Quasi-static Eocene-Oligocene climate in Patagonia promotes slow faunal evolution and mid-Cenozoic global cooling

New local/regional climatic data were compared with floral and faunal records from central Patagonia to investigate how faunas evolve in the context of local and global climates. Oxygen isotope compositions of mammal fossils between c. 43 and 21 Ma suggest a nearly constant mean annual temperature o...

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Autores principales: Kohn, Matthew J., Strömberg, Caroline A. E., Madden, Richard H., Dunn, Regan E., Evans, Samantha L., Palacios, Alma, Carlini, Alfredo Armando
Formato: Articulo
Lenguaje:Inglés
Publicado: 2015
Materias:
Ciencias Naturales
Hypsodonty
Notoungulate
Atmospheric CO2
Stable isotopes
Precipitation
Dust
Acceso en línea:http://sedici.unlp.edu.ar/handle/10915/133449
Aporte de:
SEDICI (UNLP) de Universidad Nacional de La Plata
id I19-R120-10915-133449
record_format dspace
institution Universidad Nacional de La Plata
institution_str I-19
repository_str R-120
collection SEDICI (UNLP)
language Inglés
topic Ciencias Naturales
Hypsodonty
Notoungulate
Atmospheric CO2
Stable isotopes
Precipitation
Dust
spellingShingle Ciencias Naturales
Hypsodonty
Notoungulate
Atmospheric CO2
Stable isotopes
Precipitation
Dust
Kohn, Matthew J.
Strömberg, Caroline A. E.
Madden, Richard H.
Dunn, Regan E.
Evans, Samantha L.
Palacios, Alma
Carlini, Alfredo Armando
Quasi-static Eocene-Oligocene climate in Patagonia promotes slow faunal evolution and mid-Cenozoic global cooling
topic_facet Ciencias Naturales
Hypsodonty
Notoungulate
Atmospheric CO2
Stable isotopes
Precipitation
Dust
description New local/regional climatic data were compared with floral and faunal records from central Patagonia to investigate how faunas evolve in the context of local and global climates. Oxygen isotope compositions of mammal fossils between c. 43 and 21 Ma suggest a nearly constant mean annual temperature of 16 ± 3 °C, consistent with leaf physiognomic and sea surface studies that imply temperatures of 16–18 °C. Carbon isotopes in tooth enamel track atmospheric δ 13 C, but with a positive deviation at 27.2 Ma, and a strong negative deviation at 21 Ma. Combined with paleosol characteristics and reconstructed Leaf Area Indices (rLAIs), these trends suggest aridification from 45 Ma (c. 1200 mm/yr) to 43 Ma (c. 450 mm/yr), quasi-constant MAP until at least 31 Ma, and an increase to ~ 800 mm/yr by 21 Ma. Comparable MAP through most of the sequence is consistent with relatively constant floral compositions, rLAI, and leaf physiognomy. Abundance of palms reflects relatively dry-adapted lineages and greater drought tolerance under higher p CO2 . Pedogenic carbonate isotopes imply low p CO2  = 430 ± 300 ppmv at the initiation of the Eocene–Oligocene climatic transition. Arid conditions in Patagonia during the late Eocene through Oligocene provided dust to the Southern Ocean, enhancing productivity of silicifiers, drawdown of atmospheric CO 2 , and protracted global cooling. As the Antarctic Circumpolar Current formed and Earth cooled, wind speeds increased across Patagonia, providing more dust in a positive climate feedback. High tooth crowns (hypsodonty) and ever-growing teeth (hypselodonty) in notoungulates evolved slowly and progressively over 20 Ma after initiation of relatively dry environments through natural selection in response to dust ingestion. A Ratchet evolutionary model may explain protracted evolution of hypsodonty, in which small variations in climate or dust delivery in an otherwise static environment drive small morphological shifts that accumulate slowly over geologic time.
format Articulo
Articulo
author Kohn, Matthew J.
Strömberg, Caroline A. E.
Madden, Richard H.
Dunn, Regan E.
Evans, Samantha L.
Palacios, Alma
Carlini, Alfredo Armando
author_facet Kohn, Matthew J.
Strömberg, Caroline A. E.
Madden, Richard H.
Dunn, Regan E.
Evans, Samantha L.
Palacios, Alma
Carlini, Alfredo Armando
author_sort Kohn, Matthew J.
title Quasi-static Eocene-Oligocene climate in Patagonia promotes slow faunal evolution and mid-Cenozoic global cooling
title_short Quasi-static Eocene-Oligocene climate in Patagonia promotes slow faunal evolution and mid-Cenozoic global cooling
title_full Quasi-static Eocene-Oligocene climate in Patagonia promotes slow faunal evolution and mid-Cenozoic global cooling
title_fullStr Quasi-static Eocene-Oligocene climate in Patagonia promotes slow faunal evolution and mid-Cenozoic global cooling
title_full_unstemmed Quasi-static Eocene-Oligocene climate in Patagonia promotes slow faunal evolution and mid-Cenozoic global cooling
title_sort quasi-static eocene-oligocene climate in patagonia promotes slow faunal evolution and mid-cenozoic global cooling
publishDate 2015
url http://sedici.unlp.edu.ar/handle/10915/133449
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