530 IOWA ACADEMY OF SCIENCE Vol. XX v, 1918 



limestone in i)laee can be seen. However, amouy: loose l)locks 

 and debris it was found that the layers quarried were eight 

 inches of li.uht gray iron stained limestone, and fourteen inches 

 of bluish gray limestone in one layer. A few fossils were found 

 sufficient with the lithoo^cal character of the limestone to jus- 

 tify a correlation with the Tarkio. 



At the old Keystone mill site near Red Oak on the Nebraska 

 City branch of the Chicago, Burlington & Quincy railway, in the 

 first bluft* south of the main line, an excavation 'shows Cretaceous 

 sandstone, yellow, friable, massive, cross bedded, with concre- 

 tions of limonite. The thickness exposed is twelve feet, eight 

 feet of which is above the level of the railroad track. At the time 

 of the visit of Doctor Calvin and the writer eighteen years ago 

 about one hundred yards south of tbis sandstone pit an outcrop 

 showed above the railroad track ten feet of Cretaceous shale, 

 poorly bedded, arenaceous, with limonite concretions, gradually 

 passing upwards into fifteen feet of light gray shale, free from 

 concretions, jointed, and well bedded; below the railroad track 

 was nine or ten feet of contorted friable sandstone resting un- 

 conformably on eighteen inches of light gray Carboniferous lime- 

 stone in one layer. Doctor Calvin at that time collected speci- 

 mens of Angiosperm leaves in this sandstone. This is probably 

 the same locality from w^hich Meek collected fifty years ago. A 

 short distance still farther south, where the river at high water 

 washes the railroad embankment, is the place where White ob- 

 tained his section showing Cretaceous shale extending down to 

 the limestone ledge at water level in the river, with absence of all 

 sandstone. 



SECTION NEAR RED OAK, IOWA GEOLOGICAL SURVEY, 

 VOL. 1, 1870. 



Feett 



T'ine grained sandy and clayey micaceous shale 20 



Eluish compact impure limestone IM; 



Total 2iy^ 



At the present time the railroad eml)ankniciit has been rein- 

 forced to g-uard against erosion by high watei- in the river, cov- 

 ering all exposures below the level of the track. 



A short distance farther south, on tlie nortli side of a deep 

 ravine, close to the railroad right-of-way, at an (>levation of two 

 feet above the track and thirteen feet above extreme low water in 

 the river, is a one foot ledge of yellow Carboniferous limestone in 



