OOLITE OF THE C0TTE8W0LD HILLS. OOO 



wore collected from Horns Valley Quarry. The following is a 

 vertical section : — 



Section of the Pea -Grit Series exposed in Horns Valley Quarry^ 



near Stroud. 



ft. in. 



(). Coarse Oolito 12 



f). Variable Argillaceous lied 1 



4. Hard Creain-eoloured Bed 10 



3. Coarse White Oolite 5 



2. Typical Pea Grit 3 



1. White Oolite 10 



31 10 



lleferring to the beds below the typical Pea Grit in the neighbour- 

 hood of Stroud, the late Mr. Witchell observed that* "one of the 

 beds .... is remarkable for its great thickness ; in several quarries it 

 varies from 10 to 15 feet, a feature quite unusual in the lower 

 Oolites and is altogether different from the pisolitic character, which 

 is that of a rubbly rock," My examination of that bed quite confirms 

 Mr. Witchell's description. Thin sections show it to be a regular 

 freestone and somewhat crystalline. 



Bed J^o. 2 is what may be called the t3'pical Pea Grit. The bed 

 is about 3 feet thick, and is made up of pisolitic granules, which 

 vary from 3 to 7 mm. in diameter. The feature which distinguishes 

 this bed is the weathering out of the pisolitic spherules or granules. 

 These resist the weathering better than the matrix in which the}- 

 occur, and hence stand out in relief after exposure to the atmosj^here 

 for a time. 



Bed No. 3 is a coarse white oolite, and thin sections show that 

 the coarseness is really due to granules which may almost be called 

 pisolites. In some of these the tubules of Girvanella pisolitica are 

 seen, but in others a very much swollen tubular structure (which 

 corresponds with that in the Coralline Oolite at Weymouth) is 

 noticed. 



Bed Xo. 4 is a hard cream-coloured limestone which contains 

 pisolites; the latter vary in diameter from 3 to 4 mm., and are 

 therefore smaller than those in the typical Pea Grit. Most of these 

 pisolites appear to be formed by the minute tubules to which 

 reference has been made. 



Bed No. 5 is an argillaceous bed, and will be referred to in Part II. 

 of this paper. 



Bed No. G consists of about 12 feet of coarse oolite in bands of 

 from 2 to 3 feet thick. Thin sections show the limestone to be 

 chiefly made up of small oolitic granules of the ordinary type and 

 also a few pisoHtes in which the tubules of Girvanella are noticed. 

 These latter beds are near the' base of the Lower-Freestone Series, 

 but the Coral Bed, to which I shall presently refer as the base of 

 the Lower Preestones, is not exposed. 



* Quart. Journ. Geol. Soc. vol. xlii. (1886) p. 2G7. 



