Paleoenvironment and Shore Displacement Since 3200 BC in the Central Part of the Långhundraleden Trail, SE Uppland

Department of Physical Geography and Quaternary Geology

Paleoenvironment and shore displacement since 3200 BC in the central part of the Långhundraleden Trail, SE Uppland

Christos Katrantsiotis

Master’s thesis NKA 70 Physical Geography and Quaternary Geology, 45 2013 Credits

Preface

This Master’s thesis is Christos Katrantsiotis degree project in Physical Geography and Quaternary Geology at the Department of Physical Geography and Quaternary Geology, Stockholm University. The Master’s thesis comprises 45 credits (one and a half term of full- time studies).

Supervisor has been Jan Risberg at the Department of Physical Geography and Quaternary Geology, Stockholm University. Examiner has been Stefan Wastegård at the Department of Physical Geography and Quaternary Geology, Stockholm University.

The author is responsible for the contents of this thesis.

Stockholm, 4 March 2013

Lars-Ove Westerberg Director of studies

Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

Abstract In this study, litho-, bio- and chronostratigraphic investigations combined with RTK GPS leveling have been carried out to reconstruct the paleoenvironment in the central part of the Långhundraleden Trail. The area displays four shallow lake basins of varying morphologies. The basins are now covered with peat as a result of infilling and overgrowth. The emergence of the saddle-point, i.e. the highest point of the underlying minerogenic surface, was estimated to have occurred c. BC/AD. The isolation events of two basins, at c.12.4 and c.12.3 m a.s.l. west and east of the saddle-point, were dated to c.AD 20 and c.AD 30, respectively. By combining these isolation data with six previously investigated basins a shore displacement curve for the central part of the Långhundraleden Trail and the surrounding area, i.e. east of the Ekoln basin was constructed. The curve indicates an average regressive shore displacement rate of c.6.2 mm/yr since c. 3200 BC. Around 1500 BC, this trend was interrupted by a short period of retarded regression, correlated with the L4 event. The isolation ages of the basins in the Långhundraleden Trail appears relatively young when compared to an average shore displacement rate of 5.6 mm/year in the northern part of L. Mälaren, west of the Ekoln basin. As the area is dominated by a fissure- valley landscape, this discrepancy could be attributed to small-scale irregular tectonic movements, which caused faster uplift rate, i.e. 6.2 mm/year, east of the Ekoln basin.

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2 Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

Table of Contents

1) Introduction ...... 5 2) Background ...... 7 2.1) Uppland county ...... 7 2.1.1) Geological settings ...... 7 2.1.2) The Weichselian glaciation, deglaciation and sediment regimes ...... 8 2.1.3) Shore displacement ...... 10 2.1.4) Isostatic variability ...... 12 3) The Långhundraleden Trail ...... 14 3.1) Location and general description ...... 14 3.2) Geological description ...... 15 3.3) Landscape development ...... 15 4) Description of the study site ...... 18 5) Methods...... 20 5.1) Field work ...... 20 5.1.1) Stratigraphical coring and sampling ...... 20 5.1.2) Leveling ...... 20 5.2) Laboratory method ...... 21 5.2.1) Loss on ignition ...... 21 5.2.2) Diatom analysis ...... 21 5.2.3) Radiocarbon dating ...... 22 6) Results and interpretation ...... 23 6.1) Lithostratigraphy ...... 23 6.2) Leveling and morphology ...... 32 6.3) Description of sampling sites for laboratory analyses ...... 34 6.3.1) Basin A...... 35 6.3.1.1) Age-depth model ...... 36 6.3.1.2) Loss on ignition ...... 38 6.3.1.3) Diatom analysis ...... 38 6.3.2) Basin B ...... 44 6.3.2.1) Age-depth model ...... 46 6.3.2.2) Loss on ignition ...... 49 6.3.2.3) Diatom analysis ...... 49 6.4) Evolution of the area ...... 55 7) Discussion ...... 58 7.1) Location of sampling sites ...... 58 7.2) Determining isolation threshold elevation ...... 59 7.3) Geographical settings ...... 59 7.4) Defining the isolation event ...... 59 7.5) Diatom species distribution ...... 61 7.6) Diatom dissolution and preservation ...... 64 7.7) Radiocarbon ages ...... 65 7.8) Age difference between chironomids and plant macrofossils ...... 65 7.9) Shore displacement ...... 66 7.9.1) Description of sites ...... 66 7.9.2) Description of the shore displacement curve ...... 70 7.10) Isostatic variability ...... 75 8) Conclusions ...... 80 9) Acknowledgements ...... 81 10) References ...... 81 11) Appendix 1 Coordinates(X&Y), altitude (Z in m a.s.l.) and lithostratigraphy of coring sites ...... 91 12) Appendix 2: Ecological grouping of diatoms on the basis of salinity and habitat (Basin A & B) ……………….94

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4 Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

1. Introduction

The complex development of the Baltic basin since the last deglaciation has been controlled by a set of factors. These include the vertical movements of the earth’s crust, a process known as isostatic land uplift, in conjunction with eustatic variations, the varying depths and widths of the basins thresholds as well as the freshwater input from the melting of the Scandinavian Ice Sheet (Eronen 1974; Gudelis & Königsson 1979; Björck 1995, 2008; Lambeck 1999). These factors have triggered large variations in salinity and water level within the Baltic basin resulting in two alternating freshwater and brackish water stages i.e. Baltic Ice Lake, Yoldia Sea, Ancylus Lake and Littorina Sea (Björck 1995, 2008). The land uplift has been triggered by two mechanisms; the glacial rebound in response to the unloading of the Weichselian ice sheet and movements of tectonic plates (Mörner 1977, 1979). Eustatic sea level variations have been affected by climate changes and changes of the geoid (Mörner 1999; Björck 1995, 2008; Ekman 1996). The interaction between the land uplift, which has varied both in time and space, and the local water level variations within the Baltic basin, have resulted in a complicated pattern of shore displacement along the Baltic coast. In general, the shore displacement in the area north of southern Finland- Stockholm has been characterized by a rapid regression (Miller & Robertsson 1979; Lindén et al. 2006; Berglund 2012). In southern Sweden alternating regressive and transgressive phases, due to the reduction in the rate of isostatic uplift, took place (Berglund et al. 2005). These dynamics, in relation between eustasy and isostasy, have influenced the landscape development of Baltic coasts, the prehistoric habitation and location of settlements on the coastal areas.

Eastern–middle Sweden is an area where the framework of shore displacement studies with connection to archaeological research has a long tradition (e.g. Florin 1944; Ambrosiani 1981; Risberg et al. 1991). The pattern of the human habitation has been related to changing environmental conditions due to the migration of shorelines. Following the decay of the ice sheet, the glacio-isostatic uplift gradually exposed new pieces of land forming an archipelago with large islands and adjoining land areas. This landscape offered favorable conditions for colonization providing access to marine recourses and to the transportation and communication routes as early as c.7500 BC (e.g. Knutsson et al. 1999; Pettersson & Wikell 2006). The continuing uplift and consequent tilting of the land triggered the isolation of former straits, bays and inlets, which were later turned into lakes and wetlands. The uplifted land area sparked substantial impacts on human activities and the development of farming and societies. As former trade routes have been impeded human communities no longer had direct access to the sea and were forced to abandon settlements.

In the frame of the present study, focus is placed on environmental changes along the central part of the Långhundraleden Trail, south-eastern Uppland, east-central Sweden. The Långhundraleden Trail was one of the former water routes, which connected the Uppsala area with the Baltic Sea functioning as a thoroughfare until the Middle Ages (Eklund et al. 2011). The route was used as a mode of transportation even though the saddle-point had

5 Christos Katrantsiotis emerged from the sea leading to a gradual replacement of the brackish Baltic Sea water by freshwater in the route. The pattern of the drying up of the Långhundraleden Trail is not well-known since no studies have been conducted along the route. The nearest investigation is located east and north of Uppsala in connection with studies of shore displacement along the newly opened highway E4 (Risberg et al. 2005). The reconstruction of shore displacement history along the Långhundraleden Trail could be deduced from interpolations between empirical investigations from southern and northern Uppland. The non-uniform isostatic uplift, however, has resulted in the construction of several local shore displacement curves. This has complicated the precise dating of the isolation of basins along the route based on interpolations from the surrounding area. Therefore, due to large variation in the isostatic component, shore displacement studies ought to be performed on a relative local area to improve the accuracy.

This master thesis aims at scrutinizing the development of the central part of the Långhundraleden Trail based on stratigraphic studies of sediment cores, including lithostratigraphic interpretation, diatom analysis, loss on ignition, and radiocarbon dating. The specific objectives of this master thesis are to:

1. investigate the lithology along the central part of the route 2. describe the paleoenvironment east and west of the saddle-point 3. construct a shore displacement curve

6 Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

2. Background

2.1 Uppland County 2.1.1 Geological settings The county of Uppland is located at the south-eastern coast of Sweden (Figure 1). Uppland has been called the youngest county of Sweden. Due to the land uplift and the flat landscape large parts of the county have emerged from the sea after 2000 BC.

Figure 1: (A) Maps showing the present Baltic Sea and (B) the location of Uppland. Blue line shows the position of the Långhundraleden Trail.

The bedrock is made up of granites, gneisses, and acid volcanic rocks belonging to the subcambrian peneplain, which was formed during the Svecofennian orogenic activity between 1900–1750 Ma years ago (Lundqvist & Lundegårdh 1956; Stålhös 1972; Lidmar- Bergström 1995). The structural pattern of the bedrock is a result of two deformation phases (Stålhös 1976). The older deformation, caused by east-west stress, overturned the strata to the west. A younger deformation phase, triggered by a north-south compression, generated an easterly plunging lineation. Tectonic movements and erosion have transformed the bedrock resulting in down-faulted lowland with small parts of the province elevating more than 50 m a.s.l. The highest point lies in the western part of Uppland, reaching 117.6 m a.s.l. (Agrell & Mikko 2003; Karlsson 2007). The southern part of the province, i.e. south of Uppsala, is characterized by deep fissure valleys and fault fissures, which run in north–south, east–west and northwest–southeast direction (Lidmar-Bergström 1995; Karlsson 2007). The highest area in southern Uppland reaches c. 35 m a.s.l. Northern Uppland consists of a flat peneplain, which dips gently towards the east, with small variations in topography and the most elevated parts reaching 30 m a.s.l (Lidmar-Bergström 1995; Hedenström & Risberg 2003).

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2.1.2 The Weichselian glaciation, deglaciation and sediment regimes The geological history of Uppland includes several periods of total glaciation and deglaciation. The successive advance and retreat of the ice sheet has left profound imprints on the landscape. Traces of earlier glaciations have vanished due to the effect of younger glaciers, which eroded and removed most of the older deposits. Hence, most of the evidence remains of the youngest ice age called Weichselian glaciation, which ranged between 115 ─ 11.5 ka years ago (Lundqvist 2004; Lokrantz & Sohlenius 2006; Johnsen 2010). The Weichselian Ice Sheet was subject to fluctuations both in frequency and amplitude. The ice motion polished and scraped the bedrock surface producing glacial striae as well as a series of glacial landforms. Kleman et al. (1997) presented a geomorphology-driven reconstruction of the Weichselian Ice Sheet evolution. According to this reconstruction, Uppland was covered by the ice sheet between 65 ─ 12 ka years ago (Kleman et al. 1997; Lundqvist 2004). It is under discussion whether Uppland was free of ice sometime between 50 ─ 25 ka years ago. According to Lundqvist (1992), the main part of Fennoscandia was covered by ice throughout the Middle and Late Weichselian. Other researchers (e.g. Olsen et al. 1996; Ukkonen et al. 1999) suggested that large parts of Scandinavia were free of ice during the latter part of the Middle Weichselian.

Hättestrand (1998) carried out a mapping of the glacial morphology to reconstruct the pattern of the ice flow in central and northern Sweden. In Uppland, the glacial morphology record indicates two ice flow directions. The oldest set of glacial striae and lineations records an ice movement from NNW. The youngest lineations and recessional landforms show an ice flow from N and/or NNE. The latter represents the ice motion during the latest deglaciation (Hättestrand 1998).

Due to the pressure from the ice sheet, the bedrock was deeply depressed. For that reason, the whole province was situated below the highest water level developed after the deglaciation. The ice advance and retreat gave rise to deposits which covered the bedrock to a large extend. Glacial sediments were formed during the latest ice age and postglacial deposits accumulated thereafter. The deposits are to a large extent calcium rich since they have been influenced by the southwards transportation of Ordovician limestone from the Gulf of Gävle during the Weichselian Ice age (Ingmar & Moreborg 1976; Strömberg 1989). Glacial till, which mainly dominates higher elevations in the eastern as well as the north- western part of Uppland, was directly deposited by the glacier ice, containing all grain sizes from clay particles to large boulders. Till has been a result of glacial crushing of the Precambrian granitic bedrock. In some areas clayey till can be found as Ordovician limestone was crushed and mixed with other bedrock material (Ingmar & Moreborg 1976). During the deglaciation, melt water from the ice transported and deposited bedrock material in cracks and tunnels within the ice or at the ice margin. These deposits, referred to as glaciofluvial deposits, formed eskers of well-sorted sand, gravel and stones, which mainly stretches in N–S direction. The deglaciation left vast areas of small end moraines of De Geer type, especially in the eastern part of the county, with E-W orientation and glacial lineations, mostly as flutings (Hättestrand 1998).

8 Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

During the Yoldia Sea stage, clay and silt were suspended in the melt water and deposited on the bottom as varved glacial clay along the margin of the receding ice sheet. The brackish phase of the Yoldia Sea sometimes hampered the formation of varves because of the high levels of ions, which aggregated the clay fraction into coarse grains. Varves reflect the seasonal fluctuation of glacial melt water. During spring and summer coarser and lighter layers were accumulated whereas winter deposition was marked by dark thin layers of finer material.

Varved clays have been used as a chronological tool to reconstruct the deglaciation pattern along the eastern coast (De Geer 1940; Järnefors 1963; Strömberg 1989; Brunnberg 1995). The glacial varve record indicates that the ice front was situated south of Stockholm between 9500 and 9400 BC. The northern part of Uppland was deglaciated after Figure 2: Deglaciation pattern in eastern-middle Sweden 9000 BC (Figure 2; converted into BC ages (modified from Lundqvist 1994). The red Strömberg 1989; Lundqvist lines depict the ice margin. The arrows show the direction of 1994; Björck & Svensson glacial striae. Blue line represents the Långhundraleden Trail. 2002). The deglaciation maintained a pace of ~300 m annually. The ice recession lines, which express the successive position of the retreating glacier margin, generally show a WSW ─ ENE course (Lundqvist 1975; 1994).

The relief of pressure from the ice sheet sparked the onset of the glacial isostatic adjustment. As the water depth decreased, due to the land uplift, waves or sea floor currents eroded and reworked some of the older deposits. The material washed out from the uppermost parts of the till, e.g. sand and gravel, were redeposited at more sheltered positions stratigraphically above glacial clay. During the Ancylus Lake stage glacial clay was reworked from elevated areas, along with other fine-grained sediment, transported and redeposited in the deepest parts of sheltered bays in the form of non-varved postglacial clay. During the Littorina Sea stage, highly decomposed organic material, which emanates from algae and other vegetation in surrounding areas were washed along with clay and deposited above postglacial clay, as gyttja clay and clay gyttja. Owing to wave action, the flanks of eskers were often covered by wave washed sand and gravel deposits whereas

9 Christos Katrantsiotis shingle fields were formed on the surface from residual boulders and stones. Wave washing also resulted in the appearance of bedrock outcrops in higher areas.

As the land uplift proceeded, former bays and inlets located along the coastal areas were isolated from the sea and turned into freshwater lakes (Åse 1996). Enhanced inflow of organic material and high organic productivity led to the deposition of gyttja in areas where water turbulence was low. Low oxygen levels in bottom waters slowed down the degradation process of organic material, increasing the rate of accumulation, which was enhanced by the colonization of plants that reduced the bottom currents (Bergström 2001). The former isolated lake basins were converted into mires. The youngest accumulations are different types of peat, which cover large areas in northern Uppland, due to paludification and overgrowth of former lakes (Möller 1993; Rudmark 2000). Remnants of plants from the lake edges, dominated by reeds and sedges, fell into the water forming a thick layer of reed peat. In some areas, this succession of accumulation led to Sphagnum moss peat, which represents the final stage of an autonomous hydrological system fed by precipitation.

2.1.3 Shore displacement Numerous research projects have been conducted pertaining to the course of the shore displacement in different parts of Uppland based on both archaeological and geological data. The results have often been displayed as shore displacement curves, which are governed by eustatic sea level changes and glacio-isostatic land uplift (e.g. Åse 1970a, 1970b, 1980; Ambrosiani 1981; Miller & Robertsson 1981; Miller 1982; Åse & Bergström 1982; Miller & Hedin 1988; Robertsson & Persson 1989; Risberg et al. 1991; Karlsson & Risberg 1998; Risberg 1999; Mörner 1999; Bergström 2001; Hedenström 2001; Hedenström & Risberg 2003; Karlsson & Risberg 2005).

Following the ice retreat, Uppland was submerged and the Yoldia Sea water gradually inundated the isostatically depressed bedrock (Björck & Svensson 2002; Risberg & Alm 2011; Berglund 2012). The southeastern part of the province represented the lowest lying area. The crustal depression enabled the formation of deeply incised embayment at the regional highest shoreline, recorded at 160 m a.s.l. (Björck & Svensson2002). The Yoldia Sea was a short-lived stage as the shallower straits in south central Sweden, i.e. the Närke Strait, ended the saline influence and led to the Ancylus Lake stage around 8800 BC (Björck 1995, 2008). Simultaneously, glacio-isostatic uplift and thus regressive shore-level displacement rate was rapid. According to Risberg et al. (1991) during the Yoldia and Ancylus stages the shore displacement rate on the Södertörn peninsula was c. 25-30 mm/yr.

The rapid regression, which prevailed at the end of, and immediately after deglaciation, was interrupted by the onset of the Littorina Sea stage. This stage was associated with a global sea level rise triggered by the partial collapse of the Antarctic ice sheets during the warmest postglacial times of the Atlantic period or Postglacial Climatic Optimum (Emeis et al. 2002; Björck 2008). At the transition to the Littorina Sea there was a significant decrease in the regression rate (Risberg et al. 1991). The model for southern Uppland compiled by

10 Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

Karlsson & Risberg (2005) indicates irregular regressive shoreline displacement in amounts of 10 mm/year between 8000 and 2000 BC (Figure 3). Many studies conducted in southern Scandinavia indicate that the Littorina Sea stage was characterized by multiple eustatic transgressions (Christensen 1995; Andrén et al. 2000; Sandgren et al. 2004; Yu et al. 2004). Further north, due to the different isostatic uplift rate, shore displacement curves show regional differences regarding the number and the amplitudes of the transgression events (Åse & Bergström 1982; Hedenström & Risberg 2003).

Figure 3: Modified shore displacement for northern Uppland (Hedenström & Risberg 2003) and southern Uppland (Karlsson & Risberg 2005).

In the Stockholm region and the southern part of Uppland four transgression events have been recorded (Miller & Robertsson 1981; Miller 1982; Risberg et al. 1991; Karlsson & Risberg 2005). These phases are depicted in the shore displacement curves as a reduction in the regression rate or transgressive eustatic movements. According to the shore displacement model for southern Uppland the first phase (L1) occurred around 7500 BC, when the sea level rose rapidly exceeding the bedrock elevation rate (Figure 3). The second phase (L2) peaked around 5500 BC reaching a higher altitude than L1 event. After the end of the eustatic sea-level rise, the uplift was still going on resulting in a renewed regression (Björck 2008). The rate of this regression, however, was slower than that prior to the early Littorina Sea transgression (Risberg et al. 1991). This trend continued until c. 4500 BC. Two younger transgression phases (L3 & L4) were recorded between 4500–3000 BC and 3000─1500 BC (Miller & Robertsson 1981; Miller 1982; Karlsson & Risberg 2005).

Further north, the Littorina Sea transgressions were less noticeable since glacial isostatic rebound was faster than sea level rise (Hedenström & Risberg 2003). Some studies show

11 Christos Katrantsiotis that one or two transgressive phases reached central Uppland and the L. Mälaren-region (Miller 1982; Miller & Hedin 1988; Hedenström 2001). A preliminary shore displacement curve for the Uppsala area constructed by Åse & Bergström (1982) records two or three periods with a standstill or transgressive eustatic movements. These periods are well correlated in time with the younger Littorina Sea events (Åse & Bergström 1982). The presence of shorelines on the eskers and shores around L. Mälaren and the Ekoln basin are possibly connected to a halt in shore displacement following transgression/the isolation of L. Mälaren, or other processes e.g. storm surges (Åse & Bergström 1982, 1984; Åse 1996).

During the last c. 4000 the shore displacement in southern and northern Uppland years has been a stable, relatively parallel and gradually slowing down process as the eustatic rise of global sea level has ceased. Although the sea level has attained its present level, transgressions and regressions have occurred in the last millennia (Åse 1980). These events have been connected with regional wet and dry phases (Mörner 1999). For instance, a number of studies show the occurrence of a transgression period called Viking age around AD 800–1000 (Ambrosiani 1981, Miller 1982, Åse 1994; Mörner 1999; Risberg et al. 2002). According to Åse (1980), however, the sea level rise, which was caused by this event, should have been compensated for by the isostatic land uplift. Mörner (1999) showed the occurrence of three periods with rapid sea level regression in the Stockholm area (700 – 500 BC, AD 350 – 450 and AD 970 – 1050). The amplitude of these regressions was between 1.3 m and 1.6 m. Ekman (1999) stated that sea level changes, due to northern hemisphere climate variations, have not varied more than ±1.5 mm/year since AD 800.

