Indnesian Jurnal n Gescience, Vl December 2017: a few lcalities (Figure 1). Hwever, until recent years, fractured mélange basements have

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1 Indnesian Jurnal n Gescience Vl December 2017: Fracture Characteristics f Mélange Cmplex Basement in Bantimala Area, Suth Sulawesi, Indnesia Benyamin Sapiie, Muhamad Aziz ugraha, Rizky Kurniawan Wardana, and Arif Rifiyant Gelgy Study Prgram, Faculty f Earth Sciences and Technlgy, Institut Teknlgi Bandung Jln. Ganesha. 10, Bandung 40132, Indnesia Crrespnding authr: bsapiie@gc.itb.ac.id Manuscript received: June 8, 2017; revised: June 22, 2017; apprved: July 3, 2017; available nline: August 1, 2017 Abstract - A detailed gelgical mapping and fracture characterizatin had been perfrmed in Bantimala area, Suth Sulawesi, Indnesia. The gelgy f the studied area is cmpsed f pre-tertiary metamrphic, sedimentary, and igneus rcks which tectnically mixed frming a mélange cmplex. Lcated n the sutheastern margin f Sundaland, the tectnic strngly influences the fracture ccurrences in the studied area. A ttal f 3,841 fractures cmprising shear fractures, extensin fractures, veins, and jints have been measured and analyzed. The cmmn fracture rientatins are W - SE, W - E, E - SSW, and EE - WSW trends. Fractures develping in Bantimala have clearly been cntrlled by lithlgy and structure psitin (i.e. fault znes and fld hinge). The rientatin f fractures in Bantimala area is different n each lithlgy, shwing that the fracture system was cmplex. Fracture intensity in schist is higher cmpared t the ther lithlgies. The 3D fracture mdeling thrugh 3D gecellular mdeling was generated using the result frm field data measurements and analyses. Discrete Fracture etwrk (DF) was built by fifty-ne fracture sets that were analyzed frm field measurement data. Hwever, the estimatin f average fracture prsity frm mdeling varies significantly depending n lithlgy. The value f fracture prsity is relatively small, varied frm t %. A high fracture prsity number is bserved in an area with a significant fracture intensity and mst crsscutting f fracture which in turn is cntrlled by faults and lithlgy. A mélange cmplex can have high ptential as a basement fractured reservir target, where fracture distributins and their attributes will vary depending n the lithlgy as well as lcal defrmatin. Keywrds: Bantimala Mélange Cmplex, basement fractured reservir, Discrete Fracture etwrk, 3D Gecellular Mdeling All right reserved Hw t cite this article: Sapiie, B., ugraha, M.A., Wardana, R.K., and Rifiyant, A., Fracture Characteristics f Mélange Cmplex Basement in Bantimala Area, Suth Sulawesi, Indnesia. Indnesian Jurnal n Gescience, 4 (3), p DOI: /ijg Intrductin aturally, a fractured reservir is prven as a prductive reservir in numerus il fields. A basement is ne f lithlgies that perfrms as a naturally fractured reservir. A number f fractured basement reservirs have been discvered in the wrld (Kning, 1985; Kning and Darmn, IDOESIA JOURAL O GEOSCIECE Gelgical Agency Ministry f Energy and Mineral Resurces 1989; elsn, 2001; Sapiie et al., 2014). A recent il and gas explratin in the ffshre f the nrthern Madura Island discvered gas within the basement rcks. The basement lithlgy was made f varius rcks which are interpreted as part f the Cretaceus accretinary cmplex develped as mélange. Mélange cmplexes are widely distributed in the Indnesian archipelag but expsed in Accredited /JGI by: (Jurnal - LIPI, Gelgi valid August Indnesia) Acredited August 2021 by LIPI. 547/AU2/P2MI-LIPI/06/2013. valid 21 June June RISTEKDIKTI, valid May May

2 Indnesian Jurnal n Gescience, Vl December 2017: a few lcalities (Figure 1). Hwever, until recent years, fractured mélange basements have nt well been understd. Bantimala area is ne f wellknwn places where the pre-tertiary Mélange 106 E SUDALAD 4 S 8 S SUMATRA Kalimantan JAVA atuna Karimata Straits 110 E Suth China Sea Luk Ul Cmplex Lucnia Shals Rajang river muth Balingian delta Schwaner Muntains SARAWAK Semitau Ridge rth West Brne Trugh Baram delta KALIMATA Meszic/Early Tertiary deep marine sediments, mafic igneus rcks and melange WMO Mstly Meszic igneus, metamrphic, and sedimentary rcks with sme Late Palezic and Early Cenzic rcks Cretaceus granites and tnalites intruding Palezic metamrphic rcks Java Trench 114 E BRUEI Muller Mts. Meratus Cmplex Sakala Fault JS-1 Ridge Early Cretaceus vlcanic arc and philite sequence Ophilite basic/ultrabasic units Cretaceus granites Tectnic Element 114 E Sabah delta Mahakam Delta Patemster Platfrm 118 E Sandakan delta SABAH Straits Mahakam 118 E Sulu Sea Mangkalihat Peninsula SULAWESI Bantimala Cmplex Quaternary sediments Sulu Trench Celebes Sea rth Sulawesi Trench Tmini Bay Bne Gulf Sumba 122 E Ctabat Trench Banggai-Sula Blck Grntal Bay Tukang Besi-Butn Blck 122 E 126 E Mlucca Sea Sula Fault Buru Banda Sea Halmahera km Philippines Trench Seram Trugh Seram Timr TrughAustralian Cntinent Cenzic vlcanics and plutnic rcks Tertiary carbnates Tertiary sediments Meszic r yunger metamrphic and ultramafic basement cmplex Subductin zne - Surface trace f Beniff-Wadati Seismic Zne. a dipping surface f earthquake fci believed as surface f infiltrating lithsphere, serratin mrphlgy shw the tp f crust Transfrm fault - The principal fault at strike-slip plate bundaries; which pulled dwn underneath the plate bundary that cvered by crust West and rth Sulawesi Vlcan-Pltnic Arc Central Sulawesi Methamphic Belt Ophilite Melange HP metamrphic rcks (Pmpange schists) Majr Structure Fault and Fracture Zne 126 E East Sulawesi Ophilite Belt Undifferentiated 130 E S 8 S 130 E egene and Quaternary sediments Ophilite Banggai-Sula and Tukang Besi Cntinental Fragments rmal fault (dip slip) Cntinental basement and cver Cntinental basement belw sea level Cntinental and micrcntinental West Madura Offshre Lateral fault (strike-slip, wrench fault) Thrust fault (lw angle) Spriding axis r ridge Reverse fault (high angle) Figure 1. Tectnic and lcatin map f studied area at Bantimala Cmplex, Suth Sulawesi, shwing structural pattern and tectnic units. West Madura Offshre is an il and gas field where well penetrates basement with similar rck types expsed at Bantimala area (mdified frm varius surces). 122

