Indonesian Journal on Geoscience Vol. 1 No. 1 April 2014: 21-34

INDONESIAN JOURNAL ON GEOSCIENCE Geological Agency Ministry of Energy and Mineral Resources

Journal homepage: h�p://ijog.bgl.esdm.go.id ISSN 2355-9314 (Print), e-ISSN 2355-9306 (Online)

Limestone Microfacies of Baturaja Formation along Air Rambangnia Traverse, South OKU,

Sigit Maryanto

Centre for Geological Survey, Geological Agency Jln. Diponegoro No. 57 Bandung - 40122

Manuscript received: February 14, 2012, revised: March 18, 2013, approved: April 1, 2014 Corresponding Author: [email protected]

Abstract - Limestones of the Baturaja Formation occur at Air Rambangnia traverse, South Ogan Komering Ulu, South Sumatra, and they are used as objects for microfacies studies. The microfacies studies are based on a detailed petro- graphic analysis of thirty four limestone samples, taken from the traverse. Four types of the limestones are identified such as wackestone, packstone, grainstone, and floatstone. At least five microfacies form the limestone succesion of the Baturaja Formation. They are interpreted as sedimentary facies of very restricted bay and pond, back reef local slope, slope and shelf edge, winnowed platform edge sand, and reef flank facies. Keywords: Baturaja, limestone, petrography, microfacies, sedimentary facies

Introduction The researched location was along Air Ram- bangnia River, in between Baturaja and Muaradua The term microfacies was first put forward by towns, administratively belonging to the area Brown (1943; in Flugel, 1982). It is defined as of South Ogan Komering Ulu (OKU) Regency, extensively discrete paleontology and sedimen- South Sumatra Province (Figure 1). The carbon- tology aspects, that can be grouped based on the ate rocks from Baturaja Formation are well found type and number of components in petrographic along the Air Rambangnia traverse. This article thin section and polished sample examination. was written with the aim to study the environment Thereby, microfacies identifies environment of and deposition mechanism of those limestones deposition based on petrography data (Maryanto, based on petrography data in relation to the divi- 2005 and 2008). Based on the type and number of sion of limestone microfacies. components, Flugel (1982) divides microfacies of limestone into twenty-four types according to the former division of facies zone by Wilson (1975). Methodology Wilson and Rosen (1998) stated that carbonate platform in the western part of has ap- In order to achieve the study purpose, the peared since the Late Oligocene. Bishop (2000a) research method includes field data collection concluded that the IJOGEarly Miocene of Baturaja and laboratory analysis. Field data collection is Formation consists of carbonate platform sedi- a systematical rock sampling, which is based on ments having totally thickness of 60 - 120 m. the results obtained by making detailed strati- Bishop (2000b) divided Baturaja Formation into graphic column along Air Rambangnia traverse. two lithostratigraphic units based on deposition, Laboratory work was done by quantitatively i.e. clastic sedimentary facies and limestone or petrographic analysis with point-counter for as carbonate rock facies. many as 300 counts (Maryanto, 2007a). Important

IJOG/JGI (Jurnal Geologi Indonesia) - Acredited by LIPI No. 547/AU2/P2MI-LIPI/06/2013, valid 21 June 2013 - 21 June 2016 21 Indonesian Journal on Geoscience, Vol. 1 No. 1 April 2014: 21-34

o o o o o 102 E 103 Muarabulan 104 105 106 E o o 02 S 02 S Sungailiat JAMBI Bangko SOUTH SUMATRA BANGKA BELITUNG PROVINCE Pangkalpinang

Sarolangun

03o 03o Sekayu bangka Strait

Lubuklinggau Argamakmur Kayuagung Curup Muaraenim

o Bengkulu o 04 S Lahat 04 S Pagaralam HINDIA BOCEANENGKULU Baturaja

Martapura Menggala Manna N LAMPUNG Muaradua Kotabumi 0 100 Km Investigated Traverse o o 102o E 103 104 105 o E

Figure 1. Location map of South Sumatra Province and the investigated traverse at Air Rambangnia River. aspects of petrography to be identified include: consisting of granite, andesite-basalt, metasedi- 1. the proportion of major components, such as ment, mélange, and metamorphic rocks. Uncon- carbonate grains, terrigenous grains, matrix, formable overlying the basement rocks there are neomorphism materials, cement, and rock several Tertiary Formations of Kikim, Talangakar, porosities Baturaja, Gumai, Airbenakat, Muaraenim, Ranau, 2. identification of the characters of each com- Kasai, and Alluvium (Gafoer et al., 1986, 1993; ponents, Figure 2). Limestone of the Baturaja Formation 3. texture of rocks that include fabric, sorting, in general was deposited in the back-reef environ- grain size, and shapes. The classification is ment behind the edge of the basin during the Early determined according to Dunham (1962) de- Miocene (Maryanto, 2007b). Layered limestone veloped by Embry and Klovan (1971). can be observed directly along the Air Rambangnia Microfacies interpretation of the limestones traverse. The rocks are generally sloping ramps to from the Baturaja Formation along Air Rambang- the east (Figure 3), with the total thickness of about nia traverse is divided according to the standard 220 m, measurable reach including carbonate rocks classification of microfacies from Flugel (1982) from the Baturaja Formation of 196 m thick. and facies zone from Wilson (1975). As a compari- Volcanic rocks of the Kikim Formation are son, there are also references from many authors presented as a basement. It consists of volcanic that discuss microfacies and limestone depositional breccias, volcanic sandstone, mudstone, and environment, such as Andreeva (2008), Jones and conglomeratic sandstone, with andesite lava inser- Desrochers (1992), Kindler and Hearty (1996), tions. The Baturaja Formation limestone uncon- Read (1985), and TuckerIJOG and Wright (1990). formably overlies the Kikim Formation (Figure 4). The lower part of Baturaja Formation was initiated by the presence of grainstone containing Geological Review some pore-dissolving porosities. Furthermore, the rocks become developed onto layered wackestone- Regional geology in-between Baturaja and packstone that partially argillaceous with oriented Muaradua area is preceded by Pre-Tertiary rocks fossils of mollusks (Figure 5) and algae. Several

