UNIVERSITY OF CALIFORNIA PUBLICATIONS 



BULLETIN OF THE DEPARTMENT OF 



GEOLOGY 



Vol. 7, No. 15, pp. 325-334 Issued June 12, 1913 



THE PETROGRAPIIIC DESIGNATION OF 

 ALLUVIAL FAN FORMATIONS 



BY 



ANDREW C. LAWSON 



CONTENTS 



PAGE 



Use of the Term Breccia 325 



Alluvial Fans are Formations of Vast Extent 326 



Use of the Term Conglomerate 327 



Ancient Alluvial Fan at Battle Mountain. Nevada 328 



Term Fanglomerate Proposed 329 



Limitations of the Term 330 



Varieties of Fanglomerate 331 



Geological Significance of the Battle Mountain Fanglomerate 332 



Scarcity of Fanglomerate among the Rocks of the Past 333 



Use of the Term 'Breccia.' — The following quotations refer- 

 ring to the significance of the word "breccia" are taken from 

 the current edition of a well-known American text-book of 

 geology : 



"Volcanic agglomerate, or breccia, is a mass of angular blocks of lava, 

 with which may be mingled fragments of sedimentary rocks, which the 

 volcano has torn from the sides of its chimney. . . . Ordinarily the breccia 

 is found only near the vent, etc." 



"Breccia is a rock composed of angular fragments cemented by 

 deposition of material, commonly CaC0 1; in the interstices. The frag- 

 ments may be any kind of rock. Breccia is also found in zones of 

 fracturing and shattering of the rocks along fault-planes and is then 

 called fault-breccia." 



"Coral conglomerate or breccia is a cemented mass of coral pebbles or 

 angular pieces or is made up of fragments of an older coral rock." 



