abstracts: petrology 205 



• 



the authors, who have noted their form and prominence, their 

 mutual relations, their positions in the basin, the formations exposed 

 on their axes, and their similarity to like domes and anticlines that 

 carry or do not carry oil or gas. So far as can now be determined 

 from the surface indications, about half of these are considered promis- 

 ing, but the drill, which is the final test, may show that some of them 

 are barren and that others which are now regarded as less promising 

 may be productive. It is highly probable that half or more of the 

 antichnes and domes here described constitute a large part of the most 

 promising undeveloped oil territor}- in Wyoming. The Big Horn Basin 

 seems to be destined to furnish a large contribution to the Nation's 

 supply of high-grade oil. 



R. W. Stone. 



GEOLOGY. — Louisiana clays, including results of tests made in the 

 I'ahoratonj of the Bureau of Standards at Pittsburgh. George 

 Charlton ^Iatson. U. S. Geological Survey Bulletin 660-E. 

 Pp. 12, with maps and sections. 1917. 

 This paper shows the geographic and geologic distribution of Louis- 

 iana claj^s and includes 26 tests made by the Bureau of Standards 

 showing the working and burning behavior. 



R. W. Stone. 



PETROLOGY.— T/ze problem of the anorthosites. N. L. Bowen. 

 Journ. Geol. 25: 209-243. April-May, 1917. 

 Anorthosites are made up almost exclusively of the single mineral 

 plagioclase and in virtue of this fact they present a very special prob- 

 lem in petrogenesis. The conception of the mutual solution of minerals 

 of the magma and the lowering of melting temperature consequent 

 thereon is no longer appHcable. Yet anorthosites give no evidence of 

 being abnormal in the matter of the temperature to which they have 

 been raised; in other words, they give no evidence of having been raised 

 to the temperature requisite to melt plagioclase. A possible alternative 

 is that they may never have been molten as such and are formed simply 

 by the collection of crystals from a complex melt, probably gabbroic 

 magma. This possibihty is in harmony with the expectations that 

 grow out of experimental studies and for this reason a consideration of 

 the hkehhood that anorthosites have originated in the stated manner 

 becomes imperative. 



