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Paleovegetation and paleoatmospheric P(CO2) levels during the Early Cretaceous: examples from the Hasandong Formation, Korea, and the Shimonoseki Subgroup, Japan
Journal of Asian Earth Sciences 21 (2003) 807–812 www.elsevier.com/locate/jseaes
Paleovegetation and paleoatmospheric P(CO2) levels during the Early Cretaceous: examples from the Hasandong Formation, Korea, and the Shimonoseki Subgroup, Japan Yong Il Lee* School of Earth and Environmental Sciences, Seoul National University, Seoul 151-747, South Korea Received 25 July 2000; revised 25 January 2002; accepted 21 April 2002
Abstract Stable carbon-isotope compositions of pedogenic carbonates occurring in two Lower Cretaceous non-marine deposits, the Hasandong Formation, Korea (Hauterivian/Barremian) and the Shimonoseki Subgroup, Japan (Aptian), provide a record of past pedogenic environments, and are used to infer paleovegetation and CO2 pressure P(CO2) of the Early Cretaceous atmosphere. The carbon isotopic compositions (2 5.6 to 26.7‰) of pedogenic carbonates from both strata suggest soils dominated by C3 type of vegetation. Atmospheric CO2 contributed generally less than 30% of the carbon isotopes to these pedogenic carbonates. The Early Cretaceous atmosphere is unlikely to have contained more than about 4500 ppm V by volume of CO2. High concentrations of carbon dioxide in the Early Cretaceous atmosphere are in good agreement with the modeled atmospheric P(CO2) estimation of Berner [American Journal of Science 294 (1994) 56 – 91]. The fact that paleo-P(CO2) levels during Shimonoseki time (1900 – 3200 ppm V) were lower than those of Hasandong time (2400 – 4500 ppm V) indicates that the paleo-P(CO2) levels in the atmosphere were lower than the Early Cretaceous high, which fits well with a trend of decreasing carbon dioxide levels in the paleoatmosphere during the Cretaceous. q 2002 Elsevier Science Ltd. All rights reserved. Keywords: Hasandong Formation; Shimonoseki Subgroup; Pedogenic carbonates; Carbon-isotope; Cretaceous
1. Introduction Stable isotope studies of pedogenic carbonate have been increasingly applied to ancient paleosols in order to study paleovegetation (Bocherans et al., 1994; Cerling et al., 1989, 1997; Koch, 1998; Latorre et al., 1997; Morgan et al., 1994; Quade and Cerling, 1995; Quade et al., 1995) and paleoclimates (Andrews et al., 1995; Ghosh et al., 1995; Mora et al., 1991, 1996; Ekart et al., 1999). Cerling (1991, 1992) provided a model for estimating ancient atmospheric P(CO2) by showing that the isotopic composition of pedogenic carbonate is directly related to soil CO2, which in turn depends on the concentration of CO2 in the atmosphere. The carbon isotopic composition of pedogenic carbonates is also sensitive to the type of vegetation (C3 versus C4 plants). This study provides the carbon-isotope geochemistry of pedogenic carbonates in two Lower Cretaceous calcareous paleosols within the Hasandong * Tel.: þ82-2-880-6736; fax: þ 82-2-871-3269. E-mail address: [email protected] (Y.I. Lee).
Formation, Korea and the Shimonoseki Subgroup, Japan (Fig. 1). Paleosols are ubiquitous in floodplain deposits of the Hasandong Formation and in the upper part of the fluvial fining-upward cycles within a mid- to distal-alluvial fans of the Shimonoseki Subgroup. Both strata are known to contain abundant pedogenic carbonates (Chang, 1975; Choi, 1985; Lee and Hisada, 1997), and Lee (1999) and Lee and Hisada (1999) studied their stable isotopic compositions. The objectives of this paper are to compare the carbon isotopic compositions of pedogenic carbonates from both strata and to discuss the estimates of partial pressures of atmospheric CO2 within the context of the estimated carbon dioxide concentrations during the Cretaceous.
2. Stratigraphy and depositional setting The Hasandong Formation is the middle stratigraphic unit of the Sindong Group, which is distributed along the western margin of the Cretaceous non-marine Gyeongsang Basin, Korea (Fig. 1). It is 550– 1400 m thick and consists of
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Fig. 1. Simplified geologic maps of (a) the Gyeongsang Basin, Korea and (b) the Kanmon Basin, Japan.
sandstones, reddish and gray silty shales, and minor conglomerates which were deposited in fluvial channels and on floodplains (Choi, 1985, 1986). The formation is underlain by the Nagdong Formation (alluvial to fluvial deposits) and is overlain by the Jinju Formation (lacustrine deposits). The geologic age of the Hasandong Formation has been generally inferred to be Hauterivian from charophytes in the underlying Nagdong Formation (Seo, 1985) and Barremian by Chang et al. (1997) (Fig. 2). Abundant fossils of vascular plants, bivalves, and some gastropods have been reported from mudstones of this formation. Most of them indicate an Early Cretaceous age and non-marine environments. The paleolatitude of the Korean Peninsula during the Cretaceous was similar to the present one (Kim et al., 1993). The Shimonoseki Subgroup is the upper clastic sequence of the Kanmon Group, which is distributed in northern Kyushu and westernmost Honshu, Japan (Fig. 1). The Shimonoseki Subgroup is about 2300 m thick, and rests disconformably on the low-lying Wakino Subgroup and
onlaps the older basement rocks. It is composed of conglomerate, sandstone, shale, tuff, tuff breccia and lavas of andesite, dacite and rhyolite. Most of its sediments are volcanogenic in origin. The age of the Shimonoseki Subgroup is dated as late Early Cretaceous (Aptian – Albian) (Kimura et al., 1991). Fossils are rare in general, but occurrences of a few freshwater bivalves (Nippononaia and Esterites ) have been reported (Hase, 1969; Kusumi, 1960). The Shimonoseki Subgroup is subdivided into three stratigraphic units: the Shiohama, Kitahikoshima and Sujigahama formations in decreasing age. In this report, pedogenic carbonates are from paleosols of the Shiohama Formation, mainly in the Yoshimi area, Yamaguchi Prefecture, western Honshu. Thus, the geologic age of the paleosol-bearing Shiohama Formation may correspond to the late Aptian. The studied section is about 200 m thick and is composed of several , 10 m thick conglomerate beds with intervening thick reddish mudrocks and thin sandstones. Sediments are interpreted to have been deposited in a mid- to distal-alluvial fan setting (Lee and Hisada, 1997).
