no SILURIAN. 



CONISTON GRITS AND FLAGS. 



The Coniston Grits and Flags were so named by Sedgwick, 

 from Coniston, in Lancasiiire. They consist of hard siliceous 

 sandstone or grit, flags and conglomerate, with thin bands of slate, 

 which are placed on the horizon of the Denbighshire Grits and 

 Flags. The upper part, especially, contains beds of grit or tough 

 sandstone, interstratified with shivery mudstone ; the lower com- 

 prises flaggy beds and finely-striped dark blue mudstones, which 

 are more fossiliferous. 



The thickness of this group is estimated at between 6000 and 

 7000 feet in the Sedbergh and Howgill districts ; but it may be 

 more in the Lake District proper, for there is no continuous section, 

 and the beds are much disturbed and faulted. The strata rest 

 conformably upon the Pale Shales and Graptolitic Mudstones, and 

 are divided as follows : — 



2. Coniston Grits, about 4200 feet. 

 I. Coniston Flags, about 2000 feet. 



Among the fossils of the Coniston Flags are many species of 

 Graptolites, Monogmptus priodon, M. colonus, AI. Sedgrvickii, and 

 Rttiolites Geinitzianus. Other fossils are Favosites fibrosus, Cardiola 

 intcrritpia, Orthoceras primcevum, O. subundulatum, Lituites giganteus, 

 and Fhacops ohtusicaudatus. The Coniston Grits contain fewer 

 fossils, including Graptolites, Monogmptus Roemeri, etc. ; also 

 Cardiola intcmipta, Pterinea tcnuisfriata, Orthoceras Ludense, O. 

 primavum, Rhynchonella navicula, Acidaspis, Phacops Doimiingice., 

 Ceratiocan's Muirhisoni, Spirorbis LtnvisiV, and Encrinites. 



In the Windermere district the beds have been divided as follows 

 by Mr. J. E. Marr:— 



IViiideniiere District. Sedbergh District. 



Coniston Grits. Upper Coniston Grits. 



fUppe 



(Beds S.W. of Helm Knot, 

 ( beds of High Hollins, etc. 



^ ., f Co dwell Middle „ . t^x f tt^i„, t„„. 



Comston j,^^,^_ (Lower J Beds N. of Helm Knot. 



i^ lags. ^ Brathay Flags. Flags of Frostrow Fell, etc. 



An excellent section of these beds in seen in the neighbourhood 

 of the Coldwell and Brathay quarries, south-west of Ambleside. 



The Brathay Flags (of Sedgwick) consist of blue, well-cleaved, 

 and finely-laminated flags, of uniform lithological character 

 throughout, and of fine texture. They yield JMonograptus priodon, 

 Rctiolitcs Gcinitzianus, Favosites aspera, etc., and are regarded as the 

 zone of Cyrtograptus Murchisoni. The Lower Coldwell Beds consist 

 of coarse grey grits of no great thickness, and are apparently 

 unfossiliferous. The Middle Coldwell Beds (of Sedgwick)^ com- 

 prise calcareous, flaggy grits, with Phacops ohtusicaudatus, Stropho?nena 

 depressa, Cardiola intej-rupta, and several species of Orthoceras. The 



1 See also Aveline, Explanation of 98 N.E. (Geol. Surv.), p. 8. 



