Content

BONDOC PENINSULA

The stratigraphic grouping for Bondoc Peninsula (SG 8) includes Burias Island. Ticao Island and Southern Masbate of the Masbate Island Group.

Gumaca Schist
Lithology	Quartzofeldspathic schist, greenschist, amphibolite
Stratigraphic relations	Constitutes the basement rocks
Distribution	Gumaca, Unisan
Age	Cretaceous
Named by	MGB (this volume)

The Gumaca Schist consists chiefly of quartzofelspathic schist,greenschist and amphibolites. The schist occurs as small irregular bodies in Gumaca and Unisan. The typical Mineral assemblage of the quatzofeldspathic schists is chlorite, sericite, quartz and albite. West of Unisan albite-epidote-amphibole schist is in contact with metagabbro. The amphibolite schists commonly border ultramafic rocks and might represent the metamorphic sole of an ophiolitic body, passibly the Cadig Ophiolitic Complex of Southeastern Luzon. Aurelio (1992) has reported the existence of pillow basalts about 4 km east of Unisan, which are capped by thin pelagic limestone deposits containing Globotruncana. This indicates that the associated ophiolitic formation is not younger thatn Late Cretaceous.

Unisan Formation
Lithology	Andesite, basalt, tuffaceous sandstone, conglomerate
Stratigraphic relations	Overlies the Gumaca schist
Distribution	Unisan - Pitogo road; Panaon and Guinayangan
Age	Late Eocene - Early Oligocene
Previous Name	Unisan Volcanics (Banogon , 1974)
Renamed by	MGB (this volume)

The Unisan Formation was previously named by Banogon (1974) as Unisan Volcanics for the exposures along the Unisan - Pitogo road. It is also exposed near PAnaon as well as the provincial road to Guinayangan, in the vicinity of the Manato railroad station. The formatio consists of porphyritic andesite and amyrdaloidal basalt with occasional interbeds of tuffaceous sandstones and conglomerate. Banogon (1974) suggest an Oligocene age for the Unisan. However, nannofossil determinations by Muller (in Aurelio, 1992) indicate the presence of Reticulofenestra umbilica, Cyclicargolithus floridanus, Sphenolithus predistentus, S. moniformis, Helicosphaera age range from Late Eocene to Early Oligocene.

Panaon Limestone
Lithology	Limestone
Stratigraphic relations	Unconformable over the Unisan Formation
Distribution	Panaon (northwestern part of the peninsula)
Age	Late Oligocene - Early Miocene
Named by	Unisan Volcanics (Banogon , 1974)
Renamed by	Antonio (1961)

The Panaon Limestone was named by Antonio (1961) for the exposures at Panaon, Quezon. The Limestone also outcrops along Plaridel Road, Unisan - Panaon Road, Tumagay and Malicboy. The formation consists of medium- to thickly bedded bioclastic limestone, which unconformably overlies the Unisan Formation. Fossil assemblage in the limestone includes Lepidocyclina (Nephrolepidal) parva, Cycloclypeus sp. and few Miogypsina sp., indicating Late Oligocene - Early Miocene age (Lubas and others, 1998).

Vigo Formation
Lithology	Sandstones, shale, mudstones, limestone,conglomerate
Stratigraphic relations	Unconformable over the Panaon Limestone
Distribution	Vigo River Valley; Widespread along the length of the peninsula
Age	Early - Middle Miocene
Thickness	2,530 m
Previous name	Vigo Shale (Pratt and Smiith, 1913)
Renamed by	Corby and others (1951)

The Vigo Formation was initially named by Pratt and Smith (1913) as Vigo Shale. The type locality is at the Vigo River Valley in the southeast. It is widely exposed in the peninsula in a belt extending from the southern end of the peninsula to the northern end at Gumaca. The formation consists mainly of sandstones and shales with interbeds of congloerate and lenses of limestone. Lubas and others (1998) subdivide the Vigo into two members - Lower Vigo and Upper Vigo. Comprising the Lower Vigo are shales and sandstones with lenses of limestone. The sandstones grade laterally from feldspathic wackes into calcareous wackes. Constituting the Upper Vigo is medium to thickly bedded lcast-supported polymictic poorly sorted conglomerates interbedded with siltstones and sandstones. Foraminiferal and nannoplankton assemblage indicates an age of Early Miocene for the lower Vigo and MIddle Miocene for the Upper Vigo (Aureliom 1992; Lubas and others, 1998). The total thickness of the Vigo Formation is 2,530 m (BMG, 1981).

Canguinsa Formation
Lithology	Sandstones, shale, conglomerate
Stratigraphic relations	Unconformable over the Vigo Formation
Distribution	Canguinsa River, Malunay, San Narciso; Gumaca, Pitogo
Age	Late Miocene - Pliocene
Thickness	2,280 m
Previous name	Canguinsan Sandstone (Pratt and Smith, 1913)
Renamed by	Corby and others (1951)

The Canguinsa Formation was previously named by Pratt and Smith (1913) as Canguinsa Sandstone for the exposures in and around Canguinsa River. The formation is also well exposed along the Malunay - San Narciso road and Gumaca - Pitogo road. It unconformably overlies the Vigo Formation. The Canguinsa predominantly consist of sandstones (about 75 per cent) rhythmically interbedded with shale, pebble and conglomerate and limestone. The pebbles in the conglomerate are mostly basalt and andesite and few calcareous sandstones and and limestone cemented by coarse calcareous sandy matrix. The formation is subdivided into Lower Canguinsa and Upper Canguinsa. The Lower Canguinsa is predominantly medium to coarse-grained sandstones. Local Conglomerate beds have been observed at the base of the unit. Carboneceous layers of siltstone and siltstone. Based on the foraminifera and nannoplankton assemblage, the Lower and Upper Canguinsa were dated Late Miocene and Pliocene, respectively (BMG, 1981; Aurelio, 1992; Lubas and others, 1998). The Canguinsa has a thickness of 2,280 m along the Malunay-San Narciso road section.

The Pitogo Conglomerate of Punay (1960) is probably equivalent to the basal portion of the Lower Canguinsan. The Pitogo was described as a sequence of conglomerate, sandstones and shale with occasional thi beds of detrital limestone. It conformably overlies theVigo Formation in the northwestern portion of the peninsula. The Aloneros Conglomerate of Corby and others (1951) between Sto. Domingo and Aloneros is apparently equivalent to the Pitogo.

Hondagua Formation
Lithology	Siltstone, Conglomerate, sandstones, shale limestone
Stratigraphic relations	Conformable over the Canguinsa Formation
Distribution	Hondagua, between Calauag and Lopez
Age	Pliocene
Thickness	1,750 m
Previous name	Hondagua Silt (Corby and others, 1951)
Renamed by	Espiritu and others (1968)

The Hondagua Formation was previously named by Corby and others (1951) as Hondagua Silt for the exposures in the vicinity of the railway station at Hondagua, between Lopez and Calauag towns. The formation is alo well exposed along the Lopez-Sumulong-Guinayangan road. It conformably overlies the Canguinsan Formation. The Hondagua consists of siltstone, shale and calcareous sandstone with interbeds of conglomerate and argillaceous limestone. The siltstone is medium to thick bedded and highly indurated. The conglomerate is massive with pebbles of basalt, andesite, sandstone and limestone set in a coarse calcareous sandy matrix. Foraminifera in samples of the formation indicate a Pliocene age. It is 1,100 m thick along the Sumulong-Lopez road (Espiritu and others, 1968), while a thickness of 1,750 m is reported by BMG (1981).

Vinas Formation
Lithology	Sandstone, mudstone, conglomerate, limestone
Stratigraphic relations	Conformably underlain by the Hondagua Formation and overlain by the Malumbang Formation
Distribution	Vinas, Sumulong; Dona Aurora, Calauag
Age	Pliocene
Thickness	475 m
Named by	Corby and others (1951)

This formation was named by Corby and others (1951) for the rocks typically exposed between Sumulong and Vinas, northeast of Caluag, Quezon. It also crops out as far as Dona Aurora, Calauag. The Vinas rests conformably on the Hondagua Formation and is disconformably overlain by the Malumbag Formation. As described by Espiritu and others (1968), it consist of basal beds of limestone and conglomerate succeeded by a series of poorly bedded, sandy and fossiliferous limestone, calcareous sandstone and mudstones with interbeds of pebble and cobble congolomerates. The sandstone is medium to thick bedded, coarse-grained to pebbly and poorly to fairly consolidate and in places, conglomeratic. Comprising the mudstones are thin to medium bedded siltstones, claystones and shale. The conglomerates contain sub-angular to rounded pebbles and cobbles in a coarse calcareous matrix. At the type locality, the shale contains large fosssil and helical and conical shells. On the basis of its fossil content and stratigraphic position, the age of the Vinas Formation is placed at Pliocene. It has a thickness of 475 m as measured along the Sumulong - Dona Aurora road section (Espiritu and others, 1968).

Malumbang Formation
Lithology	Limestone, sandstone, siltstone, shale, marl
Stratigraphic relations	Disconformably overlies the Vinas Formation
Distribution	Malumbag Plains; Sumulong - Guinyangan road
Age	Pleistocene
Thickness	1,610 m
Previous Name	Malumbang Series (Pratt and Smith, 1913)
Renamed by	Espiritu and others (1968)

The Malumbag Formation was originally named by Pratt and Smith (1913) as Malumbang Series in reference to the limestone exposures in the Malumbang Plains in the southeastern part of the peninsula. It is also well exposed along the Sumulong - Guinayangan road where its thickness reaches 1,610 m. The formation disconformably overlies the Vinas Formation. The Malumbang consists predominantly of Limestone with interbeds of sandstone, siltstone and shale. Light gray to brownish marl is also present in the lower part of the formation. The limestone is cream, buff of dirty white, medium to thick bedded and medium to coarse-grained. The siltstone is massive to medium bedded. The faunal assemblages correspond to nannozone NN19 (Aurelio, 1992) indicating a Pleistocene age.

