Microfacies and Depositional Environment of Tertiary Limestone, Gorontalo Province, Indonesia

Abstract

The research area is located in northern Limboto Lake in Gorontalo Province, which has complex geological characteristics. The geological complexities include stratigraphy and tectonics which influence the formation of the Limboto Basin. Limestone research in the Late Tertiary Limboto Basin is very intriguing to be done because of the lack of research in limestone. Gorontalo limestone outcrops, which become the focus of the research, have a total thickness of 30 meters. The research objective is to analyze facies, microfacies, and depositional environment of tertiary limestone. These two research objectives are attained by using two research methods, namely measurd section and petrography analysis. The research result exhibits that there are four Gorontalo limestones facies, including coralline rudstone intercalated with thin mudstone facies, sandy micrite intercession facies, coralline rudstone intercession facies and sandy allochem limestone intercession facies. According to the limestone micro- facies standard, the depositional environment of Gorontalo limestone is platform interior restricted (facies zone 8).

Analisis Lingkungan Purba Batugamping Daerah Limboto Barat Kabupaten Gorontalo

“…Berdasarkan penelitian terakhir yang dilakukan terdapat beberapa jenis dan fasies pengendapan batugamping. Beberapa fasies batugamping yakni fasies coralline rudstone, perulangan mudstone-packstone, fasies, sandy micrite dan sandy allochem limestone [4,5,6,7].…”

“…Hasil analisis biostratigrafi di laboratorium Paleontologi dan Mikropaleontologi menunjukkan bahwa jenis spesies foraminifera bentonik setiap sampel yang teramati bervariasi. Totalnya ada tujuh (7)…”

“…Bukti pengaruh tektonik pengangkatan di utara Cekungan Limboto yang saat ini tersingkap di permukaan dengan kecepatan pengangkatan 0,0699-0,0724 mm/tahun [3].Berdasarkan penelitian terakhir yang dilakukan terdapat beberapa jenis dan fasies pengendapan batugamping. Beberapa fasies batugamping yakni fasies coralline rudstone, perulangan mudstone-packstone, fasies, sandy micrite dan sandy allochem limestone [4,5,6,7].Penelitian ini sangat menarik untuk melengkapi penelitian sebelumnya mengenai batugamping dari segi komposisi fosil foraminifera. Penelitian mengenai paleobatimetri batugamping di selatan Danau Limboto pada zona neritik tengah-neritik luar [8,9].Umur batugamping di sekitar Danau Limboto berdasarkan penelitian terakhir yakni Miosen Akhir-Pliosen Awal [10] sedangkan penelitian sebelumnya berumur Pliosen-Pleistosen [11].…”

“…Tongkat Jacob sepanjang 1,5 meter tersebut memiliki interval 10 cm dengan ditandai perbedaan warna mencolok hitam dan putih. Tujuan metode MS ini dilakukan untuk mendapatkan stratigrafi daerah penelitian berdasarkan karakteristik yang berbeda dari masing-masing fasies [3,6,7,10,14].…”

The Analysis of Sliding Surface in Alo Watershed, Gorontalo District, Indonesia

“…Referring to the latest research, the name of new limestone formation is Limboto Limestone Formation. This formation consists of two to three microfacies with shallow marine paleobathymetry that have undergone tectonic uplift [5,6]. The slope on Alo watershed is dominated by gentle slopes with slopes ranging from 8 -15% with a percentage area of 3.14%, and slopes of 15 -25% are 25.74%.…”