Evaluation of Weathering Stage, Soil Development, and Soil Classification at Karangsambung Formation and Melange Lok Ulo complex in Karangsambung, Kebumen, Central Java. Supervised

Abstract

Geographically Indonesia is a country that is influenced by Hindia Australia, Eurasia, and Pacific plates interaction. One of the evidence of interaction can be seen in Karangsambung, Kebumen, Jawa Tengah. According to Sukendar Asikin (1974), stratigraphy of Karangsambung is Melange Lok Ulo complex, Totogan-Karangsambung formation, Waturondo formation, and Panosogan formation. This research was aimed to study the relation between geologic formation/soil parent material as one of land component with weathering stage, soil development and its soil classification by Soil Taxonomy System. The research was done with soil morphology description of six soil profiles that located in Karangsambung formation (P1 developed on diabas and P6 develop on Shale) and Melange Lok Ulo complex (P2 developed on phylite, P3 developed on chert, P4 developed on marble, and P5 developed on basalt). Besides that, soil sampling, laboratory analysis, evaluation of weathering stage by mineralogical, chemical, and physical methods, and soil classification by Soil Taxonomy were also conducted. Based on the evaluation of weathering stage from mineralogical, chemical, and physical methods, it was obtained that the physical and chemical estimation method is relative analogously, whereas mineralogical method is not. The order of weathering stage sequencly is P4>P1>P5>P3>P2>P6. These soil profiles are categorized as developed profiles. The order of soil development stage was determined by horizon completeness and effective depth of soil. The soil development sequence is P4>P1>P3>P2>P6>P5. Using Soil Taxonomy (USDA, 2006), the soil formed at Karangsambung formation is classified as Typic Dystrudepts, whereas the soil formed at Melange Lok Ulo Complex as Fluventic Dystrudepts and Typic Dystrudepts. Based on this soil classification system, geologic formation has indirect correlation with soil’s name family category, likewise with weathering stage and soil development.