2.1.4 Isostatic variability The variable isostatic uplift pattern, which has prevailed in Uppland and adjacent area, is revealed by the published isobases. De Geer (1925) proposed that the prevailing isobase system during the transition from the Ancylus Lake to the early Littorina Sea had an N-S direction (Risberg et al. 2005). According to Eronen’s model (1983) for the ancient shore lines of the earlier stage of the Littorina Sea, the direction of the isobases changed from north-south to northeast-southwest around 5500 BC. Risberg et al. (2005) proposed that a redirection of isostatic uplift pattern has taken place during the last 5000 years. Ekman (1996) reconstructed the recent postglacial rebound of Fennoscandia by using sea and lake level records as well as repeated leveling (Figure 4). The reconstructed map suggests that the overall east-west isobases for land uplift while the uplift is increasing towards the north in an amount of 1 mm/yr for every 50 km. The Ussisoo’s isobase system for the central part of Uppland shows more or less an NW-SE direction of the isobases around L. Mälaren indicating irregular isostatic uplift during the last centuries (Åse 1970a). Miller & Hedin (1988) traced variations in the pattern of the uplift for the Stockholm and adjacent area by comparing the distribution of the present uplift isobases with the direction of the isobases of the Littorina Limit (Figure 5). The map confirms that the isostatic uplift has change direction from northeast-southwest to east-west during the last 5000 years.

12 Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

Figure 4: Recent isobases in Fennoscandia constructed on the basis of leveling gravity and sea-

level data (in mm/year, adopted from Ekman 1996).

Figure 5: Present shore displacement

in comparison with the isobases of the Littorina Limit in Uppland (redrawn from Miller & Hedin 1988).

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3. The Långhundraleden Trail

3.1 Location and general description

Långhundraleden is a former water route located between the Baltic coast and Uppsala, in the south-eastern part of the Uppland county, east-central Sweden (Figure 6). The trail stretches from Åkersberga to Gamla Uppsala, via Össeby–Garn, Vada Frösunda, Närtuna, Gottröra, Husby-Långhundra, Östuna, Lagga and Danmark.

Figure 6: Map showing the position of the Långhundraleden Trail in the southeastern part of Uppland. The rectangle shows the studied section located in the central part of the trail between Gottröra and Husby-Långhundra.

The origin of the name Långhundraleden emanates from the elongated shape of the historic district, 'the lång/long (elongated) hundare/count', located along the trail (Gunilla Larsson pers. comm. 2012). The route is of national interest for the cultural heritage. Plenty of relics and monuments associated with the transportation, habitation and human activities in the region have been found adjacent to the trail stretching c. 4000 years back in time (Grönwall & Lilja 2004:5; Eklund et al. 2011). Owning to the isostatic land uplift, large parts of the trail have become almost dry with few remaining rivers and lakes. The water supply is dependent on precipitation and runoff from the surrounding area (Dahlbäck 2009). The land along the route is to a large extent cultivated with forested patches. The area is located within the boreo-nemoral forest zone. Spruce or deciduous trees are the predominant species (Karlsson 2010).

14 Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

3.2 Geological description The geology of the Långhundraleden Trail has been described in connection with the geological mapping of the area carried out by the Geological Survey of Sweden. The area is located within the geological map sheets: Uppsala (Lundqvist & Lundegårdh 1956), Stockholm NE (Möller & Stölhös 1964), Uppsala SW (Möller & Stölhös 1971), Uppsala SE (Möller & Stålhös 1974), Uppsala NW (Möller 1993) and Uppsala NE (Rudmark 2000).

The trail occupies a system of rift valleys formed by tectonic movements and erosion of the bedrock. These valleys are oriented in three main directions: north-south, northwest– southeast and east-west. The southern part of trail goes through a narrow rift valley with rocky precipice or steep valley sides. Northwards, the trail is expanded into a broad and flat plain surrounded by slightly elevated areas of till and bedrock.

The bedrock belongs to the uplifted subcambrian peneplain which, in this part of Uppland, consists of granites, gneisses and metamorphosed supracrustal rocks covered by scattered remnants of Paleozoic sedimentary rocks. Massifs of gabbros and diorites can be found in some areas. The main part of the bedrock is covered with Quaternary deposits. The thickness of the accumulations varies considerably. The upper parts of the deposits have been reworked by wave action, since the area lies below the highest post-glacial coastline, i.e. 150 m a.s.l. In general, coarse-grained deposits are widespread on elevated areas around the route whereas fine-grained material, such as glacial and post-glacial silt and clay, can be found in low-lying areas and depressions. The predominating glacial unit is sandy till, which lies on the Precambrian bedrock (Rudmark 2000; Karlsson 2007). Clayey sandy and gravelly to sandy till occur on the lee sides of bedrock outcrops in relation to the last ice movement (Möller & Stölhös 1964). At some places till contains sandstone and fractions of Ordovician limestone. The thickness of till is usually less than 5 m (Rudmark 2000). Glaciofluvial deposits, i.e. well sorted and rounded grained gravel to fine sand, occur in the form of small isolated deposits in depressions of the bedrock. The large valleys along the trail are filled with glacial and postglacial clay. Glacial clay is often varved, reddish with thicknesses varying between 1 and 5 m and a high content of CaCO3 emanating from Ordovician limestone (Möller 1993; Rudmark 2000). Postglacial clay is found as a thick top cover on glacial clay (Möller 1993; Rudmark 2000; Karlsson 2007). In low-lying areas, and particularly, along the fracture zone postglacial clay is covered by gyttja clay and clay gyttja. Peat accumulations consisting of remnants of dead plants have subsequently covered parts of the depressions. The thickness of peat varies between 0.5 and 3 meters (Möller 1993; Rudmark 2000). Peatlands are drained to a large extent and often cultivated.

3.3 Landscape development

Since there are no available investigations along the Långhundraleden Trail the landscape development could be deduced from studies carried out in the surrounding area. According to the deglaciation pattern described by Lundqvist (1994) the ice retreated from the southern part of the Långhundraleden Trail around 9200 BC. Hedenström (2001)

15 Christos Katrantsiotis constructed the shore displacement curve for the Tärnan region located close to the southern part of the trail (Figure 6). The general trend in the curve is regressive. During the transitional phase between the freshwater Ancylus Lake stage and the Littorina Sea stage the shoreline was located > 59 m a.s.l resulting in a remote archipelago with a group of small islands (Hedenström 2001). Two phases of stillstand, probably connected to the early Littorina Sea can be traced in this part of Uppland. According to previous investigations, none of the younger transgression phases (L3 & L4) influenced the area around trail (Risberg & Alm 2011). During the Neolithic, between 5900-3700 BC, the bedrock in the Långhundraleden Trail was about 35 meters below the sea level and the entire route was still an integrated part of the water landscape (Risberg & Alm 2011; Eklund et al. 2011).

The Långhundraleden Trail started to develop after 3000 BC. According to a hypothesis, the emergence of the Vallbyåsen esker, which is an offshoot of Stockholmåsen esker, created a dam effect (Figure 7). Simultaneously the emergence of the threshold area formed a lake in the Långhundraleden Valley (Figure 7). A major problem with this hypothesis is the fact that the esker is made up of permeable material and hence could not have functioned as a dam. Thus, the water was capable of penetrating the esker. Alternatively, the penetration may have ceased when the lower part of esker, covered by clay and silt, emerged above sea level. Another problem is the absence of lake sediment in this area; actually the main portion is mapped as postglacial clay (Lundqvist & Lundegårdh 1956; Möller & Stölhös 1964; Möller 1993; Rudmark 2000). Tentatively, the lake had a short duration, thus producing minor volumes of lake sediment. These layers might have been incorporated in the top soil during younger cultivation activities.

2 km

Figure 7: Map showing the position of the Vallbyåsen esker (black arrow) and the

Långhundraleden Valley (adopted from Risberg & Alm 2011).

16 Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

Around 2000 BC, the Långhundraleden Trail was a part of archipelago consisting of streams that connected the Baltic Sea with the interior part of Upland (Figure 8). As parts of the land emerged from the sea, valleys and protected coves were formed offering the possibility for colonization in the Bronze Age (1700 − 500 BC). The establishment of large farms, villages and hamlets occurred during the Iron Age (500 BC − AD 800). Based on previous investigations, the trail was in a hydrological function, to around 250 BC when the saddle-point emerged from the sea (Figure 8; Plikk 2010; Risberg & Alm 2011). The emergence of the saddle-point led to the gradual replacement of the brackish water by freshwater in the route. Parts of the route were utilized as a mode of transportation between the Baltic Basin and the Old Uppsala until the end of the Viking Age (11th century) thanks to string of lakes, canals and rivers, which occupied the depressions between rocky outcrops and moraine ridges (Ambrosiani 1961; Risberg & Alm 2011). The continuing land uplift has triggered modification of the landscape bringing new land above the water surface. Water connections used as route of transportation closed at various locations. By the middle of the 18th century the route was unusable since the water became too shallow for the boatsDetalj and thus för the 250 commercial f.Kr traffici vattendelaromr ceased. ådet längs Husby-Långhundraleden

N 5 km

Figure 8: Paleogeographical map of the central part of the Långhundraleden trail (black triangle in Figure 6) showing the distribution land/water prior to the

emergence of the saddle-point (black circle; adopted from Risberg & Alm 2011).

17 Christos Katrantsiotis

4. Description of the study site

The site under investigation is a long section located between Gottröra and Husby- Långhundra, in the central part of the Långhundraleden Trail, south of Mälby (Figure 6 & 9). The section is placed within the geological map sheets: Uppsala NW (Möller 1993) and Uppsala NE (Rudmark 2000). The topography of the area is characterized as a fissure valley landscape. According to the geological map, the surface of the lowland along the valley is dominated by gyttja clay and postglacial clay to the east while peat accumulations cover the central and western part of the valley (Figure 9). The low-land is fertile and highly cultivated, surrounded by elevated areas of till and exposed bedrock to the north and south. The elevated areas are covered with spruce or deciduous trees. Along the valley there is a ditch. The water supply is dependent on precipitation and runoff from the surrounding area. According to previous investigations the saddle point is located in the central part of the valley (Figure 9). From this point the water flows in two directions, to the east and west.

Traces of prehistoric settlement are numerous in this part of the trail. The settlements have been affected by changes in water level and the rate of shore displacement. According to the ancient monuments the villages nearby, i.e. Ändeberga, Mälby, Skalhamra and Rickeby were established at their present site at roughly 5th – 6th century (Figure 9; Gunilla Larsson pers. comm. 2012). Despite the fact that there are traces for earlier settlements it seems that radical changes in the structure of settlement occurred during that time.

18 Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

Figure 9: Digital elevation model of the central part of the Långhundraleden Trail (Göran

Alm 2012). The blue line shows the position of the ditch. The black arrows indicate the direction of water flow. The black circle shows the position of the saddle-point. The black dots represent the position of the sampling sites for laboratory analysis.

N 2 km

Bog Wave-washed sand Fen Wave-washed gravel Gyttja Glacial clay Thin peat cover

Glaciofluvial sediments Young fluvial deposits

Ridge-shaped glaciofluvial deposits Gyttja clay Till clayey sandy Post glacial clay

Till sandy Post glacial silt

Figure 10: Maps showing the distribution of Quaternary deposits along the central part of the Långhundraleden Trail (Möller 1993; Rudmark 2000). The black rectangle shows the study section.

19 Christos Katrantsiotis

5. Methods

The reconstruction of the landscape development along the valley from Gottröra to Husby- Långhundra, in the central part of the Långhundraleden Trail was based on stratigraphic studies of sediment cores, including litho- and biostratigraphy in conjunction with chronostratigraphy. The methods were split into fieldwork and laboratory techniques. Fieldwork included the recovery of sediment cores, which is a widely used technique to track changes in landscapes across a range of timescales and the leveling of the coring sites. Laboratory techniques included the analysis of sediments for biological and physical parameters. The biological parameters considered are siliceous microfossils including diatoms, chrysophyceae stomatocysts and sponge spicules. The physical parameter included loss on ignition (LOI). The chronologies of the sediment sequences were established by means of AMS radiocarbon dating of terrestrial macrofossils.

5.1 Field work

5.1.1 Stratigraphical coring and sampling To establish the lithostratigraphy, successive coring was performed on a longitudinal section along the ditch, which is supposed to represent the lower part of the valley (Figure 9). The core segments were taken every 100 or 50 meters covering a distance of c. 5.4 km. The coring was carried out using a Russian peat corer of 1 m length and 4.5 cm diameter. The cores were examined for general lithology, their boundaries and internal structure. Based on the stratigraphy (see results and interpretation) two coring sites were selected for sampling and laboratory analysis (Figure 9). At both sites, which are located in former lake basins, two overlapping sediment cores were collected for diatom analysis and LOI investigation. The choice of the sampling location aimed to obtain as representative sequence of sediment and peat layer as possible. In addition, twenty parallel cores were retrieved from each coring spot using a wider corer of 70 cm length and 70 mm diameter in order to obtain sufficient amount of macrofossils for radiocarbon dating. The cores were placed in rigid plastic half-tubes, wrapped in plastic film and sealed for transport to Stockholm University where they were stored and prepared for laboratory analysis.

5.1.2 Leveling Leveling was performed with a Trimble R8 GNSS to obtain level and location (altitudes) of the coring sites. The main purpose was to construct a longitudinal section and to determine the elevation of saddle-point. The equipment gives the altitude with an error of c.±0.05 m. Erosion, paludification, peat growth, ditching activities and farming can affect the accurate determination of the leveling. As a whole, the geological accuracy is estimated to be ± 0.5m (Risberg 1989). The height system referred to is RH 2000.

20 Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

5.2 Laboratory methods

5.2.1 Loss on ignition (LOI) LOI was applied as a measure of changes in the organic content throughout the sediment sequences (e.g. Dean 1974; Heiri et al. 2001). The relative changes of LOI were regarded as a tool for interpreting changes in the depositional environment over time (e.g. Lowe & Walker 1997; Veres 2002). About 1 cm3 of sediment was contiguously cut out in one cm interval throughout the sequences. Subsamples were placed into pre-weighed crucibles. The combined mass (subsample + crucible) was weighed. The crucibles were placed into the drying oven at 110ºC overnight. The dried samples were weighed and thereafter burnt at 550ºC for four hours to ignite the organic matter. The crucibles were removed from the furnace, allowing cooling. LOI values were measured as the difference in the weight of the sample before and after burning. The % organic matter was calculated from the difference between the weight of the dried sample and the burnt sample divided by the difference between the dried sample and the empty crucible, all multiplied by one hundred.

5.2.2 Diatom analysis Diatoms are a group of microscopic algae that inhabit all aquatic environments. They are encased in a cell wall, which is composed of amorphous hydrated silica. This structure, known as frustules, is well preserved in stratigraphic deposits and displays specific characteristics used for identification. Diatoms are particularly useful as indicators of changes in the aquatic environment since they display well defined ecological preferences and high species diversity. In the context of the present study diatom analysis has been used as a method to trace salinity and water depth changes, which would reflect the isolation sequence of the basins.

Diatoms were extracted from the sediment and prepared according to the standard method compiled by Battarbee et al. (1986). About 1 cm3 sediment were collected, covering the isolation event and the infilling of the lake basins. Subsamples were treated with 10 % HCl to remove calcium carbonate. Organic compounds in the sediment were oxidized by using

17% H2O2. To minimize vivid chemical reactions the samples were left at room temperature overnight and boiled on water-bath the following. After oxidation, the suspensions were repeatedly decanted at two-hour intervals from 100 ml beakers until most of the clay particles were removed. Distilled water with NH3 was added to disperse the remaining clay particles. Eventual sand grains were removed after 5 seconds sedimentation. The residues, consisting of the silt size fraction, were transferred to 5 ml tubes and a volume of the residue was extracted and spread out evenly on the cover-glass. The prepared samples were dried onto cover-slips and mounted on a microscope slide using Naphrax® to increase refraction index. Counting were carried out under a light microscope at a magnification of X1000 using oil immersion to further increase the refraction index. Over 200 diatom valves were counted, where possible, at each level. The identification of diatom taxa and information regarding ecological preferences were based on Cleve-Euler (1951-

21 Christos Katrantsiotis

1955), Krammer & Lange-Bertalot (1986, 1988, 1991a, b) and Snoeijs et al. (1993-1998). The ecological grouping was also performed using additional references (Vos & De Wolf 1988, 1993; Denys 1991/1992; Witak et al. 2006). The diatom species were grouped into classes according to their salinity requirements: Polyhalobous taxa (marine species), Mesohalobous taxa (brackish water), Halophilous taxa (favored by low salinity), Indifferent taxa (freshwater tolerant to a low level of salt), Halophobous taxa (freshwater with no tolerance to salt), Rheophilous taxa (running water), Aerophilous taxa (terrestrial conditions) and taxa with unknown ecology. The diatoms were in addition separated according to their habitat into the following groups reflecting changes in water depth: planktonic taxa (deep water), benthic taxa (shallow water) and taxa with unknown ecology. The results are presented as Tilia graphs showing the percentage abundance of diatoms in terms of salinity. The graphs were constructed using Tilia and Tilia-graph programs (version 1.7.16). Major diatom zones were defined performing stratigraphically constrained cluster analysis in CONISS.

5.2.3 Dating Five levels were AMS radiocarbon dated in each site covering the isolation event, the lake sequence and the initial development of the mire. Macrofossils from terrestrial plants were primarily chosen to avoid reservoir effects that could bias the dates. At some levels it was problematic to recover sufficient terrestrial material for dating. At those depths, chironomid head capsules were dated, in addition to macrofossils. For comparison, macrofossils and chironomids were dated separately from one depth.

Sediment layers from 20 parallel cores collected from each site were visually correlated by means of lithological boundaries. Five segments of c. 2 cm length were sliced from each sediment core. The segments form each depth were put in five separate plastic containers and soaked in 10% KOH to dissolve humic and fulvic acids. After some hours, the material from each container was sieved through a 0.25 mm mesh under running water to remove finer sediments. The residues were dispersed in Petri dishes with distilled water. Identification of macrofossils was performed at X25 magnification under a stereo microscope. Macrofossils and chironomid remains were extracted using soft tweezers. A total of 11 radiocarbon dates was carried out at the Ångström Laboratory, Uppsala University using the tandem accelerator technique. The radiocarbon isotope half-life used was T1/2=5568±30 years. Radiocarbon ages were calibrated to calendar years BC/AD. The calibrated ages were used for constructing the age-depth models. The accumulation rates for each site were estimated according to the formula:

R= H / (age LB – age UA), where R = accumulation rate, H = sediment thickness, LB = age of lower boundary, and UA = age of upper boundary.

22 Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

6. Results and interpretation

6.1 Lithostratigraphy The investigation of lithostratigraphy includes 61 coring sites (Figures 11─14). Red colors mark the sites with lake sediments, i.e. gyttja. Examples of cores are shown in Figures 15─19. Seven major stratigraphical units, informally named A to G from the oldest to youngest, can be identified (Table 1). Although there is a general stratigraphic consistency, all coring sites do not contain all units. In general, the accumulations vary from minerogenic material in the lower parts to organic-rich sediment and peat at the top (Appendix 1; Figure 20).

Table 1: General lithology of the study section and the environment during the time of deposition. Units are coded in stratigraphic order, A to G, from the oldest to youngest. Note that till or bedrock is supposed to underlain glacial clay.

Unit Lithology Environment G Fluvial deposits River F Reed/fen/carr peat/Anthropogenic filling Terrestrial E Gyttja Freshwater lake/lacustrine freshwater

D Gyttja clay/clay gyttja Littorina Sea/shallow brackish water

C Sand/gravel Shallow coast/erosion B Post glacial clay Ancylus Lake/deep freshwater A Glacial clay Yoldia Sea/deep brackish water

Unit A: Glacial clay Description: The lowermost unit, which occurs at the base of the section, consists of grey to brown clay with scattered occurrences of dropstones. The thickness of this unit varies from a few centimeters to several meters. In general, the clay is homogenous or weakly varved. At sites, the clay consists of well-developed and distinct varves characterized by alternating layers of reddish brown summer layers and a dark grey winter layers. Interpretation: This unit represents a typical feature of varved glacial clay deposited after the deglaciation during the brackish phase of the Yoldia Sea stage (Kristiansson 1986; Brunnberg 1995; Wastegård et al. 1998). The absence of varves can be attributed to the increasing salinity of the bottom water of the Yoldia Sea stage, which caused aggregation of particles hampering the formation of varves (Brunnberg 1995).

Unit B: Postglacial clay Description: This unit, which covers glacial clay along the section, consists of homogeneous and bluish-grey clay with black sulfide bands and scattered occurrences of shell fragments. At some sites, the clay is more light-brownish in color and heterogenic

23 Christos Katrantsiotis with bands of sand and silt. The thickness of this unit is variable. The maximum thickness, c. 4 meters, can be observed in the eastern part of the section. Interpretation: This unit exhibits typical features of postglacial clay deposited during the Ancylus Lake (Åker et al. 1988; Karlsson & Hansbo 1989). Postglacial clay constitutes redeposited glacial clay and other fine-grained sediment by wave action or streams. The bands of iron sulfide could be attributed to the anoxic bottom conditions. Thin layers of sand and silt indicate periods of erosion.

Unit C: Sand/gravel Description: The postglacial clay underlies a grey bed of loosely packed, coarse to fine sand and gravel. The thickness of this unit ranges from 1 to 40 cm. Interpretation: Sand and gravel were probably washed from the nearby elevated areas. The sharp contact between clay/sand indicates that the sedimentation was interrupted by period of erosion i.e. the formation of hiatuses. The gradual boundary between sand/gravel and the upper layer reflect a period of continuous deposition.

Unit D: Gyttja clay/clay gyttja Description: This unit can be subdivided into two sub-layers. The lower sub-layer, which covers postglacial clay and sand/gravel, consists of beige/grey gyttja clay. At places, this sub-layer is laminated having thin dark bands and scattered fragments of shells and plants, especially in the eastern part of the section. The thickness of the gyttja clay usually ranges from a few cm to more than two meters. The gyttja clay gradually passes into greenish greyish clay gyttja upwards. The thickness of this sub-layer usually ranges from a few cm to more than one meter. Overall, the clay gyttja and gyttja clay are unconsolidated and has darker color compared to the lower layers indicating higher organic content. Gyttja clay is located stratigraphically below clay gyttja and has a finer structure. At some sites, the clay gyttja/gyttja clay is characterized by the presence of the brackish/lagoonal algae Vaucheria. (Xanthophyceae). It should be mentioned that the terms gyttja clay refers to sediments with 2–6% humic matter and clay gyttja to sediments with 6–20% humic matter. In this study, however, the identification was based on visual observations and is thus approximate. Interpretation: Gyttja clay and clay gyttja were probably formed by deposition of highly decomposed organic material along with clay during the Littorina Sea stage. The high organic content indicates an increase in the primary production and inwash of organic material. The laminae are interpreted to reflect anoxic and eutrophic conditions (Eronen 1988). Clay gyttja or gyttja clay with Vaucheria was probably deposited during the lagoonal stage of the basin (cf. Granlund 1931; Rosqvist 2010). Vaucheria preferably grows in brackish water and/or sheltered semi-enclosed bays with river inflows (Kersen 2012). It should be noted, however, that there are a number of Vaucheria species, which are confined to freshwater conditions and some to fully marine conditions (Christensen 1988).