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noseki Subgroup, respectively, are used for this study for comparison and their carbon isotopic compositions are shown in Table 1 and in Fig. 3. The carbon isotopic compositions of the Hasandong pedogenic carbonates range from 2 2.4 to 2 9.3‰ with an average of 2 5.6 ^ 1.7‰, and of the Shimonoseki pedogenic carbonates range from 2 5.4 to 2 7.7‰ with an average of 2 6.7 ^ 0.5‰. As shown in Fig. 3 the carbon isotopic compositions of the Shimonoseki carbonates are slightly more negative and are less scattered than those of the Hasandong carbonates.
5. Discussion
Fig. 2. Stratigraphic correlation between the Gyeongsang Basin, Korea and the Kanmon Basin, Japan (modified after Sakai and Okada (1997)).
3. Pedogenic carbonate Descriptions of pedogenic carbonates of these strata are given by Lee (1999) and Lee and Hisada (1999), and only a brief summary of their characteristics is given here. The Hasandong and Shimonoseki paleosols contain (1) poor stratification of carbonate nodule-bearing fines, (2) calcareous root traces and rhizoliths, (3) circumgranular and curved cracks, fitted peloids and calcite aureoles around detrital grains in calcareous nodules, (4) vertical profiles of two or more horizons with the calcic intervals present toward the base, (5) purple horizon colors, (6) beds of limeintraclast conglomerates, and (7) truncation of carbonate nodule- and lens-bearing horizons by the overlying channel deposits. Although each of the above descriptions is not conclusive, collectively they suggest that the studied carbonate nodules are of pedogenic origin. Stable isotopic measurements were performed on powdered samples collected with a dental drill, after the nodules and rhizocretions were sliced and polished to expose the fresh surface. Stable carbon isotopes were analyzed by a VG PRISM Series II Model at the Korea Basic Science Institute. The isotopic ratios of carbon are presented in standard-notation (‰) relative to PDB. Reproducibility of the analyses was ^ 0.1‰.
4. Carbon isotope composition Analyses of a total of eighteen and fifteen pedogenic carbonates from the Hasandong Formation and the Shimo-
Because its carbon is derived from soil CO2, the carbon isotopic composition of pedogenic carbonate is strongly correlated to that of soil organic matter and the overlying flora. Atmospheric CO2, which has a carbon isotopic composition less negative than that of plants, generally contributes to soil CO2 near the surface. The difference in carbon isotopic composition between coexisting soil organic matter and pedogenic carbonate is 14 – 16‰ depending on temperature. This systematic difference arises from equilibrium fractionation between carbon-isotope species and from gas diffusive effects (Cerling et al., 1989; Quade et al., 1989, 1995). The C3 and C4 plants have d 13C values of 2 27‰ (Ehleringer, 1989) and 2 13‰ (Smith and Epstein, 1971), respectively (Fig. 4). CAM plants have a range of d 13C from 2 10 to 2 20‰ (Lerman, 1972). However, they are usually insignificant in ecosystems except in some of the desert regions. In pre-industrial times, the average isotopic composition of C3 and C4 plants should have been about 2 26 and 2 12‰, respectively. However, the carbon isotopic composition of organic matter from C3-dominated modern soils and paleosols is generally about 2 24‰ (Cerling, 1992), which is used in this study as a representative value of C3-dominated vegetation. Such heavier isotopic values indicate that the C3 plants were under water stress and warm temperatures (Cerling, 1992), which is supported by the characteristics of the Hasandong and Shimonoseki paleosols (Paik and Lee, 1998; Lee and Hisada, 1997, 1999). The d 13C values of the Hasandong plant-CO2 range from 2 15.7 to 2 22.6‰ with an average of 2 18.9 ^ 1.8‰ and those of the Shimonoseki plant-CO2 from 2 18.7 to 2 21.0‰ with an average of 2 20.6 ^ 0.6‰ assuming soil carbonate in equilibrium with soil CO2 at 25 8C (Table 1). The d 13C values of estimated Hasandong and Shimonoseki plant-CO2 are at or closer to the heavy end of C3 plants (Fig. 4), which suggests that the vegetation of the Hasandong and Shimonoseki times was probably dominated by C3-type plants. However, they are heavier than the average d 13C of C3 plants which is about 2 24‰. Influence from sources with heavier carbon-isotopes needs to be considered in order to shift d 13C values of the Hasandong and Shimonoseki plant-CO2 toward the heavy end or heavier than C 3 plant range. Compared to
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Table 1 Carbon isotopic compositions of pedogenic carbonates and estimated plant CO2 of the Hasandong Formation and Shimonoseki Subgroup (after Lee (1999) and Lee and Hisada (1999)) Hasandong Formation
Shimonoseki Subgroup
Sample
d 13C (‰) carbonate
d 13C (‰) plant CO2
Sample
d 13C (‰) carbonate
d 13C (‰) plant CO2
NAM1 NAM2 NAM3 9-1 9-2 44-1 44-2 44-3 11-1 11-2 J05 337 M09 O07 O06 Bito Yusu-sept Yusu-13 Average
24.5 23.9 24.0 27.0 24.8 26.2 26.0 23.9 27.6 26.2 27.8 29.3 25.2 23.3 22.4 26.8 26.4 26.0 25.6 ^ 1.7
218.6 218.0 218.1 221.1 218.9 220.3 220.1 218.0 221.7 220.3 221.9 223.4 219.3 217.6 216.5 220.9 220.5 220.1 218.9 ^ 1.8
1-CR1 1-CR2 2-CR1 2-CR2 3-CR1 3-CR2 5-CR1 5-CR2 6-CR1 6-CR2 7-CR 8-CR 9-CR 10-CR1 10-CR2 Average
27.0 27.7 27.0 27.3 27.0 26.9 26.7 26.4 26.2 26.5 26.9 26.9 27.0 25.4 25.8 26.7 ^ 0.5
220.3 221.0 220.3 220.6 220.3 220.2 220.0 219.7 219.5 219.8 220.2 220.2 220.3 218.7 219.2 220.6 ^ 0.6
Shimonoseki pedogenic carbonates, Hasandong pedogenic carbonates would have been influenced slightly more by sources with heavier carbon isotopes. For possible sources with heavier carbon isotopes, C4 plants, atmospheric CO2, or a combination of both can be inferred. Although the existence of C4 plants in pre-Miocene time is still in dispute, the general consensus is that C4 plants evolved from C3 plants probably during the late Miocene at about 7– 8 Ma (Cerling et al., 1997; Morgan et al., 1994; Latorre et al., 1997; Quade and Cerling, 1995; Quade et al., 1995), suggesting that the influence of C4 plants is less likely. No
Fig. 3. d 13C versus d 18O stable isotope cross plot for Hasandong and Shimonoseki pedogenic carbonates.