3 Fracture Characteristics f Mélange Cmplex Basement in Bantimala Area, Suth Sulawesi, Indnesia (B. Sapiie et al.) Cmplex basement is expsed alng river beds. The area lies in the suth arm f Sulawesi in the sutheastern margin f Sundaland. The Bantimala Mélange Cmplex is excellent fr understanding a mélange cmplex basement reservir since it is well expsed in a river in Pangkep-Bne-Barru Regency, Suth Sulawesi. The study was cncentrated in Bantimala and surrunding areas. Administratively, the area includes Pangkajene and Kepulauan (Pangkep), Bne, and Barru Regencies in Suth Sulawesi Prvince, Indnesia. In the UTM crdinate system, the studied area is lcated in the zne f 50S m and me. The Bantimala Cmplex is a pre-tertiary mélange tectnic cmplex, and als perfrms as basement rcks in the suth arm f Sulawesi. Accrding t its lcatin that has strngly been affected by yunger tectnics, the basement is well predicted t be the hme f high intensive fractures. The main purpse f this study is t understand the fracture distributins and characteristics in the basement utcrp f mélange cmplex rcks. In additin, this study will develp a fracture mdel and characterize the relatinship between lithlgy and fracture distributin in the mélange cmplex basement. Furthermre, the result f the study hpefully can be used as an analg mdel fr basement fractured reservir explratin activity within the il field in West Madura Offshre (WMO) at the East Java Basin (Figure 1). The reginal recnstructin shws that bth Bantimala and WMO areas are lcated n the sutheastern margin f Sundaland and share a similar gelgical setting, particularly during the Cretaceus time. Cnsidering this idea, the fracture interestingly shares similar characteristics. Thus, the result f this study in Bantimala can be a preliminary reference fr further and advanced basement explratin in WMO. Materials and Methds fracture characteristics f this kind f lithlgy, the study invlves fieldwrk activity and subsurface mdeling as well. Several stages f this research are as fllws. Gelgical Mapping The gelgical mapping cvered an area f abut 560 km2 (20 km x 28 km) in the Bantimala area. The bjectives f the gelgical mapping are t cnvey infrmatin f the structure and stratigraphy within the area. It is als t determine where the mst suitable areas are fr cnducting the scan line sampling in the studied area. At this stage, the primary data were cllected frm the field bservatin while satellite images and literatures frm previus researchers were als used as secndary data. Labratry activities such as petrgraphic and micr-palentlgy analyses had als been cnducted t supprt the gelgical interpretatin. The analysis f fracture data is needed t knw the characteristics f the fracture system in the studied area. The interpretatin was cnducted t investigate factrs cntrlling the fracture distributin in the mélange cmplex basement (e.g. lithlgy, structure). Scan Line Sampling fr Fracture Characteristics The scan line sampling was emplyed in the Bantimala Mélange Cmplex and sme Cretaceus t Tertiary rcks. There were frty-seven lcatins f scan line which was successfully cnducted during the study. Fracture data were cllected by the 1D scan line methd. The data that were bserved using the scan line sampling are fracture types, rientatin, length, aperture, spacing, and filling material (Figure 2). Fracture data cllected frm the field bservatin were then prcessed int the tables, diagrams, graphs, and were analyzed in rder t understand their characteristics. The result f this step will then be used as a guidance in the next fracture mdeling step. This study presents a cmprehensive methd regarding the fracture distributin in the mélange cmplex basement. In rder t understand the Fracture Mdeling The fracture mdeling was cnstructed t perfrm cnceptual visualizatin using DF 123

4 Indnesian Jurnal n Gescience, Vl December 2017: (Discrete Fracture etwrk) algrithm (Winberg et al., 2003). The DF apprach is a mdeling methdlgy that aims t describe the fractures in statistical calculatin by generating a series f discrete fracture bjects based n field bservatins f fracture prperties, such as size, rientatin, and intensity. Reliable data are needed t make a gd fracture mdel. Data such as aperture, length, and type f fracture will guide the distributin f fracture. Furthermre, these data will be used t determine ther prperties, such as fracture prsity. 124 A 1916 Z L S Figure 2. Scan line sampling methd shwing measurement f fracture attributes such as fracture length, aperture, and spacing. Z-Z is the length f scan-line measurement; A is the aperture size f the fracture; S is the spacing between adjacent fractures; and L is the trace length f the fracture. Reginal Gelgy Tectnic Setting Sulawesi is lcated within a critical psitin in the Indnesian archipelag. Tectnically, it is situated between a number f majr lithspheric plates; i.e. the nrthward mving Ind-Australian Plate, the westward-mving Pacific Plate, and the suth - sutheastward mving Eurasian Plate A Z (Hall and Smyth, 2008). Tectnic evlutin f the suthwestern part f Sulawesi is related t the cllisin between Eurasia and East Java Micrplate during Late Cretaceus frming the last bundary f Sundaland margin (Figure 3). Sulawesi and its surrunding islands can tectnically be divided int fur belts. Each belt shws characteristic lithlgical assciatin and tectnic envirnments. Thse are Western Sulawesi Vlcan-Plutnic Belt, Central Sulawesi Metamrphic Belt, Eastern Sulawesi Ophilite Belt, and Banggai-Sula Micrcntinent Platfrm (fr detail see Figure 1). The studied area is lcated in the Western Sulawesi Vlcan-Plutnic Belt. This belt can be divided int tw nrth - suth trending muntain chains, the Western Divide Muntains and the Bne Muntains. The Walanae River runs in a graben-like structure, knwn as the Walanae depressin, which ccupies the area between these tw muntain chains. This structure frms a majr nrth t nrthwest trending fault zne (Walanae Fault Zne). This depressin appears t structurally separate Suth - West Sulawesi frm the rest f the western arc. The structural and tectnic pattern f this regin is strngly influenced by the Walanae Fault Zne, which is manifested as a majr - S lw bunded n the east and west by majr sinistral wrench faults (Figure 4). The Walanae Fault Zne divided the Suth Sulawesi int tw parts. T the west f the fault zne it is an uplifted area, dminated by a muntainus belt f Late Tertiary vlcanic rcks knwn as Camba Vlcanics. The Bantimala Cmplex and the verlying Cretaceus sediments were intensively faulted during the Pli-Pleistcene times as a result f the nrthward mvement f the Banda Sea Micrplate with respect t western Indnesia (Berry and Grady, 1987). Stratigraphic Setting Reginal stratigraphy in this study referred t the stratigraphy f Western Suth Sulawesi by previus researchers and cmpared t this study as shwn in Figure 5.

