Saturday, March 20, 2010

The Last Tribes of Mindanao

The Last Tribes of Mindanao, The Tausug, People of the Current.

Tausug orSuluk is the name of an Islamized tribal group in the Sulu archipelago, and is taken from the words tau meaning man and sug meaning current.

Traditionally the Tausug are sailors, pearl divers and traders, their ancestral homelands in the Sulu Archipelago have vigorous tidal currents that flow from the Sulu and China Seas to the Celebes Sea. This translates literally into the name people of the current.

This native tribe, the first group in the archipelago to be converted to Islam, possess a courage that is beyond doubt, their bravery is supposed to be unquestionable, therefore the Tausug are often namedTau Maisug or brave people. They are proud Muslims renowned for their fierce resistance in the face of Spanish Conquerors, for 300 years the Tausug and the Spanish were engaged in almost continuous warfare, which ended when the Spaniards left thePhilippines. The Tausug regards themselves superior to other Philippine Muslims and still live a combative way of life, running away from a fight is considered shameful. One old Tausug proverb says: Hanggang maybuhay, may pag asa, meaning; Never admit defeat as long as you live.

The Last Tribes of Mindanao, The Tausug.
The Last Tribes of Mindanao, The Tausug.
This homogeneous tribe is a blend of Malay and Indonesian races; they are widespread in the Philippinesand can be found mainly in coastal area communities. They are distinctive from the Badjao Tribe by the aspects of their own culture and because they speak their own language. In the past the Tausug were boisterous pirates who infested the waters from the Sulu seas but nowadays make a living from agriculture, raising water buffaloes and fishing. Aside from being known as the best, gallant and ferocious freedom fighters of the world the Tausug are famous for being the best pearl divers in the world. Fishing is done in off-shore waters from motorized boats using bamboo traps, hook and line and fishing nets.

The strong-willed Tausug follow the Sunni Islamic beliefs and practices, Sunni Islam is the largest branch of Islam, the word Sunni comes from the word Sunnah meaning tradition. But indigenous beliefs endure, apart from Allah or Tuhan, the Tausug also believe in spirits that inhabit nature, especially rocks and trees, like the evil spirits namedsaytan and unseen creatures called jinn. According to the Tausug the human soul has four souls which leave the body when he dies, the life-soul related with blood, the spirit-soul connected with dreams, the soul of breath, associated with life and the transcendental soul. The body of the deceased will go to hell, to receive punishment for the sins committed while he was living. Various charms and belief in spirits, in order to gain success and good fortune, are still a great part of their daily life.

Tausug folk stories tell of great ancestors and legends, a favourite legend is the Kaawn of Bud Tumantangis, Mount Tumantangis, the highest peak in the province is called as such because, when sailing away, sailors cry when they lose sight of this landmarks and when they return, upon seeing again its silhouette from far away. The name Tumantangis comes from the word tangis, which means to cry, and bud meaning mountain, known to locals as the weeping mountain. The beautiful tomb of Sharif Abu Bakr, the founder of the Sulu Sultanate still exists on one of the slopes of Mount Tumantangis. The believes of the Tausug can be seen in their rituals and dances, many of them reflecting nature, such as the ebb and flow of the waves of the ocean, referring to their travels at sea.

The Pangalay, a traditional Tausug wedding dance and popularly known as the fingernail dance is one of the most well known dances, accompanied by a kulintang ensemble. This dance is distinctive because dancers use metal or golden nail extenders or janggay, which make the fingers stiff and set them apart from the thumbs. The Pangalay imitates the mythical Sarimanok bird, a reincarnation of a goddess who loved a mortal man, after the dance, she removes her nails and drops them to the ground, hoping that a man will gather them and will claim her for his bride. A Tausug marriage is usually arranged by parents, with the exception of the children of brothers, first and second cousins are favoured spouses. Marriageable women are kept in relative seclusion to protect their value to their family.

The Last Tribes of Mindanao, The Tausug.
The Last Tribes of Mindanao, The Tausug.
The Tausug tribe is one of the Muslim minorities in the Southern Philippines; they still retain many of the ancient practices and strong, dynamic traditions of their particular tribal heritages but are experiencing a great deal of change. The traditional Tausug culture is diminishing because of the influences of the modern Philippine society. Many of the Tausug are living below poverty level and have been displaced from their homes and livelihoods by the wars and armed conflicts between rebel groups and the Philippine government.

The Tausug, a rough tribe that roamed the Southern Seas and resisted foreign intruders at land is at present caught, in the middle of nowhere.

Sulu Sea Basin


Ricardo G. Poblete, Jr. and Arturo A. Morado, Jr.
COMEXCO, Incorporated


The NW Sulu Sea Basin is probably the most attractive frontier area for exploration in the Philippines. It is located within the continental North Palawan Block (NPB), a rifted fragment of the Asian mainland. The Northwest Palawan Area (NWPA), the only petroleum-producing province in the Philippines, is also located within the NPB and to the northwest of the NW Sulu Sea Basin. Previous work and our own recent study suggest that the NW Sulu Sea Basin could contain a petroleum system that is analogous to that of the NWPA.

Numerous large to giant-sized leads, representing the four (4) major play types that are identified in the basin, are presented. The major play types are:

  1. anticlines with four-way dips;
  2. Early Miocene carbonates;
  3. Middle Miocene carbonates; and,
  4. Miocene turbidites.

