Upper Permian to Middle Jurassic radiolarian assemblages of Busuanga and surrounding islands, Palawan, Philippines

Abstract

The North Palawan Block is regarded as the southernmost continuation of a Late Mesozoic accretionary complex, which developed along the length of the East Asian margin. It records a long (up to ~ 100 My) period of pelagic deposition on an oceanic plate from Late Permian to Late Jurassic when subduction resulting in the disappearance of the plate by the Early Cretaceous began. Subduction-accretion resulted in the development of three lithotectonic belts. From thirteen localities within these belts, radiolarian investigations yielded 173 species belonging to 92 genera and 45 families. Most of the samples contain Middle to Upper Triassic faunas. Several sections containing upper Permian, Lower Jurassic, and Middle Jurassic assemblages were also found. The presence of benthonic and planktonic foraminifers at some localities indicates that portions of the Liminangcong Formation were deposited in environments above the carbonate compensation depth (CCD). Manganese deposits found in some areas (e.g. Busuanga and Dabatonay) suggest that parts of the depositional area experienced a very low average sedimentation rate. Examination of the North Palawan accretionary complex reveals the ghosted history of the Izanagi Plate and constrains the timing of subduction beneath the eastern margin of Asia.