DETERMINING TEXTURAL AND GEOCHEMICAL ELEMENT CHARACTERISTICS OF SEAFLOOR SEDIMENT USING MULTIVARIATE ANALYSIS ALONG THE SIMEULUE SUB-BASIN, INDONESIA

Septriono Hari Nugroho,Purna Sulastya Putra

doi:10.17794/rgn.2020.4.7

Septriono Hari Nugroho, Purna Sulastya Putra

Open Access

https://doi.org/10.17794/rgn.2020.4.7

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Abstract

The Simeulue sub-basin is situated off north-western Sumatra between the outer arc and the mainlands. The sediment and geochemical element characteristics of basins are the important sedimentology variables to recognize the process of sediment deposition. However, the characteristics of the sediment and the geochemical elements in the Simeulue subbasin have not been well explained. This study aims to investigate the textural and geochemical elements characteristics of marine sediments and the distribution of these two variables to determine the sedimentary facies in the Simeulue sub-basin. Samples were taken from various depths in the sub-basin and collected during the 2017 Expedition of “Widya Nusantara” by using the “Baruna Jaya VIII” Research Vessel. The grain size trend analysis showed that the middle part of the basin was dominated by mud, while the edge of the basin near the island (mainland) was mostly dominated by coarser sediments. A geochemical element analysis was performed on each sample to observe the origin of the sediments. The results of these two analyses were subjected to multivariate statistics. This approach was selected because it is appropriate for determining the sedimentary facies and the depositional environments. Based on the multivariate analysis, the sedimentary facies in the Simeulue sub-basin was divided into five facies with similar sediment characteristics and depositional environments. These facies were deposited in the environment with low to medium energy.

Highlights

Granulometric analysis using Grain Size Trend Analysis (GSTA) is one of the proxies to determine the physical properties and sediment texture that are important for sediment transport and deposition study (Nugroho and Putra, 2018)
There are ten types of sediment identified in this study: coarse sand (CS), medium sand (MS), fine sand (FS), very fine sand (VFS), very coarse silt (VCST), coarse silt (CST), medium silt (MST), fine silt (FST), very fine silt (VFST) and clay (CL)
The medium silt sediment was dominant at bathymetry of more than 600 meters, while coarser sediments occurred at bathymetry of less than

Summary

Introduction

Granulometric analysis using Grain Size Trend Analysis (GSTA) is one of the proxies to determine the physical properties and sediment texture that are important for sediment transport and deposition study (Nugroho and Putra, 2018). Previous studies used the statistical parameters of the sediment grain (mean, sorting, skewness, kurtosis) to classify the depositional environment The multivariate statistical method is a powerful tool for analyzing and interpreting the depositional environment as it combines several different variables and avoids a single sample analysis (Chambers and Upchurch, 1979). This method was considered to be more effective as it facilitates the measurement and loss of efficiency produced (Nugroho et al, 2018). Some studies used multivariate methods in determining sedimentary facies in Southern Kuwait, Queensland (Australia) and Southern Utah (USA), as well as the Tarakan sub-basin (Indonesia) by Gischeler and Lomando (2005), Thoms et al (2007), Allen and Johnson (2010), and Nugroho et al (2018), respectively

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