ON OOLITES AND SPHERULITES 609 
preted as incrusted gas bubbles secondarily filled with calcite 
(“ent-odlites’’).7 ; 
In other cases the substance of the odlitic grains has been com- 
pletely changed, in some even before final deposition, in others dur- 
ing the diagenesis of the sediment, or still later through metasomatic 
or katamorphic processes, as in the dolomitic odlites,? some siliceous 
odlites,3 and the great variety of odlitic iron ores, the interpretation 
of which, in most instances, is still far from being satisfactory. 
1 C. W. v. Giimbel, NV. Jahrb. fiir Min., etc., 1873, p. 302. The incrustation of air 
bubbles by calcium carbonate was observed by Knop in the hot springs at Nauheim. 
Cf. ibid., 1874, p. 285. 
2 Cf., for instance, W. H. Sherzer and A. W. Grabau, ‘‘The Monroe Formation 
oi Southern Michigan and Adjoining Regions,”’ Mich. Geol. and Biol. Surv., Publ. 2, 
IQ10, pp. 35-37; LT. C. Brown, ‘Origin of Odlites and the Odlitic Texture in Rocks,”’ 
Bull. Geol. Soc. America, XXV (1914), 759. For European occurrences see the text- 
books of Zirkel (Petrography), Tschermak, etc. 
3 Cf., for instance, the siliceous odlites of Pennsylvania, in Brown, of. cit., pp. 
y pp 
=60-68. See 1¢é ff. on Zo A. i 
