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Full text of "Synopsis of the geology of Montreal"




Ami, Henry -fere 

Syrv geology 

of Montrc. 



GcoV 

A 



EX. BRITISH MEDICAL ASSOCIATION OFFICIAL GUIDE 
AND SOUVENIR, PP. 45-49, MONTREAL, 1897. 




SYNOPSIS 



OF THE 



GEOLOGY OF MONTREAL 



By H. M. AMI, M.A., D.Sc. 

FELLOW OF THE GEOLOGICAL SOCIETIES OF LONDON, 
SWITZERLAND AND AMERICA 



AUTHOR'S EDITION 

DEC. 1897. 



PRINTED 15 Y 

THE CANADA ENGRAVING & LITHOGRAPHING CO., 
MONTREAL. 



THE GEOLOGY OF MONTREAL. 



Fourteen distinct geological formations or hori- 
zons have been described within a radius of a 
few miles from Montreal. Four of these belong to 
the Quaternary or newest system, one is doubtfully 
but probably referable to the Devonian, one to 
the Silurian (Upper Silurian of Murchison), seven 
to the. Ordovician (Lower Silurian and Cambro- 
Silurian of many authors), and the remainder to 
the Laurentian or part of the great Archaean 
Complex. 

A geological map of Montreal and its environs 
would comprise four areas marked by four distinct 
orographic features worthy of note, as follows : 

(1) A more or less hilly and mountainous pla- 
teau of Archaean rocks to the north and north-west 
of Montreal. 

(2) A broad, flat, more or less elevated Ordovi- 
cian plain. 

(3) A number of conspicuous, more or less 
elevated conical mountains or hills of volcanic ori- 
gin rising through the Ordovician plain. 

(4) Alluvium, marine clays and sands, gravel 
terraces and raised beaches accompanied by "till" 
and numerous phenomena characteristic of the 
" Great Ice Age." 



2 Jh'itis/i Medical Association 

SUMMARY OF THE; VARIOUS GEOLOGICAL FORMATIONS IN 
AND AROUND MONTREAL, CANADA, AND SOMF, OF 
THKIR MORK SALIENT CHARACTERS. 

PLEISTOCENE. 

Exclusive of the fresh-water, lake and river 
deposits of more recent times, the Pleistocene forma- 
tions, in descending order, consist of the following : 

I. SAXICAVA SAND FORMATION, of Eastern 
Canada. Characteristic fossils : Saxicava rngosa, 
My a arenaria, M. t run cat a, Maconia fragilis. 

II. LEDA CLAY FORMATION, marine clays with 
occasional sandy partings ; foram in i feral. Fossils : 
Leda (Portlandia] arctica, CranieUa Logani, Ophio- 
glypha Sarsii, Polystoniella crispa, etc. 

III. GLACIAL OR BOULDER CLAYS, TILL. No 
fossil remains have as yet been found in the glacial 
clays of Montreal. 

Localities : St. L,ouis and Mile-End Quarries, the 
Tanneries, etc., are excellent collecting grounds for 
Pleistocene fossils. 

DEVONIAN. 

DEVONIAN ERUPTIVES, ETC. To the Devonian 
Epoch are ascribed those nepheline syenite masses, 
diabase, and trachyte, and other dyke rocks, which 
are so conspicuous and numerous about Montreal, 
holding Dawsonite, sodalite, elseolite-syenite, etc. 
The eruptive masses comprise Mount Royal, Beloeil, 
Montarville, Rougemont, Mount Johnson, etc. 

An occasional pebble of fossiliferous Middle 
Devonian limestone marks the probable existence, at 
one time, of a basin of Devonian rocks in the Mont- 
real district, similar to those which are known 
to exist farther east along the Famine River, and in 



Souvenir of Montreal, 1897 3 

the Gaspe Peninsula of Quebec, or to the south 
in the Helderberg mountains of New York State. 
Such Devonian pebbles occur in the volcanic ag- 
glomerates or breccias of St. Helen's Island, just 
south of Montreal. 

SILURIAN. 

LOWER HELDERBERG FORMATION. Consists of 
somewhat limited patches of light gray and compact 
more or less altered limestones which abound in 
fossil remains, chiefly Brachiopoda. Fossils : Fa- 
Tosites Gothlandicus, Leptcena rhoinboidalis, Orthis 
cm in ens, StropJieodonta varistriata, S- punctulifera, 
Pentamerus galeatus, Spirifer concinnus, S. cyclop- 
terns, Atrypa rcticularis, Stenoschisma formosum, 
Platyustoma depressum. Locality : South side of 
St. Helen's Island. 

ORDOVICIAN. 

