Northern Appalachian Anomaly
A new geology paper by Thomas Gernon and colleagues proposes that the Northern Appalachian Anomaly—a puzzling low-velocity zone under New England—is a migrating Rayleigh-Taylor instability triggered by Labrador Sea rifting about 80 million years ago.
This geodynamic legacy challenges conventional views of a mechanistic link to the Central Atlantic passive margin.
The Northern Appalachian Anomaly (NAA) is a prominent low-seismic-velocity zone, ∼400 km in diameter, in the asthenosphere beneath New England (northeastern USA). Previous studies interpreted this shallow feature, occurring at a depth of ∼200 km, as a thermal anomaly tied to edge-driven convection along the North American continental margins. Those studies recognized, however, that upwelling here is highly unusual given that the passive margin has been tectonically quiescent for ∼180 m.y. We propose an alternative model, based on geologic observations, geotectonic reconstructions, and geodynamic simulations, that the anomaly instead represents a Rayleigh-Taylor instability linked to the breakup of the distant Labrador Sea continental margin. A Labrador Sea origin at breakup, ca. 85−80 Ma, would imply the migration of a chain of Rayleigh-Taylor instabilities at a rate of ∼22 km/m.y., close to expected rates from geodynamic models. A migrating-instability origin for the anomaly can reconcile its spatial characteristics, depth profile, and position near a long-inactive continental margin. A corollary is that the north-central Greenland anomaly, a mirror-image of the NAA, also potentially originated at the time of breakup. Further, The Central Appalachian Anomaly may fit this model if it represents an early-stage instability linked to rifting onset in the Labrador Sea. The NAA and other associated anomalies viably represent a legacy of continental rifting and breakup along the distant Labrador Sea margins.
Eocoileus gentryorum
Paleontologists have found the fossilized remains of the extinct deer species Eocoileus gentryorum at the Early Pliocene Gray Fossil Site of northeastern Tennessee, the United States. The specimens are among the oldest records of the deer family in North America and are the only pre-Pleistocene records of deer from the Appalachian Highlands.
“The Gray Fossil Site continues to yield extraordinary discoveries that reshape our understanding of ancient life,” said Dr. Blaine Schubert, executive director of the Gray Fossil Site and Museum.
“Our team’s collaborative research is uncovering remarkable stories about how ecosystems have evolved over millions of years.”
“From tapirs and mastodons to these early deer, we’re revealing the incredible diversity of life that once flourished in Tennessee and how some species, like deer, have shown amazing resilience through geological time.”
In new research, the paleontologists examined the fragmentary remains — a skull, an upper molar and various limb bones — of Eocoileus gentryorum, a species of extinct deer first described in 2000.
Previously, Eocoileus gentryorum was known only from Florida, making the Tennessee discovery significant for understanding how quickly these early deer spread across the continent.
Interestingly, these ancient deer were notably smaller than most modern species.
“These early deer are generally smaller than modern deer species in the New World,” said Olivia Williams, a paleontologist at East Tennessee State University.
“The only smaller species today are the Key deer of Florida and brocket deer of Central and South America.”
“Fossil evidence from Washington and Florida shows these early deer dispersed rapidly coast-to-coast after their North American arrival, successfully adapting to diverse habitats from Pacific forests to Appalachian highlands,” said Dr. Joshua Samuels, also from East Tennessee State University.
“Deer have probably filled the same ecological role in Appalachian forests for nearly 5 million years, persisting and thriving through dramatic climate changes and habitat shifts that eliminated other large herbivores from the region.”
Vasio Vocontiorum
Empreinte de pas d'enfant romain (Gallo-Romains) sur une tuile d'argile rouge, réalisée pendant son séchage il y a 2000 ans. Vaison-la-Romaine, France (ancienne ville romaine de Vasio Vocontiorum).
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