Fruitland Formation

The Fruitland Formation is a sedimentary geological formation containing layers of sandstone, shale, and coal. It was laid down in marshy delta conditions, with poor drainage and frequent flooding, under a warm, humid and seasonal climate.

 

The Fruitland is underlain by the Pictured Cliffs Sandstone, and overlain by the more recent Kirtland Formation. The sequence of rocks represents the final filling of the Cretaceous seaway. The underlying Pictured Cliffs is a marginal marine sandstone, deposited in an environment similar to offshore barrier islands of the southeast United States. As the seaway retreated, the Pictured Cliffs was covered by the Fruitland Formation, which was deposited in near-shore swampy lowlands. The formation is dated to the late Campanian (part of the Cretaceous period), and was deposited over a period of about a million years. Radiometric dating from 23 meters above the base of the formation has yielded an age of 76.03 ± 0.41 Ma ago. An ash bed lying above the upper boundary with the Kirtland Formation has been dated to 75.02 ± 0.13 Ma ago. The underlying Pictured Cliffs Sandstone would be dated 76.94 - 76.27 Ma, based on the presence of the ammonite Baculites scotti, therefore placing the base of the Fruitland Formation at ~76.3 Ma.^[4]

The formation is subdivided into the upper Fossil Forrest Member (deposited between about 75.5-75 million years ago) and the lower Ne-nah-ne-zad Member (deposited from 76.3-75.5 million years ago). The Fossil Forrest member is considered to be part of the Hunter Wash, fauna shared with the overlying lower Kirtland Formation.^[1]

Ornithischians of the Fruitland Formation
Genus	Species	Member	Abundance	Notes	Images
Hadrosauridae indet.[5]	Intermediate[5]	Fossil Forest[5]	One print[5]	Giant hadrosaur track, indicating an individual larger than Shantungosaurus, the largest known hadrosaur.[5]
Parasaurolophus[6]	P. cyrtocristatus[6]	Fossil Forest[6]	A partial skull associated with a mostly complete postcranial skeleton, and a partial skull and fragmentary ribs of a juvenile individual.[6]	A lambeosaurine hadrosaurid also known from the Kaiparowits Formation.[6]
Pentaceratops[7]	P. sternbergii[7]	Fossil Forest[7]	[Two] nearly complete skulls and a nearly complete frill.[7]	A chasmosaurine ceratopsid also known from the Kirtland Formation.[7]
Stegoceras[8]	S. novomexicanum[8]	Fossil Forest[8]	Partial remains of [three] frontals and nearly complete frontoparietal.[8]	A basal pachycephalosaurid also known from the lower Kirtland Formation.[8]
Titanoceratops[9]	T. ouranos[9]		A partial skull, syncervical vertebrae, cervical vertebrae, dorsal vertebrae, sacral vertebrae, caudal vertebrae, ribs, humeri, radius, femora, tibiae, fibula, ilia, ischia, and ossified tendons.[9]	Possibly represents a junior synonym of Pentaceratops, holotype may possibly have come from the Kirtland Formation.[9]

Some remains (OMNH 10131) of Bistahieversor may actually have originated in the upper Fruitland Formation.^[10]

Saurischians of the Fruitland Formation
Genus	Species	Member	Abundance	Notes	Images
Bistahieversor[11]	B. sealeyi[11]	Fossil Forest[