PETROLOGICAL ABSTRACTS AND REVIEWS 171 



also are given. Besides detailed descriptions of the various rocks, there 

 is a good discussion of movement in solidified rock, illustrated by numer- 

 ous diagrams. 



Barrell, Joseph. ''Relations of Subjacent Igneous Invasion to 

 Regional Metamorphism," Amer. Jour. Sci., I (192 1), 1-19, 

 174-86, 255-67. 



This paper, written by the late Professor Barrell in 1913 or 1914, 

 has been edited and seen through the press by Frank F. Grout, and no 

 better abstract of it can be given than Mr. Grout's own summary. 



Evidence is presented that batholithic invasions widen downward and may 

 occur close below many rocks where they have not been suspected. Batholiths 

 like those in the American Cordillera seem to come to place without crustal 

 compression, but those of the Archean shield and those of the later Appalachian 

 invasions are accompanied by compression. A detailed study of three or 

 four regions shows the metamorphism to be related to the igneous invasion 

 more than to the depth and pressure. One of the regions of deepest burial 

 and close folding in Pennsylvania shows slight metamorphism. 



The action of magmas, both by heating and metasomatism, is reviewed. 

 The solutions are not meteoric in origin. The results in minerals depend on 

 equilibria — largely on the presence of H2O and CO2. The depth of 

 anamorphism may be smaU, due (i) to weakness of some rocks, (2) to invasion 

 of batholiths. An argument for shallow depth is based on the completeness 

 of Archean metamorphism and the salt of the ocean as a measure of erosian. 



The features of metamorphic rocks are reviewed and interpreted as due to 

 one or another factor. Major factors are batholithic invasion and compression. 

 Movements of solutions, selective crystallization, lit-par-lit injection gneisses, 

 and the alternation of injection and mashing, each leaves its marks. 



Bartrum, J. A. "The Conglomerate at Albany, Lucas Creek, 

 Waitemata Harbour," Trans. New Zealand Institute, LII 

 (1920), 422-30. Pis. 2. 



The conglomerates of the Albany Riverhead district (probably of 

 Upper Miocene age) contain pebbles of greywacke, argillite, granodiorite, 

 quartz-diorite, diorite-gneiss, diorite, anorthosite, dolerite, andesite, 

 trachyte, and rhyolite. In this paper the igneous rocks are briefly 

 described and four photomicrographs are given. It is suggested that 

 the gneissic rocks in conglomerates, here and elsewhere in the North 

 Island, perhaps furnish evidence of a terrain injected by batholitic 

 intrusions, subjected to compressional stresses, and eroded before the 

 deposition of the main mid-Mesozoic sedimentaries. 



