) 



PROCEEDINGS 



OF THE 



AMERICAN PHILOSOPHICAL SOCIETY 



HELD AT PHILADELPHIA 

 FOR PROMOTING USEFUL KNOWLEDGE 



Vol. Lll April, 1913 No. 209 



THE FLUTING AND PITTING OF GRANITES 

 IN THE TROPICS. 



(plates i-viii.) 



By J. C. BRANNER. 



(Read April 4, 1913.) 



Fluting is a peculiar minor form of topographic relief, but where 

 it occurs over an area large enough to attract attention, it is a very 

 striking feature. 



All geologists are familiar with the fluting of limestones, which is 

 a common phenomenon all the world over. Many fine examples of 

 the fluting of limestones are given in Dr. H. Stille's " Geologische 

 Charakterbilder," 10 Heft, published at Berlin in 1912, in which they 

 are called " Karren." 



But the fluting of granites or of other crystalline rocks is, so far 

 as I have been able to learn, confined to tropical, and possibly sub- 

 tropical countries. Two cases that occur on the coast of the state of 

 Pernambuco in Brazil were mentioned by me in a paper on rock 

 decomposition published in 1896.^ Since that paper was published I 

 have seen in Brazil some very striking examples, and have seen 

 photographs of several others. Good examples are also cited by 

 Max Bauer, who speaks of them as furrows (Rillen).- 



* X- C. Branner, " Decomposition of Rocks in Brazil," Bid. Geol. Soc. 

 Amer., VII., 280, Rochester, 1896. 



^ Neues Jahrbuch f. Mineralogie, 1898, II., 192, and Plate XI. 



P ROC. AMER. PHIL. SOC. LH. 2O9 K, PRINTED JUNE 6, I913. 



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