Biological traces are usually preserved at the boundary between two different types of sediment (Fig. 14.1). As traces are generally three-dimensional, the precise morphology may be difficult to ascertain, particularly if there is limited exposure or if only a cross-section of the trace exists. Entire traces preserved in three dimensions are full reliefs. They are usually burrows that have been infilled by later sediment and are
Full relief Filling Original cavity
Convex Concave Hyporelief
Fig. 14.1 Types of trace fossil preservation.
Semirelief Concave Convex Epirelief preserved as casts. Collapsed burrows and traces formed on the surface of the bedding plane are semireliefs. Traces preserved on the top of the bed are epireliefs and those on the lower surface are hyporeliefs.
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