33 rd IGC Excursion 24, August 3 5, 2008 Interactive map, photos and notes to the localities

Transcription

1 33 rd IGC Excursion 24, August 3 5, 2008 Interactive map, photos and notes to the localities From Epicontinental Sea to Foreland Basin. The Early Palaeozoic of the Oslo Region. Basin development, stratigraphy, sedimentology and Caledonian tectonics Snorre Olaussen (snorre.olaussen@eninorge.com), Bjørn T. Larsen (BjornTore.Larsen@detnor.no) and Fredrik Bockelie (bockelie@sagex.no) Next slide Content Slide 2: Overview of the names of the stops/localities and what to see Slide 3: Stratigraphic column with main strata to visit Slide 4: Interactive location map Slides 5 to 30: figures from the localities with some description and interpretation

2 Excursion start 0830 Meeting point Oslo - outside main entrance old university Karl Johans gt. 47 Click for map Phone; S. Olaussen Meeting point Harbor west of Akershus Castle (further info will be given first day) Meeting point Outside Sundvolden hotel 0800 (further info will be given second t day) Next slide

3 Day 1 Day 3 Day 2 Next slide Lower Palaeozoic stratigraphy of the Oslo Region. Main stratigraphic units to be visited during the excursion

4 Day 1 localities Day 2 localities Day 3 localities Boat and bus Summary 2.6 Hotel 2 nd Night 2.5 Hotel 1 st Night Boat and bus Bus Click on localities for interactive viewing

5 Day 1 Stop 1. Høvikvollen. Middle Cambrian transgression onto the Pre-Cambrian peneplain Details of the Middle Cambrian unconformity and flooding surface at Høvikvollen. Irregular granitic surface topography is filled with conglomerate and sandy/gravel rich dark limestone with trilobites.

6 Day 1 Stop 2. Grundvik. Late Cambrian Alum Shale Formation to Early Ordovician limestone (Huk Formation), Caledonian tectonism (Fig 1 of 2) Click for next figure Geological map of the down-faulted (Permian tectonics) Late Cambrian/Early Ordovician folded strata at Grundvik. Picture shows organic rich alum shale with carbonate concretions.

7 Day 1 Stop 2. Grundvik. Late Cambrian Alum Shale Formation to Early Ordovician limestone (Huk Formation). Caledonian tectonism (Fig 2 of 2) Dipping Ordovician strata of shales and nodular limestone. Insert shows large cephalopod.

8 Day 1 Stop 3. Slemmestad. (Short stop) Middle Cambrian transgression, flooding and development of organic rich mudstone (Alum Shale Formation) Carbonifereous sill Middle Cambrian Alum shale Middle Cambrian Limestone Precambrian basement Granitic gneisses Middle Cambrian unconformity and flooding and development of organic rich mudstone (Alum Shale Formation). Section preserved due to overlying Carboniferous sill.

9 Day 1 Stop 4. Arnestad. (Short stop) Middle Ordovician nodular limestone and shale (Arnestad Formation) interbedded by volcanic tuff Early volcanic tuff in the Oslo Region, probably related to volcanism of the evolving Caledonides in West or North. Photo H.A. Nakrem

10 Day 1 Stop 5. Spirodden. Early Silurian shales, renewed siliciclastic basin fill and preserved sea floor fauna. Cyclic dm to meter scale units from shales and siltstone to wave rippled very fine grained sandstone in upper part. Interpreted as distal offshore cu/fu para-sequences, probably related to distal response to prograding and retrograding shorelines in West or North. Insert shows corals and stromatoporoids in growth position higher up in the formation. Llandovery, Solvik Formation.

11 Day 1 Stop 6. Holmenskjæret Late Ordovician fauna and flora Folded Ordovician strata in the Asker - Børum area. Insert shows geological map of the Holmen/Sandvika area. Blue greenish colour is the marine Cambro- Silurian. Note the northeast-southwest striking fold axes.

