SILURIC FAUNA FROM SOUTHERN MICHIGAN 



541 



physical conditions and fauna of the Siluric may be supposed to liave lingered 

 in Michigan longer than elsewhere. 



In I'egard to this question entire agreement has not been reached, and there 

 is a chance for light from new facts, but as the problem has direct bearing on 

 certain knotty questions in New York. Canada, and Ohio, it seems well to give 

 the ascertained paleontologic facts to help others (Lane). 



Figure 1. — Section across the Detroit River 



8. Sibley quarry and borehole. 



G. 1. Grosse Isle. 



Amh. Amherstburg channel. 



And. Anderdon quarry. 



Dd. Devonic — Dundee limestone. 



SI. Siluric — Lucas dolomite. 



Sa. Siluric — Amherstburg dolomite. 



Sand. Siluric — Anderdon coral limestone. 



Sid. Siluric — Flat Rock dolomite. 



Ss. Siluric — Sylvania sandstone. 



Monroe Formation 



SALT SHAFT EXPOSDRB AND SECTION 



In December, 1906, the salt shaft of the Detroit Salt Mining and Manufactur- 

 ing Company penetrated a remarkable coral reef with a coral fauna of Devonic 

 affinities deeply embedded in the Upper Siluric strata of Michigan — the Monroe 

 formation. The existence of this reef had been suspected from the chips of the 

 various wells drilled in this region,^ while many years ago T. Sterry Hunt re- 

 ported a similar coral horizon at a depth in the Upper Siluric beds of Goderich, 

 Canada. Hall identified^ the fragments obtained from the Goderich wells with 

 corals known otherwise only from the Onondaga limestone. 



The section of the salt shaft is as follows, in descending order : 



(Elevation of mouth of shaft, 575 feet above tide.) Feet Feet 



Drift 83 83 



Dundee limestone, mostly a very pure calcarenite, rich In fossils, 



representing the lower Middle Devonic 63 146 



DiS CONFORM ITT :* 



"Lucas" dolomite, a hard, very porous dolomite of a lutaceous 

 texture, and full of cavities left by dissolved gastropods and other 

 fossils 189 335 



Intercalated Umestone {Anderdon limestone), containing the coral 

 fauna. The rock is a pure calcarenite (lime sand rock), in which 

 the corals are embedded 38 373 



Flat Rock dolomite, similar to the upper dolomite, but more com- 

 pact, and with few fossils 47 420 



DlSCONFORMITX : 



Sylvania sandstone, a pure silicarenite or quartz sand rock 117 537 



= Michigan Geological Survey, vol. v, pt. ii, pp. 27, 28, and plates of Monroe, Mount 

 Clemens, Port Lambton, Port Huron, etc. 



^ Transactions of the American Institute of Mining Engineers, vol. v, p. 538 ; also 

 Geol. Surv. of Canada, Report of Progress, 1876-7, pp. 221-243. 



* The hiatus supposed to be marked by disconformity was not very apparent In the 

 upper shaft (Lane). 



