BURIAL OF PEAT DEPOSITS 515 



off sharply from the overlying clay and silt." The upper layers of 

 the peat represent transported material from farther up the stream, 

 and consist of silt with twigs and branches and trunks of trees. 

 Other examples are cited by Stevenson (46). 



Glacial till is not an infrequent cover for peat deposits. Sir 

 William Dawson (i7:dj) has described an early Quaternary 

 bog in Nova Scotia, where the peat was covered by 20 feet 

 of boulder clay and so compressed that it had almost the hardness 

 of coal. In the New England States such peat buried under gla- 

 cial drift is not uncommon, and it has been observed in widely sep- 

 arated districts in the glaciated area. In Montgomery County, 

 Ohio, a bed of peat, 15 to 20 feet thick, and with its surface formed 

 by Sphagnum grasses and sedges, underlies 90 feet of gravel and 

 sand. The peat contains coniferous wood, bones of elephant, mas- 

 todon and teeth of giant beaver. In southwestern Indiana and 

 part of Illinois an ancient soil, 2 to 20 feet thick, and containing 

 peat, muck, rooted stumps, branches and leaves, lies at a depth of 

 60 to 120 feet below the surface. 



Peat deposits on the flood plains and deltas of rivers are likely 

 to be buried under the silt and mud when the river rises, and like- 

 wise, when through a change in climate or other cause a river be- 

 gins to rapidly aggrade its flood plain. In siich cases the peat de- 

 posits will be buried under regular strata of sand and clay of con- 

 tinental origin, and it would happen that the trees still standing are 

 gradually buried in the silt and sand. "Even the slender canes of 

 the Mississippi delta, killed by salt-water invasion, remain standing 

 after they have been surrounded by several feet of silt." (Steven- 

 son-46.) The filling of the hollow bark of still erect trees, in which 

 the wood has decayed, by sand and mud and so ensuring their pres- 

 ervation in an erect form, is a familiar fact to students of the Coal 

 Measures. The well-known section at South Joggins, Nova Scotia, 

 shows erect Sigillaria and other trees in considerable number. The 

 most important part of the section containing these trees is as fol- 

 lows (Dawson-i8) : 



Sandstone with erect Calamites and Stigmaria roots 6 ft. 6 in. 



Argillaceous sandstone, Calamites, Stigmaria and Alethop- 



teris cuchitica I ft. 6 in. 



Gray shale, with numerous fossil plants, and also Naiadites, 



Carbonia and fish scales . 2 ft. 4 in. 



Black coaly shale, with similar fossils I ft. i in. 



Coal with impression of Sigillaria bark o ft. 6 in. 



"On the surface of the coal stand many erect Sigillariae, pene- 

 trating the beds above, and some of them nearly three feet in 



