Karst topography and hydro-geochemical characteristics in western Thailand and their correlation to that in southwestern China

Thailand is situated in the central Indo-China Peninsula. The karst of Thailand is in the same global karst environmental zone as southwest China. Karst study in Thailand is mainly focused on the southern Shan states plateau in the north and Phang Nga bay of Karbi Province in the south. Published work on karst in Thailand has mainly been descriptive in nature, addressing topics such as the relationship between karst landscape development and regional geological structure in Mae Hong Song karst region, and the impact of climate, lithology and structure on coastline tower karst in southern Thailand. As yet, Earth System Science and Karst Dynamics have not been introduced into karst research in Thailand, thus research has not been carried out focusing on karst development mechanisms, influence factors. In this paper,the discussion of karst distribution and development,hydrogeological features of typical landscapes and their controlling factors in Thailand could help to promote study of correlations in karst geology between China and Indo-China Peninsula,providing fundamental support for the global karst carbon cycle monitoring network. Thailand has about 50,000 km2, of karst, i.e., one fourth of the Indo-China Peninsula. Typical karst landscapes are well developed, including plateau polje, peak cluster, peak valley and offshore peak forest. All those landscapes are important in the research field of global karst correlation. Since 2012, an international project in cooperation with the Department of Groundwater Resources of Thailand has been carried out by the Institute of Karst Geology. It is titled "Correlation study of karst geology between China and Indo-China Peninsula" and supported by China Geological Survey. Survey data indicates that karst in Thailand is mainly located in the west part in north-south direction, crossing 11 degrees (N19.3°to N8.5°) of latitude. Various karst landscapes with different hydro-geochemistry are found in the different latitude zone. At present, the first karst hydrogeological and carbon cycle monitoring station was established at Phu Toej spring, Kanchanaburi, Thailand, and high-resolution data was collected at 15-minute intervals for one year, including water temperature, pH, specific conductivity and dissolved oxygen. Compare to typical underground streams or springs in the karst of southwest China, Phu Toej spring has higher Ca2+(100-120 mg/L), HCO3- (8.6-9.3 mmol/L) and specific conductivity(700-777 μs/cm). This indicates that the intensity of karst processes in this catchment is much greater than that in the karst of southwest China, and there is potentially higher karst carbon sink intensity in such a tropical monsoon climate zone.