22 Limestone Microfacies of Baturaja Formation along Air Rambangnia Traverse, South OKU, South Sumatra (S. Maryanto)

1030 54’ E 1040 15’ E

Qa Tma 0 Qtk Qhv N 0 04 06’S BATURAJA ka 04 06’S Sa Tmpm Air

0 10 Km Air Suban Besar Qtk SUMATERA Tma Tpok Batuiputih Tomt Tmb EXPLANATION: 15 Tmg 15 Tmb Qa Alluviumtu Tmg -ba atu 15 INDEX MAP Qv r BTuff Volcanic Unit

i Laja Air A a Negerisindang Tmb mb Qhv Volcanic Unit Ta 12 Air 15 Qtk QTk Kasai Formation Penyandingan QUARTERNARY 10 QTr Ranau Formation Tomt 24 Tma Tma Tmpm Muaraenim Formation 17 Tpok 15 Tma Airbenakat Formation 13 Tmg

Air Tebangka Qhv Tmg Gumai Formation Qhv Kungkilan Tmb Baturaja Formation 15Air LahatTmpm Tomt Talangakar Formation Tma Tpok Kikim Formation Tpok

PALEOGENE MIOCENE Tpokc Cawang Mem. Kikim Fm. Pct Tomt Km MelangeA Complex i r L e Tmg Kjg Garba Formationng k Air Buluh Sundanaj KJgv Insu Mem. Garbaap Fm. Sagarakembang Air Tmb Kjgs KJgs Situlanglang Mem.Sukoraja Garba Fm. Kura-kura Qtk PRE-TERTIARY Kgr Garba Granite Negeriratu Pct Pct Tarap Formation Tpok Qtk Air Rambangnia Traverse Kjgv

Tpok Kjgv Air Kiti Tmpm

Tma Tmg Air Napalan Tmb Sabahlioh KJgs Qa Tpok Air Gilas Air Saman Qtk Kjg . Kgr Airbungin Tmpm Tmb Baturaja Air Rambangnia Qtk Pct Tanjungkurung Kgr Simpang Qtr Kgr Karangagung Kjgv Pct Tpokc Km Qtr A Umbulanmeliku 15 i Tpokc KJg Saungnaga r M Mehanggin Kgr a la Tmb u Tomt Qv Kotakarang Kjgv Qtr 10 10 Kgr Tmb Air Saka Tanjungbringin Tmb Qa 25 Tpokc 15 Negeriagung Tmg PCt Tma Qa Tomt Qv Air Kemu Air Komering Qtr MUARADUA Qa Tmpm Qtr Qa Tmb Kotamarga 17 Air Selabung Qa Qa Gedong Tmpm Qtr 0 Tmg 0 Tma Qtr Sukaraja Qtr Tmpm Umbulantelok 19 04 35’S 04 35’S 1030 54’E 1040 15’E

Figure 2. Geological mapIJOG of Muaradua area, South Sumatra (Gafoer et al., 1993) and locations of Air Rambangnia traverse (Maryanto, 2007a and 2008). floatstone intercalations are found containing some The middle part of Baturaja Formation is coral skeletons. Stylobed is interlayering between composed of floatstone (Figure 6), of which later wackestone-packstone with marl ended the deposi- evolved into argillaceous wackestone. Interlayers tion of the lower part of Baturaja Formation. between floatstone with wackestone-packstone

23 Indonesian Journal on Geoscience, Vol. 1 No. 1 April 2014: 21-34

Kikim Formation Baturaja Formation Alluvium A B

196 m

Section A - B

Bedded wackestone sometimes argillaceous

Argillaceous wackestone with Argillaceous wackestone-mudstone floatstone intercalations Argillaceous wackestone-mudstone with lot of concretions Argillaceous wackestone-mudstone Conglomeratic sandstone overlain Thick bedded floatstone SM326 by packstone Argillaceous wackestone-mudstone SM325B SM325A Volcanic breccia and Bedded floatstone with argillaceous SM324C sandstone with packstone-wackestone SM318B SM324B mudstone and Floatstone and wackestone SM318A 321 SM324A 320 sometimes argillaceous SM317B 8 0 lava intercalations 0 0 SM317A 322 S 04 25’ 08,5” S 04 25’ 10,0”, E 104 09’ 02,6” 319 10 324 12 0 0 SM316B 323 10 E 104 09’ 30,5” S 04 25’ 11,3” To Baturaja SM316A 325 0 Floatstone 318 326 E 104 08’ 40,0” 317 10 312 12 Carbonaceous 8 316 327 314 SM320A B 301 315 mudstone and 313 SM320B A sandstone SM321A SM321B Bedded wackestone-packstone 302 15 311 To Muaradua SM323A SM314A Grainstone, wackestone and packstone SM301A 24 310 SM323C SM302A SM314B SM323D SM310 Argillaceous wackestone-mudstone SM302B 303 SM315A SM323E 304 SM309 SM315B overlied by grainstone 309 SM323B SM303A 305 306 SM303B Argillaceous wackestone-mudstone EXPLANATION: SM304A 10 Bedded floatstone with 8 7 308 with concretion bedding SM304B 307 SM304C argillaceous packstone-wackestone Outcrop location SM304D Argillaceous wackestone Strike and dip SM305A N 10 SM305B Fault (predicted) SM305C Clayey sandstone 305 Number of site

0 400 m 05SM305 Sample location River flow direction

FigureFigure 3. 3.Detailed Detailed stratigraphicstratigraphy measure measured map alongmap Airalong Rambangnia Air Rambangnia traverse (Maryanto, traverse (Maryanto,2007a & 2008) 2007a and sample and 2008) locations. and sample locations.

