l o u R N A L ( ) F QL.JATERNARY S C I I N C E ( 1 9 8 7 ) 2 1 1 3 - 1 3 2 O 1 9 8 7 L o n g m a n C r o u p U K L t r l
( r 2 t , - l J | 7 t t 8 7 0 ) 2 U 1 | I i $ { ) } . ) t l
Late Weichselian and Holocene sea-level
history for a cross-section of western Norway
I O H N I N C E S V E N D S E N a n d J A N M A N C I E R U D U n i v e r s i t y o f B e r g e n , D e p a r t m e n t o f C e o l o g y , S e c . B , A l l e g t . 4 1 , N - 5 0 0 7 B e r g e n , N o r w a y
o o . I I l - l 1 2 . I S S N 0 2 6 7 8 1 7 9
ABSTRACT: The postglacial sea-level hisbry along a cross-sectron of western Norway has been
s t u d i e . d i n d e t a i l . T e n l o c a l s e a - l e v e l c u r v e s w e r e u s e d t o c o n s t r u c t a n e q u i d i s t a n t s h o r e l i n e d i a g r a m , c o v e r i n g t h e l a s t 1 - 1 0 0 0 y e a r s . T h i s i n c l u d e s / 6 r a d i o c a r b o n d a t e s , o f w h i c h t h e m a j o r i t y re p r e s e n t l a c u s t r i n e s e d i m e n t s a t t h e m a r i n e / l a c u s t r i n e b o u n d a r y in c o r e s fr o m e m e r g e d l a k e s . T h e d i s t a n c e betweten the westernmost and easternmost sites is 1 70 km and the difference in total emergence along t h i s p r o f i l e is m o r e t h a n 2 0 0 m . T h e s h o r e l i n e s a l l d i p w e s t w a r d w i t h a d e c r e a s i n g g r a d i e n t t h r o u g h t i m e . T h e L a t e W e i c . h s e l i a n l i n e s a r e a l l s l i g h t l y c u r v e d w h e r e a s t h e H o l o c e n e li n e s a r e a p p a r e n t l y s t r a i g h t . A f t e r t h e f o r m a t i o n o f t h e u p p e r m o s t s h o r e l i n e b y a r o u n d 1 2 8 0 0 B P t h e r e w a s a r a p i d e m e r g e n c e t h a t d e c e l e r a t e d w i t h t i m e t o a n e a r s t a n d s t i l l d u r i n g , t h e Y o u n g e r D r y a s . F r o m a b o u t 1 0 3 0 0 t h e r e w a s a g a i n a r a p i d e m e r g e n c e f o l l o w e d b y t h e T a p e s t r a n s g r e s s i o n a l o n g th e c o a s t a n d a standstill in the most easterly areas. At the western end of this profile, the Tapes transgression started a r o u n d 9 0 0 0 a n d c u l m i n a t e d a p p r o x i m a t e l y 6 0 0 0 B P , w h e n a g r a d u a l r e g r e s s i o n o c c u r r e d . T o t h e e a s t t h e e a r l y H o l o c e n e re g r e s s i o n m i n i m u m o c c u r s a t a y o u n B e r d a t e a n d t h e t r a n s g r e s s i o n m a x i m u m is u o t o 1 5 0 0 v e a r s o l d e r .
K E Y W O R D S : S h o r e l i n e s , s c a - l e v e l h i s t o r y , w e s t e r n N o r w a y , p o s t g l a c i a l , e m e r g e d b a s i n s .
lntroduction
T h e e l e v a t i o n o f s e a l e v e l r e l a t i v e to l a n d i s i n f l u e n c e d b y
several factors, that can be grouped as isostatic, eustatic and
geoidal (Mr)rner, 1976). Io understand the many processes i n v o l v e d , d e t a i l e d s e a - l e v e l h i s t o r i e s m u s t b e c o m p l e t e d fo r
different key areas where these effects can be separated. The
r e l a t i v e s e a - l e v e l h i s t o r y v a r i e s s t r o n g l y f r o m t h e f o r m e r i c e ccntre to the fringe areas of the Pleistocene ice sheets. A
cross-section of western Norway (Figs 1 and 2), from the
outermost coast to the head of the fjords, covering the entire p e r i o d fr o m a p p r o x i m a t e l y 1 2 8 0 0 B P t o t h e p r e s e n t , p r o v i d e s t h e d a t a n e c e s s a r y k r s t u d y in d e t a i l th e i m p a c t o f t h e s e v a r i o u s effects. The difference in total emergence along this profile is m o r c t h a n 2 0 0 m .
F e n n o s c a n d i a i s a c l a s s i c a l a r e a f o r s t u d i e s o f a n c i e n t s h o r e l i n e s a n d s e a - l e v e l h r s t o r i e s . E a r l y s t u d i e s w e r e h a m p e r e d b y t h e l a c k o f p r e c i s e d a t i n g te c h n i q u e s . A f t e r th e i n t r o d u c t i o n o f t h e r a d i o c a r b o n d a t i n g m e t h o d , a l a r g e n u m b e r o f w e l l - documented local sea-level histories have been developed in S c a n d i n a v i a . M u c h o f t h e p r e s e n t k n o w l e d g e fo r s o u t h e r n N o r w a y i s r e v i e w e d b y H a f s t e n ( 1 9 8 3 ) a n d A n u n d s e n ( 1 9 8 5 ) .
T h e a i m o f t h i s s t u d y is to c o r r e l a t e t h e e x i s t i n g s e a - l e v e l d a t a
and provide a regional synthesis of the sea-level history of a
relatively large area (from Sunnmore to Srtr-f randelag, Figs 1 and 2) that represents a cross-section of the west coast of N o r w a y . M o s t o f t h e p r i m a r y o b s e r v a t i o n s u s e d f o r t h i s a n a l y s i s w e r e t a k e n fr o m e x i s t i n g l i t e r a t u r e . T h e c o m p r e h e n s i v e w o r k s
b y K j e m p e r u d ( 1 9 8 1 , 1 9 8 6 ) w e r e e s p e c i a l l y h e l p f u l a n d t h e y c o n s t i t u t e a l a r g e s h a r e o f t h e i n p u t d a t a in t h i s s t u d y . H o w e v e r , s o m e o r i g i n a l d a t a c o n c e r n i n g t h e s e a - l e v e l h i s k r r y o f S u n n - m o r e a r e a l s o p r e s e n t e d i n t h i s p a p c r .
T h e r e s u l t s a r e p r e s e n t e d f i r s t i n a s h o r e l i n e d i a g r a m ( F i g . 1 1 ) , t h a t s h o w s th e a g e , c u r v a t u r e , a n d t i l t o f t h e s h o r e l i n e s i n t h i s region for every .l
000 years; and secondly in a suite of sea-level c u r v e s (F i g . 1 2 ) f o r s e l e c t e d s i t e s a l o n g t h e p r o f i l e th a t w e r e c o n s t r u c t e d f r o m t h e a f o r e m e n t i o n e d d i a g r a m . C o n s i d e r i n g t h e q u a l i t y a n d t h e v o l u m e o f t h e i n p u t d a t a , th is is o n e o f t h e m o s t p r e c i s e s h o r e l i n e d i a g r a m s , a n d s u i t e o f s e a - l e v e l c u r v e s ,
ccinstructed for any area of comparable size.
T h i s s t u d y p r o v i d e s a b a s e fo r a n a l y s i n g t h e d i f f e r e n t c a u s a l f a c t o r s o f t h e l a r g e v a r i a t i o n s i n r e l a t i v e s e a - l e v e l s , w h i c h w i l l be addressed in a future paper. The sea-level history of western Norw,ay which is presented here is also important for under- s t a n d i n g t h e s t r a t i g r a p h y a n d r e g i o n a l d i s t r i b u t i o n o f Q u a t e r - n a r y s e d i m e n t s , f o r d a t i n g b o t h th e t i m e o f d e g l a c i a t i o n a n d t h e a g e o f a r c h a e o l o g i c a l s i t e s ( e . g . B j e r c k , 1 9 8 6 ) , a n d f o r r e c o n - s t r u c t i n g t h e p a s t e n v i r o n m e n t .
