Studi Kasus Karateristik Lumpur Sidoarjo 15 Tahun Setelah Kemunculan

Abstract

This research was conducted in an area of ±6 km2 which is located in the Sidoarjo Mud area, located in the south of Sidoarjo Regency, Porong, East Java. The Sidoarjo mudflow released a volume of ±60,000 m3 - ±80,000 m3 daily and still gushing to this day. By studying the mud content further, we can better understand the changes in the material characteristics of the Sidoarjo Mud for mitigation purposes and to calculate the economic potential of the mud material. The study began with sampling of surface mud at 32 points scattered around the area of the mudflow point. The samples were then prepared using a combination of dry sieving and wet sieving methods. After preparation, the samples were then processed using the Grain Size Analysis method to determine the proportion of mud grain size, the microscope observation method for the purposes of analyzing the content of foraminifera fosils and minerals with a mesh size of 120 – 250 mesh in the mud as an effort to identify the materials that make up the mud, and the XRD analysis method to determine mineralogy of the mud. The comparison results show a large percentage of the mud grain size below 62 microns. Observations of foraminifera fosils indicate the possible origin of the formation from the Sidoarjo Mud. XRD data analysis also showed some similarities with the comparison data, such as smectic clay minerals and monmorilonite which were the most dominant clay minerals, and minerals such as and Sulfur showed influence of marine and volcanic depositional environments.The location of the Sidoarjo Mud area is above the Watusokek Fault line which extends to the Arjuno-Welirang mountain complex. Penelitian dimulai dengan pengambilan sampel lumpur permukaan di 32 titik yang tersebar disekitar area titik semburan lumpur. Sampel tersebut kemudian dipreparasi menggunakan kombinasi metode dry sieving dan wet sieving. Setelah preparasi, sampel kemudian diproses menggunakan metode Grain Size Analysis untuk menentukan proporsi ukuran butir lumpur, metode observasi mikroskop untuk keperluan analisis kandungan fosil foraminifera dan mineral ukuran mesh 120 – mesh 250 pada lumpur sebagai upaya identifikasi material penyusun lumpur, dan Metode analisis XRD untuk menentukan mineralogi dari lumpur tersebut. Hasil perbandingan menunjukkan persentase besar dari ukuran butir lumpur dibawah 62 mikron. Observasi fosil foraminifera menunjukkan kemungkinan asal formasi dari Lumpur Sidoarjo. Analisis data XRD juga menunjukkan beberapa kemiripan dengan data pembanding, seperti mineral lempung smektik dan monmorilonit merupakan mineral lempung yang paling dominan, serta mineral seperti sulfur menunjukkan pengaruh lingkungan pengendapan laut dan vulkanik.. Dengan lokasi kawasan Lumpur Sidoarjo berada diatas jalur sesar Watusokek yang memanjang hingga kompleks pegunungan Arjuno-Welirang.