Dr. Berger's research efforts have exploited his interests in the application of physical methods to geological problems. In practice, this has meant largely geochronological methods (e.g. Ar-Ar dating), though he has had practical experience with some geophysical exploration methods. Dr. Berger also has interests in the development and application of luminescence dating methods for Quaternary deposits. His efforts have culminated in the development of a new method of tephrochronometry, using the luminescence from ash sized glass, and in the extension of TL sediment-dating procedures to eolian silt (loess) as old as 800,000 years, previously thought to be well beyond the practical limits of this dating method, to a variety of waterlain sediments (lake, glaciolacustrine, glaciomarine, Arctic Ocean, floodplain, deltaic, lagoonal), and to neotectonic and paleoanthropoligical settings.