Procedures for diatom analyses and hydrodynamic separation of extreme wave paleo-deposits from tropical sediment environments

Abstract

Diatoms are an important proxy in tsunami and storm research studies to determine potential sediment source and changes in environments pre- and post-event. However, the use of this proxy has proven challenging when studying extreme wave paleo events in sediments from the humid tropics because of the scarcity of diatoms in sand beds, and in clay or silt beds above and below. This problem has been associated with (1) dissolution of diatom valves in the humid tropics, (2) rate of burial and poor preservation of tsunami deposits, and (3) sediment and diatom size. Here we propose a practical solution to this problem – using hydrodynamic separation in the analysis of diatoms of extreme wave paleo-deposits. We compare diatom identification results from selected sand beds and units above and below, collected in a humid tropical environment (Guerrero, Mexico) using a standard procedure and the proposed fast hydrodynamic separation procedure to concentrate diatom-sized fraction. Thanks to the newly proposed methodology, the results showed a significant improvement in the number of observed diatom data in the studied sand units. We discuss two different techniques to achieve this aim and suggest how improvements on the quantitative research of diatoms from extreme wave deposits, particularly tsunamis, from the humid tropics.