SOUTHWEST LUZON UPLANDS

San Juan Formation
Lithology	Basalt, andesite, graywacke, shale,slate,paraschist, marble, hornfels
Stratigraphic relations	Intruded by the Tolos Diorite
Distribution	San Juan and Lobo, Batangas
Age	Oligocene
Previous name	San Juan Metavolcanics and Metasediments (Avila, 1980)
Renamed by	MGB (this volume)
Correlation	San Agapito Dacite (Verde Island)

The San Juan Formation was previously named SAn Juan Metavolcanics and Metasediments by Avila (1980) for the exposures at the headwaters of Calumpit River north-northeast of Lobo and along the junction of Lobo River with Malobo River in Batangas. The same units are also exposed at the upper reaches of Kipot River southwest of San Juan and could be traced northwestward to the headwaters of Igot River at Libato Creek. The metavolcanic rocks are are dark gray to greenish-gray, fine0 to medium-grained highly indurated graywacke and grayish to reddish brown fine-grained ferruginous shale. The formation also includes hornfels, slates paraschist and marbles in contact metamorphic aureoles around quartz diorite intrusions. Wolfe and others (1980) mention a limestone sample, which could be a lense in the metasediments. It was dated by M.V. Reyes of the Philippine Oil Development Company as Oligocene. The San Agapito Dacite of Verde Islands could be equivalent to this formation.

Tolos Quartz Diorite
Lithology	Quartz diorite, quartz monzonite, diorite dacite
Stratigraphic relations	Intrudes the San Juan Formation
Distribution	San Juan, Taysan and Lobo, Batangas
Age	Early Miocene
Previous name	Tolos Batholith (Wolfe and others, 1980); San Juan Quartz Diorite (Avila, 1980)
Renamed by	MGB (this volume)

The intrusive rock that mainly occupies the southern part of the Batangas within San Juan, Taysan and Lobo was previously named San Juan Quartz Diorite by Avila (1980) and Tolos Batholith by Wolfe and others (1980). The Tolos is a batholith body that reaches 12 km in width and 20 km in length.

The core zone consist mainly of biotite quartz diorite, which grades into hornblende quartz diorite , which grades into hornblende quartz diorite and hornblende diorite towards the west and southwest (Wolfe, 1980). Smaller bodies of apophysal and hypabyssal dimensions also intrude the San Juan Formation. Associated quartz monzonite and dacite are also present. The batholith is foliated and gneissose near its contact with the metamorphosed intruded rock. On the other hand, the rocks intruded by this batholith are thermally metamorphosed into hornfels, marble and skarn with notable grossularite. In Mataas-na-Lupa and Sto. Nino, Taysan, north-northwest trending diorite bodies show prominent copper mineralization. Wolfe and others (1980) assign an Early Miocene age to this intrusive body. A post-mineral dacite dike intruding the batholith gives a whole rock 40 K-40Ar age of 14.8+= 0.9 Ma, equivalent to early Middle Miocne (Langhian)).

Looc Volcanic Complex
Lithology	Agglomerate, tuff, andesite, dacite
Stratigraphic relations	Unconformable over the San Juan Formation; overlain by the Calatagan Formation
Distribution	Looc, Taysan and Lobo, Batangas
Age	Middle Miocene
Thickness	500 m
Named by	Malicdem and others (1963)
Renamed by	MGB (this volume)
Synonymy	Batangas Volcanics (Corby and others, 1951),Talahib Andesite (Avila, 1980), BanoyVolcanics (Wolfe and others, 1980)

The Nasugbu Volcanic Complex was previously named Batangas Extrusives and Pyroclastics by Malicdem and others (1963) for the exposures of Volcanic rocks around the Looc lead-silver-antimony mine at Looc, Nasugbu, Batangas. Malicdem and others (1963) consider the unit equivalent to the Batangas Volcanic of Corby and others (1951) but it was renamed in recognition of its pyroclastic components. It is here renamed Nasugbu Volcanic Complex to indicate a more specific type locality. As described by Malicden and others (1963), the section at the mine site may be divided into three members: andesitic pyroclastic member, andesitic pyroclastics and flows and dacitic pyroclastics and flows. Altogether, the thickness of the three members totals about 500 m. It is assigned a Middle Miocene age. Near the mineral deposit, the rocks suffered various degrees of alteration, including chloritization, argillization and silicification. A small exposure of thinly bedded steeply dipping tuffaceous shale northeast of the Looc mine site is probably part of the limestone.

The andesitic pyroclastic member consists of agglomerate, tuff and lapilli tuff. The andesitic fragments of the agglomerates range in size from a centimeter to as much as 50 cm. The thickness of this member is estimated at 220 m.

Andesitic flows, tuffs and tuff breccia comprise the andesitic pyroclastics and flows. The andesite flows constitute more than 50 per cent of the section. Horneblende needles define flow directions. The andesite is the main host of the mineral deposit. This member has a thickness of 110 m.

The dacitic pyroclastics and flows consist mostly of agglomerate and lapilli tuff with very minor amounts of ash tuff and dacitic flows. Fragments of the agglomerate and lapilli tuff are composed of dacite. The thickness of this member is estimated at 170 m.

The Talahib Andesite of Avila (1980) is considered equivalent to the Nasugbu Volcanic Complex. The Talahib is exposed in the west-central and southeastern part of Batangas. It is overlain by the Mapulo Limestone ((Avila, 1980), which is considered equivalent to the Calatagan Formation, at the upper reaches of the western tributary of Talahib River and also along Laiya River. The andesite is characteristically vesicular and amygdaloidal and exhibits flow banding. It alo includes fine-grained, porphyritic and medium-grained equigranular phases. Thin pyroclastic layers are intercalated with the flows. Propylitization of the andesite is common, with remarkable development of chlorite and epidote. Moderate unit is apparently equivalent to the Banoy Volcanics of Wolfe and others (1980) to which they assign a Middle to Late Miocene age.

Dagatan Wacke
Lithology	Feldspathic and volcanic wacke; conglomerate
Stratigraphic relations	Rests on the San Juan Formation; overlain by the Calatagan Formation
Distribution	Taysan, Batangas
Age	Middle Miocene
Thickness	20 m
Named by	Wolfe and others (1980)

The Dagatan Wacke was named by Wolfe and others (1980) for the rocks exposed in the road cuts at Sto. Nino, Taysan and the road from Dagatan to Lobo. The unit consist of feldspathic to volcanic wcke with fine to conglomeratic facies. Clasts of quartz diorite, metavolcanic rocks, andesite and dacites in the wacke have been noted (Wolfe and others, 1980). It has a maximum thickness of 20 m at the Taysan Porphyry Copper Mine. The base of this unit rests unconformably over the metavolcanic rocks of San Juan Foramation. The presence of a fossil mollusk, Vicarya callosa Martin , in samples from Lobo and Nanlobo rivers indicates an age no older than Middle Miocene (Wolfe and others, 1980). Other mollusks and plant remains were found, which indicate near-shore deposition of the Dagatan. The wacke coould be coeval to the Nasugbu Volcanic Complex. The top of the Dagatan Wacke is overlain by a Late Miocene limestone unit, the Dingle Limestone of Wolfe and others (1980), which is probably equivalent to the Calatagan Formation.

Corregidor Formation
Lithology	Conglomerate, tuffs
Stratigraphic relations	Rest on the Nasugbu, Volcanic Complex
Distribution	Corregidor Peninsula; tip of Bataan Peninsula; Limbones Island; Patungan, Cavite; Looc; Batangas
Age	Late Miocene
Previous Name	Corregidor Conglomerate (Corby and others, 1951)
Renamed by	MGB (this volume)
Synonymy	Cutad pyroclastics and sedimentary rocks (Malicdem and others, 1963)

The Corregidor Formation was previously named Corregidor Conglomerate by Corby and others (1951), which was described earlier by Adams (1910). Exposures ofthis unit, mainly in Corregidor Island and Limbones Island, describe a belt from the southeastern tip of Bataan Peninsula to Looc, Batangas. It consists pricipally of cobble to boulder conglomerate with interbeds of sandstones and shale that were apparently deposited in a littoral environment. The sandstone exhibits cross-bedding and the shale is silty and tuffaceous. As described by Adams (1910), the conglomerate near Ternate and Naic (in Cavite) apparently grade into tuffs.

