The Holocene 11,3 (2001) pp. 323-331 Holocene sea-level variation and spit development: data from Skagen Odde, Denmark Lars B. Clemmensen, Niels Richardt and Christian Andersen (Geological Institute, University of Copenhagen, 0ster Voldgade 10, DK-1350 Copenhagen K, Denmark) Received 13 February 2000: revised maniuscript accepted 10 Septemiiber 2000 HOLOCENE RESEARCH PAPER Abstract: Extensivxe exposLures of peat located in initer-ridge swales, at the contact between beach anid oxerlyiing coastal dune deposits at Skagen Odde. northern Denmark, provide a record of spit development in relation to glacioisostatic rebound and sea-level variation. The elevationi of the base of the swale peats was measured over a distanlce of l5 kmni anid rcpresenits spit gosowth bet-Necen '6000 and 1400 cal. veairs BP. Tlle swale pealts fall from 13-14 m a.s.l. in the south (proximiial part) to 3-4 m a.s.l. in the north (distal part) reflecting the inifluenice of 'sostatic rebounid dLiting spit gTowsth. The nesw data suggest that isostatic rebound progressively declined with time fromi c. 3 mm yr' to c. 1.5 mm yr'. Superimposed on the isostatic controlled changes are smaller-scale fluctLations in peat elevation related to eustatic sea-level changes. Sea-level higlhstands ae iden1 t ified at 5450 (+2.7 in). 4700 (+1.7 m) and 2450 cal. years BP (+0.4 m). anid lowstands at 5200 (+1.5 m). 4100 (-1.9 mn) anid 1650i cal. years B3 (40.6 m). A final comilponiient that contributes to variatiotis in peat lexattion is local topoarcap1iv and at a few places pcat drapes across stiaal icoli clLidns. Tlin agc nilO indicates eat the spit-groxthi tiate varied betwveen 2 anid moi-e tlhani 10 mi sr-'. Thlse variations in growtlh rate may patily t-ecord sea level controlled flUCctLationis in the suLpply of sanid fromi erodini g clifts onl the west coast of niorth- ern Juitlarid. Key words: Sea-level variation, isostasy. spit clevelopinent, ridge-anid-swale comiplex. Deniltark, Holoceite. Introduction The sedimentarv deposits of the coastal lowlands in northern Etr- ope contain inmportant information on the interplay between Holo- cene sea-lexvel variation and isostatic movement (e.g., MWrner, 1980: Sheninani. 1989a 1989b Lambeck, 1991 Long and Tooley, 1995 Dawson and Smith, 1997 Lanmbeck et al., 1998). However. apart from the classic work of Morner (1980), the late-Holocene (post 5000-BP) sea-level hiistory of the region is only frag- mentarily documented. One of the Imlost impressive Holocene coastal sedimentary sys- tems in the region is Skagen Odde in northern Jutland, Denmark, which has a length of 35 km and forms one of the largest spits in northern Europe (Figures 1 and 2). The age and development of this paraglacial spit were first documented by Jessen (1899). Since then works by Jessen (1936), Schou (1949), Petersen (1991), Hauerbach (1992), Tanner (1993), Conradsen and Heier- Nielsen (1995), Jiang et al. (1997) and Johannesen and Nielsen (1999) have added considerably to our knowledge of this Holo- cene spit system and its palaeoclimatic and palaeoceanographic setting. The growth of Skagen Odde since about 8000 cal. years BP (Petersen, 1991) took place over a period that saw a large isostatic Arnold 2001 WI,ge5 0 5 10 km lojeni kagn Skagerrak 1 Kandesedertle *2 / ~~Kattegat ag/ ? X-i ~~~~Alb,ek Tverst.ed CO Jerup Skagen JUTLAND Hirtshals.,, OH olocene deposits [7 Weichselian deposits Figure 1 The Skagen Odde, northern Jutland, Denmark. The investigated coastal stretch on the northwestem side of the spit is indicated. The spit is still growing towards the northeast by the formation of new ridge-and- swale deposits. 0959-6836(01)HL468RP i, * , .,�� -, ..................................... �� 2001 SAGE Publications. All rights reserved. Not for commercial use or unauthorized distribution. at Copenhagen University Library on June 10, 2008 http://hol.sagepub.com Downloaded from

324 The Holocene 11 (2001) Figure 2 Air photo of the northwestern part of Skageni Odde at Kandestedeme. Note the curved rige-and-swale comiiplex truncated by coastal erosion (swales appear as darker areas). Spit growthl was towards the northeast. Owing to isostatic uplift simultaneous with spit growtth the swale peats (Martoi v) now occtur 6-10 m a.s:l. with the highest-lying swale deposits toward the souLthwest. rebound (Petersen, 1991 Tanner, 1993), and spit development is recoided by raised beach ridge-and-swale systems. The sanidy or pebbly beach ridges are separated by sssvales that are peat-filled linear depressions (Figure 2). The nature and origin of the ridge- and-swale systems (rinmne-doppe systems in Danish) were first described by Jessen (1899 1936). These ridge-and-swale deposits are veiv well exposed in erosional sections on the niorthwestern slhore of the spit, and the swale peats (the so-calledl vIartori' Pet- ersen. 1991 Cleimienseni and Andeiesen. 1998) form dlisci-ete sedi- menit bodies at the conitact betsseen marinie anid ox erlving coastal d:une (leposits (Figure 3). A number of previous studies of Skagen Odde lhave foctLised on the relaltions between Holocene spit development, sea-level vari- ation and isostatic rebound. Tanner (1993) constructed a detailed Holocene sea-level graph for the area on the basis of grain-size analysis of beach-ridge deposits on the southeastern side of the spit. Unfortunately these beach ridges were only dated indirectly and it was assutmed that the accretion rate in the area was constant. Petersen (1991) aimd Hlauerbacih (1992)3 nmeisured the elevation of the top suirface of nine beaclh ridges expose(I on the northlMestern slhor-e of the spit and radiocarbon dated the associated svdIle peolts. Tail mer (199' ) used these data on beacll ridges to costnmlctlal Figure 3 Stratigraphy of the spit deposits 3.4 km north of Kandestedeme. Swale peat (Martorv) preserved at the contact between underlying beach and associated aeolian dune deposits and overlying young coastal dune deposits. The peat has a thickness of c. 0.8 m in the swale, but is relatively thin on top of the small aeolian dune. The existence of older aeolian deposits at this locality is unusual and may record a period of increased aeolian activity at about 4100 BP. .7=7' 00 �� 2001 SAGE Publications. All rights reserved. Not for commercial use or unauthorized distribution. at Copenhagen University Library on June 10, 2008 http://hol.sagepub.com Downloaded from