Abstract

Administratively, the research area covers two districts, Wonosari Sub-district and Dulupi Sub-district, Boalemo District, Gorontalo Province. Based on the physiography of the Gorontalo region, the research area which is included in the southern mountain zone of Bone-Tilamuta-Modello generally consists of ancient volcano-sedimentary rock formations in Gorontalo, the Eocene-Oligocene. The purpose of this geological research is to discover the geological order that developed in the area of Dimito and surrounding are as covering several aspect such as geomorphology, stratigraphy, geological structure, and geological history. The result shows that the geomorphology of the research area divided into three geomorphic units, namely the units of the Alluvial Plain, Volcanic Hills, and Denudasional Hills. Stratigraphy of the research area divided into five types of units sorted from the early Miocene to the Holocene, i.e., Lava Basal Dimito (Early Eocene), Wackestone Dimito (Early Eocene), Andesit Kalidingin (Middle Miocene), Granodiorite Bualo (Middle Pliocene), and Alluvial Buaolo (Recen). Geological structures that work on the location of the research area relatively trend from northeast-southwest to northwest-southeast. Fault working on the location of the research area from the data processing consists of Normal Left Slip Fault Kalidingin and Lag Left Slip Fault Bualo.

Highlights

  • The research area covers two districts, Wonosari Sub-district and Dulupi Sub-district, Boalemo District, Gorontalo Province

  • Mineral penyusun adalah mineral feldspar plagioklas (50%), kuarsa (25%), aegerine-augite (5%), garnet (10%) dan terdapat vein kuarsa (Gambar 4f)

  • Komposisi mineral plagioklas (20%), ortoklas (10%), anortoklas (5%), quartz (35%), dan hornblende (5%)

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Summary

Pendahuluan

Indonesia merupakan wilayah geologi kompleks yang terletak di tepi tenggara benua Eurasia. Satuan Lava Basal Dimito dapat disebandingkan dengan Formasi Tinombo (Teot) pada fasies gunungapi (Bachri, 2006) dengan dasar kesebandingan pada kesamaan ciri fisik litologi yang khas berupa adanya mineral zeolite, tekstur porfiro afanitik, dan ciri khas pillow lava (Gambar 4a). Ciri litologi (Gambar 5e) yang dapat diamati di lapangan pada satuan ini adalah warna abu - abu gelap hingga abu-abu kehijauan, dengan tekstur afanitik, subhedral - anhedral, intermediet vulkanik, terdapat urat kuarsa, bersifat masif dan kompak, namun pada beberapa tempat telah mengalami pelapukan, dan berstruktur kekar berlembar (sheeting joint) (Gambar 5d) sebagai salah satu penciri lava. Ciri litologi (Gambar 6e) dari satuan ini terdiri dari material lepas dan berupa endapan yang belum mengalami kompaksi dengan fragmen batuan beku berupa andesit, granodiorit, dan basal, didominasi oleh tekstur berukuran lempung dan sebagian berukuran pasir – bongkah. Material ini dominan diendapkan di daerah sungai sehingga menutupi batuan sebelumnya (Gambar 8.4)

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