desert-like conditions have been reported for the Cretaceous in Korea and Japan, and thus the influence of CAM plants on the formation of soil carbonates can be excluded. Accordingly, the heavier d 13C values could have resulted from contributions of atmospheric CO2, whose carbon isotopic composition was about 2 6.5‰ in pre-industrial time. The calculated contribution of atmospheric CO2 for the Hasandong Formation was about 29% and for the Shimonoseki Subgroup was about 23%. A slightly more atmospheric CO2 influence on the Hasandong carbonates can be accounted for by the shallower depth of pedogenic carbonate in its paleosols relative to the Shimonoseki paleosols. Alternatively, a high atmospheric CO2 concentration during Hasandong time might have allowed more mixing of atmospheric CO2 deeper in the soil profile. Cerling (1992) provided a diffusion-reaction model to estimate atmospheric P(CO2) using carbon-isotope ratios of pedogenic carbonates. Two extreme cases are calculated to
Fig. 4. Ranges for d 13C values of different vegetation types and Hasandong and Shimonoseki pedogenic carbonates. Inverted triangles are average values and a triangle below the C3 plant range represents d 13C of organic matter from C3-dominated modern soils (Cerling, 1992).
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Fig. 6. Estimated atmospheric P(CO2) levels during the Cretaceous. The solid curve represents the GEOCARB II model (Berner, 1994).
The low atmospheric estimates are probably due to the low porosity of lacustrine carbonates.
6. Conclusion
Fig. 5. Atmospheric P(CO2) inferred from d 13C of Hasandong (filled square) and Shimonoseki (dot) pedogenic carbonates by using the model of Cerling (1992). S(z ) represents the soil-respired component of soil CO2 [ ¼ PCO2(soil) 2 PCO2(atmosphere)].
estimate the range of the atmospheric P(CO2): warm (25 8C) with high productivity where soil-respired CO2 equals 10,000 ppm V and cool (15 8C) for low productivity where soil-respired CO2 equals 5000 ppm V. Using this model, the paleoatmospheric CO2 levels of Hasandong and Shimonoseki times are estimated to be 2400 – 4500 ppm V and 1700 –3200 ppm V, respectively (Fig. 5). Collectively, the Early Cretaceous atmosphere is unlikely to have contained more than about 4500 ppm V by volume of CO2. Several model and field-based studies were done for estimation of paleoatmospheric CO2 concentrations. The estimated atmospheric P(CO2) levels during the Cretaceous are shown in Fig. 6. The modeled values of paleoatmospheric P(CO2) generally decrease during the Cretaceous with decreasing age (Berner, 1994). As shown in Fig. 6, the general trend of all Cretaceous estimates nicely matches with the modeled trend of Berner (1994) and with a general climatic decline. However, estimates from the Cenomanian to Santonian are lacking and these data are in need of further study to confirm this trend. The values inferred from the Barremian pedogenic carbonates (Cameros Basin, Spain; Cerling, 1991) are rather low compared to predicted ones. This is because the carbon-isotope values were derived from lacustrine carbonates that were modified by pedogenesis.
Abundant pedogenic carbonate nodules are present in Lower Cretaceous non-marine deposits in Korea and Japan, the Hasandong Formation (Hauterivian/Barremian) and the Shimonoseki Subgroup (Aptian), respectively. These pedogenic carbonates are used to estimate the concentration of carbon dioxide in the Early Cretaceous atmosphere. The carbon isotopic compositions of pedogenic carbonates from both strata suggest soils dominated by C3 type of vegetation. The paleo-P(CO2) level in the atmosphere during the Early Cretaceous was unlikely more than about 4500 ppm V. The estimated high concentrations of carbon dioxide in the Early Cretaceous atmosphere are in good agreement with the modeled atmospheric P(CO2) estimation of Berner (1994). The finding that paleo-P(CO2) levels of the Shimonoseki time were lower than those of Hasandong time indicates that the paleo-P(CO2) levels in the atmosphere had dropped from the Early Cretaceous high, which fits well with a trend of decreasing carbon dioxide levels in the paleoatmosphere during the Cretaceous.
Acknowledgments This study was supported by the Korea Science and Engineering Foundation grant (2000-2-13100-003-5). I am grateful to H.S. Lim for drafting the figures. I thank the reviewers (G.J. Retallack, G.A. Ludvigson and editors C.C. Johnson, H. Hirano and K. Burke) for their helpful and constructive comments.
