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Geology of Villarrica - Photo Album Page 2

Proximal, multiple flow facies of the Pucón Ignimbrite, located on the north flank of Volcán Villarrica. Four nonwelded pyroclastic flow units (labeled I-IV) are well defined by changes in color, lithic clast assemblage and bedding features. They are overlain by well-bedded, palagonitized fallout deposits, and they are underlain by glacial till. The lowermost unit has a distinctive brownish color owing to an abundance of accessory lithic material. Coarse lenticular beds at flow unit contacts are coarse aggregates of essential scoria pyroclasts.
Close-up of the base of Flow Unit I from the previous photo. A distinctive fine-grained zone (ground layer?) occurs at the base of the flow unit. In contrast, the upper three flow units have basal zones which are enriched in coarse scoria.
Close-up of the top of Flow Unit IV. There are several noteworthy features shown here. Note that the unit grades upward into fine-grained (coignimbrite?) tephra, and that it is overlain by a prominent orangish-colored fallout layer with abundant accretionary lapilli. The orangish color is a result of palagonitization.
Coarse, massive road-cut exposure of the Pucón Ignimbrite ~10 km east of V-II caldera. Note the large pyroclasts of angular granitic lithics and scoria in the massive, black, unwelded matrix. Differences in outcrop color from top to bottom are an artifact of wetting (i.e. by rain).
One essential scoria pyroclast collected from the outcrop shown above. The scoria has been brocken open to reveal a spectacular example of a partially melted granodioritic xenolith. The scoria is about 30 cm across.

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