Doloinitization in tlie Carhoniferous Liviesione. 55 



the dolomitic beds are abruptly replaced by normal limestones, but 

 the actual lateral transitions of dolomite into limestone are obscured. 

 On the maps the symbol L.T. represents such transitions obscured 

 by vegetation or by cultivated land. Actual visible passages from 

 dolomite into limestone are represented by L.P., and where the 

 material which must have contained the transition has been denuded 

 the symbol L.T.D. has been employed. At various positions near 

 Winster masses and stacks of dolomitic limestone form prominent 

 land-marks known locally as tors. Westwards beyond the Grey Tor 

 the width of the outcrop of material affected by dolomitization 

 becomes less, though the dip of the beds remains about the same. 

 The beds on the horizon of the Winster escarpment have westwards 

 passed into normal limestones within a distance of 1|- miles. 

 Similarly some of the higher strata not far below the Pendleside 

 Shales are dolomitic towards Wensley, but have become normal 

 limestones a little west of Winster, a distance of about 1 mile. 

 Further towards Gratton Dale the area of metasomatism becomes 

 greatly attenuated and finally dies out near Dale End Farm. 

 Concerning the dolomitic area from Bonsall Moor Farm to Gratton 

 Dale as a whole, several important facts should be summarized ; 

 nowhere is the vertical ^ passage of limestone into dolomite 

 or dolomite into limestone actually seen. The lateral passages are 

 also generally obscured, but exceptions to this occur at Gratton, 

 Westhill Farm, and Winster. 



At Winster, opposite the inn called the " Miners' Standard ", 

 are small disused quarries containing cherty beds, showing rapid 

 transitions of dolomite and limestone, the patches of -the latter 

 being usually a yard or two in length. A striking tectonic feature 

 is the absence of faulting in all of the beds north of the lower lava. 

 The Bonsall fault south of the lava throws some light on the probable 

 southward extension of some of the dolomitic limestones of Winster. 

 Between the lower lava in the Via Gellia and this fault considerably 

 more than 100 feet of D^ strata, all non-dolomitic, have 

 been brought down and the upper beds must be the southern 

 extension of the lower dolomitic limestones to the north. The 

 material containing the southern transition from dolomite into 

 limestone must have existed above the lower sequence in the inter- 

 vening space, but has since been removed by denudation. 



Eastwards all of the dolomitic beds appear to pass into limestone 

 within a short distance. Westwards all of the dolomitic material 

 has become limestone at Gratton Dale, 2^ miles from the Winster 

 escarpment. The more rapid lateral transitions occur on the lower 

 and higher horizons, while in the middle of the D^ sequence the 

 metasomatism has been more persistent. 



From these considerations of field evidences it is obvious that the 

 Winster area of dolomitization is a true outcrop in the petrological 



^ i.e. up or down the sequence. 



