MULLICA HILL — It may be hard to imagine today, but millions of years ago South Jersey was covered by the ocean – Harrison Township was “under the sea.” Ancient sharks, carnivorous snails, sponges and echinoderms (spiny marine animals) were the first inhabitants.
At times, due to advancing and receding shorelines, land-dwelling species like the dinosaur Hadrosaurus as well as plants and trees were washed to the sea bottom. Rivers flowing from ancient glaciers in North Jersey transported rocks and ancient plant and animal remains southward.
Eventually, the remains of all these plants and animals were deposited on the sea floor, forming a layer of a rich “greensand”, also known locally as marl. This material was actively mined at locations near Mullica Hill, Ewan and Harrisonville in the 19th century.
Marl was first used as a fertilizer. It later proved valuable as a water filtering agent. Evidence of all this truly ancient history is featured in the Harrison Township Historical Society’s new Fall exhibition, Under the Sea: Our Prehistoric Past.
For well over a century, fossil sites in the township, especially around Mullica Hill, have been well-known and documented. The exhibition showcases an array of fossil specimens that were collected locally, some over 100 million years old.
Under the Sea also explores the marl-mining industry that thrived in Gloucester County in the 19th century. The last surviving mine near Sewell only recently ceased operations. Little evidence of this industry survives save a few unfilled quarries and “Marl Road,” a South Harrison street.
Some of the sedimentary layers formed bands of iron-cemented sandstone, sometimes called “ironstone” or “Jersey sandstone” locally. This reddish brown stone was also mined and most frequently used to build foundations and small farm outbuildings, a few of which survive. Examples of this unusual material and photos of buildings are also featured.
Guest Curator Shirley S. Albright, retired Assistant Curator of Natural History at the New Jersey State Museum, has secured specimens from the collections of the New Jersey State Museum, Philadelphia’s Academy of Natural Sciences of Drexel University and from private sources which underscore the significance of the area’s geological history. Many specimens will be on view for the first time.
Under the Sea is on view in the Old Town Hall Museum Saturdays and Sundays, 1-4 p.m., Oct. 5 through Dec. 14. Admission is free.
The Museum is located at 62-64 South Main St., in historic Mullica Hill. For information call (856) 478- 4949 or visit the Society’s website, www.harrisonhistorical.com.