Biostratigraphy and Strontium Isotope Dating of Oligocene-Miocene Strata, East Java, Indonesia

Biostratigraphy and strontium isotope dating of Oligocene-Miocene strata, East Java, Indonesia

Essam F. Sharaf 1, 3, Marcelle K. BouDagher-Fadel 2, J. A. (Toni) Simo3, 4, and A. R. Carroll3 1Department of Geology, Faculty of Science, Mansoura University, Mansoura 35516, Egypt email: [email protected] 2Postgraduate Unit of Micropalaeontology of Geological sciences, University College London, Gower Street, London WC1E 6BT, U.K, email: [email protected] 3Department of Geology and Geophysics, UW-Madison, 1215 W. Dayton Street, Madison, WI 53706, USA 4ICREA - Dept. Eng. Terreny, Cartografia y Geofisica, UPC, 08034 Barcelona, Spain

INTRODUCTION The main purposes of this paper are to refine the biostratigraphic framework of Oligocene-Miocene outcrops in East Java The Oligocene and Miocene of the East Java Basin provide an Basin and to calibrate the stratigraphic ranges obtained from the excellent opportunity to examine the comparative responses of identified fossil assemblages with the geochronology of the ex- clastic and carbonate depositional systems to eustatic and tec- posures based on the strontium isotopic compositions of some tonic controls (Bransden and Matthews 1992). In this area, larger benthic forminiferal content. large and isolated carbonate buildups surrounded by deep marine carbonates or shallow- and deep-water siliciclastic rocks. GEOLOGIC AND STRATIGRAPHIC SETTING The variation in facies distributions and faunal assemblages are among the major consequences of the eustatic and tectonic evo- The study area occupies the northern part of the East Java Basin lution of the basin, but their analysis requires improved geo- (text-fig. 1). It is located within the Rembang Zone and the chronology. northern part of Randublatung Zone (Van Bemmelen 1949). The Rembang Zone consists of series of E-W oriented hills with maximum elevation of about 500 m (text-fig. 1). Those hills gener- Larger benthic foraminifera (LBF) are most prolific in warm ally represent anticlines that may or may not be faulted. The shallow water carbonate sediments. On modern reefs, they may Randublatung Zone is to the south (text-fig.1) and represents a phys- constitute up to 15% of the skeletal debris associated with other iographic depression that contains folds such as Pegat and reef builders (Maxwell 1968). Cenozoic LBF are very abundant Ngimbang anticlines (Duyfjes 1938). in Indo-Pacific Ocean, having been described from many localities in Philippines (Carozzi 1976); Japan (Matsumaru 1977); During the Cenozoic, the relative movement of the Indian, Eur- Borneo (BouDagher-Fadel, and Lord 2001; BouDagher-Fadel asian and Australian plates controlled the tectonic setting of the and Wilson 2000) and Indonesia. Many LBF have biotopes EJB. The basin exhibits a complex history of initial extension closely associated with carbonate environments. Their geo- followed by differential basin subsidence and later tectonic in- graphic distribution is controlled by environmental parameters version (Hamilton 1979). During the rifting, Paleogene exten- such as light penetration, nutrient availability, turbidity, water sion defined NE-SW trending horsts and lacustrine grabens depth, water temperature, and salinity (Cole 1957, 1963; (Cole and Crittenden 1997; Hamilton 1979). During the Eocene Renema 2002). In general, most LBF taxa have long strati- to early Oligocene, a marine transgression associated with mod- graphic ranges, but well-established genera are morphologi- erate differential subsidence flooded the area and marine car- cally distinct and have different stratigraphic ranges (see bonates were deposited across the entire region. Isolated BouDagher-Fadel and Banner 1999). The co-occurrence of carbonate mounds (red algae and coral dominated) grew above planktonic foraminifera and LBF in the same section is a rare structural highs. Mound growth continued, with more aerial re- opportunity to refine the biostratigraphic ranges of some of striction, into the Middle Miocene. The mounds were sur- these LBF and to refine the biostratigraphic frameworks based rounded by off-mound facies mostly of marls and chalks with on these two groups. occasional shallow-water carbonate debris derived from the mounds. The Burdigalian-Langhian represents the initiation of The first attempt to use the planktonic foraminiferal biostrati- clastic influx (Bransden and Matthews 1992); clastic deltas graphy in the Indonesian region was made by Bolli (1966), prograded from the north (Koesoemadinata and Pulunggono when he applied his 1957 Trinidad and Tobago zonation to the 1975). The clastic influx initially digitated with carbonate Wonocolo Formation in well Bojonogoro-1 at the southwestern mounds but overwhelmed the entire region in the Serravallian. part of east Java Basin, Indonesia. The planktonic zones intro- During the Late Miocene-Middle Pliocene (˜7 Ma- 3.6 Ma), duced by Blow (1969) and revised by Berggren et al., (1995) northern East Java was affected by contraction forming are used in the zonation scheme of this work and are correlated south-verging faults and en-echelon east-west folds. A final re- with the geologic time scale of Ogg and Smith, (2004). Addi- organization of the basin occurred during the Late Pliocene un- tional previous work on the Neogene planktonic foraminifera in til Recent (˜3.6 Ma- 0 Ma) where the southern area of EJB EJB was published by Muhar (1957) and Brouwer (1966). (Kendeng Zone) was affected by north-verging thrusts and up- stratigraphy, vol. 2, no. 3, pp. xxx-xxx, text-figures x-xx, plates x-x, tables x-x, 2005 1 Essam F. Sharaf et al.: Biostratigraphy and strontium isotope dating of Oligocene-Miocene strata, East Java, Indonesia

TEXT-FIGURE 1 Geologic map of East Java showing the main stratigraphic units, main areas and the localities of Sr isotope samples. lifted. The uplift was accompanied by volcaniclastic influx has been established as latest Early Oligocene (Rupelian, P20) from south to north (Soeparjadi et al. 1975). to Early Miocene (Aquitanian N4) (Najoan 1972; Duyfjes 1941; cited in Lunt et al. 2000). It is subdivided into three, mappeable, Oligocene-Miocene outcrops in the EJB include carbonates, shales sedimentary packages (Indonesian Map 1997). The exposed lower and sandstones that are rich in coralline algae, corals, larger benthic Kujung is represented by reefal carbonates (Darman and Sidi 2000). and planktonic foraminifera. These lithologies and exposures are The exposed middle Kujung is represented by interbedded shale not widely known; there is little previous stratigraphic, sediment- and chalk lithologies rich in planktonic foraminifera. The ex- ologic and biostratigraphic work published of these rocks. Previous posed upper Kujung forms a resistant ridge (Prupuh Ridge, near paleontological studies in this area include Duyfjes (1936 and the Prupuh village text-fig. 1) that exposes interbedded chalky 1938); Van Bemmelen (1949); Muhar (1957); Bolli (1966); carbonates and graded-bedded grainstone with scour surfaces Brouwer (1966); Van Vlerk and Postuma (1967); Pringgo- and load cast features. These lithologies are also known as the prawiro et al. (1977); van Vessem (1978); Ardhana et al. (1993) Prupuh Member carbonates (text-fig. 2). and Lunt et al. (2000). We follow the nomenclature established by Bataafsche Petroleum Maaschappiji, BPM, (1950) and JOB Tuban Formation Pertamina-Tuban (1990) as cited by Ardhana et al. (1993); within each formation we have recognized different lithologies The Tuban Formation is widely exposed along the EJB (text-fig. 2). The Oligocene-Miocene stratigraphic units of in- (text-fig.1) and has been dated as Burdigalian to Langhian terest of this work and exposed in East Java are the Kujung, (Ardhana et al. 1993). The Tuban lithologies are highly vari- Tuban and Ngrayong Formations and the Bulu Member of able. Informally, we have distinguished three main lithologies Wonocolo Formation (text-fig. 3). Briefly, these stratigraphic units (sandstone, carbonates and shale) that alternate in space and are summarized below. time. The Tuban sandstone and carbonate lithologies are well exposed in western Rembang area while the Tuban shale lithologies Kujung Formation are thicker and more abundant in the eastern Rembang area. The The Kujung Formation is the oldest formation exposed in the Tuban sandstone lithology consists of subtidal to intertidal, study area (text-figs. 1 and 2). The age of Kujung Formation bioturbated interbedded sandstone, siltstone and shale beds with

