Genesis and Classification of Soils over Limestone Formations in a Tropical Humid Region

Background and Objective: Soil development over limestone formations in the tropical humid region is unique and swayed by the environment.Its genesis gives an insight into the mode of origin and how the solum is formed from parent materials.Soils overlying Shale, Limestone and Sandstone (SLS) and Sandstone and Limestone (SL) geological formations in a tropical humid region were genetically investigated.Materials and methods: With the aid of google imageries, reconnaissance visits were carried out to areas underlain by SLS and SL formations.Slope maps were generated from the DEM (digital elevation model) obtained from USGS (United States Geological Survey) Explorer SRTM 1 (Shuttle Radar Topography Mission).Soil profile pits were sunk in each slope range, described and sampled.Results: The soils were characterized by Ap, transition B and Ckt horizons as well as low CCE (calcium carbonate equivalence).Ultisols, Alfisols and Inceptisols in the USDA (United States Department of Agriculture) System were correlated with Acrisols, Cambisols and Luvisols in the WRB (World Reference Base) for Soil Resources System.Iron and aluminum dominated the entire soils and were higher in SLS by ICP-OES (inductively coupled plasma optical emission spectrometry) procedure than XRF (X-ray florescence).Furthermore, Ca and K, as well as their oxides were low in the soils.Conclusion: The impact of the tropical humid climate on the soilsʼ cation reserve was obvious; particularly the dominance of lateralization and decalcification over calcification.Relative to SL, indices of weathering presented more intense weathering in SLS.