MAPPING AND PALEOCLIMATE SCIENCE – SMITH'S LEGACY

William Smith’s famous geologic map started a scientific conversation that has been ongoing between geologists ever since. Any Earth scientist can pick up any geologic map and almost immediately infer the relative ages of rocks as well as their likely origin and mode of emplacement and, ultimately, arrive at inferences about the geologic history of a region. By the late 20^th century a similar “common language” had been developed to facilitate understanding of the history of deep ocean sediments and past climate change--namely isostratigraphy, or more generally, chemostratigraphy. By showing that the oxygen isotope composition of the global ocean was controlled primarily by the waxing and waning of ice sheets, early giants of paleoclimatology were able to create a stratigraphic nomenclature (marine isotope stages) that allowed scientists across dozens of disciplines to instantly grasp where in time the events they studied took place. This method of “mapping” in the time domain has led to revolutions in our understanding of Earth surficial processes such as ocean circulation, orbital control of climate, sea level change, and human evolution, and continues to yield insights as new techniques and methodologies further refine our “wiggle maps” of the past.