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While calcite is insoluble in surface water, its solubility increases with depth (and pressure) and at around 4,000 m, the carbonate fragments dissolve.This depth, which varies with latitude and water temperature, is known as the carbonate compensation depth, or CCD.
The jawbone was recovered in sections and measures 5 feet (1.5 m) in length.
The researchers say the bone is clearly from a baleen whale — or whales that use baleen plates in their mouths to filter meals of tiny organisms out of seawater — and looks very similar to that of the gray whale, . Gray whales can be found today in quite strong numbers, but only in the Pacific Ocean, and even these had once teetered on the brink of extinction during eras when the whaling industry reigned.
Carbonate sediments are derived from a wide range of near-surface pelagic organisms that make their shells out of carbonate (Figure 18.10).
These tiny shells, and the even tinier fragments that form when they break into pieces, settle slowly through the water column, but they don’t necessarily make it to the bottom.
"The California grays looked exactly like the bones that were dug up in Scandinavia back in the 19th century," Ervan Garrison, a geoarchaeology professor at the University of Georgia, said in a statement, describing it as "one of the first instances where a living species was named based on the fossil evidence." The new specimen's age of approximately 36,570 years old makes it one of the oldest fossil finds in the western Atlantic basin, the researchers say.
And if the find indeed represents a Pleistocene-age gray whale, its oldest counterpart is a specimen found on the southern North Sea dating to 42,800 years ago.
Tiny fragments of this material plus other organic matter from marine plants and animals accumulate in terrigenous sediments, especially within a few hundred kilometres of shore.
As the sediments pile up, the deeper parts start to warm up (from geothermal heat), and bacteria get to work breaking down the contained organic matter.
Except within a few kilometres of a ridge crest, where the volcanic rock is still relatively young, most parts of the sea floor are covered in sediments.
This material comes from several different sources and is highly variable in composition, depending on proximity to a continent, water depth, ocean currents, biological activity, and climate.
Because this is happening in the absence of oxygen (a.k.a.Tags: Adult Dating, affair dating, sex dating