Chemical characteristics of ash layers from ODP Leg 104@en

Forty-five volcanic ash horizons cored at Sites 642, 643, and 644 on the Vøring Plateau and ranging in age from early Miocene to Pleistocene, are discussed in terms of their magmatic features as well as their diagenetic evolution. Most of these layers, some centimeters thick, are mainly made of fresh rhyolitic glass. Twenty-five percent of the ash layers, however, contain variable amounts of more basic glass shards, ranging in composition from Mg-rich tholeiites to icelandites through Mg-poor basalts, ferrobasalts, and tholeiitic andesites, and are commonly associated with rhyolitic shards. […]