Electronic Theses and Dissertation

ABSTRAK


Pemetaan geologi dilakukan di Kecamatan Woyla dan sekitarnya, Kabupaten Aceh Barat, Provinsi Aceh dengan luas blok pemetaan 25 km². Koordinat lokasi pemetaan terletak pada 96° 00’ 37.1” - 96° 03’ 54.6” LU dan 4° 29’ 42.5” - 4° 27’ 28.6” BT. Kondisi geologi regional pada lokasi penelitian terdiri dari Formasi Tutut tersusun dari beberapa litologi batuan yang berupa batuan sedimen seperti batulumpur, batupasir, batulumpur lignit, lapisan batuan sedimen yang mendasari batubara (seat rock) dan konglomerat yang terlitifikasi buruk berumur Pliosen – Plistosen. Kemudian Endapan Alluvium (Qh) terdiri dari kerikil, pasir dan lempung dengan umur Holosen. Penelitian dilakukan bertujuan untuk mengetahui sebaran batuan, keadaan geomorfologi, karakter sedimentologi, genesa litologi serta sejarah geologi dan rekonstruksi pengendapan yang lebih terukur. Hal ini menjadi factor peneliti untuk melakukan pemetaan dan kajian stratigrafi pada daerah penelitian ini. Metode yang dilakukan pada penelitian ini adalah metode pemetaan geologi, analisis sayatan tipis dan metode MS (Measure Section) untuk mengkaji stratigrafi daerah penelitian secara terukur. Hasil akhir dari penelitian berupa peta geologi, peta lintasan, peta geomorfologi dan kolom/penampang stratigrafi yang terukur dari data setiap singkapan. Kolom Stratigrafi yang terukur tersebut akan menggambarkan bagaimana pengelompokkan, hubungan, dan genesa antar batuan. Hasil dari penelitian ini diharapkan dapat menjadi sebuah referensi studi geologi yang mungkin akan bermanfaat bagi peneliti lainnya. Hasil yang diperoleh pada lokasi penelitian terdiri dari 5 satuan bentang alam yaitu Unit bentang alam perbukitan denudasional (D1), Unit dataran denudasional (D5), Unit bentang alam tubuh sungai (F1), Unit dataran banjir dan saluran sungai mati tanpa air (F3), Unit tanggul sungai, pematang alluvial dan zone pointbar (F4). Stratigrafi lokasi penelitian dari tua ke muda terdiri dari satuan Batulanau Tutut, satuan Batupasir Tutut, satuan Batu Konglomerat Tutut dan Endapan Alluvial. Berdasarkan analisis penampang stratigrafi terukur pada Formasi Tutut (QTt), didapat 6 asosiasi fasie yang terdiri dari fasies Gradded Bedding Medium Sandstone yang terendapkan pada estuary (fluvial dominated), Thick-Bedded Finesandstone And Interbadded Siltstone With Lignit yang terendapkan pada estuary (fluvial dominated), Gradded Bedding Sandstone yang terendapkan pada fluvial floodplain, Gradded Bedding with Thick Badded Mediumsandstone terendapkan pada fluvial channel bar, Gradded Bedding with Thick Badded Finesandstone terendapkan pada fluvial floodplain atau crevasse splay, Thick Badded Horizontaly Conglomerat terendapkan pada fluvial braided river. Lingkungan pengendapan pada Formasi Tutut (QTt) mengalami perubahan dari estuari didominasi fluvial yang dipengaruhi oleh pasang surut ke lingkungan pengendapan fluvial berupa sungai.


Kata Kunci: Pemetaan Geologi, Kolom/Penampang Stratigrafi, Measure Section, Formasi Tutut (QTt)

ABSTRACT Geological mapping was conducted in Woyla District and its surroundings, West Aceh Regency, Aceh Province, covering a mapping block area of 25 km². The coordinates of the mapping location are 96° 00’ 37.1” - 96° 03’ 54.6” E and 4° 29’ 42.5” - 4° 27’ 28.6” N. The regional geological conditions at the research location consist of the Tutut Formation, composed of various rock lithologies, including sedimentary rocks such as mudstone, sandstone, lignite mudstone, coal-bearing sedimentary layers (seat rock), and poorly lithified conglomerate, dating from Pliocene to Pleistocene. Subsequently, Alluvial Deposits (Qh) consist of gravel, sand, and clay, dating from the Holocene. The research was carried out to determine rock distribution, geomorphological conditions, sedimentological characteristics, lithological genesis, geological history, and more quantifiable depositional reconstruction. This was a motivating factor for the researchers to conduct mapping and stratigraphic studies in this research area. The methods used in this study were geological mapping, thin section analysis, and the Measured Section (MS) method to quantitatively study the stratigraphy of the research area. The final results of the study are in the form of geological maps, traverse maps, geomorphological maps, and measured stratigraphic columns/sections derived from data from each outcrop. These measured stratigraphic columns will illustrate the grouping, relationships, and genesis between rocks. The results of this research are expected to serve as a reference for geological studies that may be beneficial for other researchers. The results obtained at the research location consist of five landform units: Denudational Hill Landform Unit (D1), Denudational Plain Unit (D5), River Body Landform Unit (F1), Floodplain and Dry Paleochannel Unit (F3), and River Levee, Alluvial Ridge, and Point Bar Zone Unit (F4). The stratigraphy of the research location from oldest to youngest consists of the Tutut Siltstone unit, Tutut Sandstone unit, Tutut Conglomerate unit, and Alluvial Deposits. Based on the analysis of the measured stratigraphic sections in the Tutut Formation (QTt), six facies associations were identified, consisting of: Graded Bedding Medium Sandstone facies deposited in an estuary (fluvial-dominated), Thick-Bedded Fine Sandstone and Interbedded Siltstone with Lignite deposited in an estuary (fluvial-dominated), Graded Bedding Sandstone deposited on a fluvial floodplain, Graded Bedding with Thick-Bedded Medium Sandstone deposited in a fluvial channel bar, Graded Bedding with Thick-Bedded Fine Sandstone deposited on a fluvial floodplain or crevasse splay, and Thick-Bedded Horizontally Conglomerate deposited in a fluvial braided river. The depositional environment of the Tutut Formation (QTt) changed from a fluvial-dominated estuary influenced by tides to a fluvial depositional environment, specifically a river. Keywords : Geological Mapping, Stratigraphic Column/Section, Measured Section, Tutut Formation (QTt).