Midwestern Mastodon Bonebeds: Death Traps and Salt Licks

Big mastodon sites have been getting a lot of press lately. In particular, the Snowmass site high up in the Colorado Rockies has produced over 30 mastodons over the course of two field seasons. This site–making national news on a regular basis over the last year–was a pond where the bones of mastodons, mammoths, bison, and ground sloths (to name a few) were found by the dozens. The Snowmastodon site (as it has been called) was featured on Nova a few weeks ago. Kirk Johnson (Denver Museum of Nature and Science) and Dan Fisher (University of Michigan) suggest that the high number of mastodon bones in debris flows are the result animals trapped on the sandy shores of the pond during earthquake liquefaction, and that humans may be partly responsible for a partially articulated mammoth in the upper levels. This is a fascinating site, and we’re looking forward to seeing what comes from the scientific investigations…which have only begun.

However, the Snowmastodon site puts in my mind a few other big mastodon bonebeds. The Boney Spring site in the western Ozarks was excavated by crews from the Universities of Arizona and Missouri, and the Illinois State Museum in the 1970s. The Ozark project explored a number of important paleontological and archaeological localities. Boney Spring itself was the latest of three major paleontological sites spanning the last ~150,000 years. In all, 31 mastodons were excavated from a single component of the site, dating to ~16,000 years ago. This assemblage includes animals of all ages and sexes, including a very large bull, who remains the largest North American mastodon on record. Although dominated by mastodons, the Boney Spring assemblage includes a minor number of other critters, including: 4 Paramylodon harlani (Ground Sloth), 2 giant beavers (Castoroides), horse, and tapir.  Although small mammals are well represented, no large carnivores were present in the assemblage. Long-time ISM curator Jeff Saunders suggested that this concentration of mastodons was the result of environmental conditions–specifically, a severe drought which caused dying mastodons to congregate around the only source of permanent water, Boney Spring.

Another big Midwestern mastodon site is the “Birthplace of American Vertebrate Paleontology” itself, Big Bone Lick, Kentucky. Located in north-central Kentucky near the Ohio River, BBL has been the site of paleontological investigations since the 1730s. By the early 19th century, Thomas Jefferson became interested in the locality, tasking William Clark (of Lewis and Clark fame) to collect fossils for him. Mastodons figured prominently in early collections from BBL. The locality was investigated periodically throughout the 19th century by paleontological notables, but became a research backwater by the early 1900s. In 1962, University of Nebraska paleontologist C. Bertrand Schultz returned to BBL for five field seasons, the first modern paleontological excavations to occur at the site. Schultz and his collaborators discovered that the BBL locality had a complex geological history. Mastodons and other Pleistocene fauna were recovered cheek-to-jowl with bison. But these bison were not the large-horned animals contemporaneous with Pleistocene megafauna, but rather short-horned late Holocene forms. Today, the locality is a state park with an on-site visitor center and full-sized Pleistocene dioramas.  Bones still erode out of the creek banks…