Nawangsari, Putri (2020) Identifikasi Ketebalan Sedimen Dolina Karst Menggunakan Metode Tahanan Jenis Konfigurasi Wenner-Schlumberger di Desa Sekar, Pacitan. Other thesis, Institut Teknologi Sepuluh Nopember.
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Abstract
Dolina merupakan cekungan yang berada pada sela antar bukit di wilayah karst
yang memiliki sedimen lebih tebal dari daerah sekitarnya. Dolina menjadi
indikator adanya pelarutan yang signifikan akibat adanya manifestasi seperti
rongga di dalam tanah atau batuan. Ketebalan sedimen yang dimaksud dalam
penelitian adalah lapisan lunak yang berasal dari pelarutan batuan di sekitar
dolina dan terendapkan di area dolina maupun hasil pelarutan batuan dasar yang
disebabkan oleh air yang menembus melalui celah batuan secara terus-menerus.
Sedangkan batuan dasar yang dimaksud adalah lapisan batuan yang memiliki
nilai resistivitas lebih besar dan kontras resistivitasnya terlihat cukup jauh dengan
lapisan sedimen. Metode geolistrik resistivitas 2D dapat digunakan untuk
menggambarkan kondisi bawah permukaan secara lateral dan vertikal sehingga
digunakan dalam penelitian ini. Konfigurasi yang digunakan adalah Konfigurasi
Wenner-Schlumberger. Ketebalan sedimen dapat diidentifikasi dari kontras
resistivitas batuan yang dapat dilihat dari penampang hasil inversi. Penelitian
dilakukan di dolina sekitar Luweng Dawung, Desa Sekar, Pacitan. Terdapat 4
lintasan pengukuran yang sejajar, dengan panjang lintasan 140 m, 145 m, 145 m,
dan 155 m dominan berarah barat laut-tenggara. Data hasil pengukuran di
lapangan diolah dengan perangkat lunak Res2dinv. Berdasarkan geologi
regional, daerah penelitian termasuk ke dalam Formasi Wonosari yang tersusun
atas dominan batuan karbonat terumbu. Pada penampang hasil inversi setiap
lintasan terlihat persebaran nilai resistivitas yang menunjukkan litologi daerah
penelitian. Nilai resistivitas di bawah 20 Ωm diinterpretasi sebagai tanah penutup
dolina atau disebut sedimen dan nilai resistivitas di atas 20 Ωm diinterpretasi
sebagai batuan karbonat terumbu atau disebut bedrock. Selain itu, nilai
resistivitas antara 10-20 Ωm diinterpretasi sebagai rongga penuh air yang
letaknya berada di antara batuan karbonat terumbu. Ketebalan sedimen pada
lintasan NWG-1 sebesar 25 m, NWG-2 sebesar 16 m, NWG-3 sebesar 17 m, dan
NWG-4 sebesar 20 m. Hubungan ketebalan antar lintasan dapat diperoleh jika
data mencakup wilayah yang lebih luas
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Dolina is a basin between the hills in the karst region which has thicker
sediments than the surrounding area. Dolina is an indicator of significant
dissolution due to manifestations such as cavities in the soil or rocks. The
thickness of the sediment referred to in this study is the soft layer that originates
from the dissolution of rocks around the dolina and is deposited in the dolina
area as well as the results of the dissolution of bedrock caused by water that
penetrates through the rock gap continuously. While the bedrock is a rock layer
that has a greater resistivity value and the resistivity contrast looks quite far from
the sedimentary layer. 2D resistivity geoelectric method can be used to deliniate
subsurface conditions laterally and vertically so that it is used in this study. The
configuration used is Wenner-Schlumberger Configuration. Sediment thickness
can be identified from the contrast of rock resistivity which can be seen from the
cross section of the inversion results. The study was conducted in dolina around
Luweng Dawung, Sekar Village, Pacitan. There are 4 parallel lines, with a length
of 140 m, 145 m, 145 m, and 155 m dominantly directed northwest-southeast.
Data from measurements in the field are processed with Res2dinv software.
Based on regional geology, the study area is in Wonosari Formation which is
composed of dominant reef limestone. In the cross section of the inversion results
for each line, it is seen that the resistivity value distribution shows the lithology
of the study area. Resistivity values below 20 Ωm are interpreted as soil cover
dolina or called sediment and resistivity values above 20 Ωm are interpreted as
reef limestone or called bedrock. In addition, resistivity values between 10-20
Ωm are interpreted as cavities full of water that are located between reef
limestone. The thickness of the sediment in NWG-1 is 25 m, NWG-2 is 16 m,
NWG-3 is 17 m, and NWG-4 is 20 m. Thickness relationships between lines can
be obtained if the data covers a wider area.
| Item Type: | Thesis (Other) |
|---|---|
| Uncontrolled Keywords: | Dolina, Karst, Wenner-Schlumberger |
| Subjects: | G Geography. Anthropology. Recreation > GB Physical geography > GB600 Karst conservation. Q Science > QE Geology > QE571 Sedimentation and deposition. Sediment transport. Erosion. T Technology > T Technology (General) T Technology > TA Engineering (General). Civil engineering (General) |
| Divisions: | Faculty of Civil Engineering and Planning > Geophysics Engineering > 33201-(S1) Undergraduate Thesis |
| Depositing User: | Putri Nawangsari |
| Date Deposited: | 11 Aug 2020 03:42 |
| Last Modified: | 02 Jun 2023 14:45 |
| URI: | http://repository.its.ac.id/id/eprint/77412 |
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