•  
  •  
 

Abstract

The name Arkansas Novaculite was proposed by A.H. Purdue, 1909 to replace the name Arkansas Stone assigned by L. S. Griswold, 1892, but deemed too generic, to an interval of Early Devonian-Early Mississippian, very fine-grained, even textured, siliceous sedimentary rock famous for use as whetstones. The interval is exposed along the margins of the Benton Uplift, south flank of the Ouachita Mountains, west-central Arkansas, where it reaches a maximum thickness of 243.8 m (800 ft). The Arkansas Novaculite comprises informal lower and upper members characterized by massive beds of nearly pure novaculite, separated by a shale-bearing middle member that spans the Devonian-Mississippian boundary. The formation represents deep water deposition below carbonate compensation depths, in contrast to contemporaneous chert-bearing intervals, such as the Early Mississippian Boone Formation in the southern Ozarks, with chert formed in shallower marine conditions, or as a replacement of associated limestone beds. Source of the prodigious quantities of silica forming the Arkansas Novaculite has been controversial. Geochemical analyses, using both EDX and trace element analysis, were performed using mass spectrometry and have identified a significant contribution by both aluminum and potassium, which would seem to eliminate a biogenic origin and favor a volcanic source, perhaps related to an island arc system that formed during the Ouachita Orogeny as Laurasia collided with Gondwana. Trace element analysis also suggests that the Arkansas Novaculite and the chert in the Boone Formation may have both been formed from the same volcanic source.

Download

Share

COinS