Karl-Dag Vorren

High-resolution stratigraphy of the northernmost concentric raised bog in Europe: Sellevollmyra, Andoya, northern Norway

From the Sellevollmyra bog at Andoya, northern Norway, a 440-cm long peat core covering the last c. 7000 calendar years was examined for humification, loss-on-ignition, microfossils, macrofossils and tephra. The age model was based on a Bayesian wiggle-match of 35 C-14 dates and two historically anchored tephra layers. Based on changes in lithology and biostratigraphical climate proxies, several climatic changes were identified ( periods of the most fundamental changes in italics): 6410-6380, 6230-6050, 5730-5640, 5470-5430, 5340-5310, 5270-5100, 4790-4710, 4890-4820, 4380-4320, 4220-4120, 4000-3810, 3610-3580, 3370-3340 ( regionally 2850-2750; in Sellevollmyra a hiatus between 2960-2520), 2330-2220, 1950, 1530-1450, 1150-840, 730? and c. 600? cal. yr BP. Most of these climate changes are known from other investigations of different palaeoclimate proxies in northern and middle Europe. Some volcanic eruptions seemingly coincide with vegetation changes recorded in the peat, e.g. about 5760 cal. yr BP; however, the known climatic deterioration at the time of the Hekla-4 tephra layer started some decades before the eruption event.

Pollen deposition rates in peat and lake sediments from the Pinus sylvestris L. forest-line ecotone of northern Norway

A comparative investigation of pollen deposition in peat and limnic sediments from the Pinus sylvestris-Alnus incana forest line in Dividalen, central Troms, northern Norway was performed by pollen analyses of sub-modern sediments. The possibilities of using 210Pb and 137Cs-datings in calculations of pollen influx in peat and limnic sediments are discussed. Correlation between the lead–cesium peat chronology and a marker-based limnic chronology is achieved at AD 1945–1946 by comparing the percentual pollen-curves. The upper 14 cm of the peat and 12 cm of the limnic sequence are hence supposed to represent the period ca. 1945–ca. 1996. The mean percentual representation of Pinus pollen is nearly twice as high in the peat sediments as in the limnic sediments, probably due to a slight over-representation from pine trees at the edge of the mire. The mean percentual pollen values for Alnus and Betula pubescens-type is fairly equal in peat and lake sediments, while the pollen influx rates are higher for all tree taxa in the lake sediments. This may be caused by the lake being exposed to a larger regional component than the smaller and topographically more sheltered mire. To achieve reliable pollen influx data at a near annual resolution, one needs a good control of the sedimentation processes, close intervals of isotope measurements and additional chronostratigraphically fixed marker horizons.

Human impact on the Holocene forest line in the Central Alps

Palaeoecological investigations of a small mire in Ötztal, Tyrol, Austria, situated about 50 m above the potential tree-line, indicates that human impact on the landscape started with burning of heath at approximately 5300 B.P. At about 4800 B.P. a weak increase in important apophytes may reflect the local presence of domestic animals. Between 4000 and 3500 B.P. a clear decline in pastoral activity occurred. From 3000 B.P. a strong increase in the representation of apophytes suggests local summer settlement, while in the interval 2600–2200 B.P. anthropogenic activity declined. After 2150 B.P. there was a marked increase in summer farm activity. Fresh information is presented on tree-line fluctuations during the Holocene: Pinus cembra forest ascended above the present potential tree-line by more than 50–100 m between 9000–8000 B.P., 6000–5500 B.P., and 3800–3000 B.P. A Betula maximum between 7000 and 5500 B.P. is probably due to succession in nearby avalanche tracks, as well as to a higher tree-line. Low humification and low loss-on-ignition values around 6000 B.P. may reflect the Frosnitz stadial (6900–6000 B.P.). The Rootmoos I stadial (5400 B.P.) and probably the early Sub-Atlantic stadial maximum (3000–2300) are also reflected in the physical properties of the peat profile.

Age and agricultural history of the ‘-staðir’ farms of North and Central Norway

As part of an interdisciplinary project, 19 sites of 16 farms of the -staðir and staðr (one case) farm name class were investigated by means of palynological analysis and radiological datings of peat deposits close to the farm centre. In a rough summing-up it can be stated that only four to five cases showed a continuously high farming activity from approximately A.D. 200–300 to the Medieval period. Two to three cases were most likely founded or radically expanded during the Viking Age. Nine cases exhibited a more or less profound depression during the Merovingian Era, most of them representing a desertion period. Five to six of the latter cases arc concentrated around A.D. 660. We suggest that the staðir farms investigated were named during one or both of the following periods: A.D. 160–390 and A.D. 780–920.

Holocene tree‐line fluctuations and climate in central troms, Northern Norway

Based mainly on pollen influx data, an attempt is made at reconstructing Holocene tree‐line fluctuations and palaeotemperatures in central Troms, North Norway. Both past and present‐day (Tauber trap) pollen influx data suggest that influx rates exceeding 250–300 pollen/cm2/year for each of the major arboreal taxa (Betula pubescens and Pinus sylvestris) are only found at sites with corresponding forest types in the immediate surroundings. High influx rates, raised tree‐lines and favourable climatic periods are recorded at 7500–4500 and 3000–2600 B.P. Betula and Pinus woodlands may have reached more than 200 m above their present altitude limits, suggesting a July mean temperature 2°C higher than at present during the Holocene optimum.

An examination of a palsa with layers of diatomite at Kautokeino, North Norway

Gottlich, K., Hornburg, P., Konig, D., Schwaar, J. & Vorren, K.-D. 1983. Untersuchungen an einem Palsen mit Kieselgurschichten bei Kautokeino, Nord-Norwegen. An examination of a palsa with layers of diatomite at Kautokeino, North Norway. Norsk geogr. Tidsskr. Vol. 37, 1–31. Oslo. ISSN 0029-1951.

The first permafrost cycle in Færdesmyra, eastern Finnmark, Norway?

ABSTRACT The author studied the causal relationships between palsa formation, the maintenance of palsas, their final thawing, and climate. His main approach was to compare his observations with other researchers’ observations of recent palsa formation and degradation, and the use of relevant palaeoclimatic data. A more than 10 km2 large palsa mire complex in Sør-Varanger Municipality, northern Norway, was studied in terms of vegetation and stratigraphy 50 years ago, and then observed between 2005 and 2015, when the final palsa thawing occurred. The decisive climatic factor for the maintenance of existing palsas – annual mean temperatures below -1 °C, stated earlier by researchers – seemed to be valid also in the studied case. However, the results showed that new palsa formation may require a series of consecutive years with temperatures between -1 and -2 °C in annual mean temperatures. There is a possibility of detecting former palsas (i.e. since thawed) by stratigraphic investigations in cases of lateral erosion of palsas. Stratigraphic corings and field observations in the selected study area did not indicate earlier periods of palsa thawing prior to the modern one. The author concludes that the present thawing thus reflects a reversal of the final cooling stage of the present interstadial (Holocene).