Geological conditions in the relatively unexplored NW Sulu Sea Basin present possibilities for major oil and/or gas accumulations. The similar distance to the market in Luzon of the NW Sulu Sea Basin and the giant Camago-Malampaya Gas Field, currently under development by Shell (gas-to-power) in the deep waters of NWPA, implies that even a gas accumulation from the giant leads in the NW Sulu Sea Basin can be a viable economic venture. The variety of the types of leads in both shallow and deep waters in the area present the explorers with medium risk-high reward to high risk-high reward exploration opportunities.

1. Introduction

The NW Sulu Sea Basin is part of the greater NW Sulu Sea area that includes the Cuyo Platform and the Cagayan Ridge (Figure 1). The sharp change in the bathymetry near the latitude of 10o30’ North is considered the geographic boundary between the Cuyo Platform and the NW Sulu Sea Basin. The Cuyo Platform is in shallow waters (<200>

Our studies of the NW Sulu Sea Basin in the last three years has led to the following findings that:

  1. There are indications that the hydrocarbon play concept that proved successful in the NWPA might also be present in the NW Sulu Sea Basin;

  2. It contains a variety of untested plays with several giant leads, and;

  3. The area offers an opportunity for both a relatively medium risk-high reward to high risk-high reward exploration venture.

A significant portion of the NW Sulu Sea Basin and the Cuyo Platform is currently under license or under an exclusive Geophysical Survey and Exploration Contract (GSEC) application by South China Resources, Inc. with the Philippine Department of Energy (cf. Fig. 1).

2. Exploration History

The table below summarizes the highlights of past and present exploration in the NW Sulu Sea Basin and adjoining areas:

Table 1: Geochronological Summary of Past Exploration






Aeromagnetic Survey – Project MAGNET

U.S. Naval Oceanographic Office; Philippine Bureau of Mines and Bundesanstalt fuer Bodenforschung (Bfb) of Germany

Scientific Research


Seismic Acquisition

Phil. Overseas Drilling

Petroleum Exploration


Seismic Acquisition

Philex Mining Corp.

Petroleum Exploration


Seismic Acquisition

Baguio Gold Mining

Petroleum Exploration


Sesimic Acquisition

Oriental Petroleum

Petroleum Exploration


Seismic Acquisition

Mobil Oil (US)

Petroleum Exploration


Seismic Acquisition

Oceanic Minerals (US)

Petroleum Exploration


Seismic Acquisition

Brascan Resources (US)

Petroleum Exploration


Seismic Acquisition

MultiNatural Resources

Petroleum Exploration


Seismic, Gravity and Magnetic Acquisition; Ocean Drilling Program

German Federal Institute for Geosciences and Natural Resources (BGR)

Scientific Research


Seismic Acquisition

Cities Service (US)

Petroleum Exploration


Seismic Acquisition

Phillips Petroleum (US)

Petroleum Exploration


Exploratory Drilling – Roxas-1; Dumaran-1 & Paly-1: all dry holes, except Dumaran-1

Cities Service (US)

Petroleum Exploration


Seismic Acquisition & Field Geology

Seafront Petroleum

Petroleum Exploration in the Cuyo Platform


Seismic Acquisition & Field Geology

Phil. Oil & Geothermal Energy (POGEI) & Lepanto Mining

Petroleum Exploration in the Cuyo Platform


Comprehensive Basin Evaluation Studies

World Bank-funded: Phil. Bureau of Energy Dev’t, Robertson Research & Flower, Doery and Associates.

Petroleum Exploration


Geological Field Studies

in Central Palawan

UNDP-Phil. Bureau of Mines

Mineral Resources Evaluation


Seismic, Gravity, Magnetic & Geochemical Data Acquisition; Seismic Reprocessing; Basin Evaluation Studies

Australian Geological Survey Organization (AGSO) & Phil Dept. of Energy

Petroleum Exploration


Data Re-Interpretation & Basin Evaluation

South China Resources & COMEXCO, Inc.

Petroleum Exploration


Seismic Reprocessing; Aerogravity and Magnetic Acquisition; Seismic Acquisition

Murphy Oil (US) & South China Resources

Petroleum Exploration in the Cuyo Platform

3. Geological Background

3.1 Tectonic Setting and Present Structure

The NW Sulu Sea Basin, together with the Cagayan Ridge to the east and the Cuyo Platform to the north, is located within the continental NPB (Figure 2 ). The continental basin is bounded to the west by the uplifted North Borneo-Palawan ophiolite province and to the east-southeast by the oceanic SE Sulu Sea Basin and the Sulu-Negros Trench. A submerged portion of the ophiolite province presently underlies the northwestern margin of the NW Sulu Sea Basin shelfal area.

The Cagayan Ridge is a southeast-facing continental volcanic arc of ?Oligocene-Miocene age. It is a partly submerged magmatic arc that separates the continental basin of NW Sulu Sea from the oceanic SE Sulu Sea basin (Figure 3). The petrology (Kudrass et al., 1990 in Hinz et al., 1991) and geochemistry (Spadea et al., 1991 in Hinz et al., 1991) of samples collected from drillsite 771 during the Ocean Drilling Program (ODP) Leg 124 indicate that continental basement underlies the volcanic rocks of Cagayan Ridge (Rangin, 1991). A series of northeast-trending rift half-grabens have also been recognized on seismic below the thick volcanic units (Hinz et. al., 1991). These half-grabens are probably equivalent to those observed in the NWPA and other areas within the NPB.

