Chapter 10 - Climatic Control of Marine Trace Fossil Distribution

Abstract

Marine trace fossils are not generally considered to be useful as climatic indicators because of their usually long stratigraphic ranges, and because ichnotaxa may have been formed by a variety of different animals. At present, the biota of coastal and shallow-offshore waters display immense differences as one passes from equatorial towards Polar regions. This is compounded by differences in the distributions between the northern and southern hemispheres. However, such differences are less marked in the sediments of past ages, and when trace fossils are selected, differences that might be attributed to climate are relatively few or absent. Trace fossils, with the exception of those utilized in Palaeozoic ichnostratigraphy and footprint stratigraphy, are notable for their long stratigraphic ranges. Sedimentological research has focused on the ichnofacies concept and the relative constancy of the Seilacherian ichnofacies through the Phanerozic. Ichnotaxa are also generally regarded as having a wide geographical extent as well as long time ranges, though there are notable exceptions, as with most traces of Cruziana. However, today, Ophiomorpha is formed only in tropical/subtropical sediments. This appears to have been the case in older sediments, back at least to the early Caenozoic. The burrows of spatangoid echinoids forming Scolicia and Bichordites have a wider range (temperate to tropical). Together, and with regard to a few other trace fossils (Diplocraterion, Lingulichnus, Renichnus, and possibly Cruziana), these two conspicuous trace fossils offer small but significant climatic indications, if certain safeguards regarding identification are observed.