Diggin' For Dinosaurs - Fossil Butte

Fossil Butte National Monument, Wyoming

A ridge at Fossil Butte National Monument offers an endless view of high sagebrush desert with little hint of water but for a few aspens lining a shallow draw. Dust that rises with each footprint leaves no doubt that this Wyoming landscape is - what else? - bone dry.

A few delicate taps of a hammer against metal wedges between layers of rock pry loose a flat plate of stone that slides back as easily as cutting a deck of cards. Beneath the rocky shroud, exposed for the first time in 50 million years, lies the perfectly preserved skeleton of a fish that swam in the warm, shallow waters of Fossil Lake. Had you been standing here back then, you would have seen a palm-fringed tropical lake teeming with fish, stingrays, alligators, and crocodiles, and strange shorebirds with the body of a flamingo and the head of a duck - descendants of the dinosaurs who last roamed this region 15 million years ago. Fossil Butte, 10 miles west of Kemmerer on U.S. Highway 30, preserves a slice of that ancient ecosystem in a landscape that now could not be more different.

When the residents of Fossil Lake died, many sank to the bottom. Sediments covered them with a kind of geological security blanket that later hardened into stone and remained buried until the land rose and erosion sliced into southwestern Wyoming to reveal what is left of Fossil Lake. Its remnants lie in what is known as the Green River Formation, a creamy, white layer cake of mudstone, limestone, and volcanic ash that crowns most of the modest buttes and ridges in this fossil-filled landscape.

Crews building the transcontinental railroad in the late 1860s stumbled into the first major deposits of fossil fish, sparking the interest of scientists and professional collectors who soon came to dig into the past ecosystem of Fossil Lake and two other ancient lakes, Gosiute and Uinta. The monument's 2.5-mile Historic Quarry Trail leads past a former commercial quarry, quiet now except for the rustling of sagebrush, where you can see the layers of rock hiding ancient treasures. Digging for other than research purposes is now prohibited in the monument but continues at private and state quarries nearby.

To see highlights of past excavations, head for the monument's museum-class visitor center. Set into a chalky hillside, the unimposing building is filled with wonders. A fossil alligator, still lying in its bed of stone, reaches practically from floor to ceiling and is accompanied by its ancient relatives, all set off with subtle but graceful lighting. You can almost imagine yourself floating within Fossil Lake back when it swarmed with life. In a glassed-in laboratory, monument staff extract other fossils encased in their rocky tombs.

On summer weekends, the hunt for pieces of the past continues on guided hikes to a research quarry within the monument. There, under the supervision of palaeontologists, the tools come out and visitors can try their hand at peeling apart layers of rock like phyllo pastry to see what dwells underneath. Sometimes the amateur diggers may find coprolites (fossilized dung), but frequently they also come upon fish or palm fronds that look as though they had fallen into the sand only yesterday.

Continued in: Diggin' For Dinosaurs - Wyoming Dinosaur Center

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