Download or read book The Pony Express basaltic ash: a stratigraphic marker in Lake Bonneville sediments, Utah written by Charles G. Oviatt and published by Utah Geological Survey. This book was released on 2013-12-31 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Pony Express basaltic ash is locally a useful stratigraphic marker in Lake Bonneville sediments in west-central Utah. The ash was erupted from a vent in the Sevier Desert basin soon after Lake Bonneville had transgressed high enough to flood into the basin about 24,000 years ago. The ash is found at or near the base of the Bonneville marl below altitudes of 1400m (4600 ft) in part of the Sevier Desert basin and the southernmost part of the Great Salt Lake basin. The chemical composition of the ash is similar to that of other basalts in the Sevier Desert. Possible source vents are in the Pahvant Butte area or a maar near Smelter Knolls.