Malicdem and others (1963) consider their Cutad pyroclastic and sedimentary rocks to be equivalent to the Corregidor Conglomerate. As mapped by Malicdem and others (1963), the Cutad covers the western coast of the area from Patungan, Cavite (including Limbones Island) to a point south of Looc Cove in Batangas. The pyroclastics of the Cutad consists of agglomerates with minor amounts of ash tuff and lapilli tuff. A 30 m thick oxyhornblendeandesite flow is intercalated with the tuff of Pasong Creek. The upper portion of the Cuta is omposed mostly of tuffaceous boulder conglomerate with thin lenses of tuffaceous sandstone exhibiting graded bedding and cross bedding. Towards the south, the boulders become smaller with increasing percntage os finer materials (Malicdem and others, 1963). Corby and others (1951) assign in a probable Late Miocene age to the Corregidor Conglomerate. It is probably partly coeval with the Calatagan Formation

Calatagan Formation
Lithology	Limestone, marl, siltstone
Stratigraphic relations	Rests on the Nasugbu Volcanic, Complex
Distribution	Calatagan Peninsula; Taysan; Conde Mataas; Mt. Banoy, peninsulas and Island south and east of Mabini, Batangas province
Age	Late Miocene - Early Pliocene
Previous Name	Calatagan Marl (Corby and others, 1951)
Renamed by	MGB (this volume)
Synonymy	Mapulo Limeston (Avilla, 1980), Dingle Limestone (Wolfe and others, 1980)

The Calatagan Formation was previously named Calatagan Marl by Corby and others (1951) for the exposures at Calatagan Peninsula. It is equivalent to the MApulo Limestone of Avila (1980). The formation may also be found in the peninsulas and islands south and east of Mabini, Batangas, as well as other areas of the province such as Taysan, Conde Mataas and Mt. Banoy. The Lithology varies from soft tuffaceous marine siltstone to coralline limestone. The limestone crops out at Brgy. Mapulo in Taysan, along the roadcut at Conde Mataas, Batangas City, and at the upper reaches of a major tributary of Talahib River and Laiya River where it overlies the Talahib Andesite. It is massive, white to buff, soft and porous with abundant coral fingers. Corby and others (1951) assign it an age of Late Miocene to Early Pliocene. It is also equivalent to the Dingle Formation of Wolfe and others (1980), which was estimated to be 100 m thick.

Pinamucan Formation
Lithology	Conglomerate, sandstone, shale, Pyroclastic rocks
Stratigraphic relations	Unconformable over the Tolos Quartz Diorite and San Juan Formation
Distribution	Upper Pinamucan, upper Calumpit and middle Lobo rivers; Batangas
Age	Pliocene
Named by	Avila (1980)

The Pinamucan Formation was named by Avila (1980) for the interbedded sequence of conglomerate, sandstone and shale that crop out in the vicinity of the upper Pinamucan, upper Calumpit and middle Lobo rivers, where they rest unconformably over the Tolos Quartz Diorite and metavolcanic rocks of the San Juan Formation. The conglomerate i poorly indurated but well-sorted with pebbles of andesite, diorite and metasediments set in a sandy tuffaceous matrix. The sandstone and shale are well-bedded, light brown to grayish, poorly indurated and tuffaeous. The upper horizon of this unit is intercalated with pyroclastic rocks designated by Avila (1980) as Lobo Agglomerate, which is here considered part of the Pinamucan. The formation is assigned a Pliocene age.

Mataas na Gulod Volcanic Complex
Lithology	Basalt andesite, breccia, pyroclastic rocks, lahar
Stratigraphic relations	Intrudes/covers Miocene rocks
Distribution	Cavite, Batangas
Age	Pliocene - Pleistocene
Named by	MGB (this volume)

In the western portion of Cavite, the Mataas na Gulod caldera complex, with a diameter of 3 km to 4.5 km, consists of pyroclastic flows and lahars. Breccia pipes cut through the western and southern flanks. The Mataas na Gulo belongs to the Bataan Volcanic Arc complex. South of the Mataas na Gulod, the Nasugbu plain surrounded by the composite cones of Mt. Palay-Palay, Mt. Caluya, Mt. Cariliao range from 3.4 to 1.34 Ma (De Boer and others, 1980; Wolfe and Self, 1983). Radiometric dating of the basalt flows from the volcano is reported to average 2.9 Ma (Wolfe and Self, 1983). The younger volcanic products are andesitic and a resurgent dome has risen 300 m above the caldera floor.

Macolod Volcanic Complex
Lithology	Basalt, andesite, dacite, tachyandestie, rhyolite, pyroclastic rocks, lahar
Stratigraphic relations	Intrudes/covers Miocene rocks
Distribution	Batangas, Laguna, Rizal, Quezon
Age	Pliocene - Recent
Named by	MGB (this volume)

Numerous Pliocene - Pleistocene volcanic centers, here grouped into the Macolod Volcanic Complex, are confined within a narrow structurally bounded northeast trending lineament called the Macolod Corridor (Forster and others 1990). This corridor is believed to be an acroos the arc extension region, a pull-apart type structure related to the sinistral extension region, a pull-apart type structure related to the sinistral movements of the Philippine Fault to the northeast and the Sibuyan Sea Fault to the southwest (Forster and others, 1990).The rifting process along thid corridor is accompanied by profuse volcanism, which could be associated with the subduction of the South China Sea Plate along the Manila Trench. Recent studies by Sudo and others (2000) indicate that there was a migration of active volcanisim from the Laguna de Bay area and Taal to the area of monogenetic volcanoes as a result of steeping of the subducted slab at the Manila Trench.

Major element data reveal that the volcanic rocks comprising the Macolod volcanic field have a wide range of composition from basalt to rhyolite,i.e., SiO2 = 47 - 74%.Intermediate rocks, however, are the most common. Basalts occur only in small monogenetic centers in the Macolod Corridor, while dacites and rhyolites seem to be exclusively present in the Lagua de Bay area and Mt. Makiling. The most primitive basalts attain MgO contents of 10-12 % and Cr concentrations of 580 ppm. The basalts are mostly calc-alkaline, evolving to high-K calc-alkaline for intermediate and evolved lavas. The Laguna de Bay lavas, in turn, are andesite to rhyolites that are bimodally calc-alkaline and high-K calk-alkaline. In summary, the geochemistry of the Macolod Volcanic Complex reflects that of subduction-related rocks. The rocks are characterized by low amounts of TiO2 (<1, 1%), enrichment in the large ion lithopile elements (Rb, Ba, Sr), Th and light rare earth elements (La, Ce), and depletion in high field strength elements (Nb, Zr, Ta) and the heavy rare earth elements, however, are interpreted to be due to crustal contamination and the involvement of sediments entrained by the subduction along the Manila Trench.. In addition, the involvement of continental material in the subduction process cannot be discounted due to the impingement of the Palawan-Mindoro continental block against southern Luzon. Radiometric K-Ar dating indicates that volcanic activities in the Macolod Corridor had started since 2.2 Ma (Sudo and others, 2000).

• Taal Volcano

Lake Taal is a volcano-tectonic depressionwith an approximately area of 300 km2, formed by numerous explosions, collapse craters and a system of tectonic grabens. Base surges and pyroclastic flows of the maar/caldera eruptions spread over an area of more than 2000 km2; crossing the 640 m high Tagaytay ridge towards Manila Bay to the north; flowing southward to Balayan and Batangas bays; depositing up to 300 m of pyroclastics to the east in the Mt. Makiling - Mt. Malepunyo - San Pablo area; and entering the Nasugbu plain through a gap between Mt. Butalao and Mt. Cariliao to the west. Two composite cones, Mts. Sungay and Macolod, developed on the easter side of the lake. Radiometric K-Ar dating of samples from Mt. Macolod gave values of 2.22 += 0.10 Ma (Sudo and others, 2000) and 2.03 +-0.30 Ma (Oles and others, 1991), indicating that volcanic activity started since 2.2 Ma.

Near the center of Taal Lake is Taal volcano, an active volcano covering around 23 km2 and reaching up to 311 masl high (PHIVOLCS, 1995). Numerous tuff and scoria cones and depressions formed by explosion, collapse or ground subsidence are distributed on the volcano island. Of the 35 identified cones, 26 are tuff cones, 5 are cinder cones and 4 are maars. The main crater, 1.9 km in diameter, is a lake with a 100 m2 islet interpreted to be a lava needle (Oles and others, 1991). Altered grounds and streaming vents attest to the thermal activity in the island, whereas base surge and airfall deposits indicate past phreatic and phreatomagmatic eruptions. At least 33 historic eruptions of Taal Volcano have been recorded from 1572 to 1977.Aside from the main crater, other major eruptions centers are Binintiang Munti, Pira-piraso, major eruption centers are Binintiang Malaki, Binintiang Munti, Pira-piraso, Calauit and Mt. Tabaro (PHIVOLCS, 1995). Caldera formation was characterized by voluminous unloading of calc-alkaline andesitic to dacitic magma that deposited pumice flows, ignimbrite, scoria agglutinate and scoria flows (Listanco, 1994). The current active phase of the volcano culminated in the development of Volcano Island. Recent eruptions of Taal produced basaltic and andesitic deposits.

• Makiling - Malepunyo

Mt. Makiling, located on the southwest rim of Laguna de Bay, is a stratovolcano with a 16 km diameter that reaches up to 1115 masl elevation. Pyroclastic flow, lahar, airfall and lava deposits comprise the cone. The lavas consist of tachyandesite, tachydacites and rhyolite. Plinian-type eruption is evidenced by welded ash-flow tuffs. Radiometric K-Ar ages of 0.51 to 0.18 Ma have been determined for andesites and dacites of Mt. Makiling (Wolfe and Self, 1983). Smaller satellitic edifices include La Mesa tuff ring, Bijiang , Mapinggon and Masaia.

Immediately south of Mt. Makiling is a deeply eroded north-south trending volcano range that includes Mapinggon, Bulalo and Malepunyo. This composite volcano consists predominantly of lava flows and breccias at the upper portions and pyorclastic flows and lahars on its eastern flanks. Andsites from Mt. Malepunyo re dated from 1.10 Ma to 0.63 Ma (De Boer and others, 1980; Oles and others, 1991).

