Juha Köykkä - Oulu

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Res Terrae, Ser. A 32, J. <strong>Köykkä</strong>, Sedimentology of the Mesoproterozoic Telemark basin-fills, South Norway: implications for sedimentation processes, depositional environments and tectonic evolution Fig. 5. Basin analysis flow chart used in this thesis (modified from Miall, 1978, 2000). Regional mapping and lithostratigraphy, lithofacies analysis, and finally paleotectonic reconstruction form a fundamental core of the analysis. The usage of sequence stratigraphy, clastic petrofacies analysis, and geochemistry depends on study purpose, and thus some methods and tools are not always needed to reach the aims of the research. 4.1 Regional mapping and lithostratigraphy The basin analyses are based on the compilation and correlation of vertical and lateral lithostratigraphic sections, which entails studies of the physical and temporal relation- ships of strata. The study of ancient sedimentary environments usually begins with regional mapping (see Fig. 5), and it includes lithostratigraphic field measurements and correlations to define the rock types, geometry, and distinct internal sedimentary struc- 38
Res Terrae, Ser. A 32, J. <strong>Köykkä</strong>, Sedimentology of the Mesoproterozoic Telemark basin-fills, South Norway: implications for sedimentation processes, depositional environments and tectonic evolution tures. Lithostratigraphic mapping and measurements of rock sequences also provides information about the changes in sedimentation processes trough time and thus provides clues to the nature of sedimentation environments and their evolution trough time. Regional mapping and lithostratigraphy analysis also integrate elements detected by facies analysis. The objective of regional mapping and lithostratigraphy is to subdivide the ob- served rocks into descriptive units by observing changes in lithology, grain size, bed- ding, color, sedimentary structures (primary vs. post-depositional), contacts, and cyclic sequences. The lithology of the sedimentary unit is mainly controlled by depositional environment, sediment supply, climate, and basin subsidence. The establishment of lithostratigraphic units in basin analysis usually starts with (i) identification of the li- thostratigraphical units and the possible stratigraphic events to be correlated at the local and regional scale (or even global). This step is followed by (ii) the identification of unconformities and their chronostratigraphic significance. The resolution of the lithostratigraphic correlation can be improved by (iii) assigning absolute ages by radi- ometric dating. The final stage, if necessary, includes (iv) establishing the formations and possible groups, members and supergroups associated with the results after the lithofacies analysis. Most of the regional lithostratigraphic framework of the study area was established in earlier works described in Chapter 1.2. In this thesis, the lithostratigraphic mapping was mainly additional data to the previous studies in the local scale. This data were used in each of the six papers. Most of the rock samples were also collected during this phase. 4.2 Facies analysis Lithofacies is defined as a body of rock or unlithified sediment that is characterized by a particular combination of lithological and physical sedimentary structures formed in sedimentary processe(s) that are distinguishable from the lithology above, below and laterally adjacent to it. Sedimentary structures play a major role in the interpretation of sedimentary environment depositional processes, hydrodynamics and, thus, facies analysis. A group of genetically related lithofacies that have some environmental significance can be combined to lithofacies associations. Lithofacies associations are a col- 39
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Juha Köykkä - Oulu

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