Fossil Discoveries at Stratford Cliffs
The Cliffs at Stratford present a bold escarpment to the view. . .I asked a fisherman if he knew of any fossil bones in the cliffs; he replied, some giants were buried there, but he did not like to meddle with them.
-John Finch, English geologist, on visit to Stratford in the 1820s
When Thomas Lee purchased “The Cliffs” property in 1717, he did not know that he had acquired a geological phenomenon that existed in only three other places in the world–the Los Angeles basin, Austria and Belgium. The Cliffs, part of the Calvert formation, are composed of compacted sea matter dating from the Miocene Epoch–approximately 17 to 10 million years ago–when rising land replaced the ocean that once covered Stratford. The 150-foot-high cliffs along the Potomac River, formerly the sea floor, provided just the right set of circumstances for the fossilization of animal remains. Fossilized remains indicate a sea filled with primitive shark-toothed porpoises, salt-water crocodiles, sea cows, gopher turtles, rays, whales and sharks. Thousands of shark teeth found along this area of the Potomac attest to the frequency of the sharks, largest among them being Carcharodon megalodon, or Giant White Shark, with teeth measuring 7 inches or more.
Through the years, visitors to Stratford have enjoyed walking the beach and picking up an occasional shark’s tooth along the water’s edge. In the past decade, unlike the fisherman mentioned in the quote above, more than a few persons ravaged the face of the cliffs with picks, shovels and other heavy digging equipment. This indiscriminate mining for fossils was slowly, but surely, destroying undocumented fossil history and creating “unnatural” erosion.
To protect and preserve the cliffs and the public, the Board of the Robert E. Lee Memorial Association closed the shoreline bordering the cliffs to the public in 1997. The potential for dangerous cliff slides is obvious even to the casual observer. Due to the danger of the landslides caused by cliff erosion and the serious injuries (including death) they can cause, climbing upon and walking beneath the cliffs is prohibited. Visitors today are allowed to hunt for fossils along the well-marked strip of open beach adjacent to the mill and landing area. Trespassers outside of the designated area for fossil hunting will be prosecuted.
Monitoring for Endangered Miocene Fossils
A program for monitoring the cliffs for important fossil specimens is now in place. The recovery of significant Miocene fossils before the loss of their integrity due to natural forces is important to interpreting the plantation’s landscape in its entirety. The protection of its paleontological resources is vital to the Robert E. Lee Memorial Association’s responsible stewardship of the Stratford property. Dr. Lauck Ward, consulting paleontologist from the Virginia Museum of Natural History, inspects the cliffs periodically for endangered or newly exposed fossils. Dr. Ward’s evaluation of the importance and desirability of a particular fossil specimen, along with the amount of possible ground disturbance, will deterine whether or not the specimen will be recommended for excavation. Dr. Ward also leads several paleontological field trips to the beach area each year.
Erosion Research Study
Linda Birdsong, a former graduate student from the University of North Carolina, Greensboro,researched the Stratford cliffs for her Master’s Thesis in Applied Geography. Ms. Birdsong visited the plantation over a two-year time period to photograph and document areas of the cliffs having severe erosion problems. The rate and possible causes of erosion were determined by analyzing a series of aerial photographs and maps as well as using monitors to measure the flow of water from the cliffs. The rate of the most severe erosion was calculated to be around five feet per year.
The most severe erosion problems relate to large areas of cultivated land bordering the cliffs, particularly the Cliff Field. Rain water enters the ground in the Cliff Field until it reaches an impermeable layer containing iron deposits (called the Yorktown layer). The water follows this layer until it reaches the cliff face, where it flows out, creating unnatural crevices and causing an increase in landslides.
An integral part of Ms. Birdsong’s study were suggestions for remedial actions to slow down the erosion in the areas of the cliffs with above-normal rates. At the present time, the land adjacent to the cliff edge at Cliff Field is being left out of cultivation and allowed to grow up with natural vegetation. Stratford Hall has also pursued funding for a riparian planting plan to replace trees within a certain distance from the cliff edge. This tree buffer, which would be carefully planted to match the appearance of adjoining forested areas, would provide a root system to “take up” the rainfall before it reaches the Yorktown layer. A series of stakes have been installed near the edge of the Cliff Field to accurately measure future erosion. This study will add to Stratford’s knowledge of the cliffs and provide ways to improve our stewardship of this valuable natural resource.
Every geologist who wishes to acquire a knowledge of the tertiary formations of the United States, should visit the cliffs at Stratford.
– John Finch, geologist