3l8 TRANS. ST. LOUIS ACAD. SCIENCE. 



The early Qiiatenary submergence thus chronologized has already 

 been recognized in central Missouri by Dr. J. W. Spencer.* 



THE INDURATED ROCKS. 



Only the more important of the exposures observed are noted 

 in the following pages. The sections are located upon the map, 

 Fig. I, and most of them are represented graphically in Fig. 5. 



Exposures on Salt River. — The best exposure observed on 

 the river is at Bengee's coal mine, a mile south of the Hann. & 

 St. Jos. railway-. 



1. Bengee Section. 



Feet. 



1. Compact light gray limestone with conchoidal fracture, 

 magnesian in spots and bands; no identifiable fossils but 

 abundant obscure shell impressions 3J- 



2. Thinly laminated bright black fissile shale, containing 

 large ovoid nodules 5 



3. Coal, about 2 



4. Under clay passing into a slope with blue loam at base, 

 about 13 



5. Impure concretionary dolomite in a discontinuous ledge... i 



6. Argillaceous shale, yellow above and blue below, wea- 

 thering into tenacious c'ay 4j 



7. Discontinuous bed of friable dolomite ^ 



8. Argillaceous shale, incoherent above but firm below 5 



9. Massive compact limestone, containing abundant Producti 

 (including P. (squicostatus), forming a single continuous 

 ledge I 



10. Blue argillaceous shale, quickly weathering into clay, 



abounding in detached valves of Chonetes 7ncsoloba 3 



The section extends from near the summit of a low bluft^to the 

 bottom of the river channel. In addition to affording one of the 

 best series of strata observed within the area, it is of interest in 

 that it exhibits what appears to be a slight local misplacement in 

 the lower strata of the section : the /'r(?<//'/c///.s--bearing limestone 

 and the underlying shales being at one point thrown upward per- 

 haps three feet above the general level in a sharp-crested anticli- 

 nal, quickly fading out in both directions. The flexure, if such 

 it be, appears to be lost in the superjacent shales, and was not 

 observed to aflect the coal seam. It is claimed that the coal here 

 is 3 feet thick, but the above estimate — two feet — cannot be far 

 wrong, though the seam was not measured. 



* "Sand-bowlders in the Drift, or subaqueous Origin of the Drift in Central Missouri," 

 Am. Naturalist, vol. xxi., 1SS7, 917-21. 



