Late Oligocene atmospheric carbon dioxide concentrations reconstructed from fossil leaves using stomatal index


  • Tekie Tesfamichael Addis Ababa University, College of Natural and Computational Sciences, Addis Ababa 1176, Ethiopia



Stomatal index, Fossil leaves, Ethiopia, atmospheric CO2, Late Oligocene


Ancient atmospheric CO2 can be reconstructed using various climate proxies; stomata from fossil leaves are one of the climate proxies that provide critical information about past climatic conditions of the Earth. Exceptionally well–preserved fossil leaves found in overbank deposits in Chilga of Northwest Ethiopia were used to estimate late Oligocene atmospheric CO2 values using stomatal index. The age of the fossils, 206Pb/238U: 27.23 ± 0.03 Ma, was determined from zircons in an ash deposit comprising the matrix deposited contemporaneously with the fossil leaves. Stomatal indices were calculated from both the fossil leaves and nearest living relatives of the fossils. Corresponding atmospheric CO2 values for the nearest living relatives of the fossils were assigned from historical records from the Mauna Loa Observatory. This produces a calibrating curve that shows variation of atmospheric CO2 over time, and late Oligocene atmospheric CO2 values were quantified from the calibrating curve. The quantified late Oligocene atmospheric CO2 values are about 343 ± 11 ppm which show a 12 % decrease when they are quantified using a leaf gas exchange method. This is consistent with the idea that stomatal–index method underestimates CO2 values compared to the leaf gas exchange method. The late Oligocene was colder than both its preceding Eocene and its following Miocene epochs, and the results are incongruent with the cold Oligocene period. These results for this particular geologic time provide opportunity to examine how plants responded to climate changes in the past and have important implications for the study of current and future climate changes.


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Ayalew D, Barbey P, Marty B, Reisberg L, Yirgu G & Pik R 2002. Source, genesis, and timing of giant ignimbrite deposits associated with Ethiopian continental flood basalts. Geochimica et Cosmochimica Acta 66: 1429–1448. DOI:

Berner RA 2006. GEOCARBSULF: a combined model for Phanerozoic atmospheric O2 and CO2. Geochimica et Cosmochimica Acta 70: 5653–5664. DOI:

Berner RA & Kothavala Z 2001. GEOCARB III: a revised model of atmospheric CO2 over Phanerozoic time. American Journal of Science 301: 182–204. DOI:

Cotton LJ & Pearson PN 2011. Extinction of larger benthic foraminifera at the Eocene/Oligocene boundary. Palaeogeography, Palaeoclimatology, Palaeoecology 311: 281–296. DOI:

Coulie E, Quidelleur X, Gillot PY, Courtillot V, Lefèvre JC & Chiesa S 2003. Comparative K–Ar and Ar/Ar dating of Ethiopian and Yemenite Oligocene volcanism: implications for timing and duration of the Ethiopian traps. Earth and Planetary Science Letters 206: 477–492. DOI:

Escarguel G, Legendre S & Sigé B 2008. Unearthing deep–time biodiversity changes: The Palaeogene mammalian metacommunity of the Quercy and Limagne area (Massif Central, France). Comptes Rendus Geoscience 340: 602–614. DOI:

Franks PJ, Royer DL, Beerling DJ, Van de Water PK, Cantrill DJ, Barbour MM & Berry JA 2014. New constraints on atmospheric CO2 concentration for the Phanerozoic. Geophysical Research Letters 41: 4685–4694. DOI:

Grein M, Oehm Ch, Konrad W, Utescher T, Kunzmann L & Roth–Nebelsick A 2013. Atmospheric CO2 from the late Oligocene to early Miocene based on photosynthesis data and fossil leaf characteristics. Palaeogeography, Palaeoclimatology, Palaeoecology 374: 41–51. DOI:

Hansen J, Sato M, Kharecha P, Beerling D, Berner R, Masson–Delmotte V, Pagani M, Raymo M, Royer DL & Zachos JC 2008. Target Atmospheric CO2: Where Should Humanity Aim?. The Open Atmospheric Science Journal 2: 217–231. DOI:

