Today is

 

 

MICROFACIES TYPES OF THE BINANGONAN FORMATION
ANTIPOLO-TERESA, RIZAL PROVINCE

Joseph M. Foronda & Walter U. Schoell

 

 

 

ABSTRACT



The Binangonan Formation consists of carbonate deposits extending from Upper Oligocene to Lower Miocene. ln the Antipolo-Teresa area, shallow-water turbidites (allodapic limestones) comprising the Teresa Tuffaceous Siltstone (lower member) gave way to deposits of shallow-water reef complexes comprising the limestone member (upper member).

Sedimentological criteria indicate that deposits of the Teresa Tuffaceous Siltstone represent shallow water proximal turbidites. Microfacies types recognized in these turbidites include lithoclastic-bioclastic packstones / grainstones, hemipelagic wackestones/mudstones, and minor rudstones.

The shallow water turbidites served as a carbonate platform upon which reef buildup and deposition of reef-associated carbonate facies commenced. Generally four facies can
be distinguished: (a) basin margin, (b) foreslope, (c) main organic reefs, and (e) open
marine lagoon.

The basin margin facies is composed microbioclastic-calcisiltites, bioclastic packstones, mudstones/marIs, and minor hemipelagic wackstones. This paleoenvironment was
characterized by limited light and scarcity of grain-producing organisms with predominance
of planktonic forms. lnitially, a high rate of up-building of reefs in local areas caused formation of restricted basins and subsequent deposition of reddish nodular limestones. The nodules were derived by in situ brecciation without reworking.

The foreslopes facies is characteized by floatstones, bioclastic packstones, minor microbioclastic calcisiltites and boundstones. Association of limestone types in this facies might suggest that the foreslope had a generally gentle inclination. Interbedded with these deposits occur fining upwards cycles composed of coral floatstones, foraminiferal packstones/ wackestones, and mudstones which are interpreted as storm deposits (tempestites).

The main organic buildups are comprised of boundstones, and minor bioclastic packstones/ grainstones. The distribution of the microfacies types in the reef complex might indicate that these reefs were discontinuous giving way to extensive interreef areas.

 

 

 

Geological Society of the Philippines

Unit 250, 2nd Floor, Cityland Pioneer, 128 Pioneer Street, Mandaluyong City, Philippines

Tel: +(63-2) 633-9025