dominated the sequence, which are later fining Petrography upward onto sometimes argillaceous wacke- stone-mudstone. The next lithology is found as Based on a detailed petrography analysis, floatstone. the limestone types recognized are wackestone, The upper part of Baturaja Formation begins packstone, sandy packstone, grainstone, and float- with the presence of wackestone-mudstone lay- stone. Each of these rocks, including the number ers. Stylobedded and or siliceous concretional and type of the rock components would later be bedding reaches 80 cm in size are often found in used as the basis for microfacies determination these layers (Figure 7). The concretional bedding (Table 1). sometimes has a parallel direction to the bedding (forming lens) and it shrinks to the upper part. Wackestone The above concretional beddings are overlain Wackestone group also includes sandy by gradational and planar cross-bedding grain- mudstone-wackestone, which is present as an stones (Figure 8). Carbonate rock sequences in intercalation. The rocks are generally massive this traverse is ended by wackestone-packstone with fine-grained fragmental bioclastic texture. sometimes with dissolving porosities. Bioclast always occur and comprises diverse type, The carbonate rocksIJOG of Baturaja Formation size, and amount of fossil. Nevertheless, fossil partially do not crop out along Air Rambang- types composing the rock can be identified, such nia traverse, especially between sites 306-213. as red algae, mollusks, and foraminifera. Rarely Among that locations, the clastic sedimentary intraclast or extraclast are preserved in the rocks, rocks from Muaraenim Formation are exposed in the same as the presence of pellets. Terrigenous the form of claystone containing limestone boul- materials are still observed in some rock samples ders. The sedimentary rocks are preserved due with limited amounts, scatteredly, and uneven. to a tectonic strike-slip fault in N33oE direction. They are composed of quartz, feldspar, volcanic

24 Limestone Microfacies of Baturaja Formation along Air Rambangnia Traverse, South OKU, South Sumatra (S. Maryanto)

LITHOLOGY DESCRIPTION A G E A U N I T S T U N I SAMPLE CODE GRAIN SIZE STRUCTURE MICROFACIES THICKNESS (meter) AND THICKNESS (meter) LITHOLOGY SYMBOL LITHOLOGY AND SEDIMENTARY

CL FS CS PB BO 220 ST MS GR CO SM326 SMF10-FZ7 SM325B SMF10-FZ7 SM325A Bedded packstone-wackestone with various fossils SMF10-FZ7 SM324C SMF12-FZ6 SM324B Grainstone sometimes with cross-bedded structure SMF12-FZ6 SMF12-FZ6 SM324A SMF12-FZ6 SMF19-FZ8 SM323B Wackestone-mudstone partially chalky and recrystallized with SMF10-FZ7 SM323E SMF10-FZ7 SM323D lot of concretion fining upward SM323C SMF3-FZ3 SM323A Upper part

Stylobedded wackestone-mudstone SMF19-FZ8

SM321B SMF19-FZ8 SM321A Wackestone-mudstone partially with quartzitic concretion SMF10-FZ7 SM320B

SM320A Thick bedded floatstone partially develop to rudstone SMF5-FZ4 165 with wackestone intercalations

SMF5-FZ4 SM318B Wackestone-mudstone partially argillaceous SM318A SMF10-FZ7

SM317B SMF5-FZ4 SM317A SM316B SMF10-FZ7 SM316A Floatstone interlayering with packstone-wackestone SMF5-FZ4 SM315B

Floatstone thick bedded and poorly sorted SMF5-FZ4 Middle Part SM315A SM314B Wackestone generally argillaceous with molluscs orientation SMF10-FZ7 SM314A SMF5-FZ4

B A T U R A J A J A U R T A B Floatstone coral and lithoclast with molluscs-rich matrix E A R L Y M I O C E N Y R L A E

110 Fault Zone

SM305C SM305B SM305A Wackestone bedded, sometimes argillaceous with floatstone SMF19-FZ8 SM304D SM304C SM304B rudstone intercalations SMF10-FZ7 SM304A55 Wackestone-packstone generally argillaceous with fossils SMF12-FZ6 SM303B SM303A dominated by molluscs and algae Lower Part

SM302B Stylobedded grainstone with several dissolution pores SMF11-FZ6

SM302A

Volcanic breccia and sandstone cruedly bedded with IJOGintercalations of mudstone, conglomeratic sandstone, and andesite lava KIKIM SM301A EOCENE-OLIGOCENE 0 CL FS CS PB BO ST MS GR CO

Figure 4. Detailed lithostratigraphy column along Air Rambangnia traverse, OKU Selatan, South Sumatra (Maryanto, 2007a & 2008, with modifications).

25 Indonesian Journal on Geoscience, Vol. 1 No. 1 April 2014: 21-34

Figure 5. Massive marl contains a lot of mollusk mouldics, this point is as the lower part of the Baturaja Formation. Figure 8. Grainstone overlying mudstone-wackestone, pres- Photographed in the 303 site of the Air Rambangnia traverse. ents as a constituent of the upper part of Baturaja Formation. Photographed in the 324 site of Air Rambangnia traverse.

Clay mineral matrix in general is inseparable with carbonate mud matrix. The cement material is always present with very limited quantities, par- ticularly as orthosparite, iron oxides, authigenic clay minerals, and silica.

Packstone Packstone is generally massive with fine- to medium - grained fragmental bioclastic texture. Bioclast is composed of diverse type, size, and Figure 6. Very poorly sorted floatstone composing of the middle part of Baturaja Formation. Photographed in the 314 amount of fossil, however, it is predominated site of the Air Rambangnia traverse. by red algae, mollusks, and foraminifera. Intra- clast or exstraclast is present on the coarser size of limestone fragments, spread unevenly, and consists of coralline, bioclastic, and argillaceous limestones. Less amount of very fine pellet some- times changes into microsparite. Sparsely, terrrig- enous materials are still present sporadically dis- tributed, or sometimes excessively influence the rock name to become sandy. The rock matrix is mainly preserved as carbonate mud, which often changes onto microsparite and/or is recrystallized to form pseudosparite together with carbonate grains. Cement materials are always present in the Figure 7. Outcrop of wackestone-mudstone containing rocks as various amount of orthosparite calcite, siliceous concretions, is a constituent of the upper part of Baturaja Formation. Photographed in the 322 site of Air and rarely of iron oxides. Rambangnia traverse. IJOG Grainstone and sedimentary rock fragments, unidentified Grainstone is generally massive with medium- rock fragments, phosphate, and glauconite. Car- to coarse - grained fragmental bioclastic texture. bonate mud matrix often have changed into mi- Bioclast is quite dominant consisting of various crosparite, some even have recrystallized to form kind, size, and amount of fossil. Intraclast or pseudosparite together with carbonate grains. extraclast is observed unevenly in some coarse-

