Ichnostratigraphy - Trace Fossils as Indicators of Sedimentary Environments - page 190

Chapter 7
Ichnostratigraphy
M. Gabriela M ´ ngano, * ,1 Luis A. Buatois * and Robert B. MacNaughton †
*Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan,
Canada, † Geological Survey of Canada, Natural Resources Canada, Calgary, Alberta, Canada
1 Corresponding author: e-mail: [e-mail]
1. INTRODUCTION
Many ichnotaxa have long temporal ranges and occur in a narrow range of
facies. For these reasons, trace fossils have not been used extensively in bio-
stratigraphic studies. Trace fossils can provide invaluable biostratigraphic data,
however, in situations where other fossil age control is limited or lacking. Vari-
ous approaches to ichnostratigraphy (trace-fossil biostratigraphy) have been
documented. Some trace fossils preserve specific fingerprints of their producers
that yield biostratigraphic information, as in the long tradition of using tetrapod
footprints to date continental successions ( Lockley, 1998 ) or in the use of
Cruziana and Rusophycus ichnospecies to date non-fossiliferous Paleozoic
sandstones ( Seilacher, 1970, 1990, 1992 ). Complex trace fossils can have bio-
stratigraphic significance due to a behavioral pattern that has a limited strati-
graphic range (e.g., ichnospecies of Oldhamia or arthrophycids) or due to a
consistent first appearance datum (e.g., first occurrence of Treptichnus pedum ).
Beyond these applications, even long-ranging ichnotaxa can provide useful age
controls based on their documented first appearances, as is the case with
Ediacaran to early Cambrian trace-fossil biozones.
In this chapter, we briefly review the utility of trace fossils to establish rel-
ative ages in both marine and continental settings. Readers desiring a more
in-depth discussion of the principles and applications of ichnostratigraphy
can consult a number of published reviews ( Buatois and M´ngano, 2011;
Crimes, 1975; MacNaughton, 2007 ). Ichnostratigraphy has been applied pri-
marily in siliciclastic strata, where the preservation potential of stratigraphically
useful ichnotaxa is relatively high, and this is reflected in our discussion. In car-
bonates, by contrast, late diagenetic processes tend to reduce the diversity of
ichnocoenoses and hamper preservation of fine morphological details required
for detailed ichnostratigraphy (e.g., Narbonne, 1984 ).