Karakterisasi Kawasan Karst di Desa Sulkam Kabupaten Langkat Sumatera Utara

Abstract

Research has been done to characterize the karst area in the village Sulkam Langkat district of North Sumatra to obtain resistivity contour laterally and vertically, minerals, elements and morphology, compressive strength as well as search for lau Ketuken loss. Geo-electiric resistivity contour is gained by the Wenner-Schlumberger configuration to identify the rock layers in the surface area. The samples of the rocks are analyzed by using XRD and EDX, in order to determine the kind of rock for each layer and the mineral properties, respectively. Meanwhile, SEM and thin slice are employed to observe the rock morphology. Furthermore, compressive strength of the rock is tested using compression machine. Resistivity contour laterally at a depth of 1,25 m to 30 m is in the form of a layer of limestone rocks, soil and clay surfaces. The limestone rocks are especially founded in the western part of the village Sulkam. Ketuken lau rock layers are made up from sandstone clay, clay stone, sandstone and limestone, redirects the water and reservoir so that lau Ketuken lost on the surface. Resistivity contour vertically on a horizontal track surface layers of soil are mediated by limestone. The limestone and a layer of soil and clay form a cavity. Resistivity contour vertically is in the form of limestone and clay. There is soil is among the clays. The Southern part of lau Ketuken area is founded some layers of limestone, and a cavity. The mineral content of the rocks consist of CaCO3 with the composition of 96 wt % in average (from 74,1% - 100 wt%). The properties of rock elements are in the form of mineral calcite rock which is consist of Ca, C and O, as well as impurities Si. The average composition of the limestone samples are O = 46,56%; Ca = 27,37%; C = 25,94%; Si = 0,34%. Tight textures of the rock morphology is fine-grained and coarse which have grain size 2.201 μm to 4.150 μm. Its constituent are micrit rock, calcite and bioclas. The mechanical properties of limestone based on SII 0378-80 are soft limestone category. It is used to apply as a cover of the floor or pavement.

Telah di lakukan penelitian untuk mengkarakterisasi kawasan karst di desa Sulkam kabupaten Langkat Sumatera Utara untuk memperoleh kontur resistivitas secara lateral dan vertikal, mencari ketidak tampakan lau Ketuken, kandungan mineral, unsur dan morfologi serta kuat tekan batu gamping. Metode yang digunakan adalah dengan memadukan metode geolistrik konfigurasi Wenner-Schlumberger untuk mengetahui perlapisan batuan yang ada di bawah permukaan. Sampel batuan singkapan diuji dengan XRD untuk mengetahui kandungan mineral, EDX untuk menentukan kandungan unsur batuan, SEM dan sayatan tipis untuk morfologi batuan, serta kuat tekan batuan menggunakan compression machine. Kontur resistivitas secara lateral pada kedalaman 1,25 m hingga 30 m berupa lapisan batuan batu gamping, tanah permukaan dan lempung. Batu gamping terutama di bagian Barat desa Sulkam. Lapisan batuan lau Ketuken berupa batuan pasir lempung, batu lempung, batu pasir dan batu gamping yang bersifat meloloskan dan sebagai reservoar sehingga lau Ketuken tidak tampak di permukaan. Kontur resistivitas secara vertikal pada lintasan horizontal terdapat lapisan tanah permukan diantarai batu gamping, batu gamping, dan lapisan tanah serta lempung. Kontur resistivitas secara vertikal berupa batu gamping dan lempung, tanah hadir diantara lempung. Bahagian Selatan dekat dengan daerah lau Ketuken memiliki lapisan batu gamping dan terdapat rongga. Kandungan mineral batuan diperoleh CaCO3 dengan komposisi 74,1 wt.% - 100 wt.% dengan rata-rata 96 wt %. Kandungan unsur batuan berupa mineral kalsit dengan unsur Ca, C dan O dan pengotor Si. Komposisi rata-rata pada sampel batu gamping O = 46,56%; Ca = 27,37 %; C = 25,94%; Si = 0,34% . Morfologi batuan dengan tekstur rapat, berbutir halus dan kasar dengan ukuran butir 2.201 μm sampai 4.150 μm dengan penyusun batuan mikrit, kalsit dan bioklas. Sifat mekanik batu gamping berdasarkan SII 0378-80 termasuk batu gamping lunak dan digunakan sebagai penutup lantai atau trotoar.