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other parts of the world, that there were beds which would necessarily, from their stratigraphic position and fossils, have to be placed between the Carboniferous and Permian, and were in truth transition beds between the two. The idea that each system had ended in a great break, both in stratigraphy and biology, has been abandoned, and with it has gone the old rule of classification; and the more we know of the history of the globe, the more we become certain that the gaps and chasms heretofore existing in its life history will be filled up.
As long as we cling to the old names for the systems and attempt to place all these transition beds in one or the other of them, we will be led into endless disputes, with no probable termination, because there is no definite rule by which they can be positively referred. Some have attempted to evade the controversy by calling the transition beds PermoCarboniferous or Permo-Trias, with the result of multiplying the difficulties rather than avoiding them, for no definite line can be drawn between the Coal Measures and the Permo-Carboniferous or between the PermoCarboniferous and the Permian.
The definition given by Murchison of the Permian of Russia has generally been adopted in the United States; that is, to place everything in the Permian that is found to occur between the Carboniferous and the Triassic. Still the line could not be definitely settled, for as yet what constitutes the top of the Coal Measure series in this country has not been defined, even where there are no transition beds to complicate matters.
In Indiana the Merome sandstones overlie the Coal Measures. The sandstones belong to the same formation as that in Illinois which was referred by Prof. E. D. Cope provisionally to the Triassic. In a later publication he said: "The evidence now adduced is sufficient to assign the formation as represented in Illinois and Texas to the Permian." These sandstones do not constitute a bed of continuous deposition with the beds below, but are seen at a glance to have been deposited after a considerable lapse of time after the time of the deposition of the lower beds. While the beds below belong without doubt to the Upper Coal Measure series, it has not been shown that they are the very highest beds of the Coal Measures. In fact there is no place in North America where it can be said that the beds are at the very top of the Coal Measures, and everything that follows must be put in another series. In Illinois these beds are overlaid by a bed of black, gray, red, and pink shales, backed with sandstone, filling a depression denuded by forces acting at the close of the Coal Measures age which carried away the regular deposits, including probably three seams of coal. The beds furnished a lot of vertebrate fossils which were referred to Prof. E. D. Cope for identification. "
The fossils were of such a character that Prof. Cope said one of them was of a distinctive Triassic type, while the other had not been found heretofore above the Carboniferous. At a later time Prof. Cope, as has already been mentioned, referred these beds to the Permian.
And when it is said that these beds were deposited in the depression caused by erosion after the close of the Coal age. it is not intended to say that the beds which had been eroded were the very last of the Coal Measures, although they may have been; but it is intended only to say that the top of the Coal Measures as found there had been destroyed, and the beds now called Permian had been deposited subsequently.
At the meeting of the American Association for the Advancement of Science, at Baltimore, 1858, Mr. A. H. Worthem, State Geologist of Illinois, read a paper on the Permian rocks of that State, and he had a fine collection of fossils which he considered as belonging to that system.
At a later period Mr. Worthem said the fossils exhibited at Baltimore were not the Permian of Europe, but were simply of the same form as those from the Lower Permian of Kansas, as described by Prof. Swallow, and that he believed they should be referred to the Upper Coal Measures.
In Missouri the Upper Coal Measures are overlaid by the drift, and are said to be older than the Measures in Kansas.
In West Virginia the upper part of the Coal Measures has been referred to the Permian by Fontaine and White, upon the evidence of the flora found in the beds. The majority of plants described by them and referred to the Permian were from the top of the Warrensburg coal bed.
It seems that no attempt has been made in this country to definitely determine by the fossils just what shall be the top of the Coal Measures, and the only attempt to correlate the beds in different sections has been by the lithological character of the coal beds. Fossil plants have been used to distinguish the Carboniferous coal beds from the Triassic and Cretaceous, but have not been used to determine the divisions of the series.
There has not been so great a demand in the Eastern States for the correct definition of what constitutes the top of the Coal Measures, because the contacts between the different series there are distinctly and well defined except in a few places, and it is only in the West, where there is a continuous sedimentation from the well defined Coal Measures strata to that of the acknowledged Permian, that the matter has been productive of disagreement between geologists, as to the series to which certain strata ought to be referred.
In Kansas, Nebraska, and Texas there are beds that are certainly transitional between the Permian, as defined by Murchison, and the Carboniferous "
Proc. Acad. Nat. Science, Phila., Sept., 1875.
Proc. Acad. Nat. Science Phila., 1858, Vol. X, p. 144.