G22 



SCIENCE. 



[N. S. Vol. III. No. 69. 



represented by phenomena occurring in the 

 Ozark Plateau region, the particular portion 

 of it included in this epoch is no better de- 

 marked than in the coastal plain. But the 

 Ozark region immediately adjoins a drift- 

 covered region on which the Kansan drift 

 sheet is widely exposed, and when the two 

 regions have been exhaustively studied the 

 relation of the drift to the valleys along the 

 border will furnish data for discriminating 

 the proposed Ozarkian epoch from that 

 which followed. The geographical element 

 of the term has been already used in geo- 

 logical nomenclature, as, for example, the 

 Ozark Series, the Ozark Upliftand the Ozark 

 Plateau, but the term as suggested dififers so 

 widely from those in use that it can never 

 be confounded with them. Furthermore, 

 the term is euphonious and in harmony 

 with the nomenclature already adopted for 

 the other epochs of the Pleistocene period. 



The Ozarkian epoch as here proposed 

 may be defined as a marked period of ele- 

 vation and sub-aiirial erosion instituted by 

 the great post- Tertiary epeirogenic uplift 

 of North America, and terminated by the 

 Kansan epoch of widely extended glacia- 

 tion. The following general table of the 

 sub-divisions of the Quaternary Era graph- 

 ically exemplifies its relative position : 



PBESENT EPOCH DEPOSITION. 



TEEEACE EPOCH EROSION. 



Wisconsin Epoch. ..3d Glacial Drift. 



Toronto? Epocli 2d inter-Glacial.. Erosion. 



lowan Epoch 2d Glacial Drift. 



Aftonian Epoch 1st inter-Glacial. .Erosion. 



Kansan Epoch 1st Glacial Drift. 



Ozarkian Epoch. ...pre-Glaoial Erosion. 



Lafayette Period Deposition. 



[Note. Tlie subdivisions of the Pleistocene period 

 in the above table, except the last, are from Chamber- 

 lin's classification of the drift. The inter-glacial 

 epoch between the lowan and Wisconsin stages of 

 glaoiation has been provisionally named from the fos- 

 siliferons beds at Toronto, Canada, although it is con- 

 sidered far from certain that these strata belong to 

 this epoch. 



It is not customary to affix names to periods of ero- 

 sion, although these are generally the longest and of- 

 ten the best marked divisions of geologic time. It 

 has been suggested that it vs'ould be well to simply 

 recognize the intervals of erosion, when encountered 

 in any region, and wait until deposits occupying them 

 have been discovered, before naming them. But in 

 the case of the particular one under discussion, the 

 conditions were such that no deposits contemporane- 

 ous with it are likely to be discovered. During the 

 period of elevation which immediately succeeded on 

 the Lafayette submergence the shore line was far be- 

 yond its present position, and the river alluvium 

 and marine deposits of that epoch are buried under 

 later formations and covered by the sea, wliere they 

 can never be examined. Nor are there any correlative 

 glacial deposits which could furnish a name to the 

 epoch. The Ozarkian epoch as proposed is to termin- 

 ate previous to the earliest Pleistocene glaciation of 

 any portion of North America, except, perhaps, the far 

 North. At present the Kansan epoch, which is to in- 

 clude the advance and retreat of the ice sheet which 

 formed the so-called Kansan drift, is considered the 

 first of the great glaciations. But if any decisive evi- 

 dence of any previous distinct glaciation should be 

 discovered it would constitute a new epoch and simply 

 detract from the length of the Ozarkian epoch. The 

 writer is of the opinion that the portion of the Qua- 

 ternary era characterized by glacial conditions began 

 at some time subsequent to the opening of the era, 

 and it is to this distinctively pre-glacial portion that I 

 wish to attach the name, Ozarkian epoch O. H. H.]. 



Oscar H. Heeshey. 



Fkeepoet, III. 



ORGANIC MARKINGS IN LAKE SUPERIOR 

 IRON ORES. 



At the instance of Dr. Charles D. Wal- 

 cott. Director U. S. Geological Survey, and 

 with the kind permission of the editor of 

 this paper, I beg to submit the following 

 note, hoping that the subject may be brought 

 to the notice of the oflicers of the U. S. Ge- 

 ological Survey, the Geological Surveys of 

 Michigan and Wisconsin, etc., as well as 

 that of all field workers among the rocks of 



