SEVENTH ANNUAL MEETING 



75 



1. Buchanan, Berrien County 



Two miles west and a little north of Buchanan, Berrien 

 county, is a stretch of low land known as Bakertown marsh. 

 The marsh was previously a lake about three miles long and 

 a mile wide, but is now grown up in marsh grass and is prac- 

 tically dry. A ditch about a mile in length drains the marsh, 

 and exposes the strata, which exhibit the following section : 



VIII. Marsh bog 16 inches 



VII. Recent peat 20 inches 



VI. Peat and drift wood 10 inches 



V. Lake silt (no shells) 8 inches 



V. Semi-ligneous peat 12 inches 



III. Shells and lake drift 8 inches 



II. Blue Clay 7 inches 



I. Quicksand 7 to 10 feet 



The thickness of the sedimentary deposits above the sand 

 is 81 inches, or 6 feet, 9 inches. 



The quicksand (stratum I) evidently represents the period 

 of Lake Dowagiac when the glacial waters rushed down the 

 lake into the Kankakee River, loaded with sediment. The 

 clay, (stratum II), represents a quieter stage, after the main 

 drainage had shifted to the Chicago outlet. Stratum III prob- 

 ably represents the bottom of a larger St. Joseph River, for 

 the species of naiads represented are mostly of the river type. 

 An arm of Lake Chicago extended up the St. Joseph River 

 from Benton Harbor to about the vicinity of Berrien Springs* 

 and the river drained into this extension of Lake Chicago. 



The fluviatile mollusks may have reached this locality from 

 two sources ; ( 1 ) , by way of the Chicago outlet, across Lake 

 Chicago and up the St. Joseph River; or (2), by way of the 

 Kankakee when it was connected with the St. Joseph and 

 Dowagiac rivers via South Bend. The mussels are mostly of 

 the river type and their natural migration route would be by 

 way of a river. Just how long after the formation of Lake 

 Chicago the St. Joseph-Kankakee drainage persisted is not 

 definitely known, but it is believed to have continued for some 

 time in a more or less modified form. The naiades represent a 

 climate fully as warm as the present and they could not invade 

 the waterways of the icy drainage. Certain boreal types of 

 mollusks could and evidently did take advantage of this water- 

 way at an early stage. It is probable that both drainages were 

 used and the fauna represents a mixture of the two migra- 

 tions. This stratum may be safely correlated with the Tolles- 

 ton stage of Lake Chicago. 



2. See Leverett, Illinois Glacial Lobe, plate XV. 



