R. H. DOTT, JR. -- PROTEAN GEOLOGIST

Bob Dott was a geology student during the Old Regime, in the 1950’s, when the geosynclinal theory ruled. He amplified his natural love of mountains with a PhD project mapping ranges in the Great Basin: deformed late Paleozoic strata with brachiopods and fusulinids, two summers of section measuring, formation defining, thin sections, peels, and insoluble residues. His training was classical and general, his interests broad, and his thesis advisor encyclopedic. When the Revolution arrived, Bob made a seamless transition to plate tectonics, most notably with his research on the Pacific margins. In 1972 he convened an international symposium to summarize sedimentation in evolving mountain systems on active margins.

By the late 1960’s, situated at the University of Wisconsin, in the middle of the craton, Bob began his work on the local rocks — lower Paleozoic strata dominated by quartz sandstones and carbonates. By this time the lithofacies concept had broadened to include many lines of evidence beyond mineralogy: grain size and shape, sedimentary structures, body and trace fossils. Bob’s wide interests and intellect were ideal for this approach. With a bevy of students and soft-rock colleagues, he elucidated the depositional environments of the whole pre-Silurian column: eolian erg dunes, fluvial bars on a plant-free plain, rocky shorelines, beach/foreshore deposits, tidal flats, storm-dominated marine sands, burrowed carbonate-silty mixtures in the far offshore shelf, non-depositional glauconite lags, stromatolitic shoals, semi-pelagic layer-cake carbonates, hardgrounds, paleosols, and, significantly, cryptic disconformities. When the second generation of sequence stratigraphy burst onto academia, Bob embraced that approach too. The sequence concepts, modified for the cratonic interior, led to revised interpretations of the Wisconsin column. Those disconformities now took center stage. The previously-identified environmental snapshots were put into chronology, and a new relative sea level curve was the result.