Eccentricity‐Paced Southern Hemisphere Glacial‐Interglacial Cyclicity Preceding the Middle Miocene Climatic Transition

2018 ◽  
Vol 33 (7) ◽  
pp. 795-806
Author(s):  
C. Ohneiser ◽  
G. S. Wilson
Keyword(s):  
Southern Hemisphere ◽  
Middle Miocene ◽  
Climatic Transition ◽  
Middle Miocene Climatic Transition

scholarly journals Middle Miocene shark teeth from the southern margin of the Pannonian basin system (Serbia, Central Paratethys)

2019 ◽  
Vol 80 (1) ◽  
pp. 29-43
Author(s):  
Gordana Jovanovic ◽  
Nicolae Trif ◽  
Vlad Codrea ◽  
Dragana Djuric
Keyword(s):  
Geographical Distribution ◽  
Middle Miocene ◽  
Pannonian Basin ◽  
Warm Period ◽  
Central Paratethys ◽  
Shark Teeth ◽  
Climatic Transition ◽  
Basin System ◽  
High Diversity ◽  
Middle Miocene Climatic Transition

This paper describes Middle Miocene (Badenian) shark teeth from Serbia and discusses their geographical distribution at other localities of the Central Paratethys. The shark teeth originate from Visnjica (near Belgrade), from Visnjica Clay, or the ?Pleurotoma Clay?. The variety of sharks is very low, but according to these fossils Visnjica is the richest among serbian localities. The sharks teeth reported in the paper belong to the following taxa: Otodus (Megaselachus) megalodon (AgAssiz, 1835), Hemipristis serra AgAssiz, 1835 and Odontaspididae indet. The high diversity of invertebrates (molluscs, echinoids, corals etc.) and other coeval fossil assemblages indicate a warm period (the Middle Miocene Climatic Optimum), which preceded the Middle Miocene Climatic Transition.

scholarly journals The role of eastern Tethys seaway closure in the Middle Miocene Climatic Transition (ca. 14 Ma)

2013 ◽  
Vol 9 (6) ◽  
pp. 2687-2702 ◽  
Author(s):  
N. Hamon ◽  
P. Sepulchre ◽  
V. Lefebvre ◽  
G. Ramstein
Keyword(s):  
General Circulation ◽  
Middle Miocene ◽  
Ice Sheet ◽  
Water Source ◽  
Meridional Overturning Circulation ◽  
Oceanic Circulation ◽  
Climatic Transition ◽  
The Impact ◽  
Final Closure ◽  
Middle Miocene Climatic Transition

Abstract. The Middle Miocene Climatic Transition (MMCT, approximately 14 Ma) is a key period in Cenozoic cooling and cryospheric expansion. Despite being well documented in isotopic record, the causes of the MMCT are still a matter of debate. Among various hypotheses, some authors suggested that it was due the final closure of the eastern Tethys seaway and subsequent oceanic circulation reorganisation. The aim of the present study is to quantify the impact of varying Tethys seaway depths on middle Miocene ocean and climate, in order to better understand its role in the MMCT. We present four sensitivity experiments with a fully coupled ocean-atmosphere general circulation model. Our results indicate the presence of a warm and salty water source in the northern Indian Ocean when the eastern Tethys is deep open (4000 or 1000 m), which corresponds to the Tethyan Indian Saline Water (TISW) described on the basis of isotopic studies. This water source is absent in the experiments with shallow (250 m) and closed Tethys seaway, inducing strong changes in the latitudinal density gradient and ultimately the reinforcement of the Antarctic Circumpolar Current (ACC). Moreover, when the Tethys seaway is shallow or closed, there is a westward water flow in the Gibraltar Strait that strengthens the Atlantic Meridional Overturning Circulation (AMOC) compared to the experiments with deep-open Tethys seaway. Our results therefore suggest that the shoaling and final closure of the eastern Tethys seaway played a major role in the oceanic circulation reorganisation during the middle Miocene. The results presented here provide new constraints on the timing of the Tethys seaway closure and particularly indicate that, prior to 14 Ma, a deep-open Tethys seaway should have allowed the formation of TISW. Moreover, whereas the final closure of this seaway likely played a major role in the reorganisation of oceanic circulation, we suggest that it was not the main driver of the global cooling and Antarctica ice-sheet expansion during the MMCT. Here we propose that the initiation of the MMCT was caused by an atmospheric pCO2 drawdown and that the oceanic changes due to the Tethys seaway closure amplified the response of global climate and East Antarctic Ice Sheet.

scholarly journals The role of East-Tethys seaway closure in the middle Miocene climatic transition (ca. 14 Ma)

2013 ◽  
Vol 9 (2) ◽  
pp. 2115-2152
Author(s):  
N. Hamon ◽  
P. Sepulchre ◽  
V. Lefebvre ◽  
G. Ramstein
Keyword(s):  
Middle Miocene ◽  
Ice Sheet ◽  
Circulation Model ◽  
Water Source ◽  
Meridional Overturning Circulation ◽  
Oceanic Circulation ◽  
Climatic Transition ◽  
The Impact ◽  
Final Closure ◽  
Middle Miocene Climatic Transition

