Palaeomagnetic Data from Ediacaran (Vendian) Sediments of the Arkhangelsk region, NW Russia: An Alternative Apparent Polar Wander Path of Baltica for the Late Proterozoic-Early Palaeozoic

IGLESIA LLANOS, MARíA PAULA; J.A. TAIT; V. POPOV; A. ABALMASSOVA

EARTH AND PLANETARY SCIENCE LETTERS

Elsevier

Lugar: Amsterdam; Año: 2005 vol. 240 p. 732 - 747

0012-821X

The study area is located along the Zolotica river in NW Russia, located within the Kola-Dvyna Rift System in the Baltic Shield. that developed during the Sturtian (= Riphean) and Vendian times. A nine meters- thick section made up of shallow marine sediments of Upper Vendian age was sampled in this locality. Two volcaniclastic levels from the middle part of the section yielded an age of ~ 556 Ma. (U/Pb SHRIMP-II on zircons). Two magnetic components were successfully isolated, component A (Decl= 157.1, Incl= 68.0, á95= 1.9, N= 575 in situ and Decl= 171.4, Incl= 66.9 bedding corrected) carried by magnetite and component B (Decl= 120.3,  Incl= -31.7, á95= 3.9, N= 57, bedding corrected), carried by haematite.The direction from component A in situ fully coincides with that expected for the Early Ordovician at the locality, so that this component is interpreted to correspond to an overprint of this age. The direction from component B on the other hand, is dissimilar to any expected younger direction and is interpreted to represent the primary magnetisation acquired during or soon after deposition of the sediments in the Late Vendian. The corresponding palaeomagnetic poles are located for component A in situ at Lon= 55.4°E, Lat= 31°N, A95= 2.7° and for component B at Lon= 110°E, Lat= 28.3°S, A95= 3.8°, N= 57. Combined with other palaeomagnetic poles of the same tectonostratigraphic unit an alternative apparent polar wander path for the Late Proterozoic-Early Palaeozoic of Baltica is proposed. Such an alternative path shows that after the Sturtian (750 Ma.), the poles that were situated over South Africa (p.d.c.) moved to the east until they reached Australia during the Late Vendian  (555 Ma.) where they remained approximately stationary until the beginning of the Cambrian (~545 Ma.). Finally, they moved to the northwest until they reached the Arabian Peninsula in the Early Ordovician. Palaeolatitudes indicate that the Zolotica region situated near the equator from Late Sturtian through to the Early Vendian moving gradually to the north at 10-20 mm/yr. Subsequently, it moved to the south at c.275 mm/yr at the Vendian-Cambrian boundary and then to the north again at lower rates (200-50 mm/yr) until the Ordovician.