by Lou Varricchio
MIDDLEBURY | A recent rediscovery of a classic, 19th-century fossil site in northwestern Vermont is giving paleontologists a better understanding of Earth’s earliest lifeforms.
A trio of geo researchers announced their discovery in Geology, a journal of the Geological Society of America.
Geologists Giovanni Pari of Canada, Derrick Briggs, of the Yale Peabody Museum, and Robert Gaines of Pomona College in California, made the rediscovery last summer. The exact location of the fossil find is not being published to prevent trespassing and fossil poaching.
Vermont’s Parker Formation, a slate deposit appearing near St. Albans in the Lake Champlain Valley, holds some of the world’s earliest soft-bodied marine creatures that were preserved despite the original shale being transformed, under heat and pressure, into slate.
The Parker quarry lagerstätte, or PQL, within the Parker Formation, is where the marine invertebrate fossils were first found is on private property. The German word lagerstätte is used by geologists to describe a sedimentary deposit that exhibits “extraordinary fossils with exceptional preservation”—notably with soft tissues that are well preserved.
The fossils were discovered by Noah Parker in 1855 and are said to rival the famous Burgess Shale fossils of British Columbia in Canada. What makes the PQL important to science is that Parker’s fossils were discovered 25 years before the discovery of the Burgess Shale. The Parker fossils of 1855 are now in the collection of the Yale Peabody Museum in Connecticut.
The ancient St. Albans creatures were buried off the coast of a now-vanished, prehistoric supercontinent called Laurentia by geologists. Long before today’s continents broke apart and drifted to their current positions, Laurentia was situated near the warm equator.
According to the International Commission on Stratigraphy, “The Earth was generally cold during the early Cambrian, probably due to the ancient continent of Gondwanaland covering the South Pole and cutting off polar ocean currents. However, average temperatures were… higher than today.”
The researchers reported that the Parker shale was deposited in deep ocean water during the Cambrian Period more than 500 million years ago. The fossils include arthropods (crablike animals) as well as brachiopods (bivalved, clamlike animals). The common trilobite Olenellus and others were also found. Soft parts of the creatures rarely preserved in fossils are what make the discovery important to paleontology.
Among the Vermont fossils is Tuzoia a large, extinct genus of bivalved arthropod; it grew up to seven inches in length (see photo). Tuzoia is best known to paleontologists from the original Burgess Shale fossil discovery.
“Conditions in the PQL were clearly favored for high-fidelity soft-tissue preservation, but the rarity of fossils suggests that few animals reached the depositional environment,” according to the researchers. “This setting represents the low end of the oxygen gradient along which Burgess Shale-type preservation occurs… Our future searches targeting claystone event beds should confirm the potential of the Parker Formation as a source of new soft-bodied discoveries.”
Republished from April 27 Sun Community News in Middlebury.