Evaluating the Neogene paleoclimatic record of northwestern Luzon from paleoweathering proxies

Abstract This study examines the applicability of geochemical proxies used in paleoclimatic studies in the South China Sea Basin (SCSB) to decipher paleoweathering and paleoclimatic signatures recorded in the Neogene clastic sediments overlying the Zambales Ophiolite Complex (ZOC) in northern Luzon, Philippines. The Early Miocene Cabaluan Formation and the Late Miocene to Early Pliocene Santa Cruz Formation—the clastic units overlying the western flank of the ZOC—offer insights into the full suite of Neogene paleoclimatic variations in the area. Weathering indices, such as the Chemical Index of Alteration (CIA), Revised Chemical Index of Alteration (CIX), and Chemical Index of Weathering (CIW), alongside dual-elemental ratios (Al/Ti, Sc/Ti, Na/Al), indicate intense weathering conditions during a warm climate in the Early Miocene, transitioning to less intense weathering due to cooler climatic conditions in the Late Miocene to Early Pliocene. These findings align with regional trends observed in the northern South China Sea and global climatic patterns. The clastic units overlying the ZOC record the influence of the East Asian Summer Monsoon (EASM) on the climatic evolution of the study area and the surrounding region since the Early Miocene.