Page:The South Staffordshire Coalfield - Joseph Beete Jukes - 1859.djvu/216

198 beds sink down again and are endeavouring to adjust themselves to their altered condition, consequent on the intrusion of the wedge A.

As all these actions may take place in nature simultaneously and very irregularly, according to a multitude of varying conditions, we may have a great number of modifications of the simple action here described. Among other things we may easily imagine the apex of the wedge to suffer considerably in some places, and to be ground off till it may have a blunt base, not only of 8 feet, but of many yards in width.

I have spoken before of the benefit Practical Mining might receive from the study of the science of Geology. This case is an instance of the great reciprocal advantage the science of Geology would receive from the observations of practical miners, if they knew what to observe, and how and where to record their observations. In the matter of faults and dislocations in the Coal-measures especially, there are many curious observations yet to be made, and many cases occur that would at first puzzle a geologist, and might be deemed by him impossibilities till he saw them before bis eyes. Some of these came partially and imperfectly under my own observation when surveying this coal-field, but they could only be properly described and recorded by a person who was-frequently engaged in measuring and drawing them during the progress of works extending, perhaps, over weeks or months.

We may, perhaps, here advantageously say a word or two as to the age of the principal faults and dislocations of the South Staffordshire district.

It is clear that, however the Silurian rocks may have been partially disturbed and denuded before the deposition of the Coal-measures, none of the prominent dislocations and disturbances which give the marked features to the structure of the district, took place till after the formation of the whole of the Coal-measure series. All the great faults, then, are of a later date than the deposition of the newest Coal-measures of the district.

How far the pre-existing rocks were fractured and disturbed at the commencement of the Permian period, or during the interval between the deposition of any Coal-measures and that of any Permians, is very difficult to be determined.

From considerations partly derived from this district, partly from other portions of the Midland Counties, it would appear probable that great disturbances, producing both large dislocations and an immense amount of denudation, took place some time during the Permian period, or some time between the period of the Coal-measures and that of the true New red sandstone. I should incline to look on it as possible that the disturbances along the line of the Lickey, and the Dudley and Sedgley anticlinals are of this date, and possibly also some of the principal faults of the coal-field. It is, however, plain, from the description given in the last Chapter, that the great boundary faults of the coal-field were, if not produced, at least largely acted on, subsequently to the deposition of the whole of the New red sandstone, and even to that of the Lias.