During the last Interglacial period the sea rose sixty - five feet above current levels. (religion-online.org)
If there is a high level of acidity, the measurement turns out and it works great for measuring the climate of the past all the way back to the last interglacial period 125,000 years ago. (sciencedaily.com)
Scientists discovered this by using sediment cores from around the world to reconstruct sea surface temperatures from the last interglacial period, which started roughly 129,000 years ago. (discovermagazine.com)