5 Fracture Characteristics f Mélange Cmplex Basement in Bantimala Area, Suth Sulawesi, Indnesia (B. Sapiie et al.) Befre 70 M.A. a M.A. b Suth China Sea Pasific Plate Sunda Micr Plate SFZ Lu par Bangka Shear Su bdu n Early Cretaceus Subductin Jurassic-Cretaceus Magmatic Arc Cretaceus Magmatic Arc Meratus Belt r ste n ter Pa Jatibarang Pa r ste n ter Ecene Magmatic Arc Palecene-Ecene Subductin Luk Ul Melange Cmplex G Indian-Australian Plate Bangka Shear SFZ cti a 0M Suthesi w Sula Bantimala Melange Cmplex Magmatic Arc Magmatic Arc Suture Zne Suture Zne M.A. c IJ O 20-5 M.A. d Rifting-Spreading Oligcene Magmatic Arc Magmatic Arc Oligcene-Micene Subductin IDIA-AUSTRALIA PLATE Suture Zne Java Trench Magmatic Arc Suture Zne Cimandiri Fault Sakala Fault Zne Citanduy Fault Bantimala Cmplex Outer Ridge IDIA-AUSTRALIA PLATE Figure 3. Tectnic evlutin f Eastern Sundaland margin during Cretaceus Plicene shwing evlutin f Bantimala Mélange Cmplex (studied area) as part f the cllisin between Eurasia and East Java Micrplate (mdified frm Sribudiyani et al., 2003). Bantimala Tectnic Cmplex The Bantimala Cmplex is a tectnic assemblage f varius lithlgies ranging in age frm Jurassic t Cretaceus. The main cmpnents f the Bantimala Cmplex are sandstne, shale, cnglmerate, chert, siliceus shale, basalt, ultramafic rcks, schist, and metamrphic breccia. The stratigraphic relatinships amng the cm125

6 Indnesian Jurnal n Gescience, Vl December 2017: Tempe Depressin Key t Lithlgies 4.5 S Pare-pare 4.5 S Alluvial Depsits Lake Tempe Pleistcene Vlcanics (Lmpbatang) 5 S 5.5 S 6.5 S Makassar Strait Barru MAKASSAR E 120 E Walanae Depressin Lmpbatang Vlcan Sengkang Sinjai 5 S Watampne 5.5 S 6.5 S Lcatin Map Walanae Frmatin Tacipi Limestne Member f Walanae Fm. Plicene Vlcanics (Camba Fm.) Micene Trachyte Intrusin Olig-Micene Carbnates (Tnasa Fm.) Ecene-Oligcene Clastics (Malawa Fm.) Palecene Vlcanics (Bua/Langi) Upper Cretaceus Clastics (Balangbaru Fm.) Pre-Tertiary Basement Majr Fault/Lineaments Studied Area Figure 4. Reginal gelgy and structure map f Suthwest Sulawesi regin mdified frm varius surces shwing rck units and majr structures as well as lcatin f the studied area pre-tertiary basement knwn as Bantimala cmplex (red bx). pnents are mstly unclear because f their fault cntacts with each ther. All the cmpnents are surrunded by sheared claystne matrix. Balangbaru Frmatin Balangbaru Frmatin cnsists f flysch sequences that are depsited in a deep-water envirnment (bathyal - abyssal). The Balangbaru Frmatin is widely distributed in nrtheast and nrth f Bantimala area. These Cretaceus flysch sediments are predminantly interbedded sandstne and silty shale with subsidiary cnglmerates, pebbly-sandstne, and cnglmeratic-breccia. The sediment was uncnfrmably depsited n the Bantimala subductin cmplex and uncnfrmably verlain by Ecene sediments (Cffield et al., 1997). Palecene Vlcanic Rcks They cnsist f andesitic lava and pyrclastic depsits with trachyandesite cmpsitin and have intercalatins f limestnes and shales. Palecene vlcanic rcks in the Biru area are called Langi Vlcanics, while in the sutheast Bantimala, are knwn as Bua Vlcanics (Yuwn et al., 1988). Sukamt (1982) called the unit as a prphylitized vlcanic rck because f its strng alteratin. In a mre detailed mapping, vlcanic rcks in eastern Bantimala are called Alla Frmatin (Sukamt, 1986). These Palecene vlcanic rcks were uncnfrmably depsits ut at the tp f Balangbaru Frmatin. Malawa Frmatin The Malawa Frmatin cnsists f sandstne (arkse), siltstne, claystne, marl, and cnglmerate km 126

7 Fracture Characteristics f Mélange Cmplex Basement in Bantimala Area, Suth Sulawesi, Indnesia (B. Sapiie et al.) Ma Age Perid Cretaceus Micene Oligcene Ecene Palecene Early Middle Late Early Middle Late Middle Late Early Late Early Middle Sukamtn and Supriatna (1982) interbedded with layers f cals and limestne. This frmatin is thught t be depsited frm terrestrial t shallw marine envirnment. This Ecene transitinal sequence is lcated in the western part f Suth Sulawesi and is generally dminated by quartz-rich sandstnes. In additin, this frmatin has uncnfrmably verlain the Balangbaru Frmatin and interfingering with the Palecene vlcanics. Tnasa Frmatin The Tnasa Frmatin cnsists f limestne, marl, sandstne, siltstne, and claystne which were depsited in Late Ecene-Micene (van Leeuwen, 1981). The frmatin was depsited cnfrmably ver Traja Frmatin (Malawa Frmatin) and Langi Vlcanics. This frmatin is widespread in the western part f Suth Sulawesi, where this frmatin is nt expsed in the eastern part f the Walanae Valley. Garrard et al. (1988) Hasan (1991) Hall and Smyth (2008) This Study Upper Camba Fm. Walanae Tacipi Upper Camba Fm. Erasa Mlasse Trachyte Malawa Fm. Tnasa Fm. Balangbaru Fm. Lwer Camba Fm. Langi Vlcanic Bua Vlcanic Basement Cmplex Tnasa Fm. Camba Fm. Tnasa Fm. Malawa Fm. Sal Kalupang Balangbaru Fm. Basement Sppeng Vlcanic Langi Vlcanic Balangbaru Fm. Tnasa Fm. Malawa Fm. Bua Member Panggalungan Member Allup Member Basement Accretinary Cmplex Malawa Fm. Tnasa Fm. Lwer Camba Fm. Langi Vlcanic Balangbaru Fm. Basement Cmplex Breccia Unit Pasrang Dacite Limestne Unit Sandstne Unit Langk Dirite Camba Frmatin The Camba Frmatin is lcated in the western part f Suth Sulawesi, and it cmprises vlcanic breccia, cnglmerate, lava, and tuff, interbedded with marine sedimentary rcks. The frmatin is alkaline due t upper mantle partial melting that has incmpatible elementsrich with metasmatism. This may be related t the previus subductin in the Early Micene in the cntext f intraplate extensin. Alkaline nature is thught t be caused by an excessive assimilatin f melted ld limestne and jining the cntinental material int the vlcanic arc subductin (Yuwn et al., 1988). Gelgy f The Studied Area Panettekang Dirite Claystne-Sandstne Unit Basement Melange Cmplex Bua Vlcanic Figure 5. Reginal stratigraphy f Suth Sulawesi area shwing cmparisn f several previus study and this study (see text fr detail). A detailed gelgical mapping during the fieldwrk activity in Bantimala area, resulting 127

