The Usumacinta–Grijalva beach-ridge plain in southern Mexico: a high-resolution archive of river discharge and precipitation
- 1Utrecht University, Faculty of Geosciences, 3584 CS Utrecht, the Netherlands
- 2Groningen University, Centre for Isotope Research, 9747 AG Groningen, the Netherlands
- 3Leiden University, Faculty of Archaeology, 2333 CC Leiden, the Netherlands
- 4Centro Federal de Educação Tecnológica de Minas Gerais (CEFET-MG), Department of Civil Engineering, CEP 30510-000, Belo Horizonte, Brazil
- 5Michigan State University, Department of Earth and Environmental Sciences, East Lansing, MI 48824, USA
- 6Queensland University of Technology, Science and Engineering Faculty, Institute for Future Environments, Brisbane, QLD 4001, Australia
- 7TNO – Geological Survey of the Netherlands, Geomodelling Department, 3584 CB Utrecht, the Netherlands
- 8Vrije Universiteit, Faculty of Earth and Life Sciences, 1081 HV Amsterdam, the Netherlands
- 9Wageningen University, Soil Geography and Landscape Group & Netherlands Centre for Luminescence Dating, 6708 PB Wageningen, the Netherlands
- 10Deltares, Department of Applied Geology and Geophysics, 3584 BK Utrecht, the Netherlands
Abstract. The beach-ridge sequence of the Usumacinta–Grijalva delta borders a 300 km long section of the southern Gulf of Mexico coast. With around 500 beach ridges formed in the last 6500 years, the sequence is unsurpassed in the world in terms of numbers of individual ridges preserved, continuity of the record, and temporal resolution. We mapped and dated the most extensively accreted part of the sequence, linking six phases of accretion to river mouth reconfigurations and constraining their ages with 14C and OSL dating. The geomorphological and sedimentological reconstruction relied on lidar data, coring transects, GPR measurements, grain-size analyses, and chemical fingerprinting of volcanic glass and pumice encountered within the beach and dune deposits.
We demonstrate that the beach-ridge complex was formed under ample long-term fluvial sediment supply and shorter-term wave- and aeolian-modulated sediment reworking. The abundance of fluvially supplied sand is explained by the presence of easily weatherable Los Chocoyos ignimbrites from the ca. 84 ka eruption of the Atitlán volcano (Guatemala) in the catchment of the Usumacinta River. Autocyclic processes seem responsible for the formation of ridge–swale couplets. Fluctuations in their periodicity (ranging from 6–19 years) are governed by progradation rate, and are therefore not indicative of sea level fluctuations or variability in storm activity. The fine sandy beach ridges are mainly swash built. Ridge elevation, however, is strongly influenced by aeolian accretion during the time the ridge is located next to the beach. Beach-ridge elevation is negatively correlated with progradation rate, which we relate to the variability in sediment supply to the coastal zone, reflecting decadal-scale precipitation changes within the river catchment. In the southern Mexican delta plain, the coastal beach ridges therefore appear to be excellent recorders of hinterland precipitation.