748 T. C. BROWN — OOLITES AND OOLITIC TEXTURE 



a minute sphere — a spherical concretion; and the aggregation of these con- 

 cretions makes the oolite. The grains are usually much smaller than the Toe 

 of most fishes." . . . 



Further on he says :^ 



"Oolitic beds appear to be confined to the superficial formations of a reef, 

 that is, to the beach and wind-drift accumulations. No example has come 

 imder the notice of the author of oolite constituting the foundation rock of a 

 reef or island." 



After these observations by Dana little attention was given to the sub- 

 ject by Americans until Wieland made known the abundance of siliceous 

 oolites in the vicinity of State College, Pennsylvania. Several papers 

 appeared describing these, and they will receive due consideration in 

 connection with the discussion of siliceous oolites later. 



In 1896 Hopkins prepared an extensive report on the oolitic lime- 

 stones of Indiana, to which he added a chapter on the subject of "Oolites 

 and oolitic limestone in general.'^ ^ The failure of the early American 

 geologists to take notice of these structures, or, at least, to give promi- 

 nence to their records if they made them, is clearly indicated by the fol- 

 lowing extracts from Hopkins' paper : 



"The Americans have very little on the subject, as it (oolite) is not a wide- 

 spread formation in this country, and regions where it does occur have not 

 been studied very thoroughly" (loc. cit., page 397). 



"The principal deposits of calcareous oolites in the United States are in the 

 Lower Carboniferous limestones in the Mississippi Valley. So far as known 

 to the writer, none of any note occur in this country in any other formation" 

 (ibid., page 403). 



During the last two decades more attention has been given to oolitic 

 rocks, and their occurrence has been recorded in many places and at 

 various horizons. It is now recognized that oolites form a considerable 

 part of the Upper Cambrian and Lower Ordovician limestones wherever 

 they occur in this country, and that they are characteristic of this hori- 

 zon in other countries as well.^ 



The majority of the investigations on the origin and formation of 

 oolites have been carried on in (jermany and England. As early as 1888 

 Nicholson (loc. cit.), while working with thin sections of oolitic rock 

 from the vicinity of Girvan, Scotland, discovered concentric wormlike 



«Ibid., p. 156. 



' Indiana Dept. of Geology and Natural Resources, 21st Ann. Rept, pp. 397-412. 

 8 E. Blackwelder : China. Carnegie Institution of Washington, Pul). 54, vol. 1, 1907, 

 pp. 378-383. 



Nicholson: Scotland. Geol. Mag., Dec. iii, vol. v, 1888, pp. 22-24. 



