504 PRINCIPLES OF STRATIGRAPHY 



Marshes ("flows") seldom occur, since lakes and pools were rare 

 in the original surface. The peat rests either directly on the rock 

 surfaces or on the surface of glacial deposits, the contact being a 

 sharp one. In the Pennines the peats cover elevations like the 

 Cross Fell, which rises to 879 meters. It here sometimes has a 

 thickness of 4.5 meters. The peat is largely formed from the com- 

 mon reed, Phraguiitcs communis. Sphagnum is scarce in this peat, 

 as already noted for the whole of Great Britain. In places the peat 

 contains an old forest bed, sharply marked off from the other de- 

 posits and at an altitude not exceeding 780 m. A section of a peat 

 bog in this district gave ( Samuelson-40 : 200) : 



c. Scirpiis ccEspitosiis peat, yellow brown in color, very rich in 

 humus, not moldered, containing remains of dwarf shrubs. 

 Washing gave only numerous small specimens of Cenococcum 

 geophilum 125 cm. 



b. Phragmiles-Carex peat, containing numerous large stools, 

 stems, twigs, and roots of birch. The finer material con- 

 sists to a great extent of wood detritus. No coal found. 

 Nutlets of Ajuga reptans and seeds of Viola sp. were 

 washed out from a peat sample. Pollen grains of elm, 

 hazel and pine, spores of ferns and leaves of Sphagnum 

 were also found 75 cm. 



a. Boulder clay. 



This peat, as that of other regions of northern Europe, espe- 

 cially Fennoscandia, shows the occurrence of an Alpine vegetation 

 during the period of formation of the early peat. In the Cross Fell 

 the remains of these are not found in situ, however. Then followed 

 a period when the region was an extensive reed swamp, and this 

 was succeeded by wet birch forests, which in turn were replaced by 

 the wet moorland. 



A section of a peat moor in the southern Uplands of Scotland 

 gave the following succession in descending order, the altitude being 

 about 300 meters above sea-level (Samuelson-40 li'o/) : 



6. Scirpus ccespitosiis peat, mixed with Eriophorum vaginatum, 

 and also containing solitary Calluna stems. Pollen grains 

 of alder, birch, grasses, hazel, pine, Typha latifolia, etc. 

 and spores of Poly podium vulgar e and vSphagnum occur. . . 100 cm. 



5. A sharply marked layer of pine '"stools" with individuals 

 sometimes exceeding 50 cm. in diameter; rarely burnt — • 

 surrounding peat highly moldered and contains numerous 

 stems of Calluna and birch twigs ; a hazelnut also found . . 30 cm. 



4. Eriophorum vaginatum peat, rich in humus, containing some 

 birch fragments — very likely the roots penetrating from 

 above — washing gave Cenococcum geophilum, some Calluna 

 shoots, stones of Empetrum nigrum^— -goWen grains of birch, 

 hazel, pine, etc., also found 45 cm. 



