Taphonomy and time-averaging of marine shelly faunas

Ichnology is the study of traces created in the substrate by living organisms. This is the first book to systematically cover basic concepts and applications in both paleobiology and sedimentology, bridging the gap between the two main facets of the field. It emphasizes the importance of understanding ecologic controls on benthic fauna distribution and the role of burrowing organisms in changing their environments. A detailed analysis of the ichnology of a range of depositional environments is presented using examples from the Precambrian to the recent, and the use of trace fossils in facies analysis and sequence stratigraphy is discussed. The potential for biogenic structures to provide valuable information and solve problems in a wide range of fields is also highlighted. An invaluable resource for researchers and graduate students in paleontology, sedimentology and sequence stratigraphy, this book will also be of interest to industry professionals working in petroleum geoscience.

Ichnology: Organism-Substrate Interactions in Space and Time

Palaeoecology and evolution of marine hard substrate communities

Abstract About 65 ichnogenera and a number of bioerosional trace fossils that are unnamed are catalogued with respect to their stratigraphic ranges. In most cases, corresponding stratigraphic studies of the trace-makers are not possible because (1) the rank of taxonomic ascription is too high to be meaningful and (2) not all members of a high taxon are bioeroders. For example, radulation traces of chitons are known from Jurassic to Recent, whereas chitons have a body fossil record back to the Early Palaeozoic. Similarly, whereas the round drill-hole Oichnus paraboloides is known from Cambrian to Recent, the only identified makers of this trace fossil, naticid gastropods, range from Cretaceous to Recent. The stratigraphic ranges of bioerosion ichnotaxa emphasize the two marine revolutions of the Phanerozoic: there is marked increase in diversification during the Ordovician-Devonian interval and since the Triassic.

A stratigraphy of marine bioerosion

Different kinds of experimental calcareous substrates were exposed at Lee Stocking Island (Bahamas) and One Tree Island (Great Barrier Reef, Australia) to study which endolithic bacteria, algae and fungi contribute to bioerosion and what their bioerosion rates are. The sites at Lee Stocking Island were several leeward shallow water and several windward shallow and deep-water positions (from the Acropora palmata reef at 2 m down to 275 m depth). At One Tree Island, the experiments were conducted in patch reefs treated with P and N to study the influence of mineral nutrients on bioerosion. The exposure periods ranged from 1 week to 2 years. The micritic carbonate substrates exposed on Lee Stocking Island contained 6 genera with 15 species of cyanobacteria, green and red algae, and different kinds of microendolithic heterotrophs. The mean values of bioerosion rates measured between 1 to 2 g/m 2 /y at 275 m and 520 g/m 2 /y at one of the leeward sites. The composition of the endolithic community and the bioerosion rates changed over time. At One Tree Island, shell pieces of Tridacna were used as substrate exposed for 5 months to endolith activity. Five genera and 6 species of cyanobacteria, green and red algae and different kinds of heterotrophic microendoliths were found with bioerosion rates of 20–30 g/m 2 /y. There are differences in abundance of taxa between Lee Stocking Island and One Tree Island. The introduction of nutrients had no apparent impact on the microborer community. Controlling factors for the distribution and abundance of microborers are mainly light, but also the kind of substrate and, possibly, the biogeographic position. The results support the paleoecological importance of microendoliths.

Experimental studies on microbial bioerosion at Lee Stocking Island, Bahamas and One Tree Island, Great Barrier Reef, Australia: implications for paleoecological reconstructions

Shell bioerosion in high-latitude low-energy environments: Firths of Clyde and Lorne, Scotland

Limpet grazing on Cretaceous algal-bored ammonites

Trace fossils assemblage and depositional environment of Turonian calcareous sandstones in the southern Benue Trough, Nigeria

Depth distribution of endolithic algae from the Firth of Clyde: implications for delineation and subdivision of the photic zone

Synopsis Micro-borings attributed to the chlorophytes Phaeophila and Eugomontia and the cyanophytes Hyella and Plectonema are recorded from shells in the early Holocene sediments of Irvine. The basal gravel beds generally show a higher density of algal borings and a greater percentage of algal-infested shells than the overlying sand unit. Borings of Eugomontia and the sponge Cliona and the calcareous algae Melobesia and Lithothamnium , are restricted to the basal gravel. Pockets of broken Lithothamnium observed in the sand unit are interpreted as reworked. By comparison with Recent micro-endolithic algal assemblages in the Firth of Clyde, it is concluded that the basal gravel formed in a low energy marine environment about 10 m deep: the overlying sands represent a true raised beach.

Etie Ben Akpan

Papers

Shell bioerosion in high-latitude low-energy environments: Firths of Clyde and Lorne, Scotland

Limpet grazing on Cretaceous algal-bored ammonites

Trace fossils assemblage and depositional environment of Turonian calcareous sandstones in the southern Benue Trough, Nigeria

Depth distribution of endolithic algae from the Firth of Clyde: implications for delineation and subdivision of the photic zone

Depth of deposition of Early Holocene raised sediments at Irvine deduced from algal borings in mollusc shells