A U/Pb age for the Mygatt-Moore Quarry, Upper Jurassic Morrison Formation, Mesa County, Colorado
Journal Title: Volumina Jurassica - Year 2014, Vol 12, Issue 2
Abstract
Mygatt-Moore Quarry in the Brushy Basin Member of the Upper Jurassic Morrison Formation is one of the more important large dinosaur quarries in the formation, yielding fossils of sauropod dinosaurs including [i]Apatosaurus[/i], [i]Camarasaurus[/i], and an indeterminate diplodocine (cf. [i]Diplodocus [/i]or [i]Barosaurus[/i]), the theropod dinosaurs [i]Allosaurus [/i]and [i]Ceratosaurus[/i], and the ornithischians [i]Othnielosaurus [/i]and [i]Mymoorapelta[/i]. Fossil wood and carbonized plants are known from the deposit, and carbonized dinosaur skin has also been discovered.We report here on a new U/Pb radiometric age for the Mygatt-Moore Quarry, from a smectitic mudstone collected at the quarry horizon. We isolated zircons using an ultrasonic separation technique and standard heavy liquid and magnetic methods, analyzed single zircons using a chemical abrasion method (CA-TIMS). The age determined for this dinosaur quarry, 152.18 ±0.29 Ma, places the quarry at the boundary between the Kimmeridgian and Tithonian stages of the Late Jurassic Period. This age can now be used to place the quarry into stratigraphic position with respect to other dated horizons in the Morrison Formation and other rock units worldwide. We will also use this age along with other ages to create a radiometrically based stratigraphic framework for the Morrison Formation.
Authors and Affiliations
Kelli C. TRUJILLO, John R. FOSTER, ReBecca K. HUNT-FOSTER, Kevin R. CHAMBERLAIN
Keywords
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