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TEXT-FIGURE 2 Summary of the stratigraphy and the proposed ages for the different stratigraphic units in EJB. larger benthic foraminifera, thin planar corals and mollusk frag- Bulu Member of Wonocolo Formation ments, specially in the upper parts of the section. The Tuban carbon- The Wonocolo Formation in the study area consists of a basal car- ates are well exposed forming an E-W ridge that allowed measuring bonate (Bulu Member) overlain by a thick succession of shale and multiple stratigraphic sections. The Tuban carbonates are highly marl with thin sandstone intervals. The Bulu Member forms a mas- fossiliferous and characterized by massive coral-rich beds, LBF- sive and resistant carbonate bench (10-20m thick). Two main rich bedded shelf strata, and red-algal thick-bedded carbonates. The lithologies are identified: well bedded carbonates rich in large ben- Tuban shale consists of massive, featureless, green shale rich in thic foraminifera and planar corals, and sandy fossiliferous carbon- planktonic foraminifera. The Tuban Formation is interpreted as ates. The Bulu Member truncates the underlying Ngrayong a mixed carbonate-siliciclastic shelf with prograding deltas Formation; throughout the study area, meter-scale channels filled intertonguing with shelfal carbonates and buildups. with conglomerates separates the two formations. The Bulu Mem- ber is Late Serravallian-Early Tortonain in age based on the pres- Ngrayong Formation ence of Cycloclypeus annulatus (Ardhana et al. 1993; Lunt et al. 2000). The Ngrayong Formation is well exposed in quarries and river banks along the Lodan Anticline and Prantakan River (Text-fig.1). The age of Ngrayong stratigraphic unit is Middle Miocene METHODS (Ardhana et al. 1993; Lunt et al. 2000). The exposed Ngrayong Seventeen stratigraphic sections were measured throughout the area. succession is rarely fossiliferous, however, this formation consists at A total of 650 samples were collected from these sections, and 250 the base of argillaceous fine sand and shale that grades upward into samples were collected from isolated sites. interbedded fine to medium sand with thin mudstones layers and coal seams. The top of the formation consists of coarse and friable The paleontological contribution to this study includes the identifi- sandstone. The Ngrayong Formation is interpreted as prograding cation of larger benthic foraminifera (LBF) and planktonic tidal delta. foraminifera. The study of LBF is based on the study of 250 thin

3 Essam F. Sharaf et al.: Biostratigraphy and strontium isotope dating of Oligocene-Miocene strata, East Java, Indonesia

TEXT-FIGURE 3 Idealized stratigraphic framework of the different rock units in East Java Basin, Indonesia.

sections of carbonate samples from the Prantakan, Mahindu, and Selected LBF were micro-drilled for strontium isotope analysis. Prupuh areas. As the specimens studied here are from random Primary LBF shell materials were carefully selected. Extra steps thin sections of limestones, biometric measurements on iso- were performed to insure mineralogical homogeneity of each lated, solid specimens of larger foraminifera have rarely been sample including: elimination of the diagenetically deformed possible. We attempt to combine the broad results gained by forms and matrix, staining of the thin sections of the selected equatorial sections of the megalospheric nepiont of the carbonate samples with Alizarin Red S and potassium ferri- Miogypsinidae (as published by Drooger 1993) with those ob- cyanide to check their carbonate mineralogy and running quali- tained by vertical sections of the whole test (following Tan Sin tative x-ray analysis of picked foraminifera from a few shale Hok 1936, 1937). Similarly, we combine equatorial sections of samples selected for the strontium dating. Approximately 10 mg the megalospheric nepiont of the lepidocyclinids (as published of the powdered samples were dissolved in 1mL 1M ultra pure by Chaproniere 1984; Van Vessem 1978) with those obtained acetic acid. (See Asahara et al. 1995; Quade et al. 1995; Singh et by vertical sections of the whole test (as made by Cole 1957, al. 1998 for further discussion on acid leaching techniques.) The 1963). samples were then dried down in 1mL 8M hydrochloric acid in preparation for ion-exchange chromatography. Mass analysis The study of planktonic foraminifera was done either in thin sec- was completed on a thermal-ionization mass spectrometer at the tions or from washed residues. The washed residues were obtained University of Wisconsin – Madison, using a multi-collector by separating the foraminifera from 10 shale and soft chalk samples. analysis with exponential normalization to 86Sr/88Sr = 0.1194. The samples were soaked in a solution of 10% hydrogen peroxide The 87Sr/ 86Sr ratios obtained were dated numerically using (H2O2) and sodium hexametaphosphate (Na6(PO3)6, Calgon) for the standard tables of McArthur et al. (2001) based on the sea 24 hours and then the insoluble residue wet sieved with water using water Sr-isotope curve of the Tertiary listed in McArthur et al. 63 micron sieve and checked for the fossil content. The planktonic (2001) and Hodell et al. (1999) and the geologic time scale of foraminifera were examined under the binocular microscope. Gradstein, Ogg and Smith (2004). During the data collection for

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TEXT-FIGURE 4 Correlation between larger benthic foraminiferal assemblages identified from East Java and their stratigraphic ranges.

