Palaeoenvironmental and palaeogeographic reconstruction of the Tequixquiac Basin, Central Eastern Mexico: Mid to late Pleistocene environments

• Main Author: Toole, E
• Format: Thesis
• Language: unknown
• Published: Liverpool John Moores University 2019
• Subjects: Sea ice
• Online Access: https://dx.doi.org/10.24377/ljmu.t.00011362; http://researchonline.ljmu.ac.uk/id/eprint/11362

This PhD research utilises, for the first time, sedimentary evidence for mid to late Quaternary environmental change in the Tequixquiac region of Central-eastern Mexico. This project has logged over 50 stratigraphic sections and geochemically analysed a 55 m lithostratigraphic sequence for multi-proxy palaeoenvironmental information. The main research objective was to develop a spatial and temporal Palaeogeographic and Palaeoenvironmental model for the study area the covered the late Pleistocene to early Holocene. The findings of the study, based on the analysis of sedimentology, micromorphology, stable isotopes δ18Ocarbonate and δ13CDIC as well as ICP-OES sediment and tephra geochemistry, LOI, AMS radiocarbon, 40Ar/39Ar and Uranium-series dating has allowed a chronologically constrained paleoenvironmental and palaeogeographic reconstruction of the study area. The results of the study suggest that the Tequixquiac Basin has undergone a significant hydrological change from perennial lacustrine to ephemeral fluvial conditions between MIS15 – MIS 1 controlled by a combination of; climatic fluctuations, expressed as depositional cyclicity driven by precessional fluctuations to insolation levels. On shorter time-scales, changes in the mean position of the ITCZ related to SST, latitudinal gradients, atmospheric surface pressure gradients, the extent of Northern Hemisphere land and sea ice cover, and oceanic circulation patterns. Fluctuations in the TOC content of sediments are thought to be related to El Niño-like (dry) and La Niña-like (wet) events. While climate is thought to have been critical to the development the Quaternary localised uplift, deformation and normal faulting have also influenced palaeohydrology and water-table elevation during the recorded depositional period (Figs 8.15 d & 8.16 d).