190 



THE SECONDAKY AGES. 



stones and sandstones, the saliferous marls, the shales and 

 clays * replete with the exuviae of shell-fish, Crustacea, and 

 fishes are strictly sea-formed, some littoral or along-shore, 

 and others pelagic or in deeper waters. This marine origin 

 is pre-eminently observable in the Trias and Chalk, and it is 

 only in these oolitic districts where coal and ironstone are 

 found that we have evidence of estuarine and terrestrial 

 conditions of formation. Of course we are here alluding 

 more especially to the secondary systems as displayed in 



* A better idea of the composition of these systems may be obtained, 

 perhaps, by a perusal of the annexed tabulation : 



J Chalky marls and thin-bedded limestones. 

 Chalk rock, with and without imbedded flints. 

 Greensands and cherty limestones. 

 Blue tenacious clays, locally known as " gault " 

 or "golt." 

 Green and ferruginous sands, sandstones, and 



cherty limestones. 



Wealden clays, sands, and flaggy sandstones. 

 Upper Oolite consisting of fine-grained oolitic 

 limestone with interbedded clays and bitumin- 

 ous shales (coals). 



Middle Oolite consisting of coarse-grained shelly 

 and coralline limestone, with blue clays and 

 shelly calcareous grits. 



Lower Oolite consisting of coarse shelly lime- 

 stone and grits ; thick-bedded blue clays (coals) ; 

 thick-bedded sandy oolitic limestone; flaggy 

 grits and marls ; and calcareous freestone. 

 Upper Lias consisting of dark bituminous shales 



and indurated marls or marlstone. 

 Lower Lias dark laminated limestones and clays, 

 bands of ironstone, layers of jet and coal, cal- 

 careous sandstones. 



Keuper consisting of variegated marls, sandy 

 layers, limestone layers, gypsum, and rock- 

 TRIASSIC salt. 



or / Muschelkalk grey shelly limestone, with marl 



UPPER NEW RED. \ partings and beds of magnesian limestone. 



Bunter soft variegated sandstones ; coarse-grained 

 grits and conglomerates. 



OOLITIC 



or 

 JURASSIC. 



