Reefs and Mounds - Trace Fossils as Indicators of Sedimentary Environments - page 727

Chapter 24

Reefs and Mounds

Leif Tapanila * ,†,1 and Pat Hutchings ‡
*Department of Geosciences, Idaho State University, Pocatello, Idaho, USA,
† Earth Sciences Division, Idaho Museum of Natural History, Pocatello, Idaho, USA,
‡ Australian Museum, Sydney, New South Wales, Australia
1 Corresponding author: e-mail: [e-mail]

1. INTRODUCTION
Traces in reef environments are produced in hard substrates, including the skel-
etons of reef constructors, associated fauna, microbial carbonate crusts, and
early carbonate cements. A multitude of organisms use mechanical and chem-
ical means to grind, scrape, bore, gouge, and etch hard materials, thus leaving
cavities that record their behavior. A separate process of embedment allows
symbiotic organisms to be “grown around” by a living host skeletonized animal,
thereby making a bioclaustration cavity. These hard-substrate trace fossils in
reefs record two fundamental ethologies: dwelling and grazing structures, the
former include macroborings (

1 mm), and bioclaus-
trations, whereas the latter are simply called “grazings” ( de Gibert et al., 2004;
Tapanila, 2005 ).
The diverse fossil record of reef ecosystems is well studied in terms of evo-
lutionary innovation and biodiversity ( Kiessling et al., 2010 ); yet, the literature
on fossil reef ichnology is sparse when compared to the vast literature on trace
fossils in non-reef depositional settings. Two factors may account for the dif-
ferences: the hard substrates of reefs restrict the types of traces to borings, etch-
ings, and bioclaustrations, and relegate most soft-sediment burrows to off-reef
facies; and observation of traces in reef constructors often requires significant
preparation (cutting, thin sections, epoxy casting, etc.), thus making their study
more deliberate and laboratory intensive. Hard-substrate traces have received
increasing interest from ichnologists ( Sch¨nberg and Tapanila, 2006a ), but
much remains to be understand about the role and distribution of tracemakers
in ancient reefs.

1 mm), microborings (

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