Vertebrate paleontology and Cenozoic depositional environments of Death Valley National Park, California, USA

Abstract

ABSTRACT The vertebrate paleontology, lithostratigraphies, and depositional environments of the Cenozoic continental Titus Canyon and Furnace Creek Formations have been the subjects of several recent investigations. The two units are exposed in the Amargosa Range in northeastern Death Valley National Park, Inyo County, southeastern California, USA. Fossil tracks and trackways are preserved in playa mudflat deposits of the Pliocene Furnace Creek Formation at the Cow Creek tracksite on the western slope of the central Funeral Mountains. The tracksite includes footprints of birds and land mammals, as well as associated sedimentary structures. The lower red beds of the Titus Canyon Formation have produced numerous fossilized bones and teeth at Titus and upper Titanothere Canyons in the southeastern half of the Grapevine Mountains. The fossil remains represent 17 extinct genera and species of land mammals and one genus and species of pond turtle. The taxa constitute the Titus Canyon Fauna. The rodents Quadratomus? gigans and Dolocylindrodon texanus, the bear dog Daphoenictis n. sp. (small), and the tapir Colodon stovalli are associated elsewhere only in the correlative, late early late Duchesnean Upper Porvenir Local Fauna of Trans-Pecos or Far West Texas. The local fauna occurs in the Blue Cliff Horizon (i.e., above lower marker bed) in the lower part of the Chambers Tuff Formation. The two assemblages share 12 species. The age of the latter unit is constrained by corrected single-crystal laser-fusion 40Ar/39Ar dates of 37.83 ± 0.09 Ma for the underlying Buckshot Ignimbrite and 37.14 ± 0.08 Ma for the overlying Bracks Rhyolite. However, both determinations should be considered tentative and subject to change with further investigation. The first green conglomerate unit of the Titus Canyon Formation overlies the lower red beds, underlies the Monarch Canyon Tuff Bed, and has produced the first records of land mammal footprints and a land plant (petrified palm wood) from the formation. The Monarch Canyon Tuff Bed and the Unit 38 Tuff Bed, which lies at the mutual tops of the upper “red beds” and the Titus Canyon Formation, are 34.7 ± 0.7 m.y. old and 30.4 ± 0.6 m.y. old, respectively, based on recalculated 40Ar/39Ar dates. Consequently, the Titus Canyon Formation is latest middle Eocene to earliest Oligocene in age, according to the 2020 Paleogene time scale.