Reply to the comment on “Diatomaceous sediments and environmental change in the Pleistocene Olorgesailie Formation, southern Kenya Rift Valley” by R.B. Owen, R. Potts, A.K. Behrensmeyer and P. Ditchfield [Palaeogeography, Palaeoclimatology, Palaeoecology 269 (2008) 17–37]