300 Geological Society. 



GEOLOGICAL SOCIETY. 



Dec. 19, 1832. — A paper was read, entitled " Report of a Survey 

 of the Oolitic Formations of Gloucestershire." By William Lons- 

 dale, F.G.S. 



This survey was made in consequence of a resolution of the Coun- 

 cil, confirmed by the Annual General Meeting of 1832, that one 

 year's dividends of the Wollaston Fund should be applied to the 

 continuing, northwards from Bath, the survey of the oolitic formations 

 commenced by the author of the Report in the year 1827. 



The district examined is bounded on the west by the escarpment 

 of the oolitic hills from Toghill, A\ miles N.W. of Bath, to Meon 

 Hill, near Chipping Campden j and on the east by the foot of the 

 coral-rag-hills, from the neighbourhood of Chippenham to Farring- 

 don, and thence by a straight line passing from Burford to Stow-on- 

 the-Wold and Shipston-on-Stour. The formations examined are the 

 marlstone, inferior oolite, Fuller's earth, great oolite, forest marble, 

 and cornbrash. 



The geologists to whose labours the author acknowledges himself 

 much indebted, are, Mr. Smith, Mr. Cumberland, Mr. Weaver, the 

 Rev. William Conybeare, Mr. De la Beche, Mr. Murchison, and 

 Mr. Greenough : he also notices the great advantage which he pos- 

 sessed in having the Ordnance Maps for the base of his survey. 



Marlstone. — This formation was originally established by Mr. Smith, 

 and its geological position, as a member of the lias formation, has 

 been subsequently proved by Mr. Phillips, in his valuable work on 

 Yorkshire. In Gloucestershire, the formation consists of about 150 

 feet of marl and sand, containing, towards the lower part, a bed of 

 calcareous or ferruginous sandstone, abounding with organic remains j 

 and its superior stratum consists of blue micaceous marl, the repre- 

 sentative of the alum shale of Yorkshire. The most characteristic 

 fossils are Gryphcea gigantea and Pecten cpquivalvis. The marlstone 

 is co-extensive with the escarpment, and may be traced within it 

 wherever the beds subjacent to the inferior oolite have been denu- 

 dated. 



Inferior oolite. — In the South of Gloucestershire this formation con- 

 sists of nearly equal divisions of soft oolite and slightly calcareous 

 sand ; but in the northern portion of the county, the latter, for the 

 greater part, is replaced by a yellow sandy limestone. The freestone 

 beds, which are not to be lithologically distinguished from those of the 

 great oolite, gradually increase in number and thickness, from the 

 neighbourhood of Bath to the Cotteswolds, east of Cheltenham, where 

 they constitute the whole of the escarpment. This vertical importance 

 is retained through the north of the country examined ; but to the 

 eastward of the valley ranging from Stow-on-the-Wold to Barrington, 

 near Burford, a change takes place, both in the structure and thick- 

 ness of the formation. The freestone beds are there replaced by 

 strata of nodular coarse oolite, containing numerous specimens of 

 Chjpeus sinuatus : the sandy portion consists of only a thin bed, and 

 the thickness of the whole formation is diminished from 150 feet to 

 about 50. The most characteristic fossils which were noticed by the 



