the Horton-Windsor District, N. S. 167 



Gypsum, anhydrite, and red shale. 

 Bj. Maxner^ limestone 80' 



Gypsum, anhj^drite, and red shale. 

 A. Basal limestone, conglomerate, and quartzite. 



Environmental factors. — As interbedded chemical de- 

 posits and red argillaceous shales form so prominent a 

 feature throughout the Windsor series, it is evident that 

 the biotic conditions were decidedly abnormal, a funda- 

 mental fact that must be borne in mind in comparative 

 studies with other faunas. The most significant factors 

 of the Windsor seas were shallow waters, probable high 

 temperatures, and varying salinities, culminating at in- 

 tervals in conditions intolerable to a bottom life. These 

 unfavorable conditions were not confined to local pools, 

 but were of widespread extent in the Windsor basin. 



The shallow-water conditions that prevailed were 

 doubtless maintained by progressive subsidence in a 

 manner analogous to the previous differential movements 

 that controlled the terrestrial deposition in the basin. A 

 ''barrier" of some sort certainly existed against free 

 communication with the outer sea, and it was more prob- 

 ably a tectonic upwarp due to the same differential move- 

 ments than a depositional sand or gravel bar or a current 

 barrier established by differential salinites or by con- 

 trolling winds alone. The Windsor sea, moreover, was of 

 a geosynclinal Paleozoic type and not a shelf sea in the 

 nature of the present Rami of Cutch. There is, further- 

 more, no evidence at hand for complete isolation, and the 

 ''breaks'' in the sequence are in the nature of diastems or 

 minor disconformities. Stages of extreme shallowness 

 took place in the middle of the epoch, as attested by dolo- 

 mitic sands, algal bands, oolites, Modiola bands, etc., 

 which beds are characterized by peculiarly restricted 

 faunules, whilst the nearest approach to normal marine 

 conditions was reached in the late life of the sea. 



Desiccation rarely proceeded beyond the precipitation 

 of gypsum or anhydrite, but this alone would demand, 

 since there were no marked volume contractions, a sur- 

 face inflow from the outer sea of four to nine times the 

 volume of water in the basin under conditions in which 

 the evaporation would approximately balance the acces- 

 sions. 



The times of gypsum or anhydrite deposition were not 

 the only ones that prohibited the establishment of an 



