Apeil 24, 1896.] 



SCIENCE. 



621 



have studied the subject iu the coastal 

 plain or southeastern portion of the United 

 States agree in asserting that this erosion 

 period, was the longest and in every way 

 the best marked of any that have prevailed 

 over any portion of the continent since the 

 close of the Tertiary Era. In that broad 

 belt of unglaciated highland which occupies 

 the interval between the inner edge of the 

 coastal plain and the outer border of the 

 drift-covered district, this post- Lafayette 

 erosion period is as easily distinguished as 

 on the lower country near the coast. In- 

 deed, if the evidence of its length were 

 derived solely from the amount of rock ex- 

 cavation accomplished, this inner district 

 could be relied on chiefly to furnish this 

 evidence. In both districts the period of 

 erosion was begun by an elevation of the 

 continent above its normal altitude, thus 

 enabling the meteoric waters to institute a 

 vigorously erosive system of drainage. It 

 was terminated by a general subsidence of 

 the eastern portion of the United States, 

 and in consequence an extensive submer- 

 gence in the coastal plain region and the 

 Mississippi basin. 



But in the drift-covered district, where 

 evidence of this post-Lafayette elevation 

 and erosion are not wanting, but frequently 

 obscured by other phenomena, the upper 

 limit of the erosion interval was the Kan- 

 san epoch of glaciation. This epoch was 

 followed by another of erosion on the pre- 

 viously ice-covered region, which was itself 

 many times longer than any which have suc- 

 ceeded it. These two important sub-div- 

 isions of the Glacial period are the chrono- 

 logic equivalents of the latter portion of the 

 post-Lafayette period of erosion as developed 

 outside the limits of the glaciated district. 

 Severing this latter portion there still re- 

 mains a long period of sub-aerial erosion, 

 the equivalent of what in the North has 

 been denominated the pre-Glacial epoch of 

 erosion. Recent studies have indicated 



that this early pre-Kansan erosion epoch 

 constituted at least one-half of the post- 

 Lafayette period of erosion. In fact, it occu- 

 pied a very large part of the time which has 

 elapsed since the close of the Tertiary era. 



, There is, I believe, general agreement 

 among geological students that the post-La- 

 fayette period of erosion is early Quaternary 

 in age. I shall not argue this subject, but 

 assume that it has been demonstrated by 

 various writers that the period immediately 

 supervened upon the close of the Tertiary 

 era. Consequently, being Quaternary in age, 

 the portion of it which intervenes between 

 the institution of the era and the opening 

 of the Kansan epoch constitutes the first 

 and not least important epoch of the Pleisto- 

 cene period (which, as I understand the 

 consensus of opinion, is considered to date 

 from the beginning of the era). 



ISTow, up to the present time, so far as I 

 am aware, there has been no specific term 

 applied to this first epoch as here defined, 

 except the rather indefinite one, pre-Glacial. 

 As it presented features both in conditions 

 of erosion, climate and flora, somewhat 

 similar to those which characterized subse- 

 quent inter-Glacial epochs, and in marked 

 contrast to those which characterized the 

 Glacial epochs, all of which have been al- 

 ready named, it is evident that it deserves 

 some specific application which will facili- 

 tate future studies into the natural sub- 

 divisions of the era. The name wanted 

 might be secured in the coastal plain, but 

 there it is difficult, if not impossible, to 

 separate this from the subsequent epochs to 

 which, as before stated, the latter portion of 

 the pre-Columbian erosion interval belongs. 

 Instead, we may more propei-ly derive the 

 desired term from some geographical desig- 

 nation of some portion of the unglaciated 

 highland just without the glacial boundary. 

 I hereby suggest that it be hereafter known 

 as the Ozarkian epoch. True, while the 

 post-Lafayette period of erosion is as well 