this study, 4 analyses of NBS-987 yielded 87Sr/86Sr values of classification was introduced by Van der Vlerk and Umbgrove 0.710269 +/-0.000015 (2-standard deviations) n=406 for NIST (1927). Later, this classification was revised and improved by SRM-987 and 0.709192 +/-0.000013 (2-standard deviations) Leupold and Van der Vlerk (1931); Van der Vlerk (1955), Adams n=7 for EN- 1. The curves for age calculation assume 0.710248 (1970), BouDagher-Fadel and Banner (1999). Based on previous for NIST SRM-987 and 0.709175 for EN-1. To correct the work we have constructed a chart, at species level, of key LBF interlaboratory bias and make the strontium data agree with from the studied area (text-fig. 4). This figure shows that some McArthur et al. (2001), the 87Sr/86Sr ratios were multiplied by LBF have long stratigraphic ranges or their first and last appear- 0.9999725 which yielded corrected ratios of 0.710249 for the ances are uncertain and thus are poor index fossils, while others NIST SRM-987 standard and 0.709172 for EN-1. have well-defined and shorter ranges and are good index fossils. LBF and other long-range benthic foraminifera such as operculinids, BIOSTRATIGRAPHY amphisteginids, miliolids, textularids and lagenids are very abundant in the EJB. Plates 1-4 show some of the main LBF identified in this The first biostratigraphic study of the Neogene of Indonesia was re- study. As described below, LBF assemblages of the outcrops show ported by Martin (1880; cited by Brouwer 1925) using the “Mollusk lateral variation in abundance from one locality to the other support- stratigraphy” method. This method was based on the Linnaean ra- ing the concept of being facies (environmental) dependant (Van der tios of extant to extinct mollusk fauna to estimate the relative ages. Vlerk 1955; Hallock and Schlager 1986). However, this method had numerous shortcomings (Brouwer 1925) and failed to correlate between mollusk species in East Indian Ocean and the species in Europe. Since the 1920s, the larger benthic Despite the abundance of planktonic foraminifera in EJB, few foraminifera have become the most important biostratigraphic index species were described from the shale and chalk samples method for age determination in the Indo-Pacific region for their due to the lack of well preserved samples, with few exceptions large diversity and regional distribution. The Tertiary Letter Stage of the chalky beds of Prupuh Ridge and the top of the Prantakan

5 Essam F. Sharaf et al.: Biostratigraphy and strontium isotope dating of Oligocene-Miocene strata, East Java, Indonesia

River and Mahindu outcrop, where the beds are rich in planktonic L.), in which the protoconch and deuteroconch are of nearly assemblage of long geologic range such as Globigerina woodi, equal size and separated by a straight wall (this has been called Globigerinoides sacculifer, Orbulina sp. and Orbulina suturalis. “isolepidine”), and the essentially Miocene Lepidocyclina Plate 5 shows some of the main identified planktonic foraminifera (Nephrolepidina) where the smaller proloculus is followed by a from the studied area. much larger, reniform deuteroconch. The latter forms develop quadrate proloculi in the later stages of many lineages. The Upper Oligocene, Lower Kujung, LBF assemblage is dominated by Spiroclypeus sp., Heterostegina borneensis, Lepido- Family LEPIDOCYCLINIDAE Scheffen 1932 cyclina (Eulepidina) favosa, L. (E.) richthofeni, L. formosa, Subfamily LEPIDOCYCLININAE Scheffen 1932 Lepidocyclina banneri, Lepidocyclina sp., Miogypsinoides sp., Subfamily Lepidocyclininae SCHEFFEN 1932 Miogypsinella boninensis (Plate 1) and the index planktonic Genus LEPIDOCYCLINA Gümbel 1870 emend. Boudagher- foraminifera Globigerina ciperoensis described from a shale sam- Fadel and Banner 1997 ple near Dandu village, eastern Rembang area (text-fig. 1). Lepidocyclina banneri BouDagher-Fadel, Noad and Lord 2000 The Upper Oligocene-Lower Miocene (Chattian-Aquitanian, Plate 1, figure 3 P22-N4, equivalent to Te1-4-Te5), Upper Kujung, is characterized by an assemblage dominated by Lepidocyclina (Eulepidina) Lepidocyclina banneri BOUDAGHER-FADEL, NOAD, LORD 2000, formosa, L. (E) favosa, L. (N.) parva, L. (N.) morgani, L. (N.) p. 348, pl. 1, figs. 5-6. verbeeki, Lepidocyclina (Nephrolepidina) sumatrensis, Mio- gypsina sabahensis, Miogypsinoides dehaarti, Spiroclypeus sp. Dimensions: Maximum measured length 4mm. and Flosculinella sp. (pl. 1). The chalk beds are characterized Remarks: This species is characterized by its possession of mas- by a planktonic assemblage of Globoquadrina dehiscens (pl. 5, sive pillars in the centrum of the strongly biconvex test. Much nar- fig. 1), Globigerinoides quadrilobatus (pl. 5, fig. 2) and rower hyaline pillars are scattered over the whole of the lateral Globigerinoides trilobus (pl. 5, fig. 3). Two shale samples col- sides of the test. L. banneri is broadly biconvex in form in compar- lected along Prupuh Ridge are rich in Globorotalia kugleri and ison with L. delicata (Pl.3, fig.4). Globigerinoides primordius.

The Burdigalian-Langhian (N5-N9, equivalent to upper Te5-Tf1), Distribution: This species was originally described from the Tuban sandy carbonate beds are defined by Lepidocyclina Gomantong Limestone from the Upper Te, Aquitanian- (Eulepidina) formosa and Miogypsina (Miogypsina) tani. The Burdigalian of northwest Borneo. In this study it is found in the Tuban carbonates are highly fossiliferous at the Prantakan area Upper Chattian of the Lower Kujung Formation in East Java, (text-fig. 1). The association at this area consists of Austro- Kujung area Sample (6.3.3, 2001). trillina howchini, Lepidocyclina (Nephrolepidina) ferreroi, L. (N.) Lepidocyclina delicata Scheffen 1932 martini, Lepidocyclina (E.)sp., L. delicata, L. (N.) stratifera, L. Plate3, figure 4 (N.) inflata, L. (N.) angulosa, L. (N.) brouweri, L (N.) tournoueri, L. (N.) irregularis, L. (N.) kathiawarensis, Miogypsina digitata, Lepidocyclina delicata SCHEFFEN 1932, p. 18, pl. 1, fig. 4. – Katacycloclypeus annulatus (pls. 2 and 3) . To the east, Mahindu BOUDAGHER-FADEL and WILSON 2000, p. 153, pl. 1, fig. 5. – area (text-fig. 1), the dominant LBF’s are Lepidocyclina (N.) BOUDAGHER-FADEL et al. 2000b, p. 348, pl. 1, figs. 7-8. verbeeki, Miogypsina sp., Miogypsinoides sp., and Katacyclo- Dimensions: Maximum measured length 20mm. clypeus annulatus. And farther to the west (Dermawu village, text-fig.1) the association consists of Lepidocyclina (Nephro- Remarks: Lepidocyclina delicata is characterised by the dark, lepidina) verrucosa, L. (N.) ferreroi, L. (N.) sumatrensis and very finely, microgranular pillars which are restricted to the in- Katacycloclypeus annulatus. The bed on top of the Tuban car- ner lateral layers of the centrum only. Beyond these pillars, bonates (Mahindu area) contains the planktonic foraminifers hyaline, glossy radial pillars are to be found radiating from the Globorotalia praemenardii, Orbulina sp. and O. suturalis (pl. inner layers of the centrum to the outer surface. 5, fig. 6) Distribution: L. delicata Scheffen ranges from middle Tf1 to The Late Serravallian assemblage (N12 and younger, equivalent to Tf2 (Langhian to early Serravallian). It was first described from stage Tf2), Bulu, is characterized by dominance of Katacyclo- Java, Indonesia. BouDagher-Fadel et al. (2000b) record the oc- clypeus annulatus, Lepidocyclina (N.) ngampelensis (pl. 4), currence of L. delicata in the Tf2 of the Darai Limestone in cen- Orbulina sp. and Orbulina suturalis (pl. 5, fig. 6). tral south Papua-New Guinea. It has been found in Kalimantan In this paper, we systematically describe significant benthic with Katacycloclypeus in the early Serravallian (Tf2) by larger foraminifera. We only listed the occurrences of the BouDagher-Fadel and Wilson (2000) and from the Tf2 planktonic foraminifera. (Serravallian) of Sadeng section (SAD) in the Gunung Sewu area of South Central Java by (BouDagher-Fadel et al. 200B). In this study, it was found in the Tf1 “letter stage” of Late Burdigalian SYSTEMATIC DESCRIPTIONS to Langhian age of East Java, Gabalan outcrop, Rembang west, The usage of the subgeneric names Lepidocyclina (Lepidocyclina) Sample # 1. and Lepidocyclina (Nephrolepidina), with the use of Lepido- cyclina s.l. for microspheric forms, follow the system proposed by Lepidocyclina stratifera Tan Sin Hok 1935 BouDagher-Fadel and Banner (1997). The nomenclatural revi- Plate 2, figure 1B sion of BouDagher-Fadel and Banner (1997) makes the genus Lepidocyclina stratifera TAN SIN HOK 1935, p.9, pl. 1(4), figs. 1-3, Lepidocyclina sensu lato available for the naming of pl.2(5), fig.11, pl.3(6), fig.9, pl. 4(7), fig.1, pl. 1, fig. 1. microspheric forms, but the megalospheric forms are divisible Lepidocyclina (Nephrolepidina) stratifera Tan Sin Hok. – BARBERI et into the essentially Palaeogene Lepidocyclina (Lepidocyclina al. 1987, pl. 4, figs. 4,11. – BOUDAGHER-FADEL and WILSON