Glacial history
T h e i s o s t a t i c a n d g e o i d a l c o m p o n e n t s o f s h o r e l i n e d i s - p l a c e m e n t a r e c l o s e l y r e l a t e d t o t h e g l a c i a l h i s t o r y o f t h e a r e a , a n d a r e v i e w o f t h e g l a c i a l a n d p o s t g l a c i a l e v e n t s i s p r o v i d e d lourn.rl ot Quatt'rn.rry St ien< e
I O U R N A L C ) F C ) U A T E R N A R Y S ( , I E N C E
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2 a 'F i g u r e 1 M a p o i i c e m . t r g i n s o f t h e F c n n o s c : a n d i a n i c e s h e e t w h i c h a r e n r . r r k e r l w i t h h c . r v y li n c s ( c l a s h e r i f o r a l t e r n a t i v e s ) . l - h e W e i r - h s e l i . r n n r a x i n r u n t ( l t l - 2 0 0 0 0 y e a r s [3 [ ' i s r e p r o r l u c e c l f r o n t A n c l e r s e n ( 1 9 f ] 1 ) a n c i B o u l t e n e t . r l . ( 1 9 U 5 ) , a n c l t h e Y t . r u n g e r D r y a s f r o m M a n g e r u c l ( 1 9 8 7 ) . T h e s t u c l v a r e . r i s f r a m c d , 'r r r c l t h e p r o l i l e in F i g , . 1 6 i s m . r r k e c l .
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The coast of western Norway was ice free during the Alesund r n t e r s t a d i a l , a r o u n d 3 0 0 0 0 B P , a n d w a s s u b s e q u e n t l y c o v e r e d b y t h e S c a n d i n a v i a n i c e s h e e t d u r i n g t h e L a t e W e i s c h s e l i a n m a x i m u m ( M a n g e r u d e t a l . 1 9 8 . 1 ; L a r s e n e t a l ' , 1 9 B Z ) F o r o v e r a centu ry the th ickness of the ice in this area has been a matter of d e b j t e . N e s j e e t a l . ( i n p r e s s ) h a v e r e c e n t l y a r g u e d th a t t h e m o u n t a r n s u m m r t s w e r e n o t i c e - c o v e r e d , a n d t h e y h a v e p r e s e n t e d a r e g i o n a l r e c o n s t r u c t i o n o f t h e i c e s h e e t d u r i n g th e W e i c h s e l i a n m a x i m u m . l f t h e i r m o d e l ( F i g . 1 6 ) i s c o r r e c t , t h e l o a d o f t h e i c e c a n b e c a l c u l a t e d , p r o v i d i n g a n a l t e r n a t i v e m e t h o d f o r e s t i m a t i n g g l a c i o - i s o s t a t i c d e f o r m a t i o n . B e c a u s e t h e i r m o d e l is in d e p e n d e n t o f t h e s h o r e l i n e h i s t o r y o f t h e r e g i o n , the shoreline history data can be used to test it. We have not yet oerformed that exercise.
According to Bugge (i 980) the ice sheet reached the edge of t h e c o n t i n e n t a l s h e l f ( a g a i n ? ) a s l a t e a s 1 3 0 0 0 B P . l f t h i s i s c o r r e c t , th e d e g l a c i a t i o n o f t h e s h e l f w a s e x t r e m e l y r a p i d , a s there is evidence to suggest that the outer coastal area was i c e - f r e e b e f o r e . l
2 5 0 0 B P ( M a n g e r u d e t a l . , 1 9 8 . 1 ; L i e e t a l , . l
9 8 3 ; K i e m p e r u d , 1 9 8 6 ; F o l l e s t a d , 1 9 8 6 ) . S u c h a r a p i d d e g l a c i a t i o n o f t h e s h e l f r e g i o n i s fe a s i b l e b e c a u s e t h e d o m i n a n t m e c h l n i s m o l i c e - r ( ' t r e . l l w . r s t a l v i n g .
The raoid retreat continued in the deep fiords (Mangerud, 1 9 B O ; S o l l i d a n d S o r b e l , . l
9 7 9 ; R e i t e e t a l . , 1 9 8 2 ) u n t i l t h e a b r u p t c o o l i n g a t t h e o n s e t o f t h e Y o u n g e r D r y a s a t a b o u t 1 1 0 0 0 y e a r s B P . D u r i n g t h e Y o u n g e r D r y a s t h e i c e f r o n t g e n e r a l l y h a l t e d o r r e a d v a n c e d i n S c a n d i n a v i a ( M a n g e r u d , 1 9 8 0 ) l n
t h e r e w a s a m i n o r r e a d v a n c e ( R e i t e e t a l , 1 9 8 ) ) , w h e r e a s in S u n n m o r e , a l t h o u g h t h e d e t a i l e d h i s t o r y i s u n k n o w n , th e r e h a s p r o b a b l y n o t b e e n a n y m a j o r r e a d v a n c e ( N l a n g e r u d , 1 9 8 0 ) . I n t h e l a t t e r a r e a n u m e r o u s c i r q u e g l a c . i e r s a p p e a r e d d u r i n g t h e Y o u n g e r D r y a s (L a r s e n e t a l . , . l
9 8 4 ) , b u t t h e y w e r e t o o s m a l l to influence isostatic depression to any great degree. Shortly after 1 0 0 0 0 B P m o s t o f t h e i c e s h e e t ir i S c a n d i n a v i a d i s a p p e a r e d ( A n d e r s e n , 1 9 U . 1 ) .
Method used for constructing relative sea- level curves
T h e m a i n in p u t d a t a in t h i s s t u d y a r e s e v e n s e a - l e v e l c u r v e s ( F i g '
B except Borgundvig and Fig. 1 0 except Verdalsora) that were
a l I c o n s t r u c t e r . l a c c o r d i n g to t h e c l a s s i c a l S c a n d i n a v i a n m e t h o d , w h i c h r e l i e s o n t h e s t r a t i g r a p h y i n l a k e b a s i n s . W e c o n s i d e r t h i s t h e m o s t o r e c i s e m e t h o d a v a i l a b l e f o r t h i s a r e a t o d e t e r m i n e both the elevation and the age of former sea levels. A brief d e s c . r i p t i o n o f t h i s m e t h o d fo l l o w s . M o r e c o m p l e t e d i s c u s s i o n s a r e p r o v i d e d i n , f o r e x a m p l e , H a f s t e n ( 1 9 6 0 , I9 8 3 ) , K i e m p e r u d ( 1 9 8 1 ) , K a l a n d ( 1 9 8 4 ) , a n d A n u n d s e n ( 1 9 8 5 ) .
S e d i m e n t c o r e s (F i g . 3 ) a r e t a k e n fr o m s m a l l la k e s a n d b o g s s i t u a t e d a t d i f f e r e n t e l e v a t i o n s i n a s m a l l a r e a . l t s h o u l d b e e m o h a s i s e d t h a t it i s t h e p o s i t i o n o f t h e s e a le v e l re l a t i v e t o t h e
L A T E W E I C - H S E L I A N A N D I I C ) L O C E N E S E A L E V E L H I S T O R Y F O R A C - R O S S . S E C , T I O N
O F W I S T E R N N C ) R W A Y l t . 5
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F i g u r e 2 M a p o f t h e . t r e a f r o m S u n n n r o r e t o S o r T r o c l c l a g w i t h a k e y n r a p o f s o u t h e r n N o r w a y . e v i d e n c e m e n t i o n e c i i n t h e t e x t a r e m a r k e c i . T h e Y o u n g e r D r y a s e n c i m o r a i n e is f r o m Sollicl a n d t r a c e c l f r o n r K j e n s t a d ( 1 980), sliehtly ntodifieci i n S u n n n r o r e .
