34 NEW YORK STATE MUSEUM 



"As it Stands, the faunal evidence indicates almost conclusively 

 that zones 1-3 can not correspond in age to the typical Theresa. 

 The former can scarcely be older than the Gasconade-Chepultepec- 

 Oneota (=Upper Ozarkian), while the latter is surely not younger 

 than early, or early Middle Ozarkian. Apparently zones 1-3 belong 

 to the Little Falls dolomite rather than to the Theresa. If Little 

 Falls — or better, late Ozarkian — overlap took place in the 

 Ogdensburg region, the ensuing sediments would naturally partake 

 of and simulate the sandstone land there prevailing." ^ 



According to this report of Ulrich's, the fossils point to a late 

 Ozarkian (or Upper Cambrian) age, or else to a Canadian (earliest 

 Ordovician) age. But the remainder of the section here definitely 

 affirms the former as the true solution, since these beds are uncon- 

 formably overlaid by beds of Tribes Hill age, the Tribes Hill 

 formation being the oldest known formation of the New York 

 Ordovician. Though we have mapped the beds with the Theresa, 

 the Heuvelton sandstone and the beds over that all belong in this 

 new division, as well as a varying thickness of the underlying beds, 

 from o to 30 feet in thickness. It will probably be wise to extend 

 the name Heuvelton to include the whole. This division occupies 

 the same interval as that occupied by the Little Falls dolomite of 

 the Mohawk valley, but it is as yet premature to say that it should 

 be correlated with that. The Little Falls follows the Theresa 

 without a break, while there seems to be a break between this 

 Heuvelton and the underlying Theresa. 



It is, however, not certain that the Little Falls itself is a single, 

 indivisible formation. The upper, cherty beds at Little Falls and 

 eleswhere contain occasional fossils, especially in the cherts. It 

 was these upper cherts which furnished the fossils described by 

 Hall in volume i of the New York Paleontology. The beds contrast 

 rather sharply with the great mass of unfossiliferous dolomite 

 below, and also with the Tribes Hill above. An unconformity 

 separates them from the Tribes Hill. Ulrich has a suspicion that 

 these cherty beds are separable from the Little Falls proper as an 

 upper division, and that a break may occur between them and 

 the main mass of the Little Falls. He is also disposed to correlate 

 the Heuvelton beds with these upper, cherty beds of the Little 

 Falls, because of similarity in the fossils. We have seen all the 

 sections together and I think that this view of Ulrich's has much 



1 Letter of October 17, 1914. 



