Bioclasts consist of open planktonic foraminifers and nannofossil ooze in the highly vitric layers, while filled planktonic foraminifers, benthic foraminifers, and a variety of shallow water calcareous and siliceous fossils and littoral skeletal debris are common in the basal coarser grained parts of turbidites. Most volcaniclastic units thought to represent ignimbrite eruptions consist of a coarse basal part in which pumice and large brown nonvesicular and welded tuff shards and crystals dominate, and an upper part that commonly consists of thin turbidites highly enriched in bubble-wall shards. The prominent coarser grained and vitroclast-rich volcaniclastic layers were probably emplaced dominantly by turbidity currents immediately following entry of ash flows into the sea. Generally fresh sideromelane shards that occur dispersed in many felsic volcaniclastic layers and in one hyaloclastite layer are mostly nonvesicular and blocky. They indicate submarine basaltic eruptions at water depths of several hundred meters on the slope of Gran Canaria synchronously with felsic ash flow eruptions on land.
Most shards have alkali basaltic compositions.
The dense, iron-rich, moderately evolved basaltic magmas are thought to be the direct parent magmas for the trachytic to rhyolitic magmas of the Mog n Group. They were probably unable to erupt beneath the thick, low-density lid of the felsic magma reservoir below the large caldera but were erupted through lateral dikes onto the flanks of the submarine cone. Tholeiitic shards occur low in the stratigraphic section where peraluminous K-poor magmas were erupted, a correlation that supports the parental relationship. Heterogeneity in glass and crystal populations in the absence of other evidence for an epiclastic origin, probably largely reflect systematic primary compositional heterogeneity of most of the ignimbrites, which become more mafic toward the top. Post-emplacement, erosional mixing is probably reflected in volcaniclastic layers that are well bedded, contain a large amount of shallow water skeletal debris and rounded basaltic lithoclast, and show a wide spectrum of glass and mineral compositions.