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1 0 " 1 1 o
A l l s i t e s w i t h a v a i l a b l e s e a le v c l c u r v e s o r o t h e r S o r b e l ( 1 9 7 9 ) . T h e i s o b a s e s o f t h e M a i n L i n e .r r e
s'
o u t l e t o f t h e s e b a s i n s t h a t d e t e r m i n e s w h e t h e r t h e s e d i m e n t s a r e m a r i n e , b r a c k i s h o r l a c u s t r i n e ( F i g . 3 ) . T h u s th e c o m p a c t i o n o f s e d i m e n t s d o e s n o t p r o v i d e a n y p r o b l e m w h e n t h e e l e v a t i o n o f f o r m e r s e a l e v e l s a r e d e t e r m i n e d . I n o r d e r t o a v o i d t h e interpretive problems due to possible erosion of the outlet, b a s i n s w h i c h h a v e a n o u t l e t o v e r a b e d r o c k t h r e s h o l d a r e p r e f e r r e d . A l l o f t h e b a s i n s i n S u n n m o r e ( F i g . 5 ) e x c e p t F r o y s t a d m y r a l l a n d l l l , a n d L i l l e r e s t j o n n h a v e b e d r o c k th r e s - h o l d s . In T r o n d e l a g ( F i g . 1 0 ) , h o w e v e r , o n e t h i r d o f t h e b a s i n s h a v e a m o r a i n e t h r e s h o l d , b u t i n a l l t h e s e c a s e s w e ( S u n n m o r e ) a n d K j e m p e r u d ( 1 9 8 6 ) ( T r a n d e l a g ) h a v e ju d g e d th a t e r o s i o n o f t h e o u t l e t h a s b e e n m i n o r , c e r t a i n l y le s s t h a n o n e m e t r e . T h e threshold elevation defines the high tide of the former sea level
because as long as sea water flows into the basin the sediments
w i l l b e m a r i n e o r b r a c k i s h ( K i e m p e r u d 1 9 8 1 , 1 9 8 2 ) .
The age of the sea level corresponding to the outlet of each
l a k e i s d e t e r m i n e d b y i d e n t i f y i n g a n d d a t i n g t h e b o u n d a r y between the brackish and lacustrine sediments in the cores r a i s e d f r o m th e la k e fl o o r (F i g . 3 ) . T h e m e t h o d r e q u i r e s t h a t th e r e i s n o t a n h i a t u s b e t w e e n t h e b r a c k i s h a n d l a c u s t r i n e s e q u e n c e s .
As these sediments were deposited at several metres depth in
l o c k e d b a s i n s , t h e r e w a s a l m o s t a l w a y s c o n t i n u o u s s e d i m e n - t a t i o n a c r o s s th a t b o u n d a r y d u r i n g e m e r g e n c e . T h i s c a n b e
tested in most cases by pollen and diatom stratigraphy. On the
other hand, during submergence, when the sea transgressed
into former lakes, tidal currents frequently eroded the sofl l a c u s t r i n e g y t t j a s e d i m e n t s ( K a l a n d 1 9 8 4 ) , le a v i n g a n h i a t u s i n the record. Because of this, we have few basins where the onset of the Tapes transgression is well dated.
The elevation and age of the former sga-levels as determined
f o r e a c h l a k e a r e p l o t t e d in a n a g e - e l e v a t i o n d i a g r a m ( e . g . F i g . B ) , a n d a s e a - l e v e l c u r v e is d r a w n a s a r e g r e s s i o n l i n e b e t w e e n t h e p o i n t s f o r a l l l a k e s w i t h i n a r e s t r i c t e d a r e a . T h e r e s o l u t i o n o f the curve depends on the difference in elevation between a d j a c e n t l a k e s , a n d w i l l t h e r e f o r e v a r y b o t h w i t h i n e a c h diagram, and between different diagrams.
Most radiocarbon dates on the lacustrine/brackish boundary
i n t h e c o r e s w e r e ta k e n f r o m t h e l a c u s t r i n e s e d i m e n t s o n l y , t h u s a v o i d i n g p r o b l e m s w i t h r e s e r v o i r a g e , re s e d i m e n t a t i o n e t c . T h i s m e a n s t h a t d u r i n g e m e r g e n c e s t h e r a d i o c a r b o n a g e s h o u l d b e s l i g h t l y y o u n g e r t h a n th e b o u n d a r y , a n d d u r i n g a t r a n s g r e s s i o n s l i g h t l y o l d e r . T o a v o i d c o n t a m i n a t i o n o f p e n e t r a t i n g r o o t s f r o m s u b m e r g e d p l a n t s ( K a l a n d e t a l . 1 9 8 4 ) a n d r e s e d i m e n t a t i o n o f o r g a n i c r e m a i n s , t h e N a O H - s o l u b l e f r a c t i o n i s g e n e r a l l y u s e d .
The sediment sequences were correlated by pollen-, litho- and
tephra-stratigraphy, providing independent control of the inter-
nal consistency of the radiocarbon dates.
Mollusc dates are corrected for isotopic fractionation (to - 2 5 % . PDB) and a marine reservoir a g e o f 4 4 0 y e a r s , b e i n g t h e s t a n d a r d u s e d f o r t h e N o r w e g i a n c o a s t ( M a n g e r u d a n d
i l 6 I O U R N A L O F Q U A T E R N A R Y S C I E N C E
F i g u r e 3 A i : r o s s - s c c t i o n o f a b a s i n a t t h r e e d i f f e r e n t p o i n t s in t i m e . T o p : w h c n t h e s e a le v e l ( 1 ) w a s w e l l a b o v e t h e threshold. Centre:
w h e n t h e s e a le v e l ( 2 ) w a s a t t h e t h r e s h o l d . Bottom: present day, w h e n s e a le v c l ( . 1 ) i s b e l o w t h e t h r e s h o l d . T h e s k e t c h d e m o n s t r a t e s t h e s e r l i m e n t . r r y s e ( l u e n ( e in t h e l a k e a n d i l l u s t r a t e s h o w t h e s e d i m e n t a r y e n v i r o n m e n t w a s d e t e r m i n e d b y t h e e l e v a t i o n o f t h e c - r u t l e t o f t h e l . r k e (t h e t h r e s h o l d ) - I o t h e r i g h t i s s h o w n a t y p i c a l c o r e s e q u e n c c .r n c l t h e u s u a l h o r i z o n f r < . r m w h i < : h ra d i o c a r b o n s a m p l e s w e r e c o l l e c t e d . T h c b a s i n w o u l d g i v e o n e p o i n t i n a s e a - l e v e l c u r v e ( e . g . F i g . 8 ) . a n c l to ( : o n s t r u c t . t c u r v e , b a s i n s a t d i f f e r e n t e l e v a t i o n s w e r e c o r e c l . M r r i i f i c d f r o m H a f s t e n (l 9 8 3 ) .
C u l l i k s e n , 1 9 7 4 ) . l n s r i m e i n s t a n c e s m o l l u s c a n d l a c u s t n n e g y t t j a d a t e s c a n b e g e o l o g i c a l l y c o r r e l a t e d , and they always y i e l d s i m i l a r r e s u l t s , in d i c a t i n g t h a t t h e r e s e r v o i r a g e h a s v a r i e d l i t t l e t h r o u g h t h e t i m e p e r i o d s t u d i e d .