26 Limestone Microfacies of Baturaja Formation along Air Rambangnia Traverse, South OKU, South Sumatra (S. Maryanto)

Table 1. Petrography Analysis Summary of the Limestones from Baturaja Formation along Air Rambangnia Traverse, South Sumatra (Maryanto, 2007a)

SAMPLE CODE SM SM SM SM SM SM SM SM SM SM SM SM SM DESCRIPTION 302B 303A 303B 304A 304C 304D 305A 305B 305C 314A 314B 315A 315B Structure m m o m m m m m f m o f m m m m o m Texture bf bf bf bf bfc bfc bf bf bf bf bf bf bf Sorting m p p p p p p p p vp p vp vp Fabric c c c o o o o o o o o o o Av. grain size (mm) 1.80 0.70 1.40 0.30 0.20 0.20 0.20 0.80 0.20 0.80 0.80 1.20 1.80 Grain shape sr sr sr sr sr sr sr sr sr sr sr sr sa Grain contacts p l c p l c p l c f f f f p f f f p f f p f p l Percentages Carbonate Grains Green algae - 10.67 ------Red algae 1.67 1.33 1.33 0.33 - 0.33 0.67 - 1.67 0.67 1.67 0.67 2.33 Bryozoans 4.33 - 0.67 - 0.33 - 0.67 1.00 - 0.67 2.33 1.33 1.67 Echinoderms 2.67 4.00 - 1.33 - - 4.67 1.33 0.67 1.00 1.33 1.33 1.33 Coral 4.67 ------0.67 - - 1.33 3.33 8.33 Benthic foraminifera 6.00 3.00 4.00 8.00 0.67 0.67 5.67 7.33 1.67 1.67 0.67 6.33 5.00 Planktonic foraminifera 1.33 - - - - - 1.00 - - - - 0.67 0.67 Brachiopods 2.00 1.33 - - - - 1.00 0.67 0.67 1.33 1.33 1.33 2.00 Moluscs 15.00 16.33 7.33 5.33 4.00 1.67 4.33 5.67 5.00 6.00 13.00 4.00 4.67 Ostracods ------2.67 0.67 0.33 - 1.67 1.67 2.33 Sponge-spicules ------0.67 0.67 - Bioturbation ------1.00 Unidentified fossils 8.33 6.33 24.67 2.00 9.67 9.67 5.00 3.67 3.33 5.00 5.33 6.00 3.00 Intraclasts / extraclasts 5.33 - 2.67 - - - 1.33 1.67 - - 5.67 3.33 4.33 Pellet / peloids - - 0.67 ------1.33 1.00 Oolite / oncolite ------Terrigenous Grains Quartz 1.33 4.67 3.33 2.67 1.00 - 0.67 1.00 0.67 3.67 1.00 1.67 0.33 Feldspar - 0.33 1.33 0.67 - - - 0.67 0.33 2.33 0.33 0.33 - Rock fragments 1.33 6.33 10.33 2.00 1.33 - 3.00 1.67 1.33 2.00 1.33 - - Glauconite ------Phosphate ------0.67 - 1.00 - - - Opaque minerals 0.67 0.67 1.33 - - - 0.67 0.67 - 0.67 - 1.33 - Carbon ------0.67 - - 0.67 Matrix Carbonate mud - 3.33 - 22.00 - - 50.33 10.33 15.00 6.00 26.67 34.00 39.33 Clay minerals - 32.33 4.67 - - - 3.00 - - - - 6.00 - Cementing Materials Orthosparite 9.67 - - 0.67 - 2.00 1.67 4.00 3.00 4.00 3.33 8.00 6.33 Iron oxides 2.67 3.00 1.67 0.67 1.00 0.67 3.33 2.33 1.67 1.33 3.67 1.67 1.67 Authigenic clays - - 2.00 - - 2.33 - 0.67 - 1.67 - - - Silica - - - 1.33 - 2.67 0.33 - - 2.67 - - 1.00 Neomorphisms Microsparite 16.33 - - 52.33 - - 5.67 20.33 9.00 17.00 7.33 8.00 5.67 Pseudosparite 6.33 - 26.00 - 21.67 24.00 2.00 5.00 1.00 8.33 3.33 3.00 4.00 Dolomite 7.00 - 6.00 - 59.33 51.67 - 28.00 51.33 28.33 16.00 - - Micritized mud 1.33 - 1.00 - - - 0.67 - 0.67 2.33 1.00 0.67 1.33 Pyrite 0.67 ------2.67 0.67 Porosities IJOG Intraparticle ------Mouldic - 1.00 - - - - - 0.67 - - - - - Vuggy 1.33 1.67 1.00 0.67 - 4.33 1.00 1.67 2.00 1.67 1.00 0.67 1.33 Intercrystal - - - - 1.00 ------Shelter dan fenestrae - 2.33 ------1.67 - - - - Fracture - 1.33 - - - - 0.67 0.67 - - - - - Rock Name G SP SP W W W W W W W W W W/F SMF / FZ 11/6 12/6 12/6 10/7 19/8 19/8 10/7 10/7 19/8 10/7 10/7 10/7 5/4

27 Indonesian Journal on Geoscience, Vol. 1 No. 1 April 2014: 21-34

Table 1...... continued (Maryanto, 2007a)

