92 MR. W. J. CLAEKE ON THE TJNCONEORMITY Il^T THE [Peb. IQOI, 



assume, continued underground, until a similar ridge is met with at 

 Huntington Colliery. On the south-eastern side it is bounded by 

 the Trimpley anticline through Shatterford and Compton, as shown 

 by Mr. T. C. Cantrill.^ There, however, we meet with certain pheno- 

 mena not found in the Coalbrookdale field. 



Firstly, there is, as pointed out by Mr. Daniel Jones, a series of 

 unproductive measures, intermediate between the Middle productive 

 grey Measures and the Upper non-productive red Measures (whose 

 basement-beds are here represented by the rocks and marls under- 

 lying the Main Sulphur Coal). As these measures are very thick 

 in the Highley and Shatterford Pits, and on the other hand very 

 thin or non-existent in the Harcott and Billingsley pit-sections, 

 between which two groups a fault exists, it would seem as though 

 this fracture had commenced before the Upper (red) Measures 

 were deposited, whereas in the whole of the Coalbrookdale field I 

 know of no fault that has occurred before the Upper Coal-Measures 

 were first deposited, excepting of course minor slips. They all 

 seem to be post-Carboniferous in date, affecting Upper and Middle 

 Coal-Measures equally. 



Secondly, on the north-western flank of the Trimpley-Shatterford 

 anticline the Upper Coal-Measures have been tilted to a greater 

 extent than the Middle Series, owing, as I suggest, to volcanic action 

 continued in Permian or post-Permian times. 



Summarizing the foregoing observations, we find in the Middle 

 (productive) Coal-Measures of Shropshire a series of undulations 

 diminishing in amplitude and length as we proceed from the north- 

 west towards the south-east. The axes of these undulations have a 

 general east-north-easterly direction, the synclines being unsym- 

 metrical in form, having steep slopes on the north-north-west and 

 rising at a very small angle to the south-south-east, as though the 

 force of the undulatory movement originated in the north-west and 

 was directed towards the south-east, the apparently rising ground of 

 the Shatterford district forming a point of resistance. Between 

 these synclines are a series of anticlines, from the tops of which all 

 the productive Coal-Measures were removed, and the subjacent 

 formations laid bare before the Upper (red) Measures were deposited. 

 Such, I submit, is the nature of the unconformity which exists 

 between the Upper and Middle Series, and constitutes the so-called 

 Symon ' Fault.' 



But the existence of undulations of this nature in the Middle 

 Coal-Measures is not confined to Shropshire. Commencing with 

 the Pendle line of upheaval, which runs past the mouth of the Dee 

 through Ormskirk to Pendle Hill, and forms the northern boundary 

 of the Lancashire Coalfield, we pass firstly the E,ossendale anti- 

 cline ; then one in connection with the Great Bala Fault, dividing 

 the Flintshire from the Denbighshire Coalfield, and visible at the 

 surface at Caergwrle Castle and Caer Estyn, the coals on the 

 south-eastern flank of which it has been the writer's privilege to 



^ * A Contribution to the Geology of the Forest-of-Wyre Coalj5eld * 

 Kidderminster, 1895. 