Abstract. The middle Miocene climatic transition (MMCT, approximately 14 Ma) is a key period in Cenozoic cooling and cryospheric expansion. Despite it is well documented in isotopic record, the causes of the MMCT are still a matter of debate. Among various hypotheses, some authors suggested that it was linked with the final closure of the East-Tethys seaway and subsequent oceanic circulation reorganisation. The aim of the present study is to quantify the impact of varying East-Tethys seaway depths on middle Miocene ocean and climate, in order to better understand its role in the MMCT. We present four sensitivity experiments with a fully coupled ocean-atmosphere generalized circulation model. Our results indicate the presence of a warm and salty water source in the northern Indian Ocean when the East-Tethys is deep-open (4000 or 1000 m), which corresponds to the Tethyan Indian Saline Water (TISW) described on the basis of isotopic studies. This water source is absent in the experiments with shallow (250 m) and closed East-Tethys, inducing strong changes in the latitudinal density gradient and ultimately the reinforcement of the Antarctic Circumpolar Current (ACC). Moreover, when the East-Tethys seaway is shallow or closed, there is a westward water flow in the Gibraltar Strait that strengthens the Atlantic meridional overturning circulation (AMOC) compared to the experiments with deep-open East-Tethys. Our results therefore suggest that the shoaling and final closure of the East-Tethys seaway played a major role in the oceanic circulation reorganisation during the middle Miocene. The results presented here provide new constraints on the timing of the East-Tethys seaway closure, and particularly indicate that, prior to 14 Ma, a deep-open East-Tethys should have allow the formation of TISW. Moreover, whereas the final closure of this seaway likely played a major role in the MMCT, we suggest that it was not the only driver of the global cooling and Antarctica ice sheet growth. Here, we propose that the initiation of the MMCT may have been an atmospheric pCO2 drawdown and that the oceanic Changes due to the East-Tethys seaway closure amplified the response of global climate and East-Antarctic Ice Sheet.

Tracking ice-sheet dynamics by detrital feldspar Pb-isotope and 87Rb/87Sr dating during the Middle Miocene Climatic Transition, Weddell Sea, Antarctica

2021 ◽  
Author(s):  
Roland Neofitu ◽  
Chris Mark ◽  
Suzanne O'Connell ◽  
Samuel Kelley ◽  
Delia Rösel ◽  
...  
Keyword(s):  
Deep Sea ◽  
Middle Miocene ◽  
Ice Sheet ◽  
Weddell Sea ◽  
Provenance Analysis ◽  
Pb Isotope ◽  
Iceberg Calving ◽  
Climatic Transition ◽  
The Antarctic ◽  
Middle Miocene Climatic Transition

<p>Antarctic ice-sheet instability is recorded by ice-rafted debris (IRD) in mid- to high-latitude marine sediment, especially throughout climate transitions. The middle Miocene climatic transition (MMCT), 14.2 to 13.8 Ma, which marks the end of a significant warm period during the mid-Miocene, saw a rapid cooling of ca. 6-7 °C in the high-latitude Southern Ocean. This climatic shift was also accompanied by a global δ<sup>18</sup>O excursion of ca. 1‰, indicating a time of global cooling and significant Antarctic ice expansion (Shevenell et al., 2004). The MMCT is recorded by numerous IRD-rich sediment horizons in deep-sea sediment cores around the Antarctic margin, reflecting iceberg calving during times of ice-sheet instability. Resolving the locations of iceberg calving sites by detrital provenance analysis during the MMCT will be an important tool for forecasting effects of anthropogenic climate change.</p><p>Here we present results of a multi-proxy provenance study by using K- and plagioclase feldspar, selected due to their relative abundance in clastic sediment, and tendency to incorporate Rb (Kfs only), Pb, and Sr at analytically useful concentrations, thus enabling source-terrane fingerprinting. While Pb-isotope fingerprinting is an established method for provenance analysis of glaciogenic sediment (Flowerdew et al., 2012), combining in-situ Sr-isotope fingerprinting with <sup>87</sup>Rb/<sup>87</sup>Sr dating is a novel approach. These techniques are applied to deep-sea core ODP113-694, which was recovered from the Weddell Sea; as this is located ca. 750 km from the continental rise, in 4671.3 m of water. This location is ideal, as it acts as a major iceberg graveyard making it a key IRD depocenter (Barker, Kennett et al., 1988). Within the core, several IRD layers were identified and analysed with preliminary depositional ages of 14 to 14.4 Ma.</p><p>We discuss the implications of our results in terms of location of active iceberg calving sites and further consider the viability of our multi-proxy provenance approach to the Antarctic offshore.</p><p>Barker, P.F., Kennett, J.P., et al., 1988, Proc. Init. Repts. (Pt. A): ODP, 113, College Station, TX (Ocean Drilling Program).</p><p>Flowerdew, M.J., et al., 2012, Chemical Geology, v. 292–293, p. 88–102, doi: 10.1016/j.chemgeo.2011.11.006.</p><p>Shevenell, A.E., et al., 2004, Science, v. 305, p. 1766-1770, doi: 10.1126/science.1100061.</p>

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