The uplifted North Borneo-Palawan ophiolite province is a remnant of the Early to Middle Cretaceous oceanic Proto-South China Sea (PSCS) (cf. Fig. 2 ). The PSCS was modeled by Morado and Poblete (1997a) to have progressively thrusted over a portion of the NPB as a result of the nearly coeval opening of the present South China Sea to the north-northwest and the SE Sulu Sea to the southeast (Figure 4a-4d).

Northeast-trending Paleogene extensional features, similar to those in the Northwest Palawan Area (NWPA) and Cuyo Platform, exist in the NW Sulu Sea Basin (Figure 5). The north to northeast-trending en echelon folds, which are very prominent in the deep water portion of the basin, were probably inverted grabens that resulted from compressive or transpressive movement episodes during the Early to Middle Miocene (cf. Fig. 4c and 4d). Some possible igneous extrusions are observed on seismic and these appear to be localized and suspected to have emanated along the margins of the rift faults. An analogous occurrence of volcanic extrusives in the hydrocarbon-producing NWPA was encountered in the Boayan-1 well (cf. Fig. 5).

3.2 Stratigraphic Summary

The stratigraphic development in the basin can be can be segregated into four major stratigraphic sequences: pre-rift, syn-rift, drift-sag and post-drift (Figure 6 ).

The NW Sulu Sea Basin, like the Cuyo Platform and NWPA, is interpreted to be underlain by a thick pre-rift sequence of highly deformed autochthonous Paleozoic to Mesozoic metamorphic and sedimentary materials derived from a continental source similar to the outcrops in north Palawan and the Calamianes Island group. These outcrops reveal similarities with chronostratigraphic lithologies presently found in southern China (Hashimoto and Sato, 1973; Fontaine, 1979; Fontaine et al., 1985; BED, 1986).

The rift phase within the southeastern Eurasian margin, including the NPB, occurred from the close of Cretaceous to Early Oligocene (cf. Fig. 4a and 4b). The rifting event, which led to the development of large horst and grabens, corresponds to the latest phase of the Yenshanian orogeny as recorded on mainland China (Holloway, 1982).

The syn-rift sequence in the NW Sulu Sea Basin is possibly deposited in a shallow marine to marginal marine environment of deposition similar to that of the NWPA as described by Benavidez et. al., (1995). A lacustrine environment could also be present within the basin. Lacustrine sediments were encountered in the Maniguin area (Del Pilar, 1997) on the northeast portion of the NPB. In the PSCS basin (cf. Fig. 4a and 4b), deposits were mainly deep water turbidites of Eocene age (UNDP, 1985) which are represented on outcrops by the widespread Crocker Formation. It has been suspected that sometime in the Early and Middle Oligocene, portions of the eastern margin of the PSCS basin were affected by compressive movements caused by the initiation of spreading in the SE Sulu Sea (cf. Fig. 4a and 4b).

Past workers referred to the syn-rift sequence of the NPB as the pre-Nido Tertiary Formation (Sali and Oesterle, 1981; Phillips Petroleum, 1983). The Lower Paleogene syn-rift sequence is generally absent in the NWPA. The Upper Paleogene, however, is represented by an Upper Eocene trangressive sandstone overlain by an Upper Eocene to Lower Oligocene carbonate platform (Beddoes, 1980 and Hatley, 1980 in Holloway, 1982). In the east Palawan area, shallow marine undifferentiated Eocene limestones are reported to outcrop in a few islands/islets north of Dumaran Island, e.g. Pabellion, Apulit and southeastern Maytiguid Islands (David and Fontaine, 1985). These carbonates could be equivalent to the transgressive Late Eocene Lepitan Limestone in onshore SW Mindoro (Sarewitz and Karig, 1986) on the northeastern extremities of the NPB, where it has been reported to drape over the thick syn-rift sequences. Seismic data in the western part of the Cuyo Platform suggest the presence of at least 2,500 meters of syn-rift sequences in some of the half-grabens.

The recent seismic mapping show that very thick Paleogene syn-rift sequences underlie the NW Sulu Sea Basin. The Lower and Upper Paleogene sequences appear to be separated by a local unconformity of possible Early Eocene age. This deposition break is well-recognized on seismic in the deep water part of the basin. The anticipated syn-rift sequences were probably deposited in a lacustrine to possibly shallow marine environment. It was noted that in the NWPA, some of the oil discovered is sourced from syn-rift deposits (Branson et al., 1997).

The mid-Oligocene Unconformity marked the transition from rift to drift. From Late Oligocene to Middle Miocene, the South China Sea opened (cf. Fig. 4c and 4d) resulting in the southward drift of the NPB to its current position (Taylor and Hayes, 1983). Crustal sagging accompanied this drifting episode. Contemporaneous oceanic spreading in the SE Sulu Sea resulted in compressional folding and local uplifts along the eastern margin of the PSCS basin. This was probably partly compensated by the continued subduction of the southern half of the oceanic crust beneath the Sulu-Negros Trench (Morado and Poblete, 1997a).

