Karst Landforms in the Saraburi Group Limestones, Thailand
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KARST LANDFORMS IN THE SARABURI GROUP LIMESTONES, THAILAND Gheorghe Ponta, Bashir Memon, James LaMoreaux PELA GeoEnvironmental, 1009 23rd Avenue, Tuscaloosa, Alabama, 35401, USA, [email protected], [email protected], [email protected] Jade Julawong, Somchai Wongsawat Water Resource Engineering Co., Ltd., 52 Soi Ladphrao-wanghin 26, Ladphrao-wanghin Road, Ladphrao, Bangkok 10230, Thailand, [email protected], [email protected] Abstract The area is underlain by the limestone of the Saraburi Agricultural development in the Saraburi Province Group of Permian age. The limestone is exposed as a of Central Thailand has increased the demand chain of hills, ridges, and occasionally as mounds which for groundwater resources. Hydrogeological create classic 'tower karst' scenery. investigations have been undertaken by Department of Groundwater Resources (DGR) to identify potential The rainforests, excessive rainfall and widely variable zones of groundwater in the karstified limestone of the climatic conditions caused a karst landscape and cave- Saraburi group. forming environment to develop, with streams draining into the limestones from mountain catchments. In this The area is located 120 km north of Bangkok between the area, the mature karst is locally fringed by tall cliffs cities of Saraburi and Pak Chong in the south, Lopburi that overlook valleys and closed basins. The area to the west, Chai Badan and Nong Pong to the north, and underlain by limestone is extensive and rainfall is Nakhon Ratchasima to the east. It covers the following abundant. Therefore karstification potential exceeds 200 districts: Amphoe Pack Chong, Nakhon Ratchasima Province; Amphoe Muang Muak Lek, Khangnoi, Phaputabat, Wong Muang and Chalormphrakiat in Saraburi Province; and Amphoe Moung, Lamsonthi, Phatananikom, Thaluang and Chaibadan in Lopburi Province (Figure 1). The topography is characterized by mountain ranges, karstic plateaus, and rolling hills of low to medium relief, with low lands in between. The mountainous ridge elevation reaches over 800 m above sea level (ASL), karstic plateaus are developed between 300 and 500 m ASL, and the low lands are at about 100 m ASL. In the karstic plateaus and mountains areas, springs, caves, and dry stream beds exist. In dry periods, some streams in low land areas are dry, but the large rivers continue flowing. Tropical climate (Monsoon type) with two distinct seasons is characteristic of this area. The dry season begins in October and ends in May, followed by a monsoon season between June and September. Annual rainfall ranges between 1,500 and 2,000 mm and temperature ranges between 20.00C and 40.70C. Figure 1. Saraburi Province of Thailand (shown in red). 13TH SINKHOLE CONFERENCE NCKRI SYMPOSIUM 2 299 m vertically. Exokarst landforms are well represented. Geology Various types of karrens, tsingi, small- to medium- sized The project area is underlain by the limestone of the sinkholes, sinking streams, and closed depressions were Saraburi Group of Permian age. (Ridd et al., 2011) identified during site investigation. (Figure 2). The carbonate rocks are exposed as a chain of hills, ridges and occasionally as mounds which create A dye study performed in October 2012 indicated the classic 'tower karst' scenery. hydraulic connection between a sinking stream and Tham Lumphini Suan Hin Spring, and a water supply well (Well In stratigraphic order from oldest to youngest, the rock 114) located 300 meters southwest of the spring. Based on units are the: Phu Phe, Khao Khwang, Nong Pong, Pang the dye study, the protection area for the Well 114 and the Asok, Khao Khad and Sap Bon formations. spring also includes the closed depressions. Phu Phe Formation (Lower Permian). The carbonate Introduction formation consists of pinkish-gray to very dark gray Development of land in the Saraburi Province of Central limestone, nodular and tabular chert bands, partly Thailand has increased the demand for groundwater intercalated with slaty shale. Fusulinids and crinoids resources. Hydrogeological investigations have been are present. undertaken to determine potential zones of significant accumulation of groundwater in karstified limestone The Phu Phe formation is located in the central aquifer of Saraburi Group for exploitation. south part of the project area, and its outcrop covers approximately 68 km2 as a ridge with vertical cliffs. The area is located 120 km North of Bangkok between The Phu Phe formation is thrusted over Sap Bon and the cities of Saraburi and Pat Chong in the south, Khao Khad formations of Lower- Middle and Middle- Lopburi to the west, Chai Badan and Nong Pong Upper Permian Age. The Phu Phe formation outcrops to the north, and Nakhon Ratchasima to the east. It 25 km East of Saraburi. It is divided in two sections covers the following districts: Amphoe Pack Chong, along the Highway No.2 (Mittraphat Road) between Nakhon Ratchasima