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References Andrews, J.E., Tandon, S.K., Dennis, P.F., 1995. Concentration of carbon dioxide in the Late Cretaceous atmosphere. Journal of Geological Society of London 152, 1–3. Berner, R.A., 1994. GEOCARB II: a revised model of atmospheric CO2 over Phanerozoic time. American Journal of Science 294, 56–91. Bocherans, H., Friis, E.M., Mariotti, A., Pedersen, K.R., 1994. Carbon isotopic abundances in Mesozoic and Cenozoic fossil plants: paleoecological implications. Lethaia 26, 347–358. Cerling, T.E., 1991. Carbon dioxide in the atmosphere: evidence from Cenozoic and Mesozoic paleosols. American Journal of Science 291, 377– 400. Cerling, T.E., 1992. Use of carbon isotopes in paleosols as an indicator of the P(CO2) of the paleoatmosphere. Global Biogeochemical Cycles 6, 307– 314. Cerling, T.E., Wang, Y., Bowman, J.R., 1989. Carbon isotopes in soils and paleosols as ecologic and paleoecologic indicators. Nature 341, 138– 139. Cerling, T.E., Quade, J., Eisenmann, V., Ehleringer, J.R., Harris, J.M., MacFadden, B.J., Leakey, M.G., 1997. Global vegetation change through the Miocene/Pliocene boundary. Nature 389, 153 –158. Chang, K.H., 1975. Cretaceous stratigraphy of southeastern Korea. Journal of Geological Society of Korea 11, 1–23. Chang, K.H., Park, S.-O., Kim, H.-S., 1997. Cretaceous stratigraphy and geologic history of medial Kyongsang Basin: tectonics and volcanism. Geoscience Journal 1, 2– 9. Choi, H.I., 1985. Sedimentology and its application for stratigraphic classifications of the Cretaceous Kyeongsang Basin. Journal of Geological Society of Korea 21, 26–37. Choi, H.I., 1986. Fluvial plain/lacustrine facies transition in the Cretaceous Sindong Group, south coast of Korea. Sedimentary Geology 48, 295– 320. Ehleringer, J.R., 1989. Carbon isotope ratios and physiological processes in arid land plants. In: Rundel, P.W., Ehleringer, J.R., Nagy, K.A. (Eds.), Applications of Stable Isotopic Ratios to Ecological Research, Springer, New York, pp. 41–54. Ekart, D.D., Cerling, T.E., Montan˜ez, I.P., Tabor, N.J., 1999. A 400 million year carbon isotope record of pedogenic carbonate: implications for paleoatmospheric carbon dioxide. American Journal of Science 299, 805– 827. Ghosh, P., Bhattacharya, S.K., Jani, R.A., 1995. Palaeoclimate and palaeovegetation in central India during the Upper Cretaceous based on stable isotope composition of the palaeosol carbonate. Palaeogeography, Palaeoclimatology, Palaeoecology 114, 285– 296. Hase, A., 1969. The late Mesozoic formations and their molluscan fossils in west Chugoku and north Kyushu, Japan. Journal of Science, Hiroshima University Series C3, 282 –342. Kim, I.-S., Kang, H.C., Lee, H.K., 1993. Palaeomagnetism of Early Cretaceous sedimentary rocks in Chingyo–Sachon area, southwestern Kyongsang Basin. Journal of Korean Institute of Mining Geology 26, 519– 539.in Korean with English Abstract. Kimura, T., Hayami, I., Yoshida, S., 1991. Geology of Japan, University of Tokyo Press, Tokyo, 287 pp.
Koch, P.L., 1998. Isotopic reconstruction of past continental environments. Annual Review of Earth and Planetary Sciences 26, 573– 613. Kusumi, H., 1960. On the occurrence of Cretaceous estherids in north Kyushu. Journal of Science, Hiroshima University Series C3, 15–24. Latorre, C., Quade, J., McIntosh, W.C., 1997. The expansion of C4 grasses and global climate change in the late Miocene: stable isotope evidence from the America. Earth and Planetary Science Letters 146, 83–96. Lee, Y.I., 1999. Stable isotopic composition of calcic paleosols of the Early Cretaceous Hasandong Formation, southeastern Korea. Palaeogeography, Palaeoclimatology, Palaeoecology 150, 123–133. Lee, Y.I., Hisada, K., 1997. Characteristics of alluvial deposits and paleosols of the Cretaceous Shimonoseki Subgroup in Yoshimi area, westernmost Honshu. Annual Review, Institute of Geoscience, University of Tsukuba 23, 29 –33. Lee, Y.I., Hisada, K., 1999. Stable isotopic composition of pedogenic carbonates of the Early Cretaceous Shimonoseki Subgroup, western Honshu, Japan. Palaeogeography, Palaeoclimatology, Palaeoecology 153, 127–138. Lerman, J.C., 1972. Soil and groundwater: carbon isotope composition. Proceedings of Eighth International Conference on Radiocarbon Dating, Lower Hutt, D93–D105. Mora, C., Driese, S.G., Seager, P.G., 1991. Carbon dioxide in the Paleozoic atmosphere: evidence from carbon-isotope compositions of pedogenic carbonate. Geology 19, 1017– 1020. Mora, C.I., Driese, S.G., Colarusso, L.A., 1996. Middle to late Paleozoic atmospheric CO2 levels from soil carbonate and organic matter. Science 271, 1105–1107. Morgan, M.E., Kingston, J.D., Marino, B.D., 1994. Carbon isotopic evidence for the emergence of C4 plants in the Neogene from Pakistan and Kenya. Nature 367, 162 –165. Paik, I.S., Lee, Y.I., 1998. Desiccation cracks in vertic palaeosols of the Cretaceous Hasandong Formation, Korea: genesis and palaeoenvironmental implications. Sedimentary Geology 119, 161–179. Quade, J., Cerling, T.E., 1995. Expansion of C4 grasses in the late Miocene of northern Pakistan: evidence from stable isotopes in paleosols. Palaeogeography, Palaeoclimatology, Palaeoecology 115, 91–116. Quade, J., Cerling, T.E., Bowman, J.R., 1989. Systematic variations in the carbon and oxygen isotopic composition of pedogenic carbonate along elevation transects in the southern Great Basin, USA. Geological Society of America Bulletin 101, 464 –475. Quade, J., Cater, J.M.L., Ojha, T.P., Adam, J., Harrison, T.M., 1995. Late Miocene environmental change in Nepal and the northern Indian subcontinent: stable isotopic evidence from paleosols. Geological Society of America Bulletin 107, 1381–1397. Sakai, T., Okada, H., 1997. Sedimentation and tectonics of the Cretaceous sedimentary basins of the axial and Kurosegawa tectonic zone in Kyushu, SW Japan. Cretaceous Environmental Change in East and South Asia (IGCP350)-Contributions from Japan. The Memoirs of the Geological Society of Japan 48, 7–28. Seo, S.J., 1985. Lower Cretaceous geology and paleontology (Charophyta) of central Kyongsang Basin, South Korea. Unpublished PhD Thesis, Kyungpook National University, (in Korean with English Abstract), 177 pp. Smith, B.N., Epstein, S., 1971. Two categories of 13C/12C ratios for higher plants. Plant Physiology 47, 380– 384.
