Welcome Waco Mammoth National Monument

July 10, 2015 saw the addition of a new National Park Service unit, Waco Mammoth National Monument. It's the second recent NPS unit to be established for Pleistocene fossils, after Tule Springs Fossil Beds National Monument, and has been a long time germinating. I'll probably have a more detailed post within a few weeks, but here's a quick introduction. 

The Waco mammoth site was discovered along the Bosque River in the spring of 1978 by Paul Barron and Eddie Bufkin [tweaked the circumstances slightly; 2020-8-19]. They contacted Baylor University, which conducted a series of digs over the next two decades. The excavation site is compact, occupying about 5 acres. Bones of approximately two dozen Columbian mammoths have been found here to date, along with remains of tortoises, alligators, a saber-toothed cat, a camel, an antelope, and an undetermined mammal. Study of the sediments of the site and the stable isotopes of the bones (the stable isotopes of elements like carbon and oxygen can help show if a collection of animals were living in the same area or came from different places) indicate that there are at least three events recorded at the site: one mass death that claimed at least 19 mammoths and the camel, then an event that claimed the feline and the undetermined mammal, and most recently an event that killed a bull mammoth, an adult female mammoth, and a juvenile. It's a good bet that all three events are related to periodic flooding in the narrow channels of the river system. Mammoth bone has also been found in cores at a level below the major discoveries. The largest and oldest event occurred between 73,000 and 58,000 years ago, and the most recent about 15,000 years later. The group of 19 has been interpreted as a "nursery herd" of mothers and juveniles.

A view of part of the site as it was being excavated, borrowed from Chapter Two of the NPS's "Waco Mammoth Site: Special Resource Study/Environmental Assessment".

Mammoth bones in situ at the monument (photo Larry D. Moore CC BY-SA 3.0)

Flooding and runoff at the site prompted the university to remove 16 of the mammoths during the 1990s, which are now at the Mayburn Museum Complex (then the Strecker Museum) along with other bones. The museum complex has an exhibit of these bones. A protective shelter was built more recently at the site itself and allows visitors to see the bones of four mammoths and a camel in situ. Additional runoff occasionally brings more bones to light.

There's a lot of reading material out there, depending on your preference.
Non-technical includes:
The official NPS page for Waco Mammoth National Monument;
The official press release;
Baylor University's page on their exhibit;
The Waco History entry on the Waco Mammoth Site;
The City of Waco's page on the monument;
Moderately technical includes:
Waco Mammoth National Monument on Wikipedia;
Waco Mammoth Site entry for the National Fossil Day website;
The Special Resource Study for the site (NPS) (Chapter Two contains the paleontological details);
Technical includes:
George Naryshkin's 1981 thesis, "The significance of the Waco Mammoth Site to central Texas Pleistocene history";
John Bongino's 2007 thesis,"Late Quaternary history of the Waco Mammoth site: environmental reconstruction and interpreting the cause of death"