Strategy for constructing and testing the shoreline diagram
The research strategy and the organisation of this part of the p a p e r is s h o w n in a f l o w d i a g r a m (F i g . a ) . T h e t w o - b r a n c h p a t h i s c h o s e n b e c a u s e S u n n m o r e i s w e l l c o v e r e d w i t h L a t e W e i c h - selian data, but poorly covered for the Holocene, whereas for
Sor-Trondelag the opposite is the case. From the Noromore area
lying between, only scattered data are available. We have
therefore constructed a Late Weichselian diagram for Sunnmore
(Steps 2-6) which is extended eastward to incorporate the data from Sor-Trsndelag (Step 7). A Holocene diagram fr:lr Sar-f ran-
delaB (Step 9) is extended to the west and modified by the data
f r o m S u n n m u r e ( S t e p 1 0 ) . T h e t w o d i a g r a m s a r e s u b s e q u e n t l y c o m b i n e d ( S t e p 1 I ) i n t o o n e s i n g l e d i a g r a m ( F i S . 1 1 ) t h a t c o v e r s t h e e n t i r e a r e a a n d ti m e - s p a n . S e a - l e v e l c u r v e s d e r i v e d f r o m th i s d i a g r a m a r e th e n te s t e d a g a i n s t t h e o r i g i n a l i n p u t d a t a (S t e p 1 4 ) a n d o t h e r in d e p e n d e n t d a t a (S t e p I 3 ) . T h e c u m u l a t i v e e f f e c t s o f p o t e n t i a l e r r o r s th a t m i g h t a r i s e in e a c h s t e p a r e d i f f i c u l t to e s t i m a t e , b u t t h e d e v i a t i o n b e t w e e n th e f i n a l c o m p o s i t e d i a - g r a m a n d t h e e m p i r i c a l d a t a a p p e a r s d i r e c t l y f r o m F i g u r e s B , 1 0 a n d 1 3 .
Step 1. lsobases
lsobases are imaginary contours between sites of equal emergence operating over the same length of time (Andrews,
1 9 7 0 ) . A n e q u i d i s t a n t s h o r e l i n e d i a g r a m ( e . g . F i g . 1 1 ) is s i m p l y
a cross-section perpendicular to the local isobase direction,
d i s p l a y i n g t h e e l e v a t i o n a n d ti l t o f s h o r e l i n e s o f d i f f e r e n t a g e s . I n practice it has to be constructed from data collected also outside
the cross-section plane. Observations are then projected along
t h e i s o b a s e s i n t o t h a t p l a n e , a s s u m i n g th r e e p r e m i s e s fo r c o n s t r u c t i n g a n e q u id i s t a n t s h o r e l i n e d i a g r a m : ( . l ) t h e d i r e c t i o n s of the isobases are known, (2) the isobases are parallel within the area and (3) the directions of the isobases have not changed d u r i n g th e t i m e f o r w h i c h t h e s h o r e l i n e s a r e s h o w n . C o m m e n t s
on each of these premises are provided below.
1 . Along the western coast of Norway there are three subse- q u e n t s h o r e l i n e s o f d i f f e r e n t a g e s t h a t a r e p a r t i c u l a r l y w e l l
developed, and which have been used to establish isobases
( e . g . U n d i s , . l
9 4 2 ; R e i t e , 1 9 6 8 ) . T h e y i n c l u d e th e s t r o n g l y d i a c h r o n o u s p o s t g l a c i a l m a r i n e l i m i t , t h e Y o u n g e r D r y a s l e v e l th a t S o l l i d a n d K j e n s t a d ( 1 9 8 0 ) c a l l e d T h e M a i n L i n e , a n d t h e T a p e s l e v e l . T h e M a i n L i n e is th e o n l y s h o r e l i n e t h a t i s m a p p e d t h r o u g h o u t t h e e n t i r e a r e a , a n d w h i c h i s s u p p o s e d t o h a v e b e e n fo r m e d a s a n e a r l v s v n c h r o n o u s s h o r e l i n e . I n
this study we have used the isobases drawn for the Main Line
b y K j e n s t a d ( 1 9 8 0 ) , a n d g i v e n i n l e s s d e t a i l i n S o l l i d a n d K j e n s t a d ( 1 9 8 0 ) . T h i s is o b a s e m a p w a s c o n s t r u c t e d b y u s i n g a large number of terrace observations in a statistical t r e n d - s u r f a c e a n a l y s i s . T h e i s o b a s e s a r e i n a g r e e m e n t w i t h t h e d i r e c t i o n e a r l i e r f o u n d b y U n d A s ( 1 9 4 ) ) a n d R e i t e ( . 1 9 6 8 ) a n d a r e a l s o c o n f i r m e d b y o u r s t u d y fr o m S u n n m 6 r e ( S t e p s . l - 6 ) , e v e n t h o u g h w e h a v e m o d i f i e d th e m s l i g h t l y o n t h e
F i g u r e 4 A f l o w c l i a g r a n r s h o w i n g t h e p r o c e c l u r e l v c u s e c l t < r c o n s t r u c t .r n d te s t th e s h o r e l i n e di.tgram (Fig. i l ) for Sunnntore and S o r T r o n c l e l a g i n w c s t e r n N o r w , . t y . T h e o r g . r n i s a t i o n o f t h c p a l t e r a l s o f o l l o w s t h e s e s t e p s . T h e step nuntbers are incliratccl o n t h e l e f t s i c l e o f e a c h b o x .
C h r o n o l o g i c a l l r a m e w o r k f o r S u n n m o r e
S e a - l e v e l c u l v e s t r o m S o r - T r o n d e l a g
A Holocene shorelne diagram or Sor-Trondelag
Modification b y d a t a f r o m S o r - T r o n d e l a g
Sea-level cwes d e d u c e d f r o m t h e diagram
T e s t agahst h O U t data
L A T t r W E l ( . f l S E L l A N A N D l l C ) L ( ) C E N E S E A - L E V E L H I S T ( ) R Y F O R A ( . R ( ) S S - S t ( . T l ( ) N O F W E S I E R N N O R W A Y
I
o u t e r c o a s t . E r r o r s d u e t o u n c e r t a i n t i e s i n t h e d i r e c t i o n o fisobases are considered to be negligible compared to other
sources of error.
T h e i s o b a s e s a r e n o t s t r i c t l y p a r a l l e l w i t h i n t h e a r e a lF i g . 2 ) , a n d t h e s h o r e l i n e d i a g r a m w i l l t h e o r e t i c a l l y o n l y s h o w t h e t r u e t i l t o f t h e l i n e s c l o s e to t h e p r o j e c t i o n p l a n e . H o w e v e r , t h e a b s o l u t e a n d r e l a t i v e a g e s o f a l l l i n e s w i l l s t i l l b e c o r r e c t , a n d t h e e r r o r in t i l t f o r a r e a s o u t s i d e t h e p r o j e c t i o n p l a n e is c o n s i d e r e d n e g l i g i b l e . T h e i s o b a s e s o f t h e M a i n L r n e w e r e n o t e s t a b l i s h e d a t F r o y a b y K j e n s t a d ( 1 9 8 0 ) , a n d w e h a v e extrapolated the 40 m isobase (dashed line) northwards from S u n n m o r e , p a r a l l e l w i t h t h e 6 0 m i s o b a s e ( F i g . 2 ) , a n d i n a g r e e m e n t w i t h t h e s e a - l e v e l c u r v e fr o m F r o y a ( F i g . 1 0 ) .
