Owing to differential erosion, the red weathering crusts of carbonate rocks usually show special profile structures that are characteristic of thick-bedded, intensely weathered profiles and strongly undulate basement rock surface (i. e. alternate distribution of solution grooves and stone teeth). In this work a typical red weathering crust of dolomite rock (i. e. Pingba profile) is selected in a karst terrace in Guizhou Province, China. Via field geology, geochemistry, mineralogy, grain size analyses, and in comparison with two neighboring limestone soils (i. e. Luoli profile and Longdongbao profile) as well, we discussed the formation process of the red weathering crusts of carbonate rocks, and demonstrated that micro-area transportation of acid-insoluble residues of carbonate rocks is a style of forming the red weathering crusts, especially the thick-bedded those of carbonate rocks. The weathering crusts at solution grooves, at the scope of the depth upwards from weathering front, are in-situ weathering residues (i. e. residual layers); over this depth upwards, are accumulated deposits of different weathering intensity (i. e. accumulation layers) from upper adjacent stone teeth situation by micro-area transportation. This process is a direct cause leading to intense undulation of weathering indices with the depth. The latter generally compose the principal part of the profiles. At solution grooves, the chronostratigraphy of the red weathering crusts of carbonate rocks shows that, at residual layers, upwards from weathering front, the weathering age is from new to old; at accumulation layers, from bottom to top, the weathering age is from old to new. The weathering front is a main place of geochemical reaction, and at this limited-thick interface, with quick dissolution of carbonates, acid-insoluble residues begin to obviously decompose. However, ensuing evolvement of weathering crusts is very slow. When they is up to gravity balance (i. e. flat surface and no micro-area transportation), under the action of weathering from exterior to interior, at the scope of the depth from the surface downwards, the weathering profiles are gradually reconstructed and take on the developing feature of normal weathering crusts.
|Number of pages||12|
|Journal||Acta Geologica Sinica|
|Publication status||Published - 15 Jan 2007|
- Carbonate rock
- Micro-area transportation
- Red weathering crust
- Weathering front