Landscapes and landforms in coarse clastic sedimentary tablelands – Is there a unifying theme?
Piotr Migoń, Filip Duszyński
Abstract
Coarse clastic sedimentary successions cover approximately-one fourth of the continental surface and give rise to distinctive landforms at a variety of scales. Rock-mass strength differences between members of layered successions account for the presence of escarpments, typically capped by thick sandstone or conglomerate beds, usually also with mid-slope cliffs and benches reflecting variable resistance of individual members of the succession. Depending on the dip of strata, two main types of regional landscapes are plateaus and plains, or homoclinal ridges (cuestas), but higher degree of deformation may occur in the vicinity of major faults, resulting in hogback morphology. Medium-scale landforms include residual hills of various types such as mesas and buttes, rock cities and assemblages of ruiniform relief, whereas canyons and slots are common valley forms. Escarpment retreat is usually considered as an overarching concept in geomorphology of layered successions, but it does not seem to be a universal pathway of landscape evolution and even retreat itself may occur in different ways. We propose that juxtaposition of strong and weak rocks in the vertical succession is the viable unifying theme, as it has profound geomorphological implications, influencing processes and patterns of evolution at a variety of spatial scales. However, depending on lithological characteristics, mechanical and hydrogeological properties, dominant processes may vary, explaining considerable landform diversity within tablelands, even though at the grand scale stepped topography becomes a repetitive theme. Synthetic graphical presentation of morphogenetic systems on coarse clastic successions is also presented.