The ice sheet on Antarctica formed at the boundary of the Eocene and Oligocene epochs which is dated at 34 million years ago on the geology chronology of the earth. No mention is made as to what occurred at the boundary. If it was this would be logged under 'catastrophism' rather than geology. There are two theories – or two theories exist that mainstream is prepared to seriously consider. The first is based on climate change. This can of course be code for a number of things but in this instance involves some evidence which appears to show a decline in co2 levels (the usual bogeyman). In order to even treat this theory as serious you first have to believe co2 actually affects climate – currently undemonstrable. It's founded on belief rather than experiment.
The second theory (see https://phys.org/print405101707.html ) focuses on another CAGW stalwart, the ocean circulation system. Whilst there is no doubt that big changes in termperature can accompany ocean circulation swings one has to consider such swings might actually be a symptom of something else happening (of a not to be mentioned kind). The ocean circulation system is part of the earth system (of a watery planet) connecting the oceans with the atmosphere. Therefore if a catastrophic event had occurred we would expect some evidence of changes in the circulation system. If no changes occur it is likely no catastrophic event occurred. That is not to say the ocean circulation changes cannot happen by other means. Only that some kind of driver is necessary to set it in motion (and relying on co2 to do that smacks of an empty bowl on the breakfast table).
However, there is an added piece of geology to the second theory and that is demonstrable. What caused it to happen is open to question – but one could argue catastrophism might have played a role. At the Eocene/ Oligocene boundary the Drake Passage at the southern tip of S America as it abuts Antarctica, opened up, widened, or deepened (depth of ocean bed). One can imagine the latter if there was a change in the earth's geoid and therefore sea levels, and the first two as a result of tectonic upheavals of some kind. However, as mainstream is frenetically gradualist the theory is somewhat skewed and it is seriously suggested the Drake Passage probably opened up prior to 34,000 million years ago (at the tenuous date of 35,000 million years ago). When you read something like that it rings bells in your head. How do they know that? It just has to be a theory in order not to upset the uniformitarian apple cart. On that basis, we can safely say that the Drake Passage opened up at the same time as the Antarctic formed an ice sheet (not instantly of course but in a shorter period than one million years).
The Drake Passage is supposed to provide a nudge in order to create the ice sheet by setting in motion the Antarctic Circumpolar Current which encircles the southern continent. This is supposed to block the ability of warm water to come anywhere near Antarctica by forcing the warm water to move elsewhere – into the Pacific or into the southern Atlantic (as part of the ocean conveyor belt system as it is known). In other words, warm water doesn't encroach on the southern continent – and it gets very cold. You will find this hypothesis quoted as fact at numerous web sites, in journals and on blogs, even in the comments sections. It is a standard and often cited consensus point of view. Is it true? There is the problem, often avoided, that climate scientists like to tell us the West Antarctic Peninsular is melting – and indeed it does shed ice on many occasions. Why? Because warm tropical water from the Indian and Pacific oceans actually reaches the peninsular during the ocean conveyor belt process.
One has to wonder if the elephant in the room is being avoided. We may note this new paper is also the subject of a post by David Middleton at https://wattsupwiththat.com/2017/02/01/a-new-theory-about-the-formation-… … and he makes the point the new theory is the same as the old theory – which is why I didn't bother mentioning a new theory. In the comments section, 'bloke down the pub' (I like the moniker) at 6.54am, says 'sounds to me like they just wanted to keep co2 as the main driver of temperature change, even when accepting the opening of Drake Passage …' while at 8.37am 'Ed' asks, 'where was Antarctica 35 million years ago. Was it in the same position …' which is fair enough if Plate Tectonics was moving parcels of land around here and there. See below – but don't take it seriously as it is based on gradual movement.l