Unit E: Gyttja Description: At several sites, coring revealed the occurrence of gyttja, characterized as a light-colored, soft, brown to reddish sediment, rich in plant and organic remnants. This unit

24 Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail is normally found above the clay gyttja/gyttja clay in the deepest part of the former lake basins. The thickness of this unit varies from 5 cm centimeters to over 70 cm. Different composition of gyttja can be found: dark-brown coarse detritus gyttja containing seeds, moss tissue, leave remains leaves and other macrofossils, fine detritus gyttja and gyttja rich in algae/Vaucheria. Interpretation: Gyttja was deposited in freshwater conditions at the bottom of eutrophic lakes. The accumulation occurred by deposition of suspended matter in water and in the surface run-off from the catchment (Łachacz et al. 2009). The various types of gyttja may indicate changes in the water organic production and the water level. Coarse detritus gyttja, rich in macro- and microfossils, may indicate shallow water conditions. Homogenous fine detritus gyttja suggests the prevailing of deeper water conditions. Algal gyttja could indicate a phase of lowering water level with high productivity. The observed Vaucheria species could here indicate freshwater environment (Christensen 1988). Alternatively, the presence of Vaucheria could reflect a period with a mixture of freshwater and brackish water conditions.

Unit F: Peat/ Anthropogenic filling Description: The gyttja sequences gradually passes upwards into reed peat. At two coring sites alternating layers of clay gyttja, gyttja and reed peat were found (Figure 16). Reed peat is dark brown in color, dense in structure and is composed of remains of a variety of swamp plants, mostly reeds, sedges and grasses. At places, it was difficult to penetrate this layer due to compact structure and the presence of thick roots. The whole section is covered by a thick layer of heterogeneous fen or carr peat. The thickness of this peat varies from 10 to 50 cm. The peat is at most sites dark brown in color, humified, almost amorphous. It is composed of compacted organic masses consisting of leaves, roots and other plants with wood fragments. At sites fen/carr peat is found directly on top of sand and gravel. At some parts of the section peat have been progressively removed, due to impact from human activities. These parts are covered by ponds and heaps of excavated soil mixed with organic material. Interpretation: The peat successions record processes connected with gradual shallow and successive infilling of the basin leading to the terrestrial environment. Reed-sedge peat accumulations represent the first stage in the peatland development. Decomposition of vegetation in stagnant water formed a thick layer of reed peat above gyttja. Thus, reed peat together with gyttja reveals the position of former lakes located along the study section. Fen/carr peat represents the final step of the transition to the terrestrial environment as the soil surface rises above the water.

Unit G: Fluvial sediments Description: Fluvial sediments cover the western part of the section close to a small river (coring site 1). The deposits are composed of compacted and dry clay and silt. Interpretation: River deposits were formed during flooding episodes when the water table in the nearby river covered the surrounding flat area.

25 Christos Katrantsiotis

15 -

Coring sites 1 sites Coring

Figure 11: Figure

26 Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

32 -

Coring sites 15 sites Coring

Figure 12: 12: Figure

27 Christos Katrantsiotis

Coring sites 32 sites Coring

Figure 13: Figure

28 Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

61 -

Coring sites 49 sites Coring

14: Figure

29 Christos Katrantsiotis

Figure 15: Coring site 12, the sedimentary sequence between 70─150 cm depth (11.30─10.50 m a.s.l) consists of, from up to bottom: reed peat, gyttja, clay gyttja, sand and postglacial clay. Bottom is to the left.

Figure 16: Coring site 14, the sedimentary sequence between 50─100 cm depth (11.42─10.92 m a.s.l.) consists of, from up to bottom: clay gyttja, gyttja clay, sand and gravel and postglacial clay. Bottom is to the left.

Alternating layers!

Figure 17: Coring site 22, sedimentary sequence between 50 ─145 cm depth (11.87─10.92 m a.s.l.) consists of, from up to bottom: fen peat, reed peat, gyttja, clay gyttja, reed peat, gyttja, clay gyttja and gyttja clay. Note the alternating layers of reed peat, gyttja and clay gyttja between 65─114 cm. Bottom is to the left.

Figure 18: Coring site 46, the sedimentary sequence between 108─200 cm depth (10.87─09.95 m a.s.l.) consists of, from up to bottom: sand/gravel, postglacial clay and varved glacial clay. Note the transition from varved glacial clay to post glacial clay. Bottom is to the left.

Figure 19: Coring site 53, the sedimentary sequence between 150─250 cm depth (8.37─7.37 m a.s.l.) consists of postglacial clay with dark bands of sulfide. Bottom is to the left.

30 Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

. : the highest point of of point :the highest

elow)

site 25 site

Coring site 23 & 28: sampling sites for laboratory analysis (see b (see analysis laboratory for sites sampling 28: & 23 site Coring

point. point.

saddle

Lithostratigraphy of the study section. Coring site 23: the highest point of the ground surface. Coring of surface. point the ground highest 23: site the Coring of the section. study Lithostratigraphy

Figure 20 Figure the i.e. surface, mineral theunderlying

31 Christos Katrantsiotis

6.2 Leveling and morphology The topography of the study section is characterized by low-lying and relatively flat to gently sloping ground surface. The highest point of the ground surface, along the section was leveled to 12.8±0.05 m a.s.l., 1 km southwest of Mälby, in the central part of the section (coring site 23; Figure 20). This site represents the present day watershed which is located in the narrowest point of the trail between two bedrock outcrops. The topography gradually slopes to the east and west of the highest point expanding into a broad smooth and flat plain surrounded by slightly elevated areas. The part of the valley located between coring sites 44─61 exhibits lower topographic gradient than the western side. The lowest point reaches 11.3±0.05 m a.s.l. (coring site 59; Figure 20).

The simplified section shown in Figure 21 depicts the topographical features of the trail prior to the accumulation of the youngest deposits, i.e. peat/flooding sediments/anthropogenic filling. The elevation of the saddle-point, which is the highest point of the underlying mineral surface emerged from the sea along the trail, was estimated to 12.5 m a.s.l. (coring site 25; Figure 20 & 21). The emergence of the saddle-point had an important hydrological function as the water flowed from this point in both eastward and westward directions. Note that the altitude of the saddle-point is c.30 cm lower than the highest point of the ground surface since the latter represents the highest elevation of present-day peat surface (coring site 23; Figure 20).

A series of basins, informally named A-D, are distributed east and west of the saddle-point (Figure 21). The isolation thresholds, i.e. the altitude at which the sea was in contact with the basins just before the final isolation, are flat and diffuse cutting glacial and postglacial sediments. The basins are subdivided into smaller sub-basins separated by shallow and lower threshold areas (Figure 21). The basins are now capped by a relatively thick layer of peat and cannot be traced to the surface. Prior to the overgrowth, the basins were generally shallow with sides that sloped steeply to a depth of 1-2 meter in relation to the saddle-point of the trail and small in extension c. 300─500m long (Figure 21). The extension of the basins should be considered as tentative since no vertical sections were made to estimate their north-south extensions.

32 Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

accumulation accumulation

central central part of the trail and the tentative extension of basins prior to

the

of of

/anthropogenic filling /anthropogenic

Simplified Simplified topography

: :

Figure Figure 21 sediment ofpeat/flooding

33 Christos Katrantsiotis

6.3 Sampling sites for laboratory analyses Two basins were considered as suitable for sampling after the lithological investigation and the determination of the topography of the study section. Criteria for the choice were their geographical distribution and some basin characteristics, including the size and the relatively extensive and long gyttja sequences. The basins, informally named A& B, are situated on the eastern-central part of the section, east and west of the saddle-point (Figure 21 & 22). Both basins are now mires, which have been formed through the overgrowth of ancient lakes. The primary aim of investigating these two basins was to provide a chronological estimation of the emergence of the saddle-point and detailed reconstruction of environmental changes around this point.

Figure 22: A simplified sketch showing the tentative extension of the studied basins and the location of the sampling sites (coring sites 23 & 28).

34 Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

6.3.1 Basin A

Basin A is located c.1 km southwest of Mälby, west of the saddle-point (Figures 21 & 22). The basin is now covered with peat resulting in a flat topography or gently sloping ground. Peat is affected by human activities in the form of ditching and cultivation. The eastern part of the basin, which is located in the narrowest point of the Långhundraleden Trail, is delimited to the south and north by elevated areas of exposed bedrock covered with forests. To the west the basin is surrounded by broad smooth and slightly elevated areas which consist of fields. The isolation threshold, leveled to 12.4±0.05 m a.s.l., is located at the western edge of the basin extending over a flat surface (Figures 20 & 21, coring site 3). The sediment at the threshold consists of gyttja clay, which is affected by cultivation. Prior to the accumulation of younger deposits, the basin was divided into several sub-basins separated from each other by lower isolation thresholds. In general, the basin was shallow with a maximum depth of 3 m, in relation to the threshold and relatively large in extension, 1.6 km long (Figure 21& 22).

The sediment core for laboratory analysis was collected from borehole 23 located at the eastern edge of the basin (Figures 21 & 22). The core is extended from the ground surface down to a depth of 200 cm. The stratigraphy consists of, from the bottom-up, glacial clay, sand and gravel, gyttja clay, clay gyttja, gyttja, reed peat and fen peat (Table 2).

Table 2: Sediment sequence in the coring site 23 based on field observation.

Depth (cm) m a.s.l. Lithology Short description 000–065 12.81-12.16 Carr peat Black/brown, humified, almost amorphous, with wood fragments and plant remains 065–078 12.16-11.93 Reed peat Dark/brown, dense and compact, humified, with thick roots and remains of swamp plants 078–095 11.93-11.86 Gyttja Dark grayish brown, fine-grained, soft with plant fragments, gradual contacts 095–125 11.86-11.56 Clay gyttja Grayish, coarser 125–140 11.56-11.41 Gyttja clay Beige/grey 140-143 11.41-11.38 Sand and gravel Thin, grey layer, loosely packed 143>200 11.38>10.81 Glacial clay Weakly varved, grayish

35 Christos Katrantsiotis

6.3.1.1 Age-depth model Five samples consisting of terrestrial macrofossils were AMS dated (Table 3). Calibrated ages with 2σ were plotted as an age-depth model (Figure 23). The uncertainty is less than ±150 years. The isolation age was estimated by fitting a linear extrapolation (see diatom results). Accumulation rates were calculated between calibrated ages (Table 4).

AMS-dating resulted in ages between 46 BC and AD 324. The dates seem to be concordant with respect to the depth without any abrupt changes that could have affected the accumulation rates (Figure 23). According to the age-depth model, the middle and upper part of clay gyttja should have been deposited between c.AD 40 (46 BC – 85 AD) and c. AD 60 (2 BC – AD 124). The deposition of gyttja should have begun c. AD 70 (1BC – AD 128). The reed peat should have started to accumulate c. AD 200±60.

Three phases with different accumulation rates can be distinguished (Table 4). Clay gyttja accumulated more rapidly prior to or immediately after the isolation with a rate of c.5.6 mm/yr. A tentative interpretation includes an increased sediment input probably from surface run-off or by fluvial process (cf. Jaffer 2010). The accumulation rate decreases to c. 3.0 mm/yr prior to the deposition of gyttja. In the overlying layers the rate varies little, from c.1.0 mm/yr to 0.8 mm/yr. This relatively low accumulation rate could indicate stable conditions in a shallow eutrophic lake (cf. Björck 2010).

Table 3: Radiocarbon dates for basin A. Calibrated ages are shown with 1σ and 2σ.

Lab. Depth Lith. Dated material Age14C Cal. ages Cal. ages no. (cm) yrs BP (BC/AD) 1σ (BC/AD) 2 σ Ua- 79-80 Gyttja Seeds (Carex sp.) 1808±31 AD 138 – 196 (40.1%) AD 126 – 260 (87.1%) 41316 AD 208 – 242 (28.1%) AD 283 – 324 (8.3%)

Ua- 87-88 Gyttja Seeds (Carex sp., 1864±30 AD 86 – 106 (13.5%) AD 76 – 230 (95.4%) 41317 Betula sp., AD 120 – 177 (39.7%) Lysimachia sp.), AD 190 – 212 (15.0%) Bud scales (Betula sp.) Ua- 93-95 Gyttja Bud scales (Betula 1944±31 AD 20 – 85 (65.2%) 34 – 30 BC (0.6%) 41318 sp.), Seeds (Carex AD 110 – 115 (3.0%) 20 – 12 BC (1.8%) sp., Cicuta virosa, 1 BC – AD 128 (93.0%) Lycopus europaeus) Ua- 96-98 Clay Seeds (Rumex sp., 1951±31 AD 17 – 80 (68.2%) 37 – 29 BC (1.9%) 41319 gyttja Carex sp.), 22 – 10 BC (3.2%) Leaf (Salix sp.) 2 BC – AD 124 (90.3%)

Ua- 105-106 Clay Seeds (Carex sp., 1974±31 18 – 14 BC (2.1%) 46 BC – AD 85 (95.4%) 41320 gyttja Alnus sp., Betula AD 1 – 66 (66.1%) sp., Rumex sp.)

36 Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

Figure 23: Age-depth model for Basin A. All dates are stated with 2σ.

Table 4: Accumulation rates at Basin A.

Interval Vertical Time interval Time Accumulation (cm) distance (mm) (BC/AD) (years) rate (mm/year)

87.5−79.5 80 AD 130 − 230 100 0.8

94.0−87.5 65 AD 65 − 130 65 1.0

97.0−94.0 30 AD 55 − 65 15 3.0

105.5−97.0 85 AD 40 − 55 15 5.6

37 Christos Katrantsiotis

6.3.1.2 Loss on ignition A sequence of 90 cm thickness, between 135 and 45 cm depth, was analyzed. The sequence consists of gyttja clay, clay gyttja, gyttja, reed peat and fen peat. The results are shown as a curve in Figure 24. In general, the amount of organic content gradually increases from 5% in the bottom to 90% at the top. Details about the loss on ignition results are given in the diatom zones description.

6.3.1.3 Diatom analysis In the analyzed sediment sequence between 133.5 and 75.5 cm depth 190 diatom taxa were identified from the following genera: Achnanthes (2 taxa), Amphora (4), Amphipleura (1), Figure 24: Loss on ignition results at Basin Anomoeneis (1), Aulacoseira (5), Caloneis A. Note that the measurements do not cover (4), Campylodiscus (1), Chaetoceros (1 the entire sequence of the diatom analysis. resting spores), Cocconeis (2),

Coscinodiscus (4), Cyclostephanos (1), Cyclotella (2), Cymatopleura (4), Cymbella (20), Diploneis (4), Ellerbeckia (1), Eunotia (1), Epithemia (4), Fragilaria (12), Frustulia (1), Grammatophora (2), Gomphonema (11), Gyrosigma (3), Hantzschia (2), Hyalodiscus (1), Mastogloia (4), Melosira (3), Meridion (1), Navicula (27), Neidium (4), Nitzschia (16), Pinnularia (15), Rhabdonema (2), Rhopalodia (3), Rhoicosphenia (1), Stauroneis (4), Stephanodiscus (2), Surirella (6), Tabellaria (2) and Thalassiosira (3). Diatoms are abundant between 119.5 and 93.5 cm depth. Diatom preservation is generally moderate with a relatively high number of corroded valves and fragments in the lower part of sequence. The analyzed sequence also contains other siliceous microfossils e.g. Chrysophyceae stomatocysts and phytoliths. All diatom taxa classified according to salinity preferences and living conditions are shown in the Appendix 2.

The diagram showing the relative abundance of diatoms in each level has been separated in three parts; the first part shows polyhalobous, mesohalobous, halophilous and indifferent taxa (Figure 25). The second part presents halophobous taxa and rheophilous taxa (Figure 26). The third part is a summary diagram where all taxa are shown as groups (Figure 27). Species with a relative maximum abundance below 2% were excluded from the graphical illustration. Data on depth and lithological stratigraphy as indicated by field observations are included in the diagram. Results from the loss on ignition analysis were incorporated in

38 Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail the final interpretation. Based on the diatom stratigraphy three stages can be identified in evolution of the basin:

Zone 1 (133.5 ─ 116 cm, 30 BC ─ AD 20) consists of gyttja clay with a transition to clay gyttja at 125 cm depth. The amount of organic content is low and relatively stable reaching around 20%. The diatom concentration is relatively low. Overall, the diatom flora is dominated by benthic species whereas planktonic taxa increase upwards. This shift is mainly related to the higher content of Aulacoseira ambigua. In terms of salinity, indifferent taxa are predominant (up to 50%), being mainly represented by Cocconeis placentula and Epithemia adnata. Other taxa such as Epithemia sorex, Amphora libyca, Diploneis ovalis and Navicula rhynchocephala occur with lower percentages. Towards the upper boundary of the zone there is an increase in the amount of halophobous taxa (up to c.50%) represented by Gyrosigma accuminatum, Navicula americana and Aulacoseira ambigua. Another characteristic feature of the diatom assemblage is the relatively high abundance of polyhalobous/mesohalobous species, which constitute about 20% of the lower part of the zone. Most abundant are the polyhalobous Cocconeis scutellum and Diploneis smithii, and the mesohalobous Hyalodiscus scoticus and Mastogloia smithii. Chaetoceros spp resting spores are common to frequent. Halophilous species, e.g. Epithemia turgida and Rhoicosphenia abbreviata, are less abundant (up to 5%). A low proportion of rheophilous species (up to 2-3%), e.g. Meridion circulare, occur in this zone. Interpretation: The dominance of indifferent taxa together with the low percentages of estuary polyhalobous/mesohalobous species probably reflects the development of a shallow and sheltered brackish-freshwater bay or coastal lagoon. This interpretation is also supported by the presence of lagoonal taxon Campylodiscus echeneis (Miller 1986). The dominance of freshwater species towards the upper boundary of the zone indicates a period with lower salinity, probably related to freshwater input from nearby river mouths and/or in the form of groundwater. Inflow of freshwater is supported by the occurrence of Meridion circulare. Most of the species are benthic indicating shallow-water. The presence of Aulacoseira ambigua towards the upper part of the zone could be used as an indicator of the existence of extended open water (Puusepp & Kangur 2010).

Zone 2 (116 ─ 93 cm, AD 20 ─ 100) corresponds to clay gyttja with a transition to gyttja at 95 cm depth. The amount of organic matter increases significantly, reaching 60%. This zone is characterized by mass occurrences of benthic species. The proportion of planktonic taxa is relatively low represented by Aulacoseira spp. The zone is rich in indifferent taxa, which attain up to 80%. Cocconeis placentula and Fragilaria construens peak at 60% and 40%, respectively. The amount of halophobous taxa fluctuates between 20 and 40%, with high frequencies of Aulacoseira crenulata, Fragilaria capucina, Aulacoseira italica, Eunotia spp and Navicula radiosa. The amount of halophilous species, e.g. Epithemia turgida and Rhoicosphenia abbreviata, significantly decreases in the low and middle part of this zone. Epithemia turgida increases again towards the upper boundary. Mesohalobous species, which diminish to trace level, is mainly represented by Melosira lineata. Typical marine diatoms are not present in this zone.

39 Christos Katrantsiotis

Interpretation: The lower part of the zone corresponds to the final isolation of the basin as the threshold has been uplifted above the mean sea level. According to the stratigraphy and the composition of diatom flora the isolation took place during the deposition of clay gyttja. The final isolation is defined at a depth of 116 cm. This level was dated to 70 BC – AD 60 with the highest probability around AD 20. The major event is recorded in the diatom flora as the disappearance of typical marine and brackish water taxa as well as the predominance of taxa with freshwater affinity that tolerate slightly brackish water and typical freshwater forms. This change in the diatom composition coincides with the gradual increase in the amount of organic matter. The high abundance of indifferent taxa after the isolation and the presence of Epithemia turgida towards the upper part of the zone could be the result of high electrolyte content originating from the lime content in the soils (cf. Hedenström & Risberg 2003). After the final isolation significant increase in the amount of organic content in combination with the mass occurrences of epiphytic/periphytic diatoms, typical for shallow littoral zone, is interpreted to represent shallow water and increased biological productivity.

Zone 3 (93 ─ 83 cm, AD 100 ─ 180) corresponds to most of the gyttja sequence. The organic content remains relatively stable between 50% and 60%. The abundance of diatoms decreases dramatically. Benthic diatom species dominate this zone. In terms of salinity, halophilous taxa comprise more than 80% of the diatom flora towards the upper part. High percentage of indifferent taxa (up to 50%) occurs in the lowermost part of the zone. Cocconeis placentula and Epithemia adnata are the most abundant indifferent taxa. The amount of Epithemia turgida decreases towards the upper boundary. This zone also contains some scattered fragments of the marine-brackish taxon Mastogloia smithii. Interpretation: The lithology, in conjunction with the diatom composition, is believed to reflect a typical freshwater lacustrine environment. This is probably the result of the regressive shore displacement sparking more efficient input of freshwater taxa from the nearby river mouths. The stable percentage of organic content probably indicates a stable environment. High amount of benthic diatoms is interpreted to represent shallow water conditions. The scattered occurrence of the marine-brackish taxon Mastogloia smithii could be a result of reworking and redeposition of frustules from older deposits.

