Planation (Graded) Surface

A planation surface, also called a graded surface, is a form of peneplain. When the Earth’s crust experienced prolonged stable conditions, erosion and deposition caused by various external geologic dynamics tend to create a nearly level (inclination of 1–2‰) ground surface across different drainage basins. The cause of formation and the characteristics of a planation surface are complex as they involve erosion and depositional surfaces. A comparison of planation surfaces in different regions can facilitate the determination of the planation surface’s age; hence, in the context of geomorphology, planation surfaces are significant as ‘abstract strata’. The formation of a planation surfaces can take tens of millions to dozens of millions of years. The existing planation surfaces are mainly Neogene. After a planation surface is uplifted, its remnant parts can remain on the slope or hilltop, forming an ancient planation surface. When a planation surface is buried due to subsidence, it...