Trace fossils from the type ‘Etcheminian Series’ (Lower Cambrian Ratcliffe Brook Formation), Saint John area, New Brunswick, Canada

Abstract

AbstractSelected trace fossils from the type section of the ‘Etcheminian Series’ at Hanford Brook are described and illustrated:Helmithoidichnites tenuisFitch,Monocraterionsp.,Palaeophycus tubularisHall,Planolitessp.,Psammichnites gigasMatthew,Subphyllochordra?sp.,Taphrhelminthoida dailyin. sp., andTaphrhelminthopsiscf.T. circularisCrimes et al. The assemblage has elements comparable to those in other Lower Cambrian sequences. It formed in shallow water settings, is mainly endichnial, and contains systematic, guided meander traces that are generally characteristic of deep-water environments in younger sequences; this may be related to global environmental changes early in the Palaeozoic. The guided meander traces are characterized morphometrically, using an image analyser: the meander systems exhibit a strongly bimodal distribution of morphologic elements, reflecting a well developed taxis (sense for position, direction, and distance) during trace production. The method of morphometric analysis has potential for characterizing trace fossils generally, somewhat like X-ray diffractograms characterize minerals.