SILUEIAN. 259 



M 20. ANTICOSTI ISLAND. 



The Ordovician-Silurian sequence is unusually complete in the island of Anti- 

 costi, there being no apparent interruption of sedimentation nor any abrupt change 

 of faunas in the passage from one system to the other. Logan ^**™ gives a detailed 

 section, which is presented below in condensed form, lists of fossils being omitted. 



The strata of this [Hudson River] formation occupy nearly the whole of the north side 

 of the island [Anticosti] and extend from Fox Point, which is toward the east end, to Junction 

 Chff, on the south side, about 4 niiles from the west end. The remaining portion of the island 

 is occupied by newer rocks, to which the name of the Anticosti group has been given. Their 

 position in the geological series is that occupied by the Oneida conglomerate, the Madison 

 sandstone, the Clinton group, and the Niagara group of the New York geologists, but these 

 subdivisions, although apparent in the western basin, disappear in the Anticosti strata, which 

 are litholqgically unlike their equivalents in western Canada. * * * 



The rocks of this group on the island of Anticosti may be considered in four divisions, 

 * * * in immediate succession to the Hudson River formation, as follows, in ascending 



order : 



1. 



Ft. in. 



1 to 3. Greenish " argillo-arenaceous shale at base of yellowish-gray compact argillaceous 

 limestone interstratified with light reddish-gray limestone beds of from 1 to 3 inches 

 thick, with many fossils, all together , 32 6 



4. Measures partly concealed but supposed to be of the same character as the preceding, both 



lithologically and paleontologically 25 



5 to 7. Ash-gray argillaceous limestone, in beds from 1 to 3 inches thick, alternating with 

 beds of calcareo-argillaceous shale of from 5 to 7 inches. Both of these are interstratified 

 with light-gray pure limestone beds, 1 or 2 inches thick 67 



8. Measures concealed 21 



9 to 10. Gray limestone, interstratified with gray and sometimes greenish calcareo-argilla- 

 ceous shale 17 



11 . Yellowish-white coralline limestone 5 



12 to 14. Gray compact argillo-calcareous beds, slightly bituminous, interstratified with 



argillaceous bands 139 



306 6 



2. = 



1 to 2. Ash-gray and light reddish-gray limestones, in beds of from 2 to 6 inches thick, inter- 

 stratified in the upper part with conglomerate beds of some thickness, at intervals of 

 from 2 to 10 feet. The pebbles are calcareous, from 1 to 3 inches in diameter, and lie 

 flat in the beds 120 6 



3 to 5. Reddish-gray limestone, in beds from one-quarter of an inch to 3 inches thick, so.tie 

 of which weather to a reddish brown; interstratified with occasional 'conglomerate 

 layers of from 2 to 4 inches thick (toward the top) 143 6 



6. Measures concealed 40 



7. Gray, yellowish-weathering limestone, containing but few fossils 34 



8. Measures concealed 17 



9. Ash-gray, smoke-gray, ?,nd reddish gray, slightly bituminous limestones 65 



10. Measures concealed 27 



447 



1. Measures concealed 27 



2. Greenish-gray and brown fine arenaceo-argillaceous shales, interstratified with one another, 



in thin beds; no fossils are seen 60 



3 to 7. Ash-gray and light-drab limestones interstratified, both slightly bituminous and 



crowded with Stricklanida lirata (near the top) 157 9 



8. Measures concealed, with 1 foot of light-drab argillaceous, slightly bituminous limestone 



in the middle 51 



9. Light-drab argillaceous limestone, slightly bituminous, in beds of from half an inch to 3 



inches 87 6 



10. Measures concealed at the bight of the cove, north of Southwest Point 157 6 



540 9 



