Remanent magnetization of the Jotnian sandstone in Satakunta, SW-Finland

Abstract

Direction and intensity of remanent magnetization were measured on samples from a flat-laying Precambrian sandstone before and after heating at 400°C. The direction revealed and the calculated pole position agree with those observed for dike rocks in SW-Finland. The origin of the magnetization is discussed.

Meddelelser Fra Dansk Geologisk Forening · Bind 26 · Hæfte 3-4

“…The a.p.w. path between 1900 and 1300 Myr of Neuvonen (1970Neuvonen ( , 1973 appears to be rather well established (Larsson 1976), except for the polar-ity, which is still undetermined, because of a gap in reliable data between 1250 and 900 Myr. Between 900 and 700 Myr a northeastly directed a.p.w.…”

Mesoproterozoic Strike-Slip Faulting within the Åland Rapakivi Batholith, Southwestern Finland

“…This period started with the emplacement of the anorogenic rapakivi batholiths at 1.65-1.54 Ga (Rämö and Haapala, 1995), including the 1.58-1.57 Ga Åland rapakivi batholith (Figure 1; Suominen, 1991), which forms the bulk of the bedrock within the present study area, and the roughly coeval swarm of NE-SW-trending diabase dykes occurring southeast of the Åland rapakivi batholith (Ehlers and Ehlers, 1977;Suominen, 1991). Rapakivi magmatism is post-dated by regionally extensive Mesoproterozoic sedimentary rocks (Figure 1), which were deposited under stable intracontinental conditions (Kohonen et al, 1993;Pokki et al, 2013). The maximum age of the sedimentary deposition and the associated subsidence and faulting is uncertain due to the lack of clastic material from rapakivis or observed cross-cutting relationships (Kohonen et al, 1993).…”

“…Rapakivi magmatism is post-dated by regionally extensive Mesoproterozoic sedimentary rocks (Figure 1), which were deposited under stable intracontinental conditions (Kohonen et al, 1993;Pokki et al, 2013). The maximum age of the sedimentary deposition and the associated subsidence and faulting is uncertain due to the lack of clastic material from rapakivis or observed cross-cutting relationships (Kohonen et al, 1993). However, a 1.54-1.41 Ga age is suggested by the Ar/Ar ages from the 1.65 Ga (Vaasjoki, 1977) Obbnäs rapakivi granite, which Heeremans et al (1996) attributed to resetting of the isotopic system during Mesoproterozoic graben formation or, alternatively, to the cooling of the rapakivi intrusion.…”

“…With respect to (Högdahl et al, 2004), LSGM = Late Svecofennian Granite-Migmatite zone (Ehlers et al, 1993), SJSZ = Sottunga-Jurmo Shear Zone (Torvela and Ehlers, 2010), SS = Satakunta Sandstone (Kohonen et al, 1993).…”

“…The outline of Figure 3 is indicated on the map. TIB = Transscandinavian Igneous Belt(Högdahl et al, 2004), LSGM = Late Svecofennian Granite-Migmatite zone(Ehlers et al, 1993), SJSZ = Sottunga-Jurmo Shear Zone(Torvela and Ehlers, 2010), SS = Satakunta Sandstone(Kohonen et al, 1993). The figure is based on the Geological map of the Fennoscandian shield 1:1,000,000(Geological Survey of Finland, 2001).…”