Other smaller monogenetic cones in the Macolod Corridor erupted basaltic lava. Scoria cones and tuff cones are common, the former being formed from strombolian-type eruptions. Maars and tuff rings in the San Pablo area show typical features of bse surge and airfall deposits resulting from phreatic or phreatomagmatic eruptions. Andesites from Mt. Atimbia, one of the cones in San Pablo, gave an age range of 1.08 to 0.95 Ma. The youngest radiometric K-Ar dating obtained from a dacite sample from Mt. Mapinggongave an age of 0.10 += 0.02 Ma. Scoria cones in Batangas include Anilao Hill, Tombol Hill and Soroso Hill. A radiometric K-Ar age of 0.87 Ma was obtained from a sample of basalt from Anilao Hill (Oles and Others, 1991).

• Laguna de Bai

Northeast of Taal Volcano is Laguna de Bai, the largest volcano tectonic depression in this region formed by caldera eruptions and extension tectonics. Collapse structures bounding this lake suggest that is probablya relic of a much larger ancient caldera system. To the west and south of the lake are the volcanic and pyroclastic deposits of the Taal - Banahaw area. The Caliraya plateau on the eastern side of the lake represent a >400-m thick volcano-sedimentary sequence composed of welded and unwelded pyroclastic flows intercalated with lava flows, lahars, airfall tuff, base surges and fluvial and lacustrine sediments. To the north, limestones and small plutons are exposed within the pyroclastic series. Graben tectonics divided the lake into three bays. The East and Middle bays are seperated by the Jala - Jala peninsula, which host three domes including Mt. Sembrano. Talim Island, intruded by the Mt. Sangunsalaga dome and the Binangonan peninsula, isolates the Middle from the West bay. Andesites from around Laguna de Bai give radiometricK-Ar whole rock ages of 2.3 to 1.7 Ma (Sudo and others, 2000).Recent studies by Catane and Arpa (1999) suggest a resumption of volcanic activity in the Laguna de Bai area 47,000 to 27,000 yrs BP after a cessation of volcanic activity that could have lasted for a million years.

Banahaw Volcanic Complex
Lithology	Basalt, andesite, breccia, pyroclastic flows, lahar
Stratigraphic relations	Intrudes/covers Miocene rocks
Distribution	Laguna and Quezon
Age	Pleistocene - Recent
Named by	MGB (this volume)

Mt. Banahaw is the highest volcanic center in southern Luzon, reeaching up to 2158 masl. This stratovolcano includes two major flank cones, Mt. San Cristobal (1470 m) and Banahaw de Lucban (1870 m). Low-lying domes (Buho and Masalakot) and Mt. Mayabobo, a cinder cone, are also part of this volcanic complex. The Banahaw Volcanic Complex isconsidered part of the southern segment of the Luzon volcanic arc associated with the subduction of the South China Sea plate along the Manila Trench. The segment to which Banahaw belongs was designated by Defant and others (1988) as the eastern counterpart of the Mindoro volcanic belt.

Mt. Banahaw consists of lava flows and breccias on the upper regions and lahars and pyroclastic flows below elevations of 800 to 600 masl. While Mt. San Cristobal is a complex lava dome structure, Mt. Banahaw de Lucban is characterized by a dome that caused debris-avalanche on the eastern flanks. Mt. San Cristobal basalts and andesites range in age from 1.71 to 1.29 Ma (Oles and others, 1991). Accounts of Mt. Banahaw eruptions date back to 1730, 1743 and 1909 (PHIVOLCS, 1997).

SOUTHERN SIERRA MADRE

The stratigraphy of Southern Sierra Madre is subdivided into two blocs, namely: (1) Polillo Group of Islands, including the coastal areas of the eastern part of the mainland (Infanta Strip), and (2) the southern Sierra Madre mainland that embraces portion of Aurora, Nueva Ecija, Bulacan, Rizal and Quezon. Ophiolites constitute the basement of both blocs.

Polillo Group of Islands – Infanta Strip

Buhang Ophiolitic Complex
Lithology	Pyroxenite, gabbro, amphibolites, pillow basalt
Stratigraphic relations	Constitutes the basement of Polillo Island;Overlain by Bordeos Formation
Distribution	Buhang Point and Sabang Polillo Island;Jomalig and Canaway Islands
Age	Cretaceous
Previous name	Buhang Point Meta-ophiolite (Billedo, 1994)
Renamed by	MGB (this volume)
Correlation	Dibut Bay Metaophiolite of Isabela Ophiolite, Katablingan Metamorphics (Angeles and Perez, 1977)

The Buhang Ophiolitic Complex was name by Billedo (1994) Buhang Point Meta-ophiolite for the exposures of serpentinized pyroxenite, gabbros and minor amphiolite at Buhang Point, Polillo Island. Small exposures of isolated ultramafic rocks were also reported east-sooutheast of Barrio Sabang, south of Polillo town.

The volcanic carapace of the ophiolites is represented by outcrops of pillow basalt in Polillo Island, Jomalig Island and Canaway Island (at the eastern extremity of jomalig Island and Canaway Island (at the eastern extremity of Jomalig Island). In Polillo Island, an outcrop along the beach shows pillow basalt together with its reddish pelagic interstices. It is intruded by a quartz monzonite probably belonging to the Polillo Diorite. The pillow basalts are unconformably overlain by late Oligocene to Early Miocene arkosic limestone belonging to the Bordeos Formation. At Canaway Island, the rocks are composed of elongated chloritized and secricitized pillow basalt with reddish chert interstices. The pillow basalt and the chert seem to have undergone low-grade metamorphism characterized by greenschist facies. Jomalig Island is underlain entirely by volcanic flows and breccias, which have undergone greenschist facies metamorphism.

Radiometric K-Ar dating of a sample of highly foliated gabbro at Buhang Point was dated 63.68 ± 1.79 Ma equivalent to latest Cretaceous. Its geochemical characteristics show an island arc affinity (Billedo, 1994).

The Buhang Ophiolite is probably equivalent to the meta-ophiolites designated as Katablingan Metamorphics by Angeles and Perez (1977) and adopted by Revilla and Malaca (1987). It consist mainly of amphibolites with associated gabbros (Ringenbach, 1992) and exposed east of the Philippine Fault near Infanta, opposite Polillo Island. The Buhang is also correlated to the Dibut Bay Meta-ophiolite found in northeastern Luzon and is thought to represent the metamorphosed equivalent of the Isabela Ophiolite.

Quidadanom Schist
Lithology	Tremolite-actinolite-chlorite schist, feldspar-mica schist phyllite
Stratigraphic relations	Unconformable over Buhang Ophiolitic Complex
Distribution	western part of Polillo Island
Age	Late Cretaceous
Named by	Fernandez and others (1967)
Correlation	Lubingan Formation

The Quidadanom Schist was named by Fernandez and other (1967) for the low-grade metamorphosed sedimentary rocks, including small lenses of marble exposed at barrio Quindadanom. The formation occupies the western portions of Polillo Island occurring as patches from Binibitinan Malaki River in the north extending southwards to Barrio Masisi up to Barrio Agta on the south. In Anawan Malaki River, the quidadanom Schist is composed of tremolite-actinolite-chlorite schist, phyllite and minor feldspar-mica schist. The formation is apparently unconformable over the Buhang Ophiolitic Complex. The Protolith of the Quidadanom Schist could even represent the sedimentary cover of the ophiolite.

A metamorphosed limestone sample was dated Late Cretaceous (?) on the basis of Radiolarians (Dewever, 1994). The Quidadanom Schist is correlated with the late Cretaceous Lubingan Formation (see discussion under Northern Sierra Madre-Caraballo) in northeastern Luzon. The Units described above are highly indurated and exhibit low-angle bedding schistosity dipping to the east.

Anawan Formation
Lithology	Tuffaceous sandstone, shale, volcanic breccia
Stratigraphic relations	Unconformable over the Quidadanom Schist; overlain by Babacolan Formation
Distribution	Polillo Island
Age	Early Eocene(?)
Named by	Fernandez and others (1967)
Synonymy	Lubi Formation (Magpantay, 1955)
Correlation	Tamala Formation

The Anawan Formation was named by Fernandez and others (1967) for the volcano-sedimentary sequence at Anawan, Polillo Island. It consists of bedded tuffaceous sandstone and shale containing occasional volcanic breccias. This formation overlies unconformably the Quidadanom Schist. Fernandez and others (1967) divided the Anawan Formation into a lower volcanic member and an upper volcano-sedimentary member. The volcanic member is mainly exposed in the central portions of the island while outcrops of the sedimentary member found mainly along the western coastlines are very limited. Outcrops of basalts exhibiting pillow structures were likewise observed in barangays Tawi, Malagas and Milawid.

The lower undeformed portions of this formation, as observed northeast of Buhang point, are made up of a basal conglomerate containing reworked clasts of gabbro, reddish pelagic limestone, greenschist, basalt, andesite and sandstone. A sub-vertical fault contact was inferred between the basal conglomerate of this formation and rocks of the Buhang Ophiolitic Complex.

The Anawan Formation is equivalent to the Lubi Formation of Magpantay (1955) and BMG (1981) and adopted here because the section at Anawan is considered more complete. The Anawan Formation is probably equivalent to the Tamala Formation on the Infanta strip opposite Polillo Island. The Tamala is a weakly metamorphosed sequence of basaltic flows (including pillow lavas) and minor marbleized limestones (Ringenbach, 1992). It is overlain by the Marcelino Point Limestone, which has been dated early Middle Eocene (Ringenbach, 1992). This limestone unit, which is a dark gray to black bioclastic limestone with numerous Nummulites and Alveolina, is considered by Ringenbach (1992) to be most likely unconformable over the Tamala Formation.

