Underwater caves can read like locked time capsules—bones survive, surfaces remain detailed, and ancient animals leave chemical traces. Yet figuring out how megafauna remains accumulated and changed in these submerged “graveyards” has been notoriously difficult. A new study now offers a sharper way to interpret what bones are telling us.
Led by Griffith University PhD candidate Meg Walker, the research compares animal skeletal remains from two underwater cave systems in South Australia: Green Waterhole and Gouldens Sinkhole. The team used radiocarbon-dated bones as an anchor, then tracked how skeletons accumulated and were altered over years to centuries.
The core idea is that cave environments impose their own “preservation fingerprints.” By examining skeletal material from the macro scale down to the micro scale, the researchers documented differences in bone spatial patterns, surface condition, and fine-grained chemistry, including elements and proteins preserved within ancient cells.
Results show that underwater settings can preserve structure and surfaces exceptionally well. But preservation is not neutral: aquatic conditions also leave distinct biological and chemical signatures. Light gradients and living communities near cave entrances appear to play a major role.
Near brighter entrances, plant and algae growth can colonize bone surfaces, leaving compositional signals consistent with photosynthetic activity. Farther inside—where darkness is permanent—bones remain far more pristine, with fewer signatures linked to growth.
In contrast, dry caves did not show the same underwater-linked patterns. Instead, bone alteration was dominated by land-based microbial activity, including bacterial consumption, and damage shaped by root growth that can carve long grooves into exposed material.
Specialist cave divers from the Cave Divers Association of Australia collected historical bones from multiple native and introduced animals, including cows, kangaroos, emus, sheep, pigs, dingoes, rabbits, possums, quolls, and swamp rats. Some remains may even extend back to early European settlement in the 1840s.
By transforming these observations into a framework for interpreting site formation, the study helps bridge a major gap between modern underwater taphonomy and the mystery of how extinct megafauna fossils ended up preserved beneath water.
The findings are published in PLOS One in the article “Neotaphonomic characteristics of vertebrate site formation in underwater caves.” With this toolkit, archaeologists and palaeontologists gain a more testable route to reconstructing past environments from bone chemistry, texture, and trace biology.
Subject of Research: Underwater cave taphonomy and fossil preservation of vertebrate remains (including megafauna); bone chemistry, surfaces, and proteins
Article Title: “Neotaphonomic characteristics of vertebrate site formation in underwater caves”
Web References: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0343896
References: DOI: 10.1371/journal.pone.0343896
Image Credits: Steve Trewavas
Keywords: underwater caves, taphonomy, bone preservation, radiocarbon dating, proteins, geochemistry, algae, megafauna fossils, PLOS One
