GEOLOGY 



core of the hills consists of the lower shales ; the flanks of the two beds 

 of limestone with their intervening shales and overlying Ludlow Shales. 

 Owing to their purity and excellence as a flux, their proximity to the 

 blast furnaces, and to the high inclination rendering the extraction of 

 the stone a cheap and simple process, the limestones have been quarried 

 for many centuries. This industry was sufficiently striking to attract 

 the attention of Dr. Plot in 1686, who also unmistakably figures some 

 of the common fossils. At the present day the underground excavations 

 extend for great distances and to considerable depths into the heart of 

 the hills, beneath which they form vast gloomy caverns, through which 

 there wanders a long canal used in the transportation of the quarried 

 stone. 



Fossils abound, some thin layers of the limestone being crowded 

 with organic remains corals, brachiopods, bryozoa. The district has 

 become especially famous for the extremely beautiful and extensive 

 series of crinoids (stone-lilies) and for the excellent preservation and 

 large number of trilobites which have not only enriched several local 

 collections, but have found their way into many cabinets abroad. 



Ludlow Shales and Aymestry Limestone. At Walsall the Wenlock 

 limestones are succeeded immediately by the unconformable Coal-measures, 

 but around Dudley Castle they pass up into bluish grey shales belonging 

 to the Ludlow sub-division, which in turn become covered up by Coal- 

 measure strata. In the Sedgley inlier the upward sequence is further 

 continued. Here, at Hurst Hill, a sharp anticline brings up the Wen- 

 lock limestones with some overlying calcareous shales 1,000 feet thick 

 and the fossil contents indicate an horizon equivalent to the Lower 

 Ludlow Shales. To these succeeds a bed of limestone 25 feet thick, 

 locally known as the Sedgley Limestone. It is not so pure as the Wen- 

 lock Limestone, and burns into a greyish variety of lime locally dis- 

 tinguished as ' black lime,' that made from the Wenlock Limestone 

 being termed ' white lime.' The commonest fossil is Pentamerus knightii, 

 which stamps it at once as the equivalent of the Aymestry Limestone of 

 Shropshire. 



Upper Ludlow Shales. Whenever present in full sequence the 

 Silurian deposits indicate a piling up of sediments on an oscillating sea 

 floor until, towards the summit, the accumulations, assisted by gentle 

 uprisings, gradually approached the surface of the sea. The commence- 

 ment only of these conditions is met with in Staffordshire, and this 

 in the Sedgley area alone, where a mere fragment of the lower portion 

 of the Upper Ludlow Shales has been preserved in the centre of a syncline 

 under a capping of Coal-measure sandstone, which has prevented its 

 destruction by denudation. In sinking the Manor Pits near Hales- 

 owen, it is stated that somewhat higher beds containing fossils of the 

 Passage beds into the Old Red Sandstone were entered beneath the Coal- 

 measures, but nowhere has any undoubted Old Red Sandstone been met 

 with, and the formation next succeeding is separated by a great interval 

 of time from the highest Silurian strata exposed on Sedgley Beacon. 



