Sorting and provenance patterns in the Usumacinta‐Grijalva delta, Mexico
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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.