Vegetation, climate and ice-front oscillations in the Tromsø area, northern Norway during the Allerød and Younger Dryas

Sediments from two small lakes distal to the Tromsø–Lyngen moraine at Tromsø, northern Norway, indicate that the area was deglaciated prior to c. 11.7 ¹⁴C ka BP. The earliest vegetation was dominated by calciphilous and heliophilous pioneer plants on unstable soils; this changed to a vegetation reflecting a dry continental climate until c. 10.7 ¹⁴Cka BP. A phase (10.7–10.5 ¹⁴Cka BP) with snow-bed communities was followed by one with a mosaic of plant communities. This was succeeded by Empetrum heaths c. 10.3 ¹⁴Cka BP, then by an open forest with Betula pubescens after 10.0 ¹⁴Cka BP. Ice-front oscillations in the Tromsø area are evaluated. The main part of the Younger Dryas glacial readvance, the Tromsø–Lyngen event, probably occurred between 10.7 and 10.3 ¹⁴Cka BP.     

Mafic Magma Intraplating: Anatexis and Hybridization in Arc Crust, Bindal Batholith, Norway

The dioritic Velfjord plutons (     

Deglaciation and palaeoclimate of the Andfjord-Vågsfjord area, North Norway

This paper reviews the deglaciation history and palaeoclimate from 22 to 9.5 ¹⁴Cka BP in the Andfjord-Vagsfjord area. Eight main glacial events are recorded: The Egga-I (>22 ¹⁴Cka BP), the Bjerka, the Egga-II (>14.6 ¹⁴Cka BP), the Flesen (14.5 ¹⁴Cka BP), the D (13.8–13.2 ¹⁴Cka BP), the Skarpnes (12.2 ¹⁴Cka BP), the Tromsø–Lyngen (10.7–10.3 ¹⁴C ka BP) and the Stordal (10.0–9.5 ¹⁴Cka BP). Onset of the final deglaciation occurred about 14.6 ¹⁴Cka BP. Most of the western part of the Fennoscandian and Barents Sea Ice Sheets receded from the outer continental shelf 15–14 ¹⁴Cka BP. The delivery and melting of icebergs at this time to the Norwegian-Greenland Sea resulted in a low oxygen isotope event recorded in a number of cores in the region. Atlantic water intruded the area 13.2 ¹⁴Cka BP, and an atmospheric warming commenced 12.9/12.8 ¹⁴Cka BP. A marked glacial recession occurred before the Skarpnes event. During Allerød time, the glaciers retreated to the fjord heads or even farther inland. The Fennoscandian outlet glaciers readvanced (locally more than 40 km), reached their Younger Dryas outer limit after 10.7 ¹⁴Cka BP and retreated from this position before about 10.3 ¹⁴Cka BP.     

Grain-size distribution and grain-size parameters of different till types on Hardangervidda, south Norway

Vorren, T. O. 1977 06 01: Grain-size distribution and grain-size parameters of differcnt till type on Hardangervidda, south Norway.
Grain-size characteristics for different till types on Hardangervidda havc been studied: Basal tills are finer grained than ablation tills: phyllitic basal tills are relatively rich in gravel and clay: basal tills derived from a semiporphyritic granite are poor in clay and have a deficiency of very coarse sand. Of the Folk a Ward's (1957) grain-size distribution parameters, sorting and kurtosis seem to he the most diagnostic parameters for distinguishing between different types of till. A linear corrclation betwen sorting and the other grain-size parameters is indicated for the basal tills.     

The last deglaciation (20,000 to 11,000 B. P.) on Andoya, northern Norway

Cores representing a 5.5m long sequence recovered from lake Æråsvatnet have been investigated for lithostratigraphy, micro- and macrofossils and radiocarbon chronology. For the first time in Fennoscandia the maximum Weichselian advance has been closely bracketed with radiocarbon datings (19,000–18,500 B.P.). A continuous stratigraphy from 18,500 B.P. and onwards, partly marine and partly lacustrine, discloses the local shoreline displacement, the palaeovegetation, the palaeoclimate and, together with other data, the deglaciation history. Two phases with a prevailing High Arctic climate have occurred: 18,000 to 16,000 B.P. and 13,700 to 12,800 B.P. Important climatic amelioration accelerating the deglacial recession occurred 16,000, 12,800 and 12,000 B.P. The continental ice sheet was situated close to its maximum position until about 16,000 B.P. The following deglaciation was interrupted by (a minor ?) readvance/halt about 15,000 B.P. (the Flesen event), 13,700-13,000 B.P. (the D-event), 12,500 B.P. (the Skarpnes event) and 11,000–10,000 B.P. (the TromsØ-Lyngen event). The deglaciation chronology and pattern can be correlated with the suggested deep-sea-stratigraphy-based stepwise pattern relying on the old age alternative for termination IA.     

Foraminiferal stratigraphy, palaeoenvironments and sedimentation of the glacigenic sequence southwest of Bjørrnøya

Based on four shallow drillings in the outer part of the Bjørnøya trough, palaeoenvironments of foraminifera in glacigenic sediments are discussed. Different methods were used; detailed foraminiferal analysis, oxygen and carbon stable isotope analysis and transfer functions. Six different foraminiferal assemblage zones were found. One zone, AA, appears to be pre-Pleistocene in age and contains an abundance of reworked early Tertiary foraminifera. Four of the assemblage zones have a dominant arctic foraminiferal content; however, a marked boreal input is evident, particularly in zone B where B. marginata dominates. We suggest that B. marginata has been resedimented from pre-Eemian 'warm' deposits. Its occurrence in these older warm intervals possibly reflects a lower input of the Norwegian Current into the area and possibly an increase in the relative nutrient content of the water masses. The six zones have also differing numbers of foram./gram sediment. An assemblage zone where a boreal component of foraminifera ( E. nipponica, P. bulloides ) dominates was found, zone C. We define this particular assemblage zone to be of Eemian age (isotope substage 5e). The foraminiferal assemblage composition and the oxygen and carbon isotopes from zone C indicate that oceanographic conditions in the Barents Sea during the Eemian were slightly different from those of the present and that, possibly, Atlantic waters were more prevalent.     

Grain size distribution expressed as tanh-functions

The grain size distribution within a unimodal sediment can be described as a lognormal distribution when the distribution is formed by only one process. However, most sediments are formed by more than one process giving polymodal sediments. Polymodal sediments have to be described as the sum of several normal distributions, one for each process involved within the formation. Grain size distributions are usually interpreted with the help of graphical methods. Interpretations of polymodal sediments require mathematical methods. In mathematical terms a unimodal sediment can be described as a tangential hyperbolic function (tanh) and a polymodal sediment can generally be described by the sum of two or three tanh-functions. The tanh-method is a tool for identifying and estimating the number of modes within a grain size distribution and helps interpret the processes involved within the formation of a deposit. The mathematical method can also be used to computerize sediment data, allowing storage with just a few numbers. Different samples can easily be compared and classified. Also, this method could be a valuable tool for calculations of various sediment parameters both in geotechnology and hydrogeology.     

Stratigraphy and lithology of Late Pleistocene sediments at Møvatn, Hardangervidda, South Norway

Stratigraphic, textural, mineralogical, geochemical and palynological investigations indicate the existence of: lacustrine clay from late Eemian (Hovden thermomer); dark indicateclayey basal till of the Early Weichselian age (Hovden kryomer); lacustrine sediments from an Early or Middle Weichselian interstadial (Førnes thermomer); and basal till from Middle/ Late Weichselian (Førnes kryomer). The environment during the thermomers is discussed.