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Authors: Speranza, F.* 
Di Chiara, A.* 
Rotolo, Silvio Giuseppe* 
Title: Correlation of welded ignimbrites on Pantelleria (Strait of Sicily) using paleomagnetism
Issue Date: Mar-2012
Series/Report no.: 2/74 (2012)
DOI: 10.1007/s00445-011-0521-9
Keywords: Pantelleria
Caldera formation
Paleosecular variation of the geomagnetic field
Subject Classification04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous 
04. Solid Earth::04.04. Geology::04.04.08. Sediments: dating, processes, transport 
04. Solid Earth::04.04. Geology::04.04.10. Stratigraphy 
04. Solid Earth::04.04. Geology::04.04.11. Instruments and techniques 
04. Solid Earth::04.05. Geomagnetism::04.05.99. General or miscellaneous 
04. Solid Earth::04.05. Geomagnetism::04.05.02. Geomagnetic field variations and reversals 
04. Solid Earth::04.05. Geomagnetism::04.05.03. Global and regional models 
04. Solid Earth::04.05. Geomagnetism::04.05.06. Paleomagnetism 
04. Solid Earth::04.05. Geomagnetism::04.05.07. Rock magnetism 
04. Solid Earth::04.05. Geomagnetism::04.05.08. Instruments and techniques 
Abstract: Although the oldest volcanic rocks exposed at Pantelleria (Strait of Sicily) are older than 300 ka, most of the island is covered by the 45–50 ka Green Tuff ignimbrite, thought to be related to the Cinque Denti caldera, and younger lavas and scoria cones. Pre-50 ka rocks (predominantly rheomorphic ignimbrites) are exposed at isolated sea cliffs, and their stratigraphy and chronology are not completely resolved. Based on volcanic stratigraphy and K/Ar dating, it has been proposed that the older La Vecchia caldera is related to ignimbrite Q (114 ka), and that ignimbrites F, D, and Z (106, 94, and 79 ka, respectively) were erupted after caldera formation. We report here the paleomagnetic directions obtained from 23 sites in ignimbrite P (133 ka) and four younger ignimbrites, and from an uncorrelated (and loosely dated) welded lithic breccia thought to record a caldera-forming eruption. The paleosecular variation of the geomagnetic field recorded by ignimbrites is used as correlative tool, with an estimated time resolution in the order of 100 years. We find that ignimbrites D and Z correspond, in good agreement with recent Ar/Ar ages constraining the D/Z eruption to 87 ka. The welded lithic breccia correlates with a thinner breccia lying just below ignimbrite P at another locality, implying that collapse of the La Vecchia caldera took place at ~130–160 ka. This caldera was subsequently buried by ignimbrites P, Q, F, and D/Z. Paleomagnetic data also show that the northern caldera margin underwent a ~10° west–northwest (outwards) tilting after emplacement of ignimbrite P, possibly recording magma resurgence in the crust.
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