Antiche linee di riva tardo-Quaternarie sull'isola di Lipari (Isole Eolie) e mobilità verticale dell'apparato vulcanico = Late-quaternary raised shorelines at Lipari (Aeolian Islands): implications for the vertical motion of the volcanic apparatus
In: Bollettino della Società geologica italiana, Jg. 120 (2001) ; Nr. 2-3, S. 165-185
Zeitschriftenaufsatz / Fach: Geowissenschaften
Rektorat und Verwaltung » Rektorat
The occurrence of raised ancient marine deposits and forms on the Lipari Island has long been well known (KELLER, 1967; PICHLER, 1968). Five orders of marine terraces have been recognized between 45 and 3 metres asl and related to Tyrrhenian and post-Tyrrhenian highstands mostly on the basis of their elevation (KELLER, 1967). More recent studies have attempted to date these raised shorelines by means of both the relationships between marine terraces and the volcanic substratum and the radiometric dating of fossils (RADTKE, 1986; BERNASCONI & FERRINI, 1988). Recently, a detailed stratigraphical reconstruction of the relationships between volcanic products and raised shorelines has been presented for the nearby Panarea Island (LUCCHI et alii, 1999). This reconstruction, based on several stratigraphical, chronological and geomorphological data, allowed the correlation of four orders of ancient shorelines with Late Pleistocene highstands and the evaluation of the vertical motion of the volcanic apparatus during the last 125 ka. The same approach was adopted at Lipari to define the stratigraphical succession of the raised shorelines cropping out mainly along its western coast and to estimate the rate of vertical motion of the volcanic apparatus during the Late Quaternary. The island of Lipari represents the emerged portion of a wider volcanic apparatus rising from the sea floor (total elevation of about 2000 metres) and belonging to the central sector of the Aeolian arc (fig. 1). The volcanic activity ranges from 223 ka to the Present as derived by K/Ar (GILLOT & VILLARI, 1980; GILLOT, 1987; CRISCI et alii, 1991), Ar/Ar (LUCCHI, 2000a) e 14C (CRISCI et alii, 1983; LOSITO 1989) dating. The stratigraphy of the island (fig. 2b) consists of four synthems (Piano Grande, Pianoconte, Valle Muria and Vallone Fiume Bianco) and one informal unit (Paleolipari). The Paleolipari informal unit includes the older volcanic products, whose age range from 223′0.9 ka to 130′10 ka, represented by basaltic-andesite to andesite lava flows and pyroclastics. The Piano Grande Synthem embraces basaltic-andesite to andesite lava flows and pyroclastics related to the first phase of activity ol the M.S. Angelo (M.S. Angelol lithosome, dated 127′8 ka) and M. Chirica (M. Chirical lithosome) centres. The volcanic products of the Pianoconte Synthem are related to the final building stages of the M.S. Angelo (M.S. Angelo 2-3 lithosomes) and M. Chirica (M. Chirica 2 lithosome) centres. The M.S. Angelo 2 lithosome comprises the so-called « leaf-bearing pyroclastics» (RICCI LUCCHI et alii, 1988) and the andesitic lavas known as « cordierite-bearing lavas » (formazione Pulera, dated 104′3.5 and 105′19 ka), whereas the final andesitic pyroclastic breccias and lava flows (dated 92′10 ka) are related to the M.S. Angelo 3 lithosome. The M. Chirica 2 lithosome includes the andesitic lava flows outcropping in the upper part of the cliff along the western side of the island. The Valle Muria Synthem comprises rhyolitic pumiceous pyroclastics and lava flows related to volcanic activity ranging in age between about 40 and 16.8′2 ka (fig. 2); these volcanics are mainly located in the southern sector of the island. Some pyroclastic ash layers, known as Brown Tuffs (CRISCI et alii, 1983; LOSITO, 1989), are interbedded within these volcanics, and in particular represent the bottom and the top of the stratigraphical succession of the Valle Muria Synthem.