Much of the Arctic Ocean is fairly shallow compared to other oceans. There must have been times in the past during severe ice ages that a lot of what is now the ocean bed was above sea level. When was the last time that most of the arctic Ocean floor was above sea level? Going back further, were there ever forests, peat bogs or coal deposits on the present day ocean floor, and when were the internationally coveted oil reserves formed?
$\begingroup$ A link i found, it focusses on the quaternary, but maybe the references can help further: sciencedirect.com/science/article/pii/S0277379113002989 $\endgroup$– user18411Dec 10, 2019 at 13:17
1$\begingroup$ Thanks,ebv, it's very informative. $\endgroup$– Michael WalsbyDec 10, 2019 at 14:23
During glaciations, the shelves down to ~100m depth would have been above sea level, but they would have been covered by ice sheets.
The actual "ocean floor" would still be deep water. There is a general explanation of the oil formation here and here, although they don't say when (or where the continents were when the sediments were deposited), and again, this is on the shelves, not the floor.
"An overview of the petroleum geology of the Arctic" has:
Maps of palaeogeography of the Arctic based on Golonka's maps for the Late Devonian, the Middle Triassic, the Late Jurassic and the Middle Palaeogene, representing the times of deposition of some of the major Arctic source rocks
$\begingroup$ So can I take it that the floor of the Arctic Sea always was a barren place, apart from the sort of scanty marine life one can find there today? No forests or plant life, unlike Antarctica, which was once very different? $\endgroup$ Dec 10, 2019 at 10:41
$\begingroup$ Well, one can see that it is quite diverse, with shelves, epicontinental seas, deep ocean basins and even an active middle ocean ridge. If you want to ga back into the mesozoic with its different continental arrangements i would say "no", this can not be assumed. I am not so sure about the neogene, though, when high stands and ice cover took their turns. Are there no publications, yet ? There will be, soon(tm) ;-) $\endgroup$– user18411Dec 10, 2019 at 12:41
$\begingroup$ @MichaelWalsby Yes, Antarctica after rebound is mostly land. (I did not consider isostasy in the Answer - the Arctic shelves would be depressed by the weight of the ice sheets, so they might not be above sea level.) $\endgroup$ Dec 10, 2019 at 17:46