Escarpment retreat in sedimentary tablelands and cuesta landscapes - Landforms, mechanisms and patterns

Although the general concept that escarpments in layered rocks retreat through time was offered more than 150 years ago, recognizing the exact mechanisms, patterns and rates of retreat remains a challenge. In this paper, we provide the state-of-the-art of the theme of escarpment retreat, reviewing both the classic contributions, often forgotten but important case studies, and the latest research. In separate parts of the paper we discuss: (1) terminology applied to the geomorphology of escarpments; (2) the main assumptions and pathways of long-term evolution of escarpments, including conceptual models presented so far; (3) processes involved in cliff retreat, mainly weathering, mass movements and erosion; (4) the role of spring erosion and fluvial processes, leading to fluvial dissection and development of canyons present in many tablelands; (5) the possible role of climate change in escarpment evolution; (6) rates of escarpment retreat. In conclusions, we summarize the major advances in our understanding of escarpment evolution of the last two-three decades such as the recognition of the key role of emerging groundwater in non-uniform escarpment retreat, of an important role of silica dissolution and underground removal of dissolved solids, increasing appreciation of rock properties in governing the patterns of escarpment retreat, the proposal that cliffs do not necessarily retreat via catastrophic rock slope failures but may disintegrate in situ, and the first attempts to date escarpment retreat using cosmogenic isotopes. Finally, the remaining gaps and possible research priorities for the future are identified.