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All Journal JGE (Jurnal Geofisika Eksplorasi) Jurnal Geosains dan Teknologi Bulletin of Geology
Ardi, Ryan Dwi Wahyu
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Earth & Planetary Sciences Energy Engineering Environmental Science

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BIOSTRATIGRAFI DAN PALEOEKOLOGI WILAYAH LEPAS PANTAI BARAT DAYA SUMBA SEJAK PLEISTOSEN AKHIR BERDASARKAN KUMPULAN FORAMINIFERA PLANKTONIK Ardi, Ryan Dwi Wahyu; Maryunani, Khoiril Anwar; Yulianto, Eko; Putra, Purna Sulastya; Nugroho, Septriono Hari
Bulletin of Geology Vol 3 No 2 (2019): Bulletin of Geology
Publisher : Fakultas Ilmu dan Teknologi Kebumian (FITB), Institut Teknologi Bandung (ITB)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/bull.geol.2019.3.2.3

Abstract

Foraminifera are microfaunas/microfossils that frequently applied in geology especially for biostratigraphy and paleoecological analysis. This research aim to create biozonation and paleoecological analysis in the region off the southwest coast of Sumba based on planktonic foraminiferal assemblages. This region heavily affected by northwest monsoon – southeast monsoon shift and located next to one of the ITF’s outflow paths (Ombai Strait – Savu Sea) which eventually form its ecological condition. A 235 cm long deep sea sediment core coded ST08 will be used as research material. Foraminifera specimens were determined quantitatively by observing approximately 300 specimens for each split. Each taxon determined from that part then calculated for each individu that was found while different taxa determined from other splits are considered to be one. Biozonation was determined based on either Blow biozonation or Bolli and Saunders biozonation. One zone was obtained based on Blow biozonation which is N23 zone, equal to Pleistocene – Holocene. Two zones were determined based on Bolli and Saunders biozonation which are Globigerinella calida – Clavarotella bermudezi zone (below 147 cm depth), equal to Late Pleistocene and Globorotalia fimbriata zone (0 – 147 cm depth), equal to Holocene. Paleocological analysis focused on the thermocline depth parameter inferred from the relative abundance of thermocline dweller taxa that consist of Neogloboquadrina dutertrei, Puleniatina obliqueloculata, and Globorotalia menardii. Themocline dweller abundance were relatively higher during Pleistocene (49,76 – 75,66%, average 60,01%), indicating shallower thermocline (eutropic condition) while during Holocene its abundance relatively lower (33,90 – 57, 17%, average 45,77%), which indicated thermocline deepening (more oligotropic condition). Those conditions were related to the southeast monsoon domination during Pleistocene (stronger ITF) before its weakening on Holocene which induced northwest monsoon strengthening (weaker ITF).
Mikrofasies Batugamping Formasi Sentolo, Daerah Karangsari, Kulon Progo, Daerah Istimewa Yogyakarta Nurhidayah, Efrilia Mahdilah; Akmaluddin, Akmaluddin; Ardi, Ryan Dwi Wahyu; Maulida, Nisa' Khofiyan; Sholichah, Wahyunia Mar'atus
Jurnal Geosains dan Teknologi Vol 8, No 1 (2025)
Publisher : Universitas Diponegoro