SAMPLE CODE SM SM SM SM SM SM SM SM SM SM SM SM SM DESCRIPTION 316A 316B 317A 317B 318A 318B 320A 320B 321A 321B 323A 323B 323C Structure m m o m m m m m f m m f m o m o m p m Texture bf bf bf bf bf bf bf bf bf bf bf bf bf Sorting vp p p p p p p p p p p p p Fabric c c c o c o c c o o o c o Av. grain size (mm) 1.40 1.45 1.40 0.70 1.60 0.70 1.40 0.40 0.20 0.15 0.15 0.35 0.15 Grain shape sr sr sr sr sr r sr sr r sr r r r Grain contacts p l c p l c p l c f p l c f p l c p l c f f f p l p l c f p l Percentages Carbonate Grains Green algae - - 4.00 - 2.67 - 0.67 ------Red algae 2.33 2.33 4.33 1.33 3.67 1.00 5.33 1.67 1.67 1.67 0.67 0.67 0.67 Bryozoans 1.67 1.33 2.33 - 1.33 1.00 5.33 4.33 1.00 - - 0.67 - Echinoderms 1.33 1.33 1.33 1.00 1.00 1.33 1.33 1.67 1.33 1.33 5.33 2.33 4.67 Coral 4.67 2.67 5.33 4.00 4.00 2.67 2.67 1.67 - - - 0.67 - Benthic foraminifera 16.33 17.00 7.00 3.33 9.67 1.67 7.67 4.33 4.67 4.00 1.33 1.33 2.33 Planktonic foraminifera 0.33 2.33 0.67 0.67 0.67 - 0.67 2.67 1.00 2.67 16.33 19.67 8.33 Brachiopods 0.67 1.33 1.00 - 2.33 0.67 1.00 2.33 1.67 - - 4.00 1.67 Moluscs 5.67 13.67 21.67 4.67 19.33 7.67 12.33 9.67 8.00 2.33 7.33 10.33 7.33 Ostracods 0.67 1.67 0.33 - - 0.33 - 1.00 - - - 3.00 2.33 Sponge-spicules ------0.33 ------Bioturbation 1.33 - 1.00 - 0.67 - 1.33 0.67 - - - - - Unidentified fossils 4.67 2.00 5.00 3.00 3.00 6.00 6.33 5.00 6.00 6.33 6.00 6.00 6.00 Intraclasts / extraclasts 9.33 1.33 4.00 - 3.00 - 7.33 4.00 - - - 2.67 - Pellet / peloids 0.67 0.67 1.33 - 2.67 1.33 0.67 1.67 - 5.00 - - - Oolite / oncolite ------Terrigenous Grains Quartz 1.33 1.67 1.00 0.67 2.00 0.33 0.67 1.67 - 0.33 1.00 1.33 0.67 Feldspar 0.67 0.67 0.67 - 0.67 - - 0.67 - - 0.67 - 0.67 Rock fragments 2.33 1.33 1.67 0.67 1.33 - - 4.67 1.33 - - - - Glauconite - - 0.33 ------0.67 Phosphate 0.67 ------3.00 - - 1.00 - - Opaque minerals 0.67 0.67 0.67 - 0.67 - - 0.67 - - - 0.67 - Carbon - 0.67 ------Matrix Carbonate mud 23.33 13.67 10.67 10.00 9.33 10.00 13.33 9.33 9.33 10.67 5.00 22.33 28.33 Clay minerals ------6.00 6.00 4.00 7.00 8.00 - 8.00 Cementing Materials Orthosparite 8.00 4.67 5.67 1.67 11.00 3.00 4.33 5.67 4.00 0.67 5.33 4.33 3.00 Iron oxides 1.67 2.67 1.67 0.67 1.67 1.33 1.33 3.33 1.67 1.33 1.33 3.00 1.00 Authigenic clays 0.67 - - - - 0.67 1.00 1.33 - - - - - Silica - - - - 0.67 0.67 0.67 ------Neomorphisms Microsparite 7.33 17.00 7.00 60.33 8.00 56.33 10.67 7.00 20.67 30.67 27.67 5.67 11.33 Pseudosparite 6.00 4.67 3.00 6.67 4.00 - 3.00 5.00 20.67 3.00 5.00 2.00 2.00 Dolomite 4.00 - 4.00 - - - - 6.00 10.67 21.67 5.00 - 9.67 Micritized mud - 1.33 2.67 0.67 1.00 1.00 0.67 1.67 - 0.67 - - - Pyrite 0.67 ------0.67 - - - 0.67 Porosities Intraparticle - 0.67 ------0.67 0.67 - Mouldic IJOG0.67 - - - 1.33 0.67 1.33 - - - 0.67 - - Vuggy 1.33 2.67 1.67 0.67 3.67 2.33 4.33 3.33 1.00 0.67 1.67 8.67 0.67 Intercrystal ------0.67 - - - - Shelter dan fenestrae - - - - 0.67 ------Fracture ------Rock Name P/F P P W P W P P W W W P W SMF / FZ 5/4 10/7 5/4 10/7 5/4 10/7 5/4 10/7 10/7 19/8 3/3 10/7 10/7

28 Limestone Microfacies of Baturaja Formation along Air Rambangnia Traverse, South OKU, South Sumatra (S. Maryanto)

Table 1...... continued (Maryanto, 2007a)

