Field photos and photomicrographs of the Pedro Miguel Formation.

A) Field photograph of inward dipping basaltic lava flows and welded pyroclastic deposits. B) Photomicrograph of a Pedro Miguel lava flow. Note the equal sized sub-to-euhedral clinopyroxene and plagioclase phenocrysts surrounded by plagioclase microlites. C) Photomicrograph of welded pyroclastic deposit. Note stretched glass bands. D) Photomicrograph of fragmented pyroclastic deposit. Note angular welded pyroclastic fragments surrounded by darker fine-grained matrix.