Mantle plume and uplift tectonic of Borneo, Southeast Asia

Author Sardjono
DOI https://ww

Country : Indonesia
Subject :

Keywords : Mantle-plume structure, rapid uplift, Borneo Island.

Abstract

The island of Borneo includes the territories of Kalimantan Indonesia, Serawak-Sabah Malaysia and Brunei Darussalam. The region is highly dynamic in terms of tectonic and delicate in terms of climate. The island is characterized by tropical rain forests, dense vegetation, high humidity and hostile terrain, indicated by high rates of denudation which resulted from rapid uplift of the crustal rocks. Mechanisms have been set forth by previous geological studies to explain the rapid uplift of the region. The present study, using topography and gravity data, attempts to elucidate that, the origin of the uplift tectonic is the upward buoyant force of the low-density mantle-plume structure situated at the lithospheric depth beneath Borneo Island.

Results of the analysis of the Bouguer gravity show the presence of the mantle-plume structure at a depth of about 160 km below sea level. The structure is about an elliptical in shape, striking SW-NE in the central northern part of the island, the Central Range Region, approximately 600 km long, 300 km wide and about 40 km thick. Results of the analysis of free-air gravity and topography with the mantle plume at depth, indicates that the Central Range Region is in the status of isostatic disequilibrium. The crustal and lithospheric column analysis indicates that the thickness of the present-day crust beneath the Central Range Region is 15.7 km. Adopting the standard thickness of granitic crust of 30 km, this implies that approximately 14.3 km granitic crust has been uplifted, exposed, eroded, emplaced at surface and subjected to further processes of erosion, weathering and transports of detrital materials. This uplift tectonic may have been continuing since about 2 Ma, suggesting the rate of uplift of about 7.15 mm.a^-1 in the Central Range Region of Borneo.

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