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TABLE 1 Strontium isotope analyses of selected samples in EJB, illustrated by decimal latitude and longitude coordinates, and their corresponding ages. The 87Sr/86Sr ratios were normalized by multiplication by 0.9999725 which yielded corrected ratios of 0.710249 for the NIST SRM-987 standard and 0.709172 for EN-1.

2000, p. 154, pl. 1, fig. 3, pl.2, fig. 6. – BOUDAGHER-FADEL 2002, Lepidocyclina formosa SCHLUMBERGER 1902, p. 251, pl. 7, figs. 1-3. p. 164, pl. 3, fig. 10. Dimensions: Maximum measured length 5mm. Maximum measured length 4mm. Remarks: Lepidocyclina (Eulepidina) Formosa is characterized Remarks: L. stratifera has a biconvex test with many layers of by the four angles of the test prolonged into tapering rays. low cubiculae in which their platforms are as thick as or thicker than the cubicular lumena. Club-shaped hyaline pillars are de- Distribution: This species was originally described from the veloped from the outer periphery of the centrum to the surface Miocene of Borneo. In this study it is found in the Lower Mio- of the test. cene deposits (Upper Te/Te5) of East Java. Sample 8.1.3.

Distribution: L. stratifera was first described from Java, Indo- Subgenus Nephrolepidina H. Douvillé 1911 emend. Bou- nesia being found together with Miogypsina, Katacycloclypeus Dagher-Fadel and Banner 1997 and Trybliolepidina, an assemblage characteristic of middle Serravallian, Tf2 (see BouDagher-Fadel and Banner 1999). Lepidocyclina (Nephrolepidina) ferreroi Provale 1909 Barberi et al. (1987) reported L. stratifera from the Tf1 Plate 3, figure 1B, Plate 4, figure 2 (Burdigalian-Serravallian) of the carbonate sequence of the Is- Lepidocyclina ferreroi PROVALE 1909, p.70, pl.2, figs 7-13. land of Sumbawa, Indonesia. It was described by BouDagher- Lepidocyclina (Nephrolepidina) ferreroi Provale. – BOUDAGHER- Fadel and Wilson (2000) in the Tf1 of late Burdigalian to FADEL and LORD 2000, pl.2, figs 2-9. Langhian age, of eastern Borneo, Kalimantan. BouDagher- Fadel (2002) recorded similar forms from the Tf1 (Upper Dimensions: Maximum measured length 3.6mm. Burdigalian) and Tf2 (Serravallian) of the Gunung Sewu area of South Central Java. In this study it was found in the Tf1 “letter Remarks: The species is characterized in having a quadrate stage” of Late Burdigalian to Langhian age of East Java, protoconch, a quadrilateral test, depressed medially but with a Prantakan area, Sample (12.2.18, 2001). median layer which has 4 high, pillared, lateral lobes and high, numerous cubiculae with relatively thin walls and. Subgenus Eulepidina H. Douvillé 1911 [EDITOR'S QUERY: Distribution: Lepidocyclina (Nephrolepidina) ferreroi with a quadrate protoconch were found in the Burdigalian-Langhian of Please supply systematics (remarks, synonymy, etc.) for the fol- south east Kalimantan (pl.2, figs. 7, 8). In this study it is found lowing three taxa. in the Tf1 “letter stage” of Late Burdigalian to Langhian age of East Java. West Rembang, Mahindu area, (GPS 115, 2002). Lepidocyclina (Eulepidina) favosa (Cushman) Plate 1, figure 8 Lepidocyclina (Nephrolepidina) kathiawarensis Chatterji 1961 Plate 2, figure 1A Lepidocyclina (Nephrolepidina) tourneri Lemoine and Deville Lepidocyclina (Nephrolepidina) kathiawarensis CHATTERJI 1961, p. Plate 2, figure 4 429, pl. 2, fig. 9.

Miogypsina spiralis Dimensions: Maximum measured length 4mm. Plate 2, figure 6 Remarks: This species is characterized by having a bilocular End Query, resume proof text] embryonic apparatus typical of a tryliolepidine type.

Lepidocyclina (Eulepidina) formosa (Schlumberger) Distribution: This species was first described from the Upper Plate 3, figure 2 Burdigalian of western India. In this study it was found in the

