Warm High‐Elevation Mid‐Latitudes During the Miocene Climatic Optimum: Paleosol Clumped Isotope Temperatures From the Northern Rocky Mountains, USA. Issue 6 (23rd June 2021)

• Record Type: Journal Article
• Authors: Methner, K.; Mulch, A.; Fiebig, J.; Krsnik, E.; Löffler, N.; Bajnai, D.; Chamberlain, C. P.
• Is Part Of: Paleoceanography and paleoclimatology. Volume 36:Issue 6(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-06-23
• Subjects: Miocene Climatic Optimum -- clumped isotope temperatures -- Northern Rocky Mountains -- terrestrial climate -- marine‐terrestrial coupling; Paleoceanography -- Periodicals; Paleoclimatology -- Periodicals; 551.46
• DOI: 10.1029/2020PA003991
• Languages: English
• ISSNs: 2572-4517

Abstract

Abstract: Interrupting a long‐term Cenozoic cooling trend, the Miocene Climatic Optimum (MCO; ca. 17–15 Ma) represents a time interval characterized globally by warmer than present temperatures, lower ice volume, and elevated pCO2 levels. Establishing quantitative Neogene temperature estimates is an important element in the effort to explore the long‐term changes in the carbon cycle and associated climate feedbacks, yet terrestrial temperature records are still sparse. Here, we present a clumped isotope (Δ47 ) temperature record of the MCO from intermontane basins in the Northern Rocky Mountain (NRM) region. Arikareean (22.7–21.5 Ma) to Barstovian (16.9–14.7 Ma) paleosol carbonates from the Hepburn's Mesa Formation (Montana), supplemented with data from fossil localities in western Idaho. These records yield Δ47 ‐temperatures ranging from 17°C to 24°C, which are rather warm given the high elevation sites and are further relatively stable (mean of 21 ± 2°C) leading into and during the MCO until ca. 14.7 Ma. At ca. 14.7 Ma, we observe low Δ47 ‐temperatures (8°C–10°C) concomitantly with elevated Δ47 ‐temperatures (ca. 22°C). In line with recently suggested climate stability in the NRM region leading into the MCO, our Δ47 ‐temperature record, combined with carbon isotope (δ 13 C) and reconstructed soil water oxygen isotope (δ 18 Osw ) values, indicates rather stable climate and environmental conditions throughout the MCO. Combining available records from inland sites in the western United States (NRM, Mojave region) points to prevailing stable continental climates even during the MCO. Key Points: First paleosol carbonate clumped isotope (Δ47 ) temperature record of the Miocene Climatic Optimum in the Northern Rocky Mountain region Overall constant Δ47 ‐temperatures (21 ± 2°C) during the Miocene Climatic Optimum until 14.7 Ma Constant temperatures suggest dominant continentality and suppressed westerlies