The rate of climatic change estimated from gradient in signal recorded in lake sediments may be erroneous if post-depositional perturbations are overlooked. A smear out of a pulse signal, over a variable thickness of core section, due to physical of biological mixing, is a well known phenomena. Much less attention is paid to a possible overestimation of the rate of change when a part of record is missing due to an erosion event. In this paper we show a few examples of recent sediment perturbations and the resulting distortions in the time scale, as documented by short-lived radionuclides.