North Carolina’s Sandhills just got a startling update to their past. Geologists have identified a thin package of layers that record an extraterrestrial hit and the tsunami that followed, tucked into a hillside in Moore County.
The layers sit in a shallow channel carved into older Eocene sands and clays. The team named this young package the Mount Helicon Formation and tied it to a late Eocene bolide impact, a fast moving meteor or comet that strikes Earth.
What the North Carolina team found
Lead author G. Robert Ganis, Consulting Geologist in Southern Pines, NC, reports that a one yard thick sequence at Paint Hill contains four distinct beds stacked in order, from impact debris to tsunami deposits.
Bed 1 is about 17 inches of dark, sandy clay rich in carbon glass and rock fragments, with iridium measured at 14 to 18 parts per billion, far above typical crustal levels.
Bed 2 is roughly 3.5 inches of silt with small agglutinated pellets and 2 to 6 parts per billion iridium.
Bed 3 is a 2.4 inch breccia, a jumbled mix of ripped up soil and seafloor fragments, that still carries 1 to 2 parts per billion, and Bed 4 is about 6 inches of coarse sand likely emplaced by a later tsunami pulse.
Links to Chesapeake Bay
The site lies about 235 miles southwest of the buried Chesapeake Bay impact structure, the event suspected to have launched this debris toward the Carolinas.
“This buried, late Eocene complex crater is the largest known impact crater in the United States and the seventh largest known on Earth,” stated the U.S. Geological Survey, in a 2005 crater overview.
The Paint Hill channel fill makes geological sense in that context. An impact of that size would loft ejecta across the region, then send water surging inland.
Iridium in the Paint Hill impact area
Iridium is rare in Earth’s crust but common in many meteorites, so a spike is a strong indicator of impact fallout.
One 2021 study linked the iridium layers from The Chicxulub impact event, occurring ~66 million years ago, directly to the Cretaceous-Paleogene (K-Pg) mass extinction boundary sections worldwide.
Another impact fingerprint is shocked quartz, which forms under extreme pressures.
Such grains from the Upper Eocene have been documented in east central Georgia, strengthening the regional picture of ejecta distribution, as reported in a 2004 study.
Bed 3 at Paint Hill is packed with both marine and terrestrial clasts: fossil bearing chert, rolled chunks of older strata, petrified wood, and ripped up paleosol, a soil horizon hardened by iron.
That mix tells a story of powerful, short lived flow that bulldozed landward from the sea into a low area.
How bed 2 formed in the sky
The silt rich Bed 2 includes small, loosely bound pellets that resemble accretionary lapilli, aggregates formed when ash and fine particles clump together in moist air.
Impact plumes can make such pellets, though their textures differ from volcanic examples.
“Meteorite impact generated accretionary lapilli are not well studied,” observed M. S. Huber from the University of Vienna, in a 2017 research summary.
The Paint Hill particles fit that under studied category and help fill a gap in real world observations.
Reading the Paint Hill impact beds
The basal Bed 1 records the first seconds to minutes, when fine ejecta and carbon rich debris fell out and settled into the channel.
The high iridium spike in this layer matches that interpretation and aligns with how impacts concentrate siderophile metals.
Bed 2 tracks the lingering fallout of finer particles as the plume thinned. The accretionary lapilli fell like pellets, signaling humid air that encouraged grain-to-grain sticking during descent.
When the ocean rushed in
Bed 3 captures the inland surge. A slurry of seawater and sediment tore up soil blocks from nearby uplands, rolled slabs of older beds, and dropped them into the channel as flow waned.
Bed 4 likely represents a later pulse or backwash that reoccupied the channel and laid down clean sand and a bit of pea gravel.
Its swirled structures and erosive base match the stop and start behavior of oscillating tsunami flows in confined lows.
The impact beds cut into an older package of nearshore Eocene strata that the team named the Paint Hill Formation.
Those older deposits host marine fossils and show repeated fining and coarsening cycles that reflect shifting shoreline conditions along the Upper Atlantic Coastal Plain.
Soils at the top of that older unit had time to harden before the impact, which is why chunks of paleosol ended up in Bed 3.
That detail means land in this part of North Carolina was emergent by late Eocene time, then was abruptly disturbed by a tsunami surge.
Why the Paint Hill impact matters
The Paint Hill sequence shows that effects from the Chesapeake Bay impact reached well into the Carolinas. It also supplies a local marker bed that can help correlate Eocene sections across the region.
Naming the Mount Helicon Formation gives geologists a common language for this specific impact and tsunami package.
That improves maps, clarifies sea level history, and sets targets for follow up fieldwork at similar elevations to the east and south.
Impact science thrives on multiple lines of evidence. Here, anomalous iridium, lapilli like fallout, tsunami style breccia, and a sandy cap line up in a tidy sequence that matches physics and regional context.
Each feature answers a different question about timing and process. Together, they turn a quiet Sandhills slope into one of the clearest places to read the day an object from space changed the Atlantic coast.
The study is published in Southeastern Geology.
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