Are neobiota a biostratigraphical and biological marker of the Anthropocene?

The translocation of neobiota across the globe as a result of anthropogenic activity has fundamentally reconfigured the biosphere. This has accelerated since the mid-20th century, mirroring the trends observed in the ‘Great Acceleration’. Analysis of first occurrence records of neobiota in San Francisco Bay and across the conterminous USA has demonstrated that regional and continental trends show similar patterns of an acceleration in introduction rate in the mid-20th century. This fundamental perturbation to global ecologies will likely be recorded in the biostratigraphic record, particularly by widespread organisms which have a high preservation potential. High-resolution analysis of the biostratigraphic record of neobiotic introductions in San Francisco Bay has quantified a detailed record of biological and environmental disturbance. This analysis has shown that historical records of neobiotic introductions can be observed in the biostratigraphic record. Additional proxies of anthropogenic modification, including radiogenic isotopes, mercury, δ¹³C, δ¹⁵N, spheroidal carbonaceous particles and heavy metals have been analysed to assess the potential for San Francisco Bay as a site containing the Anthropocene Global Boundary Stratotype Section and Point (GSSP). The low activity levels of radiogenic isotopes in the core preclude the definition of a continuous chronology and the core lacks the clearly defined profile of ¹³⁷Cs and ^239,240Pu that is synonymous with Anthropocene stratigraphies. However, the highly-resolved biostratigraphy based on neobiotic occurrences suggests that San Francisco Bay may be an excellent site for correlating global sedimentary successions and may be suitable as an auxiliary stratotype of the Anthropocene. This is supported by quantitative biostratigraphic methods, which demonstrate that biostratigraphic events including the introductions of neobiota can be used to correlate horizons across San Francisco Bay. A late-20th century interval, defined by the arrivals of Trochammina hadai Uchio, 1963 and Potamocorbula amurensis (Schrenck, 1862) in San Francisco Bay in 1983 and 1986, can be correlated across the conterminous USA, with sedimentary deposits formed in the 1980s containing first occurrences of neobiota with a demonstrable fossil record in their introduced range.