MEM IR OF T HE GE L GICAL UR VEY O S O O S , C TLAND S O . THE GEOLO GY FANNIOH MOUNTAINS COUNTRY AROUND UPPER LOOH MAREE AND STRATH BROOM . (EXPLANATIO N OF SHEET . P E A H L L D J HO R E L L F R . D . S . B N C , . , N , . , TH L T G U G M A . H O U . E A E W NN C . T. CL , , E E G E Y F . R . G S . AND NL , WIT H CO NTR I B UTI O NS B Y L . H I N X M A B I . M A W N A P K . T . O O . , . , C C , B A M R M P E . C . O M . C . AND C T N, , A N D PETR O L O G ICAL N O TES D J H E A L L . J . D . F . R . S O . S . T LL, . , , _ ’ P U B LI S H B Y O R R O F T H E LO R S CO I SS I O N R S O F H I S J ST Y S T R A SU R Y ED DE D MM E MA E E . E D IN B U R G H P R IN TE D F O R H I S M AJE STY ’ S STATIO N E R Y O FF IC E B Y M O R R ISO N G I B B LIM ITE D A T NF I L TA E D . A nd to be purchased from S N F O R D 1 2 1 3 1 4 O NG A C R O N O N E . TA , , L E , L D ; W S R E B R G E D 2 S T . R A K. JO H N S O N I M I N U I N U H W. T , L T , A D E Q A E , D , R S R B I G IS I M I E D 1 04 G F TO N T T D U LIN . H O D G E S F G C O . , , L T , A EE , l n nce S u e M a F rom any Agent for th e sa e o f O rd a rv y ps . F I S H E R N IN 1 P H I R R C O r ou an B ook e lle f o . U L thr gh y s r, r m T W , ADE TE A E , N N w h e ole ole ale e n to th e ade ou de th e O O W . C . h o t L D , , is s Wh s Ag t Tr tsi C oun of ond on ty L . 1 9 1 3 . d ix ence P rice T wo S hillings a n S p . P R E F A C E . THIS M emoir describes the geology of the area included in Sheet 9 2 - S of the one inch map of cotland . It comprises the mountainous ground bounding the upper part of Loch M aree and extending north G annich wards to ruinard Bay and the head of Loch Broom , the F - t i mountains in the south east quadrant , and that par of the ma n th e S m watershed of Highlands situated to the east of trath Broo . R This elevated region forms part of the county of oss , but formerly O f m a it contained small outlying portions of the county Cro rty . The belt of complication due to the post - Cambrian movements crosses the sheet from Loch Broom to the alluvial plain at the head M of Loch aree . To the west of this belt lie large tracts of Lewisian G neiss and T orridon S andstone overlain unconformably by the n m Cambrian formatio . To the east there is a great develop ent of the E S t astern chists , which give rise to some of the wildes scenery in B - - Central oss shire . In the north west corner of the map there is a an d small patch of Triassic Liassic strata, let down against the T orridon Sandstone by a large fault . P J S . The heet was surveyed geologically by B N . each , . Horne , the H inxm an M E G G . late W . unn , C T Clough , L W , H Cadell , reenly , P . T . I . ocock , and C B Crampton The largest part was done by the M r G n late . unn , whose area extended from the Fionn Loch orth to G d A n T e alla ch S ruinard Bay , thence eastwar s by , trath Beg , and S B e inn D O f trath Broom to earg , and southwards to the watershed P M . the F a nnich mountains . essrs each and Horne took part in the mapping of th e belt of complication due to the post - Cambrian movements from S trath na Sh e allag to the southern margin of the D r P E S Sheet . each also surveyed the astern chists around Fionn D m B he inn r. , and Ho e the development of these rocks along e n M r the southern slope of the F n ich range . To . Clough was assigned the complicated tract of Lewisian G neiss stretching from ’ m C hais e in M r G M . Loch aree to Bei u a g Beag ; to reenly , some S h e alla h isolated areas near Loch na g, the Heights of Kinloc ewe , and M M H inxm an P on either side of Loch aree ; to essrs . , ocock , and E S - Crampton , parts of the astern chists in the north east and south th e B e inn nan R am h east corners of map , and on near the head of F i h M r T orrid on S ann e . Loch ; and to Cadell , a patch of andstone - along the north east shore of Little Loch Broom . D etailed descriptions of the Lewisian , Torridonian , and Cambrian rocks , and of the tectonics of the belt of complication , have already appeared in the M emoir on “ The G eological S tructure of the North ” d m West Highlands, which are here reproduced in a condense for n A s E S with some of the horizontal sectio s . regards the astern chists iii iv P re a ce f . the various officers have furnished descriptions of their respective P th e areas . erhaps most interesting feature connected with these rocks is the account O f the remarkable geological structure of th e F nnich a range . A lmost the W hole of the petrology O f the rocks within this S D r A heet has been done by . Teall . few specimens have been D r examined and reported on by . Flett . P . D r . The memoir has been edited by . Horne lates I to V have M r been prepared from photographs taken by . Lunn . We are indebted r R R R e v M . to the . obertson of annoch for the excellent photograph - in P n A n T e allach . of the corrie rock basi on , represented late VI The Bibliography given in the A ppendix has been prepared by M r . Tait . E A J J . H T LL , D irector . G S O eological urvey ffice , 28 J rm n S e . y treet , London 2 1 st 1 9 1 2 November . C N T E N T O S. T E CHAP R I . P AG E IN T R O DUCTIO N A rea P hysical Features H C APTER II . F oR M A T I O N s A N D R O CK G R O U P s G eneral G e ological D escriptio n P revious Literature T ER CHAP III . LEWI S IAN G N E I ss G eneral D e sc ription T h e Fundamental Complex U ltrabasic R ocks B asic R oc ks A c d R c s i o k . P re - Torridonian Intrusion s U ltrabasic D ykes Basic D ykes S y enite D yke P egm atites . T h e Loch M aree S eries and some A ssoc1ated S chi st s M c - S c 1 . i a hist 2 M c - A c - S c . i a tinolite hist G a e - c 3 . r phit S hist 4 . Kyanite G neiss R 5 . G ranular Q uartz ock ua c i 6 . Q uartz S chist and Q rtz M agnetite S h st - 7 . Q uartz Hornblende S chist 8 . Limestone l l 9 . Ca careou s B iotite Hornb ende S c hist 1 0 l . Ch orite S chist 1 1 H l d c a nd Ho n le d C hIO I ite S c . ornb en e S hist r b n e hist 1 2 l M c a nd P r e . Hornb ende S chist with brown i a y it s CHAPTER IV T H E T O R R ID O N SANDS TO NE G ene ral D escription D iabaig G roup A pple cross G roup A ultbea G roup TE CHAP R V . CAM B R IAN FO R MATIO N A o c L a aidh S h S he alla rea fr m Lo h g to trat na g .