Zone 4 (< 83 cm, > AD 180) consist of gyttja with a transition to reed peat at 78 cm depth. The amount of organic content increases significantly in the peat reaching at 90%. This zone is devoid of diatoms. Interpretation: The significant increase in the amount of organic content in combination with the lithological changes indicate the infilling of the lake, which is dated around AD 220 (AD 150 – 270). The absence of diatoms may be caused by valve dissolution due to more or less terrestrial conditions in the newly established reed belt. This plant has a high demand for amorphous silica to form phytoliths and it is assumed that the roots are able to dissolved already deposited diatom frustules (cf. Stryuf et al. 2007). Furthermore, the shallow water depth causes a reduction in the presumptions of diatom growth. Also the high growing and dense reeds cause a reduction in light at the ground level.

40 Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

10 8 6 4 CONISS 2

Total sum of squares

Zones

4 3 2 1

Rhopalodia gibba Rhopalodia Nitzschia amphibia Nitzschia

20 Navicula rhynchocephala Navicula 40

Indifferent

Fragilaria consturens Fragilaria Fragilaria brevistriata Fragilaria

20 Epithemia sorex Epithemia

20 Epithemia adnata Epithemia

Diploneis ovalis Diploneis

Cymbella cistula Cymbella

Cymbella aspera Cymbella

60 . 40

Cocconeis placentula Cocconeis Mälby

Halophilous silicula Caloneis

Amphora ovalis Amphora

Amphora libyca Amphora

point, at point,

Rhoicosphenia abbreviata Rhoicosphenia

Navicula slesvicensis Navicula

Navicula capitata Navicula

Gyrosigma parkerii Gyrosigma

Epithemia turgida Epithemia

Mesohalobous pediculus Amphora

Nitzschia levidensis Nitzschia

Navicula peregrina Navicula Gyttja clay

Melosira lineata Melosira

Mastogloia smithii Mastogloia

Hyalodiscus scoticus Hyalodiscus Fragilaria pulchella Fragilaria gyttja Clay

Polyhalobous

Chaetoceros spp. resting spores resting spp. Chaetoceros

Campylodiscus echeneis Campylodiscus Amphora commutata Amphora

Gyttja

Rhabdonema arcuatum Rhabdonema Diatom diagram showing the percentage abundance of polyhalobous, mesohalobous, halophilous and

Grammatophora marina Grammatophora

Diploneis smithii Diploneis Cocconeis scutellum Cocconeis

Reed peat

Lithology

Figure Figure 25: thesaddle west A, of at basin species indifferent Depth (cm) Depth 75 80 85 90 95

100 105 110 115 120 125 130 135 Age interval (BC-AD) interval Age AD 76 - 230AD AD 126 - 324AD 46 BC - AD 85 46 - BC AD 60 70 - BC AD 34 BC - AD 128 34 - BC AD 124 37 - BC AD

41 Christos Katrantsiotis

10 8 6 4 CONISS Rheophilous 2

Total sum of squares of sum Total

Zones

4 3 2 1

Meridion circulare Meridion

Surirella robusta Surirella

philous philous species at basin

Pinnularia spp Pinnularia

Pinnularia viridis Pinnularia

Pinnularia streptoraphe Pinnularia

Pinnularia rupestris Pinnularia

Pinnularia maior Pinnularia

Navicula viridula Navicula Navicula pupula Navicula 40

Navicula radiosa Navicula

Navicula bacillum Navicula Navicula americana Navicula Halophobous

Gyrosigma acuminatum Gyrosigma

Gomphonema truncatum Gomphonema

Gomphonema angustatum Gomphonema Gomphonema angustum Gomphonema

20 Gomphonema acuminatum Gomphonema

20 Fragilaria ulna Fragilaria

Gyttja clay Gyttja

. 20

Fragilaria dilatata Fragilaria

Fragilaria capucina Fragilaria

Mälby

Clay gyttja Clay Eunotia spp Eunotia

Cymbella minuta Cymbella

Cymbella cymbiformis Cymbella at point,

- Aulacoseira spp Aulacoseira

Gyttja Aulacoseira italica Aulacoseira

Aulacoseira crenulata Aulacoseira Diatom diagram showing the percentage abundance of halophobous and rheo

20 Aulacoseira ambigua Aulacoseira

Reedpeat

Lithology

Figure Figure 26: thesaddle west A, of

Depth (cm) Depth

75 80 85 90 95

100 105 110 115 120 125 130 135 Age interval (BC-AD) interval Age AD 76 - 230 - 76 AD AD 126 - 324 - 126 AD 46 BC - AD 85 AD BC 46- 60 AD BC 70- 34 BC - AD 128 AD BC 34- 124 AD BC 37-

42 Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

CONISS

Totalsum squaresof

Zones

3000

2000

1000

Basic sum Basic

Unknown ecology Unknown

Rheophilous

Aerophilous

Mälby

Gyttja clayGyttja

Halophobous

point, at at point,

Claygyttja

Indifferent

Gyttja

Halophilous

Mesohalobous

Diatom Diatom diagram showing the percentage abundance of all taxa and the variation in the organic matter

Polyhalobous

Reedpeat

Lithology

Figure Figure 27: saddle the of west A, basin at (%)

Depth (cm) Depth

135

130

125

120

115

110

105 100

Age interval (BC-AD) interval Age

AD 76 - 23076 - AD

AD 126 324 AD -

70 BC - AD 60 70AD BC-

46 BC - AD 85 46AD BC-

37 BC - AD 124 37AD BC- 34 BC - AD 128 34AD BC-

43 Christos Katrantsiotis

6.3.2 Basin-B

Basin B is located c. 800 m southwest of Mälby, east of the saddle-point (Figures 21 & 22). The area is a broad smooth and flat plain covered with peat, which is ditched and cultivated. The ground surface gradually rises to the south and north giving way to slightly elevated areas and forests. Prior to the accumulation of the younger deposits the basin was 2 m deep in relation to the threshold and 600 m long (Figure 21). The isolation threshold is located at the eastern edge of the basin. The threshold level has been altered by means of peat growth. The present elevation is c.12.6±0.05 m a.s.l. The initial threshold, at 12.3± 0.05 m a.s.l., cuts through sand and clay (Figures 20 & 21, coring site 32).

The sediment core for laboratory analysis was collected from borehole 28 located in the central part of the basin (Figures 21 & 22). The core spans the sediment sequence form the surface down to a depth of 3 m. The stratigraphy consists of, from the bottom-up, post glacial, gyttja clay, clay gyttja, algal gyttja, clay, reed peat, and fen peat (Table 5). Note the thin clay layer at the gyttja/peat boundary (Figure 28). It should be mentioned that in some of the cores collected for dating the clay layer was missing whereas in other cores it was observed within the gyttja layer.

Table 5: Lithology of the analyzed sediment core 28 based on filed observation.

Depth (cm) m a.s.l. Lithology Short description 000–030 11.69–11.39 Fen peat Black/brown, humified, almost amorphous, with wood fragments and plant remains 030–087 11.39–10.74 Reed peat Dark/brown, dense and compact, humified, with thick roots and remains of swamp plants 087−090 10.74−10.79 Clay Thin, grey 090–155 10.79–10.04 Gyttja Dark grayish brown, fine-grained, soft with plant fragments, gradual contacts 155–192 10.04–09.77 Clay gyttja Grey-brown 192–200 09.77–09.69 Gyttja clay Dark/grey, some laminations 200>300 09.69>08.69 Postglacial clay Bluish/gray clay, homogeneous

44 Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

Figure 28: Coring site 28, sediment cores collected for dating. The sedimentary sequence consists of, from up to bottom: fen peat, reed peat, clay and gyttja. Bottom is to the right. Note the thin layer of clay observed at the boundary of gyttja/reed peat and/or within the gyttja.

45 Christos Katrantsiotis

6.3.2.1 Age-depth model Five samples were AMS dated; three dates were obtained from terrestrial plant macrofossils and two from a mixture of plant remains and chironomid head capsules (Table 6). For comparison, the materials were dated separately at 105−107 cm depth. The results indicate that insects yield c. 200 years older ages. Since plant remains are considered as the most reliable material for dating, 100 years were added to the dates obtained from the mixture of terrestrial plant macrofossils and chironomids (140−142 and 122−124 cm depth). This correction was based on the fact that terrestrial plant macrofossils counted in both levels were approximately twice the amount of chironomid head capsules. Therefore, the former contributed more to the determination of the age.

Corrected and calibrated ages with 2σ were plotted against the depth (Figure 29). The uncertainty, which account for 95.4% of the probability, is less than 200 years. As a whole, AMS dates spans the period between 358 BC and AD 965. The age-depth model shows a relatively chronological order with upwards younger ages indicating that major disturbance of the sedimentation has not occurred. The upper part of clay gyttja should have been deposited c. 200 BC (358−87 BC). The deposition of gyttja should have begun c. 50±100 BC. The accumulation of reed peat should have started c. AD 850 ± 100.

Accumulation rates vary little throughout the sequence (Table 7). Higher rate of c.0.9 mm/yr occurred prior the isolation, decreasing to 0.5 mm/yr upwards. Such rates are reported from shallow eutrophic lakes in southern Sweden (cf. Björck 2010).

The δ13C values, which are given with the dates, indicate two phases. The relatively high values in clay gyttja and gyttja reflect aquatic environment. The low δ13C values in the upper part reflect a dominantly terrestrial source of organic matter.

46 Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

(83.9%)

379 (0.9%) 379

869 (95.4%) 869

965 (9.8%) 965 (95.4%) 549 (94.5%) 350

─ ─

─ ─ ─ ─

─

55 BC (3.3%) BC 55

246 BC (1.4%) BC 246 BC (62.2%) 87

282 BC (28.5%) BC 282

─ ─

─ ─ ─

(BC/AD) 2 σ (BC/AD)

─ ─

Corr. & Cal. ages Cal. & Corr.

78 78

AD 917 AD

258 235 AD 369 AD

(1.7%) 739 ─ 725 AD AD 771 ─ 900 900 ─ 771 AD 668 AD

358

AD 345 AD 126 AD

489 (7.9%) 489

655 (87.5%) 655

869 (95.4%) 869 (95.4%) 418

(9.8%) 965

233 (95.4%) 233

─ ─

─ ─ ─

─ ─ (1.4%) BC 246 BC (62.2%) 87 (3.3%) BC 55

Cal. ages Cal.

282 BC (28.5%) BC 282

917

─ ─ ─ ─ (BC/AD) 2 σ (BC/AD)

─

78 78

AD AD

258 235

AD 725 ─ 739 (1.7%) 739 ─ 725 AD 436 AD 25 AD

AD 771 ─ 900 (83.9%) 900 ─ 771 AD 530 AD

358

AD 668 AD 239 AD

(68.2%)

210 (6.3%) 210

780 780 (44.2%) 390

635 (68.2%) 635 (24.0%) 300 170 (61.9%) 170

─

─ ─ ─

─ ─

Cal. ages Cal. (35.4%) BC 150 (11.2%) BC 110

300 BC (21.5%) BC 300

(BC/AD) 1σ (BC/AD)

─ ─ ─

─

AD 190 AD

AD 60 AD 210 140

AD 685 AD 320 AD

350

AD 770 ─ 890 (68.2%) 890 ─ 770 AD 550 AD 250 AD

C C

yrs

Age

1182±33 1260±36 1477±45 1711±42 1891±43 2148±36

29.9 37.4 36.2 33.5 25.9

19.1

------

VPDB δ13 C ‰ ‰ δ13 C

Material Material dated, depths and ages for the coring site 28 (Basin B)

sp.)

sp., sp., sp.,

sp.)

sp., sp.,

sp.)

Carex Carex

Rumex Rumex

(

Betula

Carex

(Betula (Betula

sp., sp.,

crispus)

Table 6: . capsules

capsules, capsules,

Alnus

Seeds

Dated material Dated

Cyperaceae Cyperaceae

Seeds Seeds

Seeds ( Seeds

Chironomid head head Chironomid head Chironomid head Chironomid Seeds ( Seeds

Alnus

peat

Lith.

Clay

Reed

Gyttja Gyttja Gyttja gyttja

Gyttja

107 107 124 142 162

------

(cm)

Depth Depth

105 122 140 160

105

- - - -

no.

Lab

Ua Ua Ua Ua Ua

44345

44344 44346 44347 44348 44349

47 Christos Katrantsiotis

Figure 29: Age‐depth model for Basin B plotted with 2σ. Corrected and calibrated ages are shown with grey color. The age based on chironomid head capsules is showed with beige color. The ages obtained from the mixture of terrestrial macrofossils and chironomids are shown with dashed outlines.

Table 7: Accumulation rate at Basin B

Interval Vertical Time interval Time Sedimentation (cm) distance (mm) (years) (years) rate (mm/year) 106−85 80 AD 730 − 860 240 0.6 123−106 170 AD 450 − 730 280 0.6 141−123 180 AD 240 − 450 210 0.9 161−141 200 180 BC – AD 240 420 0.5

48 Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

6.3.2.2 Loss on ignition Loss-on-ignition analysis was carried out between 169 and 75 cm depth. The analyzed sequence consists of clay gyttja, gyttja, clay, reed peat and fen peat. The results are shown as a curve in Figure 30. Loss on ignition gradually increases from the bottom reaching a peak in the lower part of gyttja. Upwards the amount of organic content slightly decreases and then remains stable with minor fluctuations. A sharp decrease can be observed in the clay layer prior to the accumulation of reed peat. More details about the LOI are given in the description of diatom zones.

6.3.2.3 Diatom analysis In the analyzed sediment sequence between 169 and 85 cm depth 128 diatom taxa were Figure 30: Loss on ignition results at Basin identified from the following genera: B. Note that the measurements do not cover Achnanthes (2 taxa), Actinocyclus (1), the entire sequence of the diatom analysis. Amphora (2), Amphipleura (1), Aulacoseira (3), Caloneis (1), Campylodiscus (2), Chaetoceros resting spores (1), Cocconeis (2), Coscinodiscus (1), Cyclostephanos (1), Cyclotella (2), Cymatopleura (1), Cymbella (12), Diploneis (2), Ellerbeckia (1), Eunotia (1), Epithemia (3), Fragilaria (11), Frustulia (1), Grammatophora (1), Gomphonema (10), Gyrosigma (3), Hantzschia (2), Hyalodiscus (1), Mastogloia (2), Melosira (1), Meridion (1), Navicula (18), Neidium (3), Nitzschia (6), Pinnularia (8), Rhabdonema (2), Rhopalodia (2), Rhoicosphenia (1), Stauroneis (4), Stephanodiscus (1), Surirella (6), Tabellaria (2) and Thalassiosira (3). Diatoms are abundant between 150 and 90 cm depth. Diatom preservation is moderate with a high number of corroded valves and fragments in the lower part of the sequence. The occurrence of other siliceous microfossils, e.g. Chrysophyceae stomatocysts and phytoliths, is relatively high. All diatom taxa classified according to their salinity preferences and living conditions are shown in the Appendix 2.

The diagram, showing the relative abundance of diatoms, has been separated in three parts where; the first part shows polyhalobous, mesohalobous, halophilous and indifferent taxa (Figure 31). The second part presents halophobous and rheophilous taxa (Figure 32). The third part is summary diagram where all taxa are shown as groups (Figure 33). Species with abundances below 1% were excluded. Data on depth and lithological stratigraphy as indicated by field observations are included in the diagram. Results from the LOI were also

49 Christos Katrantsiotis incorporated in the final interpretation of the zones. Based on the diatom stratigraphy, three zones can be identified:

Zone 1 (169 ─ 150 cm, 390 BC ─ AD 30) consists of clay gyttja. The organic content increases from c.10 % to 30%. The diatom concentration is relatively low. The diatom flora is dominated by benthic species with scattered occurrence of planktonic taxa, mainly being represented by Aulacoseira ambigua. In terms of salinity, this zone is characterized by a mixture of marine/brackish and freshwater species. Freshwater taxa dominate with c. 70%, represented by Aulacoseira ambigua, Gomphonema acuminatum and Fragilaria capucina. Indifferent taxa contribute with 50% in the lower part of the zone, decreasing upwards. Fragilaria construens, Cocconeis placentula and Epithemia adnata are the most common species. Halophilous species occur with 10%, mainly dominated by Epithemia turgida and Rhoicosphenia abbreviata. The amount of polyhalobous species is extremely low. Mesohalobous species constitute about 10% of the assemblage mainly represented by Cocconeis scutellum, Hyalodiscus scoticus and Melosira lineata. A low proportion of rheophilous species (up to 2%), e.g. Meridion circulare, and aerophilous species (up to 1%), e.g. Hantzschia amphioxys, occur in this zone. Interpretation: The diatom composition in combination with the lithology suggests lowering of water depth and the formation of a shallow and sheltered brackish- freshwater bay or coastal lagoon. This is a stage prior to the final isolation when the water level was close to the isolation threshold. High abundance of freshwater taxa may reflect river influx that could have changed the salinity of lagoon/or bay. The occurrence of rheophilous taxon, i.e. Meridion circulare supports this interpretation. The presence of Aulacoseira ambigua probably indicates the existence of extended open water (cf. Basin A).

Zone 2 (150 ─ 90 cm, AD 30 ─ 830) is composed of gyttja. The organic content increases significantly reaching at the higher values of 80% in the lower part of the zone. Upwards the amount of organic content decreases slightly and remains stable with minor fluctuations. This zone is dominated by mass occurrences of Fragilaria spp, e.g. F. construens and F. brevistriata. They represent 80%, or most, of the diatom flora. The amount of freshwater taxa is high in the lower part of this zone decreasing upwards. Marine or brackish water diatoms are not present. Interpretation: The lower part of this zone corresponds to the final isolation of the basin as the threshold has been uplifted above the average mean sea level. The final isolation is defined at 150 cm depth. This level was dated to 50 BC ─ AD 110 with highest probability c. AD 30. The major event is recorded in the diatom flora as the disappearance of brackish/marine species, the gradual prevailing of Fragilaria spp and the peak in the concentration of freshwater species. Supporting the isolation interpretation is also the increase in organic content (cf. Robertsson & Persson 1989). This coincides with the lithological transition from clay gyttja to gyttja. The significant increase in the amount of organic content in combination with the mass occurrences of benthic species and epiphytic/periphytic diatoms typical for shallow littoral zone is interpreted to represent lower water level and higher biological productivity (cf. Basin A).

50 Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

Zone 3 (90 ─ 85 cm, AD 830 ─ 880) corresponds to reed peat and a thin layer of clay at the boundary between reed peat/gyttja (90 ─ 87 cm depth). The organic content decreases significantly in the transition from gyttja to clay and then rises in the peat reaching 90%. This zone contains low concentration of diatoms. Halophobous taxa comprise more than 80% of the diatom flora, represented by Gomphonema accuminatum and Eunotia spp. The percentage of indifferent taxa decreases upwards. Few fragments of brackish species, e.g. Campylodiscus echeneis and Hyalodiscus scoticus, occur within the clay horizon. Interpretation: The lithology, in conjunction with the diatom composition of this zone, is believed to reflect the gradual infilling of the lake. This event was dated to AD 750 – 950 with highest probability c. AD 850. The low proportion of diatoms may be caused by valve dissolution due to the gradual development of terrestrial conditions (cf. Basin A). The clay horizon probably represents a period of erosion. The fragments of brackish water diatoms within this horizon could have been caused by reworking and redeposition of the frustules from Littorina Sea deposits.

51 Christos Katrantsiotis

CONISS

Total sum of squares of sum Total

Zones

2 3

Rhopalodia gibba Rhopalodia

Navicula rhynchocephala Navicula

Fragilaria pinnata Fragilaria

Fragilaria lapponica Fragilaria

Indifferent

Fragilaria consturens Fragilaria

Fragilaria brevistriata Fragilaria

Epithemia sorex Epithemia

Epithemia adnata Epithemia

Mälby

Ellerbeckia arenaria Ellerbeckia

Diploneis ovalis Diploneis

Cymbella cistula Cymbella

Cyclostephanos dubius Cyclostephanos at point,

20 Halophilous

Cocconeis placentula Cocconeis

Amphora ovalis Amphora

Amphora libyca Amphora

Surirella capronii Surirella gyttja Clay

Rhoicosphenia abbreviata Rhoicosphenia

Navicula capitata Navicula

Mesohalobous parkerii Gyrosigma

Gyttja

Epithemia turgida Epithemia

Nitzschia levidensis Nitzschia

Melosira lineata Melosira

Hyalodiscus scoticus Hyalodiscus Clay

Gyrosigma obscurum Gyrosigma

Chaetoceros spp. resting spores resting spp. Chaetoceros

Diatom Diatom diagram showing the percentage abundance of polyhalobous, mesohalobous, halophilous and

Campylodiscus hiber nicus hiber Campylodiscus

Cocconeis scutellum Cocconeis

Reedpeat

Lithology

Figure Figure 31: saddle the of east B, at basin species indifferent

Depth

170

165

160

155

150

145

140

135

130

125

120

115

110

105 100

Age interval (BC - AD) - (BC interval Age

358 - 78 BC78 - 358

AD 126 - 379 - 126 AD

AD 345 - 549 - 345 AD

AD 668 - 869 - 668 AD

AD 750 - 950 - 750 AD 50 BC - AD 110 AD BC 50-

Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

Rheophilous

CONISS

Aerophilous

Total sum of squares of sum Total

Zones

2 3

Meridion circulare Meridion

Hantzschia amphioxys Hantzschia

Tabellaria flocculosa Tabellaria

Tabellaria fenestrata Tabellaria

Surirella robusta Surirella

Surirella bifrons Surirella

Pinnularia spp Pinnularia

Pinnularia viridis Pinnularia

Pinnularia nodosa Pinnularia

Pinnularia gibba Pinnularia

Navicula viridula Navicula

Navicula radiosa Navicula

Navicula pupula Navicula

Navicula placentula Navicula

Halophobous

Navicula elginensis Navicula

Navicula cari Navicula

Navicula americana Navicula

Mastogloia smithii var. Lacustris var. smithii Mastogloia

Gyrosigma acuminatum Gyrosigma

Gomphonema truncatum Gomphonema

Gomphonema parvulum Gomphonema

Gomphonema angustatum Gomphonema

Gomphonema angustum Gomphonema

Gomphonema acuminatum Gomphonema gyttja Clay

Fragilaria ulna Fragilaria

Mälby

Fragilaria capucina Fragilaria

Gyttja

Eunotia spp Eunotia

Diploneis spp Diploneis

point, at point,

- Cymbella helvetica Cymbella

Cymbella cymbiformis Cymbella

Clay

Cymbella caespitosa Cymbella

Aulacoseira granulata Aulacoseira

Diatom diagram showing the percentage abundance of halophobous and rheophilous basin and species at abundance rheophilous the showing of halophobous percentage diagram Diatom

Aulacoseira crenulata Aulacoseira

Aulacoseira ambigua Aulacoseira

Reedpeat

Lithology

Figure Figure 32: saddle the of east B,

Depth

170

165

160

155

150

145

140

135

130

125

120

115

110

105 100

Age interval (BC - AD) - (BC interval Age

358 - 78 BC 78 - 358

AD 126 - 379 - 126 AD

AD 345 - 549 - 345 AD

AD 668 - 869 - 668 AD

AD 750 - 950 - 750 AD 50 BC - AD 110 AD BC- 50

Christos Katrantsiotis

CONISS

Totalsum squaresof

Zones

4000

2000

Basic sum Basic

Unknown ecology Unknown

Rheophilous

Aerophilous

Mälby

Claygyttja

point, at point,

Halophobous

100

Gyttja

Indifferent Clay

Halophilous

Mesohalobous

Diatom Diatom diagram showing the percentage abundance of all taxa and the variation in the organic

Polyhalobous

(%) at basin B, east of the saddle ofthe east B, atbasin (%)

Reedpeat

Lithology

Figure Figure 33: matter

Depth

170

165

160

155

150

145

140

135

130

125

120

115

110

105 100

Age interval (BC - AD) - (BC interval Age

35878 BC-

AD 126 379 AD -

AD 345 549 AD -

AD 668 869 AD -

AD 750 950 AD - 50 BC - AD 110 50AD BC-

Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

6.4 Evolution of the area

In connection with the Weichselian deglaciation the retreating ice left behind an irregular ground surface with depressions, shallow basins and convex points. Due to the pressure from the ice sheet, the bedrock was submerged forming an open water landscape. As a whole the water depth and the intensity of bottom currents can be considered as the main factors which governed the distribution of sediment. Accumulation of fine-grained sediment, i.e. sandy silt and clay occurred in the deepest parts where calm conditions prevailed whereas coarse-grained sediment was deposited near-shore. The sedimentation spanned over the three youngest Baltic Sea stages; Yoldia Sea, Ancylus Lake and Littorina Sea. The composition of the sediments has change from minerogenic in the lower part to organic strata upwards.

