Indnesian Jurnal n Gescience, Vl August 2015: E 110 E 115 E Sumatra Sunda- Asri Basin Belitung Basin J AVA S E A SE limit f Cretaceu

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1 Indnesian Jurnal n Gescience Vl August 2015: IDOESIA JOURAL O GEOSCIECE Gelgical Agency Ministry f Energy and Mineral Resurces Jurnal hmepage: h p://ijg.bgl.esdm.g.id ISS (Print), e-iss (Online) Seismic and Sequence Analysis f Middle t Late Micene Depsits f rtheast Java Basin Hw t cite this article: Yuniardi, Y., Seismic and Sequence Analysis f Middle t Late Micene Depsits f rtheast Java Basin. Indnesian Jurnal n Gescience, 2 (2) p DOI: /ijg Intrductin Backgrund Sequence stratigraphy is ne f the main cncepts in hydrcarbn explratin by means f predictive analysis in sediment packages. This methd is very useful fr identifying ptential reservir rck with a stratigraphic trap. It can als shw pitfalls in the structural traps frmed in the basin. This methd helps the explratin effrt fr a new hydrcarbn accumulatin, field develpment, and reserve estimatin. This article shws an applicatin f sequence stratigraphy in E Java Basin. The rtheast Java Basin is ne f the sedimentary basins in Indnesia (Figure 1), which has a great hydrcarbn ptential. Ac- Yuyun Yuniardi Faculty f Gelgy, Padjadjaran University Jln. Raya Bandung - Sumedang Km. 21 Jatinangr, Indnesia Crrespnding authr: yuniardi2004@yah.cm Manuscript received: April 10, 2015; revised: April 23, 2015; apprved: August 6, 2015; available nline: August 25, 2015 Abstract - This study is fcused n Middle t Late Micene sediments. As depicted in the reginal gelgy f Indnesia, the area f study is part f rtheast Java Basin. There are three phases f tectnism in the basin: extensinal tectnics at Ecene-Oligcene time, cmpressinal tectnics at Middle Micene, and cmpressinal tectnics at Micene-Plicene time. The result f the study shws three sequences were develping during Middle t Late Micene, thse are: (1) Middle Micene sequence-1 (MM-1 sequence) cnsisting f a Lwstand Tract System depsitin in Middle Micene-1 (LST MM-1), Transgressive System Tract depsitin in Middle Micene-1 (TST MM-1), and Highstand System Tract depsitin in Middle Micene-1 (HST MT-2); (2) Middle Micene sequence-2 (MT-2 sequence), cmprising Transgressive System Tract Middle Micene-1 (TST MM-2), and Highstand System Tract depsitin in Middle Micene-1 (HST MM-2); (3) Late Micene sequence-1 (LM-1 sequence), cmpsed f a Lwstand Tract System depsitin in Late Micene -1 (LST LM-1) and a Transgressive System Tract depsitin in Late Micene-1 (TST LM-1). Keywrds: Java Basin, Micene depsits, seismic, sequence stratigraphy crding t Martdjj (198), this basin is lcated in an area surrunded by five sedimentatin regimes: stable-shelf cntinent (Rembang Zne), transitin zne (Randublatung Zne), unstable marine basin (Kendeng Zne), vlcanic zne, and suthern cntinental shelf (suthern muntains). The rtheast Java Basin was the result f a cllisin between the Sunda Micrplate and the Indian Plate. The tectnic psitin f the rtheast Java Basin is lcated n the back-arc basin frmed in the Early Tertiary subductin-related prcess in Java. Accrding t Tucker (1982), the analysis f sequence stratigraphy can be dne thrugh several methds, including seismic and bistratigraphic analysis. /JGI (Jurnal Gelgi Indnesia) - Acredited by LIPI. 54/AU2/P2MI-LIPI/06/2013, valid 21 June June

