Oligocene trace fossils from temporary fluvial plain ponds: An example from the Freshwater Molasse of Switzerland

Abstract

Numerous invertebrate trace fossils and small rare vertebrate tracks are reported and described from the Upper Oligocene deposits of the Lower Freshwater Molasse in eastern Switzerland. They are commonly accompanied by mud-cracks, raindrops, and plant remains, mostly leaves. The invertebrate trace fossils were produced by different animals, mostly insect larvae, nematodes, and probably by molluscs, in desiccating pools on a fluvial plain of a braided river. The trace fossil assemblage differs from the Scoyenia ichnofacies which is typical for terrestrial fluvial plain environment. Instead, it resembles the impoverished Mermia ichnofacies which is probably common but poorly known in this environment. This ichnofacies corresponds to a low energy environment, most probably to fluvial plain ponds. ZUSAMMENFASSUNGAus der oberoligozänen Süsswasser-Molasse der Ostschweiz werden zahlreiche Spurenfossilien von Invertebraten und einige Spuren kleiner Vertebraten beschrieben. Diese Spuren sind häufig mit Trockenrissen, Abdrücken von Regentropfen und Pflanzenresten, vor allem Blättern, assoziiert. Verschiedene Organismen, meist Insektenlarven, Nematoden und möglicherweise Mollusken, haben die Invertebraten-Spuren in austrocknenden Tümpeln auf einer Schwemmlandebene hinterlassen. Die beschriebene Assoziation von Spurenfossilien unterscheidet sich von der Scoyenia Ichnofazies, die für Ablagerungen im Bereich von Schwemmlandebenen typisch ist. Statt dessen gleicht sie einer verarmten Mermia Ichnofazies, die aus diesem Ablagerungsraum wenig bekannt ist, aber wahrscheinlich häufig auftritt. Diese Ichnofazies entspricht einem Ablagerungsraum geringer Energie, wie er in Tümpeln auf einer Flussebene vorkommt.

Eocene flora and trace fossils from the Hruby Regiel section in the Tatra Mountains (Poland): Taxonomic revision of the Wiktor Kuźniar fossil plant collection

“…It resembles the category of "leaf underminings" being small burrows produced preferentially under leaves for food and protection (for similar interpretation in fresh-water sediments see Uchman et al 2004) and preserved preferentially as the leaf blade forms a stable "wall" preventing against rapid collapse in normal softground conditions.…”

Paleohydrological significance of trace fossil distribution in Oligocene fluvial-fan-to-lacustrine systems of the Ebro Basin, Spain

“…8 tracemakers, experiments demonstrate that nematode worms do produce this type of trails (see Uchman et al, 2004 for references).…”

“…Note that amplitude is used here as commonly used in mathematics; other authors (e.g., Elliot, 1985;Uchman et al, 2004) used it to refer to the distance between opposite wave crests measured perpendicularly to the main axis of the trace, which actually is twice the amplitude (2A). The λ/A ratio varies between 3.5 and 8.7 with an average of 5.7.…”

Comments on the paper “Reconnaissance of Upper Jurassic Morrison Formation ichnofossils, Rocky Mountain Region, USA: Paleoenvironmental, stratigraphic, and paleoclimatic significance of terrestrial and freshwater ichnocoenoses” by Stephen T. Hasiotis

“…Buatois and Mán-gano (1995) summarized occurrences of the Mermia ichnofacies from the Carboniferous to the Pleistocene and discussed the temporal and spatial distribution of continental ichnofaunas and addressed the problem of how the Mermia ichnofacies evolved with geological time. Interestingly, after its original definition, the Mermia ichnofacies has been identified in a significant number of Mesozoic (Metz, 1996(Metz, , 2000Melchor, 2004) and Cenozoic (Uchman and Alvaro, 2000;Uchman et al, 2004;Ebnother and Elliott, 2004) units. The incorrect notion that the Mermia ichnofacies is exclusively Palaeozoic already has been suggested by Hasiotis (2002).…”