Life and Legacy
Joseph Cushman is a founding father of American micropaleontology. He was a pioneer in the use of foraminifera to support oil exploration in North America, developing a classification method that for the first time allowed foraminifera to be used for borehole correlation. In the early years of oil exploration, Cushman's emerging science made him an indispensible resource to those who went on to become the founders of "Big Oil" in the States. The scientific independence he achieved through his consulting work with oil companies led Joseph Cushman to transform micropaleontology over decades of collaboration with scientists, including many who trained with him in his Sharon, Massachusetts home and laboratory.
What are foraminifera and their importance to global stratigraphy?
Foraminifera are single-celled, typically shell-forming amoeboid protists that are abundant in ocean habitats ranging from shallow marshes to deep abyssal depths. Foraminifera shells are preserved in sediments around the world. Shells are commonly subdivided by chambers added during growth though some forms occur as simple tubes or hollow spheres. The size of the foraminiferal shell generally ranges from 0.05 mm to 0.7 mm, although some may be as large as 20 cm in diameter. Benthic (bottom dwelling) foraminifera evolved during the earliest Cambrian time (~540 million years ago) and are highly diverse, with over 4000 species existing today. Benthic species ranges are generally long (averaging about 20 million years) and some species are extremely useful for determining sediment ages. The diversity and type of benthic foraminifera allow determinations of ancient environmental conditions such as depth, oxygenation, and salinity. Planktonic (floating) foraminifera evolved during the middle Jurassic (~170 million years ago) and are quite low in diversity, with 40 species living in the upper water column of the ocean today. Because of their relatively short species duration (averaging ~5 million years) planktonic foraminifera are very useful for determining the age of ancient marine sediments.
Classification of forams:
Cushman wrote the textbook on it and why his method was so important
At the turn of the twentieth century foraminifera were studied by relatively few researchers who were interested more out of curiosity than for understanding their taxonomy and evolution. Beginning with his 1906 commission to study foraminifera obtained from dredges taken during expeditions of the U.S. Fish Commission steamer, the Albatross, Joseph Cushman realized that the existing foraminifera taxonomy was grossly oversimplified and a new classification based on careful observations from the stratigraphic record would provide the basis for understanding their taxonomy, diversity and phylogeny (history of relationships) through time. Financial compensation for his study of the Albatross collections and his employment with the U.S. Geological Survey and the Marland Oil Company enabled Cushman to travel abroad to study foraminiferal collections housed at museums in London, Vienna, and Berlin. His observations and illustrations of important museum type specimens, accumulation of a vast library of foraminiferal publications and study of foraminifera samples from a wide range of ages and environments led Cushman to develop a much more complex classification scheme. Though his new scheme was initially considered unorthodox and unusable by his colleagues, Cushman's belief in the value of foraminifera in stratigraphic correlation and his new classification scheme gradually became broadly accepted by his colleagues, particularly after publication in 1928 of his book Foraminifera, Their Classification and Economic Use. The following three editions of his book included a number of improvements to Cushman's taxonomy and classification scheme, and much the basic taxonomic and phylogenetic framework is still regarded as valid today. While the taxonomy and phylogenetic history of foraminifera has vastly increased in detail and complexity since Cushman's death in 1949, his contributions to their study led to many new discoveries and a significant increase in understanding the geologic history of the earth.
How Foraminifera Changed Oil Exploration
The exponential increase in the use of oil combustion engines during the early 1900s led to tremendous growth in the demand for petroleum and the global search for major petroleum deposits. Scientists quickly realized that invertebrate fossils, which had traditionally been used for geologic age determinations in field mapping, could not be used to monitor progress during borehole drilling because they were destroyed by the drill bit and became unidentifiable among the small sediment chips brought to the surface as borehole cuttings. During his consulting work with the Marland Oil Company in the early 1920s, Joseph Cushman demonstrated that the small size of foraminifera, their abundance in a small amount of sediment and their utility as age and environmental indicators made them extremely useful for borehole age determinations and correlation of subsurface strata. Financial support for the study of well samples from Marland Oil soon provided the funds for the construction of the Cushman Laboratory building, the training of students and the publication of scientific results in a new journal called the Cushman Laboratory for Foraminiferal Research Contributions. The petroleum industry continues to be a major employer of foraminifer paleontologists today with the increased need to precisely determine the age and structure of rock strata.
- Selected correspondence between Joseph Cushman and Marland Oil