2 Indnesian Jurnal n Gescience, Vl August 2015: E 110 E 115 E Sumatra Sunda- Asri Basin Belitung Basin J AVA S E A SE limit f Cretaceus granite W limit f Cretaceus melange Meratus Mts 6 S rth West Java Basin 6 S rth East-East Java Basin JAVA rthern Slpe Bgr - Kendeng Trugh Madura Suth West Java Basin Suthern Slpe 8 Suth Central Java Basin 8 9 S Micene-Plicene deepwater sedimentatin Quartenary vlcanes Olig-Micene vlcanic-magmatic arc Figure 1. Lcality map f the researched area (red square). Seismic stratigraphy is a stratigraphic interpretatin based n data frm seismic reflectin. Sme characters appear in every seismic sectin which helps in explaining the stratigraphy f an area. In this setting, seismic data can be integrated with bistratigraphic data, which identify the depsitinal age and depsitinal envirnment ccuring in the system. Based n the abve mentined, a study has been cnducted based n the seismic data integrated with well data n the sequence stratigraphy f sediments in the Middle t Late Micene time in the regin, part f the rtheast Java Basin E 110 E 115 E Sequence Stratigraphy System Tract f Sequence Stratigraphy System tract is a cntact between depsits f similar ages (Psamentier, in Walker and James, 1992). The timing is based n bistratigraphy. The system tract bundaries are identified and crrelated based n discntinuities. All f discntinuities are the result f fluctuatins in a relative sea level. Referring t the cncept f depsitinal sequence prpsed by Walker and James (1992), there are fur types f system tracts: Lw-Stand System Tract (LST), Transgressive System Tract (TST), High-Stand System Tract (HST), and Shelf Margin System Tract (SMST). The presence f each system tract is dependent n the type f sequence bundary. If a depsitin frms the type 1 sequence, then the system cntains the LST, TST, and HST. The type 1 sequence bundary implies that the resulting system tract has been influenced by sea level changes t achieve reductin in a shelf break. Type 2 sequence cntains SMST, TST, and HST. The system tracts f this type is the result f decreasing relative sea level fall, that des nt reach a shelf break. 9 S Depsitinal Sequence Analysis The depsitinal sequence is basically determined by bjective criteria such as the relatinship between the physical layers, s that the

3 cncept is very useful fr the develpment f a reginal stratigraphic framewrk. This cncept is nt affected by the amunt f rck-type determinatins, fssils, depsitinal prcesses, and ther criteria which are generally subjective and varieted (varied?) thrughut the sequence itself. Sangree et al. (1993) described several types f seismic reflectin terminatins: Onlap is the terminatin fr strata that were initially tilted. Onlap is usually seen at the base f a depsitinal sequence and can indicate a sequence bundary. Marine nlap is a cnditin where prgressive marine strata nlap tward the mainland r t an elevated tpgraphy n the basin. Castal nlap is terminated fr prgressive castal depsitin tward the mainland. Dwnlap is where yunger layers prgrade ver the lder nes. Tplap represents psitins initially tilted up against yunger cvering layers. Ersinal truncatin is the cnditin where the upper part f lder layers are angled t yunger nes. East Java Sedimentatin Regime As mentined in the Intrductin part, Martdjj (198) divided East Java int five sedimentatin regimes frm nrth t suth: stableshelf cntinent (Rembang Zne), transitin zne (Randublatung Zne), unstable marine basin (Kendeng Zne), vlcanic zne, and suth cntinental shelf (suthern muntains). Accrding t Martdjj (198), the Rembang Zne crsses thrugh the nrthern bundary f Java Island which is detached frm the Randublatung Zne by Lusi River n the west, Kening River n the east, and Sl River n the east. Sandstne and carbnates intercalated with marl and claystne are cmmn in these areas, which had been depsited n the cntinental shelf. The regin f Randublatung Zne had been determined by Bemmelen (1949) including the Blra-Cepu Hills and gimbang-dander Hills. This zne is dminated by marl and claystne with sandstne, calcarenite, and carbnate interbeds that act as imprtant reservirs. Thse Seismic and Sequence Analysis f Middle t Late Micene Depsits f rtheast Java Basin (Y. Yuniardi) sediments are interpreted t be depsited n an undulated-cntinental slpe. Bemmelen (1949) als described that the Kendeng Zne was dminated by vlcanclastics and marls with sme claystne, sandstne, and carbnate interbeds, that were derived frm