The drift-sag sequence is composed of variable deposits of Upper Oligocene to Middle Miocene age. These deposits range from non-marine to lacustrine clastics and shallow to deep open marine carbonates and clastics. Included within this sequence are the Nido Limestone Formation (or its onshore equivalent in Palawan Island, the St. Paul’s limestone) and the Pag-asa Formation, which includes the Galoc Clastics and the Batas Conglomerate.

In the NW Sulu Sea Basin, the drift-sag sediments are anticipated to be generally shallow marine carbonates to transitional marine on the shelf and fault block crests and deep marine on the basin lows, similar to the NWPA. In the Maniguin-2 well, on the northeastern part of the NPB (cf. Fig. 5), the drift-sag sediments are non-marine to lacustrine (Del Pilar, 1997; Morado, 1997). To the northwest of this well towards southwest Mindoro Island, the drift-sag sediments become transitional to deeper marine (BED, 1986). The drift-sag sediments contain the main proven source rocks, reservoirs and seals in the petroleum system of NWPA. In the Maniguin-2 oil discovery, the source, reservoir and seal are within the drift-sag sequence (Del Pilar, 1997).

The Middle Miocene Unconformity, which records the initial collision of the NPB with the Philippine Mobile Belt (PMB), separates the drift-sag sequence and the post-drift sequence

The dominant structural deformation in the NPB during the post-drift phase was compressional resulting in uplift and folding. There was also transpressional reactivation of old rift faults (Branson, et. al., 1997) which resulted in inverted structures. Some of the traps formed during this period are productive in the NWPA (e.g. W. Linapacan, Linapacan A and B).

The post-drift sequence is characterized by the presence of thick coarse clastics, mostly conglomerates, due to uplifts related to compressional and transpressional episodes brought about by continuous collision of the NPB with the Philippine Mobile Belt (PMB). These sediments belong to the Matinloc Formation. In the NWPA, Branson, et. al. (1997) noted that in some parts, uplift was in excess of 1,000 meters. The post-drift phase was followed by the deposition of Plio-Pleistocene biocalcarenites, marls and argillaceous limestones that composed the Carcar Formation.

4. Petroleum System

The tectonic model proposed by Morado and Poblete (1997b) for the continental NPB is the foundation by which the petroleum potential of the NW Sulu Sea Basin has been evaluated. It is our belief that a potential petroleum system, very similar to the one that proved successful in the NWPA, exists in the NW Sulu Sea Basin (Figure 7). In particular, rift fault systems analogous to those that control the petroleum system in the NWPA (cf. Fig. 5) are present in the NW Sulu Sea Basin.

4.1 Source Rocks

None of the three wells in the area (cf. Fig. 2 and Fig. 5) penetrated any potential source rock (BED, 1986). However, the existence of possible source rocks is imlpied by the presence of relatively good gas shows (C1-C4) and dead oil traces in a 1,100 meter thick interval of non-reservoir conglomerates in the Dumaran-1 well drilled by Cities Service in 1980. It is speculated that the hydrocarbons found in this well must have migrated up dip from a source deeper in the basin (Fraser and Guazon, 1995).

Potential hydrocarbon kitchen areas in the basin are large Paleogene grabens with thick syn-rift sediments attaining a thickness in excess of 5,000 meters and overlain by drift-sag sediments of up to 3,000 meters thick (cf. Fig. 6). Syn-rift lacustrine to marginal and shallow marine sediments and drift-sag deep water carbonates and shales, very similar to those in the NWPA are the anticipated source rocks. An older source, possibly Cretaceous in age and possibly similar to the one proposed by Durkee (1992) for the western Palawan shelf, might also be present in the basin.

4.2 Thermal Maturation

Thermal maturation of the sediments in the basin was determined using the Lopatin method (Waples, 1980). Random points along selected seismic dip-lines in the basin were chosen for thermal maturity modeling. Some of these models are presented here (Figures 8a to 8d).

A geothermal gradient factor of 3.92oC/100m (2.15oF/100ft), which is the average of two nearby ‘continental’ wells, Paly-1 and Maniguin A-1X, and ambient surface temperature of 24oC were utilized in the burial history modeling. This geothermal gradient factor is comparatively higher than the prevailing average of 3.6oC/100m in the petroleum-producing NWPA. Moreover, it is apparently higher than those in other rift-sag basins, e.g. the Damintun Depression in North China (3.4oC/100m, according to Xiao & Zuan, 1991).

The mature sediment thicknesses and computed TTI values obtained from the Lopatin models were plotted on the map and contoured for visual interpretation and presentation (Figure 9). The distribution plots appear to correlate well with the predominant north-northeast structuring in the basin (cf. Fig. 5).

From the burial history charts (cf. Fig. 8), the onset of hydrocarbon generation at the base of the syn-rift sediments occurred as early as Late Eocene to Early Oligocene. Thick intervals of the potential syn-rift and drift-sag source rocks contained in the kitchen areas are presently still within the hydrocarbon-generating window.

It was noted from the various thermal maturity profiles across the deep water part of the basin that much of the drift-sag potential marine source rocks are still within the oil generating window stage (between TTI 15 and 160). Some of the syn-rift source are in the gas generating stage. The average top of the oil window in the deep water portion of the basin is approximately 3,500 meters while the average top of the gas window lies at around 4,500 meters.

