TY - JOUR
T1 - Patagonian Aridification at the Onset of the Mid‐Miocene Climatic Optimum
AU - Trayler, Robin B.
AU - Kohn, Matthew J.
AU - Bargo, M. Susana
AU - Cuitiño, José I.
AU - Kay, Richard F.
AU - Strömberg, Caroline A.E.
AU - Vizcaíno, Sergio F.
N1 - Publisher Copyright:
©2020. American Geophysical Union. All Rights Reserved.
PY - 2020/9
Y1 - 2020/9
N2 - Fossil-rich sediments of the Santa Cruz Formation, Patagonia, Argentina, span the initiation of the Miocene Climatic Optimum (MCO), the most recent period of warm and wet conditions in the Cenozoic. These conditions drove the expansion of tropical and subtropical ecosystems to much higher latitudes, with the fossiliferous Santa Cruz Formation recording one of the southernmost examples. We collected new carbon and oxygen isotope compositions of herbivore tooth enamel from fossils ~17.4 to 16.4 Ma in age to investigate ecological and climatic changes across the initiation of the MCO. Enamel δ13C values are consistent with a C3-dominated ecosystem with moderate precipitation and a mix of wooded and more open areas. Serially sampled teeth reveal little zoning in δ13C and δ18O values, suggesting little seasonal variation in water and plant isotope compositions or seasonal changes in diet. Carbon isotope-based estimates of mean annual precipitation (MAP) are consistent with aridification, with MAP decreasing from ~1,000 ± 235 mm/yr at 17.4 Ma to ~525 ± 105 mm/yr at the start of the climatic optimum (~16.9 Ma). This decrease corresponds to increasing global temperatures, as indicated by marine proxy records, and was followed by a rebound to ~840 ± 270 mm/yr by ~16.4 Ma. In comparison to a modern mean annual temperature (MAT) in the region of ~8°C, oxygen isotopes indicate high MAT (at least 20°C) at the onset of the MCO at 16.9 Ma and a significant increase in MAT to ~25°C by 16.4 Ma.
AB - Fossil-rich sediments of the Santa Cruz Formation, Patagonia, Argentina, span the initiation of the Miocene Climatic Optimum (MCO), the most recent period of warm and wet conditions in the Cenozoic. These conditions drove the expansion of tropical and subtropical ecosystems to much higher latitudes, with the fossiliferous Santa Cruz Formation recording one of the southernmost examples. We collected new carbon and oxygen isotope compositions of herbivore tooth enamel from fossils ~17.4 to 16.4 Ma in age to investigate ecological and climatic changes across the initiation of the MCO. Enamel δ13C values are consistent with a C3-dominated ecosystem with moderate precipitation and a mix of wooded and more open areas. Serially sampled teeth reveal little zoning in δ13C and δ18O values, suggesting little seasonal variation in water and plant isotope compositions or seasonal changes in diet. Carbon isotope-based estimates of mean annual precipitation (MAP) are consistent with aridification, with MAP decreasing from ~1,000 ± 235 mm/yr at 17.4 Ma to ~525 ± 105 mm/yr at the start of the climatic optimum (~16.9 Ma). This decrease corresponds to increasing global temperatures, as indicated by marine proxy records, and was followed by a rebound to ~840 ± 270 mm/yr by ~16.4 Ma. In comparison to a modern mean annual temperature (MAT) in the region of ~8°C, oxygen isotopes indicate high MAT (at least 20°C) at the onset of the MCO at 16.9 Ma and a significant increase in MAT to ~25°C by 16.4 Ma.
KW - MMCO
KW - Miocene
KW - Santa Cruz Formation
KW - South America
KW - precipitation
KW - temperature
UR - http://www.scopus.com/inward/record.url?scp=85091466292&partnerID=8YFLogxK
UR - https://scholarworks.boisestate.edu/geo_facpubs/538
U2 - 10.1029/2020PA003956
DO - 10.1029/2020PA003956
M3 - Article
SN - 2572-4517
VL - 35
JO - Paleoceanography and Paleoclimatology
JF - Paleoceanography and Paleoclimatology
IS - 9
M1 - e2020PA003956
ER -