Struktur Geologi Daerah Dulamayo Selatan dan sekitarnya, Kabupaten Gorontalo, Provinsi Gorontalo

Abstract

This study aims to map surface geological conditions, analyze the geometry and kinematics of joint structures, and reconstruct the orientation of principal stresses (σ1, σ2, σ3) to identify local tectonic control mechanisms in the Dulamayo area and its surroundings, Gorontalo Province. Data collection was conducted through field geological mapping, joint orientation measurements, and lineament extraction from DEMNAS satellite imagery. The data analysis technique integrates rose diagrams for morphotectonic lineament orientation and lower-hemisphere equal-area stereographic projections (Schmidt net) for stress kinematic analysis on conjugate shear joints. Results indicate a landform dominated by Structural Hills composed of the Volcanic Andesite Unit and the Granodiorite Unit. Dominant macro-structural lineaments are oriented Northwest–Southeast (NW–SE, 311°) and North Northwest–South Southeast (NNW–SSE, 348°). Stereographic analysis of shear joints reconstructs a vertical to sub-vertical maximum principal compressive stress (σ1 = 85° - 87°), sub-horizontal intermediate stress (σ2 = 3° - 5°, NW–SE), and purely horizontal minimum tensile stress (σ3 = 0°, NE–SW). The vertical σ1 orientation indicates that the study area underwent deformation controlled by a Local Extensional Stress Regime (normal faulting environment) with horizontal extension oriented NE–SW (N 36° E - N 71° E). This local deformation character demonstrates compatibility with the regional tectonic framework of North Sulawesi during the Neogene to Pleistocene epochs associated with crustal extension dynamics.