Province; Amphoe Muang the cities of Sap Bon and Khao Phu Phe. The Siam Muak Lek, Khangnoi, Phaputabat, Wong Muang and Cement Plant quarry is located in this formation Chalormphrakiat in Saraburi Province; and Amphoe (Figure 3), north of Highway 2. Moung, Lamsonthi, Phatananikom, Thaluang and Chaibadan in Lopburi Province. Khao Khwang/Tak Fa Formation (Lower Permian). The formation is widely distributed in the northern The topography is characterized by mountain ranges, part of the Saraburi area. The formation was deposited karstic plateaus, and rolling hills of low to medium in a shallow-marine platform environment (Ridd et al., relief, with low lands in between. The mountainous 2011). From the border between Nakhon Sawan and Lop ridge elevation can reach over 800 m above sea level Buri provinces (the Tak Fa—Ban Mi area) to southern (ASL), karstic plateaus are developed between 300 and Phetchabun Province (the Nong Phai area), Nakornsri 500 m ASL, and the low lands are at about 100 m ASL. (1976, 1981) established the Tak Fa Formation which is In the karstic plateaus and mountains areas, springs, mainly carbonates in the Saraburi Group. caves, and dry streams exists. In dry periods, some streams in low land areas are dry, but the large rivers The Khao Khwang/Tak Fa formation of Lower Permian continue flowing. Age is located in the northern part of the project area. The outcrop area is approximately 650 km2. It is a karstic Tropical climate (monsoon type) with two distinct plateau with rolling hills of low to medium relief, which seasons is characteristic of the project area. The continue north with a narrow strip about 25 km long and dry season begins in October and ends in May, 4 to 1 km wide (~100 km2 – Tak Fa Formation) ridge followed by a rainy season between June and with vertical cliff and 23 dry-hillside caves. In the latest September. Annual rainfall ranges between 1,500 geological publications/maps the narrow limestone and 2,000 mm and temperature ranges between strip belongs to the Tak Fa Formation (Amphoe Ban Mi 20.00C and 40.70C. geological map 1:250,000). 300 NCKRI SYMPOSIUM 2 13TH SINKHOLE CONFERENCE Figure 2. Geological Map of the Project Area (from Ridd et al., 2011). Figure 3. Geological map with location of karst features. 13TH SINKHOLE CONFERENCE NCKRI SYMPOSIUM 2 301 Nong Pong Formation (Lower—Middle Permian). The Hydrogeology Nong Pong Formation is dominated by intercalations of The availability of ground water in karst aquifer system laminated thin-to-thick-bedded shale and thin-bedded of the Saraburi Group of Permian age varies widely limestone with locally developed chert. It occurs due to complex geology. This aquifer system has an widely in the central part of the Saraburi area and it is extensive subsurface network of interconnected joints, approximately 670 m thick (Ridd et al., 2011). fractures, and dissolution/solution cavities as observed in the field during the investigation. These interconnected The Nong Pong formation is located in the central part of fractures serve as conduits, leading water from the top of the project area. The area of this outcrop is approximately the mountains/karstic plateau to springs. The limestone 700 km2. It is a karstic plateau with rolling hills of low aquifer system of the Saraburi to medium relief. Group serve as a major source of groundwater for Pang Asok Formation (Lower—Middle Permian). domestic, industrial, and agriculture uses. At the This siliciclastic dominated unit in the Saraburi Group interface of noncalcareous formations with karstic crops out south of the Nong Pong Formation. It is formations, streams are sinking underground to approximately 360 m thick, and consists of interbedded discharge to spring(s) and cave(s). The availability brownish-grey to greenish-grey shale to slaty shale with of water varies during two distinct seasons. During local sandstone lenses (Ridd et al., 2011). the dry season (October to May) the flow of the springs and rivers/streams diminishes substantially. Khao Khad Formation (Lower—Middle Permian). This In the mountains area all the sinking streams were unit is up to 1800 m thick and consists of mainly thin- dry. During our field visits in December 2011, 11 to very thick-bedded limestone with chert nodules and springs, one perennial sinking stream, and one locally interbedded argillite, dolomitic shale, siltstone, perennial cave stream were identified. A network sandstone and conglomerate. It is distributed extensively of manmade ponds and lakes has been developed to in an almost WNW—ESE direction in the Saraburi area. collect and store surface runoff and the rain water (Ridd et al., 2011). during the wet season. A major portion of the water from the open ponds and lakes is lost due to the The Khao Khad formation of Lower-Middle Permian age high rate of evaporation. Air temperatures are above is located in the south part of the project area. It outcrops +300C for most of the time. as a limestone strip/band oriented NW- SE, 125 km long and 15 km wide.