Paleovegetation and paleoatmospheric P(CO2) levels during the Early Cretaceous: examples from the Hasandong Formation, Korea, and the Shimonoseki Subgroup, Japan Yong Il Lee* School of Earth and Environmental Sciences, Seoul National University, Seoul 151-747, South Korea Received 25 July 2000; revised 25 January 2002; accepted 21 April 2002
Abstract Stable carbon-isotope compositions of pedogenic carbonates occurring in two Lower Cretaceous non-marine deposits, the Hasandong Formation, Korea (Hauterivian/Barremian) and the Shimonoseki Subgroup, Japan (Aptian), provide a record of past pedogenic environments, and are used to infer paleovegetation and CO2 pressure P(CO2) of the Early Cretaceous atmosphere. The carbon isotopic compositions (2 5.6 to 26.7‰) of pedogenic carbonates from both strata suggest soils dominated by C3 type of vegetation. Atmospheric CO2 contributed generally less than 30% of the carbon isotopes to these pedogenic carbonates. The Early Cretaceous atmosphere is unlikely to have contained more than about 4500 ppm V by volume of CO2. High concentrations of carbon dioxide in the Early Cretaceous atmosphere are in good agreement with the modeled atmospheric P(CO2) estimation of Berner [American Journal of Science 294 (1994) 56 – 91]. The fact that paleo-P(CO2) levels during Shimonoseki time (1900 – 3200 ppm V) were lower than those of Hasandong time (2400 – 4500 ppm V) indicates that the paleo-P(CO2) levels in the atmosphere were lower than the Early Cretaceous high, which fits well with a trend of decreasing carbon dioxide levels in the paleoatmosphere during the Cretaceous. q 2002 Elsevier Science Ltd. All rights reserved. Keywords: Hasandong Formation; Shimonoseki Subgroup; Pedogenic carbonates; Carbon-isotope; Cretaceous
1. Introduction Stable isotope studies of pedogenic carbonate have been increasingly applied to ancient paleosols in order to study paleovegetation (Bocherans et al., 1994; Cerling et al., 1989, 1997; Koch, 1998; Latorre et al., 1997; Morgan et al., 1994; Quade and Cerling, 1995; Quade et al., 1995) and paleoclimates (Andrews et al., 1995; Ghosh et al., 1995; Mora et al., 1991, 1996; Ekart et al., 1999). Cerling (1991, 1992) provided a model for estimating ancient atmospheric P(CO2) by showing that the isotopic composition of pedogenic carbonate is directly related to soil CO2, which in turn depends on the concentration of CO2 in the atmosphere. The carbon isotopic composition of pedogenic carbonates is also sensitive to the type of vegetation (C3 versus C4 plants). This study provides the carbon-isotope geochemistry of pedogenic carbonates in two Lower Cretaceous calcareous paleosols within the Hasandong * Tel.: þ82-2-880-6736; fax: þ 82-2-871-3269. E-mail address: [email protected] (Y.I. Lee).
Formation, Korea and the Shimonoseki Subgroup, Japan (Fig. 1). Paleosols are ubiquitous in floodplain deposits of the Hasandong Formation and in the upper part of the fluvial fining-upward cycles within a mid- to distal-alluvial fans of the Shimonoseki Subgroup. Both strata are known to contain abundant pedogenic carbonates (Chang, 1975; Choi, 1985; Lee and Hisada, 1997), and Lee (1999) and Lee and Hisada (1999) studied their stable isotopic compositions. The objectives of this paper are to compare the carbon isotopic compositions of pedogenic carbonates from both strata and to discuss the estimates of partial pressures of atmospheric CO2 within the context of the estimated carbon dioxide concentrations during the Cretaceous.
2. Stratigraphy and depositional setting The Hasandong Formation is the middle stratigraphic unit of the Sindong Group, which is distributed along the western margin of the Cretaceous non-marine Gyeongsang Basin, Korea (Fig. 1). It is 550– 1400 m thick and consists of
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Fig. 1. Simplified geologic maps of (a) the Gyeongsang Basin, Korea and (b) the Kanmon Basin, Japan.
sandstones, reddish and gray silty shales, and minor conglomerates which were deposited in fluvial channels and on floodplains (Choi, 1985, 1986). The formation is underlain by the Nagdong Formation (alluvial to fluvial deposits) and is overlain by the Jinju Formation (lacustrine deposits). The geologic age of the Hasandong Formation has been generally inferred to be Hauterivian from charophytes in the underlying Nagdong Formation (Seo, 1985) and Barremian by Chang et al. (1997) (Fig. 2). Abundant fossils of vascular plants, bivalves, and some gastropods have been reported from mudstones of this formation. Most of them indicate an Early Cretaceous age and non-marine environments. The paleolatitude of the Korean Peninsula during the Cretaceous was similar to the present one (Kim et al., 1993). The Shimonoseki Subgroup is the upper clastic sequence of the Kanmon Group, which is distributed in northern Kyushu and westernmost Honshu, Japan (Fig. 1). The Shimonoseki Subgroup is about 2300 m thick, and rests disconformably on the low-lying Wakino Subgroup and
onlaps the older basement rocks. It is composed of conglomerate, sandstone, shale, tuff, tuff breccia and lavas of andesite, dacite and rhyolite. Most of its sediments are volcanogenic in origin. The age of the Shimonoseki Subgroup is dated as late Early Cretaceous (Aptian – Albian) (Kimura et al., 1991). Fossils are rare in general, but occurrences of a few freshwater bivalves (Nippononaia and Esterites ) have been reported (Hase, 1969; Kusumi, 1960). The Shimonoseki Subgroup is subdivided into three stratigraphic units: the Shiohama, Kitahikoshima and Sujigahama formations in decreasing age. In this report, pedogenic carbonates are from paleosols of the Shiohama Formation, mainly in the Yoshimi area, Yamaguchi Prefecture, western Honshu. Thus, the geologic age of the paleosol-bearing Shiohama Formation may correspond to the late Aptian. The studied section is about 200 m thick and is composed of several , 10 m thick conglomerate beds with intervening thick reddish mudrocks and thin sandstones. Sediments are interpreted to have been deposited in a mid- to distal-alluvial fan setting (Lee and Hisada, 1997).