7 Essam F. Sharaf et al.: Biostratigraphy and strontium isotope dating of Oligocene-Miocene strata, East Java, Indonesia

Tf1 “letter stage” of Late Burdigalian to Langhian age of East cene-Miocene of Australia, while those of BouDagher-Fadel Java. Sample 12.2.18. and Wilson (2000) were from the Tf1, upper Burdigalian to Langhian, of eastern Borneo, Kalimantan. The figured speci- Lepidocyclina (Nephrolepidina.) ngampelensis Gerth in Caudri mens of BouDagher-Fadel et al. (2000b) were from the Goman- 1939 tong Limestone, upper Upper Te, Burdigalian, of north Borneo. Plate 6, figure 5 BouDagher-Fadel et al. (200B) recorded L. (N.) sumatrensis Lepidocyclina (Nephrolepidina) ngampelensis GERTH, in CAUDRI from the Tf1 (Upper Burdigalian) and Tf2 (Serravallian) of 1939, p. 159, pl. 1, figs. 3-4. Rongkop section (SAD) in the Gunung Sewu area of South Cen- tral Java. In this study it is found in the Tf1 “letter stage” of Late Dimensions: Maximum measured length 5mm. Burdigalian to Langhian age of East Java. Sample (GPS 115, 2002), East Dermawu, Sample 15, and Prantakan area, Sample Remarks: This species is characterized by very low, thick (4.3.1, 2001). floored cubiculae, with strong pillars scattered along the centre of the test. Lepidocyclina (Nephrolepidina) verrucosa Scheffen 1932 Plate 4, figure 4 Distribution: This species was found in the “Tertiary” of Java. Similar forms occur in the Serravallian (Tf2) of the Darai Lime- Lepidocyclina verrucosa SCHEFFEN 1932, p. 33, pl. 7, figs. 2-4, p. 13, text-fig. 4. – BOUDAGHER-FADEL and WILSON 2000, p. 156, pl. stone in central south Papua-New Guinea (BouDagher-Fadel et 2, figs. 7-8. al., in preparation). Our specimens were found in the Serravallian (Tf2) of East Java. Prantakan River Sample (2.3). Dimensions: Maximum measured length 3.5mm. Lepidocyclina (Nephrolepidina) sumatrensis (Brady 1875) Remarks: This species is characterized by possessing pairs of Plate 3, figure 3c, 6; plate 4, figure 4A pillars radiating from about the fifth layer of cubiculae to the Orbitoides sumatrensis BRADY 1875 p. 536, pl. 14, fig. 3a-c. surface, the pillars diverging at an angle of about 60°. Lepidocyclina (Nephrolepidina) sumatrensis (Brady). – COLE 1957, p. 343, pl. 104, figs. 1-9, pl. 105, fig. 18, pl. 106, fig. 5, pl. 109, figs. 1-3.– Distribution: L. (N.) verrucosa was first described from Tf2 of CHAPRONIERE 1983, p. 41, pl. 3, figs. 11, 12, pl. 5, figs. 9-12, pl. 6, Java. BouDagher-Fadel and Wilson (2000) found similar forms figs. 1-10. – CHAPRONIERE 1984, p. 66, pl. 10, figs. a-c, pl. 22, fig. 14, pl. 23, figs. 1-7, pl. 26, figs. 15, 16, fig.21. – BARBERI et al. 1987, in the Tf1 “letter stage”, upper Burdigalian to Langhian, of east- pl. 5, fig. 3, pl. 6, fig. 4. – BOUDAGHER-FADEL and WILSON ern Borneo, Kalimantan and of the Tf1 of the Darai Limestone 2000, p. 156, pl. 2, fig. 4. – BOUDAGHER-FADEL et al. 2000b, p. in Papua. In this study it is found in the Tf1 “letter stage” of Late 352, pl.3, fig.2. Burdigalian to Langhian age of East Java. East Dermawu outcrop, (Sample #15). Dimensions: Maximum measured length 5mm.

Remarks: This species is characterized by a strongly biconvex Superfamily NUMMULITACEA de Blainville 1827 species with a narrow equatorial flange and with many small, Family CYCLOCLYPIDAE BouDagher-Fadel. 2002 narrow pillars. Genus KATACYCLOCLYPEUS Tan Sin Hok 1932

Distribution: Brady (1857) described L.(N.) sumatrensis from Katacycloclypeus annulatus (Martin 1880) the “Early Tertiary” of Nias Island, west coast of Sumatra. Cole Plate 1, figure 6; plate 2, figure 4; plate 4, figures 1, 6 (1957) obtained his specimens from the Upper Te “Letter Cycloclypeus annulatus MARTIN 1880, p. 157, pl. 28, figs. 1a-1i. – Stage” of Saipan, Chaproniere (1983, 1984) from the Oligo- DOUVILLÉ 1916, p. 30, pl. 6, figs. 2,3 [not pl. 5, fig. 6, pl. 6, figs. 1-4).

PLATE 1 Thin section photomicrographs of Late Oligocene-Early Miocene larger benthic foraminifera

1 Miogypsinella boninensis Matsumaru 1996. Equato- 4 Miogypsina sabahensis BouDagher-Fadel, Lord and rial slice of a megalospheric section. Sample 10.1.5. Banner. Axial section showing the stacks of cubiculae Dandu village, Kujung anticline. ×200. separated by massive pillars. Sample P1.69. ×100. 2, 5 Miogypsinoides dehaarti (Van Der Vlerk). A) vertical 6 Spiroclypeus sp. Axial section. Sample # 42.8 Prupuh axial section through the proloculus showing the solid section, ×50. lateral walls. B) equatorial section showing the proloculus surrounded by a whorl of embryonic 7 Lepidocyclina (Eulepidina) favosa (Cushman). Axial chambers. 2. Sample 6.3.3; Dandu village, Kujung section. Sample # 24.3, Prupuh section, ×50. anticline, sample # 69, Prupuh section. ×50. 8 Lepidocyclina (Eulepidina) formosa (Schlumberger). 3 Lepidocyclina banneri BouDagher-Fadel, Noad and Sample 8.1.3. Lord. Axial section showing massive pillars in the cenrum. Sample 6.3.3. ×100.

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9 Essam F. Sharaf et al.: Biostratigraphy and strontium isotope dating of Oligocene-Miocene strata, East Java, Indonesia

Cycloclypeus (Katacycloclypeus) annulatus Martin - COLE 1963, p.E19, Distribution: This form was first described from the Upper pl. 6, fig. 13, 14; pl. 7, fig. 7, pl. 8, figs. 4-6, 8-11, pl. 9, figs. 14, 17. Oligocene of Japan. In this study, similar forms occur in the Upper Katacycloclypeus annulatus (Martin). – BOUDAGHER-FADEL and WILSON 2000, p. 157, pl. 3, fig. 8, pl. 4, fig. 2. – BOUDAGHER- Oligocene, Lower Te, of North East Borneo (BouDagher-Fadel, FADEL 2002, p. 168, pl. 3, fig. 1. Lord and Banner 2000). This species is here found in the Upper Oligocene, Lower Te of East Java, Kujung area, Sample (10.1.5, Dimensions: Maximummeasuredlengthupto6mm(evenona 2001). broken specimen) Genus MIOGYPSINOIDES Yabe and Hanzawa 1928 Remarks: This species is characterized by having a large, thin Miogypsinoides dehaarti (Van Der Vlerk 1924) test with a central umbo surrounded by several widely spaced Plate1, figure 2, 5 annular inflations of the solid lateral walls. Miogypsina dehaarti Van Der Vlerk 1924, p. 429-431, text-fig. 1-3. Distribution: K. annulatus was first described from the Early Mio- Miogypsinoides dehaarti (Van Der Vlerk). – COLE 1957, p. 339, pl. 111, figs. 5-16. – VAN DER VLERK 1966, pl. 1, figs. 1-6, pl. 2, figs. 1-3. cene of West Java, Indonesia. Cole (1963) reported it from the Miogypsina (Miogypsinoides) dehaarti Van Der Vlerk. – RAJU 1974, p. Tertiary of Guam and Fiji. Similar forms were found in the 80, pl. 1, figs. 19-25; pl. 3, fig. 8; pl. 4, figs. 2-4. – BOUDAGHER- Serravallian, Tf2, of eastern Sabah and the Darai Limestone of FADEL, LORD and BANNER 2000c, p. 145, pl. 2, fig. 5. Papua New Guinea (BouDagher-Fadel et al., in preparation) while those of BouDagher-Fadel, and Wilson (2000) came from Dimensions: Maximum measured length 1.5mm. the lower Mid Miocene, Tf2 (early Serravallian) of Kalimantan. BouDagher-Fadel (2002) recorded this form the Lower Mio- Remarks: M. dehaarti is characterized by having very thick lateral cene of the Tacipi Formation, Indonesia. In this study similar walls and being smooth exteriorly, sometimes with slightly raised forms occurred in the Tf2 (Lower Serravallian) of East Java, dark pillars of finely granular structure. Prantakan outcrop (sample PR.2), Prantakan River, Sample Distribution: This species was first described from the Lower (4.3.1, 2001) and Mahnidu area, Sample (9.1.2, 2001). Miocene of Larat, Netherlands East Indies. An equatorial section of an ideotype was photographed by Van Der Vlerk (1966, Family MIOGYPSINIDAE Vaughan 1929 pl.2, fig.1). RAJU (1974) registered the occurrence of this spe- Genus MIOGYPSINELLA Hanzawa 1940 cies in the Indopacific and Mediterranean regions. BouDagher-Fadel et al. (2000c) found similar forms in the Up- Miogypsinella boninensis Matsumaru 1996 per Te, Aquitanian-Burdigalian, of North East Borneo, and is Plate1, figure 1 known in Papua New Guinea to range up into Tf1 (Early Miogypsinella boninensis MATSUMARU 1996, p.50, pl.5, figs 1-7; pl.6, Langhian). This species is here found in the Lower Miocene of figs 1-12; pl.7, figs 1-16; Fig.23-4. – BOUDAGHER-FADEL, LORD East Java, Lower Aquitanian (Lower Te5). Prupuh outcrop and BANNER 2000, p.144, pl.2, figs 1,2,4. Sample 1.69.

