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
7 Conclusions
The conclusions summarize the sedimentological basin analysis presented in the thesis
and main results achieved from the Telemark basin-fills.
I The Telemark basin-fills represent a tectonic-sedimentary evolution from the ex-
tensional continental rift to the strike-slip influenced tectonic setting. The prove-
nance studies indicate that the sedimentation basin was likely located near the Lau-
rentia supercontinent and moved to its present location along sinistral strike-slip
fault.
II The evolution of the Rjukan Rift Basin can be subdivided into (i) syn-rift, (ii) late-
syn rift, (iii) early-post rift, and (iv) late-post rift stages. Each stage was characte-
rized by different volcanic-sedimentary patterns, where a fluctuating basin subsi-
dence created an accommodation space for basin-fills during the pure extensional
tectonics. The accumulated basin-fills indicate sedimentation in alluvial fan, braid-
plain, fluvial, estuarine-lagoon, shallow marine and tidal environments. The lack of
a deepwater sedimentation prism and oceanic crust, and the non-evolution to pas-
sive margin setting strongly indicate that the rifting failed to complete the break-up
of the continental crust.
III The Telemark basin-fills strata are truncated by the sub-Svinsaga unconformity,
which represents a ca. 170 Ma hiatus in the stratigraphic record, marking the boun-
dary of evolution in the tectonic regimes. The sedimentological studies indicate
that this boundary was closely associated with periglacial cold-climate processes
and that the tectonic deformation and evolution was likely more intensive in differ-
ent localities.
IV The abrupt lateral lithofacies variations, coarse-grained alluvial fan sedimentation,
intrabasinal unconformities, bi-modal volcanism, and basin margin faults strongly
suggest a strike-slip influenced setting for the early Sveconorwegian units. The
evolution possibly contains a sedimentary-volcanic transpression or extension
stage to a non-volcanic and sedimentary dominated transtensional stage. The fault-
ing and volcanism was probably activated either at a later stage during the basin
evolution or in certain individual basins.
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