The Earth's History Written on Shells? Here's an Interesting Archive of Our Past

Aside from getting a record of Earth's past from ice cores, recent breakthroughs have found new potential archives of the planet's conditions, specifically climatic, through an interestingly new source: a shell.

A single-celled organism called Foraminifera, or informally forams, is one of the thousands of organisms living in the marine ecosystem. When this plankton dies, it leaves its shell to sink, which in return gets preserved on the sea beds. The shells, while still staying underwater, "grows" through time since it has calcium carbonate that aids in the incorporation of elements from sea water.

This characteristic was used by the researchers from the University of California-Davis, University of Washington, and Pacific Northwest National Lab. With high-end technology in understanding forams' growth atom-by-atom, the team discovered that the shells can actually provide a good picture of the earth's climate as far back as 200 million years ago. "Finding out how much magnesium there is in a shell can allow us to find out the temperature of seawater going back up to 150 million years," said the research's lead author Oscar Branson in ScienceDirect.

Read here: Press release from the University of California-Davis on Foraminifera atomic mapping

Atomic scale maps were produced by the team to analyze the processes and influences of the shells' environment on their growth over time. This was the first-ever attempt of quantifying the chemistry of a calcium carbonate biomineralization template.

"We know that shell formation processes are important for shell chemistry, but we don't know much about these processes or how they might have changed through time," Branson mentioned in the press release. "This adds considerable uncertainty to climate reconstructions."

The team applied two high-end techniques in creating their atomic maps to further understand the deposition of minerals to foram shells. These are Time-of-Flight Secondary Ionization Mass Spectrometry (ToF-SIMS) and Laser-Assisted Atom Probe Tomography (APT). The former was intended to map the elemental composition of a specimen surface, while the latter employs a three-dimensional technique of mapping to visualize the internal structure.