248 GEOLOGY OF ILLINOIS. 



No. 2 of the section is first met with in following down Jordan creek, about 

 two miles north of Fairmount, in the south half of section 27, town 19 north, 

 range 13 west. It is here a very shaly rock, and of no practical value; but in 

 sections 20 and 21 of the same township, above and below the Conkeytown 

 bridge over Salt Fork, it furnishes some more compact beds, which have been 

 quarried for foundations and bridge abutments. One of these layers, near the 

 bottom of this bed, from one to two feet thick, is a very solid stone, and would 

 pay for quarrying if the quantity were greater. From its outcrop along the base 

 of the river bluffs, considerable quantities have been gathered for use at Fair- 

 mount. Less compact layers, from the upper part of this bed, are quarried, to 

 some extent, at Davis's quarry, in the south part of section 31, of this township, 

 and are said to become hard and durable under the action of the weather, on 

 account of the contained oxyd of iron. Other openings in this neighborhood 

 are now abandoned. 



These are the highest beds exposed upon Salt Fork. Ingoing but short dis- 

 tances up and down the stream, we come upon the underlying thin coal seam, 

 with its accompanying black shales and argillaceous limestones, so that this is 

 evidently a point of the north and south axis of the synclinal between the east- 

 ern border of the coal field and the axis of elevation which has been noted as 

 running about south 33 east from the neighborhood of LaSalle. This latter 

 axis must evidently pass through the adjoining county of Champaign, though 

 the upper strata were there so extensively removed before the Drift period, that 

 no outcrops now exist to show what the actual dip is. 



Through the eastern part of Vermilion county, the dip is mainly to the south- 

 west, at a small angle, though local dips are very various. In ascending Salt 

 Fork, these characters are constant until we pass the west line of township 19 

 north, range 12 west, where the dip becomes much more rapid for a few miles, 

 and until it is reversed at the synclinal, above which the eastward dip is very 

 gentle. 



Nos. 4 to 12 of the section are exceedingly variable in their characters and 

 succession, so that it is very difficult to give a general section which shall fairly 

 represent their different aspects. Their most noticeable components are the 

 bands of argillaceous limestone near the top of the series, which are sometimes 

 compact and sometimes marly, but always contain great numbers of fossils, espe- 

 cially Hemipronites crassa and Productus longispinus, together with P. costatus, 

 P. Rogersii, P. scdbriculus, Athyris subtilita t Spirifer cameratus, S. plano-con- 

 vexa, Spiriferina Kentuckensis, Retzia, punctilifcra, Cyathoxonia proUfera, 

 plates of Zeacrinus, and various Bryozoa, The black shales which appear, some- 

 times above, sometimes below, and sometimes between these limestone bands, 

 are sometimes soft and sometimes slaty; under all which variations, we find them 

 containing a few specimens of Dlscina nitida, Liwjula^m^. rhombic fish-scales. 



