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

Because of fundamental differences between trace fossils and body fossils, ichnologic nomenclature is beset with difficulties. Foremost is inconsistent treatment by the International Commission on Zoological Nomenclature (lack of sanction for post-1930 names, confusion over the "rule of priority") and inadequate curation of type specimens. However, ichnologists have contributed their own problems via inadequate diagnoses and descriptions, misconceptions of ichnologic and taxonomic principles, proliferation of names and failure to engage in true monographic revisions. All these difficulties are illustrated in a thorough reevaluation of the ichnogenera Planolites Nicholson and Palaeophycus Hall. Contrary to a popular but ill-founded scheme in which these ichnogenera are differentiated simply on the presence or absence of branches, Planolites is an unlined burrow infilled with sediments having textural and fabricational characters unlike those of the host rock, whereas Palaeophycus is a lined burrow filled with sediments typically identical to those of the surrounding matrix. Planolites represents active backfilling of sediment in an ephemeral burrow constructed by a mobile deposit feeder and Palaeophycus represents passive sedimentation within an open dwelling burrow constructed by a predaceous or suspension-feeding animal. In addition to ichnological nomenclature and ethology, the ramifications are important in paleoecology, sedimentology and diagenetic studies. Currently recognized ichnospecies of Planolites include P. montanus Richter, P. beverleyensis (Billings) and P. annularis Walcott. Those of Palaeophycus include P. heberti (Saporta), P. tubularis Hall, P. striatus Hall, P. sulcatus (Miller and Dyer) and P. alternatus n. ichnosp.

Trace fossil nomenclature and the Planolites-Palaeophycus dilemma

http://earthdynamics.org/papers-ED/in-press/2013-Torsvik-Cocks-GondwanaResearch-AM.pdf

Gondwana from top to base in space and time

Antarctica — Before and after Gondwana

/pdf/the-rio-de-la-plata-craton-and-the-assembly-of-sw-gondwana-i07zm9nuyp.pdf

The Río de la Plata craton and the assembly of SW Gondwana

Proterozoic–Early Paleozoic evolution in western South America—a discussion

The Pacific Gondwana margin in the late Neoproterozoic–early Paleozoic: Detrital zircon U–Pb ages from metasediments in northwest Argentina reveal their maximum age, provenance and tectonic setting

During the Late Precambrian to Early Cambrian a large basin with a homogeneous psammitic-pelitic sediment fill existed in the area of the NW-Argentine Andes. It is now exposed in different tectonic levels. This basin of meridional elongation was situated on a stable continental margin at the western edge of the Brazilian shield. It was underlain by segmented older continental crust. According to the modal and chemical composition of the greywackes and subgreywackes a predominant metasedimentary source may be supposed. Four clastic facies types indicate a transport by gravity currents within a submarine fan system, while massive red pelites represent cut-off periods, and rare carbonates deposition on rises. The gravity currents derived from easterly directions. The sedimentation age is proved by a rich ichnofauna and some medusoid impressions.

The Puncoviscana trough — a large basin of Late Precambrian to Early Cambrian age on the pacific edge of the Brazilian shield

Floodplain deposits of the Permian Laguna Polino Member (La Golondrina Formation) of southern Patagonia, Argentina, contain a moderate diversity invertebrate ichnofauna. This member consists of up to 500 m of ripple cross-laminated and trough cross-bedded, medium-grained sandstone and mudstone, with some conglomerate. It records sedimentation in braided fluvial environments with moderate channel sinuosity. The system was characterized by the development of multistory channels, transverse or linguoid bars, and levees. At the Laguna Grande locality, trace fossils were recovered from current-rippled, very fine-grained muddy sandstone beds formed in a pond adjacent to the levee. The ichnofauna consists of a mixed pascichnia, repichnia, and domichnia assemblage composed of Cochlichnus anguineus, Ctenopholeus kutscheri, Helminthoidichnites tenuis, Helminthopsis abeli, and Palaeophycus striatus. These low-energy ponds were more suitable for development of benthic fauna and preservation of ichnofossils than were fluvial channels and point bars. Accordingly, preservation of distinct trace fossil-bearing pond horizons within an otherwise unfossiliferous fluvial succession may be regarded as taphonomic and colonization windows. The colonization history of these beds can be traced through the study of cross-cutting and substrate relationships. Detailed ichnologic analysis suggests the following succession: 1) large Cochlichnus tracemakers colonizing transitional soupgrounds to softgrounds; 2) large and small Cochlichnus, Helminthopsis and Helminthoidichnites formed in softgrounds; and 3) Palaeophycus and Ctenopholeus emplaced in transitional soft to firm substrates. The colonization sequence suggests an ecologic replacement of a surface mobile fauna dominated by nematodes, nematomorphs, and larval insects by a more stationary infauna consisting of adult insects as a result of increasing consolidation. Presence of Ctenopholeus is significant because it represents the second report of this ichnogenus and the first from nonmarine settings.

Permian nonmarine invertebrate trace fossils from southern Patagonia, Argentina; ichnologic signatures of substrate consolidation and colonization sequences

Florencio Gilberto Aceñolaza

Papers

Proterozoic–Early Paleozoic evolution in western South America—a discussion

The Pacific Gondwana margin in the late Neoproterozoic–early Paleozoic: Detrital zircon U–Pb ages from metasediments in northwest Argentina reveal their maximum age, provenance and tectonic setting

The Puncoviscana trough — a large basin of Late Precambrian to Early Cambrian age on the pacific edge of the Brazilian shield

Permian nonmarine invertebrate trace fossils from southern Patagonia, Argentina; ichnologic signatures of substrate consolidation and colonization sequences

Geología del noroeste argentino