Mineralogical changes with depth in a layered Andosol near Bandung, Java (Indonesia)

Authors:
  • HRH. VAN Reuler
    H. VAN Reuler
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Abstract
SUMMARY: The mineralogy and some physical and chemical properties of an Andosol developed in four distinct layers of volcanic ash have been investigated. Analytical methods used include X‐ray diffraction, transmission electron microscopy, particle‐size analyses, infrared spectroscopy, pyrophosphate extracts of C, Al and Fe, and acid‐oxalate extracts of Al, Fe and Si. Three buried A horizons in the ash were also dated by the 14 C method. The dates obtained indicate burial of A horizons c . 17700, 14500 and 8600 years B.P., respectively. Halloysite dominates the weathered fraction in the ash older than 17700 B.P., whereas allophane and imogolite with molar A1/Si ratios of 1.7–2.0 are predominant in the younger ash layers. Some kaolinite also occurs in the upper two layers of ash. It is considered possible that the halloysite in the deepest ash layer formed under different climatic conditions from those prevailing at present, rather than due to resilication of allophane under the overburden of ash. The results also demonstrate the mineralogical complexity of soil developed in more than one layer of volcanic ash.

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