Carbonate Facies and Sedimentation of the Klapanunggal Formation in Cibinong, West Java

DOI:10.17014/ijog.v1i3.196The limestone of Klapanunggal Formation is well exposed in the area of Cibinong and its surrounding,West Java. Detailed Observation of carbonate rock has been conducted in this area and aims to studythe carbonate facies and its growth environment. The method used in the field is the detailedinvestigation, while mikropaleontology and petrogaphic analysis conducted in the laboratory. Theresult of this study indicate that the carbonate rocks in the study area consists of four facies. namely:(1) boundstone facies, (2) packstone facies, (3) rudstone facies, and (4) limestone breccia facies. Basedon these data be interpreted that the boundstone facies was deposited in the reef front to reef crestenvironment, packstone facies developed on the lower slope, upper slope, and back-reef lagoonenvironment. Rudstone facies formed on the reef front, and breccia limestone facies were formed inthe lower slope. Geographically, the position of the carbonate body environment that is at the reeffront, upper slope and lower slope is expected to be in the North – North East while the reef crest andback reef lagoon is on the South – Southwest

Sedimen sebagai Arsip Perubahan Lingkungan

Perubahan lingkungan di wilayah pesisir teluk Jakarta akan berpengaruh pada kualitas lingkungan perairan di Teluk Jakarta. Hal tersebut akan terekam oleh inti bor sediment yang terdapat di Teluk Jakarta. Penelitian ini merupakan penelitian pendahuluan yang bertujuan untuk meneliti Perubahan pola sedimentologi dari conto inti bor sedimen dari teluk Jakarta. Dalam studi pendahuluan ini dilakukan analisis LOI untuk mengetahui kadar material organik dan juga analisis mikropaleontologi Hasil analisis pada Bor GC 21 menunjukkan adanya korelasi yang baik antara peningkatan kadar material organic dan penurunan kadar karbonat dengan Perubahan kandungan fosil. Meningkatnya kandungan foraminifera plankton pada kedalaman 13-14 cm diikuti menghilangnya ostracoda pada kedalaman 12-13 cm kemungkinan berkaitan dengan letusan Krakatau 1883. Kata Kunci : sedimen, inti bor, lingkungan, Teluk Jakarta. The environtmental changes around Jakarta coastal area will influence the environmental quality of Jakarta bay waters. Marine sediment core in the Jakarta bay will records these changes. This preliminary research will study the sedimentology pattern of marine sediment located at Jakarta bay. In this study LOI sediment core will be analysed for LOI and micropaleontology. The result from core GC 21 shows that increasing material organic content coincide with decreasing the content of carbonate and microfossil. Increasing foraminifera plankton at 13-14 cm depth coincide with disappearance of ostracode at 12-13 depth, this suppose that related to the Krakatau eruption on 1883. However the further research is still required to convince the result. Keywords : sediment, core bor, environment, Jakarta Ba

Turbidite Facies of the Halang Formation in Ajibarang Area, Central Java

DOI: 10.17014/ijog.v6i1.112An understanding of deepwater turbidite sediments is very important mainly dealing with the determination of a reservoir geometry. The problem arising in the turbidite sediment geometry is very complex and varied, and its existence depends on how, when, and type of its environment. In Central Java, the broad turbidite sediment distribution of the Halang Formation is needed to be observed its facies association. This paper will discuss the turbidite facies of Halang Formation in the Ajibarang area. The method used to analyze the turbidite facies is by measuring stratigraphic sections and observing the lithofacies characteristics to reconstruct its depositional environment. The Halang Formation outcrop in the Ajibarang area is dominantly composed of alternating sandstone and claystone or marl. Based on the observation, the turbidite facies of Halang Formation, in the Ajibarang area, was deposited on a submarine fan system at the middle fan of suprafan lobes. Compiling with the previous studies, the source of the Halang Formation is indicated to be derived from the south southwest

Depositional Environment of the Batuasih Formation on the Basis of Foraminifera Content: a Case Study in Sukabumi Region, West Java Province, Indonesia

DOI: 10.17014/ijog.v7i2.139The research was carried out on the sediments of the Batuasih Formation cropping out at Batuasih Village, Cibatu River, Padaarang Sukabumi. Data obtained from field observation, as well as foraminifera and sedimentology analyses conducted in the laboratory, were used to interpret its depositional environment. The investigation was focused on planktonic and benthic foraminiferal assemblages for depositional environment interpretation that might not be used by previous researchers. The Batuasih Formation is composed of black shaly claystone, where the lower part is rich in clay ball, and limestone intercalations in the upper part of the formation. In Cibatu Section, no clay balls is recognized in the lower part, but intercalations of limestone still occur. However, a contrast difference is found in Padaarang section, where green claystone interbeds with fine-grained sandstone. The Batuasih Formation conformably overlies the Walat Formation containing conglomerate. Foraminifera fossil found in the Batuasih Formation consists of bad preserved black benthic and planktonic foraminifera, more abundant towards the lower part of formation. Based on foraminifera assemblage comprising genus Uvigerina, Cibicides, Elphidium, Operculina, Bulimina, Bolivina, Eponides, and Neoconorbina, supported by sedimentology data, the Batuasih Formation was deposited in a shallow to deep marine environtment, during Early Oligocene (P19) time. Upwards to be the Rajamandala Formation, the depositional environment tends to be shallower gradually