Haworth M, Heath J & McElwain JC 2010. Differences in the response sensitivity of stomatal index to atmospheric CO2 among four genera of Cupressaceae conifers. Annals of Botany 105: 411–418. DOI:

Hodel F, Grespan R, Rafélis M, Dera G, Lezin C, Nardin E, Rouby D, Aretz M, Steinnman M, Buatier M, Lacan F, Jeandel C & Chavagnac C 2021. Drake Passage gateway opening and Antarctic Circumpolar Current onset 31 Ma ago: The message of foraminifera and reconsideration of the Neodymium isotope record. Chemical Geology 570: 120171. DOI:

Houben AJ, Mourik CA, Montanari A, Coccioni R & Brinkhuis H 2012. The Eocene–Oligocene transition: Changes in sea level, temperature or both? Palaeogeography, Palaeoclimatology, Palaeoecology 335–336: 75–83. DOI:

Hutchinson DK, Coxall HK, Lunt DJ, Steinthorsdottir M, Boer AM, Baatsen M, Heydt A, Huber M, Kennedy–Asser AT, Kunzmann L, Ladant J, Lear CH, Moraweck K, Pearson PN, Piga E, Pound MJ, Salzmann U, Scher HD, Sijp WP, Śliwińska KK, Wilson PA & Zhang Z 2020. The Eocene–Oligocene transition: a review of marine and terrestrial proxy data, models and model–data comparisons. Climate of the Past 68: 1–71. DOI:

Kappelman J, Rasmussen DT, Sanders WJ, Feseha M, Bown Th, Copeland P, Crabaugh J, Fleagle J, Glantz M, Gordon A, Jacobs B, Maga M, Muldoon K, Pan A, Pyne L, Richmond B, Ryan T, Seiffert ER, Sen S, Todd L, Wiemann MC & Winkler A 2003. Oligocene mammals from Ethiopia and faunal exchange between Afro–Arabia and Eurasia. Nature 426: 549–552. DOI:

Kieffer B, Arndt N, Lapierre H, Bastien F, Bosch D, Pecher A, Yirgu G, Ayalew D, Weis D, Jerram DA, Keller F & Meugniot C 2004. Flood and shield basalts from Ethiopia: magmas from the African superswell. Journal of Petrology 45: 793–834. DOI:

Konrad W, Royer DL, Franks PJ & Roth–Nebelsick A 2021. Quantitative critique of leaf–based paleo–CO2 proxies: Consequences for their reliability and applicability. Geological Journal 56: 886–902. DOI:

Kouwenberg LR, McElwain JC, Kürschner WM, Wagner F, Beerling DJ, Mayle FE & Visscher H 2003. Stomatal frequency adjustment of four conifer species to historical changes in atmospheric CO2. American Journal of Botany 90: 610–619. DOI:

Liu S, Feng Z, Lin H, Liu P, Liang M, Qing X, Xiong H, Qiu Sh, Li J, Jiang K, Hong H & Fang Sh 2021. Changes of atmospheric CO2 in the Tibetan Plateau from 1994 to 2019. JGR Atmospheres 126: e2021JD035299. DOI:

McElwain JC & Haworth DM 2009. The stomatal–CO2 proxy: limitations and advances. Geochimica et Cosmochimica Acta 73: A856.

Montañez IP & Poulsen CJ 2013. The late Paleozoic ice age: An evolving paradigm. Annual Review of Earth and Planetary Sciences 41: 629–656. DOI:

O’Brien ChL, Huber M, Thomas E, Pagani M, Super JR, Elder LE & Hull PM 2020. The enigma of Oligocene climate and global surface temperature evolution. PNAS 117: 25302–25309. DOI:

Pan AD, Jacobs BF & Herendeen PS 2010. Detarieae sensu lato (Fabaceae) from the Late Oligocene (27.23 Ma) Guang River flora of north–western Ethiopia. Botanical Journal of the Linnean Society 163: 44–54. DOI:

Pekar SF, DeConto RM & Harwood DM 2006. Resolving a late Oligocene conundrum: Deep–sea warming and Antarctic glaciation. Palaeogeography, Palaeoclimatology, Palaeoecology 231: 29–40. DOI:

Poole I, Weyers JB, Lawson T & Raven JA 1996. Variations in stomatal density and index: implications for palaeoclimatic reconstructions. Plant, Cell and Environment 19: 705–712. DOI:

Rasband WS 2016. ImageJ, U. S. National Institutes of Health, Bethesda, Maryland, USA:

Roth–Nebelsick A 2005. Reconstructing atmospheric carbon dioxide with stomata: possibilities and limitations of a botanical pCO2–sensor. Trees 19: 251–265. DOI:

Royer DL 2001. Stomatal density and stomatal index as indicators of palaeoatmospheric CO2 concentration. Review of Palaeobotany and Palynology 114: 1–28. DOI:

Sen S 2013. Dispersal of African mammals in Eurasia during the Cenozoic: Ways and whys. Geobios 46: 159–172. DOI:

Shockey BJ & Anaya F 2011. Grazing in a New Late Oligocene Mylodontid Sloth and a Mylodontid Radiation as a Component of the Eocene–Oligocene Faunal Turnover and the Early Spread of Grasslands/Savannas in South America. Journal of Mammalian Evolution 18: 101–115. DOI:

Steinthorsdottir M, Jardine PE, Lomax BH & Sallstedt T 2022. Key traits of living fossil Ginkgo biloba are highly variable but not influenced by climate–Implications for palaeo–pCO2 reconstructions and climate sensitivity. Global and Planetary Change 211: 103786. DOI:

Steinthorsdottir M & Vajda V 2015. Early Jurassic (late Pliensbachian) CO2 concentrations based on stomatal analysis of fossil conifer leaves from eastern Australia. Gondwana Research 27: 932–939. DOI:

Sun J, Sheykh M, Ahmadi N, Cao M, Zhang Z, Tian Sh, Sha J, Jian Z, Windley BF & Talebian, M 2021. Permanent closure of the Tethyan Seaway in the northwestern Iranian Plateau driven by cyclic sea–level fluctuations in the late Middle Miocene. Palaeogeography, Palaeoclimatology, Palaeoecology 564: 110172. DOI:

Tesfamichael T, Jacobs B, Tabor N, Michel L, Currano E, Feseha M, Barclay R, Kappelman J & Schmitz M 2017. Settling the issue of “decoupling” between atmospheric carbon dioxide and global temperature: [CO2]atm reconstructions across the warming Paleogene–Neogene divide. Geology 45: 999–1002. DOI:

Utescher T, Erdei B, François L, Henrot A, Mosbrugger V & Popova S 2020. Oligocene vegetation of Europe and western Asia–Diversity change and continental patterns reflected by plant functional types. Geological Journal 56: 628–649. DOI:

Villa G, Fioroni C, Pea L, Bohaty S & Persico D 2008. Middle Eocene–late Oligocene climate variability: Calcareous nannofossil response at Kerguelen Plateau, Site 748. Marine Micropaleontology 69: 173–192. DOI:

Vries D, Heritage S, Borths MR, Sallam HM & Seiffert ER 2021. Communications Biology 4: 1172.

Wang T, Li G, Aitchison JC & Sheng J 2020. Eocene ostracods from southern Tibet: Implications for the disappearance of Neo–Tethys. Palaeogeography, Palaeoclimatology, Palaeoecology 539: 109488. DOI:

Zachos JC, Dickens GR & Zeebe RE 2008. An early Cenozoic perspective on greenhouse warming and carbon–cycle dynamics. Nature 451: 279–283 DOI:




How to Cite

Tesfamichael, T. (2023). Late Oligocene atmospheric carbon dioxide concentrations reconstructed from fossil leaves using stomatal index. Journal of Palaeosciences, 72(2), 119–126.



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