Up to 5,500 meters thick of thermally mature sediments were determined from the plots of the thermal maturity profiles using time-temperature indices. Two major north-northeast trending belts of potential kitchen areas, measuring approximately 40 kilometers by 80 kilometers (3,200 square kilometers) each, contain at least 3,500 meters of thermally mature sediments (cf. Fig. 9). These potential kitchen areas correspond to the two parallel major grabens in the basin. The areas of these kitchens are considered very large and could supply the necessary volumes for major accumulations in the basin. In comparison, the size of the Malampaya Graben kitchen of NWPA, which is the source for most of the hydrocarbons accumulations in that basin, is approximately 3,000 square kilometers. It is therefore considered that, indeed, the NW Sulu Sea Basin is a very attractive frontier area for exploration.

4.3 Hydrocarbon Migration

Hydrocarbon migration from the source to the trap is anticipated to be via numerous fault and fractures systems and permeable beds present in various stratigraphic levels (cf.Fig. 7). Timing of trap formation is not considered critical in the basin since hydrocarbon generation from potential source rocks continued up to the present day (cf. Fig. 9).

A study by Todd, et. al. (1997) suggests that typical major petroleum provinces in Southeast Asia are characterized by a close association of oil and gas pools to within 20 kilometers of the source kitchen and that outside of this "halo" of accumulations, valid traps tend to be severely underfilled or dry. Most, if not all, of the leads that have been identified in the NW Sulu Sea Basin are within 20 kilometers of the potential source kitchen.

4.4 Reservoir Rocks

The potential reservoir sections in the basin are present in the pre-rift, syn-rift and drift-sag sediments (cf. Fig. 6 and Fig. 7). The pre-rift reservoirs include the Cretaceous sandstones equivalent to those gas-bearing sandstones encountered by the Sampaguita wells in the Reed Bank west of the NWPA and pre-Tertiary fractured basement rocks or carbonates similar to those that are hydrocarbon-bearing in southern Vietnam, North China (Zhai and Zha, 1981; Xiao Guan and Zuan, 1991) and Bohai Gulf (Li, 1986).

The syn-rift reservoirs are probably non-marine to shallow marine sandstones and shallow water carbonates. At the San Martin-1 gas discovery well in the NWPA, the shallow marine Eocene sandstones have porosities up to 21% (BED, 1986). While in the Reed Bank area, west of NWPA, the Sampaguita wells tested substantial amounts of gas from non-marine to transitional Paleocene-Eocene sandstones (BED, 1986). The Late Eocene rocks onshore Mindoro Island have porosities ranging from 7% to 20% with measured permeabilities up to 225 mD (Benavidez, et. al., 1995).

Potential drift-sag reservoirs are very similar to those that produce hydrocarbons in the NWPA (cf. Fig. 7). These reservoirs include shallow water carbonate buildups (Nido Limestone) on highs analogous to the Camago-Malampaya, Nido, Cadlao and Matinloc fields and turbidite sandstones in the lows, similar to the oil-bearing turbidite sandstones at the Galoc and Octon discoveries in the NWPA.

Several possible turbidite canyons have been identified on seismic along the present western margin of the NW Sulu Sea Basin and these could have been the pathways of the turbidites to the basin floor currently located in the present day deep water portion of the basin.

4.5 Seal

The regional top seal of the basin is anticipated to be the drift-sag Early to Middle Miocene fine-grained sequence (cf. Fig. 6 and Fig. 7) that is thick and widespread in the NPB. This sequence is equivalent to the deep water Pag-asa claystone of the NWPA. Local top seals would be provided by intra-formational claystones associated with transitional to shallow water sequences in the syn-rift sediments.

4.6 Trap Formation

The potential traps present were formed mostly during the syn-rift and the drift-sag phases although additional potential traps were formed during the post-drift/collision phase. The timing of trap formation is not considered a problem in this basin since, as mentioned earlier, hydrocarbon generation from potential source rocks continued up to the present day (cf. Fig. 9).

5. Play Types

There are four major petroleum plays (Types A to D) in the basin (cf. Fig. 7): They are:

  1. anticlines with four-way dip closures stacked with Mesozoic to Early Miocene reservoirs (Type A);
  1. Early Miocene reefs (Types B1 & B2);
  1. Middle Miocene reefs (Types C1 & C2), and;
  1. Miocene turbidites (Type D).

Numerous leads, representing the four aforementioned plays, have been seismically identified in the NW Sulu Sea Basin. The locations of these leads are indicated in Figure 10. Note that most of the leads are near the potential source kitchens as previously discussed.

Type A: Anticlines with Four Way Dip Closure

Anticlines with four-way dip closures are the most impressive plays in the basin. These are situated in the present-day deep water portion (>200m subsea). These anticlinal leads were seismically defined on the Top Early Miocene level. These large anticlines are products of transpressional and/or compressional folding during the drift-sag phase (Morado and Poblete, 1997b). The folding created inverted grabens placing both source and reservoirs within the four-way dip closures. These are analogous to the productive structures described by Eubank and Makki (1981) in the Central Sumatra Basin.

Examples of this play are shown in Figure 11a-c. The areal extent of these four way dip closures range between just below 50 to over 600 square kilometers. These closures are indeed giant sizes and they attest to the exciting potential of the basin. Please note also that in the crests of some of these anticlines, possible Middle Miocene carbonate buildup exists (cf . Fig. 11a and 11c), providing for additional targets in this play.

