LOESS AND THE PROBLEM OF LOESSITE IDENTIFICATION.

Abstract

This paper attempts to discuss the concepts about loess, its main features and origin, as well the possibilities of preQuaternary loess formation and identification. Loess has been defined in different ways. There are two main approaches concerning the meaning of the term: loess = fine grained (silt-size) c1astic rock, and loess = c1astic eolian sedimentary deposit. The second conceptincludes the depositional features ofthe loess, e. g. massive and homogeneous sedimentary bodies of large surficial extent and discrete thickness, with paleosol levels. Loess is a typicál deposit of quite distal sectors of the continental basins;. so its preservation potential is relatively high. Therefore, the controversial point of the geological identification of the loess in pre-Quaternary successions líes in the concept of this term (rock or deposit). If it is considered a sedimentary deposit, the possibilities of identification in the stratigraphic record become greater. As loess formation is conditioned by silt supply, the persistence of surficial winds, and a firm-Iand environment in the periphery of both glacial and desert regions, the term loessite should be used in both genetic and environmental sense, as an equivalent of eolianite, turbidite, tidalite, debrite, etc. Several diagnostic features for the identification of loessites are listed and discussed.