OUACHITA ORDOVICIAN AREA, ARKANSAS 557 



is spoken of in the geological reports of Arkansas as the Ouachita anticline. 

 On either limb of the anticline the structure is exceedingly complicated, con- 

 sisting of minor symmetrical anticlines, and overturned, closely compressed 

 anticlines and synclines. Thrust faulting is common, parallel with the folds. 

 Scarcely two of the ridges have the same structure, and that of any ridge is 

 liable to change within short distances. 



The rocks of the area are sandstone, shale, some limestone, chert, and 

 novaculite. At least eight different formations are recognized. These are here 

 tentatively named, beginning with the lowest, Collier shale, Crystal Mountain 

 sandstone, Caddo shale. Big Fork chert. Polk Creek shale, Blaylock sandstone, 

 Slatington shale, and Missouri Mountain formation (novaculite, sandstone, and 

 shale). 



The rocks of the area have been determined by the geological survey of 

 Arkansas as of Ordivician age, from the graptolites that occur profusely at 

 two horizons. There is apparently a marked unconformity at the top of the 

 Blaylock sandstone. As the graptolite horizons noted by the present writer are 

 below this, the possibility of the Slatington shale and the Missouri formation 

 being of Silurian age presents itself. These formations have so far proved 

 unproductive of fossils. 



This paper was discussed by A. C. Lane and G. K. Gilbert. 



Soon after 5 o'clock the Society adjourned, and at 7.30 met again in 

 tlie dining-room of the Hotel Alvarado for its annual dinner, which was 

 enjoyed by thirty-seven persons, including a few of the prominent edu- 

 cators of the territory. 



Session of Tuesday, December 31, 1907. 



The Society convened at 9.10 a. m., with President Van Hise in the 

 chair. The report of a committee favoring the establishment of a series 

 of stations for the study' of volcanic and seismic phenomena was adopted. 

 The consideration of an overture on the formation of a Committee on 

 Geological JSTomenclature was deferred to the end of the session. The 

 report of the Council was accepted and ordered printed in the Proceed- 

 ings, and the auditing committee was continued and given leave to report 

 to the Council after the adjournment of the Society. Tlie Society tlien 

 proceeded witli the reading of papers, the first two being presented to- 

 gether by Professor J. E. Wolff. They were 



NOTES ON THE CRAZY MOUNTAINS, MONTANA 

 BY JOHN E. WOLFF 



[A6s/roc<] 



The Crazy mountains were visited by the author in 1883 and 1889, and a 

 paper on their geology was published in the Proceedings in 1892. Last sum- 