Dimensions: Maximum measured length 1mm. Genus MIOGYPSINA Sacco 1893

Remarks: M. boninensis is characterised by having a biconvex test Miogypsina digitata Tan Sin Hok 1937 with several umbilical plug-pillars. The embryonic chambers near Plate 3, figure 3A the apex are followed by nepionic chambers disposed in a trochoid Miogypsina (Miogypsina) kotôi Hanzawa forma digitata TAN SIN HOK spire. 1937, p. 101, pl. 2, figs. 1-5, fig. 1a.

PLATE 2 Thin section photomicrographs of Early-Middle Miocene (Burdigalian-Langhian) larger benthic foraminifera

1A)Lepidocyclina (Nephrolepidina) kathiawarensis stratifera Tan Sin Hok. Sample 12.3.18. Prantakan Chatterji, oblique equatorial section showing a section. ×50. quadrate protoconch strongly embraced by a deuteroconch. Pillars are present only towards the pe- 4 Lepidocyclina (Nephrolepidina) tourneri (Lemoine riphery in our specimens, however towards both ends and Douvillé). Sample # 2, Prantakan section. ×150. of the test. B) Lepidocyclina stratifera Tan Sin Hok. 5 Miogypsina kotoi Hanzawa. Vertical axial section. Sample 12.3.18. Prantakan section. ×100. Sample 4.3.1. Prantakan River area. ×50 2 Lepidocyclina stratifera Tan Sin Hok. Sample 6 Miogypsina spiralis Rutten. Axial section showing a 12.3.18. Prantakan section ×50. large embryonic structure. Sample 11.2. 11. Mahindu 3A)Lepidocyclina (Nephrolepidina) verrucosa area. ×50. (Scheffen). A) An axial section showing pillars diverging at an angle of about 60o.B)Lepidocyclina

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stratigraphy, vol. 2, no. 3, 2005 11 Essam F. Sharaf et al.: Biostratigraphy and strontium isotope dating of Oligocene-Miocene strata, East Java, Indonesia

Miogypsina digitata Tan Sin Hok. – BOUDAGHER-FADEL, LORD Distribution: M. sabahensis was first described from the Upper and BANNER 2000c, p.146, pl.3, fig.7. Te of Burdigalian age of eastern Sabah and in the Tf1 (of Burdigalian-Langhian age) of Kalimantan, both in North East Dimensions: Maximum measured length 1mm. Borneo (BouDagher-Fadel et al. 2000c). This species is found Remarks: This form is characterized by having oval median cham- here in the Lower Miocene of East Java, Te5. Prupuh outcrop, bers and numerous fine pillars. Sample 1.69. Distribution: It was found by BouDagher-Fadel et al. (2000c) in Miogypsina tani Drooger,1952 the early Burdigalian, upper Te, of North East Borneo. In this Plate 3, figure 1B study it is found in the Tf1 “letter stage” of Late Burdigalian of Miogypsina (Miogypsina) tani Drooger 1952, p. 26, 51, 52, pl. 2, figs. East Java. Sample 4.3.1. 20-24. – RAJU 1974, p. 82, pl. 1, figs. 26-30; pl. 5, fig. 5. – WILDENBORG 1991, p. 113, pl. 4, figs. 1, 2, tabs. 19, I. – Miogypsina kotoi Hanzawa 1931 BOUDAGHER-FADEL, LORD and BANNER 2000c, p.147, pl.3, Plate 2, figure 5, plate 3, figure 3B figs 4-6.

Miogypsina kotoi HANZAWA 1931, p.154, pl.25, figs 14-18. – Dimensions: Maximum measured length 3mm. BOUDAGHER-FADEL and WILSON 2000, p.157, pl.3, figs 1-2.

Dimensions: Maximum measured length 2.5 mm. Remarks: This species is distinguished by having a long megalospheric nepionic coil of auxiliary chambers, low cubiculae Remarks: This species is distinguished in having oval median with inflated roofs and many scattered pillars. chambers, small thick-walled, but strongly convex cubicula; it has a biserial nepiont which is strongly asymmetrical. Distribution: This species was first described from the so called “Middle Oligocene” of east-central Costa Rica. It was also found Distribution: Miogypsina kotoi was first described from the in the Aquitanian stage, Upper Te, of Italy and southern Spain Burdigalian of Japan. BouDagher-Fadel and Wilson (2000) re- (Raju 1974). It has a wide distribution in the American, Mediterra- ported it from the Tf1 late Burdigalian to Langhian, of eastern nean and Indopacific regions. Similar specimens were found by Borneo, Kalimantan. BouDagher-Fadel and Lokier (in press) re- BouDagher-Fadel et al. (2000c) in the upper Upper Te, corded similar forms from the Tf1 (Upper Burdigalian) and Tf2 Burdigalian, of Borneo. In this study it is found in the Lower Tf1 (Serravallian) of Djatirago (TAN) the Gunung Sewu area of “letter stage” of Late Burdigalian of East Java. West Rembang, South Central Java. In this study it is found in the Tf1 “letter Mahindu area, sample (GPS 115, 2002). stage” of Late Burdigalian to Langhian age of East Java. Prantakan River, Sample (4.3.1, 2001). STRONTIUM ISOTOPE CHRONOSTRATIGRAPHY Miogypsina sabahensis BouDagher-Fadel, Lord and Banner 2000 Strontium isotope chronostratigraphy was used to calibrate the Plate1, figure 4 numerical ages of the exposed Oligocene-Miocene outcrops in EJB. Because the ranges of most LBF are relatively long and Miogypsina sabahensis BOUDAGHER-FADEL, LORD and BANNER 2000c, p. 147, pl.3, figs 4-6. their abundance is a facies dependant, strontium isotope ratios were used to help correlate the stratigraphic horizons. Table 1 Dimensions: Maximum measured length 1.6mm. and Text-figures 2 and 3 summarize the proposed ages for each stratigraphic unit throughout the studied area. The GPS loca- Remarks: This species is characterized by having massive and tions of the studied samples are converted to decimal latitude heavy pillars when seen in vertical section. and longitude co-ordinates and plotted on Table 1.

