THE USE OF FORAMINIFERA FOSSILS FOR RECONSTRUCTING THE YOGYAKARTA GRABEN, YOGYAKARTA, INDONESIA

The Yogyakarta region is located in the southeastern part of Central Java, Indonesia. The region forms an elongated northeast – southwest-trending central depression bordered by two parallel faults in the west and east. These major faults divided the area into three parts, including the western, central and eastern parts. Herein, we investigate the relative uplift rate of the each part by using planktonic and benthonic foraminiferas. The foraminifera will show the initial position/datum of each part before uplift. Over sixty samples (primarily limestones and marls) were taken for this research. The uplift rates of each part were different and created a depressed block control by way of parallel faults. Based on foraminifera fossil observations, each block was in the same depositional environment (inner neritic) during N9. The present positions indicate that the western part was uplifted higher than the others, with this part being uplifted more than 590 meters. The central part was uplifted less than 120 meters, and the eastern part was uplifted above an altitude of 170-300 meters. Keywords: Foraminifera fossil, planktonic, benthonic, graben, uplif

Biostratigraphy and Paleobathimetry Microfossil Foraminera in the Sentolo Formation on the Jambon Line, Bantul Regency, Special Region of Yogyakarta Province

Foraminifera microfossils can be used to determine the age of rocks and the depositional environment of an area. The research location is part of Sentolo Formation. Our stratigraphic data located on the Jambon section, Bantul Regency, Special Region of Yogyakarta Province. The appearance of the research area is in the form of well-exposed and ideal cliffs and the lithology of the formation has the potential for rock content rich in foraminifera microfossils. This is the reason for the microfossil analysis of planktic and benthic foraminifera in the study area. The purpose of this study is to determine the age and depositional environment. The research method was carried out by measuring the stratigraphic sections, sampling, and doing paleontological analysis based on planktic and benthic foraminifera. The results showed that the biostratigraphy can be divided into Globigerina venezuelana Zone (N18) & the Globorotalia plesiotumida Zone (N19), as well as the paleobathimetry, belongs to upper - lower bathyal

Biostratigraphy and Climate Change in the Late Miocene Age Based on Foraminifera in the Oyo Formation, Oyo River Section, Gunung Kidul, Yogyakarta

The date of the paleoclimate event was ascertained using a biostratigraphic analysis. The thickness of the Oyo Formation was measured using measurements with a Jacob stick method, yielding a thickness of 80.8 meters and 23 rock samples. In the Southern Mountains Zone,  new result of the age of the upper part of the Oyo Formation by biostratigraphy investigation of the hill Late Miocene (9.79 Ma to 5.78 Ma). Biostratigraphic investigation in the Oyo River revealed 28 species and 9 genera, with two datums. The study area was classified into three biozonations based on the datum found Globorotalia acostaensis/M13a/N16 zone, the lower Globorotalia plesiotumida/M13b/N17 zone, and the upper Globigerinoides conglobatus/M14/N17 zone. The results of a paleoclimate analysis on the Oyo River Section show a general cooling tendency in the study area. Seven paleoclimate zones can be determined from these trends consisting of four warm and three cold zones. Zone I (warm), zone II (cold), zone III (warm), and zone IV (cold) have the coldest peak in the study region in 8.3 Ma, zone V (warm), and zone VI (cold), followed by zone VII (warm). Based on the correlation with other studies (South China Sea, Pacific Ocean, Oyo River, Ngalang River, and Ngioro Section), paleoclimate events in the study area occur globally

The Diversity of Ray-finned Fishes (Actinopterygii) in Plio-Pleistocene Java

Java has been known in the world of Paleontology as a contributor to the findings of Homo erectus fossils, but there are still other fossil findings that have not been identified until now, especially fossil fishes of the subclass Actinopterygii. This research was conducted to recognize the diversity of the actinopterygians fishes in Plio-Pleistocene of Java and to determine the diagnostic characters of each taxon group of fossils in the Plio-Pleistocene of Java. The study was carried out using comparative anatomical methods with present-day specimens and fossil findings collection of the Laboratory of Bioanthropology and Paleoanthropology, Faculty of Medicine, Public Health and Nursing, Universitas Gadjah Mada; Bandung Geological Museum and Sangiran Early Man Site. The research found at least 8 species of fish fossils in Java which belong to three order, i.e., the order Siluriformes with 5 identified species: Bagarius gigas, Hemibragus nemurus, Clarias macrocephalus, family Ariidae with indeterminate genus or species, Plotosus canius, Clarias batrachus, and family Pangasiidae with indeterminate genus or species; the order Perciformes with two identified species: Anabas testudineus and Sphyraena crassidens; and the order Cypriniformes with one identified species: Osteochilus vittatus. Based on the fossil findings showed that the Java Island during the Plio-Pleistocene used to be a marine environment that gradually ascending into a lowland river which closes to mangrove swamps and estuaries while the ancient Bandung lake site was a lacustrine environment with calm currents and is overgrown with riparian vegetation

