WHY MONITOR CARBON IN HIGH‐ALPINE STREAMS?

In this short communication, we report on dissolved organic and inorganic carbon concentrations from a summer stream monitoring campaign at the main hydrological catchment of the Tarfala Research Station in northern Sweden. Further, we place these unique high‐alpine observations in the context of a relevant subset of Sweden's national monitoring programme. Our analysis shows that while the monitoring programme (at least for total organic carbon) may have relatively good representativeness across a range of forest coverages, alpine/tundra environments are potentially underrepresented. As for dissolved inorganic carbon, there is currently no national monitoring in Sweden. Since the selection of stream water monitoring locations and monitored constituents at the national scale can be motivated by any number of goals (or limitations), monitoring at the Tarfala Research Station along with other research catchment sites across Fennoscandia becomes increasingly important and can offer potential complementary data necessary for improving process understanding. Research catchment sites (typically not included in national monitoring programmes) can help cover small‐scale landscape features and thus complement national monitoring thereby improving the ability to capture hot spots and hot moments of biogeochemical export. This provides a valuable baseline of current conditions in high‐alpine environments against which to gauge future changes in response to potential climatic and land cover shifts.     

Holocene shore displacement and deglaciation chronology in Norrbotten, Sweden

The coastal zone of Norrbotten, northern Sweden, was gradually inundated by the Ancylus Lake following the retreating ice margin and forming a highest coastline approximately 210 m above the present sea level. The succeeding shore displacement is reconstructed based on lithological investigations and radiocarbon datings of identified isolation sequences from 12 cored lake basins. The highest lake basins, along with two basins above the highest shoreline, suggest ice-free conditions already at 10 500 cal. yr BP. This is at least 500 years earlier than previously thought and implies rapid ice-sheet break-up in the Gulf of Bothnia. The shore displacement (RSL) curve represents a forced regression of successively decreasing rate through the Holocene, from 9 m/100 yr to 0.8 m/100 yr. During the first 1000-1200 years, the isostatic uplift is exponentially declining, followed by a constant uplift rate from c. 9500 cal. yr BP to 5500-5000 cal. yr BP. The last 5000 years seem to be characterized by a low but constant rebound rate. The development of the Ancylus Lake stage of the Baltic may also be discerned in the Norrbotten RSL curve, suggesting that the chronology of the Ancylus Lake stages may have to be revised. The Littorina transgression is also reflected by the RSL curve shape. In addition, a series of early to mid-Holocene beach terraces were OSL-dated to allow for comparison with the ¹⁴C-dated shore displacement curve. Interpretations of these ages and their relation to former sea levels were clearly more problematic than the dating of the lake basin isolations.     

Comments on‘Heimdall's Stones at Vitemölla in SE Sweden and the Chronology and Stratigraphy of the Surroundings’byMörneret al. (2009)

Mörner, N.‐A. and Lind, B., 2011. Reply: Comments on ‘Heimdall's stones at Vitemölla in SE Sweden and the chronology and stratigraphy of the surroundings’ by Mörner et al. (2009). Geografiska Annaler: Series A, Physical Geography, 93, 197–199. DOI: 10.1111/j.1468‐0459.2011.00429.x     

HEIMDALL'S STONES AT VITEMÖLLA IN SE SWEDEN AND THE CHRONOLOGY AND STRATIGRAPHY OF THE SURROUNDINGS

Heimdall's Stones at Vitemölla is an archaeological monument of stones arranged in circles and where sightlines can be identified of the sunrise and sunset at winter and summer solstices and spring and autumn equinoxes. Therefore, this stone monument is likely to have served as an archaeoastronomic observatory. It is founded in a fossil land surface now covered by half a metre of eolian sand. In order to date this sand drift, sediment coring was performed in the nearby Sandefloen bog. Seven levels were subjected to AMS C14 dating. The first sand drift, correlated with the sand drift covering Heimdall's Stones, was dated at 500–600 cal. bc . Consequently, the observatory has to date back to the Bronze Age, fitting well with its Sun cult and with the rock carvings recorded on the individual stones. At the seashore 500 m east of the observatory and the bog, we were able to reconstruct the sea-level changes. In conclusion, we combine the recorded sea-level changes with the C14-dated bog stratigraphy and the observed stratigraphy at Heimdall's Stones (covering an area of 500×500 m) into one unified picture. The chronostratigraphic position of Heimdall's Stones agrees well with the dating of the Kivik grave. The Vitemölla area is likely to have been an important cultural centre in the Bronze Age.     

