A MIOCENE CAMELID TRACKSITE IN THE MUDDY CREEK FORMATION NEAR MESQUITE, NEVADA

A recently discovered camel tracksite near Mesquite, Nevada occurs in the Mio-Pliocene Muddy Creek Formation. Forty, variously oriented, Lamaichnum tracks are exposed. Additional tracks are probably concealed by a soil crust that partially covers the track-bearing surface. The tracks are preserved as molds into an approximately 4-cm-thick limestone which is cracked and rapidly eroding away. On the basis of size and orientation of the tracks, we infer that these individuals are generally larger than their earlier Miocene counterparts and were passing through the area in the northward direction. We are using photogrammetry to study this tracksite, as well as to digitally capture and preserve its evanescent features.

The track-bearing layer is light gray, silty limestone. It is the only limestone interval we have observed within the Muddy Creek Formation in this area. While it is approximately 4 cm thick in the area where the camel tracks occur, it thickens to approximately 90 cm over a distance of several tens of meters. The thicker portion contains no conspicuous camel tracks, but it contains conspicuous stromatolite-like structures which we interpret to be vadose-zone, pedogenic structures that postdate the deposition of the limestone. The deposition of this limestone layer within an otherwise fluvial, siliciclastic landscape, records the presence of a groundwater-sourced small lake to which the camels were attracted as a water source. Silt-size particles are homogeneously distributed within the limestone, recording the deposition of eolian silt in this lake.