8 Indnesian Jurnal n Gescience, Vl December 2017: in a detailed gelgy map. This was dne nt nly t understand the gelgical setting f the studied area, but als with the aim t determine where the mst suitable lcatins fr cnducting scan line sampling methd as well. Figure 6 shws a detailed gelgical map f the studied area. Mélange Cmplex Unit, Claystne-Sandstne Unit, Andesite Lava-Tuff Unit, Pasrang Dacite Intrusin Unit, Langk Dirite Intrusin Unit, Sandstne Unit, Limestne Unit, Breccia Unit, Erasa Syenite Intrusin Unit, Panettekang Dirite Intrusin Unit, Cllvial Depsit Unit, and Alluvial Depsit Unit underlie the Bantimala area km Bantimala Mélange Cmplex Unit The Mélange Cmplex Unit is the ldest rck in the studied area and cmpsed f a tectnic assemblage f slabs and blcks cnsisting f sandstne, schist, ultramafic rcks, metamrphic breccia, chert, basalt, and cnglmeratic sandstne (Figure 7). The tectnic slabs are riented W - SE and dip steeply t the east. Stratigraphic and structural relatinships amng the cmpnents are unclear. Each blck is bunded by fault which is a kind f a structure bundary. Matrix Mélange The matrix f the Mélange Cmplex Unit is sheared claystne. The matrix is widely distri- Explanatin Alluvial Depsit Clluvial Depsit Erasa Syenite Intrusin Panettekang Dirite Intrusin Breccia (Camba Vlcanics) Limestne (Tnasa Fm.) Sandstne (Malawa Fm.) Pasrang Dacite Intrusin Langk Dirite Intrusin Andesite Lava - Tuff (Bua Vlcanics) Claystnee - Sandstne (Balangbaru Fm.) Bantimala Melange Cmplex Matrix Chert Sandstne Basalt Schist Ultramafic Metamrphic Breccia Stratigraphic Cntact Reverse Fault rmal Fault Strike-slip Fault Syncline Anticline Figure 6. A detailed gelgical map f Bantimala cmplex resulting frm fieldwrks shwing varius rck units and majr structural bundaries. The equivalent frmatin name refers t reginal stratigraphic nmenclatures as presented in previus figure. 128

9 Fracture Characteristics f Mélange Cmplex Basement in Bantimala Area, Suth Sulawesi, Indnesia (B. Sapiie et al.) a An0910//IKOL An0910 XIKOL b c d e f g h Bn0307//IKOL An1202//IKOL An0634//IKOL An0605//IKOL An0908//IKOL An0650 //IKOL An1502 //IKOL Bn0307 XIKOL An0307 XIKOL An0634 XIKOL An0605XIKOL An0908 XIKOL An0650 XIKOL An1502 XIKOL Figure 7. Sme field phts f varius mélange blcks fund in the studied area shwing their lithlgy characteristic and structures. The third and furth clumns are micrphtgraphs thin sectin f the blcks f the first and secnd clumns. (a) claystne f matrix mélange; (b) blueschist; (c) ultramafic rcks; (d) greywacke sandstne; (e) basalt; (f) chert; (g) breccia; (h) cnglmeratic sandstne blcks. 129

10 Indnesian Jurnal n Gescience, Vl December 2017: buted in the Mélange Cmplex Unit. In the matrix, there wuld be tectnic clasts but in small sizes. The mst distinct utcrps f the matrix and small size blcks ccur near the junctin f the Pangkajene River, Pateteyang River, and Cempaga River. Als, the majr clasts in this mélange are metamrphics, sandstne, chert, ultramafics, and basalt. The clast sizes range frm several millimeters t several hundred meters. The clasts are lcally in budinage structures, smetimes shwing a chatic rientatin (Figure 7a). Schist Blck The Schist Blcks are lcated in the central part f the Mélange Cmplex Unit. The schist blcks are mainly cmpsed f green schist, blue schist, phyllite, lcally eclgite quartzite, and gneiss. The schist blcks well utcrp in Pateteyang, Bntri, and Cempaga River. The blueschist blck is lcally brecciated. This blck is cmmnly fliated nrthwest-sutheast by the trend and 34 t 48 by the dip angle. The result f petrgraphic analysis shws the lithlgy in schist blck is glauchphane-mica-garnet schist, quartz-mica schist, and glaucphane-mica schist (Figure 7b). K-Ar radimetry has been cnducted frm mica cmpnents f schist in Bantimala with an age range f 132 t 113 Ma (Wakita, 2000). Ultramafic Blck Ultramafic rcks f the Mélange Cmplex Unit are mainly distributed in the nrthern and eastern part f the cmplex. The ultramafic rcks are mstly serpentinized peridtite and serpentinite, generally dense, pale green t bluish green rcks, with a waxy luster and tend t be slickensided in the hand specimen. The rcks are cmmnly fund disrupted, fractured, and sheared as shwn in Figure 7c. The petrgraphic analysis shws that this blck has the sea and island texture cnstructed by livine and serpentine. 130 Sandstne Blck The Sandstne Blck is lcated in the central part f the Mélange Cmplex Unit, well utcrps in Paremba River (Figure 7d). This blck is cmpsed f thinly bedded sandstne and shale. Sme sedimentary structures such as parallel laminatin and crss laminatin can still be recgnized in this unit. The sandstne in this blck is grey, medium t fine-grained, subrunded - subangular grain shapes, well srted, and cmpact. This sandstne beds have a range f dip angles varying frm 16 t 48, striking - S t W - SE. The petrgraphic analysis shws that the sandstne in this unit culd be classified as lithic-wacke. Based n lithlgy characteristics, the sandstne unit is equivalent t Paremba Sandstne (Sukamt, 1986). Sukamt and Westermann (1993) reprted that sandstne in Bantimala Mélange Cmplex yielded Early t Middle Jurassic age based n the fssil presence, which were Ammnites (e.g. Liassic fuciniceras), gastrpds, and brachipds. Fractures in this unit cmmnly present as shear fractures, which are dminantly t be riented in W - SSE directin. Basalt Blck The Basalt Blck is distinctly expsed in Dengeng-dengeng River and Paremba River, as can be seen in Figure 7e. The basalt is very dark grey t black and massive structure. Petrgraphically, it shws that these basalts have an intergranular texture and cnsist f pyrxene and plagiclase. Chert Blck The Chert Blck is lcated in the sutheastern f the Mélange Cmplex Unit. The blck is well expsed in the Baruttung River. The chert layers range frm 1-20 cm thick, and are smetimes intercalated with thin shale. The bedded chert is mstly red r reddish brwn. The chert is mainly cmpsed f radilarian skeletns and fragments. Quartz and calcite veins usually fill the extensin fractures in the chert unit (Figure 7f). Fractures in this unit cmmnly present as shear fractures that have an E - W rientatin. Breccia Blck Breccia is a sedimentary rck cnsisting mainly f metamrphic rck fragments. The blck is mstly distinct in the suthwestern f the Mélange Cmplex Unit in Baruttung River,

