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All Journal IJOG : Indonesian Journal on Geoscience Berita Sedimentologi

Yahdi Zaim

Geology Department, Bandung Institute of Technology

Author-ID : 427164

Earth & Planetary Sciences

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Perkembangan Geologi pada Kuarter Awal sampai Masa Sejarah di Dataran Yogyakarta Mulyaningsih, Sri; Sampurno, Sampurno; Zaim, Yahdi; Puradimaja, Deny Juanda; Bronto, Sutikno; Siregar, Darwin Alijasa
Indonesian Journal on Geoscience Vol 1, No 2 (2006)
Publisher : Geological Agency

http://dx.doi.org/10.17014/ijog.vol1no2.20065The uplift of Southern Mountains in Early Pleistocene has formed the Yogyakarta Basin. In this basin, the Merapi volcanic activity has been developing. Based on 14C dating in cinder deposits exposed at Cepogo, the volcanic activity took place since Â±42 ka. While on the basis of K/Ar dating in andesitic lava at Bibi Volcano, the activity took place since 0.67 ma. The high in the south and the appearance of Merapi volcanic dome in the north had caused a fl at valley. The southern part of the valley is bounded by the Southern Mountains and the western part is bounded by the West Progo Mountains. In the present time, the lithology of the areas which are interpreted as a palaeo-valley is composed of black clay deposits. This black clay is a contact between the basement rocks and Merapi volcanic deposits. The black clay deposits exposed in the Progo River (Kasihan) has been developed since Â±16.59 to 0.47 ka, while in the Opak River (Watuadeg) 6210 y BP. Younger black clay deposits intersecting with lahars are also exposed at the Winongo River and have an age of 310 y BP. The age data of volcanic stratigraphy shows that Merapi activities had taken place since Â±6210 up to Â±310 years ago. Â

Dinamika pengendapan lahar permukaan pada alur-alur lembah di bagian selatan Gunung Api Merapi, Yogyakarta Mulyaningsih, Sri; Sampurno, Sampurno; Zaim, Yahdi; Puradimaja, Deny Juanda; Bronto, Sutikno
Indonesian Journal on Geoscience Vol 1, No 3 (2006)
Publisher : Geological Agency

http://dx.doi.org/10.17014/ijog.vol1no3.20062Endapan aliran rombakan Gunung Api Merapi, yang lebih dikenal sebagai lahar, terbentuk dari hasil longsoran endapan awan panas yang dipicu oleh curah hujan yang sangat tinggi. Pada saat ini, endapan awan panas tersebut berasal dari guguran kubah lava. Material suspensi tersebut selanjutnya menuruni lereng dengan kecepatan yang tinggi, menghasilkan aliran turbulen. Aliran tersebut biasanya berkembang pada daerah dengan perbedaan morfologi berkemiringan lereng tinggi ke landai, atau yang sering dikenal sebagai daerah tekuk lereng. Studi ini didasarkan pada pengamatan dan pengukuran fragmen lahar yang berukuran besar di permukaan. Analisis meliputi arah penyirapan, bentuk, dan besar butir fragmen. Hasil penelitian mendapatkan model arah aliran fragmen besar lahar dari bagian atas aliran rombakan, yang membentuk âmodel punggung katakâ atau âmodel punggung gajahâ. Bagian depan katak atau gajah (kepala) yaitu arah aliran atau bagian depan aliran. Hasil penelitian juga menunjukkan bahwa model tersebut berlaku pada fragmen dengan diameter 90 cm atau lebih besar. Di daerah penelitian, fragmen dengan diameter 90 cm mencapai jarak hingga 22 km dari sumbernya. Hasil penelitian ini dapat digunakan sebagai model untuk menentukan arah aliran lahar (aliran rombakan) purba yang sumbernya belum diketahui. Â

Palaeontological surveys in Central Sumatra and Bangka Louys, Julien; Zaim, Yahdi; Rizal, Yan; Price, Gilbert J.; Aswan, Aswan; Puspaningrum, Mika Rizki; Smith, Holly; Hascaryo, Agus Tri
Berita Sedimentologi Vol 47, No 3 (2021)
Publisher : Ikatan Ahli Geologi Indonesia

We report on results from surveys undertaken in Sumatra during 2018 and 2019. The surveys had three objectives: (1) to examine, sample, and record the extensive Quaternary fossil deposits from caves in West Sumatra; (2) determine the potential for fluvial deposits in Riau and Jambi provinces; and (3) relocate the fossil proboscidean remains reported from Bangka Island. Our surveys produced several significant results. We mapped three important Padang Highland caves, Ngalau Lida Ajer, Ngalau Sampit, and Ngalau Gupin, locating and sampling the main fossil deposits in each, as well as recording additional caves in the region. Our surveys of the fluvial systems in central-west Sumatra did not reveal any vertebrate Pleistocene deposits but did yield Mio-Pliocene trace fossils. Finally, we relocated elephant fossils from Bangka, but no in situ vertebrate remains could be found. These finds add important new data to the geological history of Sumatra.

