Scientists have discovered that large sections of the seafloor beneath the North Sea appear to be flipped upside down, unveiling a rare geological process that could reshape how we understand sediment movement and subsurface stability. The formations were identified using seismic imaging techniques that revealed large-scale structural inversions.
According to Science Alert, these findings are based on data showing dense sand layers positioned beneath lighter sediment, contradicting expected geological layering. The research focuses on a region where the seafloor has undergone significant reorganization over millions of years, but reveals little so far about the broader geological implications beyond the local context.
Geological Structures Challenge Conventional Layering
A team of researchers from the University of Manchester and Aker BP in Norway has identified hundreds of vast sand mounds, some spanning several kilometers across, that sit atop older, lighter sediments. This phenomenon directly contradicts traditional geological principles, where older layers lie beneath younger ones.
“This discovery reveals a geological process we haven’t seen before on this scale,” says geophysicist Mads Huuse of the University of Manchester.
“What we’ve found are structures where dense sand has sunk into lighter sediments that floated to the top of the sand, effectively flipping the conventional layers we’d expect to see and creating huge mounds beneath the sea.”
Stratigraphic Inversion and the Birth of Sinkites
This unusual layering is the result of a process called stratigraphic inversion, which in this case has led to the formation of previously unknown structures the team calls sinkites. In seismic scans of the region, these sinkites appear where denser, younger layers of sand have migrated downward into softer, porous materials, forcing the lighter sediment to rise.
The buoyant upper layers, now sitting atop the denser sands, have been dubbed floatites. According to the researchers, the upper layers are composed of a
“Lightweight, rigid, and porous layer predominantly made up of microscopic marine fossils – a structure naturally less dense than the heavy sand beneath.”
Seismic Activity May Have Caused Sediment Collapse
The team estimates the process occurred approximately 5.3 million years ago, at the boundary between the Miocene and Pliocene epochs. They believe that disruptions such as earthquakes could have broken up the upper layer into sand, which then sank into the weaker underlying fossil-rich layer. Over millions of years, this inverted structure was buried under new layers of sediment, shaping the seafloor as it exists today.
“Understanding how these sinkites formed could significantly change how we assess underground reservoirs, sealing, and fluid migration – all of which are vital for carbon capture and storage,” says Huuse.
This research shows how fluids and sediments can move around in the Earth’s crust in unexpected ways.
Insights From Seismic Imaging
Huuse and Jan Erik Rudjord of Aker BP used detailed seismic data to uncover the anomaly. As acoustic waves move through the Earth, they reflect differently depending on the density of the materials encountered. This allowed the team to identify patterns in the seafloor strata that revealed large-scale inversions across multiple sites.
The discovery adds to a growing body of evidence that the seafloor is far more dynamic than previously thought, especially in regions where sediment density, fluid content, and tectonic stresses interact in complex ways.
The findings have sparked mixed reactions within the scientific community.
“As with many scientific discoveries there are many skeptical voices, but also many who voice their support for the new model. Time and yet more research will tell just how widely applicable the model is,” says Huuse.
If validated, the model could inform future studies of carbon storage, hydrocarbon reservoirs, and the integrity of geological seals used in climate-related engineering projects.
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