Abstract

This paper provides information on the main lithological and stratigraphical framework of the continental Val Daone Conglomerate (VDC) which crops out eastwards of the central Southern Alps, along the Giudicarie Belt (western Trentino), from the NE part of the Early Pemian Collio Basin to the west, up to the Val Rendena to the east. The prevalent whitish to greyish alluvial fan and braided river deposits of this formation composed dominantly of vein quartz and volcanic fragments and reaching a maximum thickness of about 100 m and little more rest above a marked regional unconformity (corresponding to the lower boundary of the Permian 2nd tectonosedimentary megacycle emphasised by the recent literature) and paraconformably (?) below the fluvial red beds of the Verrucano Lombardo/Val Gardena Sandstone, generally related to a Late Permian age. Recently, in Val Daone, a thin grey siltstone layer included in the coarser fluvial bodies of the unit has yielded abundant and significant palynological associations. According to Pittau et alii (in print), it shows a close similarity with the continental red beds of the well known "Saxonian or Saxono-Thuringian Leouve facies" of the Dome de Barrot (French Maritime-Alps), bearing a miospore assemblage characterised by Lueckisporites virrkiae, Corissacites sp., Crucisaccites (closely resembling to Crucisaccites variosulcatus Djupina, 1971) and a large number of other palynomorphs. Therefore, according again to Pittau et alli (in print), the similarity of these species suggests the extension of the stratigraphic potential of this Crucisaccites variosulcatus Lueckisporites virrkiae zone to Western Europe. Furthermore,due to a careful review from the same authors, on the whole the discovered microfossils span, in different worldwide areas, from latest Kazanian to slightly younger times. However, in Val Daone and its surrounds, the paper's authors are generally inclined to confine them to a Middle Permian age, and thus to connect the onset of the discussed "Conglomerate" with the tectonic activity of the so-called "Mid-Permian Episodes" (Deroin & Bonin, 2003). In the eastern Southern Alps, from Comelico-Cadore to the Karawanken Mountains, the VDC can also be regarded as a Mid-Permian lateral unit of the Sesto (Sexten) Conglomerate and the Tarvisio tarvis Breccia, even though these basal bodies of the 2nd Permian tectonosedimentary megacycle include different lithologies and cannot necessarily be interpreted as quite synchronous.

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