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.14710/jgt.8.1.2025.49-59

Abstract

Penelitian mikrofasies batugamping Formasi Sentolo dilakukan di daerah Karangsari, Kulon Progo, Yogyakarta. Formasi Sentolo terdiri dari batugamping dan perselingan napal-batugamping. Penelitian ini bertujuan untuk mengetahui variasi mikrofasies dan lingkungan pengendapanpada batugamping di Formasi Sentolo menggunakan analisis petrografi. Analisis dilakukan terhadap sepuluh sampel batugamping menggunakan metode petrografi untuk menginterpretasikan tipe mikrofasies dan lingkungan pengendapan, dengan delapan sampel di antaranya juga dianalisis foraminifera bentik besar untuk menentukan umur relatif. Karakteristik yang paling menonjol pada hasil analisis komposisi batuan adalah melimpahnya fragmen fosil foraminifera bentik besar dan alga. Analisis foraminifera bentik besar pada lokasi penelitian menunjukan umur Miosen (Te5–Tf), berdasarkan kehadiran asosiasi spesies Operculinoides panamensis, Amphistegina bowdenensis, Amphistegina lessonii, Operculina sp., dan Elphidium sp. Dua mikrofasies utama berhasil diidentifikasi, yaitu fasies foraminiferal wackestone yang mewakili lingkungan laut dalam toe-of-slope (FZ3), dan fasies amphistegina grainstone/ packstone yang mencerminkan lingkungan open marine (FZ7) pada bagian backreef. Perubahan lingkungan pengendapan dari laut dalam menuju laut dangkal mengindikasikan adanya pengaruh fluktuasi muka air laut serta kontrol morfologi sisa gunungapi purba terhadap sistem pengendapan karbonat di Pegunungan Kulon Progo.
LAST GLACIAL MAXIMUM – HOLOCENE RAINFALL SHIFTS IN THE WESTERN SAVU STRAIT BASED ON GEOCHEMICAL PROXIES Ardi, Ryan Dwi Wahyu; Aswan, Aswan; Maryunani, Khoiril Anwar; Yulianto, Eko; Putra, Purna Sulastya; Nugroho, Septriono Hari; Nurhidayah, Efrilia Mahdilah
JGE (Jurnal Geofisika Eksplorasi) Vol. 11 No. 2 (2025)
Publisher : Engineering Faculty Universitas Lampung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.23960/jge.v11i2.493

Abstract

The Indo-Pacific Warm Pool significantly influences global atmospheric circulation, with tropical rainfall patterns highly sensitive to glacial–interglacial climate changes. During the Last Glacial Maximum (LGM), approximately 26,500 years before present, lower insolation, expanded ice sheets, and reduced sea levels weakened the Australian–Indonesian Monsoon (AIM) due to a southward shift of the Intertropical Convergence Zone (ITCZ). In contrast, the Holocene period experienced intensified monsoon systems and increased precipitation. However, high-resolution hydroclimate reconstructions from the western Savu Strait remain scarce. This study reconstructs rainfall variability from the LGM to the Holocene using geochemical proxies from sediment core ST10 (at 1 cm interval), located in the western Savu Strait. Three elemental ratios (Ti/Ca, K/Ca, and Rb/Sr) from X-ray fluorescence (XRF) core scanning were used to indicate terrigenous input, chemical weathering, and fluvial discharge. The age model was established using radiocarbon dating and stable isotope alignment with the Greenland ice core δ¹⁸O record. Log-transformed elemental ratios reveal four intervals of increased rainfall: the LGM, Heinrich Event 1 (HE1), Younger Dryas to Early Holocene, and the Late Holocene. These periods are characterized by elevated Ti/Ca, K/Ca, and Rb/Sr values, suggesting enhanced monsoonal rainfall and continental runoff. Conversely, lower proxy values during the Early Deglaciation, Bølling–Allerød, and Mid-Holocene indicate drier climatic conditions. These patterns align with regional proxy records from southwest Sumba and the Timor Sea, confirming the reliability of elemental ratios in reconstructing past hydroclimate variability. This study provides the first continuous record of rainfall shifts in the western Savu Strait from the LGM to Holocene and contributes to understanding long-term monsoon dynamics in southeastern Indonesia, highlighting the complex response of tropical hydroclimate to global climate forcing.
Co-Authors Akmaluddin Akmaluddin Aswan Aswan EKO YULIANTO Maryunani, Khoiril Anwar Maulida, Nisa' Khofiyan Nurhidayah, Efrilia Mahdilah Purna Sulastya Putra, Purna Sulastya Septriono Hari Nugroho Sholichah, Wahyunia Mar'atus