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Indices based on soil macroelements, such as the chemical index of alteration (CIA), the chemical index of weathering (CIW), the silicon–aluminum ratio (Sa), and the Silicon–aluminum–iron ratio (Saf) could not adequately express the sequential weathering degree of the chronosequence. The study found that Fe and Al were relatively enriched, while Ca, Mg, K and Na as well as Si were strongly lost during rock weathering and soil formation. Relative depletion/enrichment ratios of macroelements and microelements, as well as of rare earth elements (REE), were calculated and several indices were proposed to illustrate the development of the soil chronosequence.

A few indicative soil features, especially typical geochemical features, were studied and related to the stages of soil development. The absolute ages of basalt from which soils have developed varied from 1.0×10 4 a to 1.81 Ma. Basalts of different geological ages are widely distributed in the north of the island, and soils developed from them form a well dated soil chronosequence.

Hainan Island is located in the South China Sea. * College of Construction and Environmental Engineering, Sichuan University, Chengdu 610065, China.Ĭorrected manuscript received: October 9, 2006

Gan–Lin Zhang 1,*, Ji–Hua Pan 1, Cheng–Min Huang 1,2, and Zi–Tong Gong 1ġ State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China. Geochemical features of a soil chronosequence developed on basalt in Hainan Island, ChinaĬaracterísticas geoquímicas de una cronosecuencia de suelos desarrollados a partir de basaltos en la Isla Hainan, China