Electronic Theses and Dissertation

ABSTRAK
Penelitian ini dilakukan di Kecamatan Muara Satu dan sekitarnya, Kota Lhokseumawe, Provinsi Aceh, yang secara regional termasuk ke dalam Cekungan Sumatera Utara. Penelitian bertujuan untuk mengetahui karakteristik litologi dan susunan stratigrafi, mengidentifikasi perubahan fasies, serta menginterpretasikan lingkungan pengendapan berdasarkan hasil pemetaan geologi dan analisis stratigrafi. Metode penelitian dilakukan melalui pemetaan geologi permukaan, pengamatan singkapan, pengukuran stratigrafi terukur, analisis geomorfologi, serta deskripsi litologi dan struktur sedimen. Hasil penelitian menunjukkan bahwa daerah penelitian tersusun oleh Formasi Seureula (Tps), Formasi Julurayeu (QTjr), Formasi Idi (Qpi), dan Endapan Aluvial (Qh). Litologi yang dijumpai berupa batulanau karbonatan, batupasir, batupasir karbonatan, batupasir konglomeratan, batugamping, dan endapan aluvial. Berdasarkan analisis geomorfologi, daerah penelitian dibagi menjadi beberapa satuan geomorfologi, yaitu perbukitan denudasional, dataran, dan satuan fluvial. Fasies sedimen yang berkembang terdiri atas fasies batupasir–batugamping perlapisan tebal, batupasir karbonatan–batugamping fosiliferus berlapis tipis, batupasir konglomeratan masif, dan batupasir konglomeratan bergradasi. Interpretasi lingkungan pengendapan menunjukkan bahwa Formasi Julurayeu diendapkan pada lingkungan laut dangkal hingga neritik, sedangkan Formasi Idi diendapkan pada lingkungan fluvial hingga transisi. Hubungan antar satuan batuan menunjukkan adanya ketidakselarasan berupa disconformity yang mencerminkan perubahan kondisi sedimentasi dan fluktuasi muka laut di wilayah penelitian.

Kata kunci: pemetaan geologi, stratigrafi, fasies, lingkungan pengendapan, Muara Satu, Cekungan Sumatera Utara.

ABSTRAC This research was conducted in Muara Satu District and surrounding areas, Lhokseumawe City, Aceh Province, which regionally belongs to the North Sumatra Basin. The study aims to determine lithological characteristics and stratigraphic sequences, identify facies changes, and interpret depositional environments based on geological mapping and stratigraphic analysis. The research methods included surface geological mapping, outcrop observation, measured stratigraphic section analysis, geomorphological analysis, and lithological as well as sedimentary structure descriptions. The results indicate that the study area is composed of the Seureula Formation (Tps), Julurayeu Formation (QTjr), Idi Formation (Qpi), and Alluvial Deposits (Qh). The identified lithologies consist of calcareous siltstone, sandstone, calcareous sandstone, conglomeratic sandstone, limestone, and alluvial deposits. Based on geomorphological analysis, the study area is divided into several geomorphological units, including denudational hills, plains, and fluvial units. The developed sedimentary facies consist of thick-bedded sandstone–limestone facies, thin-bedded calcareous sandstone–fossiliferous limestone facies, massive conglomeratic sandstone facies, and graded conglomeratic sandstone facies. Depositional environment interpretation indicates that the Julurayeu Formation was deposited in shallow marine to neritic environments, while the Idi Formation was deposited in fluvial to transitional environments. The relationship between rock units indicates the presence of disconformities reflecting changes in sedimentation conditions and sea-level fluctuations within the study area. Keywords: geological mapping, stratigraphy, facies, depositional environment, Muara Satu, North Sumatra Basin.