Enhanced buckling due to river incision:

1. Enhanced buckling due to river incision: the Oxaya Antiform, northern Chile Gerold Zeilinger, Fritz Schlunegger, Univ. Bern Guy Simpson, ETH Zurich

2. Outline • Introduction • Examples of transverse rivers intersecting anticlines in compressional belts • Can incision amplify buckling also in active continental margins?

3. Outline • Introduction • Study area • Geographical position • Tectonic frame • Stratigraphy of important units • Geological overview

4. Outline • Introduction • Study area • Anticline structure • Oxaya Anticline geometry • Basement – Tertiary units unconformity • Tertiary units fold geometry • Spatial distribution of structures

5. Outline • Introduction • Study area • Anticline structure • Interpretation • Timing of anticline growth • (River incision history) • (Regional compression)

6. Outline • Introduction • Study area • Anticline structure • Interpretation • Conclusion •  Does the incision of the studied valleys influence the deformation of the surrounding Oxaya Anticline?

7. Introduction Worldwide examples

8. Introduction Worldwide examples • Pyrenees: Segre River at Oliana Anticline

9. Introduction Worldwide examples • Pyrenees: Segre River at Oliana Anticline • Swiss Alps: Reuss above Lake Lucerne

10. Introduction Worldwide examples • Pyrenees: Segre River at Oliana Anticline • Swiss Alps: Reuss above Lake Lucerne • French Alps: Fier river at Val du Fier

11. Introduction Worldwide examples • Pyrenees: Segre River at Oliana Anticline • Swiss Alps: Reuss above Lake Lucerne • French Alps: Fier river at Val du Fier • Himalaya: Arun river

12. Introduction Worldwide examples • Pyrenees: Segre River at Oliana Anticline • Swiss Alps: Reuss above Lake Lucerne • French Alps: Fier river at Val du Fier • Himalaya: Arun river • Apennine: Fold-thrust belt of the Umbria–Marche Apennines

13. Study area Location

14. Study area Location

15. Study area Location

16. Study area Location

17. Study area Stratigraphy

18. Study area Stratigraphy

19. Study area

20. Study area Stratigraphy

21. Study area

22. Study area Stratigraphy

23. Study area

24. Study area Stratigraphy

25. Study area

26. Study area Stratigraphy

27. Study area

28. Study area Stratigraphy

29. Study area

30. Study area Stratigraphy

31. Study area

32. Study area Simplified Geological Map (after Uhlig, 1999 and Garcia, 2003 unpublished)

33. Study area Simplified Geological Map (after Uhlig, 1999 and Garcia, 2003 unpublished)

34. Study area Schematic Profiles

35. Anticline structure Oxaya Anticline Geometry

36. Anticline structure Oxaya Anticline Geometry

37. Anticline structure Oxaya Formation Mesozoic Basement Basement – Tertiary units unconformity E W

38. Anticline structure Azapa Formation Mesozoic Basement Basement – Tertiary units unconformity W E Image by Michi Strasser

39. Anticline structure Tertiary Units Mesozoic Basement Tertiary Units Mesozoic Basement Tertiary units fold geometry E W Azapa Valley Lluta Valley W E

40. Anticline structure Spatial distribution of structures

41. Anticline structure E W Spatial distribution of structures

42. Anticline structure Spatial distribution of structures

43. Anticline structure W E Spatial distribution of structures

44. Anticline structure Spatial distribution of structures

45. Anticline structure E W Spatial distribution of structures

46. Anticline structure Spatial distribution of structures

47. Anticline structure W E Spatial distribution of structures

48. Anticline structure Spatial distribution of structures

49. Anticline structure Spatial distribution of structures

50. Interpretation Timing of anticline growth