Geomorphological and structural patterns of the scarp‑related steep dry valleys in limestone ridges: A case study from South Carpathians, Romania

Abstract

Scarp retreat is a common natural process which drives the evolution of landscape in monoclinal or horizontally bedded structures. The NW‑facing, retreating limestone slope of the Vânturarița‑Buila Massif, a mountain ridge in the South Carpathians, is incised by steep dry valleys (SDVs), parallel to each other and perpendicular to the ridge crest. We performed morphometric and structural analyses on these features in order to estimate the geomorphic control on the scarp retrogressive evolution and their relations to tectonics. Longitudinal profiles display most of their relevant morphometry. Average slope commonly ranges between 35° and 50°, often exceeding 60° on certain segments. Lengths reflect the variability of exposed caprock thickness, and changes in slope show the structural control of bedding on scarp morphology. Spatial distribution and development of the steep dry valleys, as well as the scarp retreat process, is controlled by tectonic lineaments. We performed a comparative orientation analysis on fractures of extensional origin, dextral strike‑slip faults, major faults, and steep dry valleys. Results show preferred orientations on the NW‑SE and NE‑SW. Variability in size and morphology of the amphitheater‑shaped scarp sectors depends on the exposed caprock thickness. Speleothems formed in crevice‑type caves and unearthed by scarp retreat were found along some of the steep dry valleys. This study shows that combined geomorphological and structural analysis of steep dry valleys from alpine limestone ridges can provide valuable information on the evolution and morphology of the retreating scarp they develop on.