Structural development along the Billefjorden Fault Zone in the area between Kjellströmdalen and Adventdalen/Sassendalen, central Spitsbergen

The Billefjorden Fault Zone represents a major lineament on Spitsbergen with a history of tectonic activity going back into the Devonian and possibly earlier. Recent structural, sedimcntological and stratigraphical investigations indicate that most of the stratigraphic thickness variations within the Mesozoic strata along the Billefjorden Fault Zone south of Isfjordcn are due to Tertiary compressional tectonics related to the transpressive Eocene West-Spitsbergen Orogeny. No convincing evidence of distinct Mesozoic extensional events, as suggested by previous workers, has been recognized. Tertiary compressional tectonics are characterized by a combined thin-skinned/thick-skinned structural style. Decollement zones arc recognized in the Triassic Sassendalen Group (tower Décollement Zone) and in the Jurassic/Cretaceous Janusfjellet Subgroup (Upper Décollement Zone). East-vergent folding and reverse faulting associated with these decollement' zones have resulted in the development of compressional structures, of which the major arc the Skolten and Tronfjellct Anticlines and the Advcntelva Duplex. Movements on one or more high angle east-dipping reverse faults in the pre-Mesozoic basement have resulted in the development of the Juvdalskampcn Monocline, and are responsible for out-of-sequence thrusting and thinning of the Mesozoic sequence across the Billefjorden Fault Zone. Preliminary shortening calculations indicate an eastward displacement of minimum 3-4 km, possibly as much as 10 km for the Lower Cretaceous and younger rocks across the Billefjorden Fault Zone.     

Phosphorus and ChlorinE Content of Eight New U.S.G.S. Standard Rocks

Data on the content of phosphorus and chlorine in eight new U.S.G.S. standard rooks obtained by radiochemical neutron activation analysis are presented and discussed.     

Heat conservation during cold exposure in birds (vasomotor and respiratory implications)

The mechanisms by which peripheral circulation and respiration serve in maintaining thermal homeostasis in birds living in cold climates are reviewed. Three types of arteriovenous heat exchanger (an elaborate , a simple rete , and a venae comitantes system) are found in the legs of birds. The anatomical differences between the different types of A-V associations are described, and the regulation of peripheral blood flow, in respect to maximal heat conservation and prevention of tissue damage, is discussed. A nasal temporal counter current heat exchanger, lowering the temperature of the expired air to values considerably below the body temperature, is the most important mechanism for minimizing the respiratory heat and water loss. In addition, a decreased ventilatory requirement, caused by a changed respiratory pattern and an increased parabronchial oxygen extraction, lowers the amount of air ventilated relative to the amount of oxygen uptake. Thus, the relative loss of heat and water is reduced.     

Expanding spread profile at the northern Jan Mayen Ridge

An expanding spread seismic profile at the central northern Jan Mayen Ridge, ESP-5, has yielded a crustal seismic velocity distribution which is similar to observations from the thinned continental crust at the Norwegian continental margin. The profile reveals a post-early Eocene sedimentary sequence, about 1. 5 km thick, overlying 1 km of volcanic extrusives and interbedded sediments. Below, there are about 3 km of pre-opening sediments above the seismic basement. The results indicate that the main ridge block is underlain by a thinned crust, possibly only 13.5 km thick. The results are compatible with a continental nature for the main ridge complex.     

FAST HANKEL TRANSFORMS*

Inspired by the linear filter method introduced by D. P. Ghosh in 1970 we have developed a general theory for numerical evaluation of integrals of the Hankel type: Replacing the usual sine interpolating function by sinsh (x) =a· sin (ρx)/sinh (aρx), where the smoothness parameter a is chosen to be “small”, we obtain explicit series expansions for the sinsh-response or filter function H*. If the input function f(λ exp (iω)) is known to be analytic in the region o < λ < ∞, |ω|≤ω₀ of the complex plane, we can show that the absolute error on the output function is less than (K(ω₀)/r) · exp (?ρω₀/Δ), Δ being the logarthmic sampling distance. Due to the explicit expansions of H* the tails of the infinite summation ((m?n)Δ) can be handled analytically. Since the only restriction on the order is ν > ? 1, the Fourier transform is a special case of the theory, ν=± 1/2 giving the sine- and cosine transform, respectively. In theoretical model calculations the present method is considerably more efficient than the Fast Fourier Transform (FFT).     

