372 The A )/ieri'can Geo/or/i'.sf. December, ISHT 
Fig. 2 was drawn to illustrate this occurrence and to correlate 
the subdivisions of the Cambrian sedinientaries of this 
locality. By reference to this chart, it is seen that the 
average dip of the sedimentary strata, as they appear in the 
river gorge, makes the sandstone conglomerate correspond to 
the well known break between the St. Lawrence and the over- 
lying Jordan. Further, this St. Lawn-enee-Jordan* interrup- 
tion in the continuity of the strata, is the only one thus far 
known commensurate with the formation of such a conglom- 
erate. The lithologic characters and faunal content of the 
matrix are more closely allied to those of the Jordan than to 
any other formation. For the Jordan is an extensive sand- 
stone formation, characterized by thick, coarse cross-bedding, 
well agreeing with the abundant supply of material, derived, 
in part at least, from the destruction of the St. Lawrence and 
earlier strata. It appears then that this sandstone conglom- 
erate represents the extreme northern limit of the Jordaii 
sandstone, with which it should be correlated: and the time 
break indicated was great enough to secure a solidification of 
earlier formations sutficient for the construction of a conglom- 
erate from their debris. 
The St. Lawrence Shales. From a well in the S. W. ^, S. W. 
i, S. W. i, Sec. 1, T. 38 N., R. 19 W., were obtained two spec- 
imens of a sandy shale which resembles, in lithologic charac- 
ters, the St. Lawrence shales found at Osceola Falls. This oc- 
currence is 850 feet above sea level, and therefore woutd agree 
in altitude with a continuation of the St. Lawrence shales in 
this direction. It must be admitted, however, that with the 
approach of all of these formations to the immediate vicinity 
of the cliffs of igneous rocks, beyond which none of them are 
known to extend, the lines of separation between shales and 
sandstones become less sharply defined. 
The Basal Sayulstone Series. Among all of the terms that 
have been used from time to time to designate certain forma- 
tions and groups of formations in southeastern Minnesota, 
not a single one has been limited to the sandstone and shale 
series, lying between the St. Lawrence formation and the Ke- 
weenawan rocks, with sufficient constancy and definiteness to 
warrant genera! acceptance. A recent reference to these rocks 
*Bull. G. S. A., vol. 6, 1895, p. 173, Magnesian Series, N. W. States. 
