Palaeoenvironmental Evidence in Northwest Sri Lanka Evidence from Mundal Lake and Its Environs

Abstract

During the Last Glacial Maximum (LGM), between 30,000 and 19,000 years ago, about 50 million cubic kilometres of ice that melted from land-based ice sheets, have raised global sea level by 130-180 metres. During the LGM Sri Lanka’s landmass was larger than the present time, as it extended to100 fathom line (180m) below the present coastline identified as the “submerged peneplain”. The name “Flandrian Transgression (FTG)” has been applied to the current sea level rise affecting the coastal regions around the globe, which began approximately 19,000-18,000 years ago. This rise in sea level was directly related to the melting of the continental polar and mountain piedmont glaciers forming present 99 continental shelves in tropical and subtropical regions. However, the rate of melting and proportional sea level rise was not constant through time, and sea level rose quickly during warm periods, but stopped or even temporarily fell during cold periods. The few sea-level curves available indicate that slight emergence predominated during the late Holocene along the coasts of Mozambique, on the southern shores of the Persian Gulf, west India and west and south Sri Lanka, whereas evidence of emergence is missing in oceanic islands. The FTG submerged the lithogenic quartz and biogenic carbonate sediments, former river courses, erosional remnants, scrublands, forests, wetlands etc. of the lowest peneplain, of Sri Lanka. Accordingly, the present configuration of Sri Lanka and micro landforms on the present coastal plain evolved. An approximate landforms configuration that existed in Sri Lanka prior to the FTG is now identifiable in a west-east profile across Mundal Lake.