AN INTERACTIVE COMPUTER/GRAPHIC-DISPLAY-TERMINAL SYSTEM FOR INTERPRETATION OF RESISTIVITY SOUNDINGS*

A fast computer-procedure giving the apparent resistivity curve as well as the partial derivatives with respect to the layer-parameters is presented. It is based on the linear filter method developed by D. P. Ghosh in 1971. The sampling frequency is 10 points per decade, and 3 decades are covered. The maximum relative error is less than 10^?3, and in most cases orders of magnitude smaller. The computation time on a CDC 6400 for one curve given in 30 points ranges linearly from .17s for a two-layer case to .36s for a ten-layer case. The procedure is used to plot master curves interactively on a graphic display terminal (Tektronix 4010) connected to the CDC 6400. By trial-and-error adjustments a set of layer-parameters is found, giving essentially the measured curve.     

The origin and age of driftwood on Jan Mayen

Analysis of the wood anatomy of 481 driftwood specimens from Jan Mayen shows that Larix spp. constitute approximately 70% of the trees, while sawn logs are dominated by Pinus spp. by approximately 69%. A total of 356 driftwood samples from Jan Mayen and a small number of samples from Bjørnøya in the Barents Sea and the Troynoy Island in the Kara Sea were analysed by dendrochronological methods. A driftwood Pinus chronology was dated absolutely using chronologies from living trees of Pinus sylvestris in the lower proximity of the Angara River, a tributary of the Yenisey in Siberia. About 27% of the pine logs measured on Jan Mayen were found to originate in the same region, with end years concentrated in the 1940s and 1950s. A similar source was also found for Pinus driftwood logs on Bjørnøya and Troynoy. The results confirm and further delimit the source areas of the Yenisey driftwood established earlier from driftwood logs on Svalbard and Iceland. A subordinate source of both Pinus and Picea logs on Jan Mayen is northwest Russia, from the Kola Peninsula to the Pechora River. The Transpolar Drift Stream is believed to be the main distributor of driftwood from Siberian and northwest Russian sources to Jan Mayen, via the East Greenland Current. Dendrochronological dating reveals a strong, continuous input of ice-rafted driftwood from the Kara Sea. Radiocarbon datings from Jan Mayen show surface deposits of driftwood to be less than 500 years old, due mainly to extensive degradation of older wood and little or no land uplift.     

A MAN/COMPUTER INTERPRETATION SYSTEM FOR RESISTIVITY SOUNDINGS OVER A HORIZONTALLY STRAFIFIED EARTH*

The proposed system works as follows:

• 1 By a trial-and-error procedure using a graphic display terminal a geologically relevant layer sequence with parameters (ρ_j, d_j) is adjusted to yield roughly the measured curve.
• 2 The resulting layer sequence is used as starting model for an iterative least squares procedure with singular value decomposition. Minimization of the sum of the squares of the logarithmic differences between measured and calculated values with respect to the logarithms of the resistivities and thicknesses as parameters linearizes the problem to a great extent, with two important implications:

• a) a considerable increase in speed (the number of iterations goes down), thus making it cheap to achieve the optimum solution;
• b) the confidence surfaces in parameter space are well approximated by the hyper-ellipsoids defined by the eigenvalues and eigenvectors of the normal equations.

Since these are known from the singular value decomposition we do in fact know all possible solutions compatible with the measured curve and the geological concept.

• 3 It is possible to “freeze” any combination of parameters at predetermined values. Thus extra knowledge and/or hypotheses are easily incorporated and can be tested by rerunning step (2). The overall computing time for a practical case is of the order of 10 sec on a CDC 6400.

     

Airborne pollen and spore registrations at Ny-Ålesund, Svalbard, summer 1986

Sampling of airborne pollen and spores at Ny-Alesund on Spitsbergen in the summer of 1986, by means of a Burkard pollen and spore trap, revealed only very low concentrations of air spora: a cumulative diurnal mean for the whole season of less than 200 pollen grains and just in excess of 9,000 moss and fungal spores. The most frequent pollen types recorded were those of the local taxa: Saxifraga, Salix and Oxyria digyna , whereas the share of pollen of exotic taxa, Betula, Pinus, Juniperus and Alnus , contributed only 9% of the total pollen sum. Back trajectories and pollen registrations at various aerobiological stations in Scandinavia designate central Finland as a possible source area both for the Betula and Pinus pollen. The maximum diurnal mean concentration of Cladosporium was merely 40 spores per m³ air. One may assert that the air at Ny-Alesund is almost free from allergenic pollen and spore types.