Next, the internal stratigraphy of alluvial fan A20 is described in
which, besides debris flows, pyroclastic fallout deposits are found and
a detailed chronology of paleosols is available. Alluvial fan A20 exhibits
a transversal section of 514mwidth and a minimum thickness of 5.3 m.
At sectionM-26, the fan consists of four nearly horizontal beds separated
by four incipient paleosols or erosive surfaces. Their superimposition
forms the alluvial fan (Fig. 6).