Limestone, conglomerate, sandstone, shale

Stratigraphic relations

Unconformable over the Lubuagan Formation


Callao at Peñablanca, Gattaran, Paret Embayment, Cagayan


Middle Miocene


540 – 1,000 m

Named by

Corby and others (1951) as Callao Limestone

Renamed by

MGB (2004)


Aglipay Formation (MMAJ-JICA, 1975)

The formation was previously named Callao Limestone by and others (1951) for the limestone section exposed at Barrio Callao, Peñablanca, Cagayan. It is basically a reef complex which grades into a clastic facies in the deeper part of Cagayan Valley. A sequence of conglomerate, sandstone and shale in Dutan River on the eastern part of the valley, was found to be unconformable over the tilted beds of the Lubuagan Formation. The limestone body describes a crescent shape extending to the northern foothills of Sicalao Ridge, east-northeast of Gattaran, Cagayan. The lower limestone unit is well-developed in the southern part of the valley and along the eastern flank while the clastic facies outcrops over the rest of the valley. The limestone facies is flesh to gray and coralline with few large foraminifera. The clastic facies is composed of light gray, fine to medium grained sandy limestone with interbeds of shale and conglomerate at the base. A sample of shale from Dutan River yielded nannofossils of NN7 zone (late Middle Miocene). Likewise, recent dating of the limestone indicates a Middle Miocene age. The reef limestone was deposited in a near-shore environment, the clastic facies in deeper water. It is about 540 m thick at the type locality (Durkee and Pederson, 1961) but is 1000 m thick in the Paret Embayment.

The Callao Formation is equivalent to the Aglipay Formation of MMAJ-JICA (1975) which outcrops at the southern end of the Cagayan Valley Basin. The limestone member of this formation is exposed near the town of Aglipay, in the lower reaches of Addalam River. This formation was likewise dated Middle Miocene based on the dating of benthic foraminifera found in the limestone.

The Callao is considered by BED (1986a) and Caagusan (1978) as a Late Miocene formation coeval with the Cabagan Formation. The equivalent of the Middle Miocene formations for BED (1986a) and Caagusan (1978) are the Sicalao Limestone and Lubuagan Formation.

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