Babacolan Formation
Lithology	Limestone, calcareous shale, sandstone
Stratigraphic relations	Not reported
Distribution	Polillo Island
Age	Late Eocene
Thickness	160 m
Named by	De los Santos and Spencer (1957)

A sequence of thin lenticular bodies of limestone with interbeds of indurated dark gray calcareous shale and sandstone with interbeds of black calcareous layers were designated as Babacolan Formation by De los Santos and Spencer (1957) and adopted by BMG (1981). These lenticular limestone bodies were observed along Quinbawan Creek, Bayabas River, west of Bordeos along the shore south of Buhang Point, Panikulan and along the western and southern flanks of Anibawan River valley. The thickness of the formation was estimated to be 160 m. A sample of this limestone collected in Babacolan Creek, north of Bordeos, yielded Late Eocene assemblages as indicate by the presence of several species of Pellatispira and Discocyclina (BMG, 1981).

Billedo (1994) considered the limestone bodies as the upper member of the Anawan Formation and designated it as the Babacolan Limestone Member. The formation is reported to lie unconformably over the Lubi Formation of Magpantay (1955) and BMG (1981).

Polillo Diorite
Lithology	Quartz diorite, hornblende-biotite diorite, minor granodiorite, gabbro and aplites
Stratigraphic relations	Intrudes the Anawan Formation
Distribution	Polillo Island
Age	Early Oligocene
Named by	Fernandez and others (1967)
Synonymy	Bisilian Quartz Diorite (Magpantay, 1955)
Correlation	Lupa Granodiorite (Revilla and Malaca, 1987)

The Polillo Diorite was named by Fernandez and others (1967) for the plutonic intrusive complex intrudiong the Anawan Formation in the southern axial Portion of the Polillo Isand. The leucocratic rock in the southern Polillo Island named Baslian Quartz Diorite (Magpantay, 1955) refers to the same intrusive body (BMG, 1981). The largest intrusive mass is exposed from Mount Malolod to the southern tip of Polillo Island (BMG, 1981).

Detailed investigation by geologist of Essex Mineral Company led to the distinction of five main types of intrusive rocks plus a number of subtypes (Burton, 1985). The main types of: (1) quartz diorite, (2) granodiorite, (3) granodiorite-monzonite, (4) a plug of quartz monzonite, and (5) quartz monzonite porphyry. Gabbroic phases occur as thin layers, and aplites as thin dikes. It is believed that these rocks are comagmatic and were probably intruded in the order as enumerated above, derived from a calc-alkaline magma of gabbroic composition (Tulleman’s written communication to Burton, in Burton, 1985). Quartz diorite and horneblende-biotite diorite predominate over the associated phases of the intrusive.

The diorite consists principally of intermediate feldspar (70%) and minor hornblende (15%) and quartz (10%). Accessory minerals are sericite, magnetite, pyrite and apatite. The granodiorite phase crops out near contact zones. The granodiorite has about has about 10% potash feldspar, mainly anhedral orthoclase and rarely perthites. Ferromagnesian minerals are fresh green horneblende and minor amounts of chlorite and biotite. Intermediate plagioclase is about 40% and quartz is 20% of the rock volume. Accessory minerals are apatite, magnetite, zircon and epidote.

Radiometric Rb-Sr dating of this intrusive was reported by Knittel (1985) to be 34.4 ± 1.2 Ma (early Early Oligocene).

The Lupa Granodiorite of Revilla and Malaca (1987) could be equivalent to the Polillo Diorite.

Bordeos Formation
Lithology	Sandstones, shale and conglomerate with limestone lenses and coal seams
Stratigraphic relations	Unconformable over the Babacolan Formation
Distribution	Polillo Island
Age	Late Oligocene – Early Miocene
Thickness	160 m (maximum)
Named by	Magpantay (1955)

The Bordeos formation, which was designated by Magpantay (1955), is found mainly on the eastern side of Polillo Island, where it forms an irregular sinuous belt extending from Barangay Maknit on the south to Anibawan River on the north. It is composed of well-bedded sandstone, shale and conglomerate with limestone lenses and coal seams (measuring an average of 35 cm thick and 8 m long) near the base. Sandstone dominates the series and is pale to dark gray in color, having clasts mostly of volcanic provenance and is often pebbly and sometimes grades into conglomerate. Minor limestone interbeds rarely exceeds 10 m in thickness. The Bordeos Formation unconformably rests on the Babacolan Formation and the Polillo Diorite (Fernandez and Abarquez, 1967; Knittel, 1985). A well-defined unconformity is observed at the base of the Bordeos formation, which is traceable for several kilometers. The thickness of this formation ranges from 15 m to 160 m. Alberding (1939), Magpantay (1955) De los Santos and Spencer (1957) and Fernandez and others (1967) date the Bordeos as Early to Middle Miocene. However, BMG (1981) re-examined the fossils obtained from previous samples and found out that the age of this formation was actually Late Oligocene to Early Miocene. Microfossils in arkosic limestone sampled by Billedo (1994) also indicate a Late Oligocene to Early Miocene age for the formation.

Langoyen Formation
Lithology	Limestone
Stratigraphic relations	Unconformable over the Bordeos Formation
Distribution	Eastern coast of Polillo Island
Age	Late Early Miocene- early Middle Miocene
Thickness	56 m (maximum)
Named by	Billedo (1994)

A limestone body underlying low gentle hills and scattered as small patches along the eastern coast, north and south of Bordeos was designated by Billedo (1994) as Langoyen Limestone. The Langoyen Limestone appears to be discontinuous, lenticular, and partly coralline, with a maximum thickness of 56 m. It crops out along Bordeos River, Sumuot Creek and at Sabang within the municipality of Bordeos. The limestone unconformably overlies a thin sequence of dark gray green sandstone belonging to the upper portions of the Bordeos Formation. The unconformity is marked by a slight angular discordance, characterized by minor differences in the strike and dip of the beds near the contact. A dating of early Middle Miocene was assigned by BMG (1981) for this formation on the basis of large foraminifera (Miogypsina, Lepidocyclina and Austrotrillana) contained in somesamples. An age range of late Early Miocene to Early Middle Miocene is adopted here on the basis of recent determinations reported by Billedo (1994).

Patnanongan Formation
Lithology	Sandstones, shale, conglomerate, Limestone, calcarenite
Stratigraphic relations	Not reported
Distribution	Patnanongan island; Palasan and Karlagan Islands
Age	early Middle Miocene – Late Miocene
Thickness	350 m
Named by	Fernandez and others (1967)

The Patnanongan Formation was first described by Fernandez and others (1967) after the sedimentary sequence observed in the island of Patnanongan, east of Polillo Island. The bulk of the Patnanongan Formation is largely exposed in Patnanongan Island, the type locality, in Palasan Island, the east of karlagan represented by small and scattered inliers of limestone patches in the Pliocene Karlagan Formation. The formation is composed of brown to gray, slightly indurated interbedded sandstones, shale, calcarenite, limestone and a molasse – type conglomerate. Molluscan fossils are present in the sandstones and shale beds. The limestone is of two types. The first is massive, buff to flesh to brown, hard, fine- to medium – grained and wih abundant shelss. The other is massive to crudely bedded with colors ranging from brown to flesh, cream and pink. The conglomerates contain pebbles and cobbles of previously emplaced and deposited rocks including the Laangoyen Limestone. The formation can be divided into a lower sequence made up of mostly of green calcareous sandstone and mudstone and an upper member consisting largely of molasse type of conglomerate. The average thickness of this formation is 350 m. This sedimentary sequence was given an age ranging from late Middle Miocene to Late Miocene (BMG, 1981). Billedo 91994) reports a nannoplankton age dating of early Middle Miocene to late Miocene is adopted here.

Karlagan Formation
Lithology	Shale and mudstone with occasional lenses of conglomerate and limestone
Stratigraphic relations	Unconformable over older formations
Distribution	Karlagan Island; Polillo Island
Age	Pliocene
Thickness	Not reported
Named by	Fernandez and others (1967)

The youngest formation, which blankets Karlagan Island and the northern portions of Polillo Island, is known as the Karlagan Formation (Fernandez and others, 1967). This rock unit is composed of pale to dark gray fossiliferous shale, mudstone, occasional lenses of conglomerate and limestone. Outcrops are characterized by a near – horizontal alternating sequence of thinly (few centimeters) to thickly bedded (2 m) shale and mudstone, with occasional lenses and conglomerate. The shale and mudstone are well-bedded, brown to dark gray and fossiliferous. The limestone is cream to flesh, coralline and fossiliferous. Fossil assemblages indicate a Pliocene age. The Karlagan Formation rests unconformably over the older rock units on Polillo Island.

