LITTLE SALINE LIMESTONE. 213 



CHAPTER IV 



THE FAUNA OF THE LITTLE SALINE LIMESTONE IN 



STE. GENEVIEVE COUNTY 



by 



GRACE ANNE STEWART 



INTRODUCTION. 



The Little Saline limestone is named from the Little Saline 

 Creek in Ste. Genevieve County, Missouri, along the course of 

 which the beds outcrop to a limited extent. The formation con- 

 sists of a pure white, or faintly pink, crystalline limestone, some 

 beds of which are replete with finely preserved fossils. From a 

 detailed study of the fauna it is obvious that the formation may 

 be divided into two horizons or zones, a lower one in which upper 

 Oriskany species predominate with a few Helderbergian hold- 

 overs, and an upper zone in which the upper Oriskany species 

 are associated with some Onondagan forms. 



The lower beds contain the larger portion of the fauna, 

 for of the 102 species which have been identified, 77 occur here, 

 with only 44 in the upper beds, 19 persisting through both 

 horizons. Of the total number 26 species and 1 variety, or 

 approximately 28 per cent of the entire fauna, belong to hitherto 

 undescribed species. 



The marked resemblance which exists between the Little 

 Saline and the Oriskany fauna of the Appalachian trough, particu- 

 larly in New York and Maryland, proves the contemporary age 

 of the faunas, and the extension of the Oriskany sea into south- 

 eastern Missouri. The fauna was first discovered in 1913, and 

 its presence in this region is of great interest, since its occurrence 

 proves the westward extension of the typical Oriskany fauna for 

 at least 500 miles further than was formerly supposed. 



Typical upper Oriskany faunas have been recognized at a 

 later date by C. 0. Dunbar, 1 in western Tennessee, an occurrence 

 which indicates a southward extension of the Oriskany sea for 

 at least 200 miles. 



The following correlation table shows the species which are 

 present in the Little Saline limestone, and their occurrence else- 

 where in the Appalachian trough and in Tennessee. 



iDunbar, C. O., Geol. Surv. Tenn., Bull. 21, p. 68, 1919. 



