Polygonal karst morphology of Karangbolong area, Java-Indonesia

Abstract

The Karangbolong karst is situated in the southern zone of Java where Miocene limestone has been uplifted and has experienced karstification since the late Pliocene. The research documented here aims at exploring morphological characteristic of the area. Special interest is attributed to differentiation of valley or depression morphology, conical karst morphology, and the roles of jointing system and uplift history in their development. The morphology investigation was mostly undertaken using aerial photograph visual interpretation of panchromatic aerial photograph and analytically shaded DEM, as well as field observations. The results show that the general morphological features of Karangbolong karst are characterized by aligned valleys and aligned enclosed depression with three different patterns. The orientation of the valleys and enclosed depressions coincide with the structural pattern of the area, indicating that the formation of aligned valleys and aligned enclosed depressions is preferential dissolution through jointing. The residual hills are typified by conical karst morphology with sharp peaks. It is found that tight joint spacing appears to be the main reason for the sharp peak of the conical hills. Asides from jointing system, morphology of the area is likely governed also by topographical position and gravity sliding of the limestone bed during the uplift. Uplift history has important control on the differentiation of morphology between plateau part and sloping part. Limitation of this research is that the aerial photograph was not rectified well, because the analyses in this research were more on pattern identification. More accurate rectification is needed for better morphometric analyses.