Southern Sierra Madre Mainland

Montalbam Ophiolite Complex
Lithology	Gabbro, sheeted diabase dike complex,pillow basalt, pelagic sedimentary rocks, plagiogranite
Stratigraphic relations	Constitutes the basement of southern Sierra Madre
Distribution	Montalban, Rizal, Bulacan, Nueva Ecija
Age	early Late Cretaceous
Previous name	Angat Ophiolite (Karig, 1983)
Renamed by	MGB (this volume)

The oldest rock is Southern Sierra Madre comprise an incomplete ophiolitic sequence called Angat Ophiolite by Karig (1983) for the gabbros exposed at Angat, Bulacan. Exposures of the components of the ophiolite define a nearly north-south belt from Montalban, Rizal through eastern Bulacan to Nueva Ecija, just south of the Laur-Dingalan portion of the Philippine Fault. Rigenbach (1992) asserts that the best known exposures are found in the Montalban area. Because of the precedence of the name Angat for the Early-Middle Miocene sedimentary rocks in the locality, the name Montalban Ophiolitic Complex is here proposed to replace the appellation of the ophiolitic unit. The ophiolitic sequence consists of layered and massive gabbro, sheeted diabase dike complex, pillow basalts and turbidic sedimentary rocks (Arcilla, 1983). The gabbros include low level layered gabbro and upper level isotropic norites and olivine gabbros. Minor plagiogranites are localized at gabbro-diabase contacts. Arcilla (1983) proposed the name COGEO Basalt for the pillow basalts, which are typically exposed at COGEO (Confideration of Government Employees Organizations) housing area and vicinity, including Nangka River. Other good exposures could befound in Angono, Taytay, Wawa area,as well as Puray and Tayabasan rivers. Pillow structures of the basalt average 1 -1.5 m. the lower section of the basalt apparently grades into sheeted dike complex, while the upper sections are interlayered with thin beds of ferruginous, siliceous red mudstone (Arcilla, 1983, 1991). The aggregate thickness of the pillow basalts exceeds 300 m in some sections (Arcilla, 1983). According to Arcilla (1991), the lower basalts of the ophiolite have MORB characteristics while the upper andesite-basalt section has an Island Arc Tholeiite (IAT) signature. The sedimentary cover of the ophiolitic sequence is separately designated as the kinabuan Formation.

A Turonian age (early Late Cretaceous) based on paleontologic dating of red siliceous mudstone intermixed with pillow basalt was reported by Revilla and Malaca (1987). Similarly, Arcilla (1991) gives a Turonian-Coniacian age for the turbidites just above thepillow basalts along Tayabasan River, on the basis of radiolarians and pelagic foraminifera. The Montalban is therefore dated early Late Cretaceous.

The Barenas-BAito Formation (see description under Central Luzon Basin-East) of Revilla and Malaca (1987) is a volcanic-sedimentary sequence, which includes the pillow basalts of the Montalban Ophiolitic Complex.

Kinabuan Formation
Lithology	Sandstone, shale, limestone, calcarenite,Calcilutite
Stratigraphic relations	Comprises the sedimentary cover of the Montalban Ophiolitic Complex;overlain by the Maybangain Formation
Distribution	Kinabuan Creek, Sta Ines, Antipolo, Rizal;Tatlong K, Pinugay (Philcomsat), Macaira,Sampaloc-Daraitan road and along Malinaw, Alas-Asin, Toyang and Mamuyao creeks
Age	Late Cretaceous
Thickness	>800 m
Named by	Barenas-Baito Formation (Revilla and Malaca, 1987) Tamala formation (Angeles and Perez, 1977)
Synonymy	Barenas-Baito Formation (Revilla and Malaca, 1987) Tamala formation (Angeles and Perez, 1977)

The kinabuan Formation was named by Melendres and versoza 91960) for the flysch-like sedimentary deposits along Kinabuan Creek, a tributary of Lenatin River, north of Santa ines, Antipolo, Rizal. The basal part of the sedimentary sequence is associated with underlying pillow basalts and basaltic breccias. The basalts represent the volcanic carapace of the ophiolite, whereas the pelagic sedimentary sequence constitutes the sedimentary cover of the Montalban ophiolitic Complex. This sedimentary sequence consists of thinly interbedded silty shale and calcareous sandstones with tuffaceous and siliceous layers capped by steeply dipping thin beds of limestone. Outcrops of the Kinabuan can also be found in Tatlong K, Marcos Highway from Masinag to Foremost farms, Pinugay (Philcomsat), Macaira, Sampaloc-Daraitan road along Malinaw, Alas-Asin, Toyang and Mamuyao creeks. The sedimentary sequence of Kinabuan has an estimated thickness of 800 m. Although the formation has not formally been subdivided, it is clear that there is a lower volcanic member, middle sandstone-shale member and an upper limestone member.

Haeck (1987) described the lower part of the sedimentary sequence as composed of tan to gray , fine to medium – grained calcarenite and calcisiltite, buff to gray pelagic limestone and much less common, tan, medium- to coarse-grained calcareous lithic to feldspathic arenite interbedded with black organic to light gray calcareous shale.

The upper limestone member (Reyes and Ordoñez,1970) is composed of white to buff (weathered), light to dark gray (fresh) pelagic limestones and minor light to dark gray calcarenite and calcisiltite with rare interbeds of calcareous shale. The limestone contain radiolarians, indicating a bathyal depositional environment (Ringenbach, 1992).

The Kinabuan has been dated Santonian to Early Maastrichtian based on planktonic foraminifera (Reyes and Ordonez, 1970; Hashimoto and others, 1979; Haeck, 1987). However, Arcilla (1992) reports a Turonian age for the formation on the basis of radiolarians and pelagic foraminifera.

The Barenas-Baito Formation (Revilla and Malaca, 1987) and Tamala Formation of Angeles and Perez (1977) are probably equivalent to the Kinabuan Formation.

Maybangain Formation
Lithology	Masungi Limestone member, Clastic-volcanicmember – volcanic breccias, sandstones,siltstone, mudstone, conglomerate
Stratigraphic relations	Conformable over the Kinabuan Formation;Unconformably overlain by the Binangonan Formation
Distribution	Maybangain Creek, Sampaloc, Antipolo, Rizal; Umiray. Limutan and Makalya Rivers; at Alas-asin, Macaira and along the Tanay- Daraitan road
Age	Middle Paleocene – Middle Eocene
Thickness	over 2,500 m
Named by	Melendres and Versoza (1960)
Synonymy	Kanan formation (Revilla and Malaca, 1987), Marcelino Point Limestone (Ringenbach, 1992)
Correlation	bayabas Formation (Revilla and Malaca 1987)

Conformably overlying the Kinabua Formation is the Maybangain Formation. The name was introduced by Melendres and Versoza (1960) for the rocks typically exposed along Maybangain Creek between sitios Batangas and San Andres, Sampaloc, Tanay, Rizal. The type Locality is about 3.5 kilometers north-northeast of Mt. Masungi. The formation crops out at the Midland Cement Company quarry site,along Umiray, Limutan and Makalya rivers, at Alas-asin, Macaira and along the Tanay-Daraitan road. Conformably overlying the Kinabuan, this formation consists of the lower Masungi Limestone Member and an overlying or partly intertonguing clastic-volcanic member.

A study by Ocampo and Martin (1967) regards the masungi Limestone as biohermal. However, exposures encountered by Haeck (1987) are interpreted to be lower-slope or basin margin deposits in a fore-reef setting. The outcrops consist mainly of redeposited limestones, including debris flows and turbiditic strata, which are intrerbedded with calcareous and non_calcareous mudstones and minor volcaniclastic rocks. Ringenbach (1992) considers the biohermal limestones of Ocampo and Martin (1967) as olistolith of the volcaniclastic member.

The clastic-volcanic member consists mostly of a thick sequence (more than 2,500 m) of volcanic and clastic rocks. It occupies much of the area west of the Masungi Limestone. It also occurs less extensively along Tanay river from Daranak Falls upstream to the western vicinity of Dagat-dagatan. Schoell and Duyanen (1988) distinguish for sub-members. The Kay-ibon sub-member is a 1,200 m thick pile of turbiditic volcanogenic sandstones and silttones with minor mudstones. This sub-meter contains two major olistostromes, the lower layer consisting of the Masungi LImestone and the upper layer having gravity slides and olistoliths of the Kinabuan Formation. The Susongdalaga sub-meter is a 400-m thick sequence of sandstones, volcanic breccias and conglomerate. The Kanumay sub-meter is 900-m of turbiditic sandstones and siltstones while the uppermost 250-m thick San Ysiro sub-meter is similar to the Susongdalaga.

The MAybangain Formation is probably equivalent to the Eocene Formation of Antonio (1967) in Sta. Ines, Antipolo, Rizal and the Bayabas Formation of Revilla and Malaca (1987) in the eastern part of the Central Luzon Basin.

An age range of uppermost Paleocene (Thanetian) to Middle Eocene (Lower Lutetian) was formerly assigned to this formation (BMG, 1981) on the basis of larger foraminifera as reported by Reyes and Ordenez (1970) and Hashimoto and others (1979). Haeck (1987) finds fossils of Middle Paleocene (Igorina pusilla pusilla) to Middle Eocene (Globigerinatheca subconglobata) ages in calcareous turbidites of the Masungi Limestone member of this formation. More recently Ringenbach (1992) gives a dating of Early Middle Paleocene (Subbotina pseudobulloides) to Late Paleocene (Igorina pusilla, Planorotalites pseudomenardii) for the pelagic limestones west of Urimay, which he considers as a part of the Masungi Limestone member of the Maybangain. An age range of Early/Middle Paleocene to Middle Eocene ws adopted by MGB (2004) for this formation.

The Marcelino Point Limestone north of Infanta (Rigenbach, 1992) is probablt equivalent to the Masungi Limestone. The Kanan Formation of Revilla and Malaca (1987), consisting of basaltic and andesitic volcanic rocks and volcaniclastic, is probably equivalent to the volcano-clastic member of the Maybangain Formation.

