Abstract

In the region of Daloa, Ivory Coast, several Iroko trees ( Chlorophora excelsa , family of the Moraceae), a frequent species of the equatorial rain forest known for its calcareous excretions always related to wounds kept unhealed by insect activity, show an unusual lithogenetic aspect of this process. Between severely damaged roots, large-scale bleeding of the sap, after unsuccessful attempts to build crusts of fibrous carbonate over the wounds, has penetrated into the interstitial spaces of the adjacent granitic residual sand and cemented it by precipitation of calcium carbonate into large blocks of hard and massive calcite-cemented pure-quartz sandstone. The quartz and rare feldspar grains displayed a high amount of marginal corrosion by the cryptocrystalline calcite cement. The agents responsible for the severe damage to the trees cannot be determined with certainty but are assumed to be elephants, wild boars or jungle buffaloes. This recent sandstone demonstrates processes of intense corrosion of detrital quartz and feldspar grains and of general cementation both by calcite which have taken place at or near the surface before any decay, burial, overburden or compaction could occur and which, therefore, should be considered as geologically instantaneous.

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