PALEOCLIMATOLOGY AND PALEOCEANOGRAPHY RECONSTRUCTION BASED ON MULTIPROXY ANALYSIS IN THE LATE PLEISTOCENE-HOLOCENE IN SIMEULUE WATERS, ACEH

• Main Author: Eka Mandiri Puteri, Winda
• Format: Theses
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/66946
• Institution: Institut Teknologi Bandung

Analysis of climate change and oceans in Simeulue waters, Aceh since the Late Pleistocene-Holocene were researched because this study area is in the tropical Indian Ocean which plays a role in the dynamics of the global climate change. The study area is on the eastern Indian Ocean which is affected by the variability of the atmosphere and oceans, called the Indian Ocean Dipole (IOD) and the monsoon system that occurs throughout the year. This study aims to reconstruct paleoclimate and paleoceanography and understand the effect and intensity of IOD since Late Pleistocene in the study area. A marine sediment core EW17-08 along 217 cm (94° 46’ 43” longitude and 2° 29’ 47” latitude) was retrieved from a depth of 2.811 m in western of Simeulue Island. Multiproxy were used for analysis of paleoclimate and paleoceanography, there are foraminifera analysis, radiocarbon dating, Loss on Ignition (LoI), chemical elements (XRF) analysis, and grainsize analysis. Based on this multiproxy, further analysis is carried out such as sea surface temperature (SST) analysis using Modern Analogue Technique (MAT) method, thermocline analysis using the abundance of thermocline dweller, cold climate analysis using the abundance of subtropical foraminifera and percentage of carbon, upwelling analysis using the abundance of Globigerina bulloides, rainfall intensity analysis based on sediment input and weathering parameters, current intensity analysis using the abundance of Cibicides sp., and low oxygen level analysis using the abundance of Uvigerina sp. and Bulimina sp. The Late Pleistocene period showed relatively cooler condition than the Holocene based on SST summer (June, July, and August), abundance of subtropical foraminifera, and increase in the percentage of carbon. In addition, there was an increase in upwelling intensity (aged 15.140-9.220 BP) due to strengthening of the southeast monsoon intensity which pushed the current to move northwest. In the study area, the result of paleoclimate and paleoceanography reconstruction are divided into 4 periods namely Period 1 (age 21.300-17.140 BP), which is warm and high rainfall intensity, is associated with deglaciation, Period 2 (age 15.140- 11.040 BP), which is cold and low rainfall intensity, is associated with Oldest Dryas, Bølling Interstadial, Older Dryas, Allerød Interstadial, and Younger Dryas, Period 3 (age 11.040-4.110 BP), which is warm and high rainfall intensity, is associated with Preboreal-Boreal, 8.2k event, Holocene Thermal Maximum, and 4.2k event, and last Period 4 (age 4.110-0 BP), which is cold and low rainfall intensity, is associated with Subboreal, Warm Period, and Little Ice Age. Based on the thermocline depth in the study area, the IOD intensity can be determined to be negative or positive phase. Period 1 (age 21.300-17.140 BP) and Period 3 (age 11.040-4.110 BP) the positive phase IOD condition were more intense, while Period 2 (age 15.140- 11.040 BP) and Period 4 (age 4.110-0 BP) the negative phase IOD condition were more intense. This condition is different from SST and rainfall intensity in the study area. This is thought to be due to the strengthening of the northwest monsoon during the Early-Middle Holocene and southward movement of Intertropical Convergence Zone (ITCZ) since LGM (~21.000 BP).