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NORTHUMBERLAND AND DURHAM.
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| III. | Carboniferous System, in four Formations. | |
| 1. Tuedian. | ||
| 2. Mountain Limestone in two groups. | ||
| a. Carbonaceous. | ||
| b. Calcareous. | ||
| 3. Millstone Grit. | ||
| 4. Coal Measures. | ||
| IV. | Permian System. | |
| Magnesian Limestone Formation. | ||
| MESOZOIC ERA. | ||
| V. | Triassic or New Red Sandstone. | |
| CAINOZOIC ERA. | ||
| VI. | Plistocene. | |
| Boulder Clay, Gravels, Sand. | ||
| VII. | Post plistocene. | |
| Gravels, Peat. | ||
| IGNEOUS ROCKS. | ||
| Feispathic. | ||
| Porphyry, Syenite. | ||
| Augitic. | ||
| Basalt, Greenstone. | ||
I. CAMBRO-SILURIAN.
Cambro-Silurian strata occupy but a small area in the western part of Northumberland, and do not occur in Durham. They are highly inclined against the porphyry, in the bed of the Coquet a little above Philip, and extend beyond the source of that river into Scotland. In a deep ravine, eastward of Makendon, they are well exposed ; and the Roman camp at Chew Green is formed out of them ; for some of the rampiers are natural walls of Greywacke in situ, the rock having been removed on both sides.
