Ocean and Lake Beaches

Hundreds of thousands of miles of coastline border the salt- and freshwater bodies of the United States. Few beaches are strictly sand, even the famous Florida and California beaches, and some are quite rocky. Fossils can be found in such gravel and rock accumulations, if they have been derived, at least in part, from a sedimentary rock. The fossils are usually poorly preserved, but the collecting is pleasant.

As with river collecting, beach fossils are either waterworn pebbles or fresh specimens from cliff exposures cut by the water. Storms erode beaches, carrying away sand and leaving behind rocks containing a rich harvest of fossils. Winter freezes many northern lakes, and as the ice expands it pushes many feet up the shore, carrying with it rocks once firmly bedded in the bottom.

The coastline of America exposes few fossiliferous cliffs, whereas in England, fossils can be found most of the way around the island. A few isolated coastal cliffs from California into Washington have large exposures of Cretaceous and Tertiary marine fossils. Some California beaches have a few fossils, such as agatized clams and pieces of wood. East coast beaches from Maryland south may yield a stray bone, tooth, or shell. The best-known American location is along the Maryland coast, where large cliffs, rapidly eroding, have released thousands of superbly preserved Miocene shells and some shark teeth.

Little is found around the Gulf beaches except where dredging, particularly from Mississippi almost to the tip of Florida, has dipped into fossil beds lying near the surface .These are primarily Eocene and Miocene with typical shell, bone, and teeth fossils. So many fossil shark teeth are found on the beach at Venice, Florida, and for thirty miles on either side of Venice, that postcards proclaim Venice the shark-tooth capital of the world. During the tourist season it is common to see half a hundred fossil hunters, bent low to the beach, scurrying back and forth with the waves, waiting for shark teeth to appear. During rough weather, large pieces of bone are washed up —freed along with the shark teeth from a fossil bed in the floor of the Gulf.

A small area at the south edge of Tampa, Florida, used to be covered with agatized shells and pieces of coral of Miocene age until the fossil hunters and gem cutters discovered the beauty of these specimens. After the fossil bed was located only a few feet below the surface of the beach, hunters dug up most of the beach out to the low-tide line. Now few pieces remain to be washed up by the waves.

Lake Michigan beaches provide quartz-replaced corals of Devonian or Silurian age at almost any location on the south end of the lake. The

White Mound Fossils Oklahoma
A good collecting spot may be very small. This light-colored hill, barely 50 feet across, is the only exposure near Kebo, Oklahoma, of a Devonian limestone full of trilobite fossils. It is called White Mound.

Petoskey stone found near the Michigan town of that name along Lake Michigan and nearby lake shores is the calcite-replaced Devonian coral Hexagonaria. Similar corals are found on the other side of the lake in Door County, Wisconsin.

Lake Erie laps against many Devonian exposures along its eastern half, washing out brachiopods and corals. Canadian shores around Collings-wood, Ontario, are paved with Ordovician slabs crowded with trilobites. In one Ohio lake, boulders were found that turned out to be the stumps of petrified Devonian trees.

Many reservoirs and artificial lakes in the West and Southwest have provided access to fossil layers exposed in once-inaccessible river cliffs. There lapping waves concentrate fossils along the shoreline. Lake Texoma, on the Texas-Oklahoma frontier, is a favored spot to wade in the shallow water and feel out large ammonites with the toes. The spillway of Lake Benbrook in Texas is a bonanza of clams and echinoids after water is released, tearing loose many fossils. The spillway of one eastern Oklahoma artificial lake was cut into a layer of limestone composed primarily of crinoids and the blastoid Pentremites. Stock tanks in the Southwest are often dug into fossiliferous stone, where the waters clean and expose the fossils.

Ammonite Fossil Oklahoma
Calvert Cliffs, Maryland, a Miocene formation where shark teeth are collected. (Photo Maryland Geological Survey)
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Responses

  • vihtori
    What fossils found in benbrook lake?
    8 years ago
  • kerttu tapper
    What fossils can be found around lake texoma?
    1 month ago

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