POTENSI DAN KARAKTERISTIK BATUAN SUMBER HIDROKARBON DARI CONTO PERMUKAAN DI DAERAH KARAWANG, JAWA BARAT

ABSTRAK Penelitian batuan sumber hidrokarbon yang dilakukan di daerah Karawang bertujuan untuk memperoleh data permukaan endapan klastik berbutir halus serta karakteristik litofasies yang diduga sebagai batuan induk hidrokarbon. Metode yang dipakai adalah penelitian lapangan dan laboratorium. Penelitian lapangan meliputi pengamatan stratigrafi detil dan pengambilan conto batuan. Analisa laboratorium terdiri dari analisa kandungan TOC dan pirolisis Rock Eval. Hasil analisa TOC terhadap 17 conto batulempung yang diambil dari Formasi Jatiluhur menunjukkan nilai berkisar antara sebesar 0,53-2,02%. Tmax delapan  conto sebesar 422o-432oC menunjukkan tingkat kematangan thermal yang belum matang. Delapan conto lainnya masuk dalam kategori matang dengan nilai Tmax sebesar 436o-462oC, sedang satu conto dengan nilai Tmax 467oC menunjukkan kategori pasca matang. Nilai HI berkisar antara 33-143 mg HC/TOC, dan termasuk dalam Fasies D, CD dan C. Berdasarkan nilai tersebut, batuan sumber di daerah penelitian dapat menghasilkan gas dengan kuantitas kecil. Potensi hidrokarbon di daerah penelitian menunjukkan kategori kekayaan material organik rendah hingga menengah, dengan kerogen yang termasuk type II dan III. Kualitas batuan sumber berdasarkan nilai HI termasuk dalam kategori gas prone

GEOKEMIJA POTENCIJALNIH MATIČNIH STIJENA I IZDANAKA PRIRODNOGA PLINA U ARHIPELAGU MANGOLE-TALIABU, SJEVERNI MALUKU, INDONEZIJA

The Mangole-Taliabu Archipelago has great potential for natural gas exploration due to its many active natural gas seepages. The limited natural gas exploration activities initiated during the last three decades led to a lack of publications on source rock and natural gas geochemistry. Previous research has postulated that the potential source rocks in this area and its surroundings are the Buya and Salodik formations, and known active natural gas seepages are hypothesised to originate from humic organic matter (type-III kerogen). The research aims to review and re-discuss the geochemical characteristics of potential source rock, the origins and genetics of natural gas seepages, and the correlation between natural gas seepage and source rocks by integrating the existing data with the newly collected data. This research revealed that the potential source rock is the Bobong Formation, aside from the previously confirmed Buya Formation, while the Salodik Formation is not a potential source rock as was suggested in previous publications. The most significant research finding is the type of natural gas seepage which found not only coal-derived gas but also oil-type gas. The calculated Ro of the coal-derived gas source rock is 0.80% – 1.00% and that of oil-type gas source rock ranges between 0.50% – 1.31%. For gas–source rock correlation, the Bobong Formation appears to be the most likely source for RAG/88/012 and RAG/88/014 gas samples, while the Buya Formation is the source for Binono Seep, RA/21/33, RA/21/34, and RA/21/35 gas samples. The new research findings are hoped to have significant implications for increasing the understanding of the petroleum system and encouraging further exploration activities.Arhipelag Mangole-Taliabu ima velik potencijal za istraživanje prirodnoga plina zbog brojnih aktivnih izdanaka prirodnoga plina. Ograničenost istraživačkih aktivnosti započetih tijekom posljednjih triju desetljeća dovele su do nedostatka publikacija o geokemijskim značajkama matičnih stijena i prirodnoga plina. Prethodna istraživanja pretpostavila su da su potencijalne matične stijene u istraživanome području i njegovoj okolici vezane uz formacije Buya i Salodik, a pretpostavlja se i da poznati aktivni izdanci prirodnoga plina potječu od humusne organske tvari (kerogen tipa III). U okviru ovoga istraživanja cilj je bio dati pregled i korištenjem postojećih i novoprikupljenih podataka ponovo raspraviti o geokemijskim karakteristikama potencijalnih matičnih stijena, podrijetlu i genetici prirodnoga plina te korelaciji između prirodnoga plina koji se pojavljuje na izdancima matičnih stijena. Ovo istraživanje otkrilo je da, osim prethodno potvrđene formacije Buya, formacija Bobong predstavlja formaciju s potencijalnim matičnim stijenama, dok u formaciji Salodik nisu zapažene potencijalne matične stijene, na što su upućivali rezultati prijašnjih istraživanja. Najvažniji rezultat istraživanja vezan je uz definiranje tipa prirodnoga plina na izdancima u kojemu nije pronađen samo plin dobiven iz ugljena kao matične stijene, već i plin iz nafte. Izračunani Ro za ugljenu matičnu stijenu kreće se između 0,80 % i 1,00 %, dok za naftno-matičnu stijenu varira između 0,50 % i 1,31 %. Korelacija između uzoraka prirodnoga plina s izdanaka i matične stijene upućuje na to da je formacija Bobong vjerojatno izvor za uzorke plina RAG/88/012 i RAG/88/014, dok je formacija Buya izvor za uzorke plina Binono Seep, RA/21/33, RA/21/34 i RA/21/35. Novi rezultati ovih istraživanja trebali bi imati znatan utjecaj na povećanje razumijevanja naftnoga sustava i poticanje daljnjih istraživačkih aktivnosti