Type B: Early Miocene Carbonate Buildup

Early Miocene carbonate buildup plays (cf. Fig. 7) were developed during the drift-sag phase in the basin. The more dominant carbonate play in the basin is represented by Early Miocene reefs which are equivalent to the main productive trapping mechanism in the NWPA (e.g. Camago-Malampaya, Nido, Cadlao, Matinloc and San Martin). Most of them grew on the original rift highs and near potential mature source rocks that are related to rift grabens. Some of the reefs apparently built up along "shelf breaks", hence, lying directly updip from potential mature source rocks (Morado and Poblete, 1997b).

Selected interpreted seismic sections across some of the carbonate leads are displayed in Figure 12a-c and Figure 12d-e. In many of them, all of the qualities required for reef definition on seismic, eg. mounded form, discontinuous internal reflections, onlap of surrounding sediments and drape of overlying sediments, are seen (Morado and Poblete, 1997b). Hence, their presence in the NW Sulu Sea Basin is unequivocal.

Areal closures of Early Miocene carbonate leads range from 6.5 to 104 square kilometers with vertical reliefs ranging from ~250 to 500+ meters. These size ranges are considered to be large for this type of play and could contain potential giant hydrocarbon accumulations. Most of the Early Miocene carbonate leads are in shallow waters (<200>

Type C: Middle Miocene Carbonate Buildup

Several Middle Miocene carbonate leads have also been mapped. They are indicated on seismic in Figures 11a, 11c and 12b. Their areal extent range between 9.0 and 75 square kilometers with vertical reliefs from ~300 to 1,000 meters. As with the Early Miocene carbonate leads, the Middle Miocene carbonate leads have giant sized volumes. Note that in Figure 12b, the Early Miocene carbonate is overlain by the Middle Miocene carbonate. This geological situation would therefore offer multiple reservoir objectives on this location.

The Middle Miocene reefs either developed directly on top of Early Miocene reefs or on residual highs left by the Early Miocene reefs due to compaction, or on top of Base Middle Miocene Unconformity highs (cf. Fig. 7). Good analogues for the Middle Miocene reefal plays are those found in the Luconia Shoals of Sarawak where several giant gas fields have been discovered, in the North Sumatra Basin, in East Natuna (Terumbu Carbonate) and offshore Danang-Vietnam along the Triton Horst (Murphy, 1997).

Type D: MioceneTurbidites

Basin floor turbidites have been observed from several seismic lines cutting across the deep water part of the NW Sulu Sea Basin. The extent of each turbidite section, however, have not yet been delineated at present. Some sections show thick, multiple stacking of individual turbidite units ranging in age from Early to Middle Miocene. This geological situation would offer multiple target reservoir objectives on this location.

An interpreted seismic section showing a typical Miocene turbidite section in the basin is presented in Figure 13. In the NWPA, the Galoc and Octon field discoveries are fine examples of Miocene turbidite plays. In the Sandakan Basin, in southeast Sulu Sea, similar plays were found to be hydrocarbon-bearing. Miocene turbidites are the current major plays in the SE Asian region, as shown by latest discoveries offshore Kalimantan, offshore Sarawak, etc.

7. Conclusions and Recommendations

Our studies show that the NW Sulu Sea Basin has the potential to be a major petroleum-producing region in this part of SE Asia and the world. It may contain a potential petroleum system that is very similar to the proven petroleum system in the adjoining NWPA. Currently, four major play types have been seismically mapped in the basin.

It is therefore recommended that further and more detailed serious exploration be conducted in the area. Exploration success in the area will depend on the use of new technologies. This view is already supported by the vast improvement of seismic data quality from 1981 to 1994 resulting in a better understanding of the petroleum potential of the east Palawan area in general.


The authors would like to thank South China Resources, Inc., particularly Messrs. Edgardo P. Reyes and David R. Baladad, for granting permission to present and publish this paper. We would also like to thank our colleagues at COMEXCO, Inc. for their contributions particularly in the drafting of the text and figures.

References Cited

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Branson, D. M., Newman, P. J., Scherer M., Stalder, P. J. and Villafuerte, R. G. (1997). Hydrocarbon habitat of the N. W. Palawan basin, Philippines. Proceedings of the Petroleum Systems of SE Asia and Australasia Conference, Indonesian Petroleum Association, 815-828.

Bureau of Energy Development (BED) (1986). Sedimentary Basins of the Philippines - their Geology and Hydrocarbon Potential.

Citco Philippines Petroleum Corporation et al (1980). Dumaran No.1 Final Well Report.

Citco Philippines Petroleum Corporation et al (1982). Paly No.1 Final Well Report.

COMEXCO, Incorporated (1997). Evaluation of the East Palawan Non-Exclusive Geophysical Permit (NEGP) for South China Petroleum and Exploration, Incorporated, In house report.