KARAKTERISASI MASSA BATUAN DAN EVALUASI KESTABILAN LERENG DENGAN METODE NUMERIK PADA RUAS JALAN PLANJAN–BARON–TEPUS

This research aims to evaluate the stability of the slope by considering the rock mass characterization. The research location was conducted on the Planjan–Baron–Tepus section at STA 7+000 to STA 9+725, with limestones dominating the lithology. The data collection method begins with determining rock mass quality based on rock mass classification using the Geological Strength Index (GSI) of limestone introduced by Marinos (2010). The results of testing the physical and mechanical properties of rocks and the quality of rock mass will be used as input parameters in the slope stability analysis. The results showed that the rock mass quality in the research area varied from "good" condition at STA 9+075, "fair" condition at STA 7+825, to "poor" condition at STA 8+475. Based on the slope stability analysis using the finite element method and the Generalized Hoek-Brown failure criteria, the result of the slope analysis at three locations representing the rock mass quality was a stable (safe) condition without seismic loads and with seismic loads. Key words:  slope stability, rock mass quality, geological strength index, limestone, finite element method.Penelitian ini bertujuan untuk menganalisis kestabilan lereng dengan mempertimbangkan karakterisasi massa batuan. Lokasi penelitian terletak pada ruas Planjan–Baron–Tepus pada STA 7+000 sampai STA 9+725 dengan litologi yang mendominasi adalah batugamping. Metode pengambilan data diawali dengan penentuan kualitas massa batuan berdasarkan klasifikasi massa batuan dengan metode Geological Strength Index (GSI) batugamping yang diperkenalkan Marinos (2010). Hasil pengujian sifat fisik dan mekanik batuan, serta kualitas massa batuan akan dijadikan parameter input dalam analisis kestabilan lereng. Hasil penelitian menunjukkan bahwa kualitas massa batuan lokasi penelitian bervariasi mulai dari kondisi baik (good) pada STA 9+075, kualitas massa batuan sedang (fair) pada STA 7+825, hingga kualitas massa batuan buruk (poor) pada STA 8+475. Berdasarkan analisis kestabilan lereng dengan metode elemen hingga dan kriteria keruntuhan Generalized Hoek-Brown didapatkan hasil bahwa lereng pada tiga lokasi yang mewakili kualitas massa batuan berada dalam kondisi stabil (aman) pada kondisi tanpa beban gempa dan kondisi dengan beban gempa. Kata Kunci: kestabilan lereng, kualitas massa batuan, geological strength index, batugamping, metode elemen hingga

HUBUNGAN STRATIGRAFI ANTARA SATUAN BATUAN VULKANIK DENGAN SATUAN BATUAN KARBONAT DI DAERAH BANGUNJIWO DAN SEKITARNYA, KECAMATAN KASIHAN, KABUPATEN BANTUL, PROVINSI DAERAH ISTIMEWA YOGYAKARTA

Latar belakang penelitian adalah terdapatnya batuan vulkanik berupa breksi andesit pada lokasi penelitian yang sebelumnya dipetakan sebagai batuan karbonat dari Formasi Sentolo dan endapan vulkanik kuarter Gunung Merapi dalam Peta Geologi Yogyakarta (1997). Tujuan penelitian adalah untuk menentukan hubungan stratigrafi antara satuan batuan vulkanik dengan satuan batuan karbonat. Daerah penelitian secara administratif berada di Desa Bangunjiwo dan sekitarnya, Yogyakarta, Indonesia. Metode yang digunakan meliputi pemetaan geologi, pengambilan sampel paleontologi dan petrografi, serta pengamatan sampel fosil dan sayatan. Berdasarkan hasil analisa yang dilakukan didapatkan bahwa daerah penelitian dibagi menjadi enam satuan batuan yaitu: satuan packestone-wackestone, packestone-grainstone, packestone-rudstone, konglomerat andesittuf kristal, konglomerat andesit-breksi andesit, dan pasir kerakalan. Batuan karbonat terbentuk pada Miosen tengah sampai Pliosen akhir (N10-N21) di lingkungan batial bawah sampai neritik luar dengan proses pengendapan yang menerus. Batuan vulkanik terbentuk pada Kala Pleistosen sampai Holosen di lingkungan darat dan fluvial oleh mekanisme pengendapan berupa pyroclatic flow, traction flow, dan mass flow dengan proses pengendapan yang tidak menerus. Hubungan stratigrafi antara satuan batuan vulkanik dengan satuan batuan karbonat adalah tidak selaras, dengan jenis ketidakselarasan menyudut pada beberapa lokasi, dan kontak berupa bidang ketidakselarasan erosional. Kata kunci: Daerah Bangunjiwo, hubungan stratigrafi, batuan karbonat, batuan vulkani

