352 THE GEOLOGY OF MINNESOTA. 



Fraxinus Americana, L. White ash. 



Carya alba, Nutt. Shag-bark hickory. At Lansing, and in the valley of the Cedar, one foot 

 in diameter. 



Acer saccharinum, Wang. Sugar maple. 



Carya amira, Null. Bitternut. 



Finns strobus, L. White pine. Along the rocky banks of the streams in the eastern part of 

 the county. 



Ulmus fulva, Mich. Slippery elm. 



Fraxinus sambucifolia, Lam. Black ash. 



Viburnum Opulus, L. High-bush cranberry. 



Rubus villosus, Ait. High blackberry. 



Juniperus Virginiana, L. Red cedar. 



THE GEOLOGICAL STRUCTURE. 



Of the older rocks the lower portion of the Devonian and the upper 

 portion of the Lower Silurian are found within the county, dipping toward 

 the southwest. The western portion of the county is known to be imme- 

 diately underlain by the Lower Cretaceous, without ascertainable eastern 

 limits. The underlying rock is nearly everywhere hid by the drift, and 

 for that reason the actual position of the boundaries of the formations 

 is unknown. It is possible, indeed probable, that the Cretaceous area 

 extends farther east through the northern part of the county, since traces 

 of it are found in the northern part of Fillmore county. The central and 

 northwestern parts of the county are underlain by the argillaceous sand- 

 stone, and associated shales, which are seen at Austin. In Pleasant Valley 

 and Racine townships u limestone which is the extension of the Galena and 

 Upper Trenton is found. This lies below the Austin rock. The Devonian 

 limestones, which overlie the Austin rock, occupy the southern and south- 

 eastern townships, and the western portions of Lyle and Austin, on the 

 west side of the Cedar river. The stratigraphy of the formations is as fol- 

 lows, in descending order. Nothing is known of their thickness, except 

 what can be learned from a study of their outcrops in other counties. 

 There is no reason to suppose they vary much in that respect from the 

 descriptions that have been given already of them in Fillmore and Olm- 

 sted counties. 



L 1. Blue clay. 

 Cretaceous. ? 2. White sandstone. 



( 3. Pebbly conglomerate. 



C 4. Limestone, fine grained, dolomitic. 

 Devonian. < 5. Limestone, coarse grained, dolomitic. 

 ( 6. Argillaceous sandstone. 



7. Calcareous shale. 



8. Limestone, dolomitic, with shale beds. 