11 Fracture Characteristics f Mélange Cmplex Basement in Bantimala Area, Suth Sulawesi, Indnesia (B. Sapiie et al.) while the distributin als ccurs in the nrthwestern f the Mélange Cmplex Unit. The main cmpnent f this breccia is schist with cm sized, angular - subangular, bad srted, and carse sand matrix. Quartzite als cmpses as fragments in this breccia (Figure 7g). Cnglmeratic Sandstne Blck The Cnglmeratic Sandstne Blck is situated in the eastern part f the Mélange Cmplex Unit. The blck is distinctly expsed in Kambtti River. The sandstne clur ranges frm grey t dark grey, pebbly - carse sand grain size, subangular - subrunded, medium srted, and plymict. The fragments are schist, basalt, marble, quartz, and sandstne (Figure 7h). Pre-Tertiary and Tertiary Rcks The Claystne-Sandstne Unit (Balangbaru Fm.) lies uncnfrmably n the Bantimala Mélange Cmplex Unit. This unit was depsited in a marine fan envirnment during the Late Cretaceus (Hasan, 1991). The vlcanic activity ccurred during Palecene resulting in Andesite Lava-Tuff Unit (Bua Vlcanics) in the Bantimala area. This unit has uncnfrmable stratigraphic relatinship with the Claystne-Sandstne Unit. The ther vlcanic prducts during Palecene are Pasrang Dacite Intrusin Unit and Langk Dirite Intrusin Unit. Bth f them intrude the Mélange Cmplex Unit. During Ecene, Makassar Strait rifting tk place and caused the depsitin f Sandstne Unit (Malawa Fm.). This unit was depsited in the fluvial - transitin envirnment, recgnized by cal seam and limestne particularly. Fllwed the rifting events, Limestne Unit (Tnasa Fm.) was depsited during Late Ecene - Middle Oligcene where sagging tectnic events began. Tnasa Limestne was widely spread as karst hill landscape in the suth arm f Sulawesi. In Bantimala area, this limestne has Late Ecene - Middle Oligcene in age. The vlcanic activity became active fr the secnd time in Late Micene. This vlcanic prduct is well knwn as Camba Frmatin. The Camba Frmatin is cmpsed f marine vlcanic and sedimentary rcks (Bergman et al., 1996). In the Bantimala area, the Camba Frmatin Unit culd be mapped int detailed units as Breccia Unit, Erasa Trachyte Intrusin Unit, and Panettekang Dirite Intrusin Unit. Quaternary alluvial depsits are mstly situated in the western part f the Bantimala area. This unit cnsists f varius uncnslidated material sizes ranging frm clay t gravel. The material riginated frm the ldest rck, which widely spread at the upstream side in the eastern part f the studied area. Fracture Characterizatin Fracture is a general term fr material failure n brittle cnditin (Kestler et al., 1995). In this research, the definitin f fracture is mre underlined fr naturally frmed fractures. The ther definitin is by elsn (2001), that reservir fracture is natural macrscpic discntinuity plane n rcks, which is frmed by defrmatin r physical diagenesis. Accrding t the directin f mvements, fractures in rck are classified as extensin and shear fractures. Shear fracture invlves parallel mvements f a fracture plane, while the mvement f extensin fracture is perpendicular t the fracture plane. Fssen (2010) illustrates varius types f fracture as seen in Figure 8a. The fracture type that was bserved in the Bantimala area cnsisted f fault/shear, gash/vein, extensin fracture, and jint (Figure 8b). Fracture characterizatin in this study is cnducted using surface fieldwrk and subsurface mdeling. Gelgical mapping and scan line sampling are the first fieldwrk activities t cllect gelgical and fracture data frm the Bantimala and surrunding area. Thus, thse fracture data are srted in rder t divide the fracture system int several fracture set and t btain fault-related fractures. After all, the subsurface mdel will be generated using data bserved frm the field. Fracture types, distributin including rientatin, density and intensity vary in each lithlgy 131

