DEVELOPMENT OF AN INTERACTIVE ONLINE DATABASE OF EAST AFRICAN TEPHRAS

Correlation of primary and secondary tephra deposits based on volcanic glass compositions is one of the most important tools currently in use for applying stratigraphic and chronological constraints to hominin and other fossil fauna from the Ethiopian Rift. Successful correlation of a new tephra to local or extrabasinal tephras requires a complete database of published and unpublished tephra analyses that includes information on chemical composition and variability, analytical methods, location, and stratigraphic and chronological information.

Creation of a database for tephra correlation is time-consuming, and there is potential for incompleteness. A single comprehensive and universally accessible database is a favorable alternative. To this end, we are developing an online database that currently contains over 500 published and unpublished analyses of tephras from Ethiopia and Kenya and includes interactive tools for searching the database and submitting new data. Each analysis entry contains information on major and trace element composition, tephra name and correlates, location, and age, as available, and includes information on analytical techniques and the source of the data. The database search engine allows the user to request analyses based on a paper reference, tephra name, range of major element compositions, or range of ages.

The online database has been used to identify local and extrabasinal correlates to tephras from the Asbole-Dikika Research Area, Ethiopia. Using the database, a list of candidate correlates was compiled for each Asbole-Dikika tephra using a composition-range search, and narrowed down based on calculated similarity coefficients and stratigraphic knowledge. This process efficiently identified correlations between Asbole-Dikika tephras and the Sidi Hakoma Tuff (3.4 Ma), the Wargolo Tuff (3.8 Ma), and the AST-3 tuff (2.7 Ma), as well as a locally extensive tephra horizon known as the Bironita Tuff (correlating to tephras dated 0.55-0.72 Ma).