Morocco fossils show life thrived without sunlight 182 million years ago

Unusual “wrinkled” structures preserved in Jurassic rocks in High Atlas Mountains formed in deep, dark marine environments rather than shallow sunlit waters, challenging long held assumptions about how early microbial life shaped the fossil record, according to a study published in the journal Geology.

The structures, found in the Tagoudite Formation in the Central High Atlas Mountains, date back about 182 million years and were formed at depths of around 200 metres, well below the reach of sunlight.

Scientists have traditionally linked such features to photosynthetic microbial mats that require light, typically in shallow coastal environments.

The new findings point instead to chemosynthetic microbial communities, organisms that derive energy from chemical reactions rather than sunlight.

These microbes likely fed on compounds such as sulfides in sediment rich in organic matter, forming layered mats that shaped the sediment surface into ridges and grooves ranging from millimetres to centimetres in size.

Microscopic and chemical analysis of the rocks revealed elevated carbon concentrations beneath the wrinkled surfaces, indicating biological activity and supporting a microbial origin.

The structures include elongated ridges and troughs consistent with known microbially induced sedimentary formations, but their depth makes a photosynthetic origin unlikely.

Researchers said the conditions that allowed these formations to be preserved were linked to sediment flows known as turbidites, which rapidly buried organic material and created low oxygen environments. These conditions may have limited animal activity, preventing the destruction of microbial mats and allowing the structures to fossilise.

The study suggests that deep marine environments may have hosted more widespread microbial ecosystems than previously thought, and that similar structures found in ancient rocks could have been misinterpreted.

Scientists said turbidite deposits could represent an under recognised window into ancient chemosynthetic ecosystems, expanding the range of environments where early life is known to have existed and been preserved.