The morphology, ethology and palaeoecology of certain trace fossils from the Jurassic rocks of England

Abstract

ln the present state of knowledge, thirty-one trace-fossil 'species' are known from the English Jurassic: seventeen (55%) are feeding burrows; eleven (36%) are dwelling burrows; two (6%) are crawling trails; one (3%) is a resting impression. No meandering grazing trails occur. Six new 'species' are described;- Arenicolites skeltonensim - basal Upper Lias, Yorkshire. Diplocraterion arkelli - widespread. Diplocraterion statheri - Bajocian, Yorkshire. Glossifungites lymensis - Ellerbeck Bed, Yorkshire. Asterosoma osteri _ Dogger, Yorkshire. Asterosoma multilobatum - Scarborough beds, Yorkshire. Bathymetric zones for the Jurassic sea may be defined in terms of commonly occuring assemblages of trace fossils. Littoral zones consist of monotypic banks of Thalassinoides; arenicolites spp. or Corophioides spp.; or Ophiomoreha. Gyrochorte from the littoral zone show strong orientation and U-turns are common. In sublittoral zones monotypic banks of Rhizocoralliua occur inshore; more varied assemblages, with Teichichnus. Asterosoma and Chondrites, offshore. Zoophycos, diagnostic of still-water neritic zones, is absent. Different trace-fossil ‘species’ are recognised from ironstone, calcareous and well-sorted sandstone “regimes” of sedimentation, though ‘genera’ may be identical. Rhizocorallium jenense and Rhizocorallium cicatricosus occur in ferruginous environments ; Rhizocorallium commune in impure calcareous environments. The stomatopoda are considered likely producers of Rhizocorallium commune. On basis of comparative ecological categories of trace fossils, the system which most strongly resembles the English Jurassic is the bohemian Ordovician. The middle Jurassic of Yorkshire does not compare closely with either the German middle Jurassic or the Northumbrian mamurian. The Jurassic trace-fossil fauna of England is the richest in dwelling and feeding burrows of any system so far described. In the total number of trace-fossil ‘species’ it is exceeded only by the Swiss Flysch.