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Insights into Basement Structure of West Siberian Basin from GRACE Satellite Gravity Data

This study uses forward and inverse modeling of GRACE satellite gravity data to gain new insights into the basement structure of the West Siberian Basin. Goals include identifying terranes, rift structures, and the thickness of the basalt layer. Results reveal rift-graben structures and high-density arches, confirming previous findings. The study also highlights the existence of crustal blocks and their smooth transition to neighboring regions. This research contributes to a better understanding of the geological characteristics of the West Siberian Basin.

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Insights into Basement Structure of West Siberian Basin from GRACE Satellite Gravity Data

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  1. NEW INSIGHTS INTO THE BASEMENT STRUCTURE OF THE WEST SIBERIAN BASIN FROM FORWARD AND INVERSE MODELLING OF GRACE SATELLITE GRAVITY DATA Gruppo Nazionale di Geofisica della Terra Solida 27° Convegno Nazionale 6 - 8 Ottobre 2008, Trieste Carla Braitenberg Department of Earth Sciences, Trieste University Jörg Ebbing Geological Survey of Norway, NGU, Trondheim Department for Petroleum Technology and Applied Geophysics, NTNU Trondheim

  2. Overview • Goals • Starting point and data • Gravity field modelling and inversion • Results and conclusions

  3. Goals • Identification of terranes of WSB • Identify rift structure and relation to underlying crust WSB • Thickness of basalt layer • Interpretation of the gravity field in WSB

  4. Starting point • Gravity anomaly and Geoid undulations • Regional seismic profiles • Sediment thickness (pre- and post volcanic) • Moho model • Uncertain basalt layer extent • Hypothesized rifts in basin • Vyssotski et al., 2006

  5. Topo

  6. Global gravity fields • Grace satellite • given in spherical harmonic development. • GFZ-Potsdam (Förste et al., 2008): EIGEN-GL04C • Up to degree and order 120: satellite only. • Up to degree and order 360: integration with terrestrial data.

  7. Gravity anomaly

  8. Bouguer field

  9. Gravity Modeling • Gravity effect of known masses: • Crustal thickness variation • Fixed density contrast • Sediments • Compaction: density increase with depth • Use velocity increase with depth

  10. Moho (Kovylin, 1985)

  11. Moho gravity

  12. Base pre-volcanic sediments

  13. Converting TWT to velocity-depth

  14. Gravity of sediments

  15. Residual gravity

  16. Gravity Inversion • Residual Gravity • after correction of known masses • Gravity inversion of residual • Superficial mass • 5 km reference depth, fixed density contrast • Lower crust • Density variation in layer 20 km above Moho

  17. Residual gravity- low pass filtered (150km) mgal

  18. Residual gravity high-pass filtered

  19. Lower crustal density variation

  20. Surface layer inversion

  21. Crustal model gravity

  22. Isostatic anomaly Loads: topography and sediments mgal

  23. Interpretation

  24. Results 1/4 • Rifts: positive gravity anomaly • Basalt fill necessary: up to 3 km thick. • Rift-graben structures identified • Koltogor- Urengoy • Khudottey -> 100 km west • Khudosey • North and SouthKhatanga • Yenisey • Ob

  25. Results 2/4 • Deviation from classical relation Topography- Bouguer anomaly • Density increase needed in lower crust to explain gravity field • Arch-like structure along eastern border to Siberian craton • NE-SW trending mid-basin high density anomaly • Extending from Pur Taz South-westwards

  26. Conclusions 1/2 • Rift structures: • Yenisei rift (1500 km length) underlain by high density arch • rifts in mid basin: underlain by moderately increased density • Compares well to results from QUARTZ (Morozova et al., 1999) deep seismic profile

  27. Conclusions 2/2 • Crustal blocks: • South-, Mid-, North- and Northwest- segments of basin • Smooth transition to Kara Sea and Yenisey-Khatanga trough • Eastern Arch

  28. Thank you for your attention! Reference: the work is summarized in the paper: Braitenberg C. and Ebbing J. (2009) New insights into the basement structure of the West Siberian basin from forward and inverse modelling of GRACE satellite gravity data, in editorial process Journal of Geophysical Research.

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