GEOLOGY OF SARATOGA SPRINGS AND VICINITY 39 



while the Little Falls dolomite at Saratoga has about the same thick- 

 ness as it has to the west and north. Miller has already made a 

 similar suggestion.^ 



The Hoyt limestone is composed of alternating beds of dolomite 

 and of limestone, and is comparatively thick bedded. The color 

 is usually dark and often black. Several beds of black oolite occur, 

 chiefly in the lower portion of the formation. Many of the lime- 

 stone beds furnish abundant fossils, chiefly trilobites in very frag- 

 mentary condition. Along with these are small gastropods, which 

 are much less abundant. Lingulella acuminata occurs 

 everywhere. Perhaps the most striking fossils of the formation are 

 the big, reeflike masses of the organism of unknown nature, known 

 as Cryptozoon. The genus was originally described by Hall from the 

 exposures by the roadside just north of the Hoyt quarry (plates 

 3 and 4), where a bared and glaciated surface of the rock is 

 splendidly exposed over a considerable area. Reefs and masses 

 of more than one species of this genus are of common occurrence 

 in both the Hoyt limestone and the overlying Little Falls dolomite, 

 in the latter ranging throughout the Mohawk and Champlain val- 

 leys. The reeflike nature of the masses is well shown in many 

 places in the district, notably so perhaps in the railroad cut just 

 east of Greenfield depot. Midway of this cut is shown a Crypto- 

 zoon reef of massive limestone (6 feet thick). Toward the west 

 this bed breaks up into thinner bedded material which at the same 

 time becomes very sandy and with layers of nearly pure quartz 

 sand, while to the east it remains pure limestone, though the Cryp- 

 tozoon gives out. The east is taken to be the seaward and the 

 west the landward side of the old reef. 



The Hoyt limestone is well shown in the so-called railroad 

 quarry, i mile north of Saratoga (plates 5 and 6). But neither 

 base nor summit shows there and the outcrop is an isolated one 

 lying between two branches of a fault, so that it tells nothing what- 

 ever in regard to the stratigraphic relations of the formation. It 

 has a local high dip to the southwest due to proximity to a fault, 

 shows a thickness of some 20 feet of the formation including a 

 splendid Cryptozoon reef, and is an excellent locality for fossils. 

 But for the stratigraphy we must go to the exposures in the railroad 

 cuts and the vicinity of the Hoyt quarry. Here an excellent section 

 of the greater part of the formation is obtained, overlying the 

 Theresa formation, hence making certain its stratigraphic position. 

 The summit, however, is not seen, though if we are correct in 



1 N. Y. State Mus. Bui. 153, p. 30. 



