GM 15279 GEOLOGY OF THE MEMPHREMAGOG MAP AREA • C 4 / Jç- I f Ministère des Richesses Neureiles, Québec SERVICE DES GITES MIN Aq, No GM—. 77 \V) C CN`.i:ii;i:T`l'S Chapter 1 Introduction. Chapter II General character o. <.:ty District. Chapter III General'Geology. Chapter IV Structural Geology. .Chapter V Historical Geology. Chapter VI Economic. Geolo gy. Plate I T .7:Tassri;~p~±-- Bunker Brook, - i+'itc:! Bay valley the north. Plate Il Parallel valleys, the second is that of the Tomifobia River and the pronounced valley die:;. is that of Bunker. Brook. • Plate III Looking southeast across Fitch Bay. 77i`.ls o 'Stanstead granodiorite in right background. Plate IV Whetstone Island. The low flat area in the fore•-. ground is underlain by Devonian limestone. hills in the background are of Stanstead diorite. Plate V Looking northwest toward Lake Massaw p i. ground shows .type of topography west of Bunker fault . In the background the ridge east of the .fault can be traced.far to right. .Plate VI Drag `'olds south of Ayer' s Cliff in the Tomifobia • interbedded slates and•limestone. Plate VII Biotite segregation in Stanstead granodior?. Plate VIII Biotite streaks. in Stanstead granodiorite. Plate IX Parallel pegmatite veins in Stanstead granodiorite m' • a _- _•- • . ..- .. --L- ~ Plate X Stanstead Granite Company's quarry at Gran i te-U < i le, showing the excellent sheeting and ideal working conditions. Plate XI Serpentine hill. u~ Figure Index map showing the location of the I:emphre- ma.gog area. Figure. 2. Showing location of diorite areas and points from which specimens were collected. Figure 3. Cross-section of fold, trend of fold IT.800i5. Figure 4. Showing areas of Siluro-Devoniean. Figure 5. Shôwing areal extent of Stanstead granodi or:i.te and associated dikes • Figure 6. Graphical representation of the quantitative mineralogical analyses and classification of specimens of the main mass of the Stanstead granodiorite and an average of these. Figure 7. Graphical representation of the quantitative mineralogical analyses and classification cf specimens of the intrusives associated with the main mass. o f the Stanstead granodiori te , Figure 8. Showing location of dikes. Figure 9. Diagram to show some features of the Pleistcca_L. ,and Recent geology. Figure 10. To show some important structural features. Figure 11. Showing location of quarries. G N A PTeR i• 'f .1"lkod uc t on . Purpose The tareaçlyinF soUi heaSt• of the' upper ût.!1a. ' z.s.0 e _ '(as •ocCupied.. the attention . of geolosiCts.: since- the inception oft`'_Tco ~O iC tl Survey : and has p.resented Problems.. so complex as to have aff -~'ry ef:. :rounds fo"' over sixty years. Tiloû,rt much.'Or.{~ h~;,~ beer for bitter ControvE'rsy - ,, C'`+~ done throu_ bout the area it has been for the most oarT, promiscuous or in ~y ~-. the nature of large area reconnaissance.l~onSegUeritly sat' sfa,.;t:3L=, knowledge - of the general geol64- or solution of ma:Y.y of the major Ob-- .lems has never :Peen- .gained. For .sO.iTe .ti.(Re a detailed revision of the. 'geology O'° southern Quebec ha:: been contemplated and it was tF'i'}- _ .`ié;4d to beTinriil.l,, th`i S- that the present jFTork iYrJ. trie C.M1Ï?flleiA2,ï,o .(: undertaken. This area was selected because it was thought to a:.. .,.-.__ • ; ^5,st - opportuni tiAS for • Obtc`l.iniri ; a cOïilnrehenSivv kIlo Ÿrle dEs of the ` tr«•'..- ..... ti , i~raphy And because of the presef.C2 of granite masses. of considerable economic importance. Location and size of :dap Area. .The Me_mp rrema.,.=,o- area .as herein. r3efined co.aori ses that part the ; 5 by 30 .minute :1et tpC2re:îa,`;og sheet which ll.es east o- 'y G iLi- ?hrei` Og. It is situated in .southeastern Qu2bvC on t h e international Ç l•. ' -. ' ' . , t t . ~v't•:y .. . i ~Y .~ boU-i1d?ry iY the county of Sta'ristead, and includes the township• of Stan- f % / Stë?dq parts of Magog, ?atley ti - Tt is an area . i r 12 miles- wide- and. .t7 miles 1011~ , apnroximately ?vJ square -Males. P'_n_ysi . ? .~:r %'+.ÇJriiCally . i't represents the transition from - the relatively flat coun- try of .;outhern•~.~-.