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  The timing of Mediterranean sapropel deposition relative to insolation, sea-level and African monsoon changes

Grant, K., Grimm, R., Mikolajewicz, U., Marino, G., Ziegler, M., & Rohling, E. (2016). The timing of Mediterranean sapropel deposition relative to insolation, sea-level and African monsoon changes. Quaternary Science Reviews, 140, 125-141. doi:10.1016/j.quascirev.2016.03.026.

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 Creators:
Grant, K.M., Author
Grimm, Rosina1, Author           
Mikolajewicz, U.2, Author           
Marino, G., Author
Ziegler, M., Author
Rohling, E.J., Author
Affiliations:
1Ocean Biogeochemistry, The Ocean in the Earth System, MPI for Meteorology, Max Planck Society, Bundesstraße 53, 20146 Hamburg, DE, ou_913556              
2Ocean Physics, The Ocean in the Earth System, MPI for Meteorology, Max Planck Society, ou_913557              

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Free keywords: Eastern Mediterranean
 Abstract: Abstract The Mediterranean basin is sensitive to global sea-level changes and African monsoon variability on orbital timescales. Both of these processes are thought to be important to the deposition of organic-rich sediment layers or ‘sapropels’ throughout the eastern Mediterranean, yet their relative influences remain ambiguous. A related issue is that an assumed 3-kyr lag between boreal insolation maxima and sapropel mid-points remains to be tested. Here we present new geochemical and ice-volume-corrected planktonic foraminiferal stable isotope records for sapropels \S1\} (Holocene), S3, S4, and \{S5\} (Marine Isotope Stage 5) in core \{LC21\ from the southern Aegean Sea. The records have a radiometrically constrained chronology that has already been synchronised with the Red Sea relative sea-level record, and this allows detailed examination of the timing of sapropel deposition relative to insolation, sea-level, and African monsoon changes. We find that sapropel onset was near-synchronous with monsoon run-off into the eastern Mediterranean, but that insolation–sapropel/monsoon phasings were not systematic through the last glacial cycle. These latter phasings instead appear to relate to sea-level changes. We propose that persistent meltwater discharges into the North Atlantic (e.g., at glacial terminations) modified the timing of sapropel deposition by delaying the timing of peak African monsoon run-off. These observations may reconcile apparent model–data offsets with respect to the orbital pacing of the African monsoon. Our observations also imply that the previous assumption of a systematic 3-kyr lag between insolation maxima and sapropel midpoints may lead to overestimated insolation–sapropel phasings. Finally, we surmise that both sea-level rise and monsoon run-off contributed to surface-water buoyancy changes at times of sapropel deposition, and their relative influences differed per sapropel case, depending on their magnitudes. Sea-level rise was clearly important for sapropel S1, whereas monsoon forcing was more important for sapropels S3, S4, and S5.

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Language(s): eng - English
 Dates: 2016-042016-05
 Publication Status: Issued
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1016/j.quascirev.2016.03.026
BibTex Citekey: Grant2016125
 Degree: -

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Title: Quaternary Science Reviews
Source Genre: Journal
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Pages: - Volume / Issue: 140 Sequence Number: - Start / End Page: 125 - 141 Identifier: ISSN: 0277-3791