کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
6427294 | 1634706 | 2016 | 8 صفحه PDF | دانلود رایگان |
- We present δ18O and Î47 temperature data from western North American paleosols.
- Î47 temperatures of soil carbonates delineate a +9/â11â°C temperature excursion.
- Large and rapid shifts in δ18O and pedogenic CaCO3 contents parallel Î47 changes.
- U/Pb geochronology of paleosol carbonates places continental warming at MECO.
- MECO has a profound impact on atmospheric circulation and rainfall patterns.
Eocene hyperthermals are among the most enigmatic phenomena of Cenozoic climate dynamics. These hyperthermals represent temperature extremes superimposed on an already warm Eocene climate and dramatically affected the marine and terrestrial biosphere, yet our knowledge of temperature and rainfall in continental interiors is still rather limited. We present stable isotope (δ18O) and clumped isotope temperature (Î47) records from a middle Eocene (41 to 40 Ma) high-elevation mammal fossil locality in the North American continental interior (Montana, USA). Î47 paleotemperatures of soil carbonates delineate a rapid +9/â11â°C temperature excursion in the paleosol record. Î47 temperatures progressively increase from 23â°C ± 3â°C to peak temperatures of 32â°C ± 3â°C and subsequently drop by 11â°C. This hyperthermal event in the middle Eocene is accompanied by low δ18O values and reduced pedogenic carbonate concentrations in paleosols. Based on laser ablation U/Pb geochronology of paleosol carbonates in combination with magnetostratigraphy, biostratigraphy, stable isotope, and Î47 evidence, we suggest that this pronounced warming event reflects the Middle Eocene Climatic Optimum (MECO) in western North America. The terrestrial expression of northern hemisphere MECO in western North America appears to be characterized by warmer and wetter (sub-humid) conditions, compared to the post-MECO phase. Large and rapid shifts in δ18O values of precipitation and pedogenic CaCO3 contents parallel temperature changes, indicating the profound impact of the MECO on atmospheric circulation and rainfall patterns in the western North American continental interior during this transient warming event.
Journal: Earth and Planetary Science Letters - Volume 450, 15 September 2016, Pages 132-139