FILLMORE COUNTY. 293 



Upper Trenton and Galena.] 



The quarry of Mr. Enoch Winslow is on the same horizon as Mr. Tay- 

 lor's. It is situated on the bank of Sugar creek, S. W. J sec. 4, Fountain. 

 Another on the same horizon is that of John Johnson, two miles south 

 of Fountain. 



The green shales. The interval covered by the green shale (20 feet) is not 

 often seen well exposed. The uppermost layers have been seen in Fillmore 

 county only at Mr. Taylor's quarry above, but the lower layers are visible in 

 many places where the Trenton is quarried. When wet constantly this shale 

 becomes a plastic clay. Along the brow of the Trenton terrace it colors the 

 earth in nearly all roadways that cross it, and produces, by shedding the sur- 

 face water, very muddy spots, in which teams are sometimes mired. This 

 shale always lies in thin layers, and sometimes embraces continuous beds ot 

 blue limestone which are exceedingly fossiliferous. It also sometimes holds 

 fragments of limestone of the same kind, in the form of slabs. A great 

 many fragments of Ch&tetes Lycoperdon accompany this shale and i-oll 

 down the face of the weathered slope, besides crinoidal fragments, and 

 species of Orthis, Leptwna and Strophomena. 



The Upper Trenton and Galena. By the Iowa geologists the Trenton 

 limestone has been considered as embracing not only the lower calcareous 

 beds, and the green shales, but also a part of the overlying limestone strata, 

 fading off to the Galena formation upward by a gentle lithological change 

 in the rock. But since the Hudson River horizon actually covers every 

 thing of the Lower Silurian above the Trenton (in the absence of the Utica 

 slate) this distinction between the " Upper Trenton," of the annual reports; 

 and the Galena limestone, becomes one of much less importance, and of -still 

 less importance in counties farther north where the distinctive lithology ot 

 the Galena fades out altogether. Hence for the sake of convenience, if any 

 designation besides Hudson River, be needed, the term Galena may include 

 all the calcareous strata above the green shales, belonging to the Lower 

 Silurian. 



These calcareous beds, which have in part been denominated Galena, 

 and in part Upper Trenton, include a thickness of about 125 feet, and con- 

 sist of a bluish, or grayish, evenly bedded limerock varying from fine- 

 grained and compact, in the lower part, in layers of a few inches, to more 

 vesicular, sometimes arenaceous, and often magnesian, beds of one to two 



