ABSTRACT

The De Queen Formation of the Trinity Group (Lower Cretaceous) crops out in southwestern Arkansas and southeastern Oklahoma. The outcrop, located in the Highland Gypsum Quarry of Pike County, southwestern Arkansas, is described in detail in this paper and presented as a reference locality. Data from the locality provide the basis for a nomenclatural change from the De Queen Limestone Member to the De Queen Formation. The formation consists of 64.23% clastic sediments, 24.72% gypsum, and 11.05% limestone. Hopper-shaped salt casts, ripple marks, scattered pyrite and marcasite nodules, celestite, and chickenwire gypsum can also be found. The De Queen Formation is underlain by clays and the Ultima Thule gravel lentil, while the top is unconformably overlain by Upper Cretaceous Tokio gravels.

The depositional sequence of the De Queen Formation represents environments ranging from subtidal to lagoonal with water salinities ranging from brackish to hypersaline.