Scenes From The Bone-Bearing Badlands

Fossil Bone Basin, Mojave Desert, California

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Here is a distinctive and well exposed geologic section of the middle Miocene Barstow Formation at Fossil Bone Basin. Massive greenish to brown fluviatile (deposited in ancient streams and rivers) sandstones underlie the world-famous white "Skyline Tuff," appropriately enough situated at the skyline--a hardened layer of solidified volcanic ash that erupted from a long-vanished volcano some 15 million years ago. Strata deposited just below the Skyline Tuff (some 15.2 million years) to a point several hundred feet above it (15 to 13.4 million years old) yield the most abundant fossil vertebrate material recovered from the Barstow Formation--a fantastic array of mammals, including camels, horses, pronhorns, oreodonts, gomtherium proboscideans, saber-tooth cats, canids, and numerous varieties of rodents, among many others. It is certainly one of the most fossiliferous bone-bearing, terrestrial geologic rock units in North America--the type locality for the Barstovian Stage of the Miocene Epoch--roughly 16 to 12.5 million years ago.

Here is one of many world-renowned, now abandoned quarries vertebrate paleontologists worked for decades (probably from the 1930s to 1960s) in strata just below the white to pale-brown Skyline Tuff (seen along the skyline in the first image) in the middle Miocene Barstow Formation. Bones recovered here are somewhere around 15.2 million years old. Note the red backpack slightly above center for scale.

A view roughly westward along the world-renowned whitish layer of Skyline Tuff (seen in first and second images)--it's around 15 million years old. Above the Skyline Tuff lies the Upper Member of the middle Miocene Barstow Formation, within which occurs one of the great concentrations of terrestrial vertebrate fossils yet recovered from the middle Miocene of North America.

A seeker of Miocene paleontology--my late father--stands in Fossil Bone Basin; sedimentary strata directly behind disclosed numerous perfectly preserved horse teeth weathering out on the surface. This is the highly fossiliferous Upper Member of the middle Miocene Barstow Formation.

All strata included in this view belong to the (youngest) Upper Member of the middle Miocene Barstow Formation, here roughly 15 to 13.4 million years ancient. Sedimentary constituents include greenish to brown tuffaceous mudstones and claystones deposited primarily in ancient lakes; bones occur quite regularly here, distributed as weathered-free isolated skeletal elements and, less frequently, fully articulated skeletons of many varieties of extinct mammals.

Typical tuffaceous mudstones and claystones of the youngest phases of the middle Miocene Barstow Formation, Fossil Bone Basin, Mojave Desert, California. During my last visit here, I spotted several excellently preserved vertebrate fossils weathering free from the sedimentary rocks--including a number of pronghorn foot bones, a camel astragalus, and several phalanges from extinct three-toed horses.

Rather plentiful plant life sometimes finds a foothold in the dry washes that penetrate the Upper Member of the middle Miocene Barstow Formation, Fossil Bone Basin, Mojave Desert, California. Strata here produce significant concentrations of 15 to 13.4 million year-old mammalian remains.

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