2 LIFE OF THE PLEISTOCENE 



A section of the shore north of the university campus, Evanston, studied by 

 Prof. O. C. Marcy, presented the following strata : 



Section of beach at Evanston 



1. Surface soil 1J^ feet 



2. Fine sand iy 2 



3. Coarse sand r. 2J^ 



4. Fine sand 2 



5. Gravel 1% 



6. Fine sand containing tree trunks, etc 1J^ 



7. Dark colored marly bed, the lower part peaty 1J^ 



8. Fine sand 3J4 



9. Blue clay (drift) Z]/ 2 



Mr. Bannister thus comments upon these deposits and the life contained 

 therein: "In addition to the beds given in the section, there may be seen at 

 one or two points, a thin seam of vegetable mould, resting immediately on the 

 blue clay of the drift, and at the base of the true lacustrine deposits. In this 

 seam there have been found many pieces of wood and stems of small trees, 

 apparently cedar, and, in one instance at least, the stump with the roots pene- 

 trating the clay below to a depth of two or three feet, evidently in the position 

 of its natural growth, thus showing that the land was at that time sufficiently 

 elevated to support trees. Water-worn pieces of wood, also apparently cedar, 

 are quite frequent in the stratum of sand above the clay (no. 8 of the section). 



"The bed no. 7 of the section, may be followed for upward of half a mile 

 along the beach, and is also frequently met with in digging wells in the town. 

 An occasional fragment of a bone, and a great abundance of fossil fresh-water 

 shells are found in this bed. The shells are all of existing species of Unio, 

 Pisidium, Physa, Lymnea, Planorbis, Valvata, Amnicola, Melantho, Ancylus, 

 etc. Immediately above this bed, and generally resting upon it, in the stratum 

 of sand no. 6, we find many stems of large trees, chiefly oak, which seem to have 

 drifted to their present resting place as the waters of the lake gradually en- 

 croached upon the marsh. 



"In the eastern part of the county, along the lake shore, we often find the 

 black surface soil of the small wet prairies underlaid by a bed of quicksand, 

 containing fresh-water shells of the genera Melania, Unio, etc., which belong 

 to the same period as the lake ridges. Instances of this kind of a prairie may 

 be observed along the fines of most of the railroads running southwesterly from 

 Chicago, and on the Milwaukee railroad running north. Indeed, such prairies 

 may be seen at the present time, in the process of formation, at various points 

 along the lake shore in this county and elsewhere. The bed no. 7 of the section 

 was probably deposited under conditions very similar to those of the formation 

 of these prairies, in the bottom of a shallow lagoon or marsh, and serves to show 

 how gradual was the process of submergence or emergence during which it was 

 formed. " 



