Lyall, A. K.

McMullen, R. M.

Swift, D. J.P.

Welsh

University of New Brunswick: Centre for Digital Scholarship Journals

R e p o r t s 12 A T i d a l D e l t a w i t h an E b b - F l o o d C h a n n e l S y s t e m in t h e M i n a s B a s i n , B a y of F u n d y : P r e l i m i n a r y R e p o r t * D . J . P . S W I F T , P u e r t o R i c o N u c l e a r C e n t e r , M a y a g u e z , P u e r t o R i c o R . M. M c M U L L E N , B e d f o r d I n s t i t u t e of O c e a n o g r a p h y , D a r t m o u t h , N . S. A . K. L Y A L L , D e p a r t m e n t of G e o l o g y , D a l h o u s i e U n i v e r s i t y , H a l i f a x , N . S . T h e B a y of F u n d y ( F i g u r e 1) h a s h a d a c o m p l e x h i s t o r y of c r u s t a l a n d s e a - l e v e l c h a n g e s s i n c e t h e b e g i n n i n g of the Q u a t e r n a r y P e r i o d . S p a r k e r p r o f i l e s s h o w , a t m a n y p l a c e s , m a s s i v e m a t e r i a l , p r e s u m e d g l a c i a l t i l l , l y i n g d i r e c t l y on T r i a s s i c b e d r o c k . T h i s p r e s u m e d t i l l i s o v e r l a i n by s t r a t i f i e d m a t e r i a l w h i c h c a n b e t r a c e d to g l a c i a l o u t w a s h d e p o s i t s of s a n d a n d g r a v e l o u t c r o p p i n g a l o n g the s h o r e . T h e s t r a t i f i e d m a t e r i a l i s b e i n g r e w o r k e d a n d t h e s a n d a n d g r a v e l i s b e i n g r e d e p o s i t e d in l e n s e s b y t h e p r e s e n t - d a y t i d a l r e g i m e . T h e l e n s e s a l s o c o n t a i n m u c h m a t e r i a l f r o m s h o r e l i n e c l i f f s w h i c h a r e b e i n g e r o d e d a t r a t e s of u p to two m e t r e s / y e a r ( C H U R C H I L L , 1924). T h e t i d a l r i s e in t h e M i n a s B a s i n is ' t h e h i g h e s t r e c o r d e d in the w o r l d b e i n g o v e r 17 m e t r e s a t B u r n t C o a t H e a d (CANADIAN H Y D R O G R A P H I C S E R V I C E S , 1966). In s u c h an e n v i r o n m e n t , t h e r e f o r e , t i d a l c u r r e n t s n a t u r a l l y p l a y a l e a d i n g r o l e in s e d i m e n t a t i o n . T i d a l c u r r e n t v e l o c i t i e s r a n g e , on the a v e r a g e , up to 2. 5 k n o t s in the Mina ' s B a s i n , b u t in c e r t a i n a r e a s , s u c h a s t h e M i n a s C h a n n e l , t h e y m a y b e m u c h g r e a t e r . Figure 1 Index map of Nova Scotia, showing the locat ion of the Minas Basin * M a n u s c r i p t r e c e i v e d 12 A p r i l , 1967. R e v i s e d 10 M a y , 1967. T h i s p a p e r f o r m e d p a r t of a t a l k g i v e n b y t h e two s e n i o r a u t h o r s to t h e N o r t h e a s t S e c t i o n of t h e G. S. A . , 17 M a r c h , 1967. R e p o r t s 13 FROM U.S.H.O. C H A R T 6 0 9 INTERTI D A L Z O N E 0 - 2 F A T H O M S 0 - 3 F A T H O M S Figure 2 Windsor Bay - Bathymetry O n e of t h e m o s t s t r i k i n g of t h e p r e s e n t - d a y t i d a l d e p o s i t s i s t h e W i n d s o r B a y s a n d b o d y c o m p l e x . It c a n b e c l a s s e d m o s t a c c u r a t e l y a s a t i d a l d e l t a ( p r e s e n t l y f o r m i n g a t t h e m o u t h of t h e Avon R i v e r ) b e c