. [Reports vol. I-XIII]. oal Measure ageand which are filled with a material, once sand but now consoli-dated to a more or less coherent sandstone. These channels arereferred to on p. 25. They were probably formed during sometemporary elevation of the Coal Measure strata above the levelof the water in which the latter were previously laid down. Theuppermost strata must then have been in,a barely coherentcondition such that they were quickly corraded by water flowingupon their surfaces; thus ravines and broad valleys could havebeen formed during short periods. A sinking of the stratawould cause
. [Reports vol. I-XIII]. oal Measure ageand which are filled with a material, once sand but now consoli-dated to a more or less coherent sandstone. These channels arereferred to on p. 25. They were probably formed during sometemporary elevation of the Coal Measure strata above the levelof the water in which the latter were previously laid down. Theuppermost strata must then have been in,a barely coherentcondition such that they were quickly corraded by water flowingupon their surfaces; thus ravines and broad valleys could havebeen formed during short periods. A sinking of the stratawould cause a renewed submergence and all loose and abraidedmaterial would become suspended in the waters; of these thesand, as the heavier portion, would naturally settle into the erodedchannels and other depressions, even at the beginning when thewaters were more or less in a condition of commotion. In Fig. 9,an attempt is made to represent a section through such a buriedchannel, now filled with sandstone. Its independence of the. Fig. 9. Diagram illustrating buried channels of Coal Measure age, Distribution ofsuch. present topogrnphy is there indicated. On the right hand sideof the sketch the sandstone is shown to be directly the extensionof a layer of sandstone interbedded with the other Coal Measurerocks; while, on the left, it is made to appear as an independentand superior layer to any other. Either condition may exLst innature. Buried channels of this chiiracter have been recognizedin Johnson, Lafayette, Randolph and Monroe counties; theyhave an important bearing}upon this distribution of the coal,inasmuch as they are in places over a mile wide and extendlengthwise entirely across the counties. They doubtless occurin other counties and their distribution will be defined as thedetailed mapping of the Survey is extended. THE COAL BEDS. 37 The second class of buried channels are of much later agegeologically and belong to what is known as the Quaternary orPleistocene period; at least
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