12 Indnesian Jurnal n Gescience, Vl December 2017: a b Shear fracture Jint Extensin fracture Shear fracture Styllite Vein Jint s 2 Jint s 3 Vein Extensin fracture Figure 8.Types f gelgical fractures bserved and mapped in the studied area. a) shear fractures (SF) and extensin fractures (EF) including jint (JT) and vein (VE) (mdified frm Fssen, 2010). b) Types f fractures bserved. within mélange blcks in the Bantimala cmplex (Figure 9). A ttal f 3,841 fractures is measured in the studied area frm varius lcatins and lithlgy, particularly cncentrated in different mélange blcks. Strike and dip rientatin are different in each lithlgy, especially in mélange cmplex blck units (Figure 10). Based n statistical analyses using bth lwer hemisphere steregraphic prjectins and rse diagram f fracture rientatins it indicates varius fracture trends. The main rientatins are relatively W - SE, - S, and E - SW trendings (Figure 11). The fracture intensity is defined as the number f fracture per length unit, and it becmes an essential attribute f a fracture pattern. The field bservatin and measurement indicated that fracture intensity in schist is the mst intensive fractured spt in The Bantimala Mélange Cmplex. This fracture intensity that has been measured frm the field is used fr subsurface mdeling in the further step. Fracture Mdeling The main purpse f this study is t understand fracture distributin) in basement rcks fr helping t develp fracture mdelings in subsurfaces. One f the prblems in explring natural fracture reservirs is t distribute fractures in 3D rck vlume. The fracture mdelings were directed t build a discrete fracture netwrk frm field data, and furthermre t determine the fracture prsity. Fault gemetry, lithlgy distributin, and gelgical crss sectin are the main cmpnents used fr cnstructing a gemetrical mdel f the studied area. Fractures mdeling (3D Gecellular mdeling) in this paper was build using Petrel 2016 sftware frm Schlumberger with wrkflw presented in Figure 12. Grid and 3D Cube Due t the cmplexity f the relatinship with the mélange unit, structural gridding was used in this mdeling (withut pillar gridding). The three-dimensinal cube was generated by cmbining the SRTM (Shuttle Radar Tpgraphic Missin) image and surface gelgy with cnstant depth f 1,000 m belw sea level. The cmplex structure f the mélange cmplex causes prblems fr cmmn gemetry mdeling. Stair-step faulting is used fr the mdeling f cmplex fault relatinship. The cmplex rela- 132

13 Fracture Characteristics f Mélange Cmplex Basement in Bantimala Area, Suth Sulawesi, Indnesia (B. Sapiie et al.) b c d f IJ O e G a Figure 9. Outcrp phtgraphs shwing types f fractures bserved in the studied area: (a) quartz VE bserved in interbedded chert and red limestne; (b) SF in schist; (c) SF in ultramafic rcks; (d) SF and JT in clay matrix; (e) SF in sandstne; (f) SF in mudstne. VE= vein; SF= shear fractures; JT= jint. tinship f each blck in the mélange cmplex unit is prperly mdeled using stair-step faulting prcess. Stair-step faults are created based n fault gemetries, which have been defined in the structural framewrk. Stair-step faulting wuld cnvert a fault mdel int stair-step faults making them int stair-step frm. The lithlgy was distributed using facies mdeling accrding t a plygn and pint that was created based n the gelgical map and crss sectin. The rck units are vertically dipping with the aim t make mdel simpler (Figure 13). The grid size (in meter) used in the mdel is 100x100x65 with the ttal cell f 1,288,000. Fracture Guide Mdel Several parameters such as distance t the fault, distance t the surface, and lithlgy are measured t ascertain the structure cntrl f fracture distributin. These three prperties were created n gemetrical mdeling, with sme calculatin t apprach the real number. Distance t the surface is a linear functin, while the distance t fault was calculated using equatin between distance and fracture intensity. Distance t the surface als plays a rle in the fracture distributin, as well as lithlgy. Distance t a fault, distance t the surface, and lithlgy are used as a fracture intensity guide t distribute the fracture 133

14 Indnesian Jurnal n Gescience, Vl December 2017: Breccia (Camba Vlcanic) Ultramafic Rcks Basalt Sandstne Blck Schist Trachyte Limestne km Sandstne (Malawa Fm.) Claystne Matrix Breccia Blck Chert Claystne (Malawa Fm.) Dirite Claystne (Balangbaru Fm.) Sandstne (Balangbaru Fm.) Figure 10. Distributins f fracture rientatin f each lithlgy (mélange blcks) in Bantimala Area shwing varius rientatins with three majr trends: W SE, S, and E SW. This trending variatin is interpreted due t different ages, defrmatins histry, and envirnment f frmatins f the blcks (see text fr detail). intensity. Basically, mdeling can be cnducted with a limited number f gd data that assume frm the scan line traverse. The Bantimala Mélange Cmplex is cmpsed f varius tectnic blcks which cme frm different ages and envirnments. Therefre, each blck has different characteristics and indicates that lithlgy als cntrls the fracture distributin. All structure and lithlgy cntrls are set up as parameters t build a fracture intensity guide. The fracture intensity guide will be used in distributing fracture intensity thrughut the studied area. Fracture Intensity Mdel The Fracture Intensity Mdel is the intensity f fracture that is inferred frm scan line data 134

15 Fracture Characteristics f Mélange Cmplex Basement in Bantimala Area, Suth Sulawesi, Indnesia (B. Sapiie et al.) W S 200 E W S E Clr Density Cncentratin n = 3841 Figure 11. Ttal f 3841 fractures are delineated frm field bservatin. Fracture rientatin is cmmnly W-SE, W-E, E- SSW, and EE-WSW. This trending variatin is interpreted due t different ages, defrmatins histry, and envirnment f frmatins f the blcks (see text fr detail). Simple Gridding DF Parameters Gemetry: fracture length Make Hrizn Orientatin: a. main fracture dip azimuth b. main fracture dip angle c. cncentratin Aperture size and scaled up int grid mdel. The fracture intensity mdel was generated frm the guidance f fracture guide that was generated befrehand. The mdeling result shws that the mst ppulus fracture will ccur n the red clured zne and the less fracture appeared n the turquise clured zne (Figure 14). The main cntrls n this distributin f intensity mdel are the Structural Framewrks (Based n Field Data) Structural Gridding 3D Structural Mdel Fracture Intensity (Kriging Methd) Fracture Mdeling (Discrete Fracture etwrk) ODA Methd Fracture Prsity Layering Fracture Intensity Guide Distance t surface Distance t fault Lithlgy Stchastic Methd Stair-step Fault Figure 12. 3D fracture mdeling wrk flw used in this study using PETREL. distance t the fault, distance t the surface, and their intensity. Discrete Fracture etwrk Discrete Fracture etwrk (DF) is a methd that can describe the fracture netwrk in the field as a mdel (Dershwitz et al., 2002). The main idea t make this cncept is by using 135

16 Indnesian Jurnal n Gescience, Vl December 2017: Y-axis X-axis Z-axis Z-axis Lithlgy Units G X-axis Undefined Alluvial Cllvial Camba Breccia Tnasa Limestne Matawa Sandstne Balangbaru Claystne Langk Dirite Pasrang Dacite Erasa Trachyte Panettekang Dirite Bua Vlcanic Matrix Schist Blck Ultramafic Blck Sandstne Blck Chert Blck Basalt Blck Breccia Blck Cnglmerate Blck Y-axis IJ O Figure 13. 3D gelgical mdel f Bantimala Cmplex shwing lithlgy distributins and structural relatinship. The mdel was generated based n field mapping (see text fr detail) Y-axis X-axis Z-axis Z-axis X-axis Y-axis Intensity Intensity Critical (U) Figure 14. 3D fracture intensity mdel that is built and guided frm bth structure and lithlgy cntrl shwing high intensity fracture area is strngly cntrlled by faults. 136

