Paleomagnetic evidence for low-temperature emplacement of the phreatomagmatic Peperino Albano ignimbrite (Colli Albani volcano, Central Italy) |
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| Authors: | M Porreca M Mattei C MacNiocaill G Giordano E McClelland R Funiciello |
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| Institution: | (1) Dipartimento Scienze Geologiche, Università Roma Tre, Roma, Italy;(2) Department of Earth Sciences, University of Oxford, Oxford, UK |
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| Abstract: | The Peperino Albano (approximately 19–36 ka old) is a phreatomagmatic pyroclastic flow deposit, cropping out along the slopes
of the associated Albano maar (Colli Albani volcano, Italy). The deposit exhibits lateral and vertical transitions from valley
pond to veneer facies, as well as intracrater facies. We present the results of a paleomagnetic study of thermal remanent
magnetization (TRM) of the lithic clasts of the Peperino Albano ignimbrite that provide quantitative estimates of the range
of emplacement temperatures across the different facies of the ignimbrite. Emplacement temperatures estimated for the Peperino
Albano ignimbrite range between 240° and 350°C, with the temperatures defined in the intracrater facies being generally lower
than in the valley pond and veneer facies. This is possibly due to the large size of the sampled clasts in the intracrater
facies which, when coupled with low temperature at the vent, were not completely heated throughout their volume during emplacement.
The emplacement temperatures derived from the paleomagnetic results are in good agreement with the presence of un-burnt plants
at the base of the ignimbrite, indicating that the temperature of the pyroclastic flow was lower than the temperature of ignition
of wood. Paleomagnetic results from the Peperino Albano confirm the reliability of the paleomagnetic approach in defining
the thermal history of pyroclastic flow deposits. |
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| Keywords: | Emplacement temperature Paleomagnetism Pyroclastic flow Colli Albani |
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