Maryland Geological Survey 41 



nual Eeport. In the revised rules the stratigraphy and fossils are 

 assigned equal importance M'ith the lithology in the identification of a 

 formation, as may be seen from the last sentence of Eule No. 4, which is 

 as folloM'S : " The formation should be recognized and should be called 

 by the same name as far as it can be traced and identified by means of 

 its lithologic character, its stratigraphic association, and its contained 

 fossils." ' 



The method of naming the sedimentary fomiations and the names for 

 their subdivisions are given and clearly defined as follows in Rules 5 

 and 6 : 



" 5. When, for scientific or economic reasons, it is desirable to recognize 

 and map one or more specially developed parts of a varied formation, 

 such parts shall be called members, if they have considerable geographic 

 extent; or if their distribution is more limited they shall be described 

 in some appropriate term, such as lentil. 



" 6. All sedimentary formations shall receive distinctive designations. 

 The most desirable names are binomial, the first part being geographic 

 and the other lithologic (e. g., Dakota sandstone, Trenton limestone, 

 etc.). The geographic term should be the name of a river, town, or other 

 natural or artificial feature at or near which the formation is typically 

 developed. Names consisting of two words should be avoided. Names 

 taken from natural features are generally preferable, because less change- 

 able than those of towns or political divisions. When the formation 

 consists of beds differing in character, so that no single lithologic term is 

 applicable, the word ' formation ' should be substituted for the lithologic 

 term (c. rj., Eockwood formation). Members and other subdivisions shall 

 be named in the same manner, but in the legend of the map the term 

 ' member,' etc., shall always be added to the geographic and lithologic 

 designation (c. g., in the Pottsville formation, the Homewood sandstone 

 member)." " 



The mapping of the areal geology in the Appalachian part of the 

 Virginias began in 1888 and the first folio, that of Staunton, Virginia, 



* hoc. cit., p. 23. 

 'Ibid., p. 24. 



