ANALISIS FASIES PADA FORMASI MENANGA, PEKON GUNUNGKASIH, TANGGAMUS DAN SUNGAI WAY SABU, PESAWARAN, LAMPUNG

Abstract

The Menanga Formation is part of the Woyla terrane, the last large terrane amalgamated formed island of Sumatra. Woyla terrane consist of Cretaceous arc assemblage and relatively lack of research has been done on this formation in Lampung and surrounding areas. This study aims to identify the facies of the Menanga Formation. Research was carried out by making a measured stratigraphic and dividing it into facies and facies associations. The data were taken from two places, in Gunungkasih, Tanggamus and Way Sabu, Pesawaran, Lampung. The results showed that the Menanga Formation has eight facies, there are red claystone (F1), gray claystone (F2), bioturbated siltstone (F3), laminated siltstone (F4), laminated fine sandstone (F5), Parallel sandstone (F6), ripple sandstone (F7), loadcast sandstone (F8), and graded bedding sandstone (F9). The Menanga Formation facies were grouped into two facies associations, namely levee facies association (AF1) and channel facies association (AF2). AF1 consists of F1, F2, F3, F4, and F5 which shows the upper part of the turbidite sequence while AF2 consists of F5, F6, F7, F8, and F9 which shows the lower part of the turbidite sequence. The Menanga Formation shows siltstone dominance with sedimentary structure formed due to turbidit current and stacking pattern show fining upward-thinning upward indicate midfan lobe environment The Menanga Formation interpreted to be deposited in submarine fan environment whose sediment material originates from the Woyla volcanic arc.