During the brackish phase of the Yoldia Sea, finer particles, clay and silt were suspended in the melt-water and deposited on the bottom as varved glacial clay. Homogeneous postglacial clay was deposited as a cover over the glacial clay during the Ancylus Lake stage. Sedimentation was interrupted by short periods of erosion. As the water depth decreased, sand and gravel, eroded from the surrounding, covered the clay deposits in places. Organic material, derived from algae and other vegetation in the neighborhood was deposited along with the clay as gyttja clay during the early phase of the Littorina Sea. Clay gyttja was probably deposited later as the sea ceased to transport significant amounts of minerogenic sediments (Kjemperud 1986).

The elevated forested areas of till and rocky hills, which surround the area in the north and south, transformed the trail from an open sea strait to a long narrow bay or inlet, open to the east and west. This sheltered position of the valley and the relatively large distance of the site from the open Baltic caused a reduction in the marine influence and increase in freshwater input in the form of groundwater and/or surface water from the surrounding area. Thus, a transition phase to a lacustrine environment should have started prior to the emergence of the saddle-point, i.e. prior to BC/AD (see shore displacement curve; 7.9 paragraph).

Numerous small and shallow basins of varying morphologies were located in this part of section. These basins were separated from each other by threshold areas of different elevations. Initially, the water level was high enough allowing the connection of all basins into a single lake. After the emergence of the saddle-point, i.e. BC/AD, the water level barely covered the isolation thresholds of the basins. The ongoing isostatic uplift resulted in the emergence of the basins distributed east and west of the saddle-point (Figure 34). According to the age-depth models, the final isolation of Basin A occurred around AD 20 while Basin B was isolated around AD 30 (Figure 35).

As the threshold of the basins emerged above the sea level lacustrine sedimentation began. The enhanced inflow of organic material from the surrounding land and high organic productivity led to the deposition of gyttja. The sedimentation took place in a shallow water

Christos Katrantsiotis environment under alkaline conditions. A continuous supply of nutrients from the catchment area, probably due to land-use changes could have enhanced the productivity within the lakes. Thus, water quality changed and aquatic macrophytes developed in response to nutrient supply (cf Håkansson & Regnéll 1993). These conditions in combination with the shallow and narrow morphology of the basins should have led to an extensive littoral zone supporting the expansion of littoral macrophytic vegetation and mostly attached diatoms, e.g. Fragilaria spp.

Due to sediment infilling the lakes become so shallow that peat-forming macorphytes, such as the common reed (Phragmites australis), colonized the organogenic bottom (cf Björck 2010). As a result, the former isolated lake basins were transformed into wetlands overgrown by emergent vegetation. The transition into terrestrial conditions should have been completed c. AD 220 for Lake A, west of the pass-point and c. AD 830 for Lake B, east of the pass-point. The reed peat gave eventually way to fen/carr peat, which covered the whole section. Due to human activities fens have been affected by man-made drainage and agricultural fields.

Figure 34: Map showing the approximate distribution of the lake basins after the emergence of the saddle-point (black circle) and the isolation thresholds.

Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

Figure 35: Development of the area east and west of the saddle-point. The black arrow indicates the saddle-point which emerged c. BC/AD (This age was estimated from the shore displacement curve; see 7.9 paragraph). The blue arrow shows the threshold area of Basin A, which emerged c. AD 20. The brown arrow depicts the threshold area of Basin B after the emergence c. AD 30.

Christos Katrantsiotis

7. Discussion

The lithological investigation revealed that the central part of the Långhundraleden trail consists of four small and shallow basins now covered with peat. To elaborate the paleoenvironment two sediment cores were retrieved from two basins, Basin A and B, east and west of the saddle-point. The analyses of the sequences showed that there is a close correlation between the two sites with respect to litho- and biostratigraphy. Both sequences have been divided into three main zones comprising a regressive succession. These stages include a transitional phase before and after the emergence of the saddle-point, a stage with lacustrine conditions and terrestrial environment.

From the results it can be concluded that the studied basins yielded similar isolation processes and were isolated during the same period. This seems reasonable considering the similar bedrock geology, the close distance between the sites and the fact they are located at the same elevation. Therefore, the coherent results between the basins indicate that the applied methods should be regarded as reliable. Despite this reliability, there are some potential errors and uncertainties that could be connected to the field work and the laboratory process as well as the geographical setting of the studied basins e.g. size, topography and location. These parameters should be considered before making a comprehensive conclusion regarding the development of the central part of Långhundraleden Trail.

7.1. Location of sampling sites The choice of a sampling location is aimed at obtaining the most representative sequence of sediment and peat. Normally, the most optimal sampling site is located in the deepest part of a basin, which is supposed to contain the longest record with maximum thickness of sediment and peat. The determination of this site requires successive cross-section coring. This can allow mapping of the spatial variability of sediment, which can reveal variable facies thicknesses (Long et al. 2011).

In the context of the present study, a longitudinal section was carried out along the ditch, assuming that it would represent the lower part of the valley. Due to time constrains, no vertical sections were made to estimate their north-south extensions of the basins. This increases the risk for collecting sediment cores of not being representative of the overall basin stratigraphy. This is obvious at Basin A where the sediment core was collected from the near-shore area. The sediment core form Basin B was probably retrieved near the deepest of part of the basin. Thus, it is supposed to be the representative sequence. Due to the shallow condition (<1-2m water depth) and the gentle slopes of the former lake basins the difference in the thickness of the sediments between the deepest part and the near-shore area should be c. 0.5 m or less. This could have a minor effect in the final results.

Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

7.2 Determining isolation threshold elevation The highest points of the longitudinal section of Basins A and B were considered as representing the isolation threshold levels. The accurate determination of these levels should also involve cross-section corings (Risberg 1989). Since the valley bottom is narrow and flat this procedure was omitted.

The accurate determination of isolation threshold of the basins is dependent on the accuracy of the leveling instrument (±0.05 m) and the conditions at the threshold. The defining isolation thresholds in both basins seem to be affected by growth of peat and/or human activities in the form of cultivation. The potential error derived from these uncertainties should be c.±0.5 m as determined by Risberg (1989).

7.3 Geographical settings There are some limitations related to the geographical setting of the studied basins e.g. size or topography. Due to shallow conditions (<1-2m water depth) and stagnant water, it cannot be excluded that the basins could have been affected by ice freezing. These conditions could have disturbed or stopped the sedimentation as well as influenced seasonal exchange of freshwater and marine water into the basins (Long et al. 2011). In addition, the gentle slope of the valley floor and the narrow protected valley should have supported an extensive littoral zone. Within this zone human activities could have reworked the sediment, especially in the near-shore area. Furthermore, these types of shallow basins could have been filled with sediment relatively quick, thus, ceased to operate as isolation basins. This could have restricted the ability of the basins to record environmental changes after the isolation event (Long et al. 2011).

7.4 Defining the isolation contact The isolation contact is the horizon in the sediment sequence, which represent the time when the lake was isolated from the sea (Lie et al. 1983). Kjemperud (1986) proposed four types of isolation contacts of which two are relevant to the present study. The sedimentological isolation contact, which constitutes the lowermost one, represent the time during which the sea ceased to transport significant amounts of minerogenic sediments into the basins. This is recorded in the lithostratigraphy as a change from a minerogenic, allochthonous sediment to organic, autochthonous deposit. The diatomological isolation contact represents the time during which the water in the photic zone of a basin became fresh. This is reflected in the diatom assemblage as a change from marine/brackish to freshwater species. It should be kept in mind that the salinity in the photic zone is dependent on a variety of factors including the freshwater input, the size and morphology of the basin as well as its connection to the sea (Selby and Smith 2007). The effects of these factors can complicate the identification of the diatomological isolation contact. The latter records the final isolation of a basin and coincides with the onset of the deposition of gyttja.

Christos Katrantsiotis

When considering the sedimentological isolation contact, there is a clear transition, in the analyzed sequences, from minerogenic deposits e.g. postglacial clay, sand and gravel to more autochthonous and mixed organic/minerogenic sediment. This contact coincides with the development of anoxic bottom water and the onset of the deposition of laminated brown/black clay gyttja in both basins (cf. Long et al. 2011). On the other hand, the diatomological isolation contact recoded above the sedimentological isolation contact seems to be more diffuse due to the indistinct and gradual change in the diatom composition. This can be attributed to the fact that changes in diatom assemblages have been controlled by local conditions rather than sea-level fluctuations. In other words, despite the inflow of brackish-marine water, stronger freshwater influences from the surrounding area probably resulted in freshwater conditions in the basins even prior to the emergence of the saddle-point and the isolation threshold. This is reflected in the diatom stratigraphy as a dominance of indifferent and freshwater taxa with the presence of brackish-marine taxa.

The pre-isolation freshwater conditions make the identification of diatomological isolation contact within bordering basins problematic. In ideal conditions, a typical isolation sequence shows a replacement of marine/brackish by typical freshwater diatoms after the isolation event. Halden (1917) distinguished different isolation sequences from the Littorina Sea. These sequences are determined by local bathymetric factors (Hedenström 2001). In a shallow basin the isolation sequence is characterized by the typical Clypeus flora. In deeper basins the isolation sequence is dominated by other taxa e.g. Navicula peregrina and Chaetoceros spp resting spores. In the studied basins, however, which are supposed to have been shallow the Clypeus flora is weakly developed while the abundance of Navicula peregrina and Chaetoceros spp resting spores are very low. Instead, the isolation is marked by the disappearance of marine/brackish species and the increase and the dominance of indifferent taxa e.g. Fragilaria spp and Cocconeis placentula. The latter, however, is known for its ability to grow under a range of different salinities and cannot be considered as the most accurate indicator for tracing the isolation event. Alternatively, mass occurrences of indifferent taxa could be associated with changes in water quality and chemistry brought about by high fluxes of nutrients into the basins after the isolation (see diatom species distribution). In that sense, the high abundance of indifferent taxa can be used as an indicator for the final isolation. There is a possibility for these taxa to signal long term incursions of brackish water into the basin. This can be attributed to the plane topography, which allowed brackish water to enter the basins during periods of high sea level and/or changing meteorological conditions. Freshwater taxa, on the other hand, cannot be considered as being indicative of the isolation level since their amount displays large fluctuations throughout the sequences. Especially, at Basin B, freshwater taxa decrease abruptly after the isolation. This is associated with the mass occurrences of Fragilaria spp that could mask the amount of freshwater taxa in the diatom assemblage.

It can be concluded that large inflows of freshwater and or/limited inflows of brackish water supports high abundances of freshwater taxa even prior to the final isolation.

Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

Furthermore, it is clear that indifferent taxa can peak before and/or after the final isolation since they have tolerance in a wide range of environment. From above, it can be argued that the level of the disappearance of brackish/marine taxa could be considered as a horizon, which marks the diatomological isolation contact i.e. the final isolation contact.

In general, the presented diatom results seems to be in close agreement with the LOI analysis in both sites, since rise in the organic content almost coincides with the disappearance of marine/brackish water species. One of the most prominent features documented at Basin B is the coincidence between the diatom zone boundaries and lithological boundaries as they were determined in the field. In other words, the lithostratigraphic changes from clay gyttja to gyttja are approximately synchronous with the diatomological isolation contact. This shows that the conditions for sedimentation have changed radically during the isolation phase (cf. Kjemperud 1986). At Basin A, however, the diatomological isolation contact is inconsistent with the changes observed in the lithostratigraphy. In this case, the diatomological isolation contact and rise in the organic matter occurs within the layer of clay gyttja prior to the deposition of gyttja. This probably indicates that the final isolation could have occurred during the deposition of clay gyttja and the upper part of this layer was deposited in a freshwater environment (cf. Robertsson & Persson 1989). It has been assumed, however, that organic sediments begin to accumulate within the basin immediately after the final isolation (Kjemperud 1981). If so, a misinterpretation of the boundary between clay gyttja and gyttja as it was determined in the field could be a most obvious explanation. Alternatively, long term incursions of brackish water probably caused the transportation of minerogenic particles that together with organic compounds caused the deposition of clay gyttja after the final isolation.

7.5 Diatom species distribution The diatom assemblages at the two sites were found to be relatively similar. Three important features can be seen: (1) in terms of salinity; abundant indifferent taxa, (2) regarding the water level; high abundances of littoral shallow-water and epiphytic taxa and (3) with reference to pH; high percentage of alkaliphilous species. A major difference between the two sites is the mass occurrence of Fragilaria spp and the low concentration of freshwater taxa, mainly recorded after the isolation event in Basin B.

The diatom assemblages of the basal parts of the analyzed sequences comprise mixtures of typical freshwater taxa, e.g. Aulacoseira ambigua, with estuary brackish-water diatoms, e.g. Melosira lineata, Nitzschia levidensis, Cocconeis scutellum and Fragilaria fasciculata (cf. Snoeijs 1993; Snoeijs & Vilbaste 1994). Most of the species are attached to plants or/and associated with rocks. Melosira lineata is a widespread taxon in the present-day Baltic Sea decreasing in abundance and/or becoming absent towards the south (Snoeijs 1993). Nitzschia levidensis and Cocconeis scutellum are distributed everywhere in the Baltic Sea with an optimum distribution in the central Baltic (Snoeijs & Vilbaste 1994). Nitzschia levidensis has also been reported in lagoons and closed inlets (Iliev et al. 2005). The flora in the basal parts of the sequences also includes marine species with brackish 61

Christos Katrantsiotis water affinities, e.g. Hyalodiscus scoticus (Grönlund 1988; Snoeijs & Vilbaste 1994). Pienitz et al. (1991) reported the presence of Hyalodiscus scoticus in previously studied brackish lagoons. As a whole, estuary brackish-water and marine/brackish diatoms together with scattered occurrences of taxa representing the Clypeus flora indicate the development of a bay/lagoonal environment with shallow water conditions. The Clypeus flora is normally developed when the sea level reach the altitude of the threshold indicating a lagoonal phase before the isolation of the basin (Miller 1986).

The large amount of freshwater species prior to the isolation event is mainly caused by the input of freshwater. This kind of environment is confirmed by the presence of Meridion circulare, which is characteristic of running freshwater where it is found, attached to stones and plants (Krammer & Lange-Bertalot 1991a). Another common feature is the high frequencies of the halophilous taxon Rhoicosphenia abbreviata, which is one of the most common diatoms along the coast of the present-day Baltic Sea, indicating its affinity for brackish water (Snoeijs 1993). With reference to pH, Rhoicosphenia abbreviata is favored by strong alkaline conditions indicating period of enhanced pH (Cholnoky 1968). Alkaline conditions are also indicated by the high percentages of the alkaliphilous species, e.g. Amphora ovalis (Cholnoky 1968).

The most prominent feature prior to the final isolation in both sites is the high abundance of Aulacoseira ambigua. Other Aulacoseira species, including A. granulata and A. crenulata are well represented in the stratigraphy, especially at Basin A after the isolation event. Overall, Aulacoseira species signifies freshwater conditions and moderately high water levels. A. ambigua is a planktonic taxon, which can grow in small or large lakes (Cleve- Euler 1951; Krammer & Lange-Bertalot 1991a). In that sense the high abundance of A. ambigua prior to the isolation event might be connected to an increase in water depth. This is not valid for the studied basins since the majority of taxa that thrive at the same depths as A. ambigua are benthic. A. ambigua also requires well-mixed conditions to remain in suspension in the water column (Puusepp & Kangur 2010; Poister et al. 2012). In that sense this taxon could indicate open water exposed to winds. Alternatively, the abundance of A. ambigua prior to the isolation event could be used as an indicator of human activities. This taxon has been associated with periods of human colonization and settlement (Pienitz et al. 2006) whereas in other cases with pre-colonization periods (Karst & Smo 1998). Bradbury et al. (2002) reported high abundances of A. ambigua after deforestation and Puusepp & Kangur (2010) suggests that the increase in this species might be attributed to the loss of trees around a water body. This could lead to higher wind exposure of the open-water area, and thus water-column turbulence that favors Aulacoseira species (Bigler 2001; Puusepp & Kangur 2010). In addition, A. ambigua is an alkaliphilous and mesotrophic to eutrophic taxon (Cholnoky 1968). Thus, in connection with human activities, deforestation probably caused inwash of carbonate-enriched deposits triggering an increase in nutrient levels and alkaline conditions within the water body. This environment probably favored the occurrence of A. ambigua.

Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

Another characteristic feature in connection with the isolation event, especially at Basin B, is the mass occurrence of Fragilaria species, mainly being represented by F. construens and F. brevistriata. A dominance of Fragilaria taxa is often observed in studies of Scandinavian lakes and ponds (e.g. Kjemperud 1981; Stabell 1985; Seppä et al. 2000). Although Fragilaria spp often increases in connection with isolation events, there is no clear evidence that the high percentages of these taxa can be connected directly with salinity changes (Stabell 1985; Heinsalu et al. 2000). Stabell (1985) stated that the highest percentages of Fragilaria spp may occur before, during or after the isolation event. At the studied basins at Mälby, the main peak of Fragilaria spp occur after the disappearance of brackish-water taxa and the rise of the organic content, and thus, directly after the isolation. Kjemperud (1981) and Stabell (1985) concluded that the predominance of these taxa could be related to the rapid changes in water chemistry during and after the isolation reflecting the importance of the nutrient availability and catchment processes (Seppä et al. 2000). In general, Fragilaria spp, e.g. F. construens and F. brevistriata, can be abundant in nutrient- poor waters but also in alkaline and eutrophic waters (Cleve-Euler 1952; Cholnoky 1968). Thus, the mass occurrence of Fragilaria spp in the studied basins could be connected to the nutrient availability during and after the isolation (Stabell 1985; Risberg et al. 1996). Nutrient availability could be associated with deforestation and subsequent soil erosion. Fragilaria spp have also been characterized as epiphytic species. Thus, their expansion could be connected with the shallow water and the development of littoral macrophytes (Davydova & Servant-Vildary 1996).

Cocconeis placentula and Epithemia adnata are two indifferent taxa, which are well presented throughout the sediment sequences, especially after the isolation. These species grows exclusively attached to macrophytes and other solid substrata (Snoeijs 1993; Snoeijs & Vilbaste 1994). Therefore, the rapid development of epiphytic taxa, Cocconeis placentula and Epithemia adnata, together with Fragilaria construens, may reflect the expansion of submerged aquatic vegetation and littoral plants as a result of eutrophic conditions, i.e. the increasing availability of nutrients and organic matter and a further decrease in water depth. In addition, Epithemia adnata dominates environments with high phosphorus and low nitrogen concentration (Fairchild & Lowe 1984). These conditions mainly occur in stagnant water with low oxygen concentrations favoring the procedure of nitrification (Schönfelder & Steinberg 2002).

Epithemia turgida is a littoral, epiphytic and brackish-freshwater taxon which prefers alkaline waters (Cholnoky 1968; Snoeijs & Popatova 1995). This taxon occurs in both basins before and after the isolation event. Koçer & Şen (2012) showed the preference for high electrolyte content of Epithemia species. As discussed, the deposits in the study area are calcareous, influenced by the Ordovician limestone from the bottom of the Baltic, east of the Gävlebukten Bay (Strömberg 1989). The presence of Epithemia turgida could have been favorured by a high electrolyte content originating from the lime content in the soil (cf. Bergkvist et al. 2003; Hedenström & Risberg 2003).

Christos Katrantsiotis

Freshwater and epiphytic species, which belongs to the genera Pinnularia, Eunotia and Tabellaria, are represented in the diatom assemblage throughout the sediment sequences. All these species are associated with acidic waters (Cholnoky 1968). Håkansson & Regnéll (1993) suggested that the high amount of acidophilic forms within the alkaline environment may be related to the decrease in pH following the deforestation. The high calcium carbonate of the sediment, however, argues against a decrease in pH (cf. Håkansson & Regnéll 1993). Alternatively, these acidophilic forms are known to live in terrestrial mosses and muds (Poulíčková et al. 2004; Bathurst et al. 2010). Thus, they may have been washed into the basins from the surrounding terrestrial environment where localized nitrification of organic soils may have caused a decrease in pH (cf Håkansson & Regnéll 1993).

