Rend. Online Soc. Geol. It., Vol. 21 (2012), pp. 893-895, 2 figs., 1 tab. © Società Geologica Italiana, Roma 2012 893 Key words: coarse-chaotic deposits, turbidite systems, provenance, Oligocene-Miocene, Northern Apennines. INTRODUCTION Coarse-disorganised and chaotic deposits (clasts > 5 cm) are generally produced by mass-flows like debris flows. They reveal a great importance when included in deep-sea turbidite systems, because they represent particular flow events. They generally occur inside very proximal turbidite systems, whereas are unusual for distal and high-efficiency ones. The significance and importance of the coarse-disorganised and chaotic deposits associated with the turbidite systems have been often undervalued, also due to their subordinate recurrence. Based on their sedimentological features, stratigraphy and composition, they can furnish a lot of relevant informations about: triggering mechanisms and events, transport and depositional processes, flow-transformation processes, palaeogeography and composition of the sourcing and feeding systems, features of the shallower basin, of the depositional systems and of the slope, physiography of the deep-sea basin, efficiency of the turbidite system, etc. To the regard, the diachronous foredeep turbidite systems of the Late Oligocene-Early Miocene of the Northern Apennines, represent a good chance to observe such deposits and to consider their significance. Moreover it is some more intriguer due to the role that these deposits can play about the palaeogeographic/geodynamic reconstruction of such still enigmatic sector of the Northern Apennines. The turbidite systems objects of this research are the so-called “Macigno costiero” and “Macigno del Chianti” of the Southern Tuscany, ranging in thickness respectively about 600 meters and 1500- 2000 meters. They are represented by several facies associations, with the occurrence of rare coarse-disorganised levels. These turbidite successions include thick olistostromes (submarine slides coming from the orogenic units stack) and coarse- disorganised deposits, these latter subject of this work. The restricted areas where such deposits crop out are (from the west, Fig. 1): La Spezia-Cinque Terre, Baratti-Piombino, Calafuria and Punta Ala along the Tyrrhenian coast (“Macigno costiero”), Chianni, Val d’Orcia and Chianti Mts in the tuscan inland (“Macigno del Chianti”). Some of these have been studied by sedimentological or compositional point of views by a few researchers (i.e. PATACCA, 1973; FERRINI & PANDELI, 1983; CORNAMUSINI et alii, 2002). DATA All the studied coarse disorganised-chaotic deposits show similar textures, with minor differences in terms of thickness and lateral extent, clast/matrix ratio, mud amount of the matrix, shape and grain-size of the clasts, sedimentary structures. The texture is Characters and significance of the coarse-chaotic deposits within the deep-sea turbidite systems of the Northern Apennines (Oligocene- Miocene, Macigno Fm.) GIANLUCA CORNAMUSINI (*) Fig. 1 – Sketch map with the outcrops (stars) of the coarse-chaotic deposits within the Macigno Fm: SP – La Spezia-Cinque Terre; ML – Livornesi Mts; CH – Chianni; BA – Baratti; PA – Punta Ala; VO – Orcia Valley; RP – Rapolano Terme-Chianti Mts; CA – Cavriglia-Chianti Mts; CI – Cintoia- Chianti Mts. _________________________ (*) Dipartimento di Scienze della Terra, Università di Siena (*) Centro di Geotecnologie, Università di Siena