Clay-rich red soil profiles developed in different lithologies in Indonesia were assessed using geochemical evidence, the migration coefficient and elemental ratios. Our study aimed to ascertain the source of red soil materials and to investigate the elemental behavior in tropical soils. The results indicate carbonate profiles were derived from in situ weathering, while basalt profiles, even though having close affinity to their bedrock, also showed the contribution of external materials. Elemental behavior was dynamic with carbonate profiles indicating relatively constant depletion and even distribution. Basalt profiles indicated uneven distribution with enrichment and depletion. The variation in elemental behavior was linked to difference in lithologies, age and physiochemical conditions. Our findings support evidence of both residual and multiple source parent materials in red soil formation and provide insights into elemental behavior during weathering, while highlighting the influence of external materials' contribution in deeply weathered tropical soils.

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