. [Reports vol. I-XIII]. 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 the material filling theni is of thisage. The channel proper may have bcenin process of formationever since the close of the Carboniferous period. Th
. [Reports vol. I-XIII]. 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 the material filling theni is of thisage. The channel proper may have bcenin process of formationever since the close of the Carboniferous period. They differ^^^Ijrd^ift^from the first class of channels in that the filling material con-sists of loose clay, sand and gravel similar to that spreadgenerally over the surface of the surrounding country with whichit is contemporaneous in age. In Fig. 10 such a buried channel. Fig. 10. Diagram illustrating burled channels ol pre-Glacla} age. is represented. It is to be distinguished, further, from one ofthe first class, in that the filling material is not a Coal Measurerock and is never the equivalent of any one of the members ofthat formation, which may sometimes be the case with the firstclass, as is alluded to on p. 36. Such channels occur north of theMissouri river and are best developed in the drift covered areaof the northern portion of the State. They have been recognized °^gaoh!°° ^in Putnam, Sullivan and Linn counties, and doubtless occurelsewhere. When encountered in coal mining the coal is cut offabruptly, and, sometimes, the influx of water and sand is sostrong as to cause the abandonment of the mine. These chan-nels, therefore, not only reduce the area of the coal but furtherpresent obstacles to the operation of mining. 4. All coal beds have been deposited in basins of greater orless area and depth; they constituted, at the time of formation
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