Ichnological analysis: The common ground between ichnofacies workers and ichnofabric analysts

This work compares the approaches taken by the two schools of applied ichnology (ichnofacies and ichnofabric analysts) and proposes an integrated approach for future improvement. There are many similarities between the two approaches, which mainly differ in the resolution at which ichnological analysis is undertaken. Ichnofabric work is by necessity performed on a bed-by-bed basis and interpreted at a scale consistent with that of the sedimentologist's facies. Ichnofacies studies, in contrast, seldom report bed-by-bed changes in ichnological content, instead highlighting bedset to facies association-scale changes in ichnology through comparison with summary models of ichnological trends. This work highlights the fact that workers from both schools utilize the same tools, with slightly different emphases, to reach their ichnological conclusions. Contention between the two schools has in recent years centred upon which is the better method for studying trace fossils-an artificial construct that detracts from the fact that both are extremely useful to sedimentological and palaeoenvironmental studies. Ichnofabric analysis is in addition, a highly effective means of documenting bioturbated sedimentary fabrics, as the basis for petrophysical studies. Ichnofacies and ichnofabric analysts use the same toolbox of ichnological methods to determine ancient palaeoenvironments-the scale of observation is generally different. but the results closely comparable. The recognition of key stratal surfaces on ichnological grounds is also possible with both methodologies. Ichnofacies analysts look to recognise Glossifungites ichnofacies firmgrounds in offshore mudstones. Ichnofabric studies would look to recognise overprinting of fabrics created by groups of organisms from different palaeoenvironments, but associated with the same key surface. It is proposed that the terms ichnofacies method and ichnofabric analysis are abandoned in favour of a neutral Ichnological Analysis Method, encompassing the approaches and terminology of both to produce a unified, scientifically rigorous, user-friendly methodology. (C) 2008 Elsevier B.V. All rights reserved.