UndAs (.1 942) demonstrated that the isobases corresponding t o t h e M a i n L i n e a n d t h e T a p e s le v e l a r e a p p r o x i m a t e l y p a r a l l e l in t h i s a r e a . T h i s i s t e s t e d a n d c o n f i r m e d b y o u r c o r r e l a t i o n s . K i e m p e r u d ( 1 9 8 6 ) f o u n d n o d e m o n s t r a b l e c h a n g e i n t h e d i r e c t i o n o f t h e is o b a s e s i n S o r - T r o n d e l a g t r o m
the Younger Dryas up to the present day. Also the isobases
f o r t h e p r e s e n t e m e r g e n c e (B a k k e l i d , 1 9 7 9 ) s e e m t o b e p a r a l l e l w i t h t h e o l d e r i s o b a s e s . F r o m t h i s i n f o r m a t i o n w e p o s t u l a t e a s a f i r s t a p p r o x i m a t i o n t h a t t h e i s o b a s e s f o r a l l s h o r e l i n e s i n t h i s a r e a a r e a p p r o x i m a t e l y p a r a l l e l . H o w e v e r , with several different Drocesses involved in relative sea-level c . h a n g e s , i t i s h i g h l y i m p r o b a b l e t h a t t h e i s o b a s e s s h o u l d r e m a i n p a r a l l e l i n d e t a i l o v e r s u c h a l a r g e a r e a f o r m o r e th a n 1 2 0 0 0 y e a r s . S r g n i f i c a n t c . h a n g i : s i n t h e d i r e c t i o n o f i s o b a s e s s h o u l d b e c l i s c l o s e d a s s y s t e m a t i c d e v i a t i n g d a t e s in t h e c . o m p o s i t e c l i a g r a m ( F i g . 1 1 ) .
Step 2. Chronological framework for Sunnmore
The clescriotion of the method we usecl to construct the sea-level c u r v e s p r o v i d e c l a b o v e , s h o w s t h a t t h e d a t i n g o f t h e m a r i n e
l a c u s t r i n e s e d i m e n t b o u n d a r y i n e a c h b a s i n i s c r u c i a l . T h i s b o u n d a r y r s th e r e f o r e r a d i o c a r b o n d a t e d in a l l b a s i n s . l n o r d e r k r i m p r o v e th e a c c u r a c y a n d t o a v o i d e r r o r s w i t h i n d i v i d u a l r a d i o c a r b o n d a t e s , a n d s y s t e m a t i c c r r o r s w i t h i n a b a s i n , t h e s e d a t e s w e r e n o t u s e d d i r e c t l y , b u t a s s e s s e d i n t h e f o l l o w i n g m a n n e r .
I n S u n n m o r e ( F i g . 5 ) t h e r r : . r r e s e v c r a l l i t h o l o g i c a l a n d p o l l e n - s t r a t i g r a p h i c . h o r i z o n s ( b o u n d a r i e s ) p o s t u l a t c d k r b e i s o c h r o n o u s w i t h i n t h i s r e s t r i c t e r 1 a r e a ( F i g . 6 ) , t h a t c a n b e i d e n t i f i e d i n n e a r l y a l l b a s i n s ( L i e e t a l . 1 9 f i . ) ; L a r s e n e t a l . , . l
9 { 3 4 ; M a n g e r u d e t a l . , i 9 8 , 1 ; S v e n d s i : n , l 9 B 5 ) . K r r s t r a n s e n e t a l . ( 1 9 8 7 ) u s e d t h e s e h o r i z o n s t o c o r r e l a t e t h e c o r e d lt a s i n s ( F i g . 6 ) . I n t h i s w a y a l l r a d i o c a r b o n c l a t e s c o u l c l b e t r e a t e d a s o n e s e c l u e n c e , a n c l th c a g e s o f t h e s t r a t i g r a p h i r . a l h o r i z o n s w e r e estimatecl as a mean of several rlatcs.
I n e a c h b a s i n , t h e a g e o f t h c i s o l a t i o n c o n t a c t ( b r a c k i s h / l a c u s - t r i n e b o u n d a r y ) w a s e s t i m a t e c l b y c o r r e l a t i o n t o t h e s e d a t e d h o r i z o n s . W h e r e th e is o l a t i o n c o n t a c t c l i c l n o t c o i n c . i d e w i t h o n e o f t h e h o r i z o n s , i t s a g e w a s e s t i m a t e d b y u s i n g s e d i m e n t a t i o n r a t c s a n d / o r t h e a c . t u a l r . r d i o c a r b o n d a t e i o r t h . r t p a r t i c u l a r i s o l a t i o n , th e m a i n c r i t e r i o n b e i n g t h a t t h e a g e s h o u l d b e c o n s i s t e n t w i t h t h e g e n e r a l f r a m c w o r k ( F i g s . 6 a n c l 7 ) .
F o r t h e l i t h o s t r a t i g r a p h i c b o u n d a r y l t c t w e e n t h e L e i r s t a d M e n r b e r ( Y o u n g e r D r y a s ) .r n d H a t l e n F o r n r a t i o n ( H o l o c e n e ) , w c h a v e u s c d t h e c o n s e r v a t i v e e s t i m a t c o f 1 0 2 0 0 y e a r s B P , e v e n t h o u g h s e v e r a l d a t e s s u g g c s t a s l i g h t l y o l d e r . r g c o f ' l 0 3 0 0 - 1 0 - 5 0 0
B P . In a l l b a s i n s t h i s b o u n d a r y c o r r e s p o n c l s w i t h a d i s t i n c t r i s e i n t h e B e l u l . 1 c . u r v c s , a n c l i s i n t e r p r e t e d a s r e f l e c t i n g a n . , r b r u p t c l i m a t i c a m e l i o r a t i o n w i t h i n t h e w , h o l e a r e a . li t h c l a t t e r : r g e i s c o r r e c t th e s l o w i n g o f t h e e n r e r g e n c e d u r i n g th e Y o u n g c r D r y a s (F i g . B ) w i l l b e l e s s p r o n o u n c e c l .
Step 3. Sea-level curve for Sula
T h e L a t e W e i c h s e l i a n p . r r t o f t h e r u r v e ( F i g . f i ) i s ta k e n fr o m L i c e t a l . ( l c ) 8 3 ) , w h c r e d c t a i l c c l c l o c u m e n t a t i o n i s p r o v i c l e d . T h e
Torvlomyra B o r g u n d E n d r e v a t n S l e t t e b a k k t j o n n N o r e t i o n n S a u d e d a l s m y r a g r e v a t n \ G j o l v a t n \ Lerstadvatn \ L i l l e r e s t j o n n \ S t e t t e t r o n n
K u l t u r m y r a I l l l l t L i t l e v a t n S k o l e m y r a F r o y s t a d m y r a n e
F i g u r e 5 T h e . r r c . r in v c s t i f l a t e c l i n S u n n n t o r e . A l l b a s i n s u s e c i f o r t h e c o n s t r u c t i o n o f t h e s e a , l e r v c l c u r v e s fo r I t ' i n r a v , S u l a .r n c l S t e t t e ( F i g . t3) are marked. The c:urvcs a r e p r o l e c t e d a l o n g t h e Y o u n g e r D r y . r s is o b a s e s i n t o t h e p r o j c c t i o n p l . r n e f o r S u n n m r a r e . T h e / , 2 U a n d l 9 m a . s . l . is o b a s e s a r e d r a r v n .
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1 2 1 1 ' , 1 0 z Borgund,(Hafs_!,9r11979) ---
a 7 6 5 4 3 2 1
S T E T T E
E s t i m a t e d a g e s !
+ 1 0 6 0 0 y r s B . P . T h e V e d d e A s h f o u n d ' a t t h e b r a c k i s h / l a c u s t r i n e b o u n d a r y . 1 0 7 5 0 y r s B . P . S e d i m e n t a t i o n r a t e
b e l o w t h e V e d d e A s h
' 1 2
1 1 l 0 9 8 7 6 5 4 3 2 1
l 0 3 y e a r s B . P .
F i g u r e B S t ' a l e v e l c u r v c s i o r [ S o r g u n c l r ' . r g ( L o n g r , . r e t a l . , l 9 U ] ) , L c i r r r r v ( S v e n c l s e n , l 9 u 5 ) , S u l a ( L i e e t a l . , l ( ) u . 1 , t h i s p a p c r ) . r n c l S t e t t e ( t h i s p a p e r ; . t h c s o l i c l l i n e s s h o r v t h c e r - n l r i r i c . r l ( L l r v e s a s t i r a w n b y t h e r i i f f c r e n t . r L r t h o r s . l h c c l a s h e t l l i n e s s h o r , v t h e c u r v e s c l e r i v e d f r o n r t h c s h o r e l i n r : c l i . r g r a n r { F i g . l l r f o r t h e s . t n r c s i t e s w ' h e r c c 1 c . r , i . t t i n g f r o n r t h c c n t p i r i c . r l (s o l i c l l i n e ) c L r r v e .
