- Middle member – calcarenite
Conformable over the Cabaluan Formation
Sta. Cruz, Zambales; Bolinao, Pangasinan southward to Iba, Zambales
Sta. Cruz Marl (Von Drasche, 1878)
Von Drasche (1878) first named the sedimentary rocks exposed at Sta. Cruz, Zambales as Sta Cruz Marl, which was later renamed Sta. Cruz Formation by Stoll (1962). The formation can be traced along a wide belt from Bolinao, Pangasinan that thins out to the south at Iba, Zambales.
Along the Cabaluan River section, the contact with the underlying limestone member of the Zambales Formation is transitional. The predominantly clastic unit above the limestone of the Zambales Formation is considered by Karig and others (1986) as representing the Sta. Cruz Formation, which they divide into three members: lower mudstone and marl, middle calcarenite and upper turbiditic clastic sequence. Planktic and benthic foraminifera from the three members suggest a progressive deepening in the environment of deposition up to mid-bathyal depths for the middle calacarenite and upper sequence of sandstone - pebble conglomerate - tuffaceous mudstone. Karig and others (1986) report that planktic foraminifera from all three members indicate a late Late Miocene age (zone N17/N18). A thickness of at least 750 m is estimated for the whole formation, broken down as follows: 175-200 m for the lower mudstone and marl member; 50 m for the middle calcarenite and at least 500 m for the upper clastic sequence.