Enhancing the geological aspect of aesthetic karst and beaches landscape to promote geotourism in Nusa dua and Nusa penida South Bali

Abstract

The magnificence of Bali makes this city famous as the world paradise among travellers. Its natural beauty emerges from its landscape, condensed culture and the local community. In southern Bali, the tranquil sandy beaches and karst landscapes attract few tourists, whereas their well-preserved sites store appealing facets of geological phenomena, heritage and tourism which differ to other tourism spots in Bali. This study aims to promote geotourism of Nusa Dua and Nusa Penida in Southern Bali with regards to the geological aspect of carbonate development, bioclastic sedimentation, tidal and wave abrasion, karstification, the emergence of freshwater spring on the sandy beaches and the dissemination of vertebrate fossil in the underwater cave. Geological observation is carried out to investigate karst and beaches morphologies, the geometry of reef carbonate and its karstification proce ss as well as the constituent of abundant white-sand sediments. The collected samples of sands and rocks from 4 sampling sites were analyzed using petrography analysis to identify the rock types and sand composition, while laser diffraction particle size is used to indicate the size distribution and how intense the winnowing process occurred. As a result, the existence of carbonate outcrops in Nusa Dua and Nusa Penida beaches is caused by tectonic uplift that elevates the pre-existing coral reef from shallow marine into the surface. In the surface, the reef carbonate underwent dissolution and karstification, which generated cave or other unique geometry. The discovery of vertebrate fossils in the underwater cave of the Stiva cave, Nusa Penida, reveals that this cave became a shelter for prehistoric human before it was inundated by seawater after the last maximum glaciation. Subsequently, reef carbonate growths perpetually to compensate the sea-level rise, uplifted again to surface and karstified until the present time. Another interesting object is the presence of nearshore groundwater seepage that discharges from a porous well rounded-sandy materials. It is assumed that the unconfined groundwater less firmly compresses the seawater when passing the maximum tidal level. These fascinating geological phenomena should be introduced to the visitors to educate them about the significance of preserving the geological landscape and environment.