BOB DOTT'S CONTRIBUTIONS TO TECTONIC HISTORY AND SEDIMENTARY GEOLOGY IN SOUTHWESTERN OREGON

For nearly a quarter century, Robert (Bob) H. Dott Jr. (1929–2018) worked to elucidate Oregon geology, starting in the mid-1950s while working in the petroleum industry, followed by leading field camps and overseeing student research projects within the complex Mesozoic-Cenozoic geology of coastal southwest (SW) Oregon. Bob possessed a talent for recognizing and tackling classically important problems. While tectonic interpretations of SW Oregon evolved rapidly during this era, the underlying geology and sedimentology work by Dott and his students/colleagues has stood the test of time.

Bob and his ‘University of Wisconsin contingent’ of graduate students and colleagues viewed SW Oregon “as a laboratory for investigating relations between tectonism and sedimentation in an orogenic belt.” This paradigm facilitated application of developing plate tectonics and terrane accretion ideas. USGS geologists worked with Dott and incorporated his mapping into their delineation of tectonostratigraphic terranes and recognition of varied structural histories, regional terrane boundaries, and timings of terrane accretion.

This stratigraphic and tectonic framework was a springboard for sedimentary studies of Mesozoic to Cenozoic sequences, beginning with Dott’s 1966 work on Eocene deltaic sedimentation and paleogeography, followed by slope deposit studies with K. Bird and a systemic analysis of Eocene facies and diagenesis with M. Chan. Work on turbidites and other gravity-flow deposits occupied Dott students working on Mesozoic strata, including K. Aalto. Studies of hummocky cross-stratification in both Cretaceous and Eocene strata led to a sedimentologic synthesis with J. Bourgeois of this distinctive structure and its variable bedding sequences. These coastal exposures were important training grounds for students and industry groups.

Dott’s undergraduate and graduate students, their academic offspring, and other researchers built on his seminal work, to establish newer lithostratigraphic nomenclature (e.g., A. Niem) and sequence stratigraphic concepts. Those who have followed in Bob’s footsteps have immensely enjoyed combining outstanding geology with an appreciation of the idyllic landscape of the Oregon coast.