Age of Kimberlite pipe

Some Siberian Kimberlite pipes have following geological peculiarity. Initial horizontal contact joints of sedimentary country rock curve to the depth of the Earth near ore body. Its sometimes curve to the surface of the Earth. Angle of curving achieves 10 degrees [1]. The following explanation is proposed. Heavy pipe moves to the depth and light pipe moves to the surface due to creep of rock.
The following formula is proposed to estimation of age of Kimberlite pipe: T=va/dgR, where T - age of the Kimberlite pipe, v - viscosity of country rock, a - an angle of curving strata near ore body, d - difference between densities of ore body and country rock, g - free fall acceleration, R - radius of pipe. References: 1. Boltenhagen I.L. Geomechanical estimation of age of Kimberlite pipe in salt rock. -Ukraine, Alushta: Scientific School of Academician S.A. Khristianovich, 2005 [in Russian] (look also at the internet-site http://www.boltengagen.narod.ru).