12 Day 2 Stop 1. Hovedøya. Relative sea level changes in the Late Ordovician and the boundary to the Silurian (Fig 1 of 2) Click for next figure Location 2. 1 Geological map of Hovedøya.

13 Day 2 Stop 1. Hovedøya Relative sea level changes in the Late Ordovician and the boundary to the Silurian (Fig 2 of 2) Ordovician Silurian Figure to the left shows inverted Late Ordovician strata with small incised valley filled with limestone boulders at the base and mixed siliciclastic carbonates in the upper part. Right figure shows the Ordovician-Silurian boundary. Langøyene and Solvik Formations.

14 Day 2 Stop 2. Rambergøya. Facies changes and sequence stratigraphy of the Late Ordovician Mixed siliciclastic carbonate shoreline deposits with recognizable foreshore deposits. The fisherman is standing on a 2m thick fossiliferous limestone conglomerate which caps the section. Upper Ordovician, Langøyene Formation, Rambergøya. Stratigraphic-up is to the right. Inserted logs show a sequence stratigraphic subdivision based on outcrops on Rambergøya.

15 Day 2 Stop 3. Langøyene (no landing) Overview of the Late Ordovician strata Up to 2m thick limestone conglomerate (rudstone) with steep large-scale cross stratification with defined top and bottom set interpreted (e.g. small Gilbert delta). Probably infilling small basins e.g. tiny incised valleys, abundant channels e.g. tidal channels. Late Ordovician, Langøyene Formation. Langøyene. Insert shows ooliths from the same formation.

16 Day 2 Stop 4. Malmøykalven. Early Silurian facies and fauna Fossil sea floor. Crinoidal remains in the Malmøya Formation, Malmøykalven.

17 Day 2 Stop 5. Skjellegård. Early to Late Silurian stratigraphy and facies changes, from inner shelf deposits to reef and back-reef deposits (Fig 1 of 2) Click for next figure Coral and stromatoporoids in the upper part of the Braksøya Formation. Many of them are in growth position, stratigraphic-up is to the right. Wenlock, Skjellgård.

18 Day 2 Stop 5. Skjellegård. Early to Late Silurian stratigraphy and facies changes, from inner shelf deposits to reef and back-reef deposits (Fig 2 of 2) Mixed carbonate (middle part) and siliciclastic (left and right part) units interpreted to have been deposited in a tidal flat and lagoonal setting in a back-reef environment. Insert shows LLH stromatolites. Steinsfjorden Formation.

19 Day 2 Driving along E-16 (no stop) The red colored and fluvial deposited Ringerike Group, represents the final recorded basin fill of Lower Palaeozoic in the Oslo Region Low angle cut and fill channelized fluvial sandstone along the main road to Hønefoss, Ludlow, Ringerike Group.

20 Day 3 Stop 1. Frognøya. Middle and late Ordovician carbonate deposits interbedded inner shelf mudstone and sandstones. Caledonian tectonics (Fig 1 of 2) Click for next slide Stacked coarsening upward units comprising mudstones and siltstones capped by wave rippled very fine grained sandstone and sandy/silty limestone. The section is interpreted as inner shelf deposits alternating between below and above storm wave base. Frognøya, Hole.

21 Day 3 Stop 1. Frognøya. Middle and Late Ordovician carbonate deposits interbedded inner shelf mudstone and sandstones. Caledonian tectonics (Fig 2 of 2) Thrust fault at the southwestern coast of Frognøya, Hole.

22 Day 3 Stop 2. Svartøyene. Late Ordovician transition from inner shelf mudstones to shoreline sandstones to a carbonate platform with well-developed reef deposits. Oil stained limestones (Fig 1 of 2) Click for next figure Fine to low angle trough cross-stratified fine to medium grained quartz arenite. Interpreted as shoreline deposits. Insert shows lower part with burrowed shales intersected by hummocky cross stratified sandstone suggesting offshore to lower shoreface deposits. Svartøya Formation. Hirnantian.