Sta Ines Diorite
Lithology	Horneblende diorite; minor quartz diorite
Stratigraphic realtions	Intrudes Kinabuan and Maybangain Formations
Distribution	Antipolo-Teresa road; Mt. Masarat at Sta. Ines; Mt. Mayapa, Mt. Retablo and Mt. Maon at Bulacan; Putingbato and Kaybagsik, Antipolo; along upper Mangga Creek (tributary of Madlum River), Talaguio River and Ipunan Creek (tributary of Angat River),Singalong Creek and upper Maputi and Magsuong Rivers
Age	Late Eocene
Previous name	Antipolo Diorite (BMG, 1981)
Renamed by	MGB (this volume)

The diorite intruding Cretaceous to Eocene sedimentary units along the Antipolo-Teresa road was designated by BMG (1981) as Antipolo Diorite. It is here renamed Sta. Ines Diorite. Sta. Ines Diorite was named by Antonin (1967) for the exposures at Mt. Masarat in barrio Sta. Ines, Tanay Rizal. The diorite, which intrudes limestone and clastic rocks, is associated with pyrometasonic deposits of iron ore.

At Sta. Ines, the diorite occurs as a stock measuring about 3 km along its length on the eastern and northeastern slopes of Mt. Masarat. A much bigger body, however, underlies Mt. Mayapa and Mt. Maon in Dona Remedios Trinidad and Norzagaray, Bulacan. Exposures of the diorite are also found around Mt. Retablo; at Putingbato and Kaybagsik, Antipolo; along upper Mangga Creek (Revilla and Malaca, 1987). The dominant rock type is medium to coarse-grained hornblende diorite with local quartz diorite, gabbro and diabase facies, Diorite also occurs as dikes and sills intruding sedimentary rocks.

Antonio (1967) presumed that the sedimentaryrock intruded by the diorite is equivalent to the Early Miocene Angat Formation. Revilla and Malaca (1987), however, report that the Angat Formation rests unconformably over the diorite inn Bulacan. Radiometric K-Ar dating (36.9 Ma reveals an Early Eocene age for the diorite (Wolfe, 1981).

Binangonan Formation
Lithology	lower Teresa Siltstone member - siltstone, marl
Stratigraphic relations	Unconformable oer the Maybangain Formation
Distribution	Binangonan, Teresa, and Antipolo in Rizal; Coronel River and Mt. Dalumpa west of Ligaya and Gabaldon, Nueva Ecija
Age	Late Oligocene - Early Miocene
Thickness	Teresa Siltstone - 350 m, Limestone - 900 m
Previous name	Binangonan Limestone (Smith, 1906)
Renamed by	BMG (1981)
Synonymy	Maysawa Formation (Haeck, 1987), Montalban Formation (Baumann and others, 1976)
Correlation	Bugnam Formation (Rutland, 1968), Villa Wave Formation (Rutland, 1968)

The Binangonan Limestone of Smith (1906) was renamed by BMG (1981) as Binangonan Formation rests unconformably over the Maybangain Formation. On its Western side, the formation is in fault contact with the Antipolo Diorite (Foronda and Schoell, 1987). Outcrops of Binangonan Formation are exposed in Binagonan, Teresa, and Antipolo, all in Rizal Province. Exposures were also observed on the N-S tributaries of the Coronel River, which flow in the Gabaldon Basin and also at Mt. Dalumpa

The Teresa Siltstone and the Limestone are treated here as the lower and upper members, respectively, of the Binangonan Formation. The Teresa Siltstone is essentially a 350-m thick sequence of tuffaceous calcareous siltstones and marl deposited by turbidity currents in a shallow basin (Schoell and Fuentes, 1989; Schoell and Casero 1989). the overall sedimentological characteristics of the unit, as observed by Foronda and Schoell (1987), suggest that the unit represents shallow water proximal turbidites. The upper Limestone Member is massive, light cream to pink to bluish gray and fossil-rich. This carbonate unit, which attains a thickness of 900 m, represents deposits of shallow-water reef complexes.

This formation shows facies variation in the northern part of the Southern Sierra Madre. Along the Tributaries of Coronel River and Mt. Dalumpa west of Ligaya and Gabaldon, Nueva Ecija, the formation is characterized by smaller proportions of limestone compared with associated clastic rocks consisting of conglomerates, tuffaceous sandstones, siltstone and mudstones. Wesstof Umiray, the limestone is locally more than 300 m thick topped by sandstones and conglomerates with reworked limestone clasts (Ringenbach, 1992). In Bugnam Creek east of Dalumpa Peak, volcanic rocks have been observed to be interbedded with the volcaniclastics of the Binangonan Formation (Ringenbach, 1992) Coal beds and lenses have also been noted by Revilla and Malaca (1987) in the sandstone-shale sequences in Makalya and Lagmak areas.

Previously this formation was assigned a LAte Oligocene age (BMG, 1981) base on datings by Smith (1906), Yabe and Hanzawa (1929) and Hashimoto and Balce (1977). However, recent paleontological dating of samples from this formation revals that it extends up to Early Miocene (Foronda and Schoell, 1987; Revilla and Malaca, 1987; Ringenbach, 1992). Radiometric K-Ar dating of a basalt flow associated with this formation gave 22.92 + 1.12 Ma, equivalent to earliest Miocene (Ringenbach, 1992). An age range of Late Oligocene to Early Miocene is now adopted for this formation.

The Maysawa formation of Haeck (1987) is considered to be a deeper facies of the Binangonan Formation although it does not have a clastic member/ Also probably equivalent to Binangonan Formation is the 1,300-m thick Montalban Formation of Baumann and others (1976), which is consist of basal limestone member, a late Lae Oligocene wacke-mudstone member and an Uppermost early Miocene micritic limestone member. In the northern part of Southern Sierra Madre, the Binangonan Formation is also probably equivalent to the Bugman and Villa Wave formations of Rutland (1968), which consist of dark shales, conglomerates and minor limestone.

Angat Formation
Lithology	Lower clastic member - shale, sandstones, sandy limestone, Upper limestone member
Stratigraphic relations	Overlies Barenas-Baito, Bayabas and Binangonan formations and the Sta. Ines Diorite; conformably overlain by the Madlum Formation
Distribution	Angat Limestone member of Quezon Formation
Named by	Corby and others, 1951
Renamed by	Gonzales and other (1971)

Corby and others (1951) originally asigned the term Angat to the lower limestone member of the Quezon Formation in the Angat River area. Gonzales and others (1971) raise the rock unit to formation rank and included a lower clastic facies. The formation's type locality is along Angat River roughly 6 km east of Norzagaray. Along the western flank of Sierra MAdre, the fomations forms a more or less continuous and approximately north-south belt, which splits into two at the Camachile River in the eastern Bulacan. The smaller western edge ends at Balite Creek about 4 km northeast of Norzagaray and the eastern strip streches for about 1.5 km south of Angat River. In addition, outcrops of the formation havealso been observed along the Rio Chico and Sumacbao rivers on the northwestern flank of the southern Sierra Madre. The thickeness of the Formation. The thickeness of the formation varies from one locality to another, but its maximum expoed thickness is about 1,950 meters. The formation consists of a lower clastic member representing a minor part of the formation and a upper limestone member.

The clastic member is made up of thin beds of calcareous shale and clayey sandstone with occasional lenses of sandy limestone. The sandstones is normally graded and well-cemented while the limestone lenses are dense, brittle and partly siliceous. Mollusks, corals stems and laminae of carboneceous materials are dispersed within the section. These, together with the abundance of Helicosphaera species, suggest shallow marine deposition. The sequence interfingers with the lower part of the upper limestone facies.

The limestone member is made up of a lower bedded reef-flank deposit and upper biohermal mass. This member is characterized by by localthickening and thinning over a fairly continuous belt. The lower bedded portion is dominantly calcareous rock detrita and fine slime with interbedded, finely siliceous layers. The biohermal portion is white to buff, occasionally gray to pink, cavernous and partly crystalline, consisting essentially of skeletal remains of reef-building organisms (corals and Algae) with abundant molluscan fragments and bryozoan stems. Along Madlum River, the biohermal potion is approximately 100 m thick.

Recent age dating reported by Rigenbach (1992) conforms to the result obtained by Gonzales and others (1971) and Baumann and others (1976) indicating to late Early to early Middle Miocene age. Moreover, a sample from Minalungao yielded Lepidocyclina (Nephrolepida) sumarensis and many Miogypsina sp., which point to a Late Burdigalian age. Likewise, feragic foraminifera from the pelites in the clastic member take along Rio Chico gave a precise Late Burdigalian age base on Globigerinatella insueta. Villanueva and others (1995) also report the presence of Globigerinoides sicanus De stefani in the clastic facies as well as nannofossils including Heterosphaera mediterranea and Sphenolithus cf. heteromorphous, which indicate an age of NN4-NN5, probably NN4 equivalent to Early Miocene (BBurdigalian). Recent studies by Villnueva and others (1995) also indicate an Early Miocene age for the liestone based on the presence of Cycloclypeus (K.) transiens. Abundant large foraminifera, corals, algae and molluscan remains in the limetone and carboneous materials in the clastic facies indicate deposition in a shallow neritic environment.

