Stable isotopes measured on Miocene benthic foraminifera from ODP sites 202-1237 and 184-1146

One of the most enigmatic features of Cenozoic long-term climate evolution is the long-lasting positive carbon-isotope excursion or “Monterey Excursion”, which started during a period of global warmth after 16.9 Ma and ended at not, vert, similar 13.5 Ma, approximately 400 kyr after major expansion of the Antarctic ice-sheet. We present high-resolution (1-9 kyr) astronomically-tuned climate proxy records in two complete sedimentary successions from the northwestern and southeastern Pacific (ODP Sites 1146 and 1237), which shed new light on the middle Miocene carbon-isotope excursion and associated climatic transition over the interval 17.1-12.7 Ma. We recognize three distinct climate phases with different imprints of orbital variations into the climatic signals (1146 and 1237 d18O, d13C; 1237 XRF Fe, fraction > 63 µm): (1) climate optimum prior to 14.7 Ma characterized by minimum ice volume and prominent 100 and 400 kyr variability, (2) long-term cooling from 14.7 to 13.9 Ma, principally driven by obliquity and culminating with rapid cryosphere expansion and global cooling at the onset of the last and most pronounced d13C increase, (3) “Icehouse” mode after 13.9 Ma with distinct 100 kyr variability and improved ventilation of the deep Pacific. The “Monterey” carbon-isotope excursion (16.9-13.5 Ma) consists overall of nine 400 kyr cycles, which show high coherence with the long eccentricity period. Superposed on these low-frequency oscillations are high-frequency variations (100 kyr), which closely track the amplitude modulation of the short eccentricity period. In contrast to d13C, the d18O signal additionally shows significant power in the 41 kyr band, and the 1.2 Myr amplitude modulation of the obliquity cycle is clearly imprinted in the 1146 d18O signal. Our results suggest that eccentricity was a prime pacemaker of middle Miocene climate evolution through the modulation of long-term carbon budgets and that obliquity-paced changes in high-latitude seasonality favored the transition into the “Icehouse” climate.

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Holbourn, Ann E, Kuhnt, Wolfgang, Schulz, Michael, Flores, José-Abel, Andersen, Nils (2007). Dataset: Stable isotopes measured on Miocene benthic foraminifera from ODP sites 202-1237 and 184-1146. https://doi.org/10.1594/PANGAEA.658956

DOI retrieved: 2007

Additional Info

Field Value
Imported on November 29, 2024
Last update November 29, 2024
License CC-BY-3.0
Source https://doi.org/10.1594/PANGAEA.658956
Author Holbourn, Ann E
Given Name Ann E
Family Name Holbourn
More Authors
Kuhnt, Wolfgang
Schulz, Michael
Flores, José-Abel
Andersen, Nils
Source Creation 2007
Publication Year 2007
Resource Type application/zip - filename: 202-1237_184-1146_stab-isotope
Subject Areas
Name: Geophysics

Related Identifiers
Title: Orbitally-paced climate evolution during the middle Miocene “Monterey” carbon-isotope excursion
Identifier: https://doi.org/10.1016/j.epsl.2007.07.026
Type: DOI
Relation: IsSupplementTo
Year: 2007
Source: Earth and Planetary Science Letters
Authors: Holbourn Ann E , Kuhnt Wolfgang , Schulz Michael , Flores José-Abel , Andersen Nils .