VOL. XVII. (2) INFERIOR OOLITE— CHIPPING NORTON 205 



Lithically, the Chipping-Norton Limestone varies con- 

 siderably. In the south-western half of the district it is a 

 black-speckled, although otherwise pure white, limestone, only 

 slightly arenaceous ; but eastwards it passes into much more 

 arenaceous limestones and in places into actual sand-deposits. 



About the middle of the Chipping-Norton Limestone, in 

 the south-western half of the district, is a peculiar bed best des- 

 cribed as a " Knotty-Bed.'" This Knotty-Bed becomes very 

 hard indeed and often replete with specimens of Trigonia, 

 especially of Trigonia signata, in the north-eastern portion of 

 the district, on which account Mr Walford has termed it the 

 '' Trigonia-signata-Bed."^ 



The limestone above the Trigonia-signata-Bed may pass, 

 as in the Hook-Norton Cutting, into a M'hite sand similar to 

 that of the Lower Estuarines at Stow-nine-Churches and 

 Duston, near Northampton ; while in the sandy-limestone 

 portion, larger fragments of plants occur than further west. 

 For these beds, which are equivalent to the Chipping-Norton 

 Limestone, above the Knotty Bed, the term " Swerford Beds " 

 will be useful. 



The limestones below the Knotty Bed are usually more 

 massive than those above, have often waterworn, " wavy " 

 surfaces, and when traced in an easterly direction, are found 

 to become very sandy, and, in appearance, when soft, not 

 unlike the Harford Sands on Cleeve Hill, near Cheltenham, or 

 the sands associated with the beds about the horizon of the 

 CoUyweston Slates at Collyweston, in North Northampton- 

 shire. For these beds, Mr Walford has employed the term 

 " Hook-Norton Limestones,"^ but latterly he has dropped it, 

 and has used the term " Trigonia-signata-Sa.nds and Lime- 

 stones "* for these beds, plus the overlying T.-signata-Bed. 



The Chipping-Norton Limestone, in its more sandy 

 development, gives rise to a light, very sandy soil. Percola- 

 ting, carbonated waters dissolve up the calcareous cement, 

 and in the process cause considerable settling, slipping and 

 faulting of the beds. The carbonate of lime is often deposited 



1 Called the " Old Man " by the quarrymeii at Sharp's Hill. This bed in its " knotty" develop- 

 ment is excellently seen in a quarry opposite the Merry-Mouth Inn, Fyfield, where there is the usual 

 kind of limestone above and below. 



2 Quart. Journ. Geol. Soc., vol. xxxix. (1883), p. 238. 



3 Quart. Journ. Geol. Soc., vol. xxxix. (1883), p. 238. 



4 Od Some New Oolitic Strata in North Oxfordshire" (1906), pp. 4, 5 and 27. 



