Electronic Theses and Dissertation

Penelitian ini terletak pada koordinat 5°11'24"–5°13'48" LU dan 97°00'36"–97°03'00"
BT di Kecamatan Nisam dan sekitarnya, Kabupaten Aceh Utara, Provinsi Aceh,
dengan luas wilayah penelitian sekitar 25 km². Formasi Idi terdiri oleh satuan batuan
sedimen Kuarter yang berkembang di wilayah pesisir Aceh Utara, namun penelitian
mengenai karakteristik sedimen dan lingkungan pengendapannya berdasarkan analisis
granulometri masih terbatas. Penelitian ini bertujuan untuk mengetahui kondisi geologi
daerah penelitian serta menginterpretasikan lingkungan pengendapan batupasir pada
Formasi Idi berdasarkan analisis granulometri. Metode penelitian dilakukan melalui
pemetaan geologi yang meliputi pengamatan geomorfologi, stratigrafi, litologi, serta
analisis granulometri menggunakan metode ayakan (sieve analysis) yang selanjutnya
diolah dengan parameter statistik Folk dan Ward (1957) dan diinterpretasikan
menggunakan Diagram Friedman. Hasil penelitian menunjukkan bahwa daerah
penelitian tersusun atas lima satuan batuan, yaitu Satuan Batupasir Tufaan Formasi
Julurayeu, Satuan Batupasir Formasi Julurayeu, Satuan Batugamping Terumbu
Formasi Idi, Satuan Batupasir Formasi Idi, dan Endapan Alluvium. Selain itu, daerah
penelitian memiliki tiga satuan bentang alam, yaitu satuan denudasional (D1 dan D5),
satuan struktural (S1), dan satuan fluvial (F1 dan F3). Hasil analisis granulometri
terhadap lima sampel batupasir Formasi Idi menunjukkan ukuran butir berkisar antara
pasir sangat halus hingga pasir sedang dengan tingkat sortasi sangat baik hingga
sedang, nilai skewness didominasi positif, dan seluruh sampel memiliki nilai kurtosis
very platykurtic. Hasil plotting pada Diagram Friedman menunjukkan seluruh sampel
dominan berada pada zona mainly beach sands. Berdasarkan integrasi hasil analisis
granulometri, data stratigrafi, dan kondisi geologi regional, lingkungan pengendapan
Formasi Idi di daerah penelitian diinterpretasikan berada pada lingkungan marine to
littoral dengan karakteristik beach sands.
Kata kunci: Pemetaan geologi, granulometri, Diagram Friedman, lingkungan
pengendapan, Formasi Idi.

The study area is located between coordinates 5°11'24"–5°13'48" N and 97°00'36"–97°03'00" E in Nisam District and its surroundings, North Aceh Regency, Aceh Province, covering an area of ​​approximately 25 km². The Idi Formation consists of Quaternary sedimentary rock units distributed across the coastal region of North Aceh; however, research regarding its sediment characteristics and depositional environments based on granulometric analysis remains limited. This study aims to determine the geological conditions of the area and interpret the depositional environment of the Idi Formation sandstone using granulometric analysis. The research methodology involved geological mapping—encompassing geomorphological, stratigraphic, and lithological observations—and granulometric analysis via the sieve method; the resulting data were processed using Folk and Ward (1957) statistical parameters and interpreted using the Friedman Diagram. The results indicate that the study area comprises five rock units: the Tuffaceous Sandstone Unit of the Julurayeu Formation, the Sandstone Unit of the Julurayeu Formation, the Reef Limestone Unit of the Idi Formation, the Sandstone Unit of the Idi Formation, and Alluvial Deposits. Additionally, the area features three landform units: denudational units (D1 and D5), a structural unit (S1), and fluvial units (F1 and F3). Granulometric analysis of five sandstone samples from the Idi Formation reveals grain sizes ranging from very fine to medium sand, with sorting degrees ranging from very well-sorted to moderately sorted; skewness values ​​are predominantly positive, and all samples exhibit "very platykurtic" kurtosis. Plotting on the Friedman Diagram shows that all samples fall predominantly within the "mainly beach sands" zone. Based on the integration of granulometric analysis results, stratigraphic data, and regional geological conditions, the depositional environment of the Idi Formation in the study area is interpreted as ranging from marine to littoral, characterized by beach sands. Keywords: Geological mapping, granulometry, Friedman diagram, depositional environment, Idi Formation.