176 J. J. STEVENSON — CAKBONIFEKOUS OF APPALACHIAN BASIN 



group of the AUegiieny in Pennsylvania.* Collections from beds above 

 the Black Flint yield floras typical of the higher Allegheny groups. 



This paper contains important generalizations respecting isostatic 

 movements in the southern Virginia region, anticipating in full much 

 that has been given on preceding pages respecting geographical changes. 

 The conclusion is reached that the Allegheny formation shows no ex- 

 traordinary expansion in the Kanawha region, and that the Conemaugh 

 retains its Pennsylvania thickness. Detailed information published after 

 the appearance of Mr White's paper shows that the Allegheny, so far 

 from thickening on the Kanawha, is thinner there than on the Allegheny 

 river of Pennsylvania. 



In the same year appeared a delayed paper by Mr White, f referring 

 to the Anthracite region. This discussion is based on a careful strati- 

 graphical study of the Pottsville in the Southern Anthracite field, 

 whereby many indefinite conceptions of the relations, especially in the 

 western part of the field, were corrected. During this study collections 

 of plants were made in many localities which were compared with each 

 other and with those obtained elsewhere within the Appalachian basin. 

 The conclusions, like those in the other papers already cited, were pre- 

 liminary and subject to revision in a monograph of the Pottsville flora 

 which has not been published. 



The type locality is at Pottsville, in the eastern part of the field, where 

 a detailed section was obtained. Plants were collected at 41 places, 

 covering the whole field, and 14 plant horizons were discovered at the 

 type locality, the highest being about 200 feet below the Buck Mountain 

 coal bed, long taken as the conventional base of the Allegheny. Another 

 plant bed is at 43 feet below the Buck Mountain, the interval being filled 

 with conglomerate and coarse sandstone, while an abundant flora is pres- 

 ent in the roof shale of that coal bed. The study of collections obtained 

 at Pottsville enabled Mr "^Vhite to divide the column at about 700 feet 

 below the Buck Mountain. The lower division contains plants charac- 

 terizing the Lower Lykens Valley coal beds, Coal 4 and lower, at the 

 westerly end of the field; a transition flora appears in three beds, 640 

 to 570 feet below the Buck Mountain, and an Upper Lykens flora, Lykens 

 coals 2 and 3, is present up to about 375 feet below the Buck Mountain, 

 the higher plant bed underlying about 100 feet of conglomerate; while 

 • in beds at 245 and 210 feet below the Buck Mountain is a higher flora, 



* Mr White in a later paper gave reasons for placing this flora at an even lower 

 horizon, possibly in the Pottsville. 



t D. White : Fossil floras of the Pottsville formation In the Southern Anthracite coal 

 field of Pennsylvania. 20th Ann. Rept. of U. S. Geol. Survey, pp. 755-930, 



