Wyniki wyszukiwania - BazTech

Ograniczanie wyników

2 Geological Quarterly

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Sortuj według:

Ogranicz wyniki do:

Palaeomagnetism of Late Cretaceous-Paleocene igneous rocks from the western part of the Antarctic Peninsula (Argentine Islands Archipelago)

Bakhmutov V., Shpyra V.

Geological Quarterly

2011

Vol. 55, No. 4

285-300

A collection of 360 oriented samples of igneous rocks from the western part of the Antarctic Peninsula (Argentine Islands Archipelago, Penola Strait area), has yielded well-defined palaeomagnetic directions. Age determinations by various methods showed a Late Cretaceous-Paleocene time interval for the rocks studied. The characteristic remanent magnetisation (ChRM) was isolated by a stepwise thermal demagnetisation mostly in the temperature interval 450-580 degreesC. It is evidently a primary magnetisation. The rocks along the coastline of the western part of the Antarctic Peninsula (AP) were emplaced during the Cretaceous Normal Superchron while the rocks from the islands with reversed polarity are of Paleocene. New Cretaceous (112-85 Ma) and Paleocene (60 Ma) palaeomagnetic poles for the passive continental margin of the Antarctic Peninsula fit well with a synthetic East Antarctica apparent polar wander path and confirms that the AP did not undergo latitudinal displacement for the last 100 Ma. The palaeomagnetic pole for 60 Ma shows a slight shift from palaeopoles obtained for the South Shetland Islands which implies that the South Shetland block is characterized by own tectonic evolution and probable anticlockwise rotation during the Paleocene.

Lithology and palaeomagnetic record of Late Weichselian varved clays from NW Russia

Bakhmutov V., Kolka V., Yevzerov V.

Geological Quarterly

2006

Vol. 50, No. 3

353-368

A lithological and palaeomagnetic analysis of Late Weichselian glaciolacustrine deposits from two ancient periglacial lakes was carried out in the valley of the Shuja (S Karelia) and Ust-Pjalka (S-E Kola Peninsula) rivers, NW Russia. The rhythmic structure of the varved clays is interpreted as turbiditic with systematic differences between the proximal and distal areas of accumulation. In the proximal area the textural and structural properties of the deposits towards both distal and (partly) lateral directions are described. It is shown that the proximal varve successions are incomplete while distally they are continuous. The accumulation of one varve (DE rhythm, second order cycle) during one year is consistent with palaeomagnetic data. Significant differences in magnetic parameters and in the palaeomagnetic "records" of declination-inclination between proximal and distal varves are established. Analysis of palaeomagnetic properties was combined with lithological analysis in all sections. Locally, the varved clays in the proximal area could be used for palaeomagnetic research. Taking into account the erosion of underlying deposits by turbidity currents and inclination shallowing, these sediments could not precisely record palaeosecular variation (PSV). The distal varved clays (represented by the DE rhythms) are clearly most useful both for varve-clay chronology and PSV recovery. The palaeomagnetic declination and inclination records are correlated with chrono- and magnetostratigraphy scheme of NW Russia. This paper also examines lithology-dependent "inclination error" and anisotropy of magnetic susceptibility in glaciolacustrine sediments.