1859.] HULL TIIINNIXG-OUT OF THE SECONDARY ROCKS. 73 



Northamptonshire divides itself into two well-marked zones*. The 

 Lower Zone includes the Stonesfield Slate, as well as clays, shelly 

 oolitic freestones with current-lamination; and lastly, those thick 

 beds of ferruginous sands which are so largely developed in 

 Northamptonshire. The Upper Zone, on the other hand, is ex- 

 tremely distinct, consisting of evenly bedded limestones, weathering 

 white, with bands of calcareous marl. The fossils of the Upper 

 Zone are seldom fragmentary, though generally in casts, and appear 

 to have been buried whero they lived. As might be expected, the 

 horizontal range of these two zones is very unequal, and, on the 

 whole, they probably represent, respectively, shallow- and deep-sea 

 conditions of the Great Oolite. 



These two zones range probably from Yorkshire, and certainly 

 from Lincolnshire, as may be gathered from the description of the 

 Oolites of Lincolnshire by Professor Morris t, and from thence into 

 Northamptonshire and Oxfordshire. 



The Lower Zone attains its greatest development towards the 

 w< stern escarpment of the Oolites of Wiltshire and the centre of the 

 Cotteswold Hills ; but eastward it dwindles down until it entirely 

 dies out in the Valley of the Cherwell, near Woodstock. 



The same south-easterly attenuation is also observable in the 

 case of the Forest-marble, which may be considered a subformation 

 of the Great Oolite j. Thus wo have reason for concluding that 

 under the Oxford Clay of a large portion of Northamptonshire and 

 Oxfordshire, we should pass from the Cornbrash into the Uppet 

 Zone of the Great Oolite, and from this into the Marlstone, the 

 intervening beds having disappeared. 



From internal evidence over an extensive range, afforded by the 

 evenly bedded limestones and marls of the Upper Zone of the Great 

 Oolite, and from its continuity over an area ex lending at least from 

 Somersetshire to Lincolnshire, combined with the fact that it 

 furnishes no evidence of a tendency to thin away towards the south- 

 east, I am inclined to think thai this subdivision extends as far as 

 the Palaeozoic barrier of the Thames Valley, and that it is the 

 identical pari of the formation described by M. Etozel as resting 

 upon the Carboniferous rocks of the Bas-Boulonnais. Il is the ///•>•/ 

 exception to south-easterly attenuation we meet with in ascending 

 through the Siesozoic rocks of England ; and it cannot be regarded 

 drifted Bedimentarj deposit, bu1 as one which, like the White 

 chalk, was formed on the bed of a comparative!} deep sea l>v the 

 agency of living animals, or by the precipitation of the fine cal- 

 careous mud derived from Molluscs, Corals, and Foraminifera. 



• Op. c t. p. 68. 



t Quart Journ. GeoL Boo. roL i\. p. 334. The beds which in Lincolnshire 

 succeed the ferruginous lira ndered bj Professor Morris as \< 



<>olit<\ an- "stratified sands and days, local in their occurrence, bearing plant- 

 remains." These beds represent the "Lower Zone" of the Great Oolite, and 



are Buooeeded bj marl] whiU litea, "indicating deeper-sea conditions," 



which represent the " Upper Z ." 



I his formation <li.-.- out i" the VeJlej of the Oherwi II. east of Woodstock 

 -. Slap of GeoL Survey, Sheet l>. s W. . and •• Heel.. \ ■■!" W'oodstot-k." |>. •_' I. 