17 Fracture Characteristics f Mélange Cmplex Basement in Bantimala Area, Suth Sulawesi, Indnesia (B. Sapiie et al.) be parameters fr generating DF. The length f fractures is distributed using the pwer law. The aperture f fractures has a range frm 0-1 mm, and is als distributed using the pwer law. All parameters are generated t prduce a discrete fracture netwrk mdel as seen in Figure 15. As an example, a zmed-in fracture set in claystne matrix shws dminatin f tw sets f fracture system (Figure 16). Fracture Prsity The secndary prsity r fracture prsity was playing an imprtant rle in rcks, because it culd prvide an ecnmic value. Scaling up the DF mdel using scale up fracture netwrk prperties generates a fracture prsity mdel (Oda, 1985). The value f prsity varies frm t %. The high fracture prsity number is fund in an area with a significant fracture intensity and mst crsscutting f fracture which is cntrlled by faults and lithlgy (Figure 17). IJ O G sme limited data, such as a fracture frm a scan line mapping and distribute it by using sme fracture guidance and several parameters. In a 3D Gecellular DF mdel (Petrel sftware), the fractures and faults, and their prperties are generated directly frm that cell-based infrmatin. The guidance cnsisted f distance t the fault, distance t the surface, and lithlgy intensity. The rientatin f fracture in Bantimala area is different n each lithlgy, shwing that the fracture system was cmplex. The distributin f fracture rientatin is guided by lithlgy. There are fifty-ne fracture sets, which is distributed in the discrete fracture netwrk mdel using the stchastic methd. All f the fracture set rientatin were generated by the Fisher methd (Fisher et al., 1987; Allmendinger et al., 2012). The Fisher methd describes the distributin f fracture angles in much the same way as fr cntinuus variable. The Fisher mdel methd gives mre istrpic data fr fracture deviatin. The length and aperture are bth fracture gemetry, which wuld Discrete Fracture etwrk (dip azimuth) Y-axis X-axis Z-axis Z-axis Dip azimuth (deg) Y-axis Figure Figure 15. Discrete Fracture etwrks (DF) mdeling f the Bantimala Mélange Cmplex (Dip Azimuth) using 51 fracture sets resulted frm field measurements. 137

18 Indnesian Jurnal n Gescience, Vl December 2017: Dip azimuth (deg) Lithlgy: Claystne (matrix) Fracture sets: E/78 W 352 E/61 E Figure 16. Example f zmed-in fracture sets in claystne matrix frm Discrete Fracture etwrks (DF) mdel as presented in Figure 15. Analysis and Discussin The Bantimala Mélange Cmplex cnsists f an assemblage f metamrphic, igneus, and sedimentary rcks, which were tectnically mixed. Each blck came frm different ages and envirnments. Cnsidering the varius natural frming f each blck, they will have different characteristics in any circumstances as well. This study has shwn that fractures in the Bantimala Mélange Cmplex are strngly cntrlled by lithlgy and fault znes. A fractal analysis is the first imprtant step in rder t determine the fracture distributin. The fracture intensity shws a cmparative frequency f fracture presence n a certain distance interval. In the Bantimala area, the fracture intensity is dminantly cntrlled by lithlgy. The number f fracture intensity is increasing t the brittleness f rcks. The field evidence indicated the Bntri Metamrphic Rcks and Jurassic Paremba Sandstne blcks have an intensive fracture since they are the mst brittle unit amng thers. The structure psitin in a particular fault als has the cntrl in fracture distributin, where the fracture intensity increases twards the structure bundary. The result f this mdeling can be used fr cnducting basement fractured reservirs in the West Madura Offshre (WMO), in particular designing drilling targets. Using this mdeling result, explratin wells shuld be drilled slightly incline tward the SE directin in rder t penetrate a maximum fractured area. Certainly, detailed reservir gemechanic wrks need t be dne in WMO field t have a better understanding cncerning subsurface stress cnditin. Applying results frm gemechanic t fracture distributins, explratin well can be directed 138

19 Fracture Characteristics f Mélange Cmplex Basement in Bantimala Area, Suth Sulawesi, Indnesia (B. Sapiie et al.) Prsity Mdel Y-axis X-axis Z-axis G IJ O Prsity (m /m ) ceitical fracture_prsity 3 Prsity (%) Min 4.11 x Max Average ceitical fracture prsity Figure 17. Fracture prsity distributin mdel shwing high prsity area is cntrlled by fault, fracture intensity, and lithlgy (see text fr detail). Structural factrs as well as lithlgy types played a critical rle in the develpment f basement fractured reservirs in the Bantimala Mélange Cmplex. Detailed structural mapping in the area revealed the fllwing pints: Cnclusins 1. The fracture type that was bserved in the Bantimala area cnsists f fault, shear fracture, gash fractures (vein), extensin fractures, and jints. 2. A ttal f 3,841 fractures are measured frm varius different mélange blcks. Strike and dip rientatin are different in each lithlgy where the main rientatins are relatively W - SE, - S, and E - SW trendings. 3. The rientatin f fracture in Bantimala area is different n each lithlgy, shwing that the t cut critically stress fractures which will have better permeability. 139