SAMPLE CODE SM SM SM SM SM SM SM SM EXPLANATION DESCRIPTION 323D 323E 324A 324B 324C 325A 325B 326 Structure m m o m p m m m m p m Texture bf bf bf bf bf bf bf bf Sorting p p m m p p p p Fabric c o c c c c c c Av. grain size (mm) 0.30 0.15 1.20 1.60 1.10 0.80 0.30 0.35 Structure: Grain shape sr sr sr sr sr sr sr sr m = massive Grain contacts p l f p p l c p l c p l c p l c p l c p l c o = with grain orientation Percentages p = with several pores f = with joints and fractures Carbonate Grains Green algae ------Texture: Red algae 5.67 4.67 5.33 3.33 4.67 4.67 4.33 2.67 bf = bioclastic fragmenter Bryozoans 0.67 - 3.33 2.33 1.67 2.00 1.67 3.33 cf = clastic fragmenter Echinoderms 4.67 5.00 10.33 9.33 6.67 3.33 2.00 4.67 nc = non-clactic Coral - - 2.67 1.33 3.33 4.00 3.00 3.33 c = crystalline Benthic foraminifera 2.67 0.67 22.00 19.67 14.00 11.33 10.33 29.00 Planktonic foraminifera 7.67 4.00 0.67 1.33 4.67 2.67 5.67 0.67 Sorting: Brachiopods 2.67 2.67 2.00 1.67 4.00 2.67 2.67 2.00 vw = very well sorted Moluscs 9.33 6.33 17.00 30.33 23.00 14.00 6.33 11.33 w = well sorted Ostracods 2.67 2.67 - - 0.67 1.33 1.33 0.67 m = moderately sorted Sponge-spicules ------0.67 - p = poorly sorted Bioturbation ------vp = very poorly sorted Unidentified fossils 6.33 4.67 - - 4.33 4.00 6.00 2.67 Intraclasts / extraclasts 4.00 - 3.67 6.00 5.33 2.33 - 3.33 Fabric: Pellet / peloids 3.33 6.00 0.67 0.67 0.67 0.67 - 1.00 c = closed Oolite / oncolite ------o = opened Terrigenous Grains Quartz - 1.00 0.67 0.67 1.00 1.33 1.00 0.67 Grain shape: Feldspar ------0.33 - va = very angular Rock fragments - - - 0.67 1.33 - - - a = angular Glauconite 0.67 - - 1.00 0.67 0.67 - - sa = sub-angular Phosphate 0.67 0.33 - 0.33 - - - 0.67 sr = sub-rounded Opaque minerals - - - - - 0.67 - 1.33 r = rounded Carbon - - - - - 1.00 - - wr = well rounded Matrix Carbonate mud 9.33 17.33 - - - 6.00 12.33 12.67 Grain contact: Clay minerals 5.00 4.00 - - - - 5.00 5.67 f = floating Cementing Materials p = point l = long Orthosparite 2.67 1.00 14.00 7.67 9.00 4.33 4.67 3.33 c = concave-convex Iron oxides 1.33 1.67 1.67 1.33 1.33 1.33 6.00 2.67 s = sutured Authigenic clays - - 1.33 1.00 0.67 1.00 - - Silica 13.00 6.67 - - - 0.67 - - Rock name: Neomorphisms BW = Wackestone Microsparite 6.00 5.67 - - - 15.00 5.33 6.33 BW/F = Wackestone/floatstone Pseudosparite 3.00 3.33 6.00 6.67 3.00 4.00 - 3.00 BP = Packstone Dolomite 7.33 14.00 - - 6.00 8.00 7.67 4.00 BP/F = Packstone/floatstone Micritized mud - - 3.00 1.00 2.00 0.67 2.67 2.67 BG = Grainstone Pyrite ------0.67 SBP = Sandy packstone Porosities Microfacies: Intraparticle - 0.67 - 0.67 0.33 - 0.67 0.67 SMF = Standard microfacies Mouldic IJOG- 1.67 - 0.67 - - - - (Flugel, 1982) Vuggy 1.33 3.33 5.67 2.33 1.67 2.33 10.33 1.00 FZ = Facies zone Intercrystal ------(Wilson,1975) Shelter dan fenestrae - 2.67 ------Fracture ------Rock Name P W G G G P P P SMF / FZ 10/7 19/8 12/6 12/6 12/6 10/7 10/7 10/7

29 Indonesian Journal on Geoscience, Vol. 1 No. 1 April 2014: 21-34 sized rocks, and consists of coralline, bioclas- depositional environment is the presence of fe- tic, and argillaceous limestones. Pellet is very nestrae porosity type, as a result of a tidal activity rarely preserved. A less amount of terrigenous (Tucker and Wright, 1990). materials are present evenly at the upper part Coarse-grained packstone can be deposited in of stratigraphic sequences. They are composed another deposition environment. In some cases, of quartz, feldspar, volcanic and argillaceous, packstone can develop into grainstone with the metamorphic, and unidentified rock fragments, bioclast composed as well of coated and worn red very rarely glauconite, phosphate, mica, and algae. This rock was usually deposited in slopes opaque minerals. Cement materials are always and shelf edges (SMF12-FZ6). Abrading and present in the rocks with a diverse number as leaching of carbonate grains mark the grainstone orthosparite, iron oxides, authigenic clays, and was deposited in winnowed platform edge sands silica. Most orthosparite is present from phreatic (SMF11-FZ6). meteoric environment, followed by marine and Packstone can be interpreted as reef-flank fa- burial environments. Small amount of iron oxides cies (SMF5-FZ4), characterized by the presence fills cavities and fractures in the rock. Authigenic of bioclasts mostly derived from the reef dwell- clay minerals are preserved as pore-cavity filler. ers and reef builders, such as coral and bryozoa Silica in the form of quartz, feldspar, and zeolite reefs (Read, 1985). Packstone and sometimes are preserved from the phreatic meteoric environ- floatstone with large amount of carbonate mud ment after cementation by the orthosparite calcite. matrix is interpreted as reef-flank deposits. This microfacies interpretation can be done to Floatstone each limestone sample petrography tested. The Floatstone is generally massive with coarse- interpretation microfacies result can be used to grained fragmental bioclastic texture, both with trace back the development of facies deposition of closed fabric or opened fabric. Bioclast is made a limestone formation, in this case is the Baturaja up of diverse type, size, and amount of fossil. In- Formation along the Air Rambangnia traverse. traclast or extraclast is sporadically distributed in a few samples, and is composed of coralline, bio- clastic, and argillaceous limestones. Terrigenous Discussion materials are preserved in a limited number and spread out unevenly. Carbonate mud matrix often Based on petrographic data (Table 1), the has changed into microsparite. Cement materials character of each sample can be known and traced are present limitedly within inter and intra particle to order their stratigraphy. The volcanic rocks of pores. Kikim Formation are deposited unconformably on the limestone of Baturaja Formation, while clastic sedimentary rock of Talangakar Formation Microfacies Interpretation is not exposed in this traverse (Sukandi et al., 2006). The lowest part of the Baturaja Formation Wackestone generally has an inversion tex- preceded by grainstone was deposited in the win- ture, i.e. coarse grains stuck in carbonate mud nowed platform carbonates, which is above the matrix, well washed grains, and has various fos- wave base (SMF11-FZ6). This area is very close sils. Such limestone was generally deposited in to the beach characterized by the presence of ar- back reef down-slope (SMF10-FZ7).IJOG Limestone gillaceous material from the transgression phase facies type resides in this deposition environment (Andreeva, 2008), making it into the bay or pond including argillaceous-rich limestone to some (SMF19-FZ8). The depositional environment of packstone. the limestones repeated from very restricted pond In addition to being in the back reef down- and bay (SMF19-FZ8; Figure 9) to back-reef local slope, wackestone may also be formed in very slope (SMF10-FZ7; Figure 10) is due to regres- restricted bays and ponds (SMF19-FZ8). Special sive and transgressive phases. These depositional characteristic of the limestone deposited in this environments are characterized by the presence

