Paleontology at Lake Mead National Recreation Area

Article by Aubrey Bonde
for Park Paleontology Newsletter, Spring 2018

Lake Mead overlooking Hemenway Harbor

NPS/Andrew Cattoir

Lake Mead National Recreation Area is located 30 miles east of Las Vegas, and serves as a welcome respite in the blazing heat of the Mojave Desert summers. Recreational opportunities at Lake Mead and Lake Mohave, such as boating, fishing, kayaking, and hiking, have propelled the park to rank among the top ten most highly visited of all NPS units. At the forefront of the park's conservational efforts are resource protection and education to visitors about the park’s desert wildlife, native fish and invasive species, and cultural history - far lesser known has been the park’s long and important paleontological story.

Fossil resources have been sporadically reported from the area since 1857 with the J.C. Ives expedition to survey the Colorado River corridor. The geology around the Lake Mead region has been well documented by researchers, and this has included occasional pulses of activity to collect paleontological resources as well. Lake Mead National Recreation Area now houses a small collection of fossils discovered by various researchers over the course of the last 150 years. In late 2016 through summer 2017, I was brought on through the Geoscientists-in-the-Parks Program (GIP) to help compile the paleontology story of Lake Mead. My role was to inventory museum collections, conduct field work, monitor known paleo localities, record new localities, and assemble the park's Paleontological Resources Inventory Report.

It is clear now that the paleontological record of Lake Mead is significant and expansive. This record includes fossils from the mid-Cambrian through the Early Jurassic and the latest Oligocene through Holocene, with few breaks in the geological record from those time frames. Fossils have been recovered from across the entire extent of this nearly 1.5 million acre park. Lake Mead National Recreation Area's paleo story begins roughly 515 million years ago with oceanic cover that blanketed the area for over 200 million years; this also preserved a diverse record of marine life such as trilobites (including a holotype species), corals, brachiopods (including a potentially new species), bivalves, gastropods (including a potentially new species), cephalopods, crinoids, bryozoans, and fish, to name a few. Roughly 315 million years ago, oceans receded and cycled between shallow marine and coastal environments for nearly 100 million years. Fossils in Lake Mead's collections provide evidence of this transition through marine taxa and terrestrial taxa, the latter including amphibians, early reptiles, and an abundance of petrified wood which likely represents stands of sub-tropical conifers.

Late Triassic petrified logs at Lake Mead National Recreation Area.

NPS/Aubrey Bonde

After this time, terrestrial environments aridified into the Jurassic (180 million years ago) and the Lake Mead area experienced a geologic hiatus until the late-Oligocene (26 million years ago). From 26 million years ago through the Holocene, the terrestrial record is quite complete with fossil evidence of many different forms of birds, reptiles, amphibians, and mammals.

Miocene bird track at Lake Mead National Recreation Area

NPS/Aubrey Bonde

There is still the need for much more research to be conducted at the park which would undoubtedly yield important fossil discoveries. However, today we now have a much better understanding of the paleontological history of Lake Mead National Recreation Area, which also lets us link the fossil resources of this park and their scientific significance to other NPS units from the Southwest. This broader geographic framework provides a more comprehensive view into the fossil record for the area encompassing and surrounding Lake Mead National Recreation Area.