The Karai Badlands national geological monument is located in the Karai area along the Karai-Kulakkalnattam road of Perambalur District, Tamil Nadu. A four km. the stretch of badlands with natural conical mounds and typical fossils of Cretaceous age is exposed as badlands with a series of conical mounds separated by gulleys.
Badland topography, on either side of Alattur-Ariyalur road, spread within 40-70 km. radius marks the lower part of marine Cretaceous rocks that mainly consists of clay & sandstone of Karai Formation. Like the Grand Canyon in Colorado, US, Ariyalur is considered as a Cretaceous Park of South India by the Geo-scientist.
Geological Survey of India (GSI), has declared Karai Badland as a National Geological monument for its maintenance, protection, promotion, and enhancement of geo-tourism.
The Rock formation is here exposed of Cretaceous of Trichinopoly, Which dates back to the Late Cretaceous. The Succession in the area is broadly divided into 4 Groups -Uttathur, Trichinopoly, Ariyalur, and Ninniyur, Where the Uttathur is the oldest. After comparing the age and color of the rock formations here with those of the Himalayas, we have found that they are of the same age. The Karai Formation of Uttatur Group at Karai-Kulakkalnattam section in Perambalur district forms the lower part of the Cretaceous sedimentary succession of the Cauvery Basin.