The sedimentation and paleohydrology of the Mesoproterozoic stream deposits in a strike-slip basin (Svinsaga Formation), Telemark, southern Norway

作者：Koykka Juha^*

来源：Sedimentary Geology, 2011, 236(3-4): 239-255.

DOI：10.1016/j.sedgeo.2011.01.010

• Braided stream
• Lithofacies
• Mesoproterozoic
• Paleohydrology
• Telemark
• Southern Norway

Ancient braided fluvial systems were affected by a lack of binding vegetation, under variable paleoclimatic conditions, and possibly characterized by unique fluvial styles during the Precambrian. Thus, the paleohydrological investigations are important in interpreting ancient fluvial systems and a comparison of different fluvial styles/systems. This study reports new paleohydrological and sedimentological data from the ca. 1.17 Ga-old fluvial deposits (Svinsaga Formation) in the Fennoscandian Shield, which is a part of the East European Craton. The Mesoproterozoic Svinsaga Formation overlies a major unconformity (sub-Svinsaga unconformity) in the Telemark Supracrustal rocks (southern Norway). The unconformity corresponding to a ca. 170-Ma hiatus (ca. 1347-1170 Ma) and carry evidence for ancient periglacial climatic conditions.
Eleven different sedimentary lithofacies and five lithofacies associations were recognized from the Svinsaga Formation. The lithofacies assemblages indicate that the formation represents a relatively high-energy braided fluvial environment. Massive breccias, massive and inversely to normally graded conglomerates, stratified sandstones and laminated and rippled mudstones, were transported by traction currents, sediment gravity flows and by suspension. The proximal part of the formation contains blockfield/blockslope accumulations and waning flood-flow cycles. These are overlain by hyperconcentrated and debris flow deposits, and ephemeral high-energy bedforms. The distal part of the formation contains dune bedforms and channel lag deposits, which indicate waning discharge fluctuations.
The paleohydrological calculations from the channel-fill conglomerates and sandstone bedforms correlate with lithofacies assemblages. The estimation of paleoslope and discharge values supports the presence of a fluvial stream rather than an alluvial fan environment. The stream power and water velocity systematically decreases towards the distal parts of the formation.
The abundance of the waning flood-flow cycles, ephemeral high-energy sedimentary deposits, and hyperconcentrated and debris flow deposits is a possible indicator of periglacial melt waters in basin margin strike-slip fault evolution. This melt water combined with abundantly available debris from the non-vegetated high-topographic landscape.

• 出版日期2011-5-1