Harry E. Wheeler, who served as UW geology professor from 1948 to 1976, was "the chief theoretical architect of sequence stratigraphy, the foremost concept now used by all petroleum and many mining companies to explore for oil, gas, and mineral deposits," notes UW geologist Eric Cheney.
Stratigraphy refers to the study of layers of sedimentary and volcanic rocks. These series of layers, deposited under related environmental conditions and appearing in chronological order, may reveal relationships between rock masses within a continent and even beyond; and they tell the story of how geological features have changed over time.
Cheney reflects that in the 1960s, and indeed until the 1980s, almost all geoscientists scoffed at the notion put forth by Wheeler that stratigraphic sequences extended across North America and even to Great Britain and Russia. It was a concept ahead of its time, before the idea of continental plate tectonics was developed to explain how land masses of the earth's crust have shifted and collided over geologic time, causing the same stratigraphic sequences to occur on different continents.
In the 1950s, Wheeler published many papers on the principles of stratigraphy, and in 1959 published on unconformity-bounded units. An unconformity is a break or gap in the geologic record, where the layers are missing because of erosion or other processes. He used stratigraphic principles to show, for example, that the Columbia River basalts once extended over, not below, the Cascade Range of Oregon. Professor L. L. Sloss of Northwestern University and his coworkers were the actual discoverers of sequence stratigraphy in the late 1940s in the area of Dillon, Montana, but Sloss credits Wheeler with establishing the theoretical framework for studying stratigraphy and for recognizing the meaning and importance of unconformities in the geologic record.
Cheney reflects that Wheeler's concepts of time-stratigraphy, unconformity-bounded sequences, long-distance correlation, and global changes of sea level were not widely accepted until after 1977, when Peter Vail, former student of Sloss, and colleagues at Exxon published a landmark paper on seismic stratigraphy. They used artificially-produced ground vibrations reflected off rock layers and computer technology to image stratigraphic sequences. Rumor has it that Vail burst from his office at Exxon crying "Eureka, I have discovered Wheeler!" although "this could be apocryphal," says Cheney.
"While alive, Harry rarely received the recognition he was due," notes Cheney. "He had neither seismic stratigraphy as a method nor plate tectonics as a conceptual basis. Like all great concepts, it seems simple and obvious in hindsight. It is so obvious and powerful that, as one of the previous scoffers, I'm one of those now bringing sequence stratigraphy to some of the world's oldest (1.4- to 3.1-billion-year-old) rocks."
A report of the International Subcommission of Stratigraphic Classification in 1987, the year Wheeler passed away, acknowledged Wheeler's role as the first to recognize and understand unconformity-bounded stratigraphic sequences.