30 Limestone Microfacies of Baturaja Formation along Air Rambangnia Traverse, South OKU, South Sumatra (S. Maryanto)

gang

sem lpr

for for

|------| 0,5 mm SM305C |------| 0,5 mm SM316A

Figure 9. Photomicrograph of wackestone (sample code Figure 11. Photomicrograph of packstone/floatstone (sample SM305C) with very fine - grained size, characterizing the code SM316A) with various bioclasts of red algae (gang) SMF19-FZ8 on very restricted bay or pond. and large foraminifera (for) distributed in carbonate mud matrix (lpr), typifies the SMF5-FZ4 reef-flank area.

lpr for por mol for mol lpr

for lpr mol |------| 0,5 mm SM314A |------| 0,5 mm Figure 10. Photomicrograph of wackestone (sample code SM318A SM314A) with bioclasts of mollusks (mol) and large Figure 12. Photomicrograph of packstone (sample code foraminifera (for) distributed in carbonate mud matrix (lpr) SM318A) with various bioclasts of mollusks (mol) and large characterizing the SMF10-FZ7 on back-reef down-slope. foraminifera (for) distributed in carbonate mud matrix (lpr), characterizing the SMF5-FZ4 on reef-flank area. of wackestone-packstone interlayers some parts of argillaceous and with floatstone intercalation. 1982). Furthermore, transgressive phase led to be- Regression process affects sedimentation in come the depositional environment of slopes and the middle part of Baturaja Formation, initiated shelf edges (SMF12-FZ6; Andreeva, 2008; Fig- by floatstone from reef-flank facies (SMF5-FZ4; ure 13) composed of grainstone with graded and Figure 11 and 12). The middle part of the Baturaja planar cross-bedded structures (Bathurst, 1975; Formation is dominated by limestones from that Kendall, 2005). Finally, the lithology sequence depositional environment. The depositional envi- ended by the presence of wackestone-packstone ronment repeated alternation with back-reef local deposited at back-reef local slope (SMF10-FZ7; slope facies (SMF10-FZ7; Wilson, 1975) and their Jones and Desrochers, 1992; Figure 14). lithology composedIJOG of wackestone-packstone. Paleogeographically, the reef complex is The lithology from the back-reef local slope located in the east of the researched area, thus (SMF10-FZ7) continued until the upper part of the highland is being in the west part (Maryanto, the formation, and it was preceded by the presence 2005). The Baturaja limestones were deposited, of wackestone-mudstone. Regressive phase led with the influence of a regional transgression, the depositional environment to evolve into the on the Late Oligocene age. The development of very restricted bay or pond (SMF19-FZ8; Flugel, depositional environment between time forming

31 Indonesian Journal on Geoscience, Vol. 1 No. 1 April 2014: 21-34

bry for lpr lpr

mol mol

mol for ech |------| 0,5 mm SM324B |------| 0,5 mm SM325B Figure 13. Photomicrograph of grainstone (sample code Figure 14. Photomicrograph of packstone (sample code SM324B) with various bioclasts of mollusks (mol), large SM325B) with abraded bioclasts of mollusks (mol), large foraminifera (for), and bryozoans (bry) in carbonate ce- foraminifera (for), and echinoderms (ech) distributed in ment, characterizing the SMF12-FZ6 on slope or shelf carbonate mud matrix, characterizing the SMF10-FZ7 on edge. the back-reef down-slope.

River Tidal Flat UPPER PART 4 INVESTIGATED AREA Tidal Channel Local Basin

Lagoon Bay Slope

Basin N

BASEMENT ROCKS Transgression Back-reef Fore-reef Core-reef Reef-flank

River Tidal Flat MIDDLE PART 3 Tidal Channel INVESTIGATED AREA Local Basin

Lagoon Bay Slope

Basin N

BASEMENT ROCKS Regression

Back-reef Fore-reef Core-reef Reef-flank

River Tidal Flat LOWER PART 2 INVESTIGATED AREA Tidal Channel Local Basin

Lagoon Bay Slope

Basin N

BASEMENT ROCKS Regression Back-reef Fore-reef Core-reef Reef-flank

River BASEMENT ROCKS 1 Calcareous INVESTIGATED AREA Siliciclastics

IJOGLagoon Open Marine Slope

Basin N

BASEMENT ROCKS Stable land Back-reef Fore-reef followed by erosion Core-reef Reef-flank

Figure 15. Depositional environment development of the Baturaja limestones along Air Rambangnia traverse, OKU Selatan, South Sumatra.

