GEOLOGICAL AREAS OP CANADA. 93 



The rocks within this region consist mainly of Lower or typical 



Laurentian strata, overlaid in some few localities by feldspathic rocks 



of the Upper Laurentian or Labrador series. The Laurentian strata 



proper, are composed essentially of vast beds of micaceous and 



syenitic gneiss, hornblende rock, and q\iartzites, with interstratified 



bands of crystalline limestone and oxidized iron ores. Valuable 



deposits of the latter occur, especially, in the townships of Hull, 



Templeton, and G-renville, on the Ottawa. As a rule, these Lower 



Laurentian strata are more or less strongly tilted, corrugated, or 



otherwise disturbed. They are also very generally traversed by 



granitic or syenitic veins, and are broken through in places (more 



especially in Wentworth, Chatham, and Grenville, on the Lower 



Ottawa) by enormous masses of eruptive syenite and greenstope. 



The crystalline limestones very commonly contain numerous examples 



of diopside, phlogopite, zircon, sphene, and other crystallized silicates ; 



and they are associated in many places with workable amounts of 



graphite and fluo-phosphate of lime, as in the townships of Buckingham, 



Portland, Lochaber, Grenville, &c. The Upper Laurentian or 



Labrador formation is represented principally by thick beds of anor- 



thosite or feldspar rock, with associated feldspatho-pyroxenic beds 



and interstratified gneissoid rocks. Titaniferous iron ore is a frequent 



accompaniment of these higher strata, and in some localities, as at 



Bale St. Paul, it is present in large quantity. Whilst the Lower 



Laurentian strata occur throughout the district generally, the upper 



series has been recognized only in detached areas of comparatively 



limited extent. One of these is seen in the Counties of Argenteuil, 



Terrebonne, Montcalm, and Joliet, in the western part of the district ; 



and others occur in the vicinity of the Montmorenci Falls ; in the 



country about Bale St. Paul and Murray Bay; in the vicinity of 



Lake St. John on the Saguenay ; and on the River Moisie, in the 



east. In addition to these crystalline formations, a few outlying 



patches of Silurian strata, consisting mostly of Trenton limestones 



and Utica shales, occur here and there within the Laurentide area. 



The largest of these Silurian outliers is seen around Lake St. John 



on the Upper Saguenay ; and small exposures occur at one or two 



spots on the sbore of the St. Lawrence, below Quebec, as at the 



Montmorenci Palls, Murray Bay, &c. Glacial boulders, clays, and 



gravels, with Post-Glacial sands and other superficial deposits — among 



■which the titaniferous iron sands of the Lower St. Lawrence may be 



