Mid-Cretaceous pCO(2) based on stomata of the extinct conifer Pseudofrenelopsis (Cheirolepidiaceae) by Haworth, M, Hesselbo, S, McElwain, J, Robinson, SA, Brunt, J

“…Samples are from nonmarine to marine strata of the Wealden and Lower Greensand Groups of England and the Potomac Group of the eastern United States, of Hauterivian to Albian age (136-100 Ma). …”