32 Limestone Microfacies of Baturaja Formation along Air Rambangnia Traverse, South OKU, South Sumatra (S. Maryanto)

Baturaja Formation is shown in the Figure 15. References Depositional environment of the Baturaja Forma- tion varies from very restricted bay or pond area Andreeva, P., 2008. Microfacies Analysis of (SMF19-FZ8), back-reef local slope (SMF10- Middle Devonian (Eifelian) Carbonate Rocks FZ7), slope and shelf edge (SMF12-FZ6), win- from Deep Wells in North-Eastern Bulgaria nowed platform edge sands (SMF11-FZ6), and (Preliminary Results). Geologie Sedimentolo- reef-flank facies (SMF5-FZ4). In general, the gie, 61 (10), p.1309-1314. depositional environment is conditioned exis- Bathurst, R.G.C., 1975. Carbonate Sediments tence of transgression, characterized by changes and Their Diagenesis, Second Enlarged Edi- in the position of microfacies that increasingly tion. Elsevier Scientific Publishing Company. moved away from bay or pond and going onto New York, Amsterdam, Oxford, 658 pp. the reef-flank facies. Depositional phase was Bishop, M.G., 2000a. South Sumatra Basin still ongoing until the Early Miocene (Maryanto Province, Indonesia: The Lahat/ Talangakar 2007a), which would later be crushed by the Cenozoic Total Petroleum System. Open file Gumai Formation. report 99-50S US Geological Survey. http:// Depositional environment forming the Batura- geology.cr.usgs.gov/energy/WorldEnergy/ ja Formation along Air Rambangnia traverse has OF99-50S/occurrence.html [27/03/2006]. never been the deep sea or the fore-reef area. The Bishop, M.G., 2000b. Petroleum System of the position of the fore-reef area is predicted to be far Northerst Java Province and Offshore South- away to east-southeast from the researched area. east Sumatra, Indonesia. Open file report 99- The research area is located at the volcanic back 50R US Geological Survey. http://geology. arc basin, at the basin edge bordering the land cr.usgs.gov/energy/World Energy/OF99-50R/ area, which at that time was occupied by the Pre- index.html > (13/06/2006). Tertiary rocks, now known as Garba Mountains. Dunham, R.J., 1962. Classification of Carbon- ate Rocks According to Depositional Tex- tures. In: Ham, W.E. (ed.), Classification of Conclusion Carbonate Rocks. American Association of Petroleum Geologists, Memoir 1, p.108-121. Petrographic analysis was carried out upon Embry, A.F. and Klovan, J.E., 1971. A Late De- thirty four limestone samples taken from Air vonian Reef Tract on North-Eastern Banks Rambangnia traverse, OKU Selatan, South Island, North West Territory. Bulletin of Ca- Sumatera. It shows out that limestones consist nadian Petroleum Geology, 19, p. 730-781. of wackestone, packstone, grainstone, and float- Flugel, E., 1982. Microfacies Analysis of Lime- stone. stones. Springer-Verlag. Berlin, Heidelberg, Stratigraphically, each of the rocks studied New York, 633pp. repeatedly occurs, but generally they developed Gafoer, S., Amin, T.C., and Poernomo, J., 1986. in a transgressive depositional environment. The Geological Map of Lahat Quadrangle, Suma- depositional environment is diverse ranging from tra, scale 1 : 250.000. Geological Research restricted bay or pond, back-reef local slope, slope and Development Centre, Bandung. or shelf edge, winnowed platform edge sand, and Gafoer, S., Amin, T.C., and Pardede, R., 1993. reef-flank facies. Geological Map of Baturaja Quadrangle, IJOGSumatra, Scale 1 : 250.000. Geological Re- search and Development Centre, Bandung. Acknowledgements Jones, B. and Desrochers, A., 1992. Shallow Platform Carbonates. In: Walker, R.G. and The author thanks and appreciates Mr. Herwin James, N.P. (eds), Facies Models, Response Syah for drawing digital pictures, and Mr. Heri- to Sea Level Change. Geological Association yanto for photographing thin sections. of Canada Bulletin, p.277 - 301.

33 Indonesian Journal on Geoscience, Vol. 1 No. 1 April 2014: 21-34

Kendall C.G.St.C., 2005. Carbonate Petrol- Lokal Terumbu Belakang Batugamping For- ogy. In: Kendall C.G.St.C. and Alnaji, N.S. masi Baturaja di Daerah sekitar Muaradua, Su- (developers). USC Sequence Stratigra- matera Selatan. Jurnal Sumber Daya Geologi, phy.http://strata.geol.sc.edu/ seqstrat.html 18 (2), p.107-120. [27/02/2006]. Read, J.F., 1985. Carbonate Platform Facies Kindler, P. and Hearty, P.J., 1996. Carbonate Models. American Association of Petroleum Petrography as an Indicator of Climate and Geologists, Bulletin, 69, p.1-21. Sea-Level Changes: New Data from Baha- Sukandi, U., Maryanto, S., Amar, Heriyanto, and mian Quaternary Units. Sedimentologi, 43, Krisnawan, D., 2006. Pengambilan Sampel p.381-399. Batuan untuk Pembuatan Material Acuan Maryanto, S., 2005. Sedimentologi Batuan Kar- Standar Petrologi. Lapor an­ Teknis Intern, bonat Tersier Formasi Baturaja di Lintasan Air Pusat Survei Geologi, Bandung, tidak terbit, Napalan, Baturaja, Sumatera Selatan. Jurnal 228pp. Sumber Daya Geologi, 15, p.83-101. Tucker, M.E. and Wright, V.P., 1990. Carbonate Maryanto, S., 2007a. Keterkaitan Hubungan Sedimentology. Blackwell Scientific Publica- Antar Variabel Microfacies Batugamping tions. Oxford, London, Edinburg, Cambridge, Bioclastic dari Formasi Baturaja di daerah 482pp. Sekitar Muaradua, Sumatra Selatan. Tesis S2 Wilson, J.L. 1975. Carbonate Facies in Geologic Program Pascasarjana Universitas Padjadja- History. Springer-Verlag. New York, Heidel- ran, Bandung, tidak terbit. berg, Berlin, 471pp. Maryanto, S., 2007b. Petrografi dan Proses Dia- Wilson, M.E.J. and Rosen, B.R., 1998. Implica- genesis Batugamping Formasi Baturaja di tions of Paucity of Corals in the Paleogene of Lintasan Air Saka, OKU Selatan, Sumatera SE Asia: Plate Tectonics or Centre of Origin? Selatan. Jurnal Sumber Daya Geologi, 17 In: Hall, R. and Holloway, J.D. (eds.). Bio- (1), p.13-31. geography and Geological Evolution of SE Maryanto, S., 2008. Hubungan Antarkomponen Asia, p.165-195. Microfacies Lereng Terumbu dan Cekungan IJOG

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