Studi Potensi Batuan Induk pada Sub Cekungan Banyumas dan Serayu Utara

Kajian yang dilakukan di daerah Banjarnegara, Wonosobo dan Kebumen bertujuan  untuk memperoleh data permukaan endapan klastik berbutir halus serta karakteristik litofasiesnya yang diduga berpotensi sebagai batuan induk. Sebanyak 9 conto dianalisa kandungan material organik karbonnya (TOC). Hasil analisa tersebut memperlihatkan bahwa nilai TOCnya berkisar antara   0,08 % dan 1,42 %. Berdasarkan hasil tersebut, didapatkan 2 conto berpotensi baik dan 3 conto berpotensi sedang  untuk dapat membentuk hidrokarbon, sedangkan  4 conto lainnya tidak berpotensi untuk membentuk hidrokarbon. Pyrolisis rock-eval dilakukan terhadap 5 conto yang berpotensi membentuk hidrokarbon, dan mempunyai nilai HI berkisar antara 26 dan 95 mgHC/gTOC. Berdasarkan nilai parameter evaluasi batuan induk HI (Waples, 1985), conto tersebut  berada dalam fasies organik CD dan D. Batuan induk tersebut dapat menghasilkan gas dalam kuantitas kecil. Hasil sementara dari pengamatan singkapan menunjukkan bahwa batuan klastik berbutir halus di daerah Banjarnegara diduga diendapkan dalam lingkungan dysaero

PERUBAHAN LINGKUNGAN DAN EVOLUSI MANGROVE DI PULAU BELITUNG SELAMA HOLOSEN AKHIR BERDASARKAN REKAMAN POLEN

Studi sejarah fluktuasi muka air laut dan perubahan lingkungan di Paparan Sunda masih sedikit dilakukan. Ada dua isu yang saling terkait yang menjadi permasalahan utama terkait dengan perubahan muka air laut di wilayah ini yaitu kurangnya rekaman data fluktuasi muka air laut dan perubahan lingkungan selama kurun waktu mid-late Holosen dengan kualitas yang bagus. Hal itu memiliki konsekwensi terhadap munculnya isu kedua yaitu tidak terdefinisikannya secara jelas dan tepat baik waktu maupun besaran posisi muka air laut pada saat mid-Holosen. Penelitian ini dilakukan untuk merekonstruksi perubahan lingkungan selama Holosen Akhir di wilayah Paparan Sunda menggunakan rekaman polen endapan mangrove. Pemboran tangan dilakukan guna pengamatan stratigrafi dan pengambilan sampel untuk analisis-analisis sedimentologi dan mikropaleontologi di laboratorium. Hasil studi ini menunjukkan bahwa perubahan lingkungan terjadi di Pulau Belitung selama setidaknya 1500 tahun terakhir sebagai akibat dari proses progradasi. Proses ini menyebabkan garis pantai terus maju hingga mencapai posisi saat ini. Endapan mangrove di lokasi penelitian juga merekam kejadian insidentil yang secara hipotetis diduga sebagai peristiwa tsunami akibat letusan Krakatau yang terjadi pada tahun 1883 AD dan sekitar 535-536 AD.Kata Kunci: Belitung, polen, mangrove, Mid-Holosen, Krakatau, muka laut, perubahan lingkungan.There is only minor study on sea-level fluctuation and environmental change in Sunda Shelf. The main isues in this area are lacking good quality of sea-level fluctuation and environmental change record during mid-late Holocene in which accordingly the onset time and sea-level height of the Mid-Holocene Maximum Transgression event have not been well defined. This study aims to reconstruct environmental changes during late Holocene in the Sunda Shelf area based on mangrove pollen record. Hand-auger was applied to make stratigraphic observation and sampling for sedimentological and micropaleontological analyses in the laboratory. Result of this study shows environmental changes occured within the last ca.1500 years due to coastal progradation in Belitung. This progradation shifted the coastal line seaward to attain the present position. The pollen record also reflects rapid and brief changes that may hypothetically be interpreted as the 535-536 AD and 1883 AD Krakatau tsunamis.Keywords: Belitung, pollen, mangroves, Mid-Holocene, Krakatau, sea level, environmental changes