a u s e of i t s s u r f a c e m o r p h o l o g y ( F i g u r e s 2 a n d 3). M u c h of t h i s s u r f a c e m o r p h o l o g y i s s i m i l a r to t h a t of the M i s s i s s i p p i d e l t a ( B A T E S , 1953). W e s t e r n B a r a n d M i d d l e G r o u n d a r e l e v 6 e - l i k e b a r s f l a n k i n g t h e m a i n c h a n n e l . A l u n a t e c r o s s - b a r , d i s s e c t e d by t h r e e d i s t r i b u t a r y - l i k e p a s s e s , c a p s t h e m a i n c h a n n e l . T h e c r e s t of M i d d l e G r o u n d b a r , s h o w n on t h e l e f t of F i g u r e 4 , i s n o t on t h e m a r g i n of t he m a i n c h a n n e l b u t on the m a r g i n of t h e e a s t e r n c h a n n e l , w h e r e t h e s t r o n g e s t c u r r e n t s o c c u r . T h i s i s p a r t i a l l y d u e to t h e f a c t t h a t t he t i d a l n a t u r e of t h e r e g i m e h a s p r o d u c e d a s y s t e m of m u t u a l l y - e v a s i v e e b b a n d f l o o d c h a n n e l s , a s o r i g i n a l l y d e s c r i b e d b y VAN V E E N (1936) a n d b y s u c h l a t e r w o r k e r s a s R O B I N S O N(1960, 1966). T h e t i d e in the m a i n c h a n n e l c o n t i n u e s to e b b f o r 15 m i n u t e s a f t e r the t i d e h a s t u r n e d in t h e o p e n M i n a s B a s i n . D u r i n g t h i s t i m e , t h e f l o o d t i d e i s b l o c k e d f r o m e n t e r i n g t h e s a n d b o d y c o m p l e x a n d so m o v e s a r o u n d i t a n d f l o w s up the e a s t e r n c h a n n e l b e t w e e n M i d d l e G r o u n d a n d t h e s h o r e . C u r r e n t v e l o c i t i e s w e r e m e a s u r e d in bo th the e a s t e r n a n d m a i n c h a n n e l s a n d t h e s e a r e s h o w n , p l o t t e d a g a i n s t t i m e , in F i g u r e 5. T h e g r a p h s a l s o s h o w t h a t t h e t i m e of b o t h l o w w a t e r a n d c u r r e n t r e v e r s a l a r e l a t e r in t h e m a i n c h a n n e l t h a n in t h e e a s t e r n c h a n n e l . T h e c u r v e s a r e r e l a t i v e l y w e l l r o u n d e d a n d s y m m e t r i c a l , a n d s h o w l i t t l e d i s t o r t i o n ; p r o b a b l y b e c a u s e the b u l k of t he W i n d s o r B a y s a n d b o d y c o m p l e x i s b a s i c a l l y s u b - t i d a l , s o t h a t t h e r e s p o n s e in t h e c h a n n e l s to the t i d e in t h e o p e n M i n a s B a s i n i s r e l a t i v e l y s e n s i t i v e . O t h e r s a n d b o d y c o m p l e x e s in t h e M i n a s B a s i n w h i c h a r e b a s i c a l l y i n t e r - t i d a l ( e . g. o n e in C o b e q u i d B a y ) , y i e l d t i d a l c u r r e n t c u r v e s w i t h f l a t t e n e d l o w - t i d e s e g m e n t s . T h i s c o n d i t i o n i s b r o u g h t a b o u t b e c a u s e t h e c h a n n e l s d r a i n i n g the b a r s a r e J L l O W I « » »»•* ' < • • • s • • • t^-1s ^ : id • • • • My * • • T Btf r • • h /YJHTT • • f — / • • • •• • • 4 / • • •* * tlr * * VT* • • • • ft* v-> •••• J• • • i n , Jru • • n \ * • / • O t T T X l • • I e • • • • • « • • •)• t t • • • • • *0 » A a• M• • r * • Ve • • r 1 ' fj>*ir • • • •M N A U T I C A L M I L E . S BATHYMETRY FROM ULS.H.O. C H A R T 6 0 9 0 F i n u r e 3 Windsor Bay - Sediment F a d e s R e p o r t s 15 3 H Figure 5 Tidal current ve loc i ty curves from Windsor Bay WINDSOR BAY TIDAL VELOCITIES co ' - I H O Z I^ ? 