deep cean basin depsits. Fine sediments are mre abundant than carse material, and can act as reservirs. The rate f the depsitin is very rapid and may be greater than the rate f the subsidence. Depsitinal Sequence f rtheast Java Basin Stratigraphically, the rtheast Java Basin can be divided int three majr depsitinal sequences, thse are the Ecene-Early Oligcene sequence, the Late Oligcene-Micene sequence, and Pli-Pleistcene sequence (Kusumastuti et al., 1999). The Early Ecene- Oligcene sequence is assciated with the rifting phase cntaining bth clastic and carbnate sediments. The Ecene clastics were depsited in river envirnments, including freshwater lakes (lacustrine). The primary surce material frming hydrcarbns ccurred in thse envirnments. The Late Oligcene-Micene sequences are separated by a reginal uncnfrmity beneath the cver sequence with EE-WSW rientatin. They ccured as carbnate shelf depsits frmed during the Late Oligcene knwn as Prupuh Frmatin fllwed by the frmatin f Early Micene reef limestnes. During the Middle t Late Micene, the presence f a relatively large supply f sediment cming frm the nrth and suth f the basin led t the cessatin f the carbnate depsitin. The depsitin f the vlcanclastics verlies mst f the suthern basin, distributed frm the nrthern part f Java t the recent Madura Cast. The Pli-Pleistcene sequences were uncnfrmably depsited n the Late Oligcene t Early Micene sequence, that in sme places were erded thrughut the Middle-Late Micene sequence. The sedimentatin sequence, in the studied area, was cmmenced frm the eastern part f the basin ccurring as limestne f the 103

4 Indnesian Jurnal n Gescience, Vl August 2015: Paciran Frmatin and marl f the Kalibeng Frmatin in the western part f the basin. The Paciran Frmatin cmprises limestne rich-in pelagic Glbigerina f which westwardly the Glbigerina cntent increases thrughut the marl f Kalibeng Frmatin. The depsitin f Paciran Frmatin and Kalibeng Frmatin was fllwed by the prgrading-wedge sediments f the Pucangan and Lidah Frmatins. The Pucangan Frmatin cnsists f vlcanclastic sediments derived frm the vlcanic belt in the suthern part f the basin, whilst the Lidah Frmatin is equivalent t the marine sediments f the Pucangan Frmatin cntaining marine shale and limestne debris (detritus) frm limestnes that frmed earlier. This frmatin is distributed widely in the Kendeng Zne. In the stratigraphy f Madura Strait, the Pucangan Frmatin has different facies with Snde Frmatin (Kusumastuti et al., 1999). At the end f the Pli-Pleistcene t Recent, terrestrial sediments (nnmarine) were depsited as the Kabuh Frmatin and tpur Frmatin. Methds The bjective f the study is t determine the Middle t Late Micene sequence in rtheast Java Basin, lcated in Regin, then t cnduct analyses f the sedimentatin packets. After that, t place them int a sequence stratigraphic framewrk. In the analysis, the seismic stratigraphic methd was applied supprted by bistratigraphy and well-lg data that are available fr this research. The data were taken frm Balawan, lcated in the eastern part f the studied area, and Flint well, situated in the western part f the studied area. The tw wells partially penetrated the analyzed sedimentary packages. The distributins f the system tracts can be bserved by seismic trajectry cntrlled by the well-lg data. The bistratigraphy data in this study is primary data needed fr determining the age f the hrizn analyzed. The bistratigraphic data were prvided and analyzed by the LEMIGAS (Lembaga Minyak dan Gas Bumi/ Research and Develpment Centre fr Oil and Gas) tgether with several reprts frm ther cmpanies. The data were used fr determining age bundaries (hrizn) f Early Micene t Late Micene, and then they were tied t the seismic data. Results and Discussin Middle Micene-1 Sequence (MM-1 Sequence) This sequence was depsited as the type-1 sequence in the late Early Micene sediment intervals. This sequence thins mainly