The erratic pebble material in fluvial sands of Leningrad interstadial (Upper Pleistocene) was examined in the Kelkolovo quarry (the Leningrad region, south of the Neva river, the right bank of the Mga). Paleozoic of the locality is no younger than Cambrian. In spite of Lower Carboniferous modem outcrops being only 150 kin to SO (down iceflow), substantive part of pebbles are Carboniferous (limestones, cherts) and Devonian (red sandstones, limestones). The source of the erratic material is discussed. The conclusion about the presence of Devonian - Carboniferous up to the modern Baltic shield before Quaternary and substantive scale of glacial denudation, especially in Early to Middle Pleistocene is preferable.