J ( ) U R N A L O F Q U A T I R N A R Y S C I I N C I ] H o l o c e n e p a r t i s a n u n p u [ : r l i s h e c . l ( . u r v e c o n s t r u c . t c d b y l . L .
K r i s t i a n s c n . r n d J . M a n g e r u d . T h t : l o c i t t i o n o i t h e b a s i n s a r c s h o w n i n F i g , . 5 .
T h e c u r v e s h o w s a f a s t e ' n r c r g t ' n c e i m m e d i . r t e l y : r f t e r d e g l a c i - : r t i o n , a p p r r o x i n r a t e l y 1 2 4 0 0 - 1 2 . 1 0 0 B P , a n d a m a r k c d l y c 1 c - c e l e r a t i n g r a t e to t h e e n d o f t h c Y o u n g e r D r y a s . A t t h a t t i m e a c l r a n r a t i c i n c r e a s e i n t h e r . r t e ( ) l e n t c r g r ' n c e t . r c c u r r c c l .
The l-lolocene part of thc c'urve is basecl on the stratig,raphy irr l a k e K l i n g r e v a t n ( 5 . 5 m : r . s . l . ) , w h c r c a c o m p l e t e s e c l u e n c e w i t h t w o n r a r i n e f o r n r . r t i o n s w a s i o u n r l (F i g . 7 1 . T h e a g t t o f t h e l o w e r L r o u n d a r y i s o n e e x a n r p l e r v h e r e th c r a d i o c a r b o n d a t e ( 9 7 1 0 y r : a r s B P ) is d i s c . a r t . l e d , b e c a u s e j u s t a b o v e it i s t h e P i n u - s r i s e in t h e p o l l e n d i a g r a m , a n c l th . r t ri s e is d a t e d to B 9 0 f ) B P i n o t h e r b . r s i n s ( K r i s t i a n s e n e t a l . , 1 9 8 7 ) . lh e r e g r e s s i o n m i n i m u m i s fronr Hafsten 11979). The rlate he obt.rined for ;i terrerstrial peat j u s t b e k r w t h e p r e s c n t s e a l e v e l ( 8 2 5 0 + 2 5 0 , T - 2 9 3 ) i s c o n r p a t i b l e r , v i t h t h e o t h e r d a t e s ( F i g . U ) . T h e e a r l y m a x i m u m o i t h c T i , r p c s t r a n s g r e s s i o n i s o b t a i n e d f r o n r la k c E n r j r e v a t n ( 1 3 m a . s . l . ) , w h e r e th e l r a s e o i t h e l a c u s t r i n e s e c l i m e n t s w ; t s c l a t e d k r 7 1 9 0 + 9 0 B P ( T - 4 ' l 6 2 A ) . l n l h i s l a k e e r o s i o n d u r i n g t h e t r a n s g r e s s i o n h a r l re m o v c c l t h e o l d e r H o l o c c n e s e d i m e n t s . N o t t t t h a t th e c u r v c fo r t h e p e r i o c l a i t e r 7 0 0 0 B P is lt a s c r l o n o n e s i n g l e d a t e fr o n r la k e K l i n g r e v a t n .
Step 4. Sea-level curve for Leinoy
T h e c u r v e ( F i g . B ) f o r L e i n o y (F i g . 5 ) i s f r o m S v e n d s e n ( 1 9 8 5 ) , a n d t h e c l o c u n r c n t a t i o n w i l l b e p u b l i s h e d i n a l a t e r p a p e r . T h e c u r v e s h o w s : r r a p i c l r e g r e s s i o n f o l l o w i n g d e g l a c i a t i o n a t a p p r o x i m a t e l y 1 2 6 0 0 y t : a r s B P . F r o m t h e l a t e A l l c r o d a n d d u r i n g t h e Y o u n g e r r D r y a s a p r o l o n g e d s t a n d s t i l l i s d e m o n - s t r a t e d . T h i s s t a n c l s t i l l i s r e c o r d e d in F r o v s t a d n r v r : r I w h e r e a l o n g - l a s t i n g b r . l c k i s h e n v i r o n m e r n t p r e v a i l e d f o r s e v e r a l h u n - c l r e r c l y e a r s p r i o r to t h e i s o l a t i o n . A s a t S u l a , t h e r a p i d H o l o c e n e c m e r g e n c e w h i c h s t a r t e d b y a r o u n d 1 0 3 0 0 y e a r s B P is c o n t e m - p o r . r n e o u s w i t h t h e c l e p o s i t i o n o f t h e H . r t l e n F o r m a t i o n . T h e
s t r a t i g r a p h i c . s u c c . e s s i o n s i n t w o o f t h e l r a s i n s s h o r v th l t t h e T.rpes tr.rnsgression, w,hich has not lrt:r'n daterl, re:ichecl a s l i g h t l y h i g h e r a l t i t u d e t h a n t h e Y o u n g e r L ) r y a s s c i , r l c v e l .
Step 5. Sea-level curve for Stette
T h e s e a - l e v e l c u r v e ( F i g . B ) w a s ( o n s t r u c t e d f r o n r t h e s t r a t i - g r . r p h i c c l e t a i l s r e c o r r l e r l f o r f o u r b . r s i n s ( F i g s 5 a n d / ) . T h e t h r e s h o l d e l e v a t i o n s f o r l a k e . L i l l c r c s l j o n n ( 4 , 1 - , 1 5 n r a . s . l . ) a n c l l a k e S l e t t e b a k k t j o n n ( . 1 4 . 5 n r a . s . l . ) w e r e c o r r c c t e c l t o t h e r i s o b a s e t h r o u g h t h e l a k e s S t e t t c ' t j o n n ( 4 ( 1 . 9 m a . s . l . ) a n d N o r e t - l a n n ( , . \ 7 . 9 n r . r . s . l . ) , b y u s i n g th e Y o u n g e r D r y a s s h o r e l i n e g r a d i e n t o f l . 3 m / k n r . T h c e l e v a t i o n o f t h e m a r i n e l i m i t i s r l e t e r m i n c c l l . r o m g l a c i o - f l u v i a l d e l t a te r r a c e s ( [ 1 e n n i n g s e n a n d l l o v d e n , . 1
9 U 4 ) . T h e e l e v a t i o n o f t h e ' n r ; r r i n e l i m i t s u g g e s t s t h a t t h c - a r e a lv a s c l e g l a c . i . r t c d a p p r o x i m a t e l y a t t h e s a m c ' t t m e a s S u l a , . r b o r - r t 1 2 3 ( X ) 1 2 5 0 0 B P , e v e n t h o u g h i t p h y s i c a l l y h a c l t o o c c u r s l i g h t l y l a t e r b e c a u s r : S t c t t e i s s i t u a t e c l i n l a n c l f r o n r S u l a . F o r th e c u r v e w e h a v e p l o t t c c l c l c g l a t i . r t i o n a t 1 2 , 1 0 0 B P .
