112 PROCEEDINGS OF WASHINGTON MEETING. 



Summarizing, therefore, we arc inclined to maintain the view that the move- 

 ments which originated this uplift were in Silurian times, even Lower Silurian, and 

 were consequent upon the deposition of the greal mass of Lower Silurian strata in 

 the sea surrounding the Archean archipelago. Further, the absence, in places, of 

 Upper Silurian and of Devonian beds under the lower Carboniferous strata, which 

 lap upon the sides of this Lower Silurian dome, shows that this early and first up- 

 heaval was extensive, and that large areas were lifted at that time above water 

 level to be submerged later in the Carboniferous seas for the deposition of the 

 lower Carboniferous limestone, the limits of which are outlined on the map form- 

 ing figure 25.* The pre-Carboniferous submergence was sufficient to allow the 

 waters to reach well up over the sides of the Ozark area and possibly great enough 

 to place it entirely beneath water level. Uplifting began again, however, soon 

 after this; so that, at most, only a thin deposit of lower Carboniferous rocks was 

 formed over the Ozark dome, which was subsequently entirely eroded. This up- 

 rising continued, perhaps intermittently, until after the end of the earlier Carbonif- 

 erous period, when the rocks of that formation were brought above the waters and 

 were subjected to extensive subaerial erosion. At or near the beginning of the 

 Coal Measure period, submergence began again and continued until, and probably 

 beyond, the close of that period. The Ozark area remained above the waters 

 during this submergence, however, and has continued so ever since ; the present 

 eastern limits of the Coal Measures being approximately the same as originally 

 outlined. 



The Phenomena of the Coal Measures. 

 Distribution and Hypsometry. 



The Coal Measures of Missouri cover the western and northwestern portion of the 

 state, occupying an area of some 23,000 square miles.t The general outline is familiar 

 to many, but, for purposes of ready reference, it is given on the small sketch map 

 forming figure 25. The altitude of the surface within this area varies from about 

 000 feet to nearly 1,300 feet. Along the marginal lines of the Coal Measures, 

 from northeast to southwest, the following are the approximate altitudes at succes- 

 sive points on the summits between drainage channels: Kirksville, 975 ; Macon, 

 886 ; Mexico, 798 ; Moberly, 807 ; Fayette, 800 ; Boonville, 750 ; Sedalia, 007 ; Clinton, 

 807; Nevada, 870; Joplin, 1,018. 



In the interior, along the western border of the state, the following are the alti- 

 tudes at successive points located similarly topographically : Kansas ( 'ity, about 050 ; 

 Leavenworth, about 1,000; Plattsburg, 1,000 ; St. Joseph, about 1,050; Savannah, 

 1,100; Oregon, 1,100; Maryville, 1,200; Watson, 1,100. 



Along the margin the Coal Measures may be considered to thin to a feather edge, 

 while in the extreme northwestern corner of the state they have an aggregate thick- 

 ness of perhaps 2,000 feet, and consist of probably more than 200 strata. 



*In a paper entitled "The Missouri River." published in American Geologist, September, 1889, 

 Professor Broadhead states, on page 154, that the < >zark plateau " began to rise just after the < 'ana. 

 dian. . . . From the Canadian to the beginning of the lower Carboniferous it was dry land. It 

 then became sufficiently depressed to receive limestone deposits near its outer margin during the 

 early Subearboniferous, a few l>e<ls of the later Chouteau, and early Burlington." These state- 

 ments lead one to the conclusion that he lias abandoned the belief of the Carboniferous age of the 

 uplift referred to on page im, and that the writer's opinions, so far expressed, are substantially in 

 accordance with those held by Professor Broadhead. 



f Report Mo. Geol. Survey, 1872, pari ii. p. 5. . 