20 Indnesian Jurnal n Gescience, Vl December 2017: fracture system was cmplex. The fracture intensity in schist is higher cmpared t the ther lithlgy in the Bantimala Mélange Cmplex. 4. Discrete Fracture etwrk (DF) mdel was generated using fifty-ne fracture sets frm field measurements, which are distributed using the stchastic methd. 5. The value f the fracture prsity is relatively small, varied frm t %. The high fracture prsity number is bserved in an area with a significant fracture intensity and mst crsscutting f fracture which in turn is cntrlled by faults and lithlgy. The cnclusin is that the Mélange Cmplex can have high ptential as a basement fractured reservir target, where fracture distributins and their attributes vary depending n the lithlgy as well as lcal defrmatin. It is believed that the recgnitin f fracture styles, distributin, and intensity in each mélange blck is an essential factr in explring their ptential, particularly fr planning explratin well lcatin. Integrated fieldwrk and 3D gecellular mdeling results are prven as a pwerfull apprach t help understanding the fracture distributins in space. 140 Acknwledgements This research is part f nging evaluatin f aturally Fractured Reservir ptential in Western Indnesia at the Gedynamic Research Grup ITB. The authrs thank students and staff f Gelgical Engineering Study Prgram, Faculty f Earth Science and Technlgy ITB in supprting this research. Thanks are expressed t Pertamina WMO gelgists fr their cntributin and knwledge sharing f their prject in basement fractured reservir in the mélange cmplex. References Allmendinger, R.W., Cardz,., and Fisher, D.M., Structural Gelgy Algrithms: Vectrs and Tensrs. Cambridge, England, Cambridge University Press, 289pp. DOI: /CBO Bergman, S.C., Cffield, D.Q., Talbt, J.P., and Garrard, R.A., Tertiary Tectnic and magmatic evlutin f western Sulawesi and the Makassar Strait, Indnesia: evidence fr a Micene cntinent-cntinent cllisin. In: Hall, R. and Blundell, D. (eds.), Tectnic Evlutin f Sutheast Asia, Gelgical Sciety Special Publicatin. 106, p DOI: /GSL.SP Berry, R.F. and Grady, A.E., Messcpic structures prduced by Pli-Pleistcene wrench faulting in Suth Sulawesi, Indnesia. Jurnal f Structural Gelgy, 9, p DOI: / (87) Cffield, D.Q., Guritn,., Wilsn, M.E.J., and Ascaria,.A., Petrleum Systems f Suth Sulawesi, Indnesia. In: Hwes, J.V.C. and ble, R.A. (eds.), Prceedings f the Cnference n Petrleum Systems f SE Asia and Australasia, p Dershwitz, W., Klise, K., Fx, A., Takeuchi, S., and Uchida, M., Channel etwrk and Discrete Fracture etwrk Mdeling f Hydraulic Interference and Tracer Experiments and the Predictin f Phase C Experiments. SKB Reprt IPR Stckhlm, SKB. Fisher,.I., Lewis, T., and Embletn, B.J.J., Statistical Analysis f Spherical Data. Cambridge University Press, 329pp. DOI: /CBO Fssen, H., Structural Gelgy. Cambridge University Press, 463pp. DOI: / CBO Garrard, R.A., Supandjn, J.B., and Surn, The Gelgy f The Banggai-Sula Micrcntinent, Eastern Indnesia. Prceedings, Indnesian Petrleum Assciatin, 17 th Annual Cnventin, p Hall, R. and Smyth, H.R., Cenzic arc prcesses in Indnesia: identificatin f the key influences n the stratigraphic recrd in active vlcanic arcs. In: Draut, A.E., Clift, P.D., and Schll, D.W. (eds.), Lessns frm the Stratigraphic Recrd in Arc Cllisin Znes,

21 Fracture Characteristics f Mélange Cmplex Basement in Bantimala Area, Suth Sulawesi, Indnesia (B. Sapiie et al.) The Gelgical Sciety f America Special Paper 436. DOI: / (03) Hasan, K., The Upper Cretaceus Flysch Successin f the Balangbaru Frmatin, Suthwest Sulawesi. Prceedings, Indnesian Petrleum Assciatin, 20 th Annual Cnventin, p Kestler, A.G., Milnes, A.G., and Keller, P., Quantificatin f fault/fracture systems and their flw behaviur - Based n field analgues. GEO-RECO A.S. Reprt , Munkedamsveien 59, 0270 Osl, rway. Kning, T. and Darmn, F.X., The gelgy f the Beruk rtheast Field, Central Sumatra-il prductin frm pre-tertiary basement rcks. Prceedings, Indnesian Petrleum Assciatin, 13 th Annual Cnventin, p Kning, T., Petrleum Gelgy f the Ombilin Intermntane Basin, West Sumatra. Prceedings, Indnesian Petrleum Assciatin, 14 th Annual Cnventin, p elsn, R.A., Gelgic Analysis f aturally Fractured Reservirs. Gulf Publishing Cmpany, Hustn, Texas, 352pp. Oda, M., Permeability tensr fr discntinuus rck masses. Gétechnique, 35 (4), p DOI: /get Sapiie, B., Purwaman, I., Burhan,., Lanin, E.S., Tren, E.Y., Apriansyah, D., and Iskandar, O., An Outcrps Analgue t Basement Fractured Reservir f Suban Gas Field, Suth Sumatra Basin, Indnesia. Gelgical Sciety f America, Annual Meeting, British Clumbia. Sribudiyani, Muchsin,., Ryacudu, R., Kunt, T., Astn, P., Prasetya, I., Sapiie, B., Asikin, S., Harslumaks, A.H., Yuliant, I., The cllisin f the East Java micrplate and its implicatin fr hydrcarbn ccurrences in the East Java Basin. Indnesian Petrleum Assciatin, 29 th Annual Cnventin, IPA03- G-085, 12pp. Sukamt, R., Gelgi Lembar Pangkajene dan Watampne bagian barat, Sulawesi, skala 1: Gelgical Research and Develpment Centre, Bandung. Sukamt, R., Tektnik Sulawesi Selatan dengan Acuan Khusus Ciri-ciri Himpunan Batuan Daerah Bantimala. Dctral Thesis at Institut Teknlgi Bandung, Bandung (unpublished). Sukamt, R. and Supriatna, The Gelgy f Pangkajene and Western part f Watampne, Sulawesi, Gelgical Map, scale 1: with explanatry nte. Gelgical Survey f Indnesia in cperatin with USGS. Sukamt, R. and Westermann, G.E.G., Indnesia and Papua ew Guinea. In: Westermann, G.E.G. (ed.), The Jurassic f the Circum Pacific, Cambridge University Press, p DOI: /CBO Van Leeuwen, T. M., The gelgy f Suthwest Sulawesi with special reference t the Biru area. In: Barber, A.J. and Wirysujn, S. (eds.), The Gelgy and Tectnics f Eastern Indnesia, Gelgical Research and Develpment Centre, Special Publicatin. 2, p Wakita, K., Cretaceus accretinary-cllisin cmplexes in central Indnesia. Jurnal f Asian Earth Science, 18, p DOI: /S (00) Winberg, A., Anderssn, P., Byegård, J., Pteri, A., Cvetkvic, V., Dershwitz, W., De, T., Hermansn, J., Gmez-Hernandez, J.J., Hautjärvi, A., Billaux, D., Tullbrg, E-L., Hltn, D., Meier, P., and Medina, A., Final Reprt f the TRUE Blck Scale Prject, Reprt 4, Synthesis f flw, transprt and retentin in the blck scale. SKB Technical Reprt TR Stckhlm, SKB. Yuwn, Y.S., Belln, H., Maury, R.C., and Seria-Atmadja, R., Tertiary and Quaternary gedynamic evlutin f Suth Sulawesi: cnstraints frm the study f vlcanic units. Gelgi Indnesia, 13, p