Juha Köykkä - Oulu

Res Terrae, Ser. A 32, J. Köykkä, Sedimentology of the Mesoproterozoic Telemark basin-fills, South Norway: implications for
sedimentation processes, depositional environments and tectonic evolution
the late Paleoprotorezoic and early Mesoproterozoic, Fennoscandia was part of the Co-
lumbia/Nuna supercontinent, and later part of the Laurentia (Fig. 1).
Gothian Orogeny can be described as a ca. 200–250 Ma period of subduction of
oceanic crust along the southwestern margin of the Fennoscandia during the 1.66–1.5
Ga (e.g., Brewer et al., 1998; Andersen, 2005; Åhäll and Connelly, 2008). The orogeny
evolution was charachaterized by near-continuous oceanward-stepping crustal growth,
relative to the active trench, and an average continental growth for major stages of
continental magmatism is estimated at ca. 1.6 km/Ma (Åhäll and Connelly, 2008). It is
assumed that southwestern part of the Fennoscandia may have formed during the Go-
thian Orogeny, when fragments of magmatics arcs with limited geochemical character
have been accreted onto Fennoscandia in distinct event in the period between ca. 1.66
to 1.5 Ga. (e.g., Brewer et al., 1998; Åhäll et al., 2000). This period of accretionary
orogeny was terminated by merging of a continental fragment, making up present-day
southern Norway. The subduction event was followed by a period of anorogenic crus-
tal extension magmatism and sedimentation starting at the 1.51–1.50 Ga (Bingen et al.,
2005).
The western margin of the EEC was affected by the Sveconorwegian Orogeny at
the end of the Mesoproterozoic (ca. 1.14–0.90 Ga), which suggest that Baltica collide
with another major plate. Bingen (2005) subdivided the Sveconorwegian Orogeny to
four major phases: (i) 1.14–1.05 Ga accretion and local early collision; (ii) 1.05–0.98
Ga continent-continent (Baltica-Amazonia collision); (iii) 0.98–0.96 Ga final conver-
gence; (iv) 0.96–0.90 Ga post-collisional relaxation. Models involving oblique conti-
nent-continent collision with significant strike-slip motion between a coherent Baltica-
Laurentia margin and possible Amazonia (e.g., Bingen, 2005, 2008a, 2008b). Prior to
the major collisional stage, the Sveconorwegian Orogeny shortly followed upon an
event of continental magmatism and basin formation in the Telemark, Kongsberg, and
Bamble blocks, suggesting extensional or transtensional tectonic regime at the onset of
the Sveconorwegian Orogeny.
Collision between then Laurentia and possible Amazonia resulted that the Rodinia
supercontinent was formed by the agglunation of the existing cratonic fragments. Ro-
dinia supercontinent -related collisional tectonic affected the southwestern EEC. Pas-
sive continental margins heralding incipient break-up began to form along it northeas-
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