PLATE 3 Thin section photomicrographs of Early-Middle Miocene (Burdigalian-Langhian) larger benthic foraminifera

1 Thin section photomicrograph of larger benthic 4 Lepidocyclina delicata Scheffen, A) subequatorial foraminifera assemblage A). Lepidocyclina sp., B) section showing a subcircular equatorial periphery Miogypsina tani Drooger. C) Lepidocyclina (Nephro- and broadly hexagonal median chamberlets. Gabalan lepidina) ferreroi Provale. D) Axial and equatorial section. Sample #1. ×100. sections of Cycloclypeus sp. Sample GPS #115, Mahindu area. ×50. 5 A) vertical axial section. Lepidocyclina (Nephro- lepidina) subradiata (Douvillé). B) Miogypsina tani 2 Thin section photomicrograph of A) Miogypsina Drooger. ×50. digitata Drooger. B) Miogypsina kotoi Hanzawa. C) Lepidocyclina (Nephrolepidina) sumatrensis 6 A) Lepidocyclina (Nephrolepidina) sumatrensis (Brady). Sample 4.3.1. Prantakan River. ×50. (Brady). B) Lepidocyclina (Nephrolepidina) verrucosa (Scheffen). East Dermawu section. Sample #15. 3 Lepidocyclina (Nephrolepidina) sumatrensis ×50. (Brady). Axial section. GPS 115, Mahindu area. ×50.

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stratigraphy, vol. 2, no. 3, 2005 13 Essam F. Sharaf et al.: Biostratigraphy and strontium isotope dating of Oligocene-Miocene strata, East Java, Indonesia

Strontium isotope data from the lower Kujung Formation, the oldest (Nephrolepidina) ngampelensis, Orbulina sp. and Orbulina strata exposed in the EJB (Table 1), provide an age range of 28.78+ suturalis that are dominant at this stratigraphic unit. 0.74 to 28.20+ 0.74 Ma corresponding to Early to Late Oligocene, latest Rupellian- earliest Chattian respectively, (P21), and it is con- DISCUSSION sistent with the presence of Heterostegina borneensis, Lepido- Oligocene-Miocene sedimentary deposits of EJB are dominated cyclina banneri, L. sp., L. formosa., Miogypsinoides sp., and by warm water, shallow marine carbonates that are of crucial Miogypsinella boninensis. importance as the product and record of climatic/oceanic condi- tions and interchange in tropical/subtropical inner-outer shelf The index planktonic foraminifera Globigerina ciperoensis from environments. These deposits are dominantly biogenic in ori- the middle Kujung shale/chalk indicates correlation with Zone of gin, primarily of larger foraminfera and algae, with hermatypic P22 for this interval. Strontium isotope dating of two samples from corals. Fluctuations in climate or oceanic currents have influ- the upper Kujung (Sukowati village and west of Dandu village, enced the geographic distribution of the LBF, during this period Table 1) give ages of 23.44+ 0.74 and 24.31+ 0.74 (Late and abundance of LBF in the EJB appears to be facies dependant. In Oligocene), correlating with Zone (P22-N4). For this interval, the East Java Basin LBF and planktonic foraminifera overlap in oc- benthic foraminifera assemblage consists of Lepidocyclina (E) currence in shelf and hemipelagic sediments allowing direct formosa, L. (E.) favosa, L (N.) sumatrensis, Miogypsina comparison of LBF zones with oceanic plankton scales. LBF are sabahensis, Miogypsinoides dehaarti corresponding to the common to very abundant in facies dominated by corals in the Aquitanian stage, and the planktonic foraminifera assemblage con- Lower Kujung, Tuban and Bulu carbonates. LBF are rare in skeletal tains Globorotalia kugleri, Globigerinoides primordius, Globo- grainstones (Lower Kujung), red algae dominated facies (Tuban) quadrina dehiscens, Globigerinoides quadrilobatus, Gdes and sandy carbonates (Tuban and Bulu). LBF are almost absent in primordius and Globigerinoides trilobus. the Middle Kujung chalk, Tuban clastics, Ngrayong sand and Wonocolo shale. LBF are abundant as reworked clastics in Upper The oldest sandy carbonate unit exposed of Tuban Formation has an Kujung turbidites. age of 20.80 + 0.74 Ma (Table 1). Tuban carbonates yield an age of 20.17+0.74 (base of Burdigalian, N5) to 15.25 +1.36 (base of In these facies the occurrence of the LBF together with the Langhian, N9). This is consistent with the association of planktonic foraminifera, indicate the presence of strong currents Austrotrillina howchini, Lepidocyclina (Nephrolepidina) ferreroi, L. transporting the LBF towards deeper water marine waters in the (N.) martini, L. delicata, L. (N.) stratifera, L. (N.) inflata, L. (N.) open shelf area (BouDagher-Fadel 2002). Accurate age dating angulosa, L. (N.) brouweri, L. (N.) tournoueri, L. (N.) irregularis, L. of the studied sections is corroborated by Sr isotope dating (N.) kathiawarensis, L. (N.) verbeeki, Miogypsina digitata and where appropriate. This allowed us to revise the stratigraphic Katacycloclypeus annulatus. Two samples separating the Tuban ranges of some of theses LBF. carbonates from the Ngrayong Formation yield ages of 15.34 +1.36 and 15.25+1.36 (Table 1). This is consistent with the appearance of In correlating the LBF with the occurrence of the planktonic Katacycloclypeus annulatus, Orbulina sp. and Orbulina suturalis foraminifera and comparing the data with the strontium isotope towards the very top of the Tuban carbonates. Although Orbulina data, we were able to conclude that the LBF stratigraphic range suturalis (pl. 5) and Orbulina sp. have long stratigraphic ranges, chart (text-fig. 4) is consistent with the ages obtained from their first appearance datum is in upper Langhian (Zone N9 of Blow strontium dating (text-fig. 2). 1969) indicating that the top of the exposed Tuban carbonates is as young as Late Langhian in age. CONCLUSIONS The age of exposed Lower Kujung Formation is late Early The Bulu Member from the base of the section at Prantakan River Oligocene, Rupelian P20-Late Oligocene,Chattian, P21 respec- (Table 1) reveals an age of 12.98+1.36 Ma corresponding to the tively) based on identified foraminifera and strontium dating. Serravallian age (N12, Table 1). This age is consistent with the The faunal assemblage in Prupuh Ridge area indicates that the age range of the Katacycloclypeus annulatus, Lepidocyclina exposed Upper Kujung (shale, chalk and turbidites) are rich in

