Most regrettably there is much misuse of terminology in connection with the concept of loess and the interpretation of its origin.People often speak and write incorrectly about loess accumulation — even loess specialists who are aware of the fact that loess as a concept has to satisfy at least 10 criteria.Loess is not simply dust carried and deposited by wind. Dust only becomes loess after the passage of a certain amount of time in a given geographical zone. i.e. only through diagenesis in certain ecological environments. To state that loess is of aeolian origin is an oversimplification and an incorrect definition because an aeolian origin applies only to the dust from which the loess has been formed.We are aware of the fact that airborne dust cannot be transformed into loess in every geographical environment, but only under those conditions typical of semi-arid grassland or steppe or forested steppe. The process primarily occurs where the rate of dust accumulation exceeds sheet wash or weathering (soil formation) rates. If the rate of dust accumulation is less than that of surface erosion or of soil (biogenetic) processes, the dust then develops into soil or, through intensive weathering and increased precipitation, into loam or clay.Only part of the aeolian dust transported and deposited in a zone suitable for loess formation remains there permanently and is transformed in situ into loess. Dust not affected by diagenesis is usually further transported by snowmelt or rainwash and is only transformed into loess after it has been redeposited. The loess itself, however, is easily erodible and its minerals are readily reworked and reaccumulated and, given the appropriate conditions, it readily undergoes diagenesis again.We do not always have sufficient evidence to determine whether a given loess body is of primary or secondary origin. Traditionally, the minerals making up ‘primary loess’ have been regarded as originating in dust accumulated by aeolian processes. ‘Secondary loess’ by contrast is different from typical loess in many ways and it is not unusual to find various loess series in which superimposed dust fractions have been transformed into loess by different processes.Recently we have observed that the origin of various types of loess is governed by differences in (litho) ecological conditions rather than by the way in which the mineral material from which the loess is derived (dust) has been primarily accumulated. Loessification is therefore determined by environmental conditions.

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