Madlu Formation
Lithology	Lower clastic membe - sansdstone, shale conglomerate Middle Alagao Volcannics - pyroclastic breccia, tuff, argillite indurated graywacke and andesite flow, Upper Buenacop Limestone Member
Stratigraphic relations	Conformable over the Angat Formation
Distribuition	Madlum River, San Miguel, Bulacan, Angat and Penaranda rivers, Bulacan, San Ildefonso, Bulacan
Age	Middle Miocene
Thickness	> 1,000 m
Named by	Williams (1960)
Synonymy	Sibul Formation (Corby and others (1951)

The Madlum Formation conformably rests on top of the Angat Formation. This was first used by geologists of the San Jose Oil Company (Williams, 1960 in Gonzales and others, 1971) to designate the sequence of shale, siltstone, wacke and conglomerate exposed along Madlum River close to Barangay Madlum, San Miguel, Bulacan. They also includedin this formation the upper metavolcanic member of the Sibul Formation and upper tuffaceous member of the Quezon Formation of Corby and others (1951) exposed in the Angat River area. Melendres and Verzosa (1960) subdivided the Madlum into the Angat River Limestone, Alagao Volcanics and BUenacop Limestone members. The middle and upper members were retained by Gonzales and others (1971) but changed the Angat River Limestone to Clastic Member.

· Clastic Member

The Clastic Member is extensively distributed n an almost continuously exposed belt between Angat and Penaranda rivers. It is a thick sequence of thin to thick bedded sandstone and silty shale with minor basal conglomerate and occasional limy sandstone interbeds. The sandstone is fine - to medium - grained, fairly well - sorted, well - cemented and calcareous, with sub angular to subrounded fragments of mafic rock detrite, quartz and feldspar cemented by fine clayey material.The shale which occurs in thinner beds compared to the sandstone, is calcareous. The basal conglomerate is massive is well rounded cobbles and pebbles of mfic igneous rocks, chert and limestone disperesed in a coarse calcareous matrix.

Two foraminiferal zones have been recognized in the Clastic Member by Villanueva and others (1995):Globoratallia fohsi peripheroronda Zone (N6-N10) and Globoratalia fohsi fohsi Zone (N10-N11) equivalent to Langhian, which were earlier reported by Gonzales and others (1971).

· Alagao Volcanics

Melendres and Versoza(1960) used the term Alagao Volcanics to deignate the sequence of pyroclastic breccia, tuffs, argillites, indurated and graywacke and andesite flows exposed in Alagao, Sna Ildefonso, Bulacan. Its type locality, as designated by gonzales and others (1971), is the section along the San Ildefonso-Akle road. The metavolcanic member of the Sibul Formation of Corby and others (1951) and the andesite basalt sequence in the Rodriguez-Teresa area, Rizal, are included in this member. Generally, the rock unit is purplish gray in fresh surfaces but weathers into brick-red. to purple shades. The pyroclastic breccia, the prevalent rock type, is massive and made up of angular to subrounded cobble to boulder sizes of andesite, basalt, chert and other volcanic rocks set in a matrix of andesite. The tuffaceous beds weather into bentonitic clay. The volcanic flows are massive, fine-grained an vesicular. The vesicles are filled with calcite, chalcedony or chlorite.Along Bayabas River, the estimated thickness is about 175 m, although it could be thicker along Angat River further south.

· Buenacop Limestone

The Buenacop Limestone was originally used by Melendres and Verzosa (1960) to deignate the Limestone sequence exposed at Barangay Buenacop, San Ildefonso, Bulacan with type section along Ganlang River. It also occurs as narrow discontinuous strips formed by a series of almost north-south aligned low ridges and several small patches between Sta Maria and Sumacbao rivers. The limestone in the lower part is thin to medium bedded, crystalline, slightly tuffaceous, porous with numerous fragments of volcanic rocks, chert nodules, and detrital crystals of mafic minerals. This characteristics distiguishes it from the other limestones in the area. The upper part is massive, cavernous, with dispersed occasional andesite fragments, volcanic debris and fossils of reef-building organisms such a corals, algae, mollusk and foraminifera. Fossils indicate an age of MIddle Miocene for this limestone member, which was probably deposited in ashelf area. The estimated thickness at the type locality is 150 m.

Samples of the Buenacop Limestone yielded a number of foraminifera, including Miogypsina polymorpha, Cycloclypeus (Metacycloclypeus) transiens, Lepidocyclina (N.) sumatrenesis and L. (N.) sumatrensis and L. (N.) ferreroi. Thus an age deposition could have started in early Middle Miocene. Deposition might have taken plac in a progresively deepening environment probably from shlef-edge to upper bathyal depths. It is over 1,000 m thick in the type locality.

Guadalupe Formation
Lithology	Alat Conglomerate - conglomerate, silty mudstone, tuffaceous sandstone Dilima Tuff -vitric tuff, igninbrite, volcanic breccia
Stratigraphic relations	Unconformable over Miocene rocks
Distribution	Quezon City, Pasig, Makati; southern Rizal;eastern Bulacan; southeastern Nueva Ecija
Age	Pleistocene
Thickness	1,500 - 2,000 m
Named by	Smith (1913)
Correlation	Laguna Formation (Schoell and others, 1985),San Juan Formation (Rutland, 1968)

This formation was named by Smith (1913) for the tuff sequence that crops out along Pasig River in Guadalupe, Makati Metro Manila , which was earlier described by Von Drasche (1878). In the Angat-Novaliches region, Alvir (1929) describes the same sequence but referred to it as Guadalupe Tuff Formation. Corby and others (1951) call it Guadalupe Tuffs and Teves and Gonzales (1950) adopt the name Guadalupe Formation with two members: a lower Alat Conglomerate and an Upper Diliman Tuff member. The formation unconformably overlies Miocene rocks and on the basis of the presence of Stegodon fossils and other vertebrate remains leaf imprints and artifacts, it is assigned a Pleistocene age.

· Alat Conglomerate

The Alat Conglomerate was firs mapped and named by Alvir (1929) after the marine littoral conglomerate exposed along Sapang Alat about 3 km north of the Novaliches reservoir near Novaliches town where it unconformably overlie Miocene lavas. The Alat consist of massive conglomerate, deeply weathered silty mudstone and tuffaceous sandstone. Poorly sorted conglomerate, which is the most predominant rock type, consist of well rounded pebbles and small boulders of older rocks, including diorte, gabbro, basalt, andesite and limestone cemented by coarse-grained, calcareous sandy matrix. The interbeddd sandstone is massive to poorly bedded, tuffaceous, fine to medium - gained, loosely cemented, friable and exhibits cross bedding. The mudstone is medium to thin bedded, soft,silty and tuffaceous. The maximum estimated thickness of this member is 200 m. Rigenbach (1992) notes that the San Juan Formation of Rutland (1968), exposed southeast of Laur, is very similar in facies to the Alat Conglomerate.

· Diliman Tuff

The Diliman Tuff (Teves and Gonzales, 1950) exposed in Diliman, Quezon City and large portions of Makati Pasig, Paranaque and adjoining areas, consist of volcanic ejecta with suibordinate amounts of tuffaceous, fine to medium grained sandstone. It also underlies areas between Sta. Maria and Bulu rivers in Bulacan. Fossil plant leaves of the genus Euphorbliaceae, deer and elephant teeth, and bits of wood recovered in Guadalupe and Novaliches suggest a Pleistocene age.

The whole sequence is flat - lying, medium to thin - bedded and consists of fine-grained vitric tuff and welded pyroclastic breccias with minor fine to medium-grained tuffaceous sandstones. Dark mafic minerals and bits of pumiceous and soriaceous materials are dispersed in the glassy tuff matrix. The thickness of the Diliman Tuff is 1,300 - 2,000 m.

More recnt work in the area suggests that the Laguna Formation of Schoell and others (1985) is equivalent to the Guadalupe Formation. Schoell and others (1985) defined several facies of the Laguna Formation, as follows: a) air fall tephra, b) pyroclastic flow deposits, c) lahars, d) stream deposits, e) lake deposits, and f) basalt flow. Radiometric K-Ar and palynological datings give a LAte Pliocene to Early Pleitocene age for this formation (Wolfe, 1981).

Antiopolo Basalt
Lithology	Basalt
Stratigraphic relations	Not reported
Distribution	Antipolo, Binangonan, Talim Island, Taytay,Morong in Rizal
Age	Pleistocene
Named by	Alvir (1928)

The Antipolo Basalt was named by Alvir (1928) for the basaltic rocks exposed on the hills arounf Antipolo, although the rock was already exposed earlier by Adams (1910). The rock is also exposed in surrounding areas such as Binangonan, Morong Angat-Novaliches area and Talim Island. The basalt is frequently brecciated and in places amygdaloidal. The age is believed by Alvir (1928) to be Miocene, although it could be as late as Pleistocene in view of the very lowdegree of erosion despite its location on an elevated plateau in the Antipolo hills. Remnants of the wasting of the basalt terrain are manifested as scattered cloumn of basalt in Antipolo and vicinity, suggesting that the basalt was deposited as thick lava flows that underwent columnar jointing.

Manila Formation
Lithology	Clay, silt, gravely sand, tuffaceous silt
Stratigraphic relations	Overlies the Diliman Tuff
Distribution	Metro Manila
Age	Holocene
Thickness	800 m
Named by	Purser and Dlomampo (1995)

Overlying the Diliman Tuff is a sequence of unconsolidated fluvial, deltaic and marine deposits to which Purser and Diomampo (1995) proposed the name Manila Formation. The sequence is believed to have been laid down during Holocene time. Subsurface data from core drilling along the Light Rail Transit 2 (LRT 2)) route from Santolan, Pasig to Recto, Manila indicate a thickness of about 800 m. The unconsolidated deposits consist of clay, silt, gravelly sand and tuffaceous silt.

Geology of the Region: Region IV-A