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Anthropology E-20 on Sulu

Lecture Topics

(these are roughly edited transcripts of class meetings for student use only and are not for publication or quotation)

Jan. 31 Introduction

Feb. 7: Fieldwork

Feb. 14: Culture and Society

Feb 21: Cultural Dynamics

Feb 28-March 7: Language and Communication

March 14: Culture, Self, and the Individual

March 21: Subsistence and Ecology

April11: Economy

April 18: Kinship and Marriage


Anthropology E-20

Harvard University

Spring 2002

Thursday 7:35-9:30

Sever Hall 103

Dr. Thomas M. Kiefer Email


Study Questions for Text

Instructions for Term Paper

Practice Midterm


Sulu Archipelago rain forests (IM0156)

Sulu Archipelago rain forests
Tawitawi Island, Sulu archipelago, Philippines
Photograph by Arvin Diesinos

Tropical and Subtropical Moist Broadleaf Forests

900 square miles (2,300 square kilometers) -- about the size of Rhode Island

· Location and General Description
· Biodiversity Features
· Current Status
· Threats
· Ecoregion Justification
· References
More Photos

Although these islands represent transitional stepping stones from the island of Borneo to Mindanao in the Philippines, they have evolved their own distinctive faunas. Almost no forest remains on Sulu, and only the eastern portion of Tawitawi is forested. The islands are extremely politically unstable, which exacerbates a difficult conservation situation.

Location and General Description

This ecoregion includes the main islands of Jolo (Sulu) and Tawitawi and the surrounding smaller islands from Sibutu up to but not including Basilan Island. The climate of the ecoregion is tropical wet (National Geographic Society 1999). There are apparently short (two-week) dry seasons in January and May on Tawitawi (Allen 1998). The Sulus are located south of the main typhoon track that so strongly influences the more northerly Philippine islands (Dickinson et al. 1991).

The Philippines are essentially accreted terrains, an accretion of previously isolated island archipelagos that were brought together during the collision and partial subduction of large oceanic tectonic plates.

The precursors of the Sulu Islands were an arc of submarine volcanoes that have existed for at least 25 million years. However, the Sulus were not clearly above-water islands until within the last 15 million years (Hall and Holloway 1998). The islands are low-lying and coralline (limestone). Bongao Peak, on Bongao, reaches 300 m, and Mt. Sibangkok, the highest point on the central ridge that divides Tawitawi, reaches 532 m (Allen 1998).

During the Pleistocene, the majority of the present Sulu Archipelago was one island, separated from Basilan-Mindanao to the north and greater Sibutu (and Borneo) to the south by deepwater channels of 205 m and 290 m depths, respectively. The distances between these ice age islands were not great, however (Heaney 1986).

Vegetation types in the Sulu Archipelago originally included beach forest, lowland rain forest, scrub forest, and mangroves (Stattersfield et al. 1998). Beach forest is composed ofBarringtonia, Caesalpinia, and Terminalia. A small patch of this forest type may be found on Simunul, but this is generally an endangered habitat because of coastal development (human habitation and cultivation, coconut plantations). Formerly the most prevalent forest type on the islands (as with the rest of the Philippines), lowland rain forest, or dipterocarp forest, is now mostly cleared. Represented dipterocarp genera include Anisoptera, Dipterocarpus, Hopea, andShorea. Little information is available about the native scrub forest, which has been extensively cleared as well. Mangroves are found on the coasts throughout the Archipelago but are especially extensive on Tawitawi; mangroves around Bongao have been cleared. The principal mangrove genera include Rhizophora, Ceriops, Brugueira, Sonneratia, Avicennia, and Nypa (palms) (Allen 1998).

Biodiversity Features

Unlike that of Palawan, which is located between Borneo and the Philippines, the Sulu Archipelago's fauna is not Sundaic (Allen 1998) and, though rather small, is poorly known biologically (L. Heaney, pers. comm., 2000). Palawan was the main pathway for immigrants from Borneo to the Philippines, and the Sulus have many taxa that are identical to or derived from taxa in Mindanao. Even Sibutu, close to Borneo and separated from the rest of the Sulus by the Sibutu Passage, contains an avifauna more closely related to the Sulus than to Borneo (Dickinson et al. 1991). Although there are some Sulu birds with Sundaic distributions, the avifauna of the Archipelago is essentially Philippine (Dutson et al. 1992). The Sulu hornbill (Anthracoceros montani) is one example of an animal whose likely closest relative, the black hornbill (Anthracoceros malayanus), is from Borneo. There is a cline of relatedness to Borneo as one moves north among the islands. Sibutu contains birds of Bornean origin that are not found on Tawitawi (Allen 1998). The Sulus (Sangasanga, Bongao, Simunul, Tawitawi) also support a population of slow loris (Nycticebus coucang), a Sundaic primate that is not found in the remainder of the Philippines (Heaney 1986). There is one endemic mammal in the ecoregion (table 1). The Tawitawi Island rat (Rattus taitawiensis) is considered vulnerable (IUCN 2000).

Table 1. Endemic and Near-Endemic Mammal Species.




Rattus tawitawiensis*

An asterisk signifies that the species' range is limited to this ecoregion.

A new pig species, Sus spp. nov., is being described from the Sulus on the basis of MtDNA and skull measurements from a dead specimen (Rose and Grubb, in prep.). The same subspecies of bearded pig found on Borneo (Sus barbatus barbatus) is also found in the southwestern Sulus (Sibutu and Tawitawi), and this species can still be observed crossing open water to reach these islands from Borneo. It is unknown whether these over-water migrations are related to periodic eruptions on the Bornean mainland (Oliver 1993).

