Determination and appraisal of pyroclastic flow directions using magnetic anisotropy on ignimbrites from Mount Aragats, Armenia
Final Report Abstract
We investigated paleomagnetically 32 sites of ignimbrite deposits surrounding the Aragatz volcano on the territory of Armenia. Demagnetization experiments together with rock magnetic measurements indicate magnetite and some minor amount of hematite as the magnetic carrier of the remanent magnetization in these rocks. Directional analysis based on thermal and alternating field demagnetization yield predominantly normal polarity directions of 17 sites and reversed polarity of the remaining 5 sites. The clustering is quite high within all normal polarity directions, suggesting that secular variation has been recorded. In this case all these sites belong to a single eruptive event during a rather short time interval (less than 1000 years). Therefore, we argue that our paleomagnetic directions suggest that only two major events of massive pyroclastic activity took place from the Aragatz volcano. Measurements of the anisotropy of susceptibility as well as anhysteretic remanent magnetization clearly indicates that AMS is the better proxy to investigate paleo flow directions. Performing AMS measurements on all 32 outcrops suggests that the eruption happened at first in a radial manner. At a higher distance the flow apparently is more influenced by local topography