ANALISIS MIKROFASIES BATUGAMPING FORMASI WUNGKAL-GAMPING JALUR PADASAN, GUNUNG GAJAH, BAYAT, KLATEN, JAWA TENGAH

Formasi Wungkal-Gamping merupakan formasi batuan sedimen tertua di Pulau Jawa yang tersingkap ke permukaan. Formasi ini beranggotakan batupasir, napal, serta lensa batugamping yang kaya akan kandungan fosil foraminifera besar mewakili umur Eosen Tengah hingga Eosen Akhir (Rahmawati, 2019). Analisa mikrofasies dilakukan berdasarkan pengamatan petrografis sayatan tipis batugamping dengan berfokus kepada jenis, ukuran dan asosiasi komponen penyusun batugamping serta kelimpahannya. Berdasarkan analisis yang dilakukan pada studi ini, didapatkan 4 tipe standar mikrofasies yang berkembang di Formasi Wungkal-Gamping yaitu Nummulites-Planocamerinoides grainstone, fasies Nummulites-Planocamerinoides rudstone, fasies Nummulites grainstone, dan fasies Nummulites rudstone. Dasar dari penetapan tipe standar mikrofasies ini sangat penting guna melakukan interpretasi lingkungan pengendapan dan rekonstruksi paleogeografinya

Analisa Arus Purba Formasi Pucangan - Kabuh di Trinil, Kabupaten Ngawi, Propinsi Jawa Timur

Sejak penemuan Pithecantrobus Erectus (sekarang Homo Erectus) oleh Dubois (1891), Formasi Pucangan- Kabuh di Trinil menjadi obyek yang wamai dibicarakan. Sebaran Formasi Kabuh ini cukup luas meliputi sisi selatan dari Pegunungan Kendeng yang menyebar dari barat ke timur. Formasi ini tersusun oleh konglomerat andesit, batupasir vulkanik, breksi – konglomerat vulkanik (lahaar) dan setempat mengandung batujahe (caliche) dan calcrete. Banyaknya penemuan arkeologis pada formasi ini ditafsirkan sebagai rumah dari Homo Erectus. Namun melihat litologi dan banyaknya struktur silang siur, tampaknya fosil dan artefak yang ditemukan merupakan thanatocoenosis reworked. Metode penelitian adalah melakukan pengukuran stratigrafi (MS) dalam sekala 1:50 dan mengukur arah arus purba di lapangan sepanjang Sungai Bengawan Solo di 4 lokasi. Keempat lokasi ini terletak di selatan Museum Trinil, timur Museum Trinil, lokasi eskavasi Dubois dan di desa Gadjah. Hasil pengukuran menunjukkan bahwa Sungai Bengawan Solo Purba umumnya mengalir dari barat ke timur dan anak sungai yang mengalir dari tenggara ke barat daya

HIDROGEOLOGI KAWASAN KARST GUNUNGSEWU: Panduan Lapangan Fieldtrip PAAI 2017

Gunungsewu terletak di bagian tengah Pulau Jawa bagian selatan. Secara administratif Kawasan Karst Gunungsewu terletak pada empat kabupaten, yakni Kabupaten Bantul dan Kabupaten Gunungkidul (Daerah Istimewa Yogyakarta), Kabupaten Wonogiri (Provinsi Jawa Tengah), serta Kabupaten Pacitan (Jawa Timur). Kawasan Karst Gunungsewu memiliki luas sekitar 1.300 km2, membentang sejauh 85 km (barat ke timur) dengan lebar antara 10 km samoai dengan 29 km (arah utara-selatan). Elevasi wilayah mulai dari 0 mdpal pada wiayah pantai selatan Jawa, sampai dengan sekitar 512,5 mdpal. Gunungsewu memiliki karakteristik hidrologi unik karena perkembangan lorong-lorong pelarutan