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>Middle Miocene ocean‐climate transition: High‐resolution oxygen and carbon isotopic records from Deep Sea Drilling Project Site 588A, southwest Pacific
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Middle Miocene ocean‐climate transition: High‐resolution oxygen and carbon isotopic records from Deep Sea Drilling Project Site 588A, southwest Pacific
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机译：Middle Miocene ocean‐climate transition: High‐resolution oxygen and carbon isotopic records from Deep Sea Drilling Project Site 588A, southwest Pacific
High‐resolution stable isotopic records are presented for the epi‐benthic foraminiferCibicidoides, the inferred shallow‐dwelling planktonicGlobigerinoides quadrilobatus, and the inferred deep‐dwelling planktonicGloboquadrina dehiscensfrom the middle Miocene (∼16–12 Ma) of Deep Sea Drilling Project site 588A, Lord Howe Rise, southwest Pacific. High‐resolution, multiple species oxygen and carbon isotopic data define the timing and character of the well‐known middle Miocene climatic‐oceanographic transition with a resolution comparable to Quaternary records. The benthic foraminiferal δ18O record is marked by several large fluctuations from ∼16 to 14.8 Ma, followed by a series of rapid (<50 kyr) δ18O increases that suggest a new state of the ocean‐climate system after 14.8 Ma. The total middle Miocene benthic oxygen isotopic increase of 1.2‰ is largely incorporated in two steps, an increase of 0.8‰ from 14.5 to 14.0 Ma and a second increase of 0.7‰ from 13.45 to 12.45 Ma. Each step is comprised of a series of marked δ18O increases, indicative of rapid East Antarctic ice sheet growth and contemporaneous deepwater cooling. A strong covariance of 0.7‰ between the benthic and deep‐dwelling planktonic species from 14.5 to 14.0 Ma (including a rapid increase from 14.1 to 14.05 Ma) suggests a 0.7‰ increase in the δ18O composition of seawater (δ18Osw) because of East Antarctic ice sheet growth. Comparison of the δ18O record ofGs. quadrilobatussuggests that surface waters warmed at this site by ∼3°C from 14.1 to 13.6 Ma. Carbon isotopic time series for each species generally covary throughout the early to middle Miocene interval (∼16–12 Ma), confirming that δ13C variations in this interval largely represent reservoir changes. High‐resolution δ13C data allow improved resolution of the latter five of six δ13C maxima within the well‐known early to middle Miocene carbon isotopic excursion (the Monterey Carbon Isotopic Excursion from 17.0 to 13.5 Ma). This is useful for global correlation. The last of these maxima ends with a 1‰ decrease centered from 13.9 to 13.7 Ma, ∼300 kyr after the δ18O increase considered to reflect East Antarctic ice growth. Covariance between benthic δ18O and δ13C from ∼16 to 13.8 Ma suggests a sensitive relation between global carbon cycling and the ocean‐climate system prior to 13.8 Ma. Episodic increases in organic carbon burial may have contributed to deep‐sea benthic δ13C maxima and synchronous global cooling. The positive relationship ended at ∼13.8 Ma, indicative of changing relations between global carbon cycling and the ocean‐climate system brought on by the increased stability of the E
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