STATE GEOLOGIST. 83 



10. Sandstone, coarse, thin bedded and quite soft, (545 

 A— F.) 



9. Flaggy sandstone, (545 G.) 



8. Thin shaly sandstone, passing down to a sandy shale, 

 containing much carbonaceous matter, and with oc- 

 casional partings of a substance composed of sand, 

 clay and carbonaceous matter finely comminuted, 

 (545, H— L.) 



T. Sandstone, shaly and flaggy, (545, N.) 



6. Sandstone, flaggy, striped with red, (545 0, and 544.) 

 Interval of 40 reds, up stream. 



5. Sandstone in thin layers, (543, A — B,) 20 in. 



4. Sandstone, thick bedded, mottled with red above, 



striped below, (543, C— D,) 4 ft 



3. Sandstone, with quartz pebbles, (543, E — F ) 



2. Sandstone, thin bedded, (543, G.) 



1. Sandstone, coarse, soft, very ferruginous, (543, H.) 

 Interval of 30 rods to collection of fragments be- 

 fore referred to. 



From this neighborhood to Jackson county, no outcrops of 

 rock are known ; but the arenaceous character of the drift 

 materials through Lapeer and Oakland counties and portions of 

 St. Clair and Macomb, renders it not improbable that the arena- 

 ceous strata of the Marshall and Napoleon groups would be 

 found underlying that region. 



In the southern part of the State, the Marshall Group is bet- 

 ter characterized and more fully distinguished from the Napo- 

 leon Group above. Throughout all the northern part of Hills- 

 dale county, we find a series of highly ferruginous sandstones, 

 generally very fossiliferous, and easily recognized. The ferru- 

 ginous matter is often collected into bands of iron-stone, 

 from one-fourth of an inch to four inches thick, sometimes 

 horizontal, sometimes oblique and sometimes concretionary 

 in their arrangement. From a brick red sandstone the rock 

 varies to pale red, yellowish and buff; and lewer down, becomes 

 yellowish-green, reddish-green, bluish-green and bluish. At the 

 lowest points, as in Noe's well at Jonesville, it becomes a 

 bluish, micaceous, thin-bedded, shaly sandstone, and thus pas- 

 ses into the shales of the Huron Group below. 



Good exposures of the formation may be seen in the quarries 