In summary, both sites are characterized by high abundances of littoral, epiphytic/epilythic, mainly alkaliphilous taxa. Most of them are indifferent tolerating a wide range of salinities. The shallow and narrow basins must have formed an extensive littoral zone explaining the large influence of littoral diatoms in sediment. Human activities in the catchment area, possibly associated with deforestation and nutrient supply and the consequent expansion of aquatic macorphytes could have enhanced the presence of epiphytic and alkaliphilous taxa. Further investigations, including pollen and metal concentration analysis are required to confirm this pattern and to gain a better understanding of the sedimentary environment and the interaction between human activities and environment.

7.6 Diatom dissolution and preservation The composition of the fossil diatom assemblage is affected by physical, biological and chemical processes including resuspension, erosion, bioturbation and different degrees of dissolution, i.e. taphonomy (Snoeijs & Weckström 2010). As a result, the diatom assemblage cannot fully reflect the former living communities. Poor preservation of diatoms due to silica dissolution and valve fragmentation is common in freshwater and saline systems (Ryves et al. 2006). Fine and poorly silicified valves are easily subject to chemical dissolution and abrasion. This can bias assemblages to more resistant taxa introducing errors in quantitative reconstructions (Barker 1992).

In the present study, the preservation of diatoms is generally moderate. Poor diatom concentration with high number of corroded valves and fragments was mainly observed in lower parts of the cores, prior to final isolation. This probably points to unfavorable environmental conditions such as increasing nutrient depletion or unstable, high-energy and near shore environments (Mills et al. 2009). Further up, shallow and alkaline conditions might have affected the diatom assemblage. Barker (1992) reported silica dissolution under strong alkaline conditions. It can be argued that the obvious dominance of indifferent/freshwater taxa and benthic/epiphytic species prior and after the isolation leaves little doubt about the low salinity and littoral conditions prevailed at the sites before and after the isolation of the basins.

Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

7.7 Radiocarbon ages The principles of radiocarbon dating have been discussed extensively (e.g. Shotton 1972; Olsson 1974, 1983, 1991; Lowe & Walker 1997; Björck & Wohlfarth 2001). Since the introduction of accelerator mass spectrometers AMS it has been possible to obtain more precise radiocarbon dates also from samples with low weights (20 milligrams). However, several variables make it impossible to achieve exact ages. Sediment sequences retrieved from a lake basin contain a variety of autochthonous and allochthonous deposits including animal remains, terrestrial and aquatic plant macrofossils, minerogenic matter and reworked older organic material (Björck & Wohlfarth 2001). Among those components, macrofossils of terrestrial plants are considered as the most reliable material for dating since they photosynthesize directly with the atmosphere and probably have 14C/12C ratios in equilibrium with it (Hedenström & Possnert 2001). The use of terrestrial macrofossils aims at avoiding errors derived from isotopic fractionation, reservoir and hard water effects as is the case when using bulk sediment or aquatic plant remains (Olsson 1974, 1991). Although terrestrial plant macrofossils provide the most accurate dates there are a number of uncertainties that can affect the final ages. These uncertainties can be caused by reworking of terrestrial plant remains through erosion and transportation as well as bioturbation which can introduce younger material into older horizons. Uncertainties are also derived from contamination in the laboratory during the storage or preparation of sample by dust, skin or fungal growth (Björck & Wohlfarth 2001).

The age depth models form both basins show that the dates seem to be concordant with respect to the depths. This could reflect deposition rates without any abrupt changes. Based on the uncertainties discussed above, however, these dates cannot be considered as absolute ages but as an aid in the reconstruction of the environmental changes (Risberg 1991).

7.8 Age difference between chironomids and plant macrofossils In two levels from basin B, chironomids head capsules were dated in addition to terrestrial plant macrofossils. Chironomids are non-biting midges that dominates the bottom in freshwater ecosystems. The head capsules of chironomids are made from chitin, which is a robust polymer and well preserved in freshwater sediment (Lowe & Walker 1997). The chitin is chemically similar and functionally equivalent to the cellulose of plants (Fallu et al. 2004). Chironomids have been used for radiocarbon dating in a numerous research (e.g. Jones et al. 1993; Snyder et al. 1994; Child & Werner 1999; Fallu et al. 2004). However, the results have been contradictory and somewhat ambiguous. Our study shows that chironomids yielded 200 years older ages than the terrestrial plant microfossils. One reason for older ages might be contamination by reworking and redeposition of sediment containing older carbon that could have acted as a food for chironomids (cf Jaffer 2010).

Christos Katrantsiotis

7.9 Shore displacement Lake isolation studies can be considered as a profitable tool in determining the shore displacement history of areas affected by postglacial isostatic uplift (Seppä et al. 2000). The construction of a shore displacement curve is based on the criteria defined by Risberg (1989). The selected basins should be situated at the same isostatic isobase and distributed at different altitudes. The sites should have well-defined topographical isolation threshold levels. The error is normally ±0.5 m. An important criterion is the selection of sites where the isolation contacts have been determined as accurately as possible. The use of diatom analysis has been profitable to indicate the isolation level in the sediment column with an accuracy of a few cm. The determination of the isolation age is the major cause for discrepancies in the order of several hundreds of years (Hedenström & Risberg 2003). AMS 14C dates on terrestrial macrofossils are considered to be the most reliable material despite some uncertainties due to contamination. The lack of well-dated basins can lead to the inclusion of 14C-dated isolations of basins based on bulk sediment samples. In this case, the dating of lake sediment results in too old ages due to reservoir effects. Bulk sediment samples from mires or overgrown lakes are affected by younger rootlets causing too young ages of the sediment underlying the peat deposits (Åkerlund et al. 1995).

7.9.1 Description of sites Based on the criteria defined by Risberg (1989) the studied basins in the Långhundraleden Trail were combined with six previously 14C-dated isolations of basins located in the central-eastern part of Uppland, east of the Ekoln basin, to construct a shore displacement curve. Since central Uppland is an area with local variations in isostatic uplift closely situated sites were selected assuming that they should have similar isostatic uplift histories. The basins are located at a maximum distance of 15-20 km from the central part of Långhundraleden, close to the 4.5 mm/year recent isobase (Åse 1970a; Table 8; Figure 36). It should be noted that the selected sites were studied from various periods and their quality regarding the radiocarbon dates was different. In addition, the difference in the height systems used in different studies was also considered. All altitude values were transposed to RH2000 from RH00 and RH70 by adding 50 cm and 30 cm, respectively (cf. Sund 2010).

Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

Table 8: Sites and basin characteristics used to construct the shore displacement model. The identification of isolation contacts was based on diatom analysis.

Site Study Basin Dated Altitude Isolation age material m a.s.l (BC/AD) (RH2000) 1 Mälby, Basin A Present study Mire Terrestrial 12.4±0.5 AD 20 remains (70 BC – AD 60) 2 Mälby, Basin B Present study Mire Terrestrial 12.3±0.5 AD 30 remains (50 BC – AD 110) 3 L. Plikk (2010) Lake Terrestrial 5.3±0.5 AD 1300±75 Brantshammarssjön remains 4 L. Säbysjön Karlsson & Risberg Lake Bulk 19.1±0.5 1330±200 BC (1998) sediment 5 L. Svartsjön Karlsson & Risberg Lake Bulk 20.5±0.5 1530±105 BC (1998) sediment 6 Slaskerna Karlsson & Risberg Mire Bulk 20.5 ±0.5 1220±200 BC (1998) sediment 7 L. Horssjön Karlsson & Risberg Lake Bulk 34.5 ±0.5 3200±300 BC (1998) sediment 8 L. Halmsjön Karlsson & Risberg Lake Bulk 25.8±0.5 2130±250 BC (1998) sediment

Figure 36: Map showing the geographical distribution of basins used to construct the shore displacement curve. The sites 1-8 are shown in Table 8. Stippled blue line indicates the position of the Långhundraleden Trail. Black lines indicate the recent isobase system in mm/year (Åse 1970a).

Christos Katrantsiotis

Two basins investigated within this project are located in the central part of the Långhundraleden Trail. Both sites, which are covered by peat and situated at approximately the same elevations, present similar isolation ages. Basin A, with a threshold at 12.4 m a.s.l, was isolated c. AD 20 while Basin B at 12.3 m a.s.l. was isolated c. AD 30. The isolation of L. Brantshammarssjön was investigated by Plikk (2010) in connection with a study of the shore displacement in Fjärdhundraland, SW Uppland, and the northern coastal areas of L. Mälaren since 1000 BC. This lake, with a threshold at 5.3 m a.s.l., is located 20 km west of the central part of Långhundraleden Trail. The isolation was estimated to have occurred c. AD 1300. It should be noted that all the sites mentioned above have been treated with the same technique including diatom analysis and AMS radiocarbon on terrestrial macrofossils.

Six sites located few kilometers southwest of the central part of Långhundraleden Trail were investigated by Karlsson & Risberg (1998) in connection to the expansion of Arlanda airport south-east from Uppsala. The type of the studied basins includes lakes and mires (Table 8). In these basins the isolation contacts were determined by means of diatom analysis. 14C-dated isolations on bulk sediment resulted in uncorrected and uncalibrated dates. The original ages obtained from the lakes were corrected for an estimated reservoir age of 200 years (Hedenström & Possnert 2001; Risberg et al. 2005; Karlsson & Risberg 2005). The ages obtained from the overgrowth lakes or mires were not corrected. It was assumed that the contamination due to penetration of younger roots would eliminate or reduce the error caused by reservoir effect (Åkerlund et al. 1995; Risberg et al. 2005). All the dates were calibrated using OxCal v. 4.1. Based on corrected and calibrated ages a time- depth diagram was constructed and a new isolation age was estimated for each basin.

L. Säbysjön is a deep sedimentary basin with isolation threshold at 19.1 m a.s.l. This basin is supposed to yield too old ages due to reservoir effects. The final isolation was estimated to have occurred 1330±200 BC. L.Svartsjön is a shallow sedimentary basin with isolation threshold at 20.5 m a.s.l. and high degree of overgrowth. Slaskerna is now covered with mire. The isolation threshold of this basin was leveled to 20.5 m a.s.l. The latter two types of basins normally give younger ages than those obtained from lakes. Based on the time- depth models the final isolations of L. Svartsjön and Slaskerna were estimated to have occurred c.1220±200 BC and c.1530±105 BC, respectively.

L. Halmsjön is a relatively deep sedimentary basin. The isolation threshold of this lake was leveled to 25.8 m a.s.l. L. Horssjön is a small lake situated in a peat dominated area with isolation threshold at 34.5 m a.s.l. The isolation ages of these two basins show high degrees of uncertainties. In both cases the initial ages obtained from the laboratory do not follow the trend of being younger upwards (Alsø 1998). To achieve chronological models linear interpolations were applied between the calibrated dates (Figure 37). For L. Horssjön the lowermost age was considered too young, probably affected by the downward penetration of younger roots. The ages obtained from L. Halmsjön were corrected for reservoir effects before the calibration and the construction of the age-depth model. Based on these models, the isolation of L. Halmsjön and L. Horssjön should have occurred 2130±250 BC and 3200±300 BC, respectively (Figure 37). 68

Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

Depth Uncorr. Corr &Calibr. (cm) 14C yrs BP 14C yrs BC 955 3805±80 1970±220 959 4150±150 2460±420 963 4045±90 2300±260

Depth Uncorr. Corr & Calibr. (cm) 14C yrs BP 14C yrs BC 531 3975±85 2530±320 535 4475±105 3200±300 541 4135±80 2700±200

Figure 37: Age‐depth models for L.Halmsjön (up) and L Horssjön (down). The black lines show the age-depth model produced by the correction and calibration of original ages. The dashed black lines show the interpreted age-depth model. The dashed red lines show the isolation depth, (based on diatom analysis) and the corresponding isolation age.

Christos Katrantsiotis

7.9.2 Description of the shore displacement curve The shore displacement curve for the central part of Långhundraleden and the surrounding area since 3200 BC is shown in Figure 38. The y-axis represents the leveled threshold altitudes and the x-axis radiocarbon dated biological isolations. The horizontal error bars show uncertainties of the isolation ages. The lengths of bars are based on the standard deviations of the radiocarbon dates (2σ). Vertical error bars depict the altitude uncertainty, which is of the order of ±0.5 m.

Figure 38: Shore displacement curve for the central part of the Långhundraleden Trail and the surrounding area based on observations of isolation contacts from basins listed in Table 8. The dashed black line indicates a linear shore displacement rate of 6.2 mm/year. For comparison of the L4 event two curves from southern Uppland were included. The pink line is modified after Karlsson and Risberg (2005). The grey curve is calibrated and modified after Miller (1982).

The proposed model should be regarded as representing a tentative shore displacement curve due to the uncertainties in the 14C dates of bulk samples. The wider time span in the upper part of the curve is caused by the dating material resulting in less accurate chronological control. Taking into account these uncertainties, the part of the curve covering the period between 3200 BC and AD 1300 could be divided into two segments, which represent two phases of the shore displacement: one linear segment (3200 – 1500 BC), which corresponds to a period of a relatively fast regression with a mean value at 6.4

Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail mm/year and a second one (1200 BC – AD 1300) with a apparent uplift rate at 6.2 mm/year. These two periods seem to be interrupted by a short phase of retarded regression (1500 – 1200 BC). The younger part of the curve, since around AD 1300, probably indicates a period of faster regression with mean value at 7.4 mm/year.

Evidence for impact of L4 event in central Uppland? The suggested halt in the regression might be correlated in time with the L4 transgression event recorded in southern Uppland and Södermanland. An attempt was made to estimate this correlation by comparing the shore displacement curve for the central part of Uppland with the curves for the Stockholm region and the central and northern part of the peninsula Södertörn (Figure 38: Miller 1982; Karlsson & Risberg 2005). The curve constructed by Miller (1982) was based on uncalibrated radiocarbon dates from mires in the Stockholm region. This probably resulted in too young ages, which could have influenced the shore displacement curve. Thus the original curve was calibrated using OxCal v. 4.1. The model developed by Karlsson & Risberg (2005) was mainly based on corrected and calibrated ages from lake sediments in central and northern part of the peninsula Södertörn. Despite these corrections, it cannot be excluded the possibility for a tendency of older dates to be assigned to the isolation events, influencing the configuration of the curve.

The comparison shows that the proposed model for the central Uppland records a period of retarded regression, which coincides fairly well with L4 event as it is recorded by Miller’s curve in the Stockholm region. On the other hand, the model developed by Karlsson & Risberg (2005) seems to record this event 500 years earlier with the peak occurring c. 1900 BC. The dating of various types of accumulations has probably been responsible for this deviation among the models. The lack of transgressional sea level in the central part of Uppland might have been caused by a faster isostatic uplift, which probably compensated the impact of a sea level rise.

The occurrence of a retarded regression phase seems to be supported by the diatom stratigraphy, especially from L.Svartsjön and Slaskerna. The diatom stratigraphy from L. Säbysjön does not show any clear indication of a decrease in the regression rate. The lack of evidence could be attributed to the analyzed sedimentary sequence which probably does not cover the period with the retarded regression.

In L. Svartsjön the period of retarded regression can be discerned as a clear prolonged presence of Chaetoceros spp resting spores prior to the final isolation of the basin (Karlsson & Risberg 1998). Chaetoceros is a large genus of brackish planktonic diatoms. Rich occurrences of Chaetoceros spp resting spores in Baltic Sea sediments have been interpreted as representing rising sea level (e.g. Robertsson 1991). In that sense, their high and prolonged abundance in L. Svartsjön could be used as an indicator for a water level standstill. Some other authors connect the abundance of Chaetoceros spp resting spores with increased nutrient supply (e.g. Miller & Risberg 1990; Andrén 1999; Małgorzata 2011). The eutrophication process brings about a rise in biological production and organic

Christos Katrantsiotis matter, which favor the production of Chaetoceros spp resting spores. In L. Svartsjön, however, the low proportion of organic carbon prior to the isolation does not support the occurrence of eutrophic environment. Alternatively, the vegetive cells of Chaetoceros produce large amounts of resting spores when their living conditions for some reason are under stress. Thus, the dominance of Chaetoceros spp resting spores could be explained by light or nutrient deficiency (Miller & Risberg 1990; Kuwata & Takahashi 1990). It is also possible that Chatoceros spp resting spores could reflect local conditions prior to the isolation, e.g. high salinity and deep water (cf. Hedenström 2001).

In Slaskerna, the period of retarded regression can be seen as a clear dominance of the brackish water taxon Melosira westii prior to the final isolation. This taxon has been used as a marker fossil in association with Littorina Sea transgressions (Miller 1982; Miller & Hedin 1988). In bibliography, however, there are contradictory suggestions regarding the habitat conditions of Melosira westii. It seems that most of the references have classified this species as planktonic (e.g. Miller 1982; Miller & Risberg 1990; Risberg 1991; Robertsson 1991; Vos & Wolf 1988; Miettinen 2011). Other authors regard it as benthic (e.g. Andrén et al. 1999). The record from Slaskerna corresponds in time approximately with those from Helgö in the eastern part of Lake Mälaren where the prolonged isolation sequence, including Melosira westii was interpreted to represent the L4 event (Miller & Hedin 1988). Melosira westii has also been found in studies from northern Uppland, prior to the isolation, where the impact of L4 event was not noticeable (Robertsson & Persson 1989; Hedenström & Risberg 2003). In this case the presence of this taxon could be attributed to local topographical conditions.

Regardless the uncertainties in the habitat of Melosira westii the isolation age of Slaskerna seems to be too young to represent a period of retarded regression. The isolation age with the corresponding isolation threshold altitude give a rate of shore displacement of 6.2 mm/year, which is the same as the rate of uplift during the last 3000 years. If so, local topographical conditions might have favored the growth of Melosira westii. According to Åkerlund (1995) bulk sediments dates from mires could yield 700 years younger ages than the corresponding lake sediments. If this is true, the ages obtained from Slaskerna are probably affected by downward penetration of younger roots. Based on the above, the isolation age of Slaskerna should be c. 1900 BC and correspond to the period of retarded regression. If so, the rich occurrence of Melosira westii could be interpreted as a prolonged standstill in water depth.

There are no other studies to confirm the influence of L4 event in the central part of Uppland. Åse & Bergström (1982) compiled a preliminary shore displacement curve for the Uppsala area based on older studies, showing the impact of L4 event in this area. On the other hand, Hedenström (2001) suggested that the northern limit of the Littorina Sea transgressions was close to Tärnan region east of the Långhundraleden Trail. Based on previous investigations from the surrounding area, Risberg & Alm (2011) suggested that none of the younger transgression phases influenced the area around the trail. It is possible that the shape of the curve between 1500 ─ 1300 BC could be attributed to uncertainties in 72

Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail the dating material resulting in too old ages. If so, this probably causes the deviation of L. Säbysjön and L. Svartsjön from the linear trend. Regardless the uncertainties of the isolation ages, the well correlation of the period of retarded regression with the L4 event as recorded by Miller (1982) in Stockholm region could be used as an evidence to support the influence of the younger Littorina Sea transgression on the central part of Uppland. In any case, there is a need for research to confirm or to reject this scenario.

Evidence for neotectonic movements? There are three potential ‘scenarios’ that could explain the deviation of L. Brantshammarssjön from the linear regression of 6.2 mm/year. The first scenario suggests a period of slower shore displacement rate prior to c.AD 1300. This is followed by a period of rapid apparent uplift rate. The period prior to the isolation of L. Brantshammarssjön coincides with the Medieval Warm Period (AD 800–1300) in the northern hemisphere. Thus, a eustatic sea level rise and/or hydrological factors associated with high water levels in the Ekoln basin, in combination with strong fluctuations of water level over the threshold, are might have caused a decreased shore displacement rate (Plikk, 2010). A regression of sea level during the following Little Ice Age, AD 1550–1850, might be associated with the rapid shore displacement rate since the isolation of L. Brantshammarssjön (Plikk 2010).

According to the second scenario, there is a possibility for irregular bedrock movement that caused faster regression of 7.4 mm/year in this part of Uppland over the last 800 years. The third scenario suggests that the shore displacement curve has followed a linear trend of 6.2 mm/year over the last 3000 years. If so, the deviation of L. Brantshammarssjön from this linear trend could be attributed to errors in the isolation data. L. Brantshammarssjön has a diffuse isolation threshold affected by water level fluctuations and/or anthropogenic activities and hence, may be erroneous (Plikk 2010). The threshold is extended over an almost flat surface with an altitude between c.4.8 and 5.8 m a.s.l. (RH2000). Thus, the altitude of the threshold was determined to c.5.3 m a.s.l. (RH2000) with an uncertainty of c.±0.5 m (Plikk 2010). This wide range of uncertainties causes errors in the calculation of the shore displacement rate. For instance, an isolation threshold at 4.8 m a.s.l. would give an apparent uplift rate of 6.7 mm/ year, which is in close agreement with the uplift rate at Mälby. Considering isolation threshold at 5.3 m a.s.l. the shore displacement rate would be 7.4 mm/year. In addition to potential errors in the determination of isolation threshold, the identification of the isolation contact from L. Brantshammarssjön also involves several uncertainties. Large pre-isolation freshwater input and/or limited inflows of brackish water caused the dominance of freshwater taxa even prior to the final isolation. Thus, the diatom stratigraphy in the sediment sequence does not show any major salinity changes.

There are no studies of isolated basins at lower altitudes in the surroundings of Ekoln basin, which could confirm or reject these scenarios. Due to many uncertainties involved in the identification of the isolation contact and the determination of the altitude of the isolation threshold, the data from L. Brantshammarssjön could be considered doubtful. Therefore it

Christos Katrantsiotis can be argued that a mean shore displacement rate of 6.2 mm/year over the last 3000 years is the most possible scenario.

