Mid-Cretaceous pCO2 based on stomata of the extinct conifer Pseudofrenelopsis (Cheirolepidiaceae)
Abstract
Stomatal characteristics of an extinct Cretaceous conifer, Pseudofrenelopsis parceramosa</em> (Fontaine) Watson, are used to reconstruct atmospheric carbon dioxide (p</em>CO2) over a time previously inferred to exhibit major fluctuations in this greenhouse gas. 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). Atmospheric p</em>CO2 is estimated from the ratios between stomatal indices of fossil cuticles and those from four modern analogs (nearest living equivalent plants). Using this approach, and two calibration methods to explore ranges, results show relatively low and only slightly varying p</em>CO2 over the Hauterivian Albian interval: a low of ∼560 960 ppm in the early Barremian and a high of ∼620 1200 ppm in the Albian. Data from the Barremian Wealden Group yield p</em>CO2 values indistinguishable from a soil-carbonate based estimate from the same beds. The new p</em>CO2 estimates are compatible with sedimentological and oxygen-isotope evidence for relatively cool mid-Cretaceous climates.
- Publication:
-
Geology
- Pub Date:
- September 2005
- DOI:
- 10.1130/G21736.1
- Bibcode:
- 2005Geo....33..749H