Two warms and a cold; how a glaciation at the transition between the warm Pliocene and warm Miocene could have dried up the Mediterranean Sea

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Author(s): Tzanova, Alexandrina; Herbert, Timothy
Author Affiliation(s): Primary:
Brown University, Department of Earth, Environmental and Planetary Science, Providence, RI, United States
Volume Title: AGU 2018 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2018; American Geophysical Union 2018 fall meeting, Washington, DC, Dec. 10-14, 2018. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: The Late Miocene and Pliocene are spectacular examples of a time when the planet looked very much as it does today geographically, but the climate was much warmer than today, and the Earth's record shows major biome shifts. At the transition between these two epochs lies the Messinian Salinity Crisis (MSC: 5.9-5.35 Ma) the cause of which still puzzles us today. During this time the Mediterranean Sea desiccated and locked at least 5% of the salt contained in the global ocean away from the global oceanic conveyor belt. Controversy continually surrounds the balance of local versus global controls on the MSC and recent work points to a previously undocumented cool spell during an otherwise warm climate bracketing the desiccation. Episodic and enigmatic episodes of ice-rafted debris in the high latitude North Atlantic and North Pacific oceans of latest Miocene age have pointed to the possibility of at least ephemeral bi-polar glaciations at the time of the Messinian Salinity Crisis. Here we present orbital sea surface temperature reconstructions from the Equatorial Pacific (IODP Site U1338), North Atlantic (ODP Site 982), which aim at establishing the orbital scale synchronicity of decreasing sea surface temperatures and subsequent rebound in the context of Mediterranean desiccation and reflooding. We take advantage of recently developed, orbitally resolved age models for these sites, which have made addressing this curiosity possible. Sites 982 and U1338 show a trend towards deteriorating temperatures at the end of the late Miocene, circa 6 Ma, followed by an increasing trend towards the end of the Messinian Salinity Crisis. The coldest reconstructed temperatures during this interval are akin to values associated with the Holocene and are the culmination of a global cooling of 6-8°C that occurred from 10-5.35 Ma. While regional tectonics must have played a major role in determining sill depths of potential openings between the Mediterranean and Atlantic, the larger global context of episodic ice ages of late Miocene age have suggested a global eustatic overprint that may have determined the timing of isolation of the basin.
Year of Publication: 2018
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Cenozoic; Cores; East Pacific; Expedition 321; Expeditions 320/321; IODP Site U1338; Integrated Ocean Drilling Program; Marine sediments; Messinian; Messinian Salinity Crisis; Miocene; Neogene; North Pacific; Northeast Pacific; Pacific Equatorial Age Transect; Pacific Ocean; Paleo-oceanography; Paleosalinity; Sediments; Tertiary; Upper Miocene
Coordinates: N023028 N023028 W1175811 W1175811
Record ID: 2019061724
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