Geology and tectonic history of Southeastern Luzon, Philippines

Abstract Southeastern Luzon belongs to the eastern Philippine Mobile Belt. Geological and structural studies revealed that it could be divided into three major structural units limited by two subparallel NW-SE trending left-lateral strike-slip faults: the Hilawan Fault in the NE and the Minas Fault in the SW. The North-central Catanduanes Structural Unit (NCSU) is characterized by a Middle to early Late Cretaceous volcanic arc sequence unconformably overlain by a Middle to Late Eocene volcanic arc sequence followed by Early Oligocene intrusives. The Median Structural Unit (MSU), limited from the NCSU by the Hilawan Fault, is underlain by a Late Cretaceous volcanic arc sequence followed by two distinct chaotic sequences from the end of Cretaceous-Paleocene and latest Middle Eocene-earliest Late Eocene. It is limited to the southwest by the Minas Fault. The Western Caramoan Structural Unit (WCSU), pre-Late Cretaceous ophiolitic suite unconformably overlain by Late Cretaceous volcanic arc sequence and Middle Eocene limestones are exposed. These structural units are overlain by carbonate and detrital sequence from the Late Oligocene to Pliocene. Constrained by angular unconformities and deposition of olistostromes, polyphase left-lateral strike-slip faulting was recorded since the end of Cretaceous up to the limit of Early-Late Oligocene. These faults probably represent the traces of a Proto-Philippine Fault System in Southeastern Luzon.