Page:The Journal of geology (IA journalofgeology21894univers).pdf/258
- base of the series consisting of coarse red sandstones, shales and marls resting on the Old Red Sandstone.
The oil shales of Scotland are confined almost exclusively to the "Calciferous sandstone" strata in the Edinburgh district, and the principal seams occur in West Lothian, where the most important oil works are situated, about twelve miles west of the Scottish metropolis.
Broadly speaking, Edinburgh is situated on a great anticline, in the center of which there rises a ridge of Silurian and Old Red Sandstone rocks, partly igneous and partly sedimentary, whose general strike is northeast and southwest. The hard volcanic strata and igneous intrusions in these older rocks have produced most of the pictureque ranges of hills in the vicinity of Edinburgh, and the softer beds in the higher parts of the series dip away, with many complications, from either side of the central axis. To the east of the Pentland ridge the inclination of the beds is very high, and comparatively regular, and consequently the whole thickness of the calciferous sandstone series can be traversed in a short time. There is also here a large fault running along the base of the hills which conceals the lowest of the calciferous series of rocks and brings up the old volcanic beds against the upper parts of the oil-bearing strata, and indeed at one place the dislocation has been so great that the calciferous rocks with their oil shales are almost entirely hidden, and the upper beds of the Old Red Sandstone abut almost directly on the base of the marine limestone series.
The Carboniferous limestones along this line, with their interbedded coal seams, are inclined for long distances at the same high angle and plunge at places almost vertically downwards beneath the long and regular trough of Dalkeith Coal Measures, from which they emerge five or six miles farther east at a much lower inclination.
To the west of the Edinburgh anticlinal the structure of the district is much more complicated. The Calciferous rocks spread out for fifteen or sixteen miles in a tumultuous sea of undulations, basins and folds cut up by multitudes of faults, and