A RETROSPECTIVE ON 50 YEARS OF QUATERNARY TERRESTRIAL STUDIES

About 50 years ago the U.S. hosted the VIIth INQUA Congress, from which came the comprehensive overview book “The Quaternary Stratigraphy of the United States.” A review of this volume reveals the enormous strides that have been made in reconstructing paleoclimate and Quaternary history in the U.S. and globally in the past several decades. Radiocarbon and uranium-series dating were in their infancy; luminescence and cosmogenic dating did not exist. Ages for any deposits older than the limit of ¹⁴C dating were mostly not known, although some were constrained by paleontological data, K-Ar dating, and correlation of tephra. There were only four recognized major glacial/pluvial periods! Moreover, Quaternary deposits were seen by many as the overburden that obscured “real” bedrock geology. Today, Quaternary and bedrock studies are closely intertwined and their cross-fertilization has led to broader and deeper understanding of Earth history. To take one simple example, the use of stable isotopes of oxygen and carbon in ice, marine, and terrestrial deposits to constrain Quaternary paleoclimate is now routinely applied to rocks as old as Precambrian in age. Quaternary stratigraphic studies now may require combinations of expertise in geochemistry, climate modeling, radioisotopes, and statistics, as well as time-honored methods such as physical and magnetic properties of sediments and soils, palynology, and micropaleontology. Our challenge for the future is to retain the fundamentals of our science—field-based geomorphic relationships, surficial deposits mapping, and their connections through earth-surface processes—and to fully integrate these fundamental approaches with the detailed analytical work and modeling that have overtaken the field in the past 25 years. This talk will illustrate these points through some examples of the past few decades of progress in understanding Quaternary climate history and earth surface processes based on studies of aeolian and lacustrine deposits.