File:Bulletin (1910) (14597314719).jpg

Identifier: bulletin195unit (find matches)
Title: Bulletin
Year: 1910 (1910s)
Authors: United States. Bureau of Mines
Subjects: Mines and mineral resources Mines and mineral resources Mining engineering
Publisher: Washington U.S. Govt. Print. Off. (etc.)
Contributing Library: Gerstein - University of Toronto
Digitizing Sponsor: University of Toronto

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LEGEND PLEISTOCENEGlacial Drift -?; PENNSYLVANIANCoal Measuresr La Salle LsLCoal No. 2 DEVONIANLimestone Z2Z SILURIANNiagara Limestone -— OROOVICIAN Maqucketa Shalef^:^^Trenton • Galena LimestoneSt Peter SandstoneLower Magnesian STEREOGRAM OF LA SALLE, ILL., AND VICINITY, SHOWING THE GENERAL GEOLOGIC STRUCTURE AND STRATIGRAPHY.(Courtesy of F. W. Do Woll, dircotor, Illinois State Oeologlcal Survey.) GRAPHIC PRESENTATION OF UNDERGROUND CONDITIONS. 51 val. Isochor lines are drawn in somewhat the same way as con-tour lines. A light line is drawn from one well to another well andthis is proportionally divided at definite intervals according to the
Text Appearing After Image:
Figure 11.—Convergence map showing by lines of equal distance (isochor lines) thevertical distance between the Ames limestone member and the hundred-foot sand inthe Sewickley Quadrangle. The lines are drawn to pass through points on the Ameslimestones having an equal distance above the top of the hundred-foot sand. Inareas left blank the Ames limestone has been removed by erosion. amount of convergence found between the two wells. The intervalused is usually a multiple of 5 or 10. The isochore lines are formedby connecting, for each given interval, or distance between key bed 52 UNDERGROUND CONDITIONS IN OIL FIELDS. and oil sand, all the points representing that distance. As in draw-ing contour lines, good judgment is necessary. With a given well elevation, a convergence map, and a contourmap of the key bed, the depth of the oil sand at any point on the Tnapscan be predicted. USE or CONVERGENCE MAP TO PREPARE A CONTOUR 31AP OF THE OIL SAND. The convergence map, prepared on transpare

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