Trace Fossils in Siluro-Devonian Tidal Flat to Distal Basin Slope Carbonates of Arctic Canada: ABSTRACT

Abstract

Upper Silurian and Lower Devonian carbonates of Somerset, Griffith, Cornwallis, and Devon Islands (Arctic Canada) were deposited under conditions which ranged from tidal flat in the south to basin slope in the north. Trace fossils occur commonly in this succession. Planolites, Palaeophycos, Chondrites, and Skolithos are ubiquitous throughout the sequence. Seven commonly occurring ichnogenera exhibit restricted environmental conditions: Polarichnus is confined to tidal flat deposits, Zoophycos and Pilichnia are most common in deep subtidal shelf and upper basin slope deposits, and Phycodes, Lockeia, Taenidium, and Cruziana occur predominantly in basin slope deposits. Seven other ichnogenera, Arenicolites, Arthraria, Cochlichnus, cf. Furculosus, Helicodromites, Teichichnus, and cf. Thalassinoides, occur only very rarely. Trace fossil assemblages of the tidal flat and subtidal shelf carbonates are broadly similar to the Skolithos and Cruziana ichnofacies reported from environmentally equivalent siliciclastic deposits. Similarly, the assemblage of the deep subtidal-upper basin slope carbonates resembles the environmentally equivalent Zoophycos ichnofacies. In contrast, the assemblage of the basin slope carbonates comprises abundant resting and feeding traces (Cruziana ichnofacies) whereas assemblages of siliciclastic slope deposits are dominated by complex grazing traces and graphoglyptids (Nereites ichnofacies). The relative scarcity of arthropod traces throughout this carbonate sequence probably reflects diagenetic alternation of bedding surfaces. End_of_Article - Last_Page 524------------