Step 6. Late Weichselian shoreline diagram for Sunnmore
T h e c l i a g r a m f o r S u n n m o r e (F i t j . 9 ) w . r s c o n s t r u c t e c l i n t h e f o l l o l v i n g w a y . F r o m t h e s e a - l e v e l c . u r v e s ( F i g . 8 ) f o r L e i n o y , S u l a a n c l S t e t t e th e e l e v a t i o n s o f t h e s h o r e l i n e s f o r 1 2 4 O 0 ,
1 2 0 0 0 , 1 1 0 0 0 , a n d . 1
0 3 0 0 B P w e r e a b s t r a c t e d a n c l p r o j e c t e d a l o n g t h e i s o b a s e s i n t o t h e p r o j e c . t i o n p l a n e f o r t h e s h o r e l i n e c l i a g r a m i o r S u n n n r t r e ( F i g . - 5 ) . I n t h i s d i a g r a m s t r i i i g h t l i n e s a r e dr:iwn as the best fit between the thrr:e points for each age. As is a p p a r e n t f r o m F i g . 9 , v e r y g o o d f i t s h a v e b e e n o b t a i n e c l . T h c 1 0 3 0 0 B P li n e n e a r l y c o i n c i d e s w i t h a l i n e t h r o u g h t h e c l i s t i n c t n r o r p h o l o g i c . a l t e r r a c e s ( R e i t e , I 9 6 8 ; L i c e t a l . , 1 9 8 . 3 ) b e l o n g i n g t o t h e M a i n L i n e .
LEGEND: 6\ prominent beach ridge at the marhe limit
A g e o f l i n e s
1
103 years B.P.
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U) F i g u r e 9 A L a t e W e i r h s e l i a n s h < . r r e l i n e d i a g r a n r f o r S u n n m o r e {F i g . 5 ) . T h e s h o r e l i n e s w e r e d r a w n a s t h e f r e s t - f i t b e t w e e n th e s e a - l e v e l c u r v e s fo r L e r n o y , S u l a a n d S t e t t e ( v e r t i c a l li n e s ) . T h e s e a - l e v e l s r e a d o f f f r o m t h c c u r v e s f c . r r ' l 0 3 0 0 , 1 1 0 0 0 , 1 2 ( 1 0 0 a n d 1 2 4 0 0 B [ ' : r r e m a r k e d b y d o t s .
L A T L \' \ ' L I C I ] S I I I A N A N D I ] O t O C - F N I S I A - I I V I I H I S T O R Y I O R A ( R O S S S t ( - T I O N
( ) F W t : S l t, R N N ( ) R W A Y l ) 1
D u r i n g p c r i o d s o f r ; i p i c l c m c r l l e n c c , a s m a l l e r r o r i n . r g e c l e t e r m i n a t i o n s w i l l c a u s e a l . r r g e e r r o r i n t h e r e a d i n g o f e l e v . r t i o n f r o m t h c s e a - l c v c l c u r v c . T h e r e f o r e , t h e 1 2 4 0 0 a n d 1 2 0 ( X ) B P li n e s a r e c o n s i r j e r e r l m o r e u n c e r t a i n t h a n th e I I 0 0 0 a n c l 1 0 . 1 0 0 B P l i n e s .
T h e r l i a g r a m s h o w s t h : r t t h e n r a r i n e l i m i t o n V i g r ; r , V a l d e r o y a a n d C o c l o y ( F i g . 5 ) i s .r b o u t 1 0 - l 2 m a b o v e t h e 1 2 4 0 0 B P li n e . T h e a g e o f t h i s le v e l is u n k n o l v n , b u t a c c o r d i n g k r t h e c u r v c fo r L e i n o y ( F i g . t | ) it i s o l d e r th a n 1 2 6 0 0 B P . B y a s s u m i n g a s i m i l a r r e g r e s s i o n r a t e to t h a t b e t w e e n . 1
2 4 ( X ) a n d 1 2 0 0 0 y e a r s B P a t e n t . r t i v c . r g e o i . r b o u t 1 2 1 i 0 0 y c a r s B P is p r o p o s e d . H o w e v e r , i t i s s t i l l a n u n s o l v e d p r o b l e m . r s t o w h e t h e r th e n r . r r i n e l i m i t o n these outer islancls was formed at the start of a regrersir.,n, .r s t a n d s t i l l o r a t t h e e n d o f : r t r . r n s g r e s s i o n . T h e n r a r i n e l i m i t o n t h c s c i s l a n d s is r c p r c s c n t e d L r y p r o m i n e n t b e a c h r i d g e s a n d l e r r i l c e s ( R e i t e , 1 U 6 { l ; C r e v e , 1 9 t } , 1 ; L a n d v i k , 1 9 8 2 ) . B e a c . h r i d g e s o f a c o m p a r a b l e s i z c h a v c n o t b e e n fo u n d e l s e w h e r e i n t h i s a r e a , e x c e p t f o r a t t h e l e v e l o f t h e T a p e s t r a n s g r e s s i o n . W e q u e s t i o n w h e t h e r t h e n r . r r i n e l i r n i t o n t h c w e s t e r n i s l a n d s m i g h t h a v e b e e n fo r n r e d r l u r i n g s u c h a t r a n s g r e s s i o n .
Step 7. Extension and modification of the Late Weichselian diagram based on data from Sor-Trondelag
I n t h i s s t e p t h c L . i t c W e i c h s e l i a n c l i a g r a n r f o r S u n n n r o r e i s p r o i e c t r : d i n t o t h e p r o j e c t i o n p l . r n c fo r t h e S o r T r r r n d e l a g ( a n d t h c c o n r p o s i t e ) c l i a g r . r n r ( F i g . 2 ) , a n c l th c - S u n n n r t r e s h o r e l i n e s art'cxtrapolated t:astw,arrl ancl acljustcd in rel.rtion to the curves f r o m S o r - T r o n c l c ' l a g ( F r o s t a ; K j e m l r e r u c l , 1 9 t ) | ; B i u g n , H i t r a a n d F r o y . r ; K j c n r p c r u r l , I 9 t i 2 , 1 9 8 6 ) . T h i s w , a s d o n e in t h e fo l l o w i n g w a y : t h e m o r p h o l o g i c a l l y r l i s t i n c t M a i n L i n e ( i r o m K j e n s t a c l , 1 9 8 0 ) lv h i c . h i n S u n n m o r e w a s d c m o n s t r a t e d t o b e i d e n t i c a l t o t h c I 0 . 1 0 0 B P l i n c r v a s d r a w n in b o t h c l i a g r . r n r s . T h is li n e is w e l l c s t a b l i s h e d i n S u n n m o r e a n d S o r - T r r . l n c i e l a e a t t h e 4 0 m i s o b a s e a n d f o r t h i s r e a s o n th e t w o c . l r a s r a m s w e r e c o m b i n e d a t t h a t l e v e l , k e e p i n g a n u n b r o k e n M a i n L i n e . T h e e l e v i i t i o n o f l h e s h o r e l i n c s i n S o r - [ r o n d e l a g w e r e r e a d f r o m t h e c u r v e s in t h e s a m e w . r y a s i n S u n n m o r e ( S t c p 6 ) , a n d p l o t t e d in t o t h e n e w s h o r e l i n e c l i a s r a m .
T h e s e a - l e v e l d a t e s f r o n r S o r - T r r . l n d e l a e a r e in c o n s i s t c n t w i t h a r e c t i l i n e a r e x t r . , r p o l a t i o n o f b o t h t h e M a i n L i n e a n d t h e o l d e r s h o r e l i n e s t o t h e e a s t o f t h e d i a g r a m f o r S u n n m o r e . H o w e v e r , if a s l i e h t c o n c i : r v e ( . u r v a t u r e o f t h e M a i n L i n e is c o n s i d e r e d t o b e s i g n i f ic a n t a n d th e o l d e r s h o r e l i n e s a r e a l s o d r a w n w i t h a s i n r i l a r c u r v a t u r e , th e n m o s t o f t h e s e a - l e v e l d a t a f i t i n t o t h e n e w d i a g r a m . T h e r e a r e t w o p i e c e s o f e v i c l e n c e t h a t c o n t r a d i c t t h i s c . o n f i s u r a t i o n .