Dislocated Quaternary deposits in southeastern Kattegat – a glacial or gravitational phenomenon?

The Quaternary deposits in the Store Middelgrund–Rørdebanke area midway between the island of Anholt and Hallandsåsen on the Swedish coast are described on the basis of reflection seismic profiles with a vertical resolution of 5–10 m. The Quaternary rests on Upper Cretaceous limestone, the surface of which is nearly horizontal. Three Quaternary sequences are defined and interpreted as: (1) Late Weichselian marine or lacustrine deposits, (2) Late Weichselian glaciogenic deposits, and (3) Late Saalian–Eemian and Early–Middle Weichselian deposits. Sequence 3 is probably comparable to the upwards-coarsening sequence known from Skaerumhede in Vendsyssel. The layers in sequence 3 are dislocated in the eastern part of the Store Middelgrund–Rødebanke area mainly by gentle folding, but other types of deformations occur. Folding could be the result of horizontal push from an ice sheet approaching from the east. Alternatively the folding is an effect of vertical, gravitational forces acting on the sediments due to an unstable density profile, as described by the Rayleigh–Taylor instability model. The zone of deformation is located close to the northern flank of the tectonically active Sorgenfrei–Tornquist Zone. It is suggested that the initiation of the folding process was facilitated by tremors from small earthquakes.     

Ribbed moraine formed by subglacial folding, thrust stacking and lee-side cavity infill

Transverse-to-iceflow ribbed moraine occurs in abundance in the coastal zone of northern Sweden, particularly in areas below the highest shoreline (200–230 m a.s.l.), but occasionally also slightly above. Based on detailed sedimentological and structural investigations of machine-dug sections across five ribbed moraine ridges, it is concluded that these vertically and distally prograding moraine ridges were formed as a result of subglacial folding/thrust stacking and lee-side cavity deposition. The proximal part of the moraines (Proximal Element) was formed by subglacial folding and thrust stacking of sequences of pre-existing sediments, whereas the distal part (Distal Element) was formed by glaciofluvial and gravity-flow deposition in lee-side cavities. The initial thrusting and folding is suggested to be a result of differences in bed rheology at the ice-marginal zone during the early or late melt season, and that generated a compressive zone transverse to ice flow as a result of a more mobile bed up-glacier compared to a less mobile bed down-glacier. It is considered that the lee-side cavities were formed as a result of ice-bed separation on the distal slope of the thrust/fold-created obstruction. The lee-side cavities formed an integral part of a subglacial linked-cavity drainage network regulated in their degree of interconnection, size and shape by fluctuations in basal meltwater pressure/discharge and basal iceflow velocity. The proximal and distal elements of the ribbed moraine ridges are erosively cut and/or draped with a consistently more homogeneous deforming bed till (Draping Element) marking the final phase of ribbed moraine formation considered to be contemporaneous with De Geer moraine formation further down-flow at the receding ice-sheet margin.     

Seismic stratigraphy of the Quaternary and its substratum in southeastern Kattegat, Scandinavia

Based on c. 1500 km reflection seismic profiles, the Quaternary formations and their pre-Quaternary substratum in the southeastern Kattegat are described and a geological interpretation is suggested. The major volume of Quaternary deposits is found in a broad north-northwest south-southeast trending topographic depression. The substratum consists of Upper Cretaceous limestone in the region north of the Sorgenfrei–Tornquist Zone, and inside this zone older Mesozoic sedimentary rocks and Precambrian crystalline rocks are found. The Quaternary is divided into four seismic units. No direct stratigraphic control is available, but the units are assumed to represent a period ranging from Late Saalian to Holocene. The oldest unit (unit 3) is composed of deposits of supposed Late Saalian to Middle Weichselian age. This unit was severely eroded probably by the Late Weichselian ice sheets in a zone extending 40–50 km from the Swedish coast. Unit 2 represents the Late Weichselian till deposits. North and east of the island of Anholt unit 3 is cut by a system of channels eroded by glacial meltwater. By the erosion a relief up to c. 100 m was formed. After the recession of the Late Weichselian ice, an up to 100 m thick sequence of water-lain sediments (unit 1) was deposited in the erosional basin and channels. Holocene deposits (unit 0) of considerable thickness have only been identified in the channels in the northern part of the area.