~,uebec to the ::7'.:,rë rugged ,`toun'tainOUs areas of northern Vermont•'=iild New Hampshire . • Fieldld W.ni r l.. The .Jeological field work unon ',hi ch the renort is based was done during. the. summer'. of 1923. The base : map' used is that of the Depart- ment of ,`il.itia 'and ' Defence published on a. scale of one mile + with 25-foot contours, Lbcations were made mainly 'uÿ pace and com,=ss traverses And comnass trian;ula.tion: 7 , dyre-c-tioht. Lake -,ias5awippi 1 tong „narrow• lake occupying a crook in the valley, has an elevation of 523 -feet. The 'depth of the lake was not as- certained but, appearances would lead one to believe that it ea -,; exceeds 30 feet - and 1-1117 • • siderably. more. 0outh of • iake massawippi there is a id. • upward to .an elevation of 775 feet, then a long gradual descent to an -• elevation of. 683 feet at Fitch Bay. .This part of the valley is o,r-,baby filled to a conSiderable depth with superficial material., Near/_,a',rp, Massawippi wells drilled to a depth of 60 feet are entirely in so--called. gravel. Fitch gay near Magoon Point is reported to be from 40 to 60 feet deep. The narrowness of the valley here clearly indicates that its rock floor is considerably higher than at Zake JAssawippi. In general the rock floor, H.7preL,kent-:.ba6tom, and the land and water surface show an V P/ increaseleelevation from north to south within the map area. The vaLey is unsymmetrical, with a high ridge of abrupt slope on its western side and on the eastern a ridge several hundred feet lower with a gradual slope. The northwestern of the two sections into which, the fl,rr--, is divided . by the-great valley . just described is almost a penirula. is bounded on the west byf;Lake Lilemohremagog and on the east by • 1. , and z_e masi,awippl. In general it constitutes an asyimmetrical " 1 ride with a gradual slope to the west and an abrupt one to the east. The axis lies within a mile or two of thef boundary Valley. Along, the . 1 .-- shore of Lake Mem-ohremarLo is a well-defined low ridge of klIrp-Dey2:--Iian IlimeStone% Between this and the too of the main ridge there are _.,.,n-,.., '0',})/(AsW01( 41 'e0; minor undulationswhich'haver not-very definiteTorm. The hill north of .,:iagoon int assumes such prominence as to dwarf the main ride, which in this section falls away rather rapidly. Farther north Loverina.2:e.1 . sprawls out in a lAcge,' irregular,- though probably shallow, depression on the western slope. ItS'outlet-stream flowin1 south • takes advantage of a break in the ridge and enters Fitch /JJay.. :Northwest of _Lake Idassawi3- -pi. broad depression with-a.horthwestsoutheast'trendand-another-to-t•,... ine-' • . 'Ç rIe south with an eaStweSt-trend destroy this section of the area.: n thesoutheasternseCtion of t e.maP 4area there is in . • A.Yi7«led`j T_'_leTi't S . The writer wishes, to express his appreciation for the infor- mation given him by the quarry operators and many other local residents. He is indebted to the faculty of the Department of ^eology of the Univer- sity of Chicago for laboratory facilities, advice and as::istaIr.•r-, • ciallykto Dr.Albert Johannsen whose continued interest and he:L_r: source of much encouragement. Assistance in the field was r e'r:+d, : e:.i >~?' J.W.trrei; for six weeks aÏiCt. by C W.Wal.lis fOr.the greater.,the part _ ~ season. writer is also indebted to s wife Helen Kerr whose con- . C.,51.0 ~',•~~,: tinued assis ance in .the preparation . of the;~manuscript\~:ade its .H1 ' a; tion possible \znder the pres ure of much otï?ei:, ?i3Ori, \. Previous Work. To. outline completely the;` Ÿ ork done in southern Quebec would --- ~h require more. space and time than the benefits accruing from such a r°e:s le.;'' would warrant. • The. proximity of this section of the country to the o-' - g inal headquarters of the Canadian. *Survey at Montreal. led the earl,, ers to turn their attention to it. Some of-the problems found the .: _.,.c_. became subjects of .controversy, and the "Taconic Question" developed i.h'=o a :,torm center in the geological literature of the period. ~e .CO «;t.N: • - around Lake Champlain and other sections along the:ooun^ ary becaTie Aï'taiît hunting g?"ounds for palrkontolO-;lsts and geologists from across t~c •border. Many articles apneared dealing with the fauna, stra.tigraoliy, is_neous .roC :Cs-, and to a lesser degree .the structure. In the latter part of •the nineteenth cen.turz, revisedd and completed the mapping of the entire southern part of the province - task viich had rten begun' by Sir., William Lo;)-an and carried on by r l ~ colleagues. Since,• „ that time much•wor'; has, been •dOne on small sccitte•r'e ~ areas, faunas, intrusives, mineral deposits, and so on, ._,ut of it tool the form of sys'tematiC areal mapping. •.Of. all. this. work and the literature resulting from it the most outstanding feature is the achievement of .'_,ojan. Though he did. s?o ^o-11.7 ete the mapping of the southern :OaT't of , Que'toec it is quite apparent . that-he was .a.ble 't,o•7oerCeive to a: remarkable' degree.