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

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

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

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

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

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

7. Worldwide examples Introduction

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

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

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

11. 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 Introduction

12. 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 Introduction

13. Location Study area

14. Location Study area

15. Location Study area

16. Location Study area

17. Stratigraphy Study area

18. Stratigraphy Study area

20. Stratigraphy Study area

22. Stratigraphy Study area

24. Stratigraphy Study area

26. Stratigraphy Study area

28. Stratigraphy Study area

30. Stratigraphy Study area

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 Simplified Geological Map (after Uhlig, 1999 and Garcia, 2003 unpublished) Study area

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 Simplified Geological Map (after Uhlig, 1999 and Garcia, 2003 unpublished) Study area

34. Schematic Profiles Study area

35. Oxaya Anticline Geometry Anticline structure

36. Oxaya Anticline Geometry Anticline structure

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

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

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

40. Spatial distribution of structures Anticline structure

41. EW Spatial distribution of structures Anticline structure

42. Spatial distribution of structures Anticline structure

43. WE Spatial distribution of structures Anticline structure

44. Spatial distribution of structures Anticline structure

45. EW Spatial distribution of structures Anticline structure

46. Spatial distribution of structures Anticline structure

47. WE Spatial distribution of structures Anticline structure

48. Spatial distribution of structures Anticline structure

49. Spatial distribution of structures Anticline structure

50. Timing of anticline growth Interpretation

51. Lluta collapse Timing of anticline growth Interpretation

52. Oxaya Surface Diablo EW Timing of anticline growth Interpretation Eroded area

53. SN Timing of anticline growth Interpretation

54. Conclusion The Formation of the Oxaya Anticline was enhanced by the incision of the studied valleys. Incision amplified buckling occurs also in regions not representing fold and thrust belts. The Oxaya Anticline is coherent with the results of numerical modelling of transverse rivers. Existing deformation can be substantially enhanced by surface processes

55. Thank you!