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noseki Subgroup, respectively, are used for this study for comparison and their carbon isotopic compositions are shown in Table 1 and in Fig. 3. The carbon isotopic compositions of the Hasandong pedogenic carbonates range from 2 2.4 to 2 9.3‰ with an average of 2 5.6 ^ 1.7‰, and of the Shimonoseki pedogenic carbonates range from 2 5.4 to 2 7.7‰ with an average of 2 6.7 ^ 0.5‰. As shown in Fig. 3 the carbon isotopic compositions of the Shimonoseki carbonates are slightly more negative and are less scattered than those of the Hasandong carbonates.
5. Discussion
Fig. 2. Stratigraphic correlation between the Gyeongsang Basin, Korea and the Kanmon Basin, Japan (modified after Sakai and Okada (1997)).
3. Pedogenic carbonate Descriptions of pedogenic carbonates of these strata are given by Lee (1999) and Lee and Hisada (1999), and only a brief summary of their characteristics is given here. The Hasandong and Shimonoseki paleosols contain (1) poor stratification of carbonate nodule-bearing fines, (2) calcareous root traces and rhizoliths, (3) circumgranular and curved cracks, fitted peloids and calcite aureoles around detrital grains in calcareous nodules, (4) vertical profiles of two or more horizons with the calcic intervals present toward the base, (5) purple horizon colors, (6) beds of limeintraclast conglomerates, and (7) truncation of carbonate nodule- and lens-bearing horizons by the overlying channel deposits. Although each of the above descriptions is not conclusive, collectively they suggest that the studied carbonate nodules are of pedogenic origin. Stable isotopic measurements were performed on powdered samples collected with a dental drill, after the nodules and rhizocretions were sliced and polished to expose the fresh surface. Stable carbon isotopes were analyzed by a VG PRISM Series II Model at the Korea Basic Science Institute. The isotopic ratios of carbon are presented in standard-notation (‰) relative to PDB. Reproducibility of the analyses was ^ 0.1‰.
4. Carbon isotope composition Analyses of a total of eighteen and fifteen pedogenic carbonates from the Hasandong Formation and the Shimo-
Because its carbon is derived from soil CO2, the carbon isotopic composition of pedogenic carbonate is strongly correlated to that of soil organic matter and the overlying flora. Atmospheric CO2, which has a carbon isotopic composition less negative than that of plants, generally contributes to soil CO2 near the surface. The difference in carbon isotopic composition between coexisting soil organic matter and pedogenic carbonate is 14 – 16‰ depending on temperature. This systematic difference arises from equilibrium fractionation between carbon-isotope species and from gas diffusive effects (Cerling et al., 1989; Quade et al., 1989, 1995). The C3 and C4 plants have d 13C values of 2 27‰ (Ehleringer, 1989) and 2 13‰ (Smith and Epstein, 1971), respectively (Fig. 4). CAM plants have a range of d 13C from 2 10 to 2 20‰ (Lerman, 1972). However, they are usually insignificant in ecosystems except in some of the desert regions. In pre-industrial times, the average isotopic composition of C3 and C4 plants should have been about 2 26 and 2 12‰, respectively. However, the carbon isotopic composition of organic matter from C3-dominated modern soils and paleosols is generally about 2 24‰ (Cerling, 1992), which is used in this study as a representative value of C3-dominated vegetation. Such heavier isotopic values indicate that the C3 plants were under water stress and warm temperatures (Cerling, 1992), which is supported by the characteristics of the Hasandong and Shimonoseki paleosols (Paik and Lee, 1998; Lee and Hisada, 1997, 1999). The d 13C values of the Hasandong plant-CO2 range from 2 15.7 to 2 22.6‰ with an average of 2 18.9 ^ 1.8‰ and those of the Shimonoseki plant-CO2 from 2 18.7 to 2 21.0‰ with an average of 2 20.6 ^ 0.6‰ assuming soil carbonate in equilibrium with soil CO2 at 25 8C (Table 1). The d 13C values of estimated Hasandong and Shimonoseki plant-CO2 are at or closer to the heavy end of C3 plants (Fig. 4), which suggests that the vegetation of the Hasandong and Shimonoseki times was probably dominated by C3-type plants. However, they are heavier than the average d 13C of C3 plants which is about 2 24‰. Influence from sources with heavier carbon-isotopes needs to be considered in order to shift d 13C values of the Hasandong and Shimonoseki plant-CO2 toward the heavy end or heavier than C 3 plant range. Compared to
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Table 1 Carbon isotopic compositions of pedogenic carbonates and estimated plant CO2 of the Hasandong Formation and Shimonoseki Subgroup (after Lee (1999) and Lee and Hisada (1999)) Hasandong Formation
Shimonoseki Subgroup
Sample
d 13C (‰) carbonate
d 13C (‰) plant CO2
Sample
d 13C (‰) carbonate
d 13C (‰) plant CO2
NAM1 NAM2 NAM3 9-1 9-2 44-1 44-2 44-3 11-1 11-2 J05 337 M09 O07 O06 Bito Yusu-sept Yusu-13 Average
24.5 23.9 24.0 27.0 24.8 26.2 26.0 23.9 27.6 26.2 27.8 29.3 25.2 23.3 22.4 26.8 26.4 26.0 25.6 ^ 1.7
218.6 218.0 218.1 221.1 218.9 220.3 220.1 218.0 221.7 220.3 221.9 223.4 219.3 217.6 216.5 220.9 220.5 220.1 218.9 ^ 1.8
1-CR1 1-CR2 2-CR1 2-CR2 3-CR1 3-CR2 5-CR1 5-CR2 6-CR1 6-CR2 7-CR 8-CR 9-CR 10-CR1 10-CR2 Average
27.0 27.7 27.0 27.3 27.0 26.9 26.7 26.4 26.2 26.5 26.9 26.9 27.0 25.4 25.8 26.7 ^ 0.5
220.3 221.0 220.3 220.6 220.3 220.2 220.0 219.7 219.5 219.8 220.2 220.2 220.3 218.7 219.2 220.6 ^ 0.6
Shimonoseki pedogenic carbonates, Hasandong pedogenic carbonates would have been influenced slightly more by sources with heavier carbon isotopes. For possible sources with heavier carbon isotopes, C4 plants, atmospheric CO2, or a combination of both can be inferred. Although the existence of C4 plants in pre-Miocene time is still in dispute, the general consensus is that C4 plants evolved from C3 plants probably during the late Miocene at about 7– 8 Ma (Cerling et al., 1997; Morgan et al., 1994; Latorre et al., 1997; Quade and Cerling, 1995; Quade et al., 1995), suggesting that the influence of C4 plants is less likely. No
Fig. 3. d 13C versus d 18O stable isotope cross plot for Hasandong and Shimonoseki pedogenic carbonates.
