Distribution and carbon isotope patterns of diterpenoids and triterpenoids in modern temperate C3 trees and their geochemical significance

A comparison of terpenoid and leaf fossil vegetation proxies in Paleocene and Eocene Bighorn Basin sediments

“…It should also be noted that tetracyclic diterpenoids were included as conifer biomarkers in their study, possibly leading to some overestimation of conifers given that these biomarkers are also produced by angiosperms (e.g. Diefendorf et al, 2012). Nevertheless, the similarities between Bechtel et al (2008) and this study are striking and suggest that diterpenoids overexpress conifers in the floral community.…”

“…3) for all structures except tetracyclic diterpenoids, which have angiosperm and conifer origins (cf. Diefendorf et al, 2012). Diterpenoid abundance ranged from 0 to 87.59 lg/g C and was highest at the Fifteenmile Creek site.…”

“…More quantitatively, we modified di-to triterpenoid ratio calculations (Bechtel et al, 2003;Nakamura et al, 2010) to account for biomarker production estimated from modern vegetation (Diefendorf et al, 2012). All di-and triterpenoid-based paleovegetation proxies significantly overestimated conifer abundance compared with the megafossil estimates (Fig.…”

“…1) and high level chemotaxonomic indicators. For example, non-steroid pentacyclic triterpenoids are almost exclusively synthesized by angiosperms, whereas tricyclic diterpenoids are characteristic of gymnosperms, specifically conifers (Erdtman, 1963;ten Haven and Rullkötter, 1988;Sukh Dev, 1989;Otto et al, 1997;Otto and Simoneit, 2001;Otto and Wilde, 2001;Hautevelle et al, 2006;Keeling and Bohlmann, 2006;Cox et al, 2007;Diefendorf et al, 2012). Studies have used simple di-to triterpenoid ratios to reconstruct vegetation distribution, but few compared terpenoid abundance ratios to the relative abundance of angiosperms and conifers seen in pollen or megafossils from the same deposits (Bechtel et al, 2003;Nakamura et al, 2010).…”

“…Studies have used simple di-to triterpenoid ratios to reconstruct vegetation distribution, but few compared terpenoid abundance ratios to the relative abundance of angiosperms and conifers seen in pollen or megafossils from the same deposits (Bechtel et al, 2003;Nakamura et al, 2010). These earlier studies also did not account for biomarker production, which differs between different plant functional types (angiosperm vs. conifer; deciduous vs. evergreen), as such data have only recently become available (Diefendorf et al, 2012). As a result, there is significant uncertainty as to the value of terpenoid ratios as paleovegetation proxies in ancient sediments where biomarkers have been significantly altered or lost during early diagenesis (e.g.…”