An assessment of paleoenvironment of the Rakwana-Pannila limestone mountain of Sri Lanka

Abstract

The Rakwana mountain range, which is located in the margin of the northern side of Sinharaja, a UNESCO world heritage site, is an area having rich bio–diversity. The recent excavations of the alluvial deposits in Sabaragamuwa basin associated with northern side of Sinharaja area revealed that the existance of caves in the vicinity of Pannila mountain. The cave formation is seen within the rocks of crystalline limestons (marble),which is popularly known as ‘Pannila Hunugala’ is of 550 m in length and 350 cm height at its entrance of which 60 cm filled with water, where special cave characteristics are visible. Stalagmite and stalactites of 2.5 m height at the core of the cave was believed to be formed after re-crystallization of pre-existing crystalline limestones- the basement rock - in the Highland Complex of Sri Lanka belongs to the Precambrian age. Speleothem dimensions were used to measure the volume of stalagmite and stalagtites. The action of chemical weathering of crystalline limestone followed by limy solutions makes it secondary features like stalagmite and stalactite.It is postulated from the Geological map of Sri Lanka that the same crystalline limestones bed is extended to the Rakwana Pannila 'Hunugala’, Samanalawewa, Handagiriya caves.