Shallow-Marine Carbonates - Trace Fossils as Indicators of Sedimentary Environments - page 718

morphology, carbonate ramps and rimmed shelves comprise broad and very
shallow facies belts favorable for intense bioturbation, subaerial exposure,
and development of peritidal ichnofauna and trace fossils formed by plant roots.
(3) Carbonate sediments and their high diagenetic potential have a strong
impact on the ichnological signature, resulting in the common occurrence of
bioerosion, chemically etched borings, abundance of firm- and hardgrounds,
and preferential trace-fossil preservation. Early-diagenetic processes can lead
to rapid lithification with trace-fossil accentuation, but can also result in little
to no sediment color contrast between burrows and matrix and bears a high
potential for diagenetic alteration of trace fossils and hosting rocks.
Three ichnofacies are important for the reconstruction of paleoenvironments
on carbonate shelves (or ramps): the Psilonichnus Ichnofacies, the Skolithos
Ichnofacies, and the Cruziana Ichnofacies. In addition, the substrate-controlled
Glossifungites Ichnofacies and the Trypanites Ichnofacies can overprint the
former ones during periods with stagnant or low net-sediment accumulation
(condensation, omission).
The value of ichnological analysis in shallow-marine carbonates is demon-
strated in two case studies, the Middle Ordovician cool-water carbonates of the
St. Petersburg region in Russia and the Middle Triassic epicontinental carbon-
ates in Germany. Furthermore, neoichnological approaches can set a focus on
rimmed carbonate platforms examplified on the Quaternary of the Bahamas,
and on homoclinal carbonate ramps such as the Quaternary of the southern
Arabian Gulf. These examples, with their distinctive ichnocoenoses, are similar
to other carbonate systems elsewhere and may serve as a comparative model for
future investigations around the world.
Ichnological studies of modern carbonate environments and their rock-record
equivalents are far from complete and have much potential for fruitful future
research. Carbonates should not be viewed as the object of a separate subdiscipline
of ichnology. Rather, ichnological information from carbonates should be
combined with that of siliciclastics to achieve a better, more comprehensive
understanding of depositional environments and the sedimentary rock record.
ACKNOWLEDGMENTS
D. K. thanks Statoil for enabling me to perform work in the Middle East and to publish it.
H. A. C. thanks Brian White (Smith College), Jim Carew (College of Charleston), John
Mylroie (Mississippi State University), Tony Martin (Emory University), and numerous other
colleagues who have contributed to my understanding of Bahamian geology and ichnology
over several decades, as well as the many Smith College geology students who assisted with
field studies. I am grateful to the directors and staff of the Gerace Research Centre for support
of my fieldwork on San Salvador and for facilitating much of my work on other islands of the
Bahamas. A. V. D. acknowledges financial support from the Russian Foundation for Basic
Research (Grant 10-05-00848). Jeff Lukasik (Statoil) kindly reviewed the manuscript and
helped to improve this chapter.