STKA'I'KIK'AIM n' OF 'Vl\K WALDRON SIIAI.K, 



397 



Hole near I hii'lsville. The evidence which he presents, however, is 

 not conclusive and may be equally well accounted for by local 

 warping of the beds. lender the influence of a gentle westerly dip,, 

 averaging- probably about W to the mile, the Waldron shale passes 

 under the later formations to the westward. The westerly dip 

 and slight thickness of the formation combined with the absence 

 of very strong topographic relief confines the outcrop of the Wal- 

 dron shale to a rather narrov^ north and south belt. Although a 

 very thin formation the Waldron is very persistent and extends 

 southward from southern Shelby and Rush counties to the Ohio 

 River, a distance of about 85 miles. The Waldron shale is not 

 known north of the central part of the State. The heavy mantle 

 of drift to the north of its northernmost exposures in Rush and 

 Shelby counties conceals a large area in which important strati- 

 graphic changes take place, the precise nature of which is unknown. 

 All that we know certainly about them is that they result in a 

 Silurian section in the Wabash Valley in which neither the Wal- 

 dron shale nor its two accompanying limestone formations have 

 been identified. It may be that the Cincinnati geanticline which 

 is believed to have been in existence during the Waldron shale 

 interval, as pointed out elsewhere in this paper, swung to the west- 

 ward across north central Indiana making distinct marine basins 

 in northern and southern Indiana. Certain differences in the 

 faunas as well as the stratigraphy of the Silurian of the northern 

 and southern Indiana sections could be cited in support of this 

 hypothesis. 



From the Shelby county localities southward the AValdron shale 

 can be seen in numerous sections. In the northern part of its area 

 of outcrop the approximate position of the Waldron shale is in- 

 dicated when it does not outcrop by the junction of the Louisville 

 limestone lying above it and the Geneva limestone. The latter, 

 which is the lowest division of the Devonian, is a chocolate or buff 

 colored saccharoidal magnesian limestone presenting a marked con- 

 trast with the lighter colored Louisville limestone. These two 

 formations as previously shown by one of the writers* and others" 

 are unconformalDle. 



The Louisville limestone decreases from a thickness of 50 feet or 

 more at the Ohio River to less than ten in many places in the north- 

 ern part of the Waldron shale- area. 



a Kindle. 25th Ann. Kept. Ind. Dept. Geol. and Nat. Res. 1901, p. 557, pi. 16. 



^ Foerste. 22d Ann. Kept. Ind. Dept. Geol. and Nat. Res., 1898, pp 233-234 ; 

 Price, 24th Ann. Rept. Ind. Dept. Geol. and Nat. Res., 1900, pp. 99, 121 ; Elrod, 

 Proc. Ind. Acad. Sci., 1901 (1902), p. 210. 



