604 ABSTKACTS: GEOLOGY 



GEOLOGY. — Fauna of the so-called Boone chert near Batesville, Ark. 



G. H. GiRTY. U.S.Geol. Survey Bull. 595. Pp. 45 with 2 plates. 



1915. 

 The Moorefield shale which is typicall}^ exposed in the Batesville 

 quadrangle of northern Arkansas has generally been regarded as of 

 u]3per Mississippian age. Its fauna comprises a unique assemblage 

 of species remarkably different from the typical upper Mississippian 

 faunas of Missouri and Illinois, and in some ways reminiscent of the 

 Devonian rather than of the Carboniferous types of life. In the Bates- 

 ville region the Moorefield shale rests on a series of impure limestones 

 and cherts that have heretofore been identified as Boone limestone 

 because of their lithologic character. The Boone limestone is commonly 

 regarded as of Osage age and its fauna differs as widely from that of 

 the Moorefield shale as the Moorefield fauna differs from the faunas 

 of the typical Mississippian. Recent studies, described in this report, 

 have shown that the cherty beds underlying the Moorefield shale near 

 Batesville differ in lithology from the typical Boone farther west. 

 Aside from other less striking differences they contain an intercalated 

 bed or beds of black shale quite alien to the Boone. Moreover they 

 contain a fauna thoroughly unlike that of the typical Boone. Fossils 

 are hard to find in this series of cherty beds, but several small collections 

 were obtained, aggregating about 35 species. The noteworthy feature 

 of this fauna is that practically all the species occur also in the Moore- 

 field shale above, some of them being characteristic Moorefield types, 

 while practically none of them occurs in the typical Boonp. This 

 fact bears in two directions. The Moorefield shale, as defined, con- 

 tains at its base a few beds of dark gray, earthy limestone ; most of the 

 formation, however, consisting of black and green shale. The basal 

 beds, for which at one time the name "Spring Creek" limestone was 

 proposed, furnish nearly all of what is known as the Moorefield fauna. 

 Only a few forms have been obtained from the shaly part of the forma- 

 tion and these make up a fauna considerably different from that found 

 in the "Spring Creek" limestone. It is the "Spring Creek" limestone 

 fauna which is represented in the cherts and impure limestone below, 

 and in view of these facts it is proposed, to restrict the name Moore- 

 field to the shale beds of which the formation mainly consists and to 

 unite the "Spring Creek" limestone with the underlying formation 

 which it resembles faunally and lithologically. 



The second question considered is whether the cherty beds contain- 

 ing the "Spring Creek" limestone fauna are really Boone or some 

 younger formation. It is true that their fauna and lithology are dis- 



