San Marcial basin
December 20, 2021
Bureau geologists have been mapping the San Marcial basin for the past 5 years. This is the sparsely populated basin near Fort Craig, about 30 miles south of Socorro. Relatively little attention has been paid to the geology here until this mapping effort. Not unexpectedly, after tromping around and making many outcrop observations, we have learned a lot more about the geology in this part of New Mexico.
An ancillary "fruit of our labor" is the discovery of fossils in a few places in the basin. We took Gary Morgan, from the New Mexico Museum of Natural History and Science and an expert on ancient mammal fossils, out to these sites in early November. At the last site, as we were hiking back to the cars and dusk was deepening, Gary spotted a bone the size of a small tree trunk! The first photo shows Gary holding what he later determined to be a radius-ulna (forearm) bone of a humongous ancient camel.
The extinct camel is called Gigantocamelus. It was the size of a modern-day giraffe, with a long neck but having shorter, more robust legs. The second photo shows the bone in comparison to the radius-ulna in a modern llama. The Kansas Geological Survey has an artistic sketch of what the camel may have looked like on their website. Imagine such a huge beast galloping around New Mexico 2 million years ago!