TERRACES, ANCIENT CHANNELS AND RAPIDS. 539 



Along the course of the Missouri, in Saint Charles county below Dut- 

 zow, there is also a much eroded terrace consisting of a thick formation 

 of loess resting upon a rocls:y base. This rises to the height of about 200 

 feet above the present stream, is well shown at Dutzow, Augusta, and 

 less distinctly between the lower course of the Dardenne and the Mis- 

 souri. It seems to correspond in structure to the loess formation at 

 Alton. No northern drift is found upon it in the valley of the Missouri. 

 This also covers the peninsula between the Missouri and the Mississippi 

 in Saint Louis county as far south as Creve Coeur. Traces of loess at a 

 similar level are found at Cape Girardeau, and surrounding the lower 

 portion of the ancient rocky island at Grand Tower loess accumulation 

 is built up in terrace form to the height of 125 to 130 feet. This bears 

 evidence of being recently formed. It contains closed basins which have 

 not yet been opened by erosion. 



A small bowlder of greenstone was found at the height of about 80 

 feet above the Mississippi at this point. This may be considered equiva- 

 lent to the lower terrace, so well developed higher up. 



We should here speak of the withdrawal of the Missouri from certain 

 channels. The valle}^ passing through the southern part of Kansas City 

 may l)e considered an old channel of the Kansas river connecting with 

 the Big Blue. The Kansas river vacated this channel and emptied di- 

 rectly into the Missouri by its present course through what may have 

 been before a mutual flood-relief channel between these two streams. 

 This .took place about the time of the formation of the high terrace 

 already described. The change of the Missouri from the old channel 

 leading from Waverly southeast through Saline county may have been 

 caused in a similar way and about the same time by the Missouri pre- 

 ferring a similar flood-relief cliaunel between it and the Grand river. 

 More recently a similar change has taken place between the Little Blue 

 and the ^Missouri, east of Independence. The Little Blue runs now 

 north Av est to the Missouri from a point a little east of Independence ; but 

 from the same point a broad valley, largely occupied by ponds and 

 marshes, extends eastward to the Missouri near Napoleon. This valley 

 is but little elevated above the present flood plain of tlie Missouri. 



The only case of ancient rapids wliich has been distinctly observed is 

 that at Weston, a little north of Leavenworth. At that point there is 

 found on the Missouri side of the river a remarkable stratum of cobble- 

 stones and gravel 16 to 18 feet in thickness. Its base is about 140 feet 

 above the present stream. It reaches for a mile or more in the direction 

 of the river. It is composed mainly of limestone bowlders similar to the 

 strata which Professor Broadhead has designated as numbers loO to 152 of 

 his Upper Coal Pleasure section.^ About three and a half miles north of 



* Missouri Geol. Report, part 11, 1872, p. 92. 

 LXXV— Bur,i„ Geol. Soc. Am., Vol. 5. 1893, 



