Continental trace fossils and museum exhibits - Geological Curators ...

Figure 1. Field photograph of an outcrop in the Miocene Pelleu Island Formation, White Limestone Group, Jamaicadepicting pronounced overhang of bedding plane surfaces (see Blissett and Pickerill 2004 for details on the ichnotaxa).geological collecting, and which are adequatelydescribed elsewhere (e.g., Rixon 1976). Further, werecommend Feldmann et al. (1989) for techniques ofpreparation, which are not discussed herein. Illustratedspecimens are deposited in the collections of theNationaal Natuurhistorisch Museum, Leiden, TheNetherlands (RGM), and the Geology Museum,University of the West Indies, Mona, Kingston,Jamaica (UWIGM).Collecting specimens oriented parallel ornear-parallel to stratificationThis group embraces surface tracks and trails, certainburrows and burrow systems, and surface etchings,borings, etc., on hardground surfaces. It also includesopen infaunal burrow systems cast on the sole of thesucceeding bed in turbidites and tempestites,commonly found in, for example, Paleodictyon. Suchtraces are best seen at sites where extensive beddingplanes are exposed (tops of beds, except where theyhave been inverted by tectonic activity) or in extensivevertical sections with more or less pronouncedoverhangs (e.g., Figure 1). In many cases these arethe easiest of trace fossils to recognise, yet they arenot necessarily the easiest to collect, such as wherethe trace fossil is situated in the centre of a surface orthe bed is more than a few tens of mm in thickness. Anextensive bedding surface (e.g., Figure 2) with avariety of traces and other sedimentary structures canbe a spectacular display specimen, even if it has to becollected as a jigsaw of separate fragments for reassembly,broken up in the field by heavy hammeringor perhaps even a rock saw; a less destructivemethodology would be to cast the surface in the field.Important data, apart from that normally collected inthe field (Tucker 1982), includes labelling the topand bottom of the slab(s) (there may be differentassemblages of traces on each surface), compassorientation, and numbering the separate pieces of a‘jigsaw’ that can be related to an explanatory sketch(for suggestions of how to glue a rock ‘jigsaw’ backtogether, see Wolberg 1989). The parts of a ‘jigsaw’may include pieces of burrow infill which have‘popped off’ of a bedding plane.Collecting in situ specimens from bedding planes islikely to involve intensive labour, using a heavyhammer and/or a rocksaw. It is easier (and lessdestructive to an exposure) to look for loose slabs at-206-