desert-like conditions have been reported for the Cretaceous in Korea and Japan, and thus the influence of CAM plants on the formation of soil carbonates can be excluded. Accordingly, the heavier d 13C values could have resulted from contributions of atmospheric CO2, whose carbon isotopic composition was about 2 6.5‰ in pre-industrial time. The calculated contribution of atmospheric CO2 for the Hasandong Formation was about 29% and for the Shimonoseki Subgroup was about 23%. A slightly more atmospheric CO2 influence on the Hasandong carbonates can be accounted for by the shallower depth of pedogenic carbonate in its paleosols relative to the Shimonoseki paleosols. Alternatively, a high atmospheric CO2 concentration during Hasandong time might have allowed more mixing of atmospheric CO2 deeper in the soil profile. Cerling (1992) provided a diffusion-reaction model to estimate atmospheric P(CO2) using carbon-isotope ratios of pedogenic carbonates. Two extreme cases are calculated to
Fig. 4. Ranges for d 13C values of different vegetation types and Hasandong and Shimonoseki pedogenic carbonates. Inverted triangles are average values and a triangle below the C3 plant range represents d 13C of organic matter from C3-dominated modern soils (Cerling, 1992).
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Fig. 6. Estimated atmospheric P(CO2) levels during the Cretaceous. The solid curve represents the GEOCARB II model (Berner, 1994).
The low atmospheric estimates are probably due to the low porosity of lacustrine carbonates.
6. Conclusion
Fig. 5. Atmospheric P(CO2) inferred from d 13C of Hasandong (filled square) and Shimonoseki (dot) pedogenic carbonates by using the model of Cerling (1992). S(z ) represents the soil-respired component of soil CO2 [ ¼ PCO2(soil) 2 PCO2(atmosphere)].
estimate the range of the atmospheric P(CO2): warm (25 8C) with high productivity where soil-respired CO2 equals 10,000 ppm V and cool (15 8C) for low productivity where soil-respired CO2 equals 5000 ppm V. Using this model, the paleoatmospheric CO2 levels of Hasandong and Shimonoseki times are estimated to be 2400 – 4500 ppm V and 1700 –3200 ppm V, respectively (Fig. 5). Collectively, the Early Cretaceous atmosphere is unlikely to have contained more than about 4500 ppm V by volume of CO2. Several model and field-based studies were done for estimation of paleoatmospheric CO2 concentrations. The estimated atmospheric P(CO2) levels during the Cretaceous are shown in Fig. 6. The modeled values of paleoatmospheric P(CO2) generally decrease during the Cretaceous with decreasing age (Berner, 1994). As shown in Fig. 6, the general trend of all Cretaceous estimates nicely matches with the modeled trend of Berner (1994) and with a general climatic decline. However, estimates from the Cenomanian to Santonian are lacking and these data are in need of further study to confirm this trend. The values inferred from the Barremian pedogenic carbonates (Cameros Basin, Spain; Cerling, 1991) are rather low compared to predicted ones. This is because the carbon-isotope values were derived from lacustrine carbonates that were modified by pedogenesis.
Abundant pedogenic carbonate nodules are present in Lower Cretaceous non-marine deposits in Korea and Japan, the Hasandong Formation (Hauterivian/Barremian) and the Shimonoseki Subgroup (Aptian), respectively. These pedogenic carbonates are used to estimate the concentration of carbon dioxide in the Early Cretaceous atmosphere. The carbon isotopic compositions of pedogenic carbonates from both strata suggest soils dominated by C3 type of vegetation. The paleo-P(CO2) level in the atmosphere during the Early Cretaceous was unlikely more than about 4500 ppm V. The estimated high concentrations of carbon dioxide in the Early Cretaceous atmosphere are in good agreement with the modeled atmospheric P(CO2) estimation of Berner (1994). The finding that paleo-P(CO2) levels of the Shimonoseki time were lower than those of Hasandong time indicates that the paleo-P(CO2) levels in the atmosphere had dropped from the Early Cretaceous high, which fits well with a trend of decreasing carbon dioxide levels in the paleoatmosphere during the Cretaceous.
Acknowledgments This study was supported by the Korea Science and Engineering Foundation grant (2000-2-13100-003-5). I am grateful to H.S. Lim for drafting the figures. I thank the reviewers (G.J. Retallack, G.A. Ludvigson and editors C.C. Johnson, H. Hirano and K. Burke) for their helpful and constructive comments.
