WORK OF JOSEPH BARRELL ON SEDIMENTATION 4] 



in his "Central Connecticut in the geologic past." ^^ His opinion was 

 that the sediments were deposited from the waters of migrating rivers 

 and shifting lakes, and that the sediments of the wide river floodplains 

 w^ere subjected to periodic drying. The climate was inferred to be of 

 semi-arid character. 



Another group of formations that engaged Barrell's attention was that 

 known as the Old Red Sandstone in the British Isles, and his last impor- 

 tant paper on the interpretation of geological formations was entitled 

 "Dominantly fluviatile origin under seasonal rainfall of the Old Red 

 Sandstone." ^^ 



The conclusions reached in this study are stated as follows : 



"The central conclusion reached in this paper is that the Old Red Sandstone 

 formations were not deposited in lakes or estuaries, nor are they of desert 

 origin. The analysis of their characteristics and comparison with sediments 

 now forming determine them to be river deposits accumulated in inter- 

 montane basins. This is a kind of sedimentation not now found in the British 

 Isles. For a close analogy one may turn to the basin deposits of the western 

 United States laid down in the Tertiary period between the growing ranges of 

 the Cordillera. This reinterpretation of the Old Red Sandstone of the British 

 Isles is in line with that which has gone forward in America during the past 

 fifteen years in regard to the origin of the continental Tertiary deposits : once 

 looked on as deposited in lakes greater in area than any now existing on the 

 earth, they are now regarded as accumulations made chiefly on river plains. 

 Such a reinterpretation for the Old Red Sandstone involves radical changes 

 in the conception of Devonian geography — no less a change than the substitu- 

 tion of land surfaces, occasionally flooded, as a replacement in the mental 

 vision of wide and permanent bodies of water. If the new interpretation is 

 well founded, it means that such terms as 'Lake Caledonia' and 'Lake Orcadie" 

 should be turned into 'Caledonian and Orcadian basins.' " ^^ 



Rhythms and the Measurements of geologic Time 



The title of this section of this review is that of the one of Barrell's 

 papers^'^ in which he probably attained his greatest height as thinker on 

 fundamental geological problems. A part of it was presented under the 

 title "The significance of sedimentary rhythms," as one of a series of 

 papers composing a "Symposium on the interpretation of sedimentary 

 rocks," at the meeting of the Geological Society of America in Albany, 

 New York, December 29, 1916. It is not practicable to give in this place 

 even an adequate review of this remarkable memoir ; a few comments and 



^* Connecticut State Geological and Natural History Survey, Bull. 23, 1915, pp. 28-32. 



35 Bull. Geol. Soc. Am., vol. 27, 1916, pp. 345-386. 



36 Op. cit., pp. 348, 349. 



3' Bull. Geol. Soc. Am., vol. 28, 1917, pp. 745-904. pis. 43-46. 



