Sandstone, conglomerate, shale

Stratigraphic relations

Conformable over the Cabagan Formation


Ilagan, Isabela; Sicalao-Casiggayan High


Late Pliocene – Early Pleistocene


2,200 m

Named by

Ilagan Sandstone (Corby and others, 1951)

Renamed by

MGB (2004)

The name Ilagan Sandstone was used by Corby and others (1951) for the exposure along Ilagan River, south of Ilagan, Isabela. Subsequent workers called it Ilagan Formation. It is widespread over the valley south of the Sicalao-Casiggayan High. It conformably overlies the Cabagan Formation. The Ilagan Formation is divided into a lower marine shale and sandstone alternation and an upper coarser marine sandstone and continental sandstone and conglomerate sequence. The bottom is characterized by abundant mollusks. The formation is 2200 m thick in the type area. BED (1986a) assigns an age of Late Pliocene to Early Pleistocene for the Ilagan. Marine fauna indicate warm, shallow to brackish water deposition.

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