NEW ERUPTIVE VENTS FOR THE WHAKAMARU-IGNIMBRITE (TAUPO VOLCANIC ZONE)IDENTIFIED FROM MAGNETIC FABRIC STUDY

The location of possible source vents for the Whakamaru Ignimbrite was investigated using flow directions inferred from anisotropy of magnet ic susceptibility (AMS). If we assume that the magnetic fabric was for med in response to processes in the formative pyroclastic flow, the ma gnetic lineation is related to die direction to die source vent. Linea tion vectors mostly appear to dip towards the source, suggesting a flo w-related imbrication of the fabric. AMS has been determined at 22 sit es around Lake Taupo, and show an average bulk magnetic susceptibility (MS) of 8.04 x 10(-3) SI. The degree of anisotropy (P) ranges from 1. 014 to 1.032. The magnetic susceptibility is due to titanomagnetite. M easurements showing strongly dipping magnetic foliations presumably ca used by underlying topography and local deflections of the flow have b een discarded. The magnetic lineation is dipping towards the source in 14 sites and 180-degrees from the source in four sites. Four source v ents for the Whakamaru Ignimbrite are interpreted along an 80 km north -south trend on the eastern shore of Lake Taupo. Our interpretation co rroborates the results of previous studies which have identified vents near Wairakei and northern Lake Taupo. This study shows that there ar e other possible source vents south of the lake and north of Wairakei.