ILLUSTRATIONS. 



Page. 



Tlate I. Logs of the Seaman and Rudd wells and a generalized log for north-central Texas In pocket. 



II-V. Species of Orthaulax ; 33-37 



VI. Alinement chart for graphic computation of thickness of strata 44 



VII. Alinement chart for graphic computation of depth to a stratum 48 



VIII. Alinement chart for graphic solution of right triangles 50 



IX. A, Coconino sandstone and Kailiab limestone in Hurricane fault scarp, (i miles south of Hurri- 

 cane, Utah; B, Closer view of middle part of scarp shown in A: C. Upper part of Kaibali 

 limestone and basal member (Rock Canyon) of Moenkopi formation in Virgin Canyon, 1^ 



miles west of Virgin City, Utah SS 



X. A, View northward toward Smith's Mesa from a point just south of Virgin City, Utah: B. 



Panorama along east side of Coalpits Wash near Grafton. Utah 59 



XI. A. Chinle formation and overlying massive Jurassic sandstone in Zion Canyon above Spring- 

 dale, Utah: B, Cross-bedding in white upper part of massive Jurassic sandstone 12 miles 



north of St. George, Utah 02 



XII. A, Group of cinder cones of late date and associated lava. r)iamond Valley, 12 miles, north 



of St. George, Utah: B. Nearer view of larger cone of group shown in A (ifi 



XIII. A, Shinarump conglomerate resting on upper Moenkopi shale and sandstone. Smith's Mesa. 

 3 miles north of Virgin City, Utah: B. Late basalt flow resting on a conglomerate of basalt 



and other bowlders, on road from Toquerville to La Verkin, Utah (57 



XIV-XXVIII. Foraminifera of the Byram marl 107-122 



XXIX-XXXV. Foraminifera of the Mint Spring calcareous marl 146-152 



XXXVI-XL. Fossil plants from the Woodbine sand 181 



XLI. A, Hills of chloritic schist at the northern end of Big Horn Mountains, near Palo Verde mine, 



Maricopa County. .\riz.: B. Gonzales Wells, Dome Rock Mountains, Yuma County, Ariz.. 184 

 XLII. A. A plug of latite of Tertiary age in the Dome Rock Mountains, about 4 miles southwest of 

 Quartzsite, Yuma County, Ariz.: B. Black Butte, Cactus Plain, near Osborne's Well, Yuma 



County, Ariz 185 



XLIII. A, Osborne Wash, about 2 miles southwest of Osborne's Well, Yuma County, Ariz.; B, Saddle 



Mountain, Maricopa County. .\riz.. looking south 188 



XLIV. A, Bank of wash near Woolsey Tank, Gila Bend Mountains, Maricopa County, Ariz. ; B, Woolsey 



Tank, ( iila Bend Mountains. Maricopa County. Ariz 189 



XLV. Reconnaissance geologic map of the lower Gila region, Ariz In pocket. 



XLVI . <!)sage Rock, about 1 mile north of Belvidere, Kans 202 



XLVII-LXI. Fossil plants from the Cheyenne sandstone 225 



Figure 1. Outline map showing the position of the Seaman and Rudd wells, north-central Texas, and their 



relation to the " Bend arch " 6 



2. Geometric representation of the thickness of a stratum when the dip of the stratum and the relative 



positions of a point on the upper surface of the stratum and another on the lower surface are given. . 40 



3. Diagram to illustrate the method of calilirating the diagonal scale of a Z chart 43 



4. Diagram to illustrate the method of determining the locus of the curvilinear scale in an alinement 



chart consisting of two parallel straight-line scales and a c^u'vilinear scale 44 



5. Geometric representation of the distance to a stratum when the dip of the stratum, the position of a 



point on the stratum relative to the starting point of measurement, and the horizontal and vertical 

 directions of the line of measurement are given 47 



6. Right-angled triangle showing the relations of slope distance, horizontal distance, difference of eleva- 



tion, and vertical angle between two station points 48 



7. Diagram illustrating the coml>ination of three alinement charts for the solution of right-angled 



triangles 49 



8. Dia^am illustrating the use of an alinement chart for the solution of the tangent condition in right- 



angled triangles 50 



9. Trigonometric computer for the solution of such problems as are readily solved with the 12-inch 



straight slide rule 51 



10. Map showing localities where sections were measured in Washington County, Utah, and Mohave 



County, Ariz 53 



11. Cut in the Woodbine sand near Arthurs Bluff, Tex 180 



IV 



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