The presence of marine fossils in areas away from the sea is a clue that the land was once under the ocean. Through careful observation of rock formations and fossil deposits, students can draw conclusions about the ancient history of the Petersburg area. This out-of-classroom learning activity should be facilitated at Lee Memorial Park, where students have a unique opportunity to view a fossil deposit dating to the Upper Miocene and Lower Pliocene periods.

Lieutenant Run is a small stream in Lee Park that has cut through rock strata that date as early as the Miocene period. At the central part of the Lieutenant Run exposure, two different rock units are exposed. The lower one, a fine shelly sand named the Eastover Formation, was deposited in late Miocene time between about 6.5 million and 9 million years ago. This formation contains marine fossils of over 200 different species, providing evidence that the sea reached as far inland as Petersburg at the time these strata were deposited. Among the fossils found in the Eastover Formation are a variety of mollusks, including swimming forms, bottom dwellers, shallow burrowers, and deep burrowers. While most of the species found at Lee Park are now extinct, careful observers can recreate the marine environment by looking at similar or related living species. This comparison shows that the Petersburg area was a shallow marine setting near the shoreline.

Immediately above the Eastover Formation is a second, later rock unit—the Yorktown Formation—that dates to the lower Pliocene period between about 3.5 million to 5.0 million years ago. Quartz pebbles along the contact between these two rock units and Pliocene period deposits in the eroded burrows of the Eastover Formation partially reveal a significant chapter in the geological history of the region. Sometime after the Eastover Formation was deposited, the sea regressed; almost 2 million years passed before marine deposits resumed. This drop in sea level also isolated and dried up the Mediterranean Sea at the same time.

Source: "Educator's Guide: On the Trail of History - Lee Memorial Park, Petersburg, Virginia."