Introduction

Abstract

There were an enormous number of striking geologic discoveries made and geologic theories created in the twentieth century. All of these bear importantly on marine geology. Four findings stand out: (1) plate tectonics (linked to continental drift and based largely on the geomorphology of the seafloor, geomagnetism surveys, heat flow patterns, and earthquakes at sea), (2) Orbital Ice Age Theory (informed by solar system astronomy and confirmed by the study of deep-sea sediment), (3) stepwise Cenozoic cooling (based on results from deep-sea drilling), and (4) confirmation of the impact theory for the end of the Mesozoic (clinched by stratigraphy of pelagic sediments). The respective widely recognized pioneers are (1) a number of largely US American and British geologists, geophysicists, and geomagnetists (e.g., Lamont’s marine geologist Bruce Heezen (1924–1977), the US Navy’s Robert Dietz (1914–1995) and Harry Hess (1906–1969), the UK geophysicist Fred Vine (Ph.D. 1965, Cambridge)), and also the German meteorologist Alfred Wegener (1880–1930); (2) Milutin Milankovitch (1879–1958), Serbian astronomer and civil engineer, and two astronomers (John Stockwell and Urbain Le verrier) delivering input to his calculations (The leading contemporaneous proponent of orbital forcing is André Berger, Belgian astronomer and climatologist.); (3) contemporaneous pioneers are the NZ-US marine geologist James P. Kennett (Ph.D. 1965, Wellington), the British geophysicist Nick Shackleton (1937–2006), the isotope chemist Sam Savin (Ph.D. 1967, Pasadena), and the geologist Robert Douglas (Ph.D. 1966, U.C. Los Angeles); and (4) the impact pioneers are the German-Swiss geologist and paleontologist Hanspeter Luterbacher, the Italian geologist Isabella Premoli Silva, and the Californian physicist Luis Alvarez (1911–1988) and his geologist son Walter (Berkeley) and their associates F. Asaro (1927–2014) and H. Michel (Berkeley). The crucial papers and books were published (1) in the 1920s and 1960s (Continental Drift and Plate Tectonics), (2) in the 1920s and 1980s (Orbital Ice Age Theory, proposed and verified), (3) in the 1970s (microfossils and oxygen isotopes), and (4) in the 1960s and 1980s (sudden end-of-Cretaceous mass extinction documented in pelagic sediments on land and iridium maximum found, respectively).