Identifying ash flow sources with directional data: An application to the Kizilkaya ignimbrite, central Anatolia

Magnetic fabric of ignimbrites: a case study from the Central Anatolian Volcanic Province

“…The shaded area represents the maximum overlapping zone after triangulation, regarded as the Kızılkaya ignimbrite source area. directions point to a source area between the Derinkuyu Basin and the Göllü Dag rhyolite massif, and substantiate the location proposed by Le Le Pennec (2000). The limited number of sites and their uneven geographical distribution prevent a closer definition of the source area.…”

“…The results are shown in Figure 9, where the arrows correspond to the foliation plunge and the white fans to the 95% confidence limit of the lineation. According to the model (Hillhouse & Wells 1991;Le Pennec 2000;Palmer & MacDonald 2002), the convergence area of all these directions should locate the source area from which the pyroclastic current flowed. Inspection of Figure 9 shows that the source area is not well defined: at some sites (Ovacık, Soganlı and Guzelöz), the directions point to a source area in the SW, in the Ç iflik region, whereas those from the other sites are scattered.…”

“…The red-coloured Kızılkaya ignimbrite is the largest unit of the succession, with a volume in excess of 180 km 3 (the value was obtained considering the ignimbrite cropping out-area extension and average thickness, and is not the dense-rock equivalent volume) and an extent of about 10 600 km 2 (Le Pennec et al 1994;Schumacher & Mues-Schumacher 1996). It commonly defines flat tabular surfaces on the Nevşehir plateau, displaying a low aspect ratio (about 1/7000), and generally consists of uniform and massive deposits some 15 -20 m thick, although it can locally exceed 80 m in the palaeovalleys, such as at Ihlara (Schumacher & Mues-Schumacher 1996;Le Pennec 2000). The ignimbrite, entirely representing an outflow deposit, is typically columnar-jointed, whose patterns indicate that it is a single flow and cooling unit, with a lower vitric and an upper devitrified zone.…”

“…The degree of welding varies from incipient to high; it is unwelded at the base and in distal facies, and densely welded in the middle -upper portions in proximal-medial facies ). Its composition is rhyolitic (71-73% SiO 2 ), pumice is porphyritic and contains 30 -35% plagioclase, biotite, quartz, minor amphibole and oxides (Le Pennec 2000).…”

“…The Kızılkaya ignimbrite, the youngest and most widespread ignimbrite of the Neogene sequence of the Cappadocian Province, was extensively studied by Le Pennec et al (1994 and Le Pennec (2000) using the AMS technique to infer the vent position, since the surficial expressions of the caldera structures are missing. AMS data, as well as isopach and isopleth maps of the underlying fall layer and petrofabric measurements, suggested a source area in the neighbourhood of the Göllü Dag Quaternary rhyolitic complex, to the SW of the town of Derinkuyu, on the Nevsehir plateau (Fig.…”