A Silurian "pipe-rock" at Hadeland.

Working on a general petrologic survey of the Lower Llandoverian sandstone series in the northern part of the Oslo Region, I visited a section along the high-road at Klinkenberg, NE of Jevnaker railway station. The section cuts through an anticline, the axis of which dips slightly to the west. It forms a rather complete profile through the sandstone series, the total thicknes of which in this place amounts to c. 120 m. - About a hundred metres above the bottom of the sandstone series some thin beds of a greyish-green, arenaceous shale occur; they are partly laminated by fine layers of dark-coloured sandstone, and filled up with vertical cylinders consisting of a similarlooking material. Approximately four metres downwards and eight metres upwards in the series the rock consists of similar dark-coloured, arenaceous beds, more or less irregularly mingled up with the greyishgreen shale material, sometimes causing an indistinct stratification. The thickness of each bed may exceed half a metre, the bedding surfaces, howev·er, are not everywhere quite distinct. A doser examination revealed an abundance of black cylinders in these rocks as well, though they could not easily be recognized, because of the slight difiference in colour.