Badania paleomagnetyczne osadów kambru z otworów Goczałkowice IG 1 i Sosnowiec IG 1 (Górny Śląsk)

Jerzy Nawrocki

Abstract


W efekcie analizy paleomagnetycznej stwierdzono, że co najmniej w środkowym kambrze Górny Śląsk znajdował się w obrębie wysokich (około 60°) paleoszerokości geograficznych. Wysokie inklinacje otrzymane z prób środkowokambryjskich nie odbiegają od paleonklinacji wyznaczonych dla skał kambru i dolnego ordowiku Masywu Armorykańskiego oraz południowej części Gór Świętokrzyskich. Wtórne składowe namagnesowania utrwalone w hematytowym spoiwie piaskowców i mułowców przemawiają za późniejszą (najprawdopodobniej karbońską) rotacją badanego obszaru.

 

PALAEOMAGNETC INVESTIGATIONS OF THE CAMBRIAN DEPOSITS FROM THE GOCZAŁKOWICE IG 1 AND SOSNOWIEC IG 1 BOREHOLES (UPPER SILESIA)

Paleomagnetic investigations have been carried out on the Lower and Middle Cambrian clastic deposits from the Goczałkowice IG 1 and Sosnowiec IG 1 boreholes. Analysis of results of thermal demagnetization of the Goczałkowice Lower Cambrian sandstone let distinguish three groups of components of natural remanent magnetization (NRM):

-low-stable components, determined from results of detailed analysis (including laboratory test) as the youngest (probably Cainozoic);

- interpreted as closed to primary, high stable components with inclination values similar to ones of the previous group and relative declination differs by 180° (directions lie in the oposite quadrant of the lower hemisphere of projection in relation to the directions determined for the previous group);

- medium and high stable components with under equatorial values of inclination and values of declination included in the 60° diversification interval.

Characteristic directions of the Middle Cambrian Sosnowiec IG 1 borehole sandstone samples are of high, negative or positive value of inclination. Various polarity is here an important contention for primariness of the NRM components related to these directions. Results obtained let set up hypothesis that the least in Middle Cambrian the area investigated must lie within the zone of high latitude (around 60°). Taking into consideration contemporary reconstruction of the Lower Palaeozoic configuration of continents (e.g. R van der Voo, 1988) this area should be placed in a zone on the border of moderate and subpolar latitudes in the southern hemisphere. A mode of spatial distribution of the NRM secondary components fixed by haematization of the Lower Cambrian Goczałkowice IG 1 borehole scolithous sandstones indicates a great probability of the Carboniferous rotation of area investigated. For such an age of rotation speak underequatorial values of palaeoinclination, and the Carboniferous rocks which here are the dominant component of the overburden. Elevated temperature resulting in interaction of the overburden caused chemical alternation of goethite, non magnetite cryptocrystalline haematite pigment, what resulted in forming magnetically active haematite, being a carrier of the NRM secondary components. Due to the limited range of investigations the results presented and their interpretations should be treated only as initial.


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