The
bedrock of
Gloucester County, where Edelman Fossil Park is located, is composed of alternating layers of
sand,
silt, and
clay due to fluctuating sea levels since the Cretaceous. These sedimentary sequences are known as
facies. Sedimentary rocks of this area have been dated from between the Lower Cretaceous to the
Miocene (145 to 5.3 mya). The entire area of Southern New Jersey is known as the
coastal plain. It was submerged under a shallow sea until the late
Pliocene when the ocean receded as the
Greenland ice sheet formed 3 million years ago. The Coastal Plain begins on a southeast diagonal between
Carteret and
Trenton with sediments overlapping the rockier Piedmont Formation to the northwest. The specific layer in which the fossils are located is known as marl, a dark to light green, manganese-rich, clay that forms when algae, aquatic plants, and aquatic animals decay over a long period in hard-water streams rich in calcium carbonate. This layer is typically located in swamps, resulting in a covering of a dark organic-rich layer of peat. Because of marl's formation as the result of decaying plants and algae in soft sediment, it is a great harborer of fossils including numerous
invertebrates as well as larger land-dwelling animals whose bodies were swept downstream and laid here to rest. Within marl sediments is the
mineral vivianite (Fe2+3(PO4)2 · 8H2O) that forms as a result of
reduction-oxidation reactions. This deep blue to bluish-green crystal begins to oxidize in the presence of oxygen, converting Fe2+ to Fe3+ until the blue color becomes almost black and opaque. Because of this inevitable darkening, there is no such thing as stable vivianite. Embedded into these layers are also
schist dropstones, indicative of the ancient glaciations that occurred in this area during
glacial periods. “This is something that I personally and lots of other paleontologists have been looking for all around the world,” said the museum's executive director Dr.
Kenneth Lacovara, adding that he had sought such a layer in southern Patagonia, the foothills of the Himalayas and elsewhere. And I found it behind the
Lowe's in New Jersey,” he said. == Site history ==