The Ordovician (Cambro-Silurian and Lower 
Silurian) formations in the Montreal district are 
seven in number, and from the Lorraine or upper- 
most Ordovician in Canada, down to the Potsdam 
sandstone there is not a single break in the suc- 
cession. From Ste. Anne, a point twenty miles 
west of Montreal, to Chambly, there is a complete 
section and series of these seven formations in 
descending order as follows : 

I. LORRAINE ("Hudson River" of many geol- 
ogists). Consists of dark brown and black, brittle, 
for the most part indurated clay and arenaceous 
shales and sandstones. Fossils : Columnar ia alveo- 
lata, Catazyga Headi, Pteriuca demissa, Byssonychia 
radiata, Orthograptus quadritnucronatus, Clidophorus 
pianulatus, Orthodesma parallel-urn, Cyrtolites orua- 
ttis. Localities : Chambly, Rougemont, Riviere- 
des-Hurons, Belceil. 



4 British Medical Association 

II. UTICA FORMATION. Dark brown and black, 
brittle and bituminous shales with occasional bands 
of limestone at the base'. Fossils : Reteograptus (?) 
eucharis, Leptograptus flaccidus, Lcptobolus insignis, 
Scliizocrania filosa* Cornulitcs iuiniaturum, TrocJio- 
lites animonius, Triarthrus Bccki. localities : St. 
Helen's Island, West End, Point St. Charles, near 
Victoria Bridge. 

III. TRENTON FORMATION. Dark gray fossili- 
ferous limestone and shales. Fossils : Glyptocystitcs 
Logani, Hcterocrinus tennis, Pachydictya acuta, Plcc- 
tainbonitcs sericca, Prasopora Sclwyni, Dalmanc.lla 
tcstudinaria, Parastropliia Jiemiplicata, Rajincsqiiina 
altcrnata, Treuiatis Montrealensis, T. tci'ininalis, 
Glossina riciniforviis, RJiynchotreina iricegu wall/is, 
Cyclonema Montrcaleusc, Bellerophon bilobatus, Conu- 
laria Trcntonensis, Trochonema umbilicatum, Isotelus 
gigas, Calyincna scnaria, Localities : Mile-End and 
St. Louis quarries, Lachine, Pointe-aux-Trembles, 
Hochelaga. 

IV. BIRD'S EYE AND BLACK RIVER FORMA- 
TION. Dark gray impure fossiliferous limestones. 
Blocks of this limestone were used in construct- 
ing the piers of the Victoria Tubular Bridge. 
Fossils : Tetradium fibratuin, Coluinnaria Halli, 
Solenopora compact a, Stromatocerium rugoswn, He- 
licotoma planulata, Cyrtodonta Hnronensis, Bathy- 
urus extans. ' Localities : Pointe- Claire, St. Vin- 
cent-de-Paul. 

V. CHAZY FORMATION. Light and dark gray 
fossiliferous limestones. Fossils : Bolboporites Ame- 
ricamis, Malocystites Murchisoni, Blastoidocrinus car- 
charicedens, Rhynchotrema plena, Lingula Belli, 
Orthis, (Hebertelhi) borealis, O. imperator, Bathynnis 
Angelini. Localities : Sault - au - Recollet, Back 
Mountain, St. Martin, Terrebonne, Caughnawaga. 
Excellent building stone. 



Souvenir of Montreal, 1897 5 

VI. CALCIFEROUS FORMATION. Dark gray, im- 
pure, more or less magnesian and arenaceous, fossil- 
iferous limestone. Fossils : Pleurotomaria calcifera, 
P. Caimdensis, Orthisina grauda'va, Ophileta com- 
planata, O. disjuncta, Hormotoma Anna, Metoptoma 
simplex, Orthoceras Lamarcki, Ainphion Salteri, 
Batliyurus Cybele, Ribeira calcifera, Leperditia Anna. 
Localities : Ste. Anne, Caughnawaga, Carillon. 

VII. POTSDAM (SANDSTONE) FORMATION. 
Light yellow, rusty-weathering sandstones. Fossil 
remains : Scolithus Canadensis, Protichnites multino- 
tatus, P. lineatus, P. octonotatus, P. septemnotatus. 
Localities : Beauharnois, for tracks ; Ste. Anne, 
for Scolithus. 

ARCH^AN. 

LAURENTIAN. The " Morin area," north of 
Montreal, has been recently described by Dr. Adams, 
and forms a part of that extensive series of granites 
and granitoid gneisses, limestones and anorthosites 
so extinsively developed everywhere in North -East- 
ern Canada, covering as they do an area of more 
than two million square miles. 

For a more detailed account of the geology of 
Montreal and its environs, the reader is referred 
to volume VII of the "Annual Report of the Geo- 
logical Survey of Canada," 1896, in which Dr. Ells, 
Dr. Adams and the writer present the leading geo- 
logical features in the stratigraphy, petrography, 
and palaeontology respectively. The " Geology of 
Canada," 1863, by Sir Win. Logan, E. Billings, 
Sterry Hunt, etc., also contains excellent -details on 
the same district, besides other districts of Ontario 
and Quebec. 



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