Arafura Sea is located between Papua and Australia as a part of Sahul Shelf. It is strongly influenced by ITF, ITCZ replacement, monsoon, and ENSO circulation that interplay with local mechanism. To understand the paleoceanographic parameter changes during Holocene, we conducted foraminiferal quantitative analysis from a 152 cm length sediment core (Aru–07), in every 10 cm interval. This sediment core was retrieved from 134o00’33.6” E, 5o55’51.59” S, by RV Geomarin 3 belongs to Marine Geological Institute. Geochronology of the sediment was reconstructed based on 2 AMS 14C age dates, analyzed on organic samples. We identified 129 species of benthic and 24 species of planktonic foraminifera that is dominated by planktonic specimens with average of 53.14%. Predominant species are Globigerina bulloides (16.16%), Globigerinoides ruber (11.18%), and Neogloboquadrina dutertrei (5.65%). Benthic type is dominated by genera Bolivina, Bulimina, and Uvigerina by 25.86% (average). This might suggest eutrophic condition associated with carbon-rich or low oxygen level (dysoxic) condition. Single linkage cluster analysis revealed 3 paleoenvironmental zones, are: Zone I: older than 3.9 kyr BP, characterized by depleted oxygen level and nutrient enrichment compared to that of younger zone. Zone II: 3.9 – 2 kyr BP, characterized by oxygen content enrichment and deeper thermocline layer, related to the sea level rise during more neutral or La Niña like condition. Zone III: younger than 2 kyr BP, represent shallower thermocline layer, higher productivity which might be related to upwelling, and dysoxic condition. Sea level might be declined that related to more El Niño like condition.Keywords: Paleoceanographic changes, upwelling, foraminiferal analysis, Arafura SeaLaut Arafura berlokasi di antara Papua dan Australia sebagai bagian dari Paparan Sahul. Kondisi iklim sangat dipengaruhi oleh ITF, perpindahan ITCZ, monsun, dan ENSO yang berinteraksi dengan mekanisme lokal. Untuk memahami perubahan parameter oseanografi selama Holosen, kami melakukan analisis kuantitatif mikrofauna foraminifera, yang dilakukan terhadap sebuah bor sedimen laut sepanjang 152 cm (Aru–07) pada interval setiap 10 cm. Bor sedimen bawah laut ini telah diambil pada posisi 134o00’33.6” BT, 5o55’51.59” LS, menggunakan kapal penelitian Geomarin 3, Pusat Penelitian Geologi Kelautan. Geokronologi sedimen berdasarkan 2 radiocarbon dating, dianalisis dari sampel organik pada sedimen. Teridentifikasi 129 spesies bentik dan 24 spesies plangtonik yang didominasi oleh plangtonik dengan persentase rata-rata 53.14%. Foraminifera Jenis–jenis yang dominan antara lain Globigerina bulloides (16.16%), Globigerinoides ruber (11.18%), dan Neogloboquadrina dutertrei (5.65%). Sedangkan jenis bentik didominasi oleh genus Bolivina, Bulimina, dan Uvigerina, dengan persentase rata–rata 25.86%. Hal tersebut kemungkinan menunjukkan kondisi eutropik yang berasosiasi dengan kondisi kaya karbon dan rendah level oksigen (disoxic). Analisis cluster single linkage menunjukkan tiga zona utama, yaitu: Zona I: lebih tua dari 3.9 kyr BP, dicirikan oleh relatif rendahnya kandungan oksigen dan lebih kaya kandungan nutrien. Zona II: 3.9 – 2 kyr BP, dicirikan oleh meningkatnya kandungan oksigen, dan mendalamnya lapisan termoklin, berkaitan dengan meningkatnya muka air laut ketika kondisi netral atau kondisi seperti La Niña. Zona III: lebih muda dari 2 kyr BP, merupakan zona dengan kondisi lapisan termoklin yang mendangkal, produktifitas meningkat yang kemungkinan berkaitan dengan upwelling, dan kondisi disoxic. Muka air laut kemungkinan turun, berasosiasi dengan kondisi seperti El Niño.Kata kunci: Perubahan paleoseanografi, upwelling, analisis foraminifera, Laut Arafura

