The research area located in the lowland zone and the corrugated hilly zone which is dominated by sedimentary rocks. Therefore, this study aims to determine the geological features of the research area and the study of depositional environmental facies of the Lake Deposits Formation as an analysis of the depositional environment of Limboto Lake. The research method used is the surface geological mapping, measuring section of stratigraphic and laboratory analysis. Field data consists stratigraphycal features of research area. Laboratory analysis consists of petrography and stratigraphy-sedimentology analysis. It can be concluded facies and stratigraphy of research from older to youngest, consists of clastic limestones unit formed in Late Miocene-late Early Pliocene age, reef limestones formed in Late Miocene-early Late Pliocene age, sandstones unit formed in Late Pliocene-Pleistocene age, clay unit and sandy clay unit are deposited in Holocene. Overall the study site consisted of marine, transitional and terrestrial deposition environment with Lake Deposits Formation facies is lake margin clastic deposits and meandering-stream environment deposits.

This study explores the mechanisms behind the rapid shrinkage of Limboto Lake, Gorontalo, Indonesia, using remotely sensed imagery and river outcrop investigation data. The results show that more than 70% of the sedimentation resulting in shrinkage is contributed by riverbank erosion causing rivers to drain into the lake during the period 2003–2017. From geological investigation, it is found that the lowland area to the west of Limboto Lake comprises 1 m of flood sediments, followed by at least 5 m of fine-grained inner bay sediments. Severe riverbank erosion is also observed at many points. Hence, it is concluded that the shrinkage of Limboto Lake resulted from rapid-induced rapid erosion of inner bay sediments formed during plate collision which readily flowed into and were deposited in Limboto Lake; this created a delta, especially on the west side of the lake. Accelerated sedimentation caused by river erosion has led to rapid lake shrinkage. This phenomenon could be typical of the transformation of enclosed seas into lakes by the rapid uplifting movement of land in collision zones.

Limboto Lake located in the Gorontalo Province is a part of the places where the disclosure of various types of rocks as well as various tectonic deformations, the genesis of this lake is a low basin included in shallow lake type or type of flood plain. Development of Limboto Lake starts from the existence of the Neogene extension exactly on slab-rollback extension of the Banda embayment in Early Miocene, rapid uplift and subsidence near Gorontalo Basin in Late Miocene. Various problems that occur in the Limboto Lake both silting and susceptibility to lake water flows allegedly related to the tectonic activity that ever happened even today. This study reports new determination about the ancient environment of Limboto Lake. The purpose of the study is the facies study of the Lake Deposits Formation (Qpl) to determine the depositional environment of ancient Limboto Lake in Gorontalo Basin against its influence on the current Limboto Lake. The environment facies identified in the Gorontalo Basin are marine deltaic facies and shallow marine carbonate facies (carbonate rimmed shelf). The evidence found by stratigraphically features is: (a) Marine Deltaic Environment: (1) Lithologies: mainly sandstones (compositionally dominate immaturely) through muddy sandstones, sandy mudstone to mudstone; also the presence of lignite; compressed weakly and in the form unconsolidated, (2) Texture: not diagnostic, average sorting and rounding sand grains, (3) Structure: cross-lamination and wave-lamination of various types in the sandstones, flat-bedding, and channel common. Finer sediment show flasher, wavy bedding and are heterolithic. Some sediment containing rootlets; (b) Shallow-Marine Carbonate Facies: (1) Lithologies: Skeletal packstone-wackestone, and mudstone, (2) Texture: diverse, (3) Structure: cross-lamination, parallel-lamination, wave-lamination, desiccation crack; in the reef limestone is massive and unbedded, with intense bioturbation. Based on the ancient environment determine to encourage the high activity of silting Limboto Lake because the material around the lake easily detached.