Applin, Esther Richards, et al.

Offprint of the paper proving that microfossils could be used to date the layers of the Earth’s crust, a key insight of modern geology. Presentation copy inscribed by author Alva E. Ellisor on the upper cover.

Lead author Esther Richards Applin (1895-1972) was an petroleum geologist at the Rio Bravo Oil Company. “In a paper presented at a Geological Society meeting in 1921 by her supervisor at Rio Bravo, Applin suggested that microfossils could be used to date strata. She was ridiculed by more experienced geologists for her audacity... To verify her claim, Applin worked with Alva Ellisor and Hedwig Kniker to find ways to separate the fossils from the matrix of the cuttings. In 1925, the three coauthored a paper that detailed the sequences and oil-bearing zones in the Gulf Coast using microfossils” (Biographical Dictionary of Women in Science p. 46).

Ellisor was one of the first professional female stratigraphers in the United States, and probably the first woman to do geological work for an oil company, the Humble Oil and Refining Company (BDWS p. 419). “Ellisor recognized the importance of combining laboratory work with field work. She examined nearly every area of the gulf coast, visiting Pliocene, Miocene, Oligocene, and Cretaceous exposures o the coast. After her first paper was published (1918), she identified the first Foraminifera ever observed on the Gulf Coast... this discovery supplied the oil industry with the means to identify these oil-bearing formations where previously they had been dependant on large fossils or fossil fragments. After this discovery, she became Humble’s first research stratigrapher and paleontologist” (BDWS). Ellisor was elected vice-president of the Houston Geological Society twice and was a Fellow of the Geological Society of America.