EFFECTS OF BIOKARSTIC PROCESSES ON THE DEVELOPMENT OF SOLUTIONAL RILLENKARREN IN LIMESTONE ROCKS

Karren landforms developing on limestone rocks are understood to be pr oduced primarily by chemical dissolutional processes. Available data s uggest that rainfall intensity, drop size, water temperature and visco sity play significant roles in the growth of the most simple of these features, which are termed rillenkarren. Nevertheless, chemical data a nd scanning electron microscopy provided by our study have shown that mechanical removal of small limestone particles is one of the principa l processes involved in the growth of rillenkarren. This mode of detac hment is caused by the impact of raindrops but their effect seems grea tly increased when algal cells of Chroococcus minutus (Kutz.) Nag. hav e previously corroded the surface of the limestone, weakening its crys talline structure. These fragile micromorphologies of biokarstic origi n are fundamental in the development of rillenkarren, complementing th e wellknown physico-chemical controls that are involved.