Alternating stripmining and sequestration in deep-sea sediments: The trace fossil Polykampton–an ecologic and ichnotaxonomic evaluation

Abstract

Polykampton Ooster, 1869, comprises deep-sea trace fossils composed of a horizontal median cylindrical tunnel and lateral spreite lobes that alternate on either side of the tunnel and are slightly inclined to bedding. The lobes in P. alpinum Ooster, 1869, are closely spaced and partly shingled. In P. guberanum isp. nov. they are asymmetric and widely spaced. In both ichnospecies, the lobes are generally below the median tunnel. In P. multiflabellatum isp. nov., the lobes extend from outer bents of the median tunnel that runs below the lobes. Polykampton is a structure produced by a "worm"-like organism occupying a deep endobenthic tier. The tracemaker evidently sequestered organic-rich sediment from the seafloor, stored it in the lobes and processed it later by stripmining for feeding, especially in times of low food availability on the seafloor. Polykampton occurs in upper Albian to Oligocene deep-sea, mainly turbiditic deposits.

The trace fossilPolykampton recurvumn. isp. (sequestrichnia) from the Maastrichtian–Paleocene deep-sea deposits of NW Italy

“…The trace fossil Polykampton Ooster, 1869, typified by P. alpinum Ooster, 1869 from the Paleogene flysch deposits of Switzerland, was almost forgotten for more than a century and treated as a monospecific ichnogenus (Häntzschel, 1975;Seilacher, 2007). Discoveries of four new ichnospecies of Polykampton from Cretaceous-Oligocene flysch deposits (Wetzel and Uchman, 1997;Uchman and Rattazzi, 2018;Uchman et al, 2019Uchman et al, , 2020 showed that this ichnogenus is more diverse and widespread than previously thought. In this paper, a sixth named ichnospecies of Polykampton is described and interpreted.…”

“…However, there are no traces of reworking of the lobes. This is a repetitive problem in all ichnospecies of Polykampton, which can be explained by the possibility that the food can be obtained by ingestion without reworking by means of exoenzymes produced by bacteria, as proposed for the other ichnospecies of Polykampton (Uchman and Rattazzi, 2018;Uchman et al, 2019Uchman et al, , 2020. Labile organic matter can be released from particulate organic matter by exoenzymes (e.g., Aller and Cochran, 2019) and leached into the main tunnel.…”

“…8,9). The other ichnospecies of Polykampton show different geometries of the lobes, which are much wider and show a leaf-or petal-like outline (Uchman et al, 2019(Uchman et al, , 2020. They can easily be distinguished from P. recurvum n. isp.…”

“…The formation is gently tectonically deformed, with folds, faults, and internal detachments, especially in the middle and upper parts (Marroni et al, 2002;Levi et al, 2006). Trace fossils of the Pagliaro Formation are very diverse and locally abundant; they are typical of the deep-sea Nereites ichnofacies (Uchman, 2007;Uchman and Rattazzi, 2018;Uchman et al, 2019).…”

Preface: Ichnology, trace fossils and depositional environments

“…Polykampton consists of a central, mainly horizontal, slightly winding tunnel having rather narrow-spaced, petal-like lobes filled with fine-grained, organic-rich material on either side (Uchman et al, 2019). The studied specimens occur within a few tens of meters thick interval in Palaeogene muddy turbidites in the Lesser Caucasus (Georgia).…”