FIGURE 4. Biostratigraphic framework for the Brazos River K-Pg boundary successions and correlation to magnetostratigraphy and international timescale. A. Calcareous nannofossils based on the schemes of Perch- Nielsen (1985) for the Cretaceous and Martini (1971) for the Paleogene (see Tantawy et al., 2011). M. prin = Micula prinsii; C. inter. = Cruciplacolithus intermedius. B. Planktonic foraminfera based on the CF scheme of Li and Keller (1998) for the Cretaceous and Berggren and Pearson (2005) for the Paleogene. P. hariaensis = Pseudoguembelina hariaensis; G. gansseri = Gannsserina gansseri; P. hantk. = Plummerita hantkeninoides; P. eugub. = Parvularugoglobigerina eugubina; S. triloc. = Subbotina triloculinoides. C. Dinoflagellate ranges based on Aydin (2013). P. grallator = Palynodinium grallator; T. pelagica = Thalassiphora pelagica; D. carposph. = Disphaerogena carposphaeropsis; C. corn. = Carpatella cornuta; D. calif. = Damassadinium californicum. D. Ammonites (this study). D. iris = Discoscaphites iris; D. minardi = Discoscaphites minardi. E. Lithostratigraphy (Smith and Pessagno, 1973; Yancey, 1996). Dashed lines indicate uncertainty in position/timing of boundary between range zone.

Published as part of Witts, James D., Landman, Neil H., Garb, Matthew P., Irizarry, Kayla M., Larina, Ekaterina, Thibault, Nicolas, Razmjooei, Mohammad J., Yancey, Thomas E. & Myers, Corinne E., 2021, Cephalopods from the Cretaceous-Paleogene (K-Pg) boundary interval on the Brazos River, Texas, and extinction of the ammonites, pp. 1-52 in American Museum Novitates 2021 (3964) on page 9, DOI: 10.1206/3964.1, http://zenodo.org/record/4566589