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References Andrews, J.E., Tandon, S.K., Dennis, P.F., 1995. Concentration of carbon dioxide in the Late Cretaceous atmosphere. Journal of Geological Society of London 152, 1–3. Berner, R.A., 1994. GEOCARB II: a revised model of atmospheric CO2 over Phanerozoic time. American Journal of Science 294, 56–91. Bocherans, H., Friis, E.M., Mariotti, A., Pedersen, K.R., 1994. Carbon isotopic abundances in Mesozoic and Cenozoic fossil plants: paleoecological implications. Lethaia 26, 347–358. Cerling, T.E., 1991. Carbon dioxide in the atmosphere: evidence from Cenozoic and Mesozoic paleosols. American Journal of Science 291, 377– 400. Cerling, T.E., 1992. Use of carbon isotopes in paleosols as an indicator of the P(CO2) of the paleoatmosphere. Global Biogeochemical Cycles 6, 307– 314. Cerling, T.E., Wang, Y., Bowman, J.R., 1989. Carbon isotopes in soils and paleosols as ecologic and paleoecologic indicators. Nature 341, 138– 139. Cerling, T.E., Quade, J., Eisenmann, V., Ehleringer, J.R., Harris, J.M., MacFadden, B.J., Leakey, M.G., 1997. Global vegetation change through the Miocene/Pliocene boundary. Nature 389, 153 –158. Chang, K.H., 1975. Cretaceous stratigraphy of southeastern Korea. Journal of Geological Society of Korea 11, 1–23. Chang, K.H., Park, S.-O., Kim, H.-S., 1997. Cretaceous stratigraphy and geologic history of medial Kyongsang Basin: tectonics and volcanism. Geoscience Journal 1, 2– 9. Choi, H.I., 1985. Sedimentology and its application for stratigraphic classifications of the Cretaceous Kyeongsang Basin. Journal of Geological Society of Korea 21, 26–37. Choi, H.I., 1986. Fluvial plain/lacustrine facies transition in the Cretaceous Sindong Group, south coast of Korea. Sedimentary Geology 48, 295– 320. Ehleringer, J.R., 1989. Carbon isotope ratios and physiological processes in arid land plants. In: Rundel, P.W., Ehleringer, J.R., Nagy, K.A. (Eds.), Applications of Stable Isotopic Ratios to Ecological Research, Springer, New York, pp. 41–54. Ekart, D.D., Cerling, T.E., Montan˜ez, I.P., Tabor, N.J., 1999. A 400 million year carbon isotope record of pedogenic carbonate: implications for paleoatmospheric carbon dioxide. American Journal of Science 299, 805– 827. Ghosh, P., Bhattacharya, S.K., Jani, R.A., 1995. Palaeoclimate and palaeovegetation in central India during the Upper Cretaceous based on stable isotope composition of the palaeosol carbonate. Palaeogeography, Palaeoclimatology, Palaeoecology 114, 285– 296. Hase, A., 1969. The late Mesozoic formations and their molluscan fossils in west Chugoku and north Kyushu, Japan. Journal of Science, Hiroshima University Series C3, 282 –342. Kim, I.-S., Kang, H.C., Lee, H.K., 1993. Palaeomagnetism of Early Cretaceous sedimentary rocks in Chingyo–Sachon area, southwestern Kyongsang Basin. Journal of Korean Institute of Mining Geology 26, 519– 539.in Korean with English Abstract. Kimura, T., Hayami, I., Yoshida, S., 1991. Geology of Japan, University of Tokyo Press, Tokyo, 287 pp.
Koch, P.L., 1998. Isotopic reconstruction of past continental environments. Annual Review of Earth and Planetary Sciences 26, 573– 613. Kusumi, H., 1960. On the occurrence of Cretaceous estherids in north Kyushu. Journal of Science, Hiroshima University Series C3, 15–24. Latorre, C., Quade, J., McIntosh, W.C., 1997. The expansion of C4 grasses and global climate change in the late Miocene: stable isotope evidence from the America. Earth and Planetary Science Letters 146, 83–96. Lee, Y.I., 1999. Stable isotopic composition of calcic paleosols of the Early Cretaceous Hasandong Formation, southeastern Korea. Palaeogeography, Palaeoclimatology, Palaeoecology 150, 123–133. Lee, Y.I., Hisada, K., 1997. Characteristics of alluvial deposits and paleosols of the Cretaceous Shimonoseki Subgroup in Yoshimi area, westernmost Honshu. Annual Review, Institute of Geoscience, University of Tsukuba 23, 29 –33. Lee, Y.I., Hisada, K., 1999. Stable isotopic composition of pedogenic carbonates of the Early Cretaceous Shimonoseki Subgroup, western Honshu, Japan. Palaeogeography, Palaeoclimatology, Palaeoecology 153, 127–138. Lerman, J.C., 1972. Soil and groundwater: carbon isotope composition. Proceedings of Eighth International Conference on Radiocarbon Dating, Lower Hutt, D93–D105. Mora, C., Driese, S.G., Seager, P.G., 1991. Carbon dioxide in the Paleozoic atmosphere: evidence from carbon-isotope compositions of pedogenic carbonate. Geology 19, 1017– 1020. Mora, C.I., Driese, S.G., Colarusso, L.A., 1996. Middle to late Paleozoic atmospheric CO2 levels from soil carbonate and organic matter. Science 271, 1105–1107. Morgan, M.E., Kingston, J.D., Marino, B.D., 1994. Carbon isotopic evidence for the emergence of C4 plants in the Neogene from Pakistan and Kenya. Nature 367, 162 –165. Paik, I.S., Lee, Y.I., 1998. Desiccation cracks in vertic palaeosols of the Cretaceous Hasandong Formation, Korea: genesis and palaeoenvironmental implications. Sedimentary Geology 119, 161–179. Quade, J., Cerling, T.E., 1995. Expansion of C4 grasses in the late Miocene of northern Pakistan: evidence from stable isotopes in paleosols. Palaeogeography, Palaeoclimatology, Palaeoecology 115, 91–116. Quade, J., Cerling, T.E., Bowman, J.R., 1989. Systematic variations in the carbon and oxygen isotopic composition of pedogenic carbonate along elevation transects in the southern Great Basin, USA. Geological Society of America Bulletin 101, 464 –475. Quade, J., Cater, J.M.L., Ojha, T.P., Adam, J., Harrison, T.M., 1995. Late Miocene environmental change in Nepal and the northern Indian subcontinent: stable isotopic evidence from paleosols. Geological Society of America Bulletin 107, 1381–1397. Sakai, T., Okada, H., 1997. Sedimentation and tectonics of the Cretaceous sedimentary basins of the axial and Kurosegawa tectonic zone in Kyushu, SW Japan. Cretaceous Environmental Change in East and South Asia (IGCP350)-Contributions from Japan. The Memoirs of the Geological Society of Japan 48, 7–28. Seo, S.J., 1985. Lower Cretaceous geology and paleontology (Charophyta) of central Kyongsang Basin, South Korea. Unpublished PhD Thesis, Kyungpook National University, (in Korean with English Abstract), 177 pp. Smith, B.N., Epstein, S., 1971. Two categories of 13C/12C ratios for higher plants. Plant Physiology 47, 380– 384.