PLATE 4 Thin section photomicrographs of Early-Middle Miocene (Burdigalian-Serravallian) larger benthic foraminifera

1,6 Thin section photomicrographs of Katacyclocypeus 4 Lepidocyclina (N.) ferreroi Provale, Axial section, annulatus Martin. 1. Equatorial sections. Sample PR Sample GPS 150, 2001, Prantakan area, ×50. 171. 6. Vertical section, Sample 9.1.2. Mahindu area. ×200. 4, 6 Katacycloclypeus annulatus Martin. Axial section. Prantakan River. Sample #2. 4X50, 6 Sample 99.12 2 Thin section photomicrograph of Lepidocyclina ×60. (Nephrolepidina) ferreroi Provale. Prantakan area, GPS #150, 2001. ×50 5 Katacycloclypeus annulatus Martin. A) Fragments of equatorial sections. B) Fragment of an axial section. 3 Lepidocyclina (Nephrolepidina) ngampelensis Gerth. Prantakan River section .Sample #3.1. ×150 Kembang Baru section.Sample #10. ×150.

14 Essam F. Sharaf et al. Plate 3

stratigraphy, vol. 2, no. 3, 2005 15 Essam F. Sharaf et al.: Biostratigraphy and strontium isotope dating of Oligocene-Miocene strata, East Java, Indonesia larger benthic and planktonic foraminifera with stratigraphic sity of Wisconsin-Madison. Exxon Mobil and Anadarko have range of Early Miocene Aquitanian age (Te5) which is equiva- provided partial support to this research. The strontium analyses lent to Zone N4 of Blow (1969). Strontium isotope dating of the were funded by the donors of the Petroleum Research Fund of Prupuh carbonates exposed at Sukowati village and along the the American Chemical Society. western side of Prupuh Ridge gives an age of Late Oligocene (Chattian) to Early Miocene (Aquitanian) equivalent to Zones REFERENCES P22 to N4 of Blow (1969). The Tuban outcrops have a long ADAMS, C.G., 1970. A reconsideration of the Indian Letter classifica- stratigraphic range from Upper Te5-Tf1 (Burdigalian- tion of the Tertiary. Bulletin of the British Museum (Natural History) Langhian), which is equivalent to Zones N5-N9 of Blow Geology, 19, 85-137 (1969). The studied carbonate beds from Mahindu and Prantakan outcrops confirmed the presence of Orbulina sp. and ADAMS, C.G., 1984. Neogene larger foraminifera, evolutionary and Orbulina suturalis suggesting an age of late Langhian (N9) for geological events in the context of datum planes. In: Ikebe, I. and the top of the Tuban. This is consistent with the age constrained Tuschi, R., Eds., Pacific Neogene Datum Planes, p. 47-68. Univer- from strontium dating of the shale unit at the top of Prantakan sity of Tokyo Press. outcrop. ARDHANA, W., LUNT, P. and BURGON G.E., 1993. The deep marine The Bulu Member of the Wonocolo Formation is characterized by sand facies of the Ngrayong Formation in the Tuban Block, East Java faunal assemblage of late Mid –Late Miocene age (Serravallian Basin, 118-175. Indonesian Petroleum Association, Clastic Core –Tortonian). The strontium dating of the Bulu carbonates exposed Workshop. at Prantakan River is consistent with the age range obtained from the LBF. ASAHARA, Y., TANAKA, T., KAMIOKA, H., and NISHIMURA, A., 1995, Asian continental nature of 87Sr/86Sr ratios in north central The co-occurrence of both coralgal benthic planktonic Pacific sediments. Earth and Planetary Science Letters, 133: foraminifera rocks in the carbonate facies of the Oligocene and 105-116. Miocene of EJB is a rare opportunity for correlating the biostratigraphic framework of this region. These organism BEMMELEN, R.w. van, 1949. The Geology of Indonesia. The Hague: types although controlled by environment would have influ- Martinus Nijhoff, 732p. enced production rates on the reef and platform. BERGGREN, W.A., KENT, D.V., SWISHER, III, C.C., and AUBRY, M.P., 1995. A: revised Cenozoic geochronology and chronostrati- ACKNOWLEDGMENTS graphy. In: W. A. Berggren, D. V. Kent, M.P. Aubry and J. We would like to thank the Indonesian Institute of Technology Hardenbol, Eds., Geochronology, time scales and global strati- in Bandung (Prof. Lambok and Dardji), and specially Nuki graphic correlation. SEPM Special Publication, 54: 129-212. Nugroho for providing field assistance. We are grateful to Dr. Clay Kelly, Department of Geology and Geophysics, Univer- BOLLI, H.M., 1957. Planktonic foraminifera from Oligocene-Miocene sity of Wisconsin-Madison, Joseph Serra, University of Barce- Cipero and Lengua Formations of Trinidad, B.W.I., U.S National Museum Bulletin lona, and Peter Lunt , Coparex Blora, Indonesia for their help in 215: 97-123. identification of foraminifera and for their valuable recommen- ———, 1966. The planktonic foraminifera in well Bojonegoro-1 of dations. Martin Shield’s help in the field and was key to having Java. Eclogae Geologicae Helvetiae, 59 (1): 449-465. a better understanding of the EJB history. We want to thank Prof. C.M. Johnson, the director of thermal-ionization mass BLOW W. H., 1969. Late Middle Eocene to recent planktonic spectrometer lab at the University of Wisconsin-Madison, Dr. foraminiferal biostratigraphy. Proceedings of the First International Brian Beard and in particular, Brooke Swanson for the stron- Conference on Planktonic Microfossils Geneva, 1967, 1: 199-422. tium isotope analyses. We would like to thank the Micro- palaeontology Unit at UW-Madison for use of photographic BOUDAGHER-FADEL, M.K. and WILSON, M.E.J., 2000. A revision facilities. This work was funded by student grants from GSA, of some larger foraminifera from the Miocene of East Kalimantan. AAPG, and Department of Geology and Geophysics, Univer- Micropaleontology, 46: 153-165.

PLATE 5 1 Globoquadrina dehiscens (Cushman, Parr and Col- 4 Globorotalia praemenardii (Cushman and Stain- lins).Prupuh section. Sample # 35. ×150. forth). Northern Gunung Manak area, Sample 3.9.1. ×100. 2 Oblique thin sections of two specimens of Globi- gerinoides quadrilobatus (d’Orbigny). Prupuh sec- 5 Thin section photomicrographs of planktonic tion. Sample # 35. ×250. foraminifera: Globigerinoides spp., and Globigeri- noides quadrilobatus (d’Orbigny) . Prupuh section. 3 Globigerinoides trilobus (Reuss). Prupuh section. Sample # 37. ×100. Sample # 35. ×150 6 Orbulina suturalis Brönnimann. Prantakan area, GPS # 150, 2001. ×200.

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stratigraphy, vol. 2, no. 3, 2005 17 Essam F. Sharaf et al.: Biostratigraphy and strontium isotope dating of Oligocene-Miocene strata, East Java, Indonesia

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