In this paper we present a method for estimating soil pCO2 in ancient environments using the measured carbon-isotope values of pedogenic carbonates and plant-derived organic matter. The validity of soil pCO2 estimates proves to be highly dependent on the organic δ13C values used in the calculations. Organic matter should be sourced from the same paleosol profiles as sampled carbonates to yield the most reliable estimates of soil pCO2. In order to demonstrate the potential use of soil pCO2 estimates in paleoecological and paleoenvironmental studies, we compare samples from three Upper Jurassic localities. Soil pCO2 estimates, interpreted as a qualitative indicator of primary paleoproductivity, are used to rank the Late Jurassic terrestrial environments represented by the Morrison Formation in western North America, the informally named Lourinhã formation in Western Europe, and the Stanleyville Group in Central Africa. Because modern terrestrial environments show a positive correlation between primary productivity and faunal richness, a similar relationship is expected in ancient ecosystems. When the relative paleoproductivity levels inferred for each study area are compared with estimates of dinosaur generic richness, a positive correlation emerges. Both the Morrison and Lourinhã formations have high inferred productivity levels and high estimated faunal richness. In contrast, the Stanleyville Group appears to have had low primary productivity and low faunal richness. Paleoclimatic data available for each study area indicate that both productivity and faunal richness are positively linked to water availability, as observed in modern terrestrial ecosystems.
Supplementary Figure 01
Composite stratigraphic sections for the Lourinhã formation in the Portugal study area. Shading indicates pedogenically modified strata. White triangles and black circles denote positions of pedogenic carbonates and organic matter samples used in pCO2 calculations.
11005 Myers Suppl Figure 01.tif
Supplementary Figure 02
Composite stratigraphic sections for the Morrison Formation at the three localities in the Western U.S. Shading indicates pedogenically modified strata. White triangles and black circles denote positions of pedogenic carbonates and organic matter samples used in pCO2 calculations.
11005 Myers Suppl Figure 02.tif
Supplementary Figure 03
Stratigraphic section for the Stanleyville Group in the Samba Core. Modified from Cahen et al. (1959). Light blue shading indicates pedogenically modified strata. White triangles and black circles denote positions of pedogenic carbonates and organic matter samples used in pCO2 calculations.
11005 Myers Suppl Figure 03.tif
Supplementary Figure 04
Stratigraphic variation in carbon-isotope values for pedogenic carbonates and organic matter from the Lourinhã and Morrison formations. (A) Pedogenic carbonates from northern section of Lourinhã formation, (B) Pedogenic carbonates from southern section of Lourinhã formation, (C) Pedogenic carbonates from Ghost Ranch section of Morrison Formation, (D) Pedogenic carbonates from Shell section of Morrison Formation, (E) Organic matter from northern section of Lourinhã formation, (F) Organic matter from southern section of Lourinhã formation.
11005 Myers Suppl Figure 04.tif
Supplementary Table 01
Carbon-isotope values of pedogenic carbonate samples (n = 56) from the Lourinhã formation. Values range from -10.66‰ to -5.31‰, with an average of -8.30‰.
11005 Myers Suppl Table 01.doc
Supplementary Table 02
Carbon-isotope values of pedogenic carbonate samples (n = 32) from the Morrison Formation. Values range from -6.96‰ to -3.28‰, with an average of -5.71‰. Ghost Ranch, NM; SH = Shell, WY; MD = Bridger, MT.
11005 Myers Suppl Table 02.doc
Supplementary Table 03
Carbon-isotope values of carbonate samples (n = 7) from the Stanleyville Group. Only CS34 is suitable for use in soil pCO2 calculations. See text for discussion.
11005 Myers Suppl Table 03.doc
Supplementary Table 04
Carbon-isotope values of plant-derived organic matter from the Lourinhã formation (n = 66). Values range from -29.36‰ to -20.18‰. The average δ13C value for all samples is -22.33‰. PT = northern section; PL = southern section.
11005 Myers Suppl Table 04.doc
Supplementary Table 05
Carbon-isotope values of plant-derived organic matter from the Morrison Formation (n = 4). Values range from -22.28‰ to -18.68‰. The average δ13C value for all samples is -21.04‰. GR = Ghost Ranch, NM; MD = Bridger, MT; SH = Shell, WY.
11005 Myers Suppl Table 05.doc
Supplementary Table 06
Carbon-isotope values of plant-derived organic matter from the Stanleyville Group (n = 5). The average δ13C value for all samples is -24.30‰. Only samples CS21 and CS29 are potentially Upper Jurassic; all other samples are Lower Cretaceous.
11005 Myers Suppl Table 06.doc