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A Very Old Story

Calvert Cliffs’ Miocene marine deposits are the largest in the world. But why?

I am going to test your patience and write about geology. This means you will be tempted to immediately turn to the News of the Weird. Please don’t.

Memorize the following sentence; it is your five-second speech on what makes Calvert County special: Calvert Cliffs contain the largest exposed Miocene marine deposits in the world. That, and a geological mystery.

The Miocene marine deposits that form the famous, fossil-laden, Calvert Cliffs are roughly 10 million years old. That’s relatively young in geological time. The sharks, whales, dolphins and all whose bones and teeth are, even now, falling out of those cliffs are much less ancient than the dinosaurs.

But why Calvert?

The ancient Miocene seas covered the coastal plain north and south of Calvert County, and the creatures that lived there left their bony parts behind. To the west, where Rt. 95 runs north to south, is approximately where the Miocene sea met dry land. Meaning that here, on the geophysical province called the coastal plain (including the Eastern Shore), there are marine fossils buried beneath the surface — or exposed, as they are along the Chesapeake shoreline in Calvert County.

The same sharks’ teeth our cliffs are famous for can be found in other sites, some of them far away, though elsewhere similar fossils are buried well below the surface or exposed in limited quantities. 

Again, why Calvert?

Why are there cliffs from Fairhaven in Southern Anne Arundel to an area just south of Cove Point in Calvert? Why not St. Mary’s?

St. Mary’s, like the Eastern Shore, is flat like Kansas. Calvert is elevated, with rolling hills and cliffs. A ridge runs in a meandering north-south line through the county. It reaches a height of about 180 feet near Sunderland and tapers down to about 100 near Solomons. In its wanderings, the ridge keeps to the east, closer to the Bay.

The creeks that drain to the Patuxent — such as St. Leonard, Lyons and Hunting — are longer than the few, such as Parkers and Fishing Creek, which flow into the Bay.

An interesting creek note pertains to Battle and Parkers creeks. It is believed these drainages were once connected. Battle Creek and its cypress swamp flows westward to the Patuxent. Parkers Creek, where a few stray cypresses also grow, flows its sluggish course into the Bay. On a map, the headwaters of each body seem to reach toward each other. But there is that darn ridge that gets in the way. 

The best I could come with is this from C.F. Stein’s History of Calvert County: “The terrain … is characterized by three levels, each marked by a terrace. These platforms and terraces represent three eras when the land sank below the levels of the waters then rose again.” I love how Stein summarizes millions of years of the geologic story in a sentence.

Sea levels rise and fall with global cooling and warming cycles. But what caused the land to lift? Is it rebounding from the weight of glaciers that covered regions north of here? Is it true that there is a geological fault that runs below the Patuxent? If so, does that help explain it?

If you are a geologist, now is the time to explain this geological puzzle. Please send an email to editor@bayweekly.com.

Everyone else may now turn to News of the Weird.

 

Places to visit

Bay Front Park, town of Chesapeake Beach, approximately one mile south of Mears Ave. off Rt. 261 in Chesapeake Beach.

Calvert Cliffs State Park in Lusby: www.dnr.state.md.us/publiclands/southern/calvertcliffs.asp