Abstract

This report summarizes the results obtained by applying modal petrographic analysis to distinguish the siliciclastic turbidite successions of the Paleocene-Upper Oligocene Caneloto Complex and of the Upper Oligocene-Lower Miocene (?) Macigno in the Cinque Terre and lower Magra valley area. The Canetolo Complex is a structuralk unit tectonically intervening between the underlying Tuscan Nappe and the overlying Ligurid Units. In the studied area the Canetolo Complex is represented by marly calcareous (Groppo delVescovo Limestone), shaly calcareous (Argille e Calcari di Canetolo) and arenaceous (Ponte Bratica Sandstone and Petrignacola Sandstone) lithostratigraphic units (Abbate, 1969; Braga and Marchetti, 1970; Brage et alii, 1972). The new data show that in the arenaceous lithologies of these stratigraphic units i) the k-feldspar is absent and ii) the lithic fragments are adundant. Despite these similarities, the appreciable differences in the volcanic lithics and in the relative abundance of feldspars allow to distinguish the Ponte Bratica Sandstone and the Petrignacola Sandstone. The petrographic facies of Macigno, the thick turbidite unit at the top of the Tuscan Nappe, is appreciably different and suggests that in the Oligocene the turbidite sedimentation of the Tuscan Nappe and of the Canetolo Complex derived from different supply areas and filled separated basins.

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