9419111 Self This study is to map, sample, and analyze by both granulometry and clast morphology the various facies of the 1991 ignimbrite at Mount Pinatubo, Philippines. Fabric studies of the main body of the ignimbrite by anisotropy of magnetic susceptibility (AMS) will also be undertaken. The main aim is to better understand the lithofacies and facies association of the deposit, its emplacement mechanisms, and the nature of the pyroclastic flows. The information, which will be put into the well-constrained temporal framework of the 3.5-hour-long climax, will shed much-needed light on the current debate in volcanology concerning the nature of, and the spectrum of deposition mechanisms from, pyroclastic flows. The study will also provide information on the amount od co-ignimbrite ash generated during the 1991 eruption. Without detailed studies of ignimbrites, models of pyroclastic flow emplacement will continue to outstrip the amount of information available from actual examples that have been explored in detail, and in this regard the value of results from the new, large Pinatubo deposit should not be lost.
