Morphometric and geological features of karstic depressions in gypsum (Sivas, Turkey)

Abstract

Gypsum covers an area of approximately 5 % in Turkey and is mainly found in Sivas basin. Gypsum in the Sivas basin includes many karst structures with various sizes and has a variety of forms that present different conditions offering different morphometric features. Two basic shapes of karstic terrain are reflected in this area offering a wide variety of gypsum karst. The first of these are dissolution dolines which constitute the polygonal karst areas, and the second one is collapse dolines which is deeper karst depressions formed by roof collapse and the accompanying of solutions. The aim of this study was to determine and identify general characteristics of doline in the study area using morphometric measurements and calculations. Density of dolin is very high in study area. The source of the dolines data included 1/25,000 scale digital maps containing elevation and several cartographic attribute interpretations, a very demanding field work and satellite images. The parameters calculated for the study area include depression length, width, orientation, area, perimeter, depth, circularity index, depression density, circularity index, length/width ratio and major axis orientation. This study describes an application of geographic information systems to examine the morphometric and geological features of gypsum karst in Sivas basin. The effect of geologic, structural, and hydrogeologic variables on the morphometry and spatial distribution of depressions are discussed in the study.