September 19, 2016:

A new mass death assemblage in Lower Cretaceous strata of east-central Utah contains well-preserved skeletons representing an ontogenetic series of individuals of Utahraptor, and at minimum two iguanodont grade ornithischian skeletons. The dinosaurs were entombed in ovoid-lensoidal, fine-grained sandstone sills linked by sandstone pipes and/or dikes and another basal lensoidal mass with scattered and broken iguanodont and sauropod bones and to an underlying gravelly sandstone bed. Exposed in the excavation high-walls are syndepositional normal-faults bounding graded ripple strata. Multiphased fluid over-pressurization in an artesian setting creating the structures. Trapping, killing, and subsequent burial mechanism was generated by variations of pressure in a localized artesian spring system that breached the surface and is the first such mechanism documented with numerous dinosaur victims.

James I. Kirkland, Edward L. Simpson, Donald D. DeBlieux, Scott K. Madsen, Emily Bogner & Neil E. Tibert (2016)
Depositional constraints on the Lower Cretaceous Stikes Quarry dinosaur site: Upper Yellow Cat Member, Cedar Mountain Formation, Utah.
Palaios 31(9): 421-439
DOI: 10.2110/palo.2016.041