USES OF GEOCHEMICAL AND GEOCHRONOLOGICAL DATABASES DEVELOPED IN THE U.S. GEOLOGICAL SURVEY TEPHROCHRONOLOGY LABORATORY, MENLO PARK, CA
The tephra identifications, relative ages, and correlations are further supported by a second, relational database containing field notes, locality data, petrographic, mineralogic, and chronologic data for each sample. Previously investigated tephra sample correlations are also in this database. Moreover, 40Ar-39Ar, K/Ar, INAA, ICP-MS, and other accessory data in the above databases may be used as evidence to constrain geochronologic conclusions. In the near future, we hope to integrate our geochemical and relational databases.
The Tephrochronology Laboratory databases are primarily used to help determine the ages of regional lithostratigraphic units containing geochemically identifiable tephra. However, these data sets also can be used to: 1) help map the areal distribution of tephra layers, especially in conjunction with GIS software; 2) provide age control for recurrence interval calculations of, for example, volcanic eruptions, flood events, etc.; 3) reconstruct climatic history, e.g., constrain pluvial highstands; 4) determine clay sources in Native American pottery. The tephra databases also have wide applications in environmental studies, paleontology, hydrologic modeling, and archeology, among other disciplines.