23 Day 3 Stop 2. Svartøyene. Late Ordovician transition from inner shelf mudstones to shoreline sandstones to a carbonate platform with well-developed reef deposits. Oil stained limestones (Fig 2 of 2) Carbonate build-up resting on shallow marine sandstone (offshore sand bars and shoreline). Note interfingering of shale and massive reef core carbonates and loading of the massive reef limestone. Røyse Formation, Lille Svartøya. Ashgillian. Insert shows chromatogram of the oil stained limestone.

24 Day 3 Stop 3. Rytteraker. Early Silurian siliciclastic shelf deposits passing upwards to carbonate platform with shoal and bioherm facies. Red colored shelf deposits, the Vik Formation (Fig 1 of 2) Click for next figure Cross stratified fossiliferous sandstone interbedded with bioturbated calcareous mudstone. Low angle normal graded cross strata (hummocky) overlain by climbing ripples and terminated by wave ripples suggest tempestites. Limovnstangen, Skinnerbukta Formation, Llandovery.

25 Day 3 Stop 3. Rytteraker. Early Silurian siliciclastic shelf deposits passing upwards to carbonate platform with shoal and bioherm facies. Red colored shelf deposits, the Vik Formation (Fig 2 of 2) Coral/stromatoporoid build-up overlying carbonate shoals. The build-up probably represents stabilization period of the shoals e.g. lower energy period due to relative sea level rise. Limovnstangen, Rytteraker Formation, Llandovery. Insert shows the overlying red colored Vik Formation.

26 Day 3 Stop 4. Geitøya. Transition from Llandovery shelf sandstone to Wenlock reef and back-reef deposits (Fig 1 of 2) Click for next figure Wenlock Llandovery The boundary between Llandovery and Wenlock is marked by an unconformity surface. The Bruflat Formation of Llandovery age consists of well sorted sandstone probably deposited in an inner shelf environment. Insert shows wave ripples on bedding surface in the sandstones. Above the unconformity surface algal/coral/stromatoporoid reefs are developed. The Braksøya Formation, Wenlock age.

27 Day 3 Stop 4. Geitøya. Transition from Llandovery shelf sandstone to Wenlock reef and back-reef deposits (Fig 2 of 2) Close up of frame builders on a patch reef within the Braksøya Formation. Former inter-reef cavities are now filled with shales and reef debris.

28 Day 3 Stop 5 Skjørvold. Tidal carbonate deposits of the Late Silurian Steinsfjorden Formation (Fig. 1 of 2) Click for next figure Red laminated and mud cracked marl overlain by thin bedded wave rippled limestone and large scale cross stratified grainstone. Interpreted upward-deepening unit from tidal flat to intertidal and low/intertidal subtidal shoals. Wenlock Steinsfjorden Formation.

29 Day 3 Stop 5 Skjørvold. Tidal deposited carbonates of the Late Silurian Steinsfjorden Formation (Fig 2 of 2) Laminated limy dolomite interpreted as algal mats deposited in high intertidal zone. Note minor dome structures in middle part of the bed. Wenlock, Steinsfjorden Formation.

30 Day 3 Stop 6 East side of Steinsfjorden, Tyrifjorden. The final recorded basin fill of the Lower Palaeozoic Oslo Region. Late Silurian fluvial sandstone (Fig 1 of 2) Click for next slide Floodplain deposits within the alluvial deposited lower part of the Sundvollen Formation, Ringerike. Sandstone units represent in-channel fill and overbank deposits (e.g. levees, floodplain, crevasses). Insert shows current ripples probably within a crevasse channel.

31 Day 3 Stop 6 East side of Tyrifjorden. The final recorded basin fill of the Lower Palaeozoic Oslo Region. Late Silurian fluvial sandstone (Fig 2 of 2) T. Halvorsen, 2002 Alluvial sandstone of the Ringerike Group. Insert from Halvorsen (2002).

32

33 Meeting point Main railway station Train to and from airport