Sorting and provenance patterns in the Usumacinta‐Grijalva delta, Mexico ______________________________________________________ Master Thesis Earth Sciences T.G.Winkels Student number: 3245799 Utrecht University Faculty of Geosciences Department Physical Geography Supervisor: W.Z. Hoek / C.A.M. Nooren Sorting and provenance patterns in the Usumacinta‐Grijalva delta, Mexico Abstract The Usumacinta‐Grijalva delta is located in southern Mexico and is characterized by the largest beach ridge plain in the world, with well over 500 consecutive beach ridges spanning roughly the last 5000 years. This beach ridge plain has the potential to be used as a high resolution paleo‐environmental record since a sequence of beach ridges can be regarded as a time‐series for coastal evolution. During the 2013 field campaign samples were taken from 70 different coring locations in a series of transects and additional corings covering the delta plain. For a selection (>200) of samples grain‐size parameters were determined according to two different methods: sieving and laser‐diffraction particle size analysis, while magnetic susceptibility was determined for all samples. End member modeling was performed on both grain size datasets, in order to unmix and quantify the relative abundance of different sediment populations. Based on provenance and sorting processes, a physical meaning has been assigned to each specific sediment population (end‐member). Based on these labels, the contribution of the different river systems and coastal sorting processes, that play a role in the coastal evolution of the Usumacinta‐Grijalva delta, were reconstructed. Using LIDAR images and sediment characteristics, five different phases of delta evolution could be identified. Keywords Beach ridges Grain size analysis Magnetic Susceptibility End‐members ___________________________________________________________________________________________________________ 2 T.G. Winkels Faculty of Geosciences Utrecht University Department Physical Geography Sorting and provenance patterns in the Usumacinta‐Grijalva delta, Mexico Contents List of figures ............................................................................................................................ 5 Acknowledgments .................................................................................................................... 7 1. Introduction ...................................................................................................................... 8 1.1 Aim of research ...................................................................................................... 9 1.2 Thesis Outline......................................................................................................... 9 2. Previous Research .......................................................................................................... 10 2.1 Beach Ridges ........................................................................................................ 10 2.2 Heavy minerals .................................................................................................... 12 2.2.1 Hydrodynamic processes ....................................................................................... 12 2.2.2 Sediment Provenance .......................................................................................... 12 2.2.3 Post‐depositional processes ................................................................................ 13 3. Regional setting .............................................................................................................. 14 3.1 Climate setting ..................................................................................................... 14 3.2 Geological setting ................................................................................................ 16 3.3 Fluvial systems ..................................................................................................... 16 3.4 Coastal setting ..................................................................................................... 17 3.5 Anthropogenic impact ......................................................................................... 17 4. Methods .......................................................................................................................... 18 4.1 Coring ................................................................................................................... 18 4.2 Ground penetrating radar (GPR) ......................................................................... 18 4.3 Grain size ............................................................................................................. 18 4.3.1 Sieving analysis .................................................................................................... 18 4.3.2 Laser‐diffraction analysis ..................................................................................... 20 4.3.3 Grain‐size statistics .............................................................................................. 20 4.4 End‐Member Modeling ........................................................................................ 21 4.5 Heavy Minerals .................................................................................................... 22 4.6 Magnetic Susceptibility ........................................................................................ 23 4.7 Chronology ........................................................................................................... 23 4.7.1 Optical Stimulated Luminescence dating ............................................................ 23 4.7.2 Radiocarbon dating ............................................................................................. 24 5. Results ............................................................................................................................. 25 5.1 Internal structure ................................................................................................. 25 ___________________________________________________________________________________________________________ 3 T.G. Winkels Faculty of Geosciences Utrecht University Department Physical Geography Sorting and provenance patterns in the Usumacinta‐Grijalva delta, Mexico 5.2 Sediments anlysis ................................................................................................. 25 5.3 Sedimentary Zone classification .......................................................................... 27 5.3 End‐Member Modeling ........................................................................................ 31 5.4.1 Choosing number of end‐members ..................................................................... 31 5.4.2 End‐member characteristics ................................................................................ 31 5.4.3 End‐member abundances .................................................................................... 33 5.5 Depth variations end‐members ........................................................................... 35 5.6 Heavy minerals ................................................................................................... 37 5.6.1 Heavy mineral percentages ................................................................................. 37 5.6.2 Heavy mineral determination .............................................................................. 37 5.4.3 Heavy mineral comparison .................................................................................. 39 5.7 End‐member labels ............................................................................................. 40 5.8 Sorting processes ................................................................................................ 40 5.7 Age models .......................................................................................................... 41 6. Paleogeographic evolution of the Usumacinta‐Grijalva delta........................................ 43 7. Discussion ....................................................................................................................... 45 8. Conclusions ..................................................................................................................... 48 9. Recommended future research ...................................................................................... 49 10. Reference list ................................................................................................................. 50 Appendix 1 Coastal Settings ................................................................................................... 53 Appendix 2 GPR Measurements ............................................................................................. 54 Appendix 3 Sieving Analysis ................................................................................................... 55 Appendix 4 End‐Member correction ...................................................................................... 56 Appendix 5 Sea level correction ............................................................................................. 57 Appendix 6 Chronology .......................................................................................................... 58 Appendix 7 Sedimentary Zone classification 1 ................................................................... 59 Appendix 7 Sedimentary Zone classification