Karakterisasi Kawasan Karst Di Desa Sulkam Kabupaten Langkat Sumatera Utara

viii

KARAKTERISASI KAWASAN KARST DI DESA SULKAM

KABUPATEN LANGKAT SUMATERA UTARA

ABSTRAK

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 CaCO

3

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.

ix

CHARACTERIZATION OF KARST AREAS IN VILLAGE SULKAM

LANGKAT NORTH SUMATRA

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 CaCO

3

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 g

rain 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.