After work as a junior factory chemist, Stubblefield moved to London to continue his education in evening classes at the South-Western Polytechnic (later Chelsea College).
[4] In 1923, Stubblefield was appointed demonstrator in geology at Imperial and began research into the early Palaeozoic rocks of Shropshire, in parallel with Oliver Bulman.
His work was supported by the Daniel Pidgeon fund of the Geological Society, and he gained his PhD in 1925.
Here he worked on the Lower Palaeozoic fossils of Shrewsbury, the Carboniferous of the coalfields of south Wales, Kent, and Cumbria.
Stubblefield was secretary of the Palaeontographical Society from 1934 to 1948, and subsequently president and compiler of the trilobite section of Zoological Record.