Arafura Sea is influenced by several climatic dynamics, it is also a part of the coral triangle that provides most of marine organism diversity of the world. Therefore, this area is an important  waters that impact the climatic dynamic so its paleoceanographic changes need to be understood. For that, we analyzed the foraminiferal PB ratio from marine sediment core ARAFURA-24 with a core length of 179 cm, collected from 47.4 m water depth, combined with that of Aru-07, taken from 276 m water depth (core length 152 cm). Both sediment cores were collected from the Arafura Sea using a gravity corer on board Geomarin III. ARAFURA-24 was sub-sampling in every 20 cm interval, while Aru-07 had been prepared in every 10 cm interval. PB Ratio values from ARAFURA-24 and Aru-07 ranged from 0,56% - 7,43% and from 29,89% to 82,66%, respectively. The age model was reconstructed by 14C radiocarbon dating derived from organic sediment, combined with tie points of PB ratio records. The result indicates that ARAFURA-24 has been sedimented since the last 9.7 kyr BP. PB ratio records reveal three maximum sea level rises, which are before 7.4 kyr BP, at 5.86 kyr, and after 3 kyr BP (approximately at 2 kyr BP at Aru-07). From the age model reconstruction, sedimentation during the last 3 kyr BP was relatively slower than that in the older period. It can be concluded that the foraminiferal PB ratio during Late Holocene was not significantly impacted by sedimentation rate (hence detrital influence), in contrast, during Mid-Holocene detrital influence had more impact on the PB ratio record.

Gita member is part of Talang Akar Formation is known as hydrocarbon reservoir at Asri Basin, eastern part of South Sumatra. This formation consists of several depositional systems such as braided channel, meandering channel, fluvial-deltaic, and estuarine system. A channel system was an interesting system developed in the Asri Basin, however, to get the channel distribution in Asri Basin is quite challenging because the thickness of the channels caused its appearance is generally close or under seismic resolution, the existence of coal below our target also affects the impression of “S” sand on seismic data. In this study, spectral decomposition and RGB Blending have been successful to identify “S” sand. RGB Blending map is extracted from 15 Hz as low frequency, 45 Hz as middle frequency, and 75 Hz as high frequency. Our interpretation was applied at RGB Blending map and reveal the “S” sand is classified as a meandering channel depositional system with the main direction of the channel is Northeast – Southwest.

Foraminifera is very diverse and adaptive, both in its morphology and biology. It is a potential bioindicator to understand the ecological and physical conditions of the ancient and modern waters based on their distribution. It has been well confirmed that the abundance of foraminifera (as a fossil) in sediment can reflect the ocean conditions above (mixed layer to upper ocean) where it was deposited. Planktonic foraminifera however can be considered as passive particles, their movement is carried by ocean currents. In consequence, the foraminifera abundance may represent more wider ocean condition according to the ocean current pattern. This study aims to examine the role of ocean currents in the distribution of foraminifera in the Sulawesi Sea. Ten gravity core sediment samples from 73-3009 m water depth were retrieved by RV Geomarin III from the Marine Geological Institute, Indonesia. We conducted quantitative analysis, including calculation of abundance and cluster analysis. Two decades (1992-2012) of ocean current simulated data from the Hybrid Coordinate Ocean Model (HYCOM) is used in this analysis, extending from 115°E-140°E and 8°N-2°S. The result indicates that planktonic foraminifera is abundant in the Sulawesi Sea by 86.3%. There were several predominant planktonic species such as Globigerinoides ruber (22.6%), Globigerina bulloides (15.3%), and Neoglobuquadrina dutertrei (10.1%). The ocean current above the sample location is constantly moving eastward as a part of the NECC. The average currents velocity shows that foraminifera in sample site S-03 with depth 2064 m may originated from up to 1035 kilometers away from its recent location.