Y. The Taconic of Georgia and the Report on the Geology of Vermont. 



By Jules Marcou. 



(Read May 4, 1887.) 

 CONTENTS. 



I. Introduction p. 105 bomg near Quebec. Landslides at Montmo- 



II. Sections aronnd Parker quarry at Georgia. rcncy and Indian Lorette Fails . p. 116 



The Lorraine shales versus tlie Hudson River V. The Report on tlie Geology of Vermont. The 



group. The sui)pressed Etuuions' Agricul- classification and nomenclature of Messrs. E. 



tural and geological map of the state of New and C. H. Hitchcock ... p. 119 



York. Colony .... p. 107 VI. Historic cl.assification and use of tiie name 



III. Age of the red sandrock, and section near Georgia, with some paleontological remarks 



S wanton p. 114 and some notes on the Graptolites zones of 



IV. The supposed overlying great fault of the America ..... p. 122 



Georgia formation. The section at Charle- 



I. Introduction. 



_l HE geology of the eastern region of Lake Champlain and of the whole band of coun- 

 try extending from Albany and Ponghkeepsie on the Hndson River, varying in breadth 

 from ten to forty miles eastward and extending north to Quebec, Trois Pistoles and 

 Cape Gaspe, is, by far, the most difS.cnlt and complicated that I have met with dnring my 

 forty years' researches in both hemispheres. JSTothing, even in the central Alps, is so 

 puzzling and intricate. 



The slates predominate as a general fact, but there are enclosed among them lentic- 

 ular masses of ordinary limestone, marble, magnesian limestone, calcareous sandstone 

 and pure sandstone, varying in size from that of the fist to small islands or even mountains 

 2000 feet long and 1000 feet broad. At first sight the slates are too uniform to permit 

 of establishing stratigraphic divisions and easily recognized groups; and the lenticular 

 masses of limestone and sandstone appear so suddenly from place to place, with such 

 capricious distribution, that instead of being a help in the classification, they are, on the 

 contrary, a constant cause of error and considerably increase the difficulties. 



The sections are rarely very clear, and require more than ordinary caution in their 

 surveys and interpretations. Paleontology must be used with a large margin for anom- 

 alies. Singular apparitions of forms, which otherwise are trusted as sure indications of 

 certain groups of strata, are very likely to mislead, if not taken carefully with all the 

 surrounding circumstances attending their j^osition in the rocks. It is more difficult to ar- 

 rive at the truth about fossils from some parts of the Taconic system than from any other 

 system of rocks in the scale of geological formations. Even the colonies of Bohemia, 

 first discovered and described by Barrande, in the second fauna (Cainl)rian) of fossils of 

 the third fauna (Silurian), seem easier to work out and to accept. We must be contented 



MEMOIRS BOSTON 30C. NAT. III8T., VOL. IV. IG (105) 



