Fig. 24.
Dudley Port Trough Faults.
Scale 6 in, to 1 mile vertical and horizontal.
1. Upper Sulphur coal.
2. Two-foot coal.
3. Brooch coal.„
4. Thick coal.„
5. Heathen coal.„
6. New mine coal.
7. Fire-clay coal.„
8. Bottom coal.„
9. Silurian shale, with Dudley limestones.
From the maximum of 130 yards, however, the throw of these faults diminishes in each direction to one of much less amount. It has been proved by the workings that each of these faults hades, or slopes downwards, towards the other at an angle of about 70°, they must, therefore, meet at no great distance below the included piece of coal, and as their throw is equal and opposite, they must, where they meet, exactly counterbalance and neutralize each other, and if continued at all, must descend as a mere fissure or crack, without producing any dislocation. It so happens that the included piece of coal is, at Dudley Port, exactly on a level with the Dudley limestone outside the faults, and the workings have been continued from the coal into the limestone. This likewise shows that as regards the mass of the country on each side, these Dudley Port Trough faults (or fault) are no dislocation at all, but only so as regards the piece of ground between them. Nevertheless, it is probable that they mark the line of most intense strain at the period when the clevatory forces were acting on the district. This is a point which for convenience sake we will discuss more fully farther on.
That they had the effect of materially modifying the action of the disturbing force is shown by the fact that to the southward of the Dudley Port Trough all the faults are downthrows to the north, while to the northward of it all the faults are downthrows to the south; in other words, all the faults of the central district form no succession of steps down to the Dudley Port Trough faults.
Faults between Dudley Port Trough and Rounds Green.—Starting from Round's Green, between Timmin's Hill and Oldbury, we have 4 faults, with some branches, running about north-east and south-west, and throwing down to the north-west from 90 to nearly 180 feet. The course of these faults is concealed towards the south-west by the trap of the Rowley Hills, while towards the north-east they appear to die out, or at all events have not been traced. The southern fault of the Dudley Port Trough itself dies out towards the north-east, its throw diminishing to 210 feet near Horsley, where it has a small branch throwing down to the south 90 feet. Two small faults, with a southern downthrow, likewise start out of it near Roseland farm.
The northern fault of the Dudley Port Trough runs into and coalesces with the Tipton fault near Horsley.
