Please look at the attached figure (Heiko Palike et al., 2012, nature). At ~34 Ma, we can find the CCD deepening, carbonate accumulation, pCO2 decreasing, ice-sheet expansion, and Antarcitic cooling. Mybe the trigger was ice-sheet expansion induced by low insolation. If the decrease of the pCO2 was uptaked by ocean, will be not good for carbonate accumulation. Isn't that a bit of a contradiction? How about the relationship between these variations? Thank you very much!
You will find a brief summary of the changes occurring in the waters around Antarctica in Sciences in Cold and Arid Regions 5(3); 259-275. doi: 10.3724/SP.J.1226.2013.00259 There are a number of relevant references in it. I hope this helps.
Stuart.
Dear Xiaolin Ma,
I have studied the Eocene-Oligocene Transition a few years ago during my Master's, so I can give you a few thoughts. However, I am not sure this is up to date.
You could have have look at these references:
Zachos J.C. and Kump L.R. (2005) 'Carbon cycle feedbacks and the initiation of Antarctic glaciation in the earliest Oligocene', Global and Planetary Change, vol. 47, no 51, pp. 66.
Scher, H.D., Bohaty, S.M., Zachos, J.C. and Delaney, M.L. (2011) "Two-stepping into the icehouse: East Antarctic weathering during progressive ice-sheet expansion at the Eocene-Oligocene Transition', Geology, vol. 39, no 4, pp. 383.
These two references look at other feedbacks that could have played a role in the EOT.
Low insolation could have initiated an ice-sheet in Antarctica. This ice-sheet may have been dynamic and wet-based, so that it physically weathered Si sediments, drawing down some atmospheric CO2 in the process (Scher et al., 2011). Zachos and Kump (2005) proposed that lower temperatures enhanced oceanic circulation, increasing the nutrient cycle and leading to increased drawdown of atmospheric CO2.
I think the key is to look at other feedbacks triggered by a lowering of insolation due a special orbital configuration.
I hope this helps,
Julie
The formation of Large Igneous Provinces (LIPs) may have been responsible for the formation of small ice sheets at the start and end of the Cretaceous. At the start of the Cretaceous the Whitsunday SLIP may have created an ice sheet in Antarctica. At the end of the Cretaceous the Deccan Traps may have produced an ice sheet in the far north, despite high levels of atmospheric CO2.
Volcanic activity associated with the opening of Drakes Passage or the Tasmanian Gateway, or even perhaps the Columbia River LIP may have produced a volacanic veil which cooled the planet enough for the Antarctic Ice sheet to form.
There is a paper here that might help: https://www.sciencemag.org/content/312/5772/428.full
Additional references that will be helpful:
Coxall, H.K., Wilson, P.A., Pälike, H., Lear, C.H., and Backman, J., 2005, Rapid stepwise onset of Antarctic glaciation and deeper calcite compensation in the Pacifi c Ocean: Nature, v. 433, p. 53–57, doi: 10.1038/nature03135.
Coxall, H. K., and P. A. Wilson (2011), Early Oligocene glaciation and productivity in the eastern equatorial Pacific: Insights into global carbon cycling, Paleoceanography, 26, PA2221, doi:10.1029/2010PA002021.
Lear, C.H. et al., 2008, Cooling and ice growth across the Eocene-Oligocene transition: Geology, v. 36(3), p. 251-254.
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