Sun. Nov 27th, 2022

Reconstruction of eurypterids. (Image credit: Karen Carr)

Using advanced microscopes and chemical analysis, researchers investigated tiny liquid pockets within minerals , to gain insights into the geochemistry of an inland sea in North America, 390 million years ago.

First author of the paper, Sandra Taylor says, “We discovered we can actually dig out information from these mineral features that could help inform geologic studies, such as the chemistry of ancient oceans.

” The researchers were able to confirm that the water within the minerals matched the chemical profile of an ancient inland saltwater sea. The sea was in the region of the great lakes, stretching from Michigan in the US to Ontario in Canada.

In the Middle Devonian period, this inland sea harboured a coral reef ecosystem rivalling the Great Barrier Reef. The waters were inhabited by SUV-sized sea scorpions, along with now extinct creatures such as trilobites and the ancestors of horseshoe crabs. The waters receded, the biota became extinct, and eventually the sea dried up, leaving behind minerals embedded in sediments, which became the samples investigated in the new study.

One of the lead authors of the study, Daniel Gregory says, “We use mineral deposits to estimate the temperature of the ancient oceans. Salt deposits from trapped seawater are relatively rare in the rock record, so there are millions of years missing in the records, and what we currently know is based on a few localities where the salt is found. Sampling with this technique could open up millions of years of the geologic record and lead to new understanding of changing climate.” The researchers intended to sample pyrite, or a mineral known as fool’s gold, and were surprised to find embedded bubbles of seawater within.

A paper describing the findings has been published in Planetary Science Letters.

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