An unconfornity between the clayey and the sandy facies of the Septaria Caly in a clay pit near Winterswijk (The Hetherlands, province of Gelderland) is described. The lowermost part of the sandy facies contains many broken and splintered fragments of septaria, phosphorites and sharkteeth, that do not show a sign of transportation. This basal conglonerate is thought to be due to a short but heavy period of erosion of the uppermost part of the clayey facies of the Septaria Clay.