> For instance, drilling in the Gulf of Mexico in 1967 revealed a vast layer of salt from the Jurassic beneath the oceanic sediments. The total global amount of

> For instance, drilling in the Gulf of Mexico in 1967 revealed a vast layer of salt from the Jurassic beneath the oceanic sediments. The total global amount of halite (salt deposits) discovered was astonishing: the minimum estimate is 19.6 quintillion kilograms (19.6 × 1018 kg), or more than half of the total salt in the oceans today — the maximum estimate is that an unbelievable 95% of the present total is trapped in halite deposits. If all of this had been dissolved at one time, the salinity of seawater would have been much higher: 57‰ to 73‰ instead of today’s 34‰ to 35‰. This extreme scenario is unlikely, but one thing is clear: the salinity of the oceans has varied significantly over geologic time. The problem is how to quantify this change.