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the Oxaya Antiform, northern Chile Enhanced buckling due to river incision: Gerold Zeilinger, Fritz Schlunegger, Univ. Bern Guy Simpson, ETH Zurich Slide 2 Introduction Outline Examples of transverse rivers intersecting anticlines in compressional belts Can incision amplify buckling also in active continental margins? Slide 3 Introduction Study area Outline Geographical position Tectonic frame Stratigraphy of important units Geological overview Slide 4 Introduction Study area Anticline structure Oxaya Anticline geometry Basement Tertiary units unconformity Tertiary units fold geometry Spatial distribution of structures Outline Slide 5 Introduction Study area Anticline structure Interpretation Timing of anticline growth (River incision history) (Regional compression) Outline Slide 6 Introduction Study area Anticline structure Interpretation Conclusion Does the incision of the studied valleys influence the deformation of the surrounding Oxaya Anticline? Outline Slide 7 Worldwide examples Introduction Slide 8 Worldwide examples Pyrenees: Segre River at Oliana Anticline Introduction Slide 9 Worldwide examples Pyrenees: Segre River at Oliana Anticline Swiss Alps: Reuss above Lake Lucerne Introduction Slide 10 Worldwide examples Pyrenees: Segre River at Oliana Anticline Swiss Alps: Reuss above Lake Lucerne French Alps: Fier river at Val du Fier Introduction Slide 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 Slide 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 Slide 13 Location Study area Slide 14 Location Study area Slide 15 Location Study area Slide 16 Location Study area Slide 17 Stratigraphy Study area Slide 18 Stratigraphy Study area Slide 19 Slide 20 Stratigraphy Study area Slide 21 Slide 22 Stratigraphy Study area Slide 23 Slide 24 Stratigraphy Study area Slide 25 Slide 26 Stratigraphy Study area Slide 27 Slide 28 Stratigraphy Study area Slide 29 Slide 30 Stratigraphy Study area Slide 31 Slide 32 Simplified Geological Map (after Uhlig, 1999 and Garcia, 2003 unpublished) Study area Slide 33 Simplified Geological Map (after Uhlig, 1999 and Garcia, 2003 unpublished) Study area Slide 34 Schematic Profiles Study area Slide 35 Oxaya Anticline Geometry Anticline structure Slide 36 Oxaya Anticline Geometry Anticline structure Slide 37 Basement Tertiary units unconformity Anticline structure Oxaya Formation Mesozoic Basement EW Slide 38 Basement Tertiary units unconformity Anticline structure Azapa Formation Mesozoic Basement Image by Michi Strasser WE Slide 39 Tertiary units fold geometry Anticline structure Tertiary Units Mesozoic Basement EW EW Azapa Valley Lluta Valley Tertiary Units Mesozoic Basement Slide 40 Spatial distribution of structures Anticline structure Slide 41 EW Spatial distribution of structures Anticline structure Slide 42 Spatial distribution of structures Anticline structure Slide 43 WE Spatial distribution of structures Anticline structure Slide 44 Spatial distribution of structures Anticline structure Slide 45 EW Spatial distribution of structures Anticline structure Slide 46 Spatial distribution of structures Anticline structure Slide 47 WE Spatial distribution of structures Anticline structure Slide 48 Spatial distribution of structures Anticline structure Slide 49 Spatial distribution of structures Anticline structure Slide 50 Timing of anticline growth Interpretation Slide 51 Lluta collapse Timing of anticline growth Interpretation Slide 52 Oxaya Surface Diablo EW Timing of anticline growth Interpretation Eroded area Slide 53 SN Timing of anticline growth Interpretation Slide 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 Slide 55 Thank you!