» Home > In the News

Ocean Acidification

23 December 2020

This doesn't concern modern doom mongering but real ocean acidifiction, in the remoter past. Back in the Cretaceous period – and perhaps related to a catastrophic event of some kind. In the Early Cretaceous there is evidence of an ocean anoxic event – oxygen deprivation. An entire family of coean dwelling nannoplankton appear to have been wiped out – almost. Calcium and strontium isotopes in their fossils have linked it to an igneous episode, we are told, the Ontong Java Plateau province eruption. This is roughly the size of Alaska and eruptions are said to have continued over 7 million years. This sounds like an impossibility and appears to be an artifact of geochronological gradualism. Or that is one way of looking at it. What we can accept, if not the dating system, is the actuality of a massive volcanic outpouring of lava that spewed out a lot of co2 into the atmosphere  – and here is the rub. Some geologists are convinced the Cretaceous represents a period of overheating of the planet – with a very high co2  content in the atmosphere. Their credibility is somewhat neutralised as they think in terms of a Cretaceous that lasted for an awful long time – millions and millions of years. This would require a continuous supply of co2, replenishing that what was washed out of the atmosphere on a regular basis. Even dating the eruption event over 7 million years is not enough. In spite of that the study has been published but the whole of the Cretaceous is odd. It is known mostly in the UK by the chalk formation. What we have is an igneous event and a spell of overheating of the planet. How long it lasted relies on the dating of sedimentary layers. In this case the laying down of the chalk in Europe and the US. Not all geologists might be onboard – but they are keeping their powder dry. The study was published in the journal Geology – see https://doi.org/10.1130/G47945.1

A 1600m long sediment core was used in the study, said to come from mid-Pacific mountains. The carbonites retrieved from the core were said to have lived and formed in a shallow sea in the tropics, dated between 127 and 180 million years ago. They are presently situated in the deep ocean which may imply they are sea mounts that were once much closer to the surface. That is an intriguing observation. It is of course unsurprising that a marine eruption, or one nearby, involving a vast outpouring of lava, was capable of causing ocean acidification. It is only the time  scale that is surprising – and the idea it takes a long time to lay down sediments. See https://phys.org/news/2020-12-volcanic-eruptions-triggered-ocean-acidifi…

Skip to content