0 J t - H o o - > - 2 - 1 LxJ > • 3 -- 6 MAIN CHANNEL \ CURRENT REVERSAL LOCAL. LOW WATER T 5 \ T 6 r - 4 — i 1 1 1 1 1 1 r - 3 - 2 - 1 0 1 2 3 4 HOURS FROM LOW WATER AT WALTON Figure 4 Sub-bottom prof i le across the eastern channel (right) and Middle Ground Bar. R e p o r t s 16 t h e i r s h a p e so t h a t c u r r e n t v e l o c i t y a n d w a t e r d e p t h r e m a i n n e a r l y c o n s t a n t . P e t r o g r a p h i c a n d g r a i n - s i z e d i s t r i b u t i o n s t u d i e s of t he s e d i m e n t m a k i n g u p t h e W i n d s o r B a y s a n d b o d y c o m p l e x a r e c u r r e n t l y in p r o g r e s s . T h e s e a r e b e i n g u n d e r -t a k e n to d e t e r m i n e the n a t u r e of t h e t e x t u r a l a d j u s t m e n t to the p r e v a i l i n g h y d r a u l i c r e g i m e , a n d t h e p a r t t h a t t he s a n d b o d y c o m p l e x p l a y s in t h e s a n d b u d g e t of t h e M i n a s B a s i n a s a w h o l e . An a m p l i f i c a t i o n of t h i s s t udy a n d o t h e r s t u d i e s in t h e a r e a w i l l b e p u b l i s h e d in due c o u r s e . T h e p o r t i o n of the w o r k c o n d u c t e d b y D. S w i f t w a s s u p p o r t e d by t h e N o v a S c o t i a R e s e a r c h F o u n d a t i o n a n d by G r a n t s A - 1 9 4 8 a n d A - 2 6 8 6 f r o m the N a t i o n a l R e s e a r c h C o u n c i l of C a n a d a . R e f e r e n c e s c i t e d B A T E S , C . C. , 1953, A r a t i o n a l t h e o r y of d e l t a f o r m a t i o n : A m e r . A s s o c . P e t r o l . G e o l . B u l l . , v . 37, p . 2112-2162. CANADIAN H Y D R O G R A P H I C S E R V I C E , 1966, T i d e a n d C u r r e n t t a b l e s , B a y of F u n d y a n d A t l a n t i c C o a s t of N o v a S c o t i a : T h e Q u e e n ' s P r i n t e r , O t t a w a , , 138 p. C H U R C H I L L , F . J . , 1924, R e c e n t c h a n g e s in t h e c o a s t l i n e in the C o u n t y of K i n g s , N o v a S c o t i a : N o v a S c o t i a I n s t . S c i e n c e P r o c . a n d T r a n s . , v . 16, p . 8 4 - 8 6 . R O B I N S O N , A. H. W. , I960, E b b - f l o o d c h a n n e l s y s t e m s in s a n d y b a y s a n d e s t u a r i e s : G e o g r a p h y , v . 45 , p . 183-199. , 1966, R e s i d u a l c u r r e n t s in r e l a t i o n s h i p to s h o r e l i n e e v o l u t i o n of the E a s t A n g l i a c o a s t : M a r i n e G e o l o g y , v . 4 , p . 5 7 - 8 4 . VEEN, J . V a n , 1936, O n d e r z o e k i n g e n in de H o o f d e n in v e r b a n d m e t de g e s t e l d h e i d d e r N e d e r l a n d s c h e K o s t : Den H a a g . 

A Tidal Delta with an Ebb-Flood Channel System in the Minas Basin, Bay of Fundy: Preliminary Report

https://journals.lib.unb.ca/index.php/ag/article/download/1528/1894

A Tidal Delta with an Ebb-Flood Channel System in the Minas Basin, Bay of Fundy: Preliminary Report

Abstract

Similar works

Full text

Available Versions

University of New Brunswick: Centre for Digital Scholarship Journals