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Probable root structures and associated trace fossils from the Lower Pleistocene calcarenites of Favignana Island, southern Italy... 755
bioturbated (Fig. 8C, D). The lower calcarenites are overlain by
horizontally bedded coarse calcarenites (Fig. 8D, F). E.
rectibrachiatus initiates from two more or less even disconti-
nuities (Figs. 8B, D–F and 9): the first is located between the
two calcarenites and a second one, 30 cm higher, is located
within the horizontally bedded calcarenite. The discontinuities
are marked by a thin brownish crust. We interpret these discon-
tinuities as representing horizons of emergence, other features
of which have been destroyed by subsequent erosion. The
brownish crust may be an initial pozdol-type palaeosol (cf.
Arndorff, 1993) or a penetrative calcrete associated with a
higher emergence horizon that was subsequently truncated by
erosion. More problematic is the colonization surface for
Faviradixus robustus, because overlying sediments are not
preserved at its localities. The candidate surface is the disconti-
nuity between the Calabrian calcarenites and the Tyrrhenian
strata. However, the Tyrrhenian deposits display a characteris-
tic lithology, which would be expected in the fillings of the
structures – which, however, are identical to the surrounding
Calabrian calcarenites (Fig. 6). This does not exclude this dis-
continuity as a continental colonization surface, because colo-
nization by plants might take place at the beginning of forma-
tion of this discontinuity, before sedimentation of the
Tyrrhenian deposits, when the Calabrian calcarenites were
erosionally remobilized. Alternatively, the continental coloni-
zation surface does not need to be hard. In Pleistocene carbon-
ates of Tunisia, Plaziat and Mahmoudi (1990) observed empty
root tubules, 2–20 cm in diameter, that start from aeolianite and
continue down for up to 2–5 m. It seems that the tubules repre-
sent void tubes after roots in a loose sediment. The consistency
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Acknowledgements. This research has been supported by
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