412 PROCEEDINGS OF OTTAWA MEETING. 



river deposil flooring the entire flood plain, and unconformably below lies the 

 dense, tenacions blue or greenish Port Hudson clays, which underlie the flood plain 

 throughout. Thus the structure is similar to that of other parts of the "Delta." 

 save thai the deposits lie 20 or 25 feet higher. 



The configuration and composition of the dome indicate that it was originally a 

 part of the broad flood plain extending from the mouth of the Ohio to the Gulf, 

 and its exceptional altitude and general conformation suggest a localized uplift. 

 Moreover, several of the dry bayous enter Keelfoot lake squarely or obliquely, and 

 when this occurs there is no trace of delta-building, and both channel and natural 

 levees may be traced for long distances in the lake; indeed, for some distances 

 they may be traced throughout their extent and found to connect in the form of a 

 fairly definite drainage system. This absence of deltas indicates that the uplift or 

 deformation occurred suddenly. Furthermore, it is found that while great cypresses, 

 Sycamores and poplars, sometimes two or three centuries old, grow over the gen- 

 eral surface of the dome, no trees older than seventy or seventy-five years grow- 

 within the unoccupied bayous; from which it maybe inferred that the uplift 

 occurred at least seventy or seventy-rive years ago, and probably not much earlier. 



Reelfoot lake is a shallow water-body of irregular form, perhaps live miles in 

 average width anil twenty miles in length from north to south, lying between the 

 Lake county dome and the base of the upland scarp, a dozen t<> a score of miles 

 east of the river. Its depth increases very gradually from its western margin 

 nearly to the eastern shore, where at low water its depth is twenty or thirty feet. 

 At high water on the Mississippi its depth is some twenty feet more, since it then 

 becomes part of the general flood by which the Lake' county uplift is transformed 

 into a double island. The lake is not an uninterrupted sheet. Here and there, 

 particularly toward the western side, groves of sickly cypresses spring from its 

 bottom and half shadow- the water surface with puny branches and scant foliage, 

 and here and there throughout all portions of the water body, save in the channels 

 of the old bayous, gaunt cypress trunks with decaying branches stand, sometimes 

 a dozen to the acre, numbering many thousands in all. Moreover, between the 

 decaying boles, rising a score toa hundred feet above the water, there are ten times 

 as many stumps, commonly of lesser trees, rising barely to low-water level. Now. 

 while the subsurface structure beneath Keelfoot lake is not revealed, the phenomena 

 of the lake grade into the phenomena of the dome. The lake bottom is meandered 

 by waterways whose combined channels and natural levees prove them to be bayous 



similar to those of the Mississippi H 1-plain; along and between the bayous 



cypress stumps and boles are scattered just as they are distributed over much of the 

 modern flood-plain, and dry bayous and drowned swamps alike indicate that the 

 land beneath Reelfool lake was depressed. Moreover the transformation of the area 

 from land to lake without filling the old bayous by sediment indicates that the de- 

 pression occurred suddenly. Furthermore the presence of the cypress stumps and 

 trunks, particularly in the deep portions of the lake where the drowning must have 

 been complete, indicates that the date of the subsidence was not remote. 



The upland scarp overlooking the Mississippi flood ['lain on the east, from Baton 

 Rouge to the mouth of the Ohio, is everywhere mantled by loess or a loam of 

 closely related character, and the mantle, as well as the underlying rocks, is deeply 

 scored by erosion. Accor lingly the upland margin is made up of steep salients and 

 cusps and narrow divides separating a myriad ravines. Now, on approaching the 

 Keelfoot country from the north or the south, certain minor topographic features 