The age of the emergence of the saddle point; Present study and comparison

Based on the isolation data from Mälby and the present shore displacement curve it can be estimated that the saddle-point along the Långhundraleden Trail, at 12.5 m a.s.l., emerged around BC/AD (Figure 38). This is contradictory to the age estimated from the shore displacement curve west of the Ekoln basin and the northern parts of L. Mälaren (Plikk 2010; Risberg & Alm 2011). These studies suggest that the saddle-point emerged around 250 BC. This discrepancy could be attributed to different isostatic uplift histories east and west of the Ekoln basin. As discussed, the present shore displacement curve was based on closely situated sites, located in and around the central part of the Långhundraleden Trail. Therefore, these sites are supposed to yield similar isostatic uplift history. On the other hand, Plikk’s curve was based on basins located west of the Ekoln basin and north of Stockholm. These basins are supposed to have experienced different isostatic uplift history as compared with the area east of the Ekoln basin. Therefore, it can be concluded that the age BC/AD estimated from the present shore displacement curve seems to be more accurate than the age 250 BC.

Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

7.10 Isostatic variability Even if the main outlines of the relative land uplift in Uppland is known the variability of this uplift is still being discussed. This is because Uppland is an area with a fissure valley landscape where the bedrock topography is pronounced. As a consequence, different bedrock blocks may have been uplifted unequally causing irregular isostatic uplift which could affect the relation between isolation ages at similar altitudes (Risberg et al. 1996; Hedenström & Risberg 1999). If a region has been subject to irregular isostatic uplift, lakes at the same altitude should have been isolated at different times (Risberg 1989). The most obvious indication of this phenomenon is the different isolation ages of the basins at Mälby and Knyllinge fen. According to the present investigation, the basins at Mälby with isolation thresholds at 12.4 and 12.3 m a.s.l. were isolated c. AD 20 and c. AD 30, respectively. Based on these data the average uplift rate at Mälby, east of the Ekoln basin was estimated to 6.2 mm/year. The isolation ages of these basins appear relatively young when comparing to Knyllinge fen, which is supposed to be located close to the same recent isobase as Mälby, 20 km west from the Ekoln basin (Figure 39; Åse 1970a). The isolation of Knyllinge fen, with a threshold altitude at 12.5 m a.s.l. occurred c. 250 BC (Plikk 2010). These data give an apparent uplift rate of c.5.6 mm/year. Therefore, if the dates are correct it can be argued that the basins at Mälby and Knyllinge fen, which are at the same altitude, have been isolated at different times indicating different isostatic uplift rates, east and west of the Ekoln basin.

Knyllinge fen appears to have similar uplift history as two basins located north of Stockholm; L. Gullsjön at c.16 m a.s.l. and L. Fjäturen at c.10 m a.s.l. (Figure 39). The isolation of L. Gullsjön and L. Fjäturen occurred c.850±100 BC and AD 150±100, respectively (Karlsson & Risberg 2005). These data give an average shore displacement rate of c.5.6 mm/year. From the above, it is obvious that L. Gullsjön L. Fjäturen and Knyllinge fen could fit into the same shore displacement curve indicating a uniform shore displacement in a southeast-northwest direction (Figure 40).

L. Brantshammarssjön is located close to the same recent isobase as Knyllinge fen and Mälby, east of the Ekoln basin (Figure 39). As discussed, the uncertainties in the isolation data of the basin cause a large error in the estimated uplift rate with minimum and maximum values ranging from 6.7 to 8.1 mm/year. Regardless the uncertainties, however, the low altitude of the isolation threshold (≥4.5 m a.s.l.) and the relatively young isolation age (≥AD1300) suggest that the apparent uplift rate in this area should be higher than 6.0 mm/year.

The studied basins at Mälby and L. Brantshammarssjön appear relatively young when compared to Knyllinge fen and the shore displacement curve from southwestern Uppland (Figure 40). This probably suggests that the central part of the Långhundraleden Trail and the surrounding area, east of the Ekoln basin have experienced faster rebound in comparison with the northern coastal areas of L. Mälaren, west of the Ekoln basin and the area, north of Stockholm.

Christos Katrantsiotis

Figure 39: Map showing the location of Knyllinge fen, L. Gullsjön, L. Fjäturen. L. Brantshammarssjön and the basins at Mälby (black circles).

Figure 40: The shore displacement curve constructed in this study (dashed grey line) compared to the shore displacement curve for the area west of the Ekoln basin and the northern parts of L. Mälaren, west of the Ekoln basin (Plikk 2010).

Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

An important question is whether the observed anomalies are triggered by irregularities in land uplift or misinterpretations of the isolation data. It should be stressed that the same method including diatom analysis and radiocarbon dating of terrestrial plant remains was applied to all of the basins. L. Gullsjön and L. Fjäturen, as well as Knyllinge fen, seems to have well-defined isolation contacts and well-dated isolation sequence. The determination of the isolation threshold of L. Gullsjön and L. Fjäturen may involve some uncertainties since ditching activities has modified the nature of the threshold morphology (Karlsson & Risberg 2005). The basins investigated at Mälby have more or less prolonged isolation stages duo to the large pre-isolation freshwater input. The isolation contacts, however, are clear and the isolation levels are well-dated.

It can be concluded that the pattern described above cannot be explained by systematic errors in the dating method or misinterpretation of the isolation data. It is also obvious that the published isobases seem to be inaccurate for this part of Uppland since they cannot explain the isolation ages and corresponding altitudes of the basins in relation to their geographic distribution. Since the basins are situated in a relatively pronounced topographic landscape it can be argued that the area has been subjected to small-scale irregular isostatic uplift. If so, this anomaly probably caused a redirection of the isobases in the central part of Uppland over the last 3000 years.

To assess the proposed change in the direction of isobases all the basins with the corresponding uplift rates described above were put on the same map where an attempt was made to redraw the isobases (Table 9; Figure 33). The calculation of the uplift rate was based on the formula R= H / T where R = rate of uplift in mm/year, H = isolation threshold in mm (RH2000), T = isolation age (BP)

The results suggest that the pattern of the isostatic uplift during the last 3000 years is different to the recent uplift (Figure 41). To stress this discrepancy the proposed isobase system is compared with recent isobases as determined from Ussisoo (Åse 1970a). According to the proposed isobase system, the rate of uplift northeast of Enköping has been 5.6 mm/years, which is the almost the same as the rate of uplift just north of Stockholm. On the other hand, the uplift rate in the Arlanda region and the central part of Långhundraleden Trail, east of the Ekoln basin, has been c. 6.2 mm/year. From the above, it can be argued that the isobases for 5.5 and 6.0 mm/year uplift should have ellipsoid shapes sloping southwards indicating that irregular uplift has occurred northeast of Lake Mälaren during the last 3000 years. Since the rate of uplift is increasing towards the north, it can also be suggested that the isobase for 6.5 mm/year could be placed close to Uppsala. Thus, the maximum difference in the isostatic uplift rate between northern and southern part of the Långhundraleden Trail inferred from the model should be in the order of 1 mm/year. If so, the northern part of the trail has been uplifted 2 m more than the southern part.

Christos Katrantsiotis

The Ussisoo’s isobase system is based on data from mareograph-observations along the coast of Sweden and repeated precise levelings in the interior. According to this model, Knyllinge fen, L. Brantshammarssjön and Mälby should have similar isostatic uplift rates for the last hundreds of years since they are located close to the recent isobase of 4.5 mm/year. If so, all sites should fall on the same shore displacement curve. The shore displacement at Stockholm, according to Ussisoo, has a numerical figure of just above 4.0 mm/years and at Uppsala c.5 mm/year. The present-day uplift in the central part of Långhundraleden has been estimated to be about 4.5 mm /year, i.e. slightly higher in the northern parts. These values are lower than the values inferred from the proposed model. The discrepancy can be attributed to the fact that Ussisoo’s model takes into account the last hundreds of years for the reconstruction of the recent land uplift whereas the proposed model covers a longer period. As a whole it is can be argued that the irregularities in land uplift that has occurred in the central part of Uppland are not well explained by the Ussisoo’s isobase system. The reason for that could be small-scale irregular isostatic uplift that probably triggered a redirection of the isobases over the last 3000 years as it was proposed.

The complicated bedrock structure of L. Mälaren area is dominated by major fault lines orientated in a NW-SE direction forming different bedrock blocks. The division could cause different blocks to have different isostatic uplift histories. The study sites used to construct the shore displacement curve are situated on or close to the block called Odensala, which is located southeast of Uppsala (De Geer E.H. 1948). This block is delimited in the north by the elongated watershed Långhundraleden Trail where the studied basins at Mälby are located in and in the west by the pronounced fault-line of the Ekoln basin. It can be argued that this block has been subject to irregular small-scale movements along old fracture zones causing the presumed land uplift anomalies. In particular, this block seems to have been uplifted with a faster rate, c.6.2 mm/year, than the area located west of the fault- line of the Ekoln basin. Furthermore, if the isolation data from L. Brantshammarssjön are correct then the uplift rate for this block should be much higher, probably in the order of 7.4 mm/year for the last 800 years. De Geer E.H. (1948) combined the single minor bedrock blocks into larger blocks along main fissure lines mainly sloping towards SE. From this investigation it can be concluded that southern Uppland and the northern coastal areas of L. Mälaren belong to the same bedrock block. This can explain the pattern derived from Figures 40 & 41 where it is indicated that southern Uppland and the region around Enköping should have a uniform shore displacement history.

The present investigation shows that there is strong evidence to propose the likelihood of irregular small scale in the central part of Uppland over the last 3000 years. If this scenario is true it caused the bedrock block located east of the fault-line of the Ekoln basin to be uplifted with higher rate than the area west of the basin. Further investigations are required to confirm these uplift anomalies, which could have important implications in the stability of the bedrock for storage of nuclear waste products and archaeological research regarding land-sea transitional settings, trade routes and the location of settlement at different periods. 78

Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

Table 9: Sites and data used to calculate the rate of uplift in different parts of Uppland. The identification of isolation contacts was based on diatom analysis. The isolation ages were based on radiocarbon dating of terrestrial plant macrofossils. In Slaskerna the dating was based on bulk sediments. The altitudes refer to RH2000.

Site Study Basin Isolation threshold Isolation age Uplift rate m a.s.l (RH2000) BC/AD (mm/yr) 1 Mälby, Basin A Present study Mire 12.4 ±0.5 AD 20 6.2±0.2 (70 BC – AD 60) 2 Mälby, Basin B Present study Mire 12.3 ±0.5 AD 30 6.2±0.2 (50 BC – AD 110) 3 Slaskerna Karlsson & Mire 20.5 ±0.5 1220±200 BC 6.3±0.4 Risberg (1998) 4 L. Plikk (2010) Lake 5.3 ±0.5 AD 1300±75 7.4±0.7 Brantshammarssjön 5 Knyllinge fen Plikk (2010) Mire 12.8 ±0.5 250±100 BC 5.6±0.3

6 L. Fjäturen Karlsson & Lake 10.3.±1 AD 150±100 5.5±0.3 Risberg (2005) 7 L.Gullsjön Karlsson & Lake 16 .3 ±0.5 850±100 BC 5.7±0.2 Risberg (2005)

Figure 41: Map showing the proposed isobase system for the last 3000 years (black lines) compared to the recent isobase system constructed by Ussisoo (yellow lines; published in Åse 1970a). Sites 1-9 are shown in Table 9. Numbers refer to average uplift rates in mm/yr. The uplift rate 7.4 mm/yr may be erroneous or indicate a period with anomalous trend (see text).

Christos Katrantsiotis

8. Conclusions

Based on the goals of this thesis, the conclusions can be summarized in the following way:

1. The central part of the Långhundraleden Trail consists of four shallow basins of varying morphologies. The basins are now covered with peat as a result of infilling and overgrowth of former lakes.

2. The emergence of the saddle-point, i.e. 12.5 m a.s.l, was estimated to have occurred c. BC/AD. The final isolation of Basin A, west of the saddle-point occurred c. AD 20. The lake was filled in with sediment c.200 years later. Basin B located east of the saddle- point was isolated c. AD 30. This lake was filled in with sediment 800 years later.

 Based on the lithological characteristics of the sediment and the diatom results three major stages can be identified in the evolution of the area, east and west of the saddle-point. These stages include a lagoonal phase, a freshwater stage and terrestrialization.

 A transition to a lacustrine environment should have started prior to the emergence of the saddle-point, since the sheltered position of the valley caused a reduction in the marine influence and increase in freshwater input from the surrounding area.

 After the isolation of the basins, the sedimentation took place in a shallow water environment under alkaline conditions with high nutrient supply.

3. The shore displacement curve for the central part of the Långhundraleden Trail and the surrounding area, i.e. east of the Ekoln basin, shows an average rate of c.6.2 mm/yr since 3200 BC. The trend is regressive but from c.1500 BC to 1200 BC there are indications of a somewhat retarded shore displacement. This period is tentatively correlated with L4 transgression event recorded by Miller (1982) in Stockholm region.

 The rate of apparent land uplift east of the Ekoln basin has been 0.6 mm/year faster when compared to the average shore displacement rate of 5.6 mm/year in the northern part of L. Mälaren, west of the Ekoln basin and the area north of Stockholm, during the last 3000 years. As the area is dominated by a fissure valley landscape, this discrepancy can be attributed to irregular bedrock

Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

9. Acknowledgements

I would like to thank Gunilla Larsson, a marine archaeologist at the Department of Archaeology and Ancient History, Uppsala University, for instigating this project. I would also like to thank my supervisor Jan Risberg at the Department of Physical Geography and Quaternary Geology, Stockholm University, for assisting and helping me in field work, laboratory work and writing. Thanks also to Gunilla Larsson, Edvard Petersson and Jan Pietroń for helping out in the field work. I would like to thank Mats Regnell at the Department of Physical Geography and Quaternary Geology, Stockholm University, for indispensable help with macrofossil identification. Last but not least I would like to thank Göran Alm, at the Department of Physical Geography and Quaternary Geology, Stockholm University, for the construction of digital elevation model of the study section. The core from Basin A was retrieved by Jan Risberg, Linnéa Hedenberg Muje, Carl Lindgren, Jan Wirstad, Gunilla Larsson and Göran Alm in 2010. Material for dating from this core was collected by Anna Plikk. Financial support to cover field work and AMS datings were granted by the Berit Wallenberg foundation to Gunilla Larsson within the project "Strandlinjer längs Långhundraleden".

10. References

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11. Appendix 1: Coordinates (X&Y), altitude (Z in m a.s.l.) and lithostratigraphy of coring sites

Coring site 1 Coring site 9 Coring site 17 X=6625474.063 Y=153074.621 X=6625334.604 Y=153888.875 X=6625332.280 Y=154386.344 Z=12.14 m a.s.l. Z=12.07 m a.s.l. Z=11.95 m a.s.l. 12.14─11.64 Fluvial deposits: 12.07─11.87 Fen peat 11.95─11.10 Carr peat clay and silt 11.87─11.82 Sand 11.10─10.78 Gyttja 11.64>Gyttja clay 11.82─10.87 Gyttja clay 10.78─10.60 Clay gyttja with 10.87─10.12 Postglacial clay Vaucheria Coring site 2 10.12>09.57 Glacial clay 10.60─10.12 Gyttja clay X=6625466.026 Y=153176.190 10.12─10.09 Sand and gravel Z=12.02 m a.s.l. Coring site 10 10.09>09.45 Glacial clay 12.02>11.32 Gyttja clay X=6625324.995 Y=153990.526 Z=12.27 m a.s.l. Coring site 18 Coring site 3 12.27─11.77 Fen peat X=6625333.576 Y=154436.772 X=6625401.009 Y=153362.244 11.77─11.72 Sand Z=12.03 m a.s.l. Z=12.37 m a.s.l. 11.72─10.27 Postglacial clay 12.03─11.43 Carr peat 12.37>11.67 Gyttja clay 10.27>09.77 Glacial clay 11.43─11.18 Reed peat

Coring site 4 11.18─10.60 Gyttja Coring site 11 10.60─10.18 Clay gyttja with X=6625319.509 Y=153545.191 X=6625316.253 Y=154034.092 Z=12.10 m a.s.l. Vaucheria Z=12.09 m a.s.l. 10.18>08.83 Gyttja clay 12.10─11.70 Fen peat 12.09─11.59 Fen peat 11.70─10.88 Clay gyttja with 11.59─11.57 Sand Coring site 19 Vaucheria 11.57─9.34 Postglacial clay X= 6625321.817 Y=154535.801 10.88─10.85 Sand 09.34>09.09 Glacial clay Z=11.95 m a.s.l. 10.85─8.60 Postglacial clay 11.95─10.85 Carr peat 08.60>08.10 Glacial clay Coring site 12 10.85─10.63 Reed peat

X=6625316.035 Y=154084.993 10.63─10.35 Gyttja Coring site 5 Z=11.99 m a.s.l. X=6625328.396 Y=153644.400 10.35─09.95 Clay gyttja 11.99─11.29 Fen peat 09.95─09.65 Gyttja clay Z=12.08 m a.s.l. 11.29─11.14 Reed peat 12.08─11.78 Fen peat 09.65─09.60 Sand and gravel 11.14─10.94 Gyttja 09.60>09.45 Glacial clay 11.78─11.48 Gyttja clay 10.94─10.79 Clay gyttja 11.48─11.23 Alternating layers of 10.79─10.49 Sand Coring site 20 sand and clay 10.49─09.14 Post glacial clay X=6625305.272 Y=154636.409 11.23─09.09 Postglacial clay 09.14>Glacial clay Z=12.05 m a.s.l. 09.09>08.08 Glacial clay 12.05─11.05 Carr peat Coring site 13 Coring site 6 11.05─10.50 Reed peat X=6625318.444 Y=154136.139 10.50─10.30 Gyttja with coarse X=6625333.331 Y=153693.782 Z=11.83 m a.s.l. Z=11.56 m a.s.l. remains 11.83─11.16 Fen peat 10.30─09.65 Gyttja clay 11.56─11.31 Fen peat 11.16─11.06 Gyttja 11.31─09.83Reed peat 09.65─09.55 Sand and gravel 11.06─11.00 Gyttja clay 09.55>08.75 Glacial varved clay 09.83─09.21 Gyttja 11.00─10.90 Sand and gravel 09.21─08.63Clay gyttja 10.90>10.33 Postglacial clay Coring site 21 08.63─07.26 Gyttja clay X=6625287.969 Y=154738.402 07.26─07.25 Stony/gravelly sand Coring site 14 Z=12.11 m a.s.l. 07.25>07.06 Glacial clay X=6625319.456 Y=154185.898 12.11─11.01 Fen peat Z=11.92 m a.s.l. Coring site 7 11.01─10.81 Reed peat 11.92─11.42 Fen peat 10.81─10.61 Gyttja X=6625354.370 Y=153739.651 11.42─11.22 Clay gyttja/gyttja clay Z=11.63 m a.s.l. 10.61─10.36 Gyttja with plant 11.22─11.10 Sand and gravel remains 11.63─11.13 Fen peat 11.10─10.12 Postglacial clay 11.13─10.03 Reed peat 10.36─10.16 Gyttja with coarse 10.12>09.42 Glacial clay plant remains 10.03─09.88 Gyttja 09.88─09.61 Reed peat Coring site 15 10.16─09.90 Clay gyttja 09.61─09.55 Gyttja X=6625320.789 Y=154235.450 09.90─09.29 Gyttja clay 09.55─09.45 Reed peat Z=11.97 m a.s.l. 09.29─09.23 Sand and gravel 09.45─08.93 Gyttja 11.97─11.47 Fen peat 09.23>08.61 Glacial clay with diffuse varves 08.93─08.73 Clay gyttja 11.47─11.22 Clay gyttja/gyttja clay 08.73─07.93 Gyttja clay 11.22─11.12 Sand and gravel Coring site 22 07.93─07.88 Gravelly sand 11.12─10.57 Postglacial clay X=6625272.190 Y=154833.438 7.88>7.63 Glacial clay 10.57>09.97 Glacial clay Z=12.37 m a.s.l.

