Electronic Theses and Dissertation

Secara geografis daerah penelitian terletak di Pulau Breueh pada koordinat 5° 42' 9.60"N – 5° 40' 0.02"N LU dan 95° 4' 49.48"E – 95° 8' 1.78"E BT dengan luas area 25 km2. Secara administratif terletak di Kecamatan Pulo Aceh, Kabupaten Aceh Besar, Provinsi Aceh. Pemetaan geologi dilakukan di daerah penelitian yang memiliki 2 formasi yaitu Formasi Gunungapi Breueh (Tlvb), Formasi Peunasu (Tlp), dan 1 endapan yaitu Aluvium (Qh). Penelitian bertujuan untuk mengetahui kondisi geologi serta menganalisis karakteristik airtanah pada daerah penelitian yang berupa pulau kecil dan tergolong rentan mengalami intrusi air asin dengan metode pemetaan geologi, analisis petrografi, pengukuran muka airtanah, penentuan batas interface antara air tawar dengan air asin, pengujian sifat fisik airtanah mencakup nilai pH (potential of hydrogen), DHL (daya hantar listrik), dan TDS (total dissolved solids), serta analisis geokimia airtanah. Pemetaan geologi dengan total 72 titik amat terbagi dalam 4 satuan batuan yaitu satuan basal, satuan lapili – tuff, satuan serpih, satuan gamping terumbu dan 1 endapan yaitu endapan pasir pantai. Penamaan ketiga batuan beku formasi Gunung Api Breueh yang didapatkan dari analisis petrografi berupa Basal, batuan piroklastik formasi Gunung Api Breueh yang didapatkan dari analisis petrografi berupa Lapili – Tuff Litik – Kristal, batuan sedimen klastik formasi Peunasu yang didapatkan dari analisis petrografi berupa Mudrock, dan batuan sedimen non-klastik formasi Peunasu yang didapatkan dari analisis petrografi berupa Floatstone. Hasil analisis sifat fisik airtanah pH kisaran 6 – 9 tergolong aman. Pengujian TDS sumur GGP 1 Moderately Saline dan GGP 2 Slightly Saline. Pengujian DHL sumur SRP 1, SRP 2, SRP 4, BS 1, BSK 1, BSK 2, PL 1, PL 4, LPY 1, LPY 3, dan LPY 4 sebagai Fresh – Brackish Water, serta sumur SRP 3, GGP 1, GGP 2, UP 1, dan LPY 2 sebagai Saline Water. Analisis geokimia parameter intrusi air laut sumur GGP 1 Intrusi Sangat Tinggi, UP 1 Intrusi Sedikit, LPY 2 Intrusi Sedang, sedangkan sumur LP 2, UP 1, dan PL 2 Tanpa Intrusi. Analisis diagram stiff dan piper sumur LP 2, BSK 3, dan PL 2 dominan Kalsium (Magnesium) Bikarbonat dan UP 1 tipe campuran. Sumur GGP 1 dan LPY 2 dominan Kalsium Klorida.

Geographically, the research area is located on Breueh Island at coordinates 5° 42' 9.60"N – 5° 40' 0.02"N LU and 95° 4' 49.48"E – 95° 8' 1.78"E BT with an area of 25 km2. Administratively, it is located in Pulo Aceh District, Aceh Besar Regency, Aceh Province. Geological mapping was carried out in the study area, which has two formations, namely the Breueh Volcano Formation (Tlvb) and the Peunasu Formation (Tlp), and one deposit, namely Alluvium (Qh). The study aims to determine the geological conditions and analyze the characteristics of groundwater in the study area, which is a small island and is prone to saltwater intrusion, using geological mapping, petrographic analysis, groundwater level measurement, determination of the interface between fresh water and salt water, testing of the physical properties of groundwater, including pH (potential of hydrogen), EC (electrical conductivity), and TDS (total dissolved solids), as well as geochemical analysis of groundwater. Geological mapping with a total of 72 points is divided into 4 rock units, namely the basalt unit, lapilli-tuff unit, shale unit, coral limestone unit, and 1 deposit, namely coastal sand deposits. The naming of the three igneous rocks of the Breueh Volcano formation obtained from petrographic analysis are Basal, pyroclastic rocks of the Breueh Volcano formation obtained from petrographic analysis in the form of Lapilli – Lithic – Crystalline Tuff, clastic sedimentary rock of the Peunasu Formation obtained from petrographic analysis in the form of Mudrock, and non-clastic sedimentary rock of the Peunasu Formation obtained from petrographic analysis in the form of Floatstone. The results of the physical analysis of groundwater pH in the range of 6 – 9 are classified as safe. TDS testing of wells GGP 1 (Moderately Saline) and GGP 2 (Slightly Saline). EC testing of wells SRP 1, SRP 2, SRP 4, BS 1, BSK 1, BSK 2, PL 1, PL 4, LPY 1, LPY 3, and LPY 4 as Fresh – Brackish Water, and wells SRP 3, GGP 1, GGP 2, UP 1, and LPY 2 as Saline Water. Geochemical analysis of seawater intrusion parameters shows that well GGP 1 has Very High Intrusion, UP 1 has Slight Intrusion, LPY 2 has Moderate Intrusion, while wells LP 2, UP 1, and PL 2 have No Intrusion. Analysis of the stiff and piper diagrams of wells LP 2, BSK 3, and PL 2 shows a dominant Calcium (Magnesium) Bicarbonate type, while UP 1 is a mixed type. Wells GGP 1 and LPY 2 are dominated by Calcium Chloride.