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Midlatitude Temperature Variations in the Oligocene to Early Miocene
Author(s) -
Guitián José,
Phelps Samuel,
Polissar Pratigya J.,
Ausín Blanca,
Eglinton Timothy I.,
Stoll Heather M.
Publication year - 2019
Publication title -
paleoceanography and paleoclimatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.927
H-Index - 127
eISSN - 2572-4525
pISSN - 2572-4517
DOI - 10.1029/2019pa003638
Subject(s) - geology , middle latitudes , alkenone , sea surface temperature , oceanography , climatology , sea ice , context (archaeology) , benthic zone , paleoceanography , paleontology
Antarctic ice sheet margin extent and the sensitivity of benthic δ 18 O to orbital forcing have varied on million‐year timescales during the Oligocene to Early Miocene. However, few sea surface temperature (SST) records for this time interval exist to evaluate links between polar processes and mean temperature outside polar regions. Here, we present a new record of SST for the time interval 30 to 17 Ma derived from the long‐chain alkenone unsaturation ratio ( U 37 k ′ ) at Integrated Ocean Drilling Program Site 1406A in the midlatitude North Atlantic. Results confirm that warm temperatures from 24°C to over 30°C prevailed in midlatitudes in this time and suggest a transition from colder early‐middle Oligocene to warmer average conditions after 24.5 Ma. The global significance of this transition is highlighted by the coincidence with changes in the dominance from marine‐ to terrestrial‐terminating ice sheets in the Ross Sea around Antarctica. The longest continuous section of the record (20.6 to 26.6 Ma) contains multiple 2 million‐year cycles in SST, potentially paced by long obliquity modulation. Complex and temporally varying relationships are observed between North Atlantic SST and benthic δ 18 O in paired samples; significant covariation is only observed around the Oligocene‐Miocene transition, coincident with a lower average marine ice extent. These North Atlantic U 37 k ′temperature records provide a new context in which to examine the stability of climate and the Antarctic ice sheet during the Oligocene and early Miocene.