F i r s t , t h c s c a - l e v e l c u r v e fr o m B i u g n ( F i g . 1 0 ) s u g g e s t s t h a t th e 1 0 3 0 0 B P s h o r e l i n e i s . l
1 5 - 1 1 7 m a . s . l . w h e r e a s , a c c o r d i n g t o o u r f i n a l d i a g r a m ( F i g . 1 1 ) , a n d a l s o t o S o l l i d a n d K j e n s t a d ( 1 9 U 0 ) , i t i s a b o u t ' l 0 5
m a . s . l . T h e B j u g n c u r v e s h o w s a l n r o s t n t r e m c r g e n ( - e l r e t w e e n 1 1 5 0 0 a n d 1 0 3 0 0 B P , w h e r e a s o u r d i a g r a m s u g g e s t s a n e m e r g e n c e o f l 0 n r d u r i n g th a t p e r i o d . In o u r o p i n i o n th e d i s c r e p a n c y i s d u e t o a n e r r o r in t h e B ju g n c u r v e t h a t i s d i s c u s s e c l i n m o r e d e t a i l in s t e p 1 4 .
S e c o n d , a t H i t r a ( F i S . 1 0 ) K j e m p e r u d 0 9 8 2 , 1 9 8 6 ) d r e w a c u r v e s h o w i n g a n e a r s t a n d s t i l l f r o m 1 2 5 0 0 t o 1 2 0 0 0 B P , w h i c h m e a n s t h . r t t h e t w o s h o r e l i n e s o f t h a t a g e s h o u l d c o i n c i d e . H o w e v e r , in t h e e x t r a p o l a t e d S u n n m o r e d i a g r a m t h e 1 2 4 0 0 B P l i n e i s 1 5 m h i e h e r th a n t h e 1 2 0 0 0 B P l i n e a t H i t r a . T h i s d i s c r e p a n c y m a y b e r e a l , b u t t h e d a t a f r o m H i t r a m a y a l s o b e i n t e r p r e t e d a s b e i n g c o m p a t i b l e w i t h t h e d i a g r a m . T h i s w i l l b e
c l i s c u s s e c l i n n r o r t : d c t a i l in t h r : tc s t i n g o f t h e f i n a l c . l i . r g r a m ( s t c p t ' 1 ) .
T h e c o n c I u s i o n . r t t h is p o i n t i s th a t th c e r x t r a p o l a t e c l S u n n m o r c d i . r g r a m g i v e s a r e a s o n a b l y c o r r e c t p i c t u r e o f t h e s e a - l e v e l h i s t o r y i n S o r - T r r . r n d e l . r g .
Step B. Sea-level curves from Sgr-Trondelag
F r o n r S o r - T r r r n c l e l a g K je n t l t e r u d ( l 9 B 1 , 1 9 8 2 , 1 9 8 ( r ) c o n - s t r l r c t ( ' c l s c . r - l e v c l c u r v c s f o r F r o s t a , B j u g n , H i t r . r , a n c . l F r o y a ( F i g . 2 ) . T h e c u r v e s fo r F r o s t a a n c l B j u g n ( F i g . 1 0 ) a r e w e l l
cst:rblished ls thev are basecl on m.rny racliocarbon dates,
l v h r : r e a s l h c c u r v c s f r o n r F r o y a a n d [ ] i t r a ( F i g . l0 ) a r c b i l s e d o n icrver rlates. Note tl'rat Kjemperud used calendar ye:irs for the l a s t / 0 0 0 y e . r r s w h e r e c o r r e c t i o n o I r a d i o c a r b , - r n y c a r s r : p o s s i b l e . W e h a v e o n r i t t e r l t h a t c o r r e c t i o n , s o t h a t a l l d a t e s a n d t i m e - s c . r l c s i n t h i s p a p e r a r e g i v e n in c o n v r : n t i o n a l r a d i o c a r L r o n ye.r rs.
Step 9. Holocene shoreline diagram for Sar- Trondelag
F r o m h i s d a t a in S o r - T r o n d e l a g K j e m p e r u d ( . 1 9 8 6 ) c o n s t r u c t e d a s h o r e l i n e d i a g r a n r , m o r e o r l e s s i n t h e w a y d e s c r i b e d i n s t e p 6 . T h e r e is o n e m a j o r d i f f e r e n c . e . K j e m p e r u d a p p a r e n t l y u s e d th e i n d i v i d u a l ra d i o c a r b o n d a t e s fo r t h e i s o l a t i o n o f e a c h b a s i n ,
whereas we arsue that each sea-level curve is the best fit tcr
several dates from several basins. We consider the ages read off f r o m t h e c u r v e s t o b e m o r e p r e c i s e a n d r e l i a b l e th a n t h e i n d i v i d u a l d a t e s . A t s o m e p o i n t s , K j e m p e r u d ' s s h o r e l i n e d i a - gram cloes not correspond to his own sea-level curves. He also p o i n t s o u t t h a t d i f f e r e n t s o l u t i o n s m a y b e g i v e n fo r th e o l d e r p a r t on the basis of the oresent data. We therefore retained the Late W e i c h s e l i a n s h o r e l i n e d i a g r a m e x t r a p o l a t e d f r o m S u n n m o r e ( s t e p 7 ) , a n d c o n s t r u c t e d a n e w H o l o c e n e d i a g r a m , u s i n g K j e m p e r u d ' s d a t a , b u t f o l l o w i n g t h e p r o c e d u r e d e s c r i b e d i n s t e p 6 . T h i s d i a g r a m i s n o t m u c h d i f f e r e n t f r o m th e fi n a l o n e ( F i g . 1 1), and is therefore not presented here.
Step 10. Modification of the shoreline diagram based on data from Sunnmgre
I n s t e p 1 0 t h e d i a g r a m f o r S o r - T r s n d e l a g i s e x t e n d e d t o t h e w e s t a n d m o d i f i e d r e l a t i v e t o t h e s e a - l e v e l c u r v e f o r S u l a ( F i g . B ) , w h i c h i s t h e o n l y H o l o c e n e c u r v e f r o m S u n n m o r e th a t i s r e a s o n a b l y w e l l e s t a b l i s h e d . T h e d i a g r a m w a s o n l y s l i g h t l y m o d i f i e d , s u p p o r t i n g t h e a s s u m p t i o n t h a t t h e i s o b a s e s a r e n e a r l y p a r a l l e l th r o u g h o u t th e p o s t g l a c i a l p e r i o d . A f u r t h e r discussion of the correspondence between the data from S o r - T r o n d e l a g a n d S u n n m o r e i s l e f t to s t e p 1 4 .
Step 11. A composite shoreline diagram
T h e L a t e W e i c h s e l i a n (s t e p 7 ) a n d t h e H o l o c e n e ( s t e p 1 0 ) d i a g r a m a r e c o m b i n e d in t h e w a y d e s c r i b e d i n s t e p 7 . T h i s m a y
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F i g u r e 1 0 S e a - l e v c l c u r v c s i o r V e r d a l s o r a ( S v e i a n a n r l ( ) l s e n , 1 9 8 ' 1 ) , F r o s t a { K j e m p e r u d , i 9 U l ) , t 3 i u g n , l l i t r . r a n c l F r o y a ( K y e n r p e r L r d , I 9 U 2 , 1 9 8 6 ) in S o r - T r o n c l e l a g ( F i g . 2 ) . T h e s o l i c l l i n e s s h o w , t h e e n r p i r i c a l ( ( r r v e s , l \ r l r a l v n b y t h c . t u t h o r s . T h e r r : r v e s r l e r i v e r l f r o n r t h c s h o r c l i n e c l i . r g r . r m ( F i g . l 1 ) . r r c c l a s h e c l w h e r c t h e l ' c l c ' v i . r t e f r o m t h e e n r l r i r i c . r l c u r v c s . N o t c t h . r t th e c u r v e r o n s t r u c t e r l b v S v c i a n a n d O l s e n ( 1 9 t i . 1 1 f o r V c r r l a l s o r a i s n r a i n l v b a s e c l o n m c r l l u s c s o t c u r r i n g in n r a r i n e t c r r . r c c s w h i l e t h e o t h e r s . r r e b . r s c c l o n t h e s t r a t i g r a p h v o f e n r e r g e c l b a s r n s .
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