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Rend. Online Soc. Geol. It., Vol. 17 (2011) - (DOI 10.3301/ROL.2011.17)

Sedimentology and ichnology of the lower part of the Saraceno Formation (Cretaceous?, Miocene?) (northern Ionian Calabria)

C. Caruso (*), D. Natoli (*) & M. Sonnino (*)

 

(*) Dipartimento di Scienze della Terra, Università degli Studi della Calabria, 87036 Arcavacata di Rende (CS).
claudia.caruso@unical.it; meco81it@hotmail.it; m.sonnino@unical.it


Abstract  

The Saraceno Fm. (SELLI, 1962) outcrops mainly in the Saraceno Valley and in the Satanasso Valley (Northern Calabria, Ionian coast). It is about 600 m thick (DI STASO & GIARDINO, 2002) and it is subdivided into four main lithofacies (SONNINO, 1984; D’ALESSANDRO et alii, 1986) which show a lithological evolution from marls (sometimes with chert nodules) to calcarenites, to siliciclastic sandstones and shale, that is an evolution from shelf to deep sea fan deposits (SONNINO, 1984). The age of this Fm. is still debated; recent studies indicate that the Saraceno Fm. has a Miocene age (DI STASO & GIARDINO, 2002), while according to TORRICELLI & AMORE (2003) the Saraceno Fm. is referred to Upper Cretaceous. The Saraceno Fm. is characterized by richness in trace fossils. D’ALESSANDRO et alii (1986) describe nineteen ichnospecies, which are very well recognizable and preservated in the Saraceno Fm.: Chondrites (five ichnospecies), Cosmorhaphe lobata, Fucusopsis isp. (now named Halopoa), Helminthoida labyrinthica (now named Nereites irregularis), Paleodictyon isp., Palaeophycus tubularis, Phycosiphon incertum, Rhizocorallium  irregulare, Scolicia  isp., Taenidium annulatum (now named Cladichnus fischeri), Muensteria isp. (later named Taenidium satanassi and now named T. dieslingi), Teichichnus isp., Thalassinoides isp., Zoophycos (two ichnospecies).
Very recent studies executed by the authors, confirm that the lower part of the Saraceno Fm., outcropping in the homonymous valley, considered by TORRICELLI & AMORE (2003) as the type area of this Fm., shows proximal features of a shallow marine paleoenvironment, i.e. hummocky cross stratification and symmetrical ripples, already identifi ed by D’ALESSANDRO et alii (1986). A detailed stratigraphic sections, of about 55 m in thickness, have been recently measured.
The misured outcrop consist of an irregular alternation of calcarenites (sometimes rich in cherts), calcilutite and shales, which is completely overturned. The trend is a general decrease of grain size, from the bottom toward the top. The calcarenitic beds show a normal grain size selection and a gibbous and bioturbated bottom. The top of the calcarenitic layers are constituted by a laminated siltstone, interpreted as a diluted turbiditic current or as a distal diluted tempestites (A. UCHMAN, pers. comm.). The shale parts are not uniform: colours range from green to red to grey and to black; this change in colours could be due to the fluctuation in oxygen content (A. UCHMAN, pers. comm.). Almost all shaly intervals are characterized by an allocthonous and an autochthonous shale. In the autochthonous one (black shale), small passive white fi lled Chondrites isp., small Planolites isp. and Trichichnus isp. are present (= anossic episodes). In the gray shale (stratigraphically located just below the black one) bigger Chondrites isp., Planolites isp. and also Thalassinoides isp. are present (= more oxygenation). So the background sediment is intensely bioturbated. New ichnological observations of the outcrop misured have allowed to recognize: Chondrites intricatus, Chondrites targionii, Chondrites stellaris, Taenidium
dieslingi, Rhizocorallium isp., Zoophycos isp., Trichichnus isp., Pilichnus isp., ?Phymatoderma isp., and Planolites isp. Particularly, in the debris nearly the rocky cliff, a beautiful and rare specimen of Chondrites, recently deposited in the Geological Museum of the Jagiellonian University, Kraków (Poland) is been collected (UCHMAN et alii, in press). It shows similarities with other specimens referred to Late Cretaceous formations (i.e. Campanian Khalenberger Formation); this discovery could confirm the dating of TORRICELLI & AMORE (2003), at least for the lower part of the Saraceno Fm.

 

KEY WORDS: Saraceno  Formation,  hummocky  cross stratifications,  ichnofossils,  shelf  deposits,  Calabria, Southern Italy.

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