Trace Fossils
Abstract
This book serves as an up-to-date introduction, as well as overview to modern trace fossil research and covers nearly all of the essential aspects of modern ichnology. Divided into three section, Trace Fossils covers the historical background and concepts of ichnology, on-going research problems, and indications about the possible future growth of the discipline and potential connections to other fields. This work is intended for a broad audience of geological and biological scientists. Workers new to the field could get a sense of the main concepts of ichnology and a clear idea of how trace fossil research is conducted. Scientists in related disciplines could find potential uses for trace fossils in their fields. And, established workers could use the book to check on the progress of their particular brand of ichnology. By design, there is something here for novice and veteran, insider and outsider, and for the biologically-oriented workers and for the sedimentary geologists.
... There is a tradition in the study of trace fossils based on traces left in soft deposits, to identify them mostly as expressing animal behaviour (VALLON et al., 2016), frequently concentrating on movement (PLOTNICK, 2012), although both movement and growth in response to environmental stimuli are also known for plants and microorganisms. In the present contribution we found that the traces we describe originate from the behaviour of a specialized group of microboring organisms (BERTLING et al., 2006;MILLER III, 2007a), while accepting the general definition of behaviour from the MerriamWebster Dictionary as "the way that a person, an animal, a substance" (or a microorganism) "behaves in a particular situation or under particular conditions" (endolithic). We confirm the view of BROMLEY & NIELSEN (2015) who noted that bioerosion structures constitute 'readymade fossils,' suggesting that the onset of fossilization be equated with the death of the bioeroding tracemaker. ...
... We hope this type of work will eventually support identifying extant deep sea euendolithic tracemakers as well as any ancient body fossils that may be found within their traces. Behaviour may change during growth, development, and the functional differentiation of individual trace makers, resulting in production of a variety of trace shapes, especially in those characterized as compound complex traces (MILLER III, 2007a). In addition to morphological differentiation of the tracemaking organism (oncogeny), how the trace was formed (ichnogeny) needs to be identified and discussed. ...
... Euendolithic microborings may also constitute a cumulative historical record, involving more than one microboring organism. Such cases would constitute composite, rather than compound traces, which require recognition but do not require naming (MILLER III, 2007a). Although some individual ichnotaxa illustrated here are located within larger groups of different ichnotaxa in a few photomicrographs, we carefully selected photomicrographs that unambiguously illustrate the type for each ichnotaxon described to ensure clarity. ...
Microboring traces in carbonate skeletal fragments deposited in aphotic depths of the oceans are studied, evaluated, and described with respect to their marine ecology and palaeoecology as well as ichnotaxonomy. Sand-size deep sea sediment particles dredged from depths ranging between 600 and 3266 m of the Bermuda Pedestal, Central Atlantic Ocean, the Florida Escarpment, the Mediterranean Sea, the Red Sea and the Indian Ocean were studied. Following ichnological rules, trace fossils are described as ichnogenera and ichnospecies, defined as products of organismal behaviour. This, in our view, refers to the growth habit of microboring organisms in response to environmental stimuli within the substrate they penetrate. The problem of palaeobathymetry is discussed in conjunction with the distinction between light-dependent and light independent microboring organisms, with the emphasis on the latter. We considered this distinction to be important because only the light-dependent microborers have been recognized as indicators of ancient depositional depths, whereas the light-independent ones are expected to occur at any depth, subject to the availability of organic nutrients. Microboring organisms often leave morphologically similar traces due to convergent evolution. Their responses may change during their life cycle; they may produce different traces when pursuing their vegetative vs. reproductive functions. New ichnotaxa are described. All are regarded as organotrophs given their aphotic zone deep sea origin. This work presents the most complete set of deep sea microbial euendolith traces, to date.
... Because these parameters may occur at specific water depths, it should not be surprising to find nearshore assemblages in offshore sediments, and vice versa. For example, the Skolithos ichnofacies, which is typical of nearshore settings, may occur in offshore tempestites or deep-marine turbidites, and the Cruziana ichnofacies, which is typical of lower shoreface to offshore deposits, may also be present in shallower settings, such as intertidal flats on tide-influenced shorelines (Miller, 2007). In recent decades, ichnologists have proposed many new ichnofacies from continental and marine environments, some of which are considered well founded, some are retained as mutually equivalent, and still others are considered invalid categories (see Buatois and Mangano, 2011 for a detailed discussion). ...
... Complex trace fossils include large, elaborate structures that appear to indicate long occupation and control of environmental factors (MILLER 2007), and commonly display very complex morphology that cannot be logically attributed to a single type of simple behaviour . They often consist of compound elements, comprising intergradational forms in which one ichnotaxon gradually or directly passes into another, or may contain composite trace fossils, resulting from interpenetration of the same and/or different tracemakers (PICKERILL 1994). ...
The ichnogenusBalanoglossites
Mägdefrau, 1932 is re-described from its type area and is interpreted as part of a complex trace fossil comprising both burrow and boring components. The type ichnospecies,B. triadicus, consists of predominantly deep U- or Y-shaped tunnel elements, whereasB. ramosus n. isp. encompasses irregularly ramified galleries. Both ichnospecies occur frequently in firmground and hardground substrates with sporadic epikarst features. In the underlying softground, they may integrate intoLabyrintichnus terrerensis
Uchman & Álvaro, 2000, a network of irregular galleries and communicating shafts. On the omission surface, the tunnels are linked to elongated or winding grooves in hard or firm substrates. Further elements of the complex trace fossil include lobate burrows similar toZoophycos andRhizocorallium, mainly occurring in firmground and softground, shallow to deep U-shaped pouches and winding tunnels (Maeandropolydora sulcans
Voigt, 1965) in hard and firm substrates. Finally, some tunnel portions and well preserved top surfaces of the ichnofabrics are scattered with the faecal pelletsCoprulus oblongus
Mayer, 1952.C. oblongus has a rounded shape and a homogeneous structure and belongs to the Coprulidae n. ichnofam. Based on the numerous fingerprints preserved in the complex trace fossil, polychaete worms are identified as possible tracemakers. This is in accordance with the close combination of borings and burrows, a tunnel system highly variable in shape and size, blind ending side-branches and tunnel terminations, association with scolecodonts and exceptionally preserved polychaete remains. In addition, different commensals may have contributed to the modification of the complex trace fossil.
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