Yol. 57.] PHYSICAL DEVELOPMENT OP eTJADELOFPE. 509 



conglomerates above Basse Terre, is undetermined. Tliey cannot 

 be correlated with the submarine tuffs observed in the south- 

 eastern part of the island, nor is it known whether they are older 

 or newer. They may be contemporary with other kinds of 

 Tertiary accumulations in Grande Terre. However, the observations 

 show the great age of the underlying eruptive rocks, which are 

 evidently as old as the igneous basement of Antigua, or of p re- 

 Tertiary age. Such igneous and igneo-mechanical formations 

 have been more fully studied in Dominica. 



As the old eruptives underlie the tuffs near Trois Rivieres, the 

 apparent representatives of which were long ago described by 

 Moreau de Jonnes and Duchassaing as underlying the limestones of 

 Grande Terre, there is little reason to doubt their extension under 

 the whole island, or even under the archipelago. 



The outwardly-sloping terraces, observed in places up to a 

 considerable elevation, are simply the massive beds of tuff, giving 

 rise to cliffs, 100 feet high, which have been deformed owing to 

 the elevation of the mountain-mass due to volcanic forces. These 

 have not affected the strata or configuration of Grande Terre. The 

 late volcanic phenomena have not been studied by me, but eruptions 

 were recorded at several dates in the eighteenth and nineteenth 

 centuries.^ 



lY. The Eaelier Tertiaky FoPvMAtions in Grande Terre. 



The lowest beds in Grande Terre are seen in only a few localities 

 at low elevations, beneath the overlying limestones east of Salt 

 River. They are composed of yellow tuff, surmounted by 75 or 

 80 feet of volcanic sand redeposited by the sea, as described by 

 Moreau de Jonnes and Duchassaing. In the lower beds those 

 observers found only a few fossils, but in the upper layers Duchassaing 

 obtained Ai'ca umbonata, Pectunculus indvinatiis, Lam., Cyatliina 

 guadalupensis^ and other organisms. The Pectunculus is an European 

 Eocene type, and Cyathina may be placed along with the corals 

 of Antigua, thus suggesting the early Tertiary age of the strata. 

 Conformably with these beds, and underlying most of the surface of 

 Grande Terre, there is a calcareous formation consisting of beds of 

 white or creamy limestone and marl, with the surface some- 

 times weathered to drab. Some of the beds are fine-grained, compact, 

 and hard, others are earthy and marly. In places they contain fossils, 

 mostly in the form of casts. The rocks of more compact texture 

 often abound in cavities. The strata are nearly horizontal, but dip 

 north-eastward. These beds include the roches a ravets and 

 part of the white marls or foraminiferal limestones of Duchassaing.^ 



^ In 1778, 1796, 1797, 1836, 1837, & 1846. 



2 Duchassaing classified the formations of Grande Terre as follows: — 



Is ewer Pliocene : Alluvium and detrital formations,' the Madreporic, and 



the Galibis or Antbropolite. 

 Older Pliocene : Clays ; and white marl or foraminiferal limestone. 

 Miocene : Eoches a ravets, volcanic sands, redeposited by the sea, and 

 yellowish tuffs. See Bull. Soc. Geol. France, ser. 2, vol. iv (1847) 

 pp. 1094-95, 



