90 MH. L. M. PARSONS 0>' THE C^BBOXIFEEOTrS [vol. IxxUl, 



The total thickness of limestone and dolomite seen at this 

 locality is about 48 feet. As Avill be seen from the section, the 

 ' Cavern ' exposures exhibit beds lower than those at the base of 

 the * Main ' exposure. 



The strata observed at Ticknall are typical of the Western Series 

 of inliers, and a few comments on the natm^e of the Ticknall beds 

 may be given here. 



The crinoidal limestones at the base of the Cavern exposure are 

 mostly thin -bedded, contain a considerable amount of argillaceous 

 matter, and are separated by thin bands of shale ; the bulk of the 

 rock consists of large unaltered crinoid-stems. Dolomite is absent, 

 the very small amount of magnesium carbonate present not suffic- 

 ing for the formation of definite rhombohedra. This point is 

 discussed in a later section of the paper. 



The tine-grained foraminiferal limestones succeeding the crinoid 

 beds contain hardly any dolomite rhombohedra in their lower part, 

 but a greater proportion in their upper. The bulk of the rock 

 consists of impure argillaceous limestone, containing about 8 per 

 cent, of impurities insoluble in acids. A certain amount of re- 

 crystallized calcite occm-s in place of some original organic 

 structures. 



About 2 feet of a fine-grained sandy material containing Pro- 

 (hicftis shells and a little dolomite succeed the foraminiferal lime- 

 stone just described, indicating an unusually abrupt alteration in 

 the conditions of sedimentation. 



Above the sandy stratum come several feet of thinly-bedded 

 * Productus ' limestones with thin shal}' partings. The proportion 

 of magnesium carbonate is below 12 per cent., and rhombohedra of 

 dolomite are rare. 



Grrey and yellow dolomites terminate the Carboniferous Lime- 

 stone at this locality. So far as I am aAvare^ there is in the 

 Geological Survey Memoirs no description or even mention of 

 these dolomites. The beds immediately underneath the shales of 

 ' Pendleside ' type in the Western inliers consist of about 10 feet 

 of almost pure dolomite devoid of fossils. Partings of shale are 

 not present, as in the lower beds seen here. In the lower part of 

 the dolomite the higher proportion of limonite gives the body of 

 the rock a yellow colour, but in the grey dolomite above the iron 

 compounds present appear to be in the form of carbonate, which 

 weathering to limonite on the exterior forms a brown crust, and this 

 gives to the unbroken rock the appearance of a dark grit. In other 

 respects the yellow and grey dolomites are very similar. Xo chert 

 has been found in any of the beds exposed in the Western inliers. 



"Palrtiontolouy of the Ticknall Beds. 



In compiling the faunal list my own collection has been the 

 main som'ce of information, but I have received the loan of speci- 

 mens from Mr. R. Wood, of Melbourne, Dr. Turton, of Heanor, 

 and Dr. F. L. Kitchin, of the Geological Survey. Mr. Vassall, of 



