. [Reports vol. I-XIII]. souri have been separated into an Upper, a Middle and aLower division, respectively 1S17, 324, and 250 feet thick,i allhaving a slight dip a little north of west. The common concep-tion regarding these divisions, as well as those of the contiguousIowa Coal Measures, is that they underlie each other successively,concerning Coal and that, should the strata of the Upper Coal Measures in thesions. northwestern part of the State be penetrated by a shaft, the members of the Middle and Lower Coal Measures would besuccessively encountered. The reservation is generally made,how
. [Reports vol. I-XIII]. souri have been separated into an Upper, a Middle and aLower division, respectively 1S17, 324, and 250 feet thick,i allhaving a slight dip a little north of west. The common concep-tion regarding these divisions, as well as those of the contiguousIowa Coal Measures, is that they underlie each other successively,concerning Coal and that, should the strata of the Upper Coal Measures in thesions. northwestern part of the State be penetrated by a shaft, the members of the Middle and Lower Coal Measures would besuccessively encountered. The reservation is generally made,however, that some of the beds will probably thin out, disappearor be replaced by others, so that exactly the same succession ofstrata cannot be expected, though, whatever may be includedunder the indefinitely applied term Formation, is consideredto be continuous. The adjoining Figure 2 represents, in ageneral way, the implied and commonly conceived idea of thepositions and relations of these divisions of the Coal Fig. 2. Diagram illnstrating tlie commonly conceived positions of tlieCoal Measure strata. The nature of some of the Coal Measure strata demandshorizontality of position at the time of deposition and as, accord-ing to the above representation, the strata are parallel with each^horizontaL Other, they must, on this interpretation, all have been depositedas horizontal layers and subsequently tilted simultaneously intothe present position. Further, the existence of coal beds nearthe base of this formation shows that even the lowermost stratawere accumulated near the surface, and, hence, to produce theconditions generally pictured, would require a regional subsi- 1 Report Mo. Geo], Survey, 1872, Parti, p. 6, THE COAL MEASURES. 27 dence of about 2,000 feet, equal in rate and amount over the whole area, with which the process of deposition kept paceSub^s^id^ence^^of equally and exactly over every portion. An ideal restoration to a horizontal position of these strata
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