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Geological Quarterly, 2012, 56 (4): 745–756
DOI: http://dx.doi.org/10.7306/gq.1052

Probable root structures and associated trace fossils from the Lower Pleistocene
calcarenites of Favignana Island, southern Italy: dilemmas of interpretation

Alfred UCHMAN, Andrzej ŚLĄCZKA and Pietro RENDA

Uchman A., Ślączka A. and Renda P. (2012) – Probable root structures and associated trace fossils from the Lower Pleistocene
calcarenites of the Favignana Island, southern Italy: dilemmas of interpretation. Geol. Quart., 56 (4): 745–756, doi: 10.7306/gq.1052

Two types of large, branched structures from the Lower Pleistocene (Calabrian) high-energy calcarenites of Favignana Island are de-
scribed: Faviradixus robustus gen. et sp. nov. and Egadiradixus rectibrachiatus gen. et sp. nov. They may be interpreted as root struc-
tures of large plants, i.e., trees and trees or shrubs, respectively. The former taxon co-occurs with the marine animal trace fossils
Ophiomorpha nodosa, Ophiomorpha isp., Thalassinoides isp. and Beaconites isp. The interpretation as root structures although tentative
is probable and can be related to short emergence episodes for the formation of E. rectibrachiatus or to longer emergence, responsible for
the discontinuity at the base of the overlying Tyrrhenian deposits, for F. robustus. Calcified root mats of smaller plants associated with
the Tyrrhenian or younger emergence surfaces are common.

Alfred Uchman and Andrzej Ślączka, Institute of Geological Sciences, Jagiellonian University, Oleandry 2a, 30-063 Kraków, Poland,
e-mails: alfred.uchman@uj.edu.pl, andrzej.slaczka@uj.edu.pl; Pietro Renda, Dipartimento di Geologia, Universita di Palermo, Via
Archirafi 20/22, 90100 Palermo, Italy, e-mail: renda@unipa.it (received: April 24, 2012; accepted: September 12, 2012; first published
online: November 5, 2012).

Key words: ichnology, root structures, burrows, carbonates, Quaternary, Mediterranean Sea.

INTRODUCTION burrows. The presence of a coaly lining is a common feature of
roots (Sarjeant, 1975; Pieńkowski, 2004), but it may be oxi-
Distinguishing between animal trace fossils and root struc- dized and or consumed by detrivores. This feature is extremely
tures is not always easy (see Boyd, 1975; Sarjeant, 1975; rare in carbonate deposits.
Klappa, 1980; Gregory and Campbell, 2003), mainly because
the morphology of fossil root systems is much less understood In the Lower Pleistocene shallow-marine calcarenites of
than that of animal trace fossils. Klappa (1980), Curran (1984), Favignana Island, southern Italy (Figs. 1 and 2), two types of
and Ekdale et al. (1984) provided criteria for the distinction be- large branched structures are present: (1) horizontal to oblique,
tween roots and animal burrows; however, their application is and (2) vertical. Their interpretation as crustacean burrows or
not always straight forward. Moreover, the primary morphol- other animal trace fossils (A. Uchman) appeared problematic as
ogy of roots can be considerably transformed diagenetically, shown by discussion during the Workshop on Crustacean
leading to formation of different mimicking features. For in- Bioturbation – Fossil and Recent in Lepe, Spain, in 2010
stance, a cementation envelope (root tubule according to (Gibert et al., 2010). Therefore, their alternative interpretation
Klappa, 1980) along the roots can mimic a burrow wall. More- as root structures was considered, but some problems of such
over, root structures can co-occur with marine animal burrows, interpretation remain unsolved. Their description and interpre-
for instance, when roots penetrate into exposed soft marine tation are the main aim of this paper. They can be considered in
sediments. In such cases carbonate sediments are usually the terms of ichnotaxonomy because root structures are not
quickly lithified, but roots can etch even very hard limestones only body fossils (e.g., Pieńkowski, 2004) but also structures of
and deeply penetrate the rock (James and Choquette,1989; A. recurrent shape, resulting from deformation of the substrate by
Uchman, pers. observations). Nevertheless, meniscate fillings a living organism (see Sarjeant, 1975; Bertling et al., 2006).
or constructed granulated walls are obvious features of animal Such practice has been adopted for root structures in Pleisto-
cene calcarenites in Italy by D’Alessandro and Iannone (1982).
However, casts of voids after roots can be also considered as