Namurian-Westphalian A) strata of the Mabou and Cumberland groups outcrop extensively in western Cape Breton Island. As well as a diverse collection of burrows, trails, pits, and coprolites described previ ously, numerous surface marks, mostly trackways, were encountered in these strata: Diplichnites cf. logananus (Marsh) Smith, Appendage Marks (types A and B), an "Arthropod Resting" Trace, Horn-shaped Surface Traces, and Vertebrate Trackways (types A, B, C, D, E, and F).Des strates du Carbonif&re (Namurien-Westphalien A) des groupes de Mabou et de Cumberland aifleurent sur une surface dtendue dans l'ouest de l 'ile du Cap-Breton. On rel&ve en outre dans ces strates une collection diversifide de terriers, de pistes, de trous et de coprolites ddcrits antdrieurement; un grand nombre de marques au sol, en majeure partie des pistes, comme celles du Diplichnites cf. logananus (Marsh) [Traduit par la rddaction] I n t r o d u c t io nThis paper describes and discusses several o f the trace fossils encountered at various localities in western Cape Breton Island (Fig. 1). The numerous surface markings described (pri marily trades and trackways) occur in Carboniferous (Namurian-W estphalian A) M abou and Cumberland Group strata that have been confidently inferred to be the products of fluvial, floodplain, and lacustrine sedimentation in half grabens main tained by a transtensional tectonic regime (Keighley and Pickerill, 1996a). The surface markings may occur exclusive of, or asso ciated with, the trace fossils already described from these strata by Keighley and Pickerill (1997); Baird (personal com munication, 1989Baird (personal com munication, ,1994 and his co-workers have collected additional material that remains undescribed. Future work will assess the palaeoenvironmental distribution of our specimens.N o m e n c l a t u r a l p r o b l e m s and t e r m in o l o g y Before presenting our taxonomic classification o f the trace fossils from the study area, it is necessary to first comment on the chaotic taxonomic nom enclature that exists for both •Current Address: Department of Earth Sciences, University of Liverpool, Brownlow Street, Liverpool, England, L69 3BX vertebrate and invertebrate trackways and explain the prin ciples behind our nomenclatural decisions. As stated in Keighley and Pickerill (1996b, 1997) and Pickerill and Keighley (1997), an ichnotaxon can only be formally nam ed (and hence diag nosed) from distinguishing morphological features, follow ing the guidelines o f the International Code o f Zoological Nomenclature (I.C.Z.N., 1985). Criteria such as (a) the phy togeny of the producer, (b) stratigraphic limitation of the trace fossil, or (c) the environm ent in which the trace fossil was produced, are not criteria that can be directly, or objectively, observed or proven in a type specimen. Therefore they re main hypothetical concepts and so cannot be used to pro vide a name based upon the 'Principle o f the Name-bearing Type' (I.C.Z.N., 1985, p. xiii, Article lb-1). Specificall...

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