File:Reports (1908) (14761886416).jpg

Identifier: reports9190miss (find matches)
Title: (Reports)
Year: 1903 (1900s)
Authors: Missouri. Division of Geological Survey and Water Resources
Subjects: Geology Mines and mineral resources
Publisher: Rollo (etc.)
Contributing Library: University of Illinois Urbana-Champaign
Digitizing Sponsor: University of Illinois Urbana-Champaign

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the sense that we usethe term, but rather a limestone bed, which has been dissectedunder somewhat unusual conditions. This Central marble boulder horizon is so persistent over alarge part of the area studied that it serves as an excellent datumplane from which to establish the contacts between the severalformations above and below. It actually divides the Davis forma-tion into two parts, an upper and a lower, and in much of the fieldwork it was found convenient to recognize this division. Thishorizon also serves a most useful purpose in recognizing and locat-ing faults, and in order to determine its exact elevation throughoutthe area covered by the special Flat River and Leadwood sheet aline of levels were run over its entire course. As stated above, fifteen different conglomerate beds have bsenrecognized in one continuous section of this formation, of whichcne occurs above the Central marble boulder bed and fourteen be-low. Of these fifteen beds eight are typical edgewise conglomer-
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DAVIS FORMATION. 37 ates as described by Nason in the Am. Journal of Science, Vol. XII,pp. 358-361, and seven are conglomerates of the ordinary type.The edgewise conglomerate beds all occur beneath the Centralmarble boulder bed. The conglomerate bed above the Centralboulder bed is dolomite, while all the others are limestone exceptin two instances, where they are magnesian limestone. The con-glomerate beds are not all continuous over the area, but appearand disappear at intervals, being replaced with hard, dense, crystal-line limestone. A good illustration of this may be observed in oneof the Illinois Southern railroad cuts north of Elvins. The ordinary type of conglomerate, with one exception, con-sists of roundish disc-like limestone pebbles embedded in a matrixof medium grained crystalline limestone. In the exception referredto dolomite pebbles are embedded in a matrix of dolomite. In thecase of edgewise conglomerates, flat lenses of fine grained limestoneare embedded in a medium g

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