402 



REPORT OF STATE GEOLOOIS'l . 



while in southeastern Indiana they are non-magnesian limestones 

 or limestones with a very small percentage of magnesia. All of 

 the available evidence appears to indicate that there was a suc- 

 cession of periods of gradual and areally progressive development 

 of the Cincinnati geanticline from Clinton time to the close of the 

 Louisville epoch. The last of these intervals of uplift terminated 

 Silurian deposition in this area and extended the land conditions 

 to the westw^ard of most of the present outcrops of the Silurian in 

 southern Indiana. The evidence of the last phase of the uplift is 

 found in the unconformity which has been shown to exist between 

 the Silurian and Devonian both in northern and southern Indiana.'* 

 At Harris City the Geneva limestone, which is the basal Devonian 

 formation, rests directly on the Laurel limestone; the Waldron 

 shale and the Louisville limestone both being absent. Nine miles 

 west of this point both the Louisville limestone and the Waldron 

 shale are present, the latter having about its maximum faunal de- 

 velopment. The absence of the two upper formations of the Silu- 

 rian at Harris City is the result either of erosion during the inter- 

 val represented by the Siluro-Devonian unconformity or of non- 

 deposition resulting from a retreating shore line at the end of the 

 Laurel limestone epoch. The extension of the latter formation 

 20 miles eastward of Harris City, without any known out-liers 

 of the Louisville limestone or Waldron shale, favors the latter 

 hypothesis. 



A map and report by Mr. J. A. Price^ affords important evidence 

 in this connection. Mr. Price's map attempts to show the eastern 

 limit of the Waldron shale across Decatur County, a north-south 

 distance of about 30 miles. The field work was evidently done with 

 considerable care, but the line which purports to be the eastern 

 limit of the Waldron shale marks in reality the parting between 

 the Geneva limestone (Devonian) and the Laurel limestone (Silu- 

 rian). The map, which shows all of the Waldron shale outcrops ob- 

 served by Mr. Price, indicates that these are to be seen frequently 

 three to ten miles west of his assumed eastern limit of the shale, 

 but not a single outcrop is shown on or near the line supposed to 

 represent its eastern border. It appears clear from the report*" that 

 wherever the uppermost Silurian beds were observed near this line 

 they represent the Tiaurel limestone and are followed directly by 



" Kindle, E. M. The Devonian J'ossils aijd stial igiaphy of Indiana. 25th Ann. 

 Itept. Dept. Geol. and Nat. Kes. of Ind., 1901, pp. 557, p62, 566, pi. 16. 



''"A i-pporl uiiou thf Waldron shale and ils liuii/.oii." L'Ifli Ann. Kept. Fnd. 

 l>f'.])t. Geol. and Nat. Res., 1000, pp. 81-14H. 