Coring site 8 Coring site 16 12.37─11.72 Fen peat X=6625356.131 Y=153789.777 X=6625331.380 Y=154336.626 11.72─11.65 Reed peat Z=11.93 m a.s.l. Z=12.03 m a.s.l. 11.65─11.47 Gyttja 11.93─11.23 Fen peat 12.03─11.33 Carr peat 11.47─11.43 Clay gyttja 11.23─10.78 Gyttja, coarse detritus 11.33─11.03 Clay gyttja with 11.43─11.32 Reed peat 10.78─10.70 Clay gyttja Vaucheria 11.32─11.23 Gyttja 10.70─10.58 Gyttja clay 11.03─10.56 Gyttja clay 11.23─10.92 Clay gyttja 10.92>10.87 Gyttja clay 10.58─10.31 Sand 10.56─10.55 Sand and gravel 10.31─09.33 Postglacial clay 10.55> Glacial clay 09.33─09.23 Glacial clay

09.23> Bedrock or boulder

Christos Katrantsiotis

Coring site 23 (sampling site) Coring site 30 Coring site 38 X=6625263.134 Y=154882.369 X=6625252.853 Y=155547.522 X=6625166.905 Y=156247.009 Z=12.81 m a.s.l. Z=12.29 m a.s.l. Z=12.46 m a.s.l. 12.81─12.16 Carr peat 12.29─11.89 Carr peat 12.46─11.86 Anthropogenic filling 12.16─11.93 Reed peat 11.89─11.69 Clay gyttja 11.86─11.36 Postglacial clay 11.93─11-86 Gyttja 11.69─10.49 Gyttja clay with 11.36>10.46 Glacial clay 11.86─11.56 Clay gyttja Vaucheria in the 11.56─11.41 Gyttja clay upper part Coring site 39 11.41─11.38 Sand and gravel 10.49>10.29 Postglacial clay with X=6625161.750 Y=156329.577 11.38>10.81 Glacial clay gravel and stones in Z=12.37 m a.s.l. the upper part 12.37─12.17 Anthropogenic filling Coring site 24 12.17─12.07 Carr peat X=6625258.553 Y=154982.469 Coring site 31 12.07─11.97 Sand with a big Z=12.59 m a.s.l. X=6625233.422 Y=155594.604 boulder and stones 12.59─12.09 Carr peat Z=12.41 m a.s.l. 11.97─11.67 Postglacial clay 12.09─11.49 Clay gyttja 12.41─12.16 Fen peat 11.67>11.37 Glacial clay 11.49─11.32 Gyttja clay 12.16─11.76 Gyttja clay 11.32─11.29 Sand and gravel 11.76─11.71 Sandy gravel Coring site 40 11.29─10.69 Glacial clay 11.71>10.91 Glacial clay X=6625148.143 Y=156428.849 10.69> Bedrock or boulder Z=12.25 m a.s.l. Coring site 32 12.25─11.75 Anthropogenic filling Coring site 25 X=6625224.061 Y=155706.350 11.75─11.60 Gyttja clay X=6625250.015 Y=155084.632 Z=12.58 m a.s.l. 11.60─11.55 Sand Z=12.80 m a.s.l. 12.58─12.28 Fen peat 11.55>11.25 Glacial clay 12.80─12.50 Carr peat 12.28─12.08 Gyttja clay 12.50─12.40 Sand and 12.08─11.68 Sand Coring site 41 gravel/stones 11.68─11.33 Postglacial clay with X=6625132.212 Y=156532.054 12.40> Postglacial clay with sand silt and sand layers Z=12.28 m a.s.l. layers 11.33 >11.08 Glacial clay 12.28─11.78 Anthropogenic filling 11.78─11.63 Fen peat Coring site 26 Coring site 33 11.63─11.53 Gyttja clay with iron X=6625246.609 Y=155184.385 X=6625212.547 Y=155882.362 precipitation Z=12.42 m a.s.l. Z=12.32 m a.s.l. 11.53─11.28 Gyttja clay 12.42─11.80 Carr peat 12.32─11.92 Fen peat 11.28─11.18 Sand 11.80─11.57 Gyttja clay 11.92─11.50 Gyttja clay 11.18>10.78 Glacial clay 11.57─11.52 Sand and gravel 11.50─11.27 Postglacial clay with 11.52─11.45 Postglacial clay with silt and sand layers Coring site 42 sand layers 11.27>10.82 Glacial clay X=6625107.995 Y=156635.616 11.45─11.42 Glacial clay Z=12.43 m a.s.l. Coring site 34 12.43─11.93 Anthropogenic filling Coring site 27 X=6625208.172 Y=155969.048 11.93─11.73 Gyttja clay with iron X=6625243.345 Y=155287.518 Z=12.57 m a.s.l. precipitation Z=11.84 m a.s.l. 12.57─11.97 Fen peat 11.73─11.48 Gyttja clay 11.84─11.54 Carr peat 11.97─11.84 Gyttja clay 11.48─11.33 Sand 11.54─11.04 Reed peat 11.84─11.77 Sand 11.33>10.93 Glacial clay 11.04─10.99 Vaucheriagyttja 11.77─11.47 Postglacial clay with 10.99─10.34 Gyttja, coarse detritus silt and sand layers Coring site 43 10.34─10.04 Clay gyttja 11.47>11.07 Glacial clay X=6625045.304 Y=156806.632 10.04─09.91 Gyttja clay Z=12.03 m a.s.l. 09.91─09.74 Sand and gravel Coring site 35 12.03─11.03 Anthropogenic filling X=6625182.376 Y=156106.780 11.03─10.93 Clay gyttja with wood 09.74>08.84 Glacial clay Z=11.99 m a.s.l. pieces Coring site 28 (sampling site) 11.99─11.34 Fen peat 10.93─10.73 Gyttja clay X=6625235.996 Y=155388.087 11.34─11.27 Reed peat 10.73─10.53 Sand and gravel Z=11.69 m a.s.l. 11.27─11.01 Gyttja 10.53>10.03 Glacial clay 11.69─11.39 Fen peat 11.01─10.64 Clay gyttja Coring site 44 11.39─10.74 Reed peat 10.64─10.60 Sand X=6625050.608 Y=156858.647 10.74─10.79 Clay 10.60>9.99 Glacial clay Z=11.80 m a.s.l. 10.79─10.04 Gyttja Coring site 36 11.80─11.05 Anthropogenic filling 10.04─09.77 Clay gyttja X=6625179.679 Y=156145.946 11.05─10.85 Fen peat 09.77─09.69 Gyttja clay Z=12.39 m a.s.l. 10.85─10.45 Reed peat with Alnus 09.69>08.69 Postglacial clay 12.39─11.71 Fen peat with sand 10.45─10.30 Reed peat mixed with Coring site 29 11.71─11.64 Gyttja clay with sand gyttja X=6625233.705 Y=155483.941 11.64>11.39 Glacial clay 10.30─09.95 Clay gyttja

Z=11.84 m a.s.l. 09.95─09.55 Gyttja clay Coring site 37 09.55─09.50 Sand and gravel 11.84─11.09 Carr peat X=6625168.326 Y=156234.002 11.09─10.99 Gyttja/clay gyttja 09.50>09.00 Glacial clay with few Z=12.62 m a.s.l. dropstones 10.99─10.89 Vaucheriagyttja 12.62─11.92 Anthropogenic filling 10.89─10.84 Gyttja clay 11.92─11.42 Postglacial clay 10.84─10.82 Sand 11.42>10.62 Glacial clay 10.82> postglacial and glacial clay

Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

Coring site 45 Coring site 53 X=6625054.749 Y=156910.331 X=6624983.931 Y=157791.888 Z=11.61 m a.s.l. Z=11.40 m a.s.l. 11.61─11.11 Anthropogenic filling 11.40─10.45 Gyttja clay 11.11─10.61 Reed peat with Alnus 10.45─10.30 Sand

11.61─10.56 Clay gyttja 10.30─10.12 Sandy, gyttja clay 10.56─10.51 Gyttja 10.12─10.07 Coarser sand 10.51─10.26 Clay gyttja 10.07─06.15 Postglacial clay 10.26─10.01 Gyttja clay 06.15>06.10 Glacial clay 10.01─09.97 Sand and gravel 09.97>09.11 Glacial clay with few Coring site 54 dropstones X=6624977.159 Y=157842.910 Z=11.41 m a.s.l. Coring site 46 11.41─10.71 Gyttja clay X=6625058.004 Y=156961.463 10.71─10.61 Sand Z=11.95 m a.s.l. 10.61─10.01 Gyttja clay 11.95─11.75 Anthropogenic filling 10.01─09.86 Alternating layers of 11.75─11.45 Fen or carr peat silt, sand and clay 11.45─10.93 Clay gyttja 09.86>08.91 Postglacial clay 10.93─10.87 Gyttja clay with sand and gravel layers Coring site 55 10.87─10.80 Sand and gravel X=6624982.604 Y=157892.751 10.80─10.53 Postglacial clay Z=11.37 m a.s.l. 10.53>09.95 Glacial varved clay 11.37─10.97 Gyttja clay 10.97─10.87 Sand Coring site 47 10.87─08.86 Laminated gyttja clay X=6625061.928 Y=157014.196 with shell fragments Z=11.73 m a.s.l. 08.86─08.72 Sand 11.73─11.13 Fen peat with stones 08.72>08.37 Postglacial clay with 11.13─10.85Gyttja shell fragments 10.85─10.76 Clay gyttja 10.76─10.23 Gyttja clay Coring site 56 10.23─10.20 Sand and gravel X=6624985.582 Y=157944.315 10.20> 09.73Glacial clay Z=11.40 m a.s.l. 11.40─10.90 Gyttja clay Coring site 48 10.90─10.80 Sand X=6625062.164 Y=157061.165 10.80─08.92 Laminated gyttja clay Z=11.68 m a.s.l. with shell fragments 11.68─11.18 Carr peat 08.92─08.73 Alternating layers of 11.18─11.03 Reed peat silt, sand and clay 11.03─10.73 Gyttja 08.73─07.40 Postglacial clay with 10.73─09.63 Clay gyttja sand, shell fragments 09.63─09.43 Gyttja clay with vaucheria Coring site 57 09.43─09.38 Sand X=6624985.257 Y=157991.585 09.38─09.33 Sandy gravel Z=11.59 m a.s.l. 09.33─09.13 Postglacial clay 11.59─10.59 Gyttja clay 10.59>08.10 Postglacial clay 09.13 >08.68 Glacial clay Coring site 58 Coring site 49 X=6624978.851 Y=158099.623 X=6625059.824 Y=157160.837 Z=11.54 m a.s.l. Z=11.53 m a.s.l. 11.54>09.54 Postglacial clay 11.53─11.03 Gyttja clay 11.03─10.98 Sand and gravel Coring site 59 10.98─10.53 Postglacial clay with X=6624982.114 Y=158190.001 shell fragments Z=11.14 m a.s.l. 10.53>09.53 Glacial clay 11.14>08.14 Postglacial clay

Coring site 50 Coring site 60 X=6625058.034 Y=157356.747 X=6624989.065 Y=158397.053 Z=11.63 m a.s.l. Z=11.41 m a.s.l. 11.63>11.23 Gyttja clay 11.41>08.41 Postglacial clay

Coring site 51 Coring site 61 X=6625031.955 Y=157545.562 X=6624893.788 Y=158572.803 Z=11.44 m a.s.l. Z=11.80 m a.s.l. 11.44─11.09 Gyttja clay 11.80>08.80 Postglacial clay 11.09─11.01 Sand 11.01>10.44 Postglacial clay

Coring site 52 X=6625008.920 Y=157694.521 Z=11.33 m a.s.l. 11.33─10.88 Gyttja clay 10.88─10.70 Sand 10.70─10.33 Postglacial clay

Christos Katrantsiotis

12. Appendix 12 Ecological grouping of diatoms on the basis of salinity and habitat (Basin A & B)

Polyhalobous, benthic Halophilous, benthic Achnanthes brevipes Agardh, 1824 Anomoeoneis sphaerophora (Ehrenberg) Pfitzer, 1871 Achnanthes hungarica Grunow in Cleve & Grunow, 1880 Amphora pediculus (Kützing) Grunow, 1880 Cocconeis scutellum Ehrenberg, 1838 Caloneis amphisbaena (Bory) Cleve, 1894 Cymatopleura elliptica v. hibernica (W. Smith) Van Heurck, Caloneis tenuis (Gregory) Krammer, 1985 1896 Cymatopleura solea (Brébisson) W. Smith, 1851 Diploneis smithii (Brébisson) Cleve, 1894 Cymatopleura solea v. apiculata (W. Smith) Ralfs in Grammatophora marina (Lyngbye) Kützing, 1844 Pritchard, 1861 Grammatophora oceanica Grunow, 1881 Epithemia turgida (Ehrenberg) Kützing, 1844 Navicula crucicula (W. Smith) Donkin, 1872 Gomphonema olivaceum (Hornemann) Brébisson, 1838 Rhabdonema arcuatum (Lyngbye) Kützing, 1844 Gyrosigma parkerii (Harrison) Elmore, 1921 Rhabdonema minutum Kützing, 1844 Navicula capitata Ehrenberg, 1838 Navicula menisculus Schumann, 1867 Polyhalobous, planktonic Navicula pusilla W. Smith, 1853 Actinocyclus normanii (Gregory ex Greville) Hustedt, 1957 Navicula slesvicensis Grunow in Van Heurck, 1880 Coscinodiscus asteromphalus Ehrenberg, 1844 Nitzschia calida Grunow in Cleve & Grunow, 1880 Coscinodiscus nitidus W. Gregory, 1857 Pinnularia lundii Hustedt, 1954 Coscinodiscus radiatus Ehrenberg, 1841 Rhopalodia gibberula (Ehrenberg) O. Müller, 1899 Coscinodiscus spp Ehrenberg, 1839 Rhopalodia operculata (Agardh) Håkansson, 1979 Mesohalobous, benthic Rhoicosphenia abbreviata (C. Agardh 1831) Lange-Bertalot, Amphora commutata Grunow, 1880 1980 Fragilaria fasciculata (C. Agardh) Lange-Bertalot, 1980 Surirella angusta Kützing, 1844 Surirella capronii Brébisson in Kitton, 1869 Fragilaria pulchella Lange-Bertalot, 1980 Gyrosigma obscurum (W. Smith) Griffith & Henfrey, 1856 Halophilous, tychoplanktonic Hantzschia spectabilis (Ehrenberg) Hustedt, 1959 Cyclotella menghiniana Kützing, 1844 Mastogloia braunii Grunow, 1863 Mastogloia elliptica (Agardh) Cleve, 1893 Indifferent, benthic Mastogloia pumila (Cleve & Möller 1879) Cleve, 1895 Amphipleura pellucida (Kützing) Kützing, 1844 Mastogloia smithii Thwaites, 1856 Amphora libyca Ehrenberg, 1840 Melosira lineata (Dillwyn) Agardh, 1824 Amphora ovalis (Kützing) Kützing, 1844 Melosira moniliformis (O. F. Müller) Agardh, 1824 Caloneis bacillum (Grunow) Cleve, 1894 Melosira westii W. Smith, 1856 Caloneis silicula (Ehrenberg) Cleve, 1894 Navicula cruciculoides Brockmann, 1950 Cocconeis placentula Ehrenberg, 1838 Navicula elegans W.Smith, 1853 Cymatopleura elliptica (Brébisson) W. Smith, 1851 Navicula peregrina (Ehrenberg) Kützing, 1844 Cymatopleura elliptica v. hibernica (W. Smith) Van Navicula recens (Lange-Bertalot) Lange-Bertalot, 1985 Heurck, 1896 Nitzschia circumsuta (Bailey) Grunow, 1878 Cymbella aspera (Ehrenberg) Peragallo, 1849 Nitzschia commutata Grunow in Cleve & Grunow, 1880 Cymbella cistula (Ehrenberg) Kirchner, 1878 Nitzschia compressa (Bailey) Boyer, 1916 Cymbella lanceolata (Ehrenberg) Kirchner, 1878 Nitzschia constricta (Kützing) Ralfs in Pritchard 1861 non Diploneis ovalis (Hilse) Cleve, 1891 (Gregory) Grunow in Cleve and Grunow 1880 Ellerbeckia arenaria (Moore) Crawford 1988 Nitzschia hungarica Grunow, 1862 Epithemia adnata (Kützing) Brébisson , 1838 Nitzschia levidensis (W. Smith) Grunow in Van Heurck, Epithemia granulata (Ehrenberg) Kützing, 1844 1881 Epithemia sorex Kützing, 1844 Nitzschia littoralis Grunow in Cleve & Grunow, 1880 Fragilaria brevistriata Grunow in Van Heurck, 1885 Nitzschia marginulata Grunow in Clever & Möller, 1878 Fragilaria construens (Ehrenberg) Grunow, 1862 Nitzschia scalaris (Ehrenberg) W. Smith, 1853 Fragilaria exigua Grunow in Cleve & Möller, 1878 Nitzschia sigma (Kützing) W. Smith, 1853 Fragilaria lapponica Grunow in van Heurck 1881 Nitzschia tryblionella Hantzsch in Rabenhorst, 1860 Fragilaria pinnata Ehrenberg, 1843 Surirella striatula Turpin, 1828 Frustulia vulgaris (Thwaites) De Toni, 1891 Gomphonema gracile Ehrenberg, 1838 Mesohalobous, planktonic Gyrosigma attenuatum (Kützing) Rabenhorst 1853 Campylodiscus echeneis Ehrenberg, 1840 Navicula cuspidata (Kützing) Kützing, 1844 Campylodiscus hibernicus Ehrenberg, 1845 Navicula rhynchocephala Kützing, 1844 Chaetoceros spp resting spores Ehrenberg, 1844 Navicula sub-placentula Hustedt in A. Schmidt et al. 1930 Hyalodiscus scoticus (Kützing) Grunow, 1879 and Husted 1943 Thalassiosira baltica (Grunow in P.T. Cleve & Grunow) Navicula trivialis Lange-Bertalot, 1980 Ostenfeld, 1901 Navicula tuscula Ehrenberg, 1841 Thalassiosira hyperborea v. lacunosa (Berg) Hasle, 1989 Nitzschia amphibia Grunow, 1862 Thalassiosira hyperborea v. pelagica (Cleve-Euler) Hasle, Nitzschia heufleriana Grunow, 1862 1989 94

Paleoenvironment and shore displacement in the central part of the Långhundraleden Trail

Nitzschia palea (Kützing) W. Smith, 1856 Navicula placentula (Ehrenberg) Kützing, 1844 Rhopalodia gibba (Ehrenberg) O. Müller, 1895 Navicula pupula Kützing, 1844 Stauroneis smithii Grunow, 1860 Navicula viridula (Kützing) Ehrenberg, 1838 Neidium ampliatum (Ehrenberg) Krammer, 1985 Indifferent, planktonic Neidium affine (Ehrenberg) Pfitzer, 1871 Cyclostephanos dubius (Fricke) Round, 1987 Neidium dubium (Ehenberg) Cleve, 1894 Cyclotella radiosa (Grunow) Lemmermann, 1900 Neidium iridis (Ehrenberg) Cleve, 1894 Stephanodiscus medius Håkansson, 1986 Neidium productum (W. Smith) Cleve, 1894 Stephanodiscus hantzschii Grunow (in Cleve & Grunow), Nitzschia angustata (W.Smith) Grunow in Cleve & 1880 Grunow, 1880 Halophobous, benthic Pinnularia acrosphaeria Rabenhorst, 1853 Pinnularia braunii (Grunow) Cleve, 1895 Aulacoseira crenulata (Ehrenberg) Thwaites, 1848 Pinnularia brevicostata Cleve, 1891 Cymbella affinis Kützing, 1844 Pinnularia divergens W.Smith, 1853 Cymbella caespitosa (Kützing) Brun, 1880 Pinnularia gibba Ehrenberg, 1841(1843) Cymbella cuspidata Kützing, 1844 Pinnularia interrupta W. Smith, 1853 Cymbella cymbiformis Agardh, 1830 Pinnularia legumen (Ehrenberg) Ehrenberg, 1843 Cymbella ehrenbergii Kützing, 1844 Pinnularia macilenta (Ehrenberg) Ehrenberg, 1843 Cymbella helvetica Kützing, 1844 Pinnularia maior (Kützing) Rabenhorst, 1853 Cymbella hybrida Grunow in Cleve & Möller, 1878 Pinnularia nodosa (Ehrenberg) W. Smith, 1856 Cymbella hustedii Krasske, 1923 Pinnularia rupestris Hantzsch in Rabenhorst, 1861 Cymbella mesiana Cholnoky, 1955 Pinnularia streptoraphae Cleve, 1891 Cymbella minuta Hilse ex Rabenhorst, 1862 Pinnularia viridis (Nitzsch) Ehrenberg, 1843 Cymbella naviculiformis (Auerswald) Cleve, 1894 Pinnularia spp Ehrenberg, 1843 Cymbella proxima Reimer in Patrick & Reimer, 1975 Stauroneis anceps Ehrenberg, 1843 Cymbella silesiaca Bleisch in Rabenhorst, 1864 Stauroneis lauenburgiana Hustedt, 1950 Cymbella subaequalis Grunow in Van Heurk, 1880 Stauroneis phoenicenteron (Nitzsch) Ehrenberg, 1843 Cymbella subcuspidata Krammer, 1982 Surirella bifrons Ehrenberg, 1843 Cymbella tumida (Brébisson) Van Heurck, 1880 Surirella lapponica A. Cleve, 1895 Diploneis subovalis Cleve, 1894 Surirella minuta Brebisson in Kützing, 1849 Diploneis spp Ehrenberg, 1844 Surirella roba Leclercq, 1983 Eunotia spp Ehrenberg, 1837 Surirella robusta Ehrenberg, 1841 Fragilaria bidens Heiberg, 1863 Surirella visurgis Hustedt, 1957 Fragilaria capucina Desmazières, 1925 Fragilaria constricta Ehrenberg, 1843 Halophobous, planktonic Fragilaria dilatata (Brébisson) Lange-Bertalot, 1986 Aulacoseira ambigua (Grunow) Simonsen, 1979 Fragilaria nitzschioides Grunow in Van Heurck, 1881 Aulacoseira granulata (Ehrenberg) Simonsen, 1979 Fragilaria ulna (Nitzsch) Lange-Bertalot, 1980 Aulacoseira italica (Ehrenberg) Simonsen, 1979 Gomphonema acuminatum Ehrenberg, 1832 Aulacoseira spp Thwaites, 1848 Gomphonema angustum Agardh, 1831 Tabellaria fenestrata (Lyngbye) Kützing, 1844 Gomphonema angustatum (Kützing) Rabenhorst, 1864 Gomphonema augur Ehrenberg, 1840 Halophobous, tychoplanktonic Gomphonema clavatum Ehrenberg, 1832 Tabellaria flocculosa (Roth) Kützing, 1844 Gomphonema insigne Gregory, 1856 Gomphonema parvulum (Kützing) Kützing, 1849 Aerophilous, benthic Gomphonema subtile Ehrenberg, 1843 Pinnularia borealis Ehrenberg, 1843 Gomphonema truncatum Ehrenberg, 1832 Hantzschia amphioxys (Ehrenberg) Grunow in Cleve & Gyrosigma acuminatum (Kützing) Rabenhorst, 1853 Grunow, 1880

Mastogloia smithii v. lacustris Grunow, 1878 Rheophilous, benthic Navicula abiskoensis Hustedt, 1942 Meridion circulare (Greville) C. A. Agardh, 1831 Navicula americana Ehrenberg, 1843 Navicula bacillum Ehrenberg, 1843 Unknown ecology Navicula cari Ehrenberg, 1836 Cymbella spp Agardh, 1830 Navicula clementioides Hustedt, 1944 Fragilaria spp Lyngbye, 1819 Navicula elginensis (Gregory) Ralfs in Pritchard, 1861 Gomphonema spp Ehrenberg, 1832 Navicula gastrum (Ehrenberg) Kützing, 1844 Navicula spp Bory de St. Vincent, 1822 Navicula hasta Pantocsek, 1982 Nitzschia spp Hassall, 1845 Navicula libonensis Schoeman, 1970 Surirella spp Turpin, 1828 Navicula oblonga (Kützing) Kützing, 1844 Navicula radiosa Kützing, 1844