This ecoregion overlaps exactly with the Sulu Archipelago EBA. The EBA contains nine restricted-range birds, four of which are limited to the Sulus. All the restricted-range birds are forest species. Ten bird species qualify as endemic or near endemic to this ecoregion (Kennedy et al. 2000; table 2). Included in the ecoregion are the critically endangered Sulu bleeding-heart (Gallicolumba menagei), Tawitawi brown-dove (Phapitreron cinereiceps), and Sulu hornbill (Anthracoceros montani) and the endangered blue-winged racquet-tail (Prionoturus verticalis). Several endemic bird subspecies may warrant elevation to species status upon detailed review (Stattersfield et al. 1998; Collar et al. 1999).

Table 2. Endemic and Near-Endemic Bird Species.


Common Name



Sulu bleeding-heart

Gallicolumba menagei*


Dark-eared dove

Phapitreron cinereiceps*


Grey imperial-pigeon

Ducula pickeringii


Blue-winged racquet-tail

Prioniturus verticalis*


Mantanani scops-owl

Otus mantananensis


Philippine needletail

Mearnsia picina


Sulu hornbill

Anthracoceros montani*


Celestial monarch

Hypothymis coelestis


Yellowish bulbul

Ixos everetti


Brown tit-babbler

Macronous striaticeps

An asterisk signifies that the species' range is limited to this ecoregion.

Several widespread but threatened species also occur on the islands, including the critically endangered Philippine cockatoo (Cacatua haematuropygia) and vulnerable rufous-lored kingfisher (Todirhamphus winchelli) (Collar et al. 1999; Stattersfield et al. 1998).

The critically endangered Philippine crocodile (Crocodylus mindorensis) was historically found on Jolo (as well as Luzon, Mindoro, Masbate, Samar, Negros, Busuanga, and Mindanao), but the only remaining populations are found on Mindoro, Negros, Mindanao, and Busuanga. The current wild population may be approximately 100 nonhatchlings (Ross 1998).

Current Status

There is almost no forest remaining on Jolo (Sulu) Island, and only the eastern and north-central portions of Tawitawi are forested (Stattersfield et al. 1998; Allen 1998). The majority of Tawitawi was selectively logged in the 1960s and early 1970s (Allen 1998). Apparently, there were plans to replace the remaining forests of Tawitawi with oil palm plantations. The situation on the smaller islands is mixed. Sibutu and Simunul have been largely cleared (Stattersfield et al. 1998). Simunul has some patches of forest remaining that support populations of Philippine cockatoo (Cacatua haematuropygia), blue-naped parrot (Tanygnathus lucionensis), and blue-backed parrot (T. sumatranus) (Dutson et al. 1992). Sibutu has considerable secondary forest, and the island supports numerous Sulu subspecies. The last forests of Sangasanga were cleared in 1992-1993. The island of Bongao still supports forests; an unidentified jungle flycatcher collected in 1973 has not been observed since (Dutson et al. 1992). Small islands in the Tandubas group (which also includes Tawitawi and Sangasanga) still have small forest tracts that reportedly maintain populations of the endemic Sulu bleeding-heart and Sulu hornbill (Stattersfield et al. 1998).

The main population center is on Bongao, where a busy port exists. Tawitawi is not heavily populated, but future economic development on the island is a concern (Allen 1998; Stattersfield et al. 1998). Table 3 details the existing protected area on the islands.

Table 3. WCMC (1997) Protected Areas That Overlap with the Ecoregion.

Protected Area

Area (km2)

IUCN Category

Mt. Dajo



Ecoregion numbers of protected areas that overlap with additional ecoregions are listed in brackets.

Types and Severity of Threats

In general, habitat loss is the main threat to wildlife, but hunting is also a problem. Small-scale logging continues to destroy the remaining habitat (Stattersfield et al. 1998).

Justification of Ecoregion Delineation

MacKinnon (1997) identified seven subunits in the Philippines, and the Philippine BAP (Philippine DENR & UNEP 1997) demarcated fifteen biogeographic units. Udvardy (1975) identified the Philippines as a single biogeographic province. We delineated nine ecoregions in the Philippine islands, including Palawan. We deviated from Udvardy (1975), MacKinnon (1997), Stattersfield et al. (1998), and the Philippine BAP (Philippine DENR & UNEP 1997) to varying degrees and based our delineation of the Philippine ecoregions on Heaney (1993).

The islands of the Sulu Archipelago were delineated as a separate ecoregion, the Sulu Archipelago Rain Forests [IM0156]. This ecoregion includes the Tawitawi Group, Tapul Group, Jolo Group, and Samales Group of islands. These islands, with a lowland moist or semi-evergreen moist forest vegetation (Whitmore 1984), are also an EBA (Stattersfield et al. 1998) and have been identified as a distinct biounit by MacKinnon (1997) and a biogeographic zone by the Philippine BAP (Philippine DENR & UNEP 1997)


References for this ecoregion are currently consolidated in one document for the entire Indo-Pacific realm.
Indo-Pacific Reference List

Prepared by: John Morrison
Reviewed by:

This text was originally published in the book Terrestrial ecoregions of the Indo-Pacific: a conservation assessment from Island Press. This assessment offers an in-depth analysis of the biodiversity and conservation status of the Indo-Pacific's ecoregions.

For more general information on this ecoregion, go to the WildWorld version of this description.

All text by World Wildlife Fund © 2001