Abstract

Energy-dispersive analysis and X-ray mapping has shown that carbonate occurs primarily as detrital calcite and dolomite grains and not, as some earlier workers have suggested, as surface encrustations or "gnarls" on quartz and feldspar grains. This provides strong evidence against a process of "loessification" and indicates that the loess has experienced only slight postdepositional weathering and diagenesis. Secondary carbonate encrustations are sometimes found on grains in the B horizons of soils present within the loess, but such layers form only a relatively small proportion of the total loess thickness. All of the larger loess grains examined exhibit "rough" surface textures because of adhering fine silt- and clay-size particles. No differences were observed between the surface textures of grains from fresh carbonate-bearing loess and those from decalcified samples treated with 50 percent HCl. Much of the fine debris can be removed from the grain surfaces by sonic vibration or, in more resistant cases, by HF treatment. The surface textures of quartz grains treated in this way typically show fresh, angular breakage features which are consistent with a glacio-fluvio-eolian origin.--Modified journal abstract.

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