The Ichnofabric Concept - Trace Fossils as Indicators of Sedimentary Environments - page 135

Chapter 5
The Ichnofabric Concept
Allan A. Ekdale, * ,1 Richard G. Bromley † and Dirk Knaust ‡
*Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah, USA,
† Geological Museum—SNM, Copenhagen, Denmark, ‡ Statoil ASA, Stavanger, Norway
1 Corresponding author: e-mail: [e-mail]
1. INTRODUCTION
Most people would agree that ichnology is the study of traces and trace fossils,
which of course is quite true, at least in part. But ichnology includes much more
than just identifying and interpreting trace fossils. Ichnology broadly encom-
passes the preservable and preserved effects that active organisms (animals,
plants, bacteria, etc.) produce in the substrate (both unconsolidated and lithi-
fied). It includes analytical approaches to understanding the processes of bio-
turbation and bioerosion, as well as the products of those processes.
While recognition and description of identifiable trace fossils are of para-
mount importance in ichnological studies, the taphonomic overprint and pres-
ervation mode of trace fossils also hold great value for interpreting the post-
depositional history of sedimentary units. Even more broadly, recognition of
characteristic ways in which the texture and fabric of a sediment has been
affected by organism activity offers significant sedimentological, paleoecolog-
ical and even stratigraphical information. This is the arena of ichnofabric.
2. EARLY DEVELOPMENT OF THE CONCEPT
The fabric of a bolt of fine cloth, or an ornate oriental carpet, or an intricately
constructed tapestry is composed of many multihued, multitextured, inter-
twined threads that create an exquisite whole. A single thread does not a tapestry
make. Yet, the omission of a single thread may alter the appearance and possi-
bly even the overall character of the fabric, and removal of one thread may
cause the entire fabric to unravel. The fabric of a sedimentary deposit is not only
composed of many different threads (involving the mineralogy, size, shape, ori-
entation, distribution, etc. of grains and matrix) but also constructed by the com-
plex interplay of numerous physical and biological processes. Fabrics are not
woven instantaneously, and so the fabric of a sedimentary deposit (especially