Mud Volcano in Southeast Maluku: Evidence for Neotectonics in East Indonesia Zaim, Yahdi; Ernawan, Budi; Fachrizal, Fachrizal
Berita Sedimentologi Vol 24, No 1 (2012)
Publisher : Ikatan Ahli Geologi Indonesia

Mud volcanoes are observed in S.E. Maluku, east Indonesia, in Babar, Tanimbar and in the Kai islands. They are active, show bubbles of flammable gases, mud flows and rock fragments, and except in the Kai Islands, are associated with melange complexes. They have also been reported to be present on Timor Island. The formation of active mud volcanoes in S.E. Maluku is closely related to the geology and tectonics of this region, and is due to subsurface overpressures forming liquefied shale that is extruded along thrust faults and fractured zones. The association of melange complexes and Quaternary fractured limestone terraces with mud volcanoes is closely related to the Quaternary and neotectonic activities in this region. Mud volcanism in this region is probably one of the main processes leading to the formation of chaotic deposits in the Quaternary in SE Maluku.

Isotopic reconstruction of Proboscidean habitats and diets on enigmatic island of Sulawesi Puspaningrum, Mika Rizki; Chivas, Allan R.; Kurniawan, Iwan; Wibowo, Unggul P.; Zaim, Yahdi; van den Bergh, Gerrit D.
Berita Sedimentologi Vol 47, No 3 (2021)
Publisher : Ikatan Ahli Geologi Indonesia

Sulawesi is known for its complex geological and biogeographic history, which is reflected in their extinct and extant faunal assemblage. Evidence of oldest terrestrial fauna in Sulawesi was found in the Early Pleistocene sediment and evolved since then. Despite being mostly isolated from the mainland Southeast Asia; four successive Proboscidean taxa have been found from the southern part of the island. The four taxa are: Stegoloxodon celebensis, Stegodon sompoensis, Stegodon sp. B, and cf. Palaeoloxodon namadicus, in which respective taxa are included in successive faunal stages. The aim of this research is to reconstruct the diet and palaeoenvironment of these Proboscidean taxa by incorporating stable isotope analysis with the fossil faunal record, geology, and stratigraphy. Stable carbon (δ13C) and oxygen (δ18O) isotope analysis were especially used in this study. Our result suggests that Stegoloxodon celebensis and Stegodon sompoensis were flexible feeders and were able to adapt to different niches, from closed canopy forest to open vegetation, while the diets of Stegodon sp. B, Celebochoerus heekereni and cf. Palaeoloxodon namadicus suggest that they were more specialized.

The Palaeo-Kambaniru river mouth, Sumba, East Nusa Tenggara, Indonesia: A record of strongly seasonal catastrophic flow in a monsoon-controlled deltaic complex Zonneveld, John-Paul; Zaim, Yahdi; Rizal, Yan; Aswan, Aswan; Fortuin, Anne; Larick, Roy; Ciochon, Russell L.
Berita Sedimentologi Vol 47, No 3 (2021)
Publisher : Ikatan Ahli Geologi Indonesia

The Kambaniru River valley near the city of Waingapu preserves a thick succession of coarse-grained fluvial-deltaic sediment deposited during the Late Pleistocene. This succession incises through a thick uplifted coral reef terrace succession and records intervals of highly episodic flow events during the last glacial interval. The occurrence of intraclastic, coarse sand/gravel matrix olistostromes in several areas attests to the occasionally catastrophic nature of flow in the ancestral Kambaniru River. Small to moderate-sized coral-rich reefs and laterally restricted reef terraces occur on delta-front conglomerate successions at multiple horizons through the study interval. These reefs record both intervals of low flow as well as periodic river-mouth avulsion episodes. Comparison of radiometric dates obtained from pelecypod and coral material from both deltaic successions and laterally adjacent coral reef terrace intervals indicates that uplift/subsidence history of the terraces differs from that of the valley and that correlation between the two should be taken with care.

Co-Authors Agus Tri Hascaryo, Agus Tri Aswan Aswan Chivas, Allan R. Ciochon, Russell L. Darwin Alijasa Siregar Deny Juanda Puradimaja Ernawan, Budi Fachrizal Fachrizal, Fachrizal Fortuin, Anne Iwan Kurniawan Larick, Roy Louys, Julien MIKA RIZKI PUSPANINGRUM, MIKA RIZKI Mulyaningsih, Sri Price, Gilbert J. Sampurno Sampurno Smith, Holly Sutikno Bronto van den Bergh, Gerrit D. Wibowo, Unggul P. Yan Rizal, Yan Zonneveld, John-Paul _, Aswan

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