t the suthwest and nlap n the uncnfrmity. The Middle Micene-1 sequence (MM-1 sequence) is cmpsed f Lwstand System Tract depsitin in Middle Micene-1 (LST MM-1), Transgressive System Tract depsitin in Middle Micene-1 (TST MM-1), and Highstand System Tract depsitin in Micene Middle-1 (HST MM-1). This system tract was depsited abve the Early Micene sediments. The depsitin f the Lwstand System Tract in Middle Micene-1 (LST MM-1) ccured when the sea level receeded faster than the subsidence f the basin. The rapid drp f the sea level led t the develpment f dwnlap patterns (Figure 2), while n seismic it shws the patterns f nlap, which describes the lwstand depsitin prcess that cntinues until the sediment supply n lnger culd keep pace with the accmmdatin cntinue t be frmed by the subsequent rise in the sea level. These shw that the lwstand depsitin prcess cntinued until the sediment supply n lnger culd keep pace with accmmdatin by the subsequent rise in the sea level. The dispersal f the Lwstand System Tracts depsitin in Middle Micene-1 (LST MM-1) ccured nly in places. The depsitin f this system tract nly ccupied lwerlying areas at the late Early Micene structuring limited by elevatin in the eastern part with relative grwth t the suth-west (SW) and nrth-east (E). In general, the internal cnfiguratin f the seis- 104

5 AD-8 AD-6 AD-5 AD-4 AD-3 AD-2 Seismic and Sequence Analysis f Middle t Late Micene Depsits f rtheast Java Basin (Y. Yuniardi) S Tp f Late Micene 2 TST LM-1 2 Late Micene Sequence 1 LST LM-1 Tp f Middle Micene Middle Micene Sequence 2 3 TST MM-2 HST MM-1 HST MM-2 Middle Micene Sequence 1 TST MM-1 3 Tp f Early Micene LST MM-1 4 Tp f gimbang Carbnates 4 Tp f gimbang Clastics Tp f Oligcene 5 5 Transgressive system tract (TST) Index Map " Lwstand system tract (LST) Highstand system tract (HST) 30" Java 0 10 DK- Figure 2. Interpretatin f seismic line. mic interpreted f the lwstand system tracts shws parallel and subparallel psitins. Frm the distributin pattern, it is estimated that the sediments were accumulated in the lwer areas, extending east-west f the structure frmed n the tp f the Early Micene sediments. These structures which shaped the basin, were frmed by the remnants f a tectnic activity which well develped during the Cretaceus t Middle Ecene epch. Accrding t Martdjj (198), the Rembang Zne crsses thrugh the nrthern bundary f Java Island which is detached frm the Randublatung Zne by Lusi River n the west, Kening River n the east, and Sl River in the suth. Sandstne and carbnates intercalated with marl and claystne are cmmn in these areas, which had been depsited in a cntinental shelf. The depsitin f the Transgressive System Tract Middle Micene-1 was preceeded by a rise in the sea level that inundated almst the entire shelf area previusly expsed by the sea level fall. The spreading pattern f the Transgressive System Tracts depsitin in Middle Micene-1 (TST MM-1) ccupied a slightly wider area than the spread pattern f Lwstand System Tract depsitin in Middle Micene-1 (LST MM-1). This was caused by the additin f accmdatin space fr sediment accumulating by a relative sea level rise. The seismic nlap patterns indicate that the sea level rise accmpanied this Lw Stand System tract depsitin system (Figure 3). Its distributin shws that the Transgressive System Tract depsitin in Middle Micene-1 (TST MM-1) experienced thinning twards the elevatin t the nrth and suth. The Highstand System Tract depsitin in the Middle Micene-1 (HST MM-1) began t frm when sea levels rse slwly as sediment supply cntinued t grw. This cnditin raises the patterns dwnlap n seismic (Figure 2). In general, the internal cnfiguratin f interpreted seismic f the lwstand system tract shws parallel and subparallel patterns. The spread f the Highstand System Tract depsitin in Middle Micene-1 (HST MM-1) cntinued t ccupy the same system tract depsitin limited by elevatins in the nrth and suth peaks frmed by the Early Micene sediments (Figure 3). In general, the Highstand System Tract depsitin in the Middle Micene-1 (HST MM-1) had thinned in the range secnd n parts f the bundary depsitin, especially t the west, east, and suth-west (Figure 4). The HST MM-1 sediment 105

6 AD-8 AD-6 AD-5 AD-4 Indnesian Jurnal n Gescience, Vl August 2015: S Tp f Late Micene LST MM-1 TST LM-1 Tp f Middle Micene Late Micene Sequence 1 TST MM-1 TST MM-2 HST MM-1 Transgressive system tract (TST) Lwstand system tract (LST) Highstand system tract (HST) Middle Micene Sequence 2 Tp f Early Micene Figure 3. Sectin f nlap TST MM-1 t the peak f Early Micene depsitin (range hrizn) at seismic line shwing rising f sea level. 30" S S Java Island "E AD-4 AD-2 30" DK- AD-3 AD-6 AD-5 AD-8 Java Index Map 30" S S " AD-3 AD DK "E 0. secnd secnd secnd secnd - secnd - secnd secnd secnd sediment suply directin Ischrn Map Lwstand System Stract Late Micene-1 Figure 4. Ischrn map f HST MM

7 supply is generally thught t riginate frm the nrth-nrtheast (Martdjj, 198). It is inferred frm the thickness f the sediments in HST MM- 1, then were experiencing thinning t the west, east, and suth-west. Middle Micene-2 Sequence (MM-2 Sequence) The Middle Micene-2 sequence (MM-2 sequence) cmprises the Transgressive System Tract depsitin in Middle Micene-2 (TST MM-2) and the Highstand System Tracts depsitin in Middle Micene-2 (MM-2 HST). The distributin f TST MM-2 is slightly different frm the distributin f TST MM-1, but in general it still shws thinning t the suth, suthwest, and the elevatin f the surrunding areas. The depsitin f TST MM-2 30"S S Seismic and Sequence Analysis f Middle t Late Micene Depsits f rtheast Java Basin (Y. Yuniardi) Java Island Rijang mre develped in the middle part f the studied area. Frmatin f the TST MM-2 is affected by a quick relative sea level rise that prduced nlap patterns in seismic similar t the Oligcene sediments (Figure 3). Sediment dispersal patterns are estimated t shw sediment surces fr TST MM-2 riginated frm the nrth-nrtheast. The accumulatin f the Highstand System Tract depsits in Middle Micene-2 (HST MM-2) is thicker in the western part f the studied area. In general, the HST MM-2 had been thinning in the range 0.0- secnds TWT n parts f the bundary depsitin, especially n the west, east, and suth. While the range f -0.6 secnds TWT thickening ccured in the central part f the Highstand System Tract and the Middle Mi " E AD AD AD-6 AD-5 AD-2 AD DK- S 30"S " E 0. secnd secnd secnd secnd - secnd - secnd secnd secnd sediment suply directin Ischrn Map Lwstand System Stract Last Micene-1 Figure 5. Ischrn map f HST MM-2. 10

8 AD-8 AD-6 AD-5 AD-4 Indnesian Jurnal n Gescience, Vl August 2015: cene-2 (HST MM-2). This is caused by a high sediment supply that did nt match the existing accmmdatin capacity. As the cnsequence, the depsitin mved twards the lwer basin lcated in the eastern part f the studied area (Figure 5). Late Micene-1 Sequence (LM-1) Late Micene-1 sequence (LM-1 sequence) was cntrlled by the Lwstand System Tract depsitin in the Late Micene-1 (LST LM-1) and the Transgressive System Tract depsitin in Late Micene-1 (TST LM-1). The Highstand System Tract depsitin in Late Micene-1 (HST LM-1) is estimated t develp at the next level abve the Late Micene structure. Since this study was limited nly frm the Middle Micene t Late Micene sediments, then further detailed analysis was nt dne beynd the upper peak f the Late Micene sequence. The Lwstand System Tract depsitin in Late Micene-1 (LST LM-1) is the first system tract depsited n the tp f the Middle Micene sediments. As fr the Lwstand System Tract depsitin in Middle Micene-1 (LST MM-1), this system tract was depsited when relative sea level fell faster than the decline in the basin subsidence n the basis f a relatively shallw Tp f Late Micene Tp f Middle Micene Late Micene Sequence 1 surrunding areas (the areas f shelfs). The rapid drp in the sea level generated the dwnlap patterns (Figure 6). The distributin f the Lwstand System Tract depsitin in Late Micene-1 (LST LM-1) was very brad, almst filling the entire peak f Middle Micene sediments. These sediments were limited by elevatins lcated in the suthern and nrthern parts f the studied area. Sediments thin twards the suth and west ranges between secnds TWT. This depletin ccurred due t depsitin f Lwstand System Tract in Late Micene-1 (LST LM-1), nlap t the Early Micene sediments that resulted frm a tectnic rise f the suthern studied area (Figure 6). This system tract als thickened in the middle t the west f the studied area where lwer areas range frm - secnds TWT (Figure ). The distributin f the Transgressive System Tract depsit in Late Micene-1 (TST LM-1) is different t the distributin f the Transgressive System Tract depsit in Middle Micene-2 (TST MM-2), but in general it still shws thinning t the suth. The depsitin f the TST LM-2 mre develped in almst all parts f the studied area. The frmatin f the TST MM-2 is affected by a rapid relative sea level rise which prduces nlap patterns in seismic recrdings. 2 2 TST LM-1 LST MM-1 Transgressive system tract (TST) Lwstand system tract (LST) S Middle Micene Sequence 2 Tp f Early Micene LST MM-1 TST LM-1 Middle Micene Sequence 1 3 TST LM Index Map " Highstand system tract (HST) AD-3 AD-2 DK- 30" Java 0 10 Figure 6. Interpretatin f seismic line. 108

9 Seismic and Sequence Analysis f Middle t Late Micene Depsits f rtheast Java Basin (Y. Yuniardi) " E 30" S S secnd secnd secnd secnd - secnd Figure. Ischrn map f LST LM-1. Cnclusins Java Island The sedimentatin rder in Middle Micene t Late Micene can be divided int three depsitinal sequences: Middle Micene sequence-1 (MM-1 sequence) cnsisting f the Lwstand Tract System depsit in Middle Micene-1 (LST MM-1), Transgressive System Tract depsit in Middle Micene-1 (TST MM-1), and Highstand System Tract depsit in Middle Micene-1 (HST MT-2). Middle Micene sequence-2 (MT-2 sequence), cmpsed f the Transgressive System Tract Middle Micene-1 (TST MM-2), and Highstand System Tract depsit in Middle Micene-1 (HST MM-2) Rijang secnd secnd secnd sediment suply directin AD " E AD-4 Ischrn Map Lwstand System Stract Late Micene AD-6 AD-5 AD-2 AD-3 Late Micene sequence-1 (LM-1 sequence), cmprising Lwstand Tract System depsitin in Late Micene-1 (LST LM-1) and Transgressive System Tract depsit in Late Micene-1 (TST LM-1). The analysis results f sequence stratigraphy tend t indicate that hydrcarbn ptential in the studied area is classified int tw grups, based n the type f trap, namely: Anticline trap; the depsitin LST MT-1, MT HST-1, and the HST MT-2 and the HST MT-2 stratigraphic traps; the depsitin LST MT-1 frms a pinchut feature at altitude in the nrth, HST MT-1 frms pinchut at altitude in the suth and in the nrth, HST MT-2 frms pinchut at altitude in the suth, and LST MA-1 with pinchut at altitude in the suth. DK " S S 109

10 Indnesian Jurnal n Gescience, Vl August 2015: Acknwledgment The authr wuld like t thank all thse wh have helped twards the entire prcess f drafting and publishing this paper. References Bemmelen, R.W.Van, The Gelgy f Indnesia, IA. Gvernment printing ffice, The Hague etherland, 32pp. Kusumastuti, A., Darmy, A.B., Suwarlan, W., and Ssrmihardj, S.P.C., The Wunut Field: Pleistcene vlcaniclastic gas sands in East Java. Prceedings, Indnesian Petrleum Assciatin, 2 th Annual Cnventin and Exhibitin, Jakarta, p , Martdjj, S., 198. Sedimentatin Regime f East Java. Gelgy Departement f Institut Tektnlgi Bandung (ITB), Bandung. Sangree, J.B., Mitchum, R.M., and Vail, P.R., Applicatin f Sequence Stratigraphy t Hydrcarbn Explratin. AAPG Memir, p Tucker, M.E., The Field Descriptin f Sedimentary Rcks. Jhn Wiley & Sns, ew Yrk, Trnt, 112pp. Walker, R.G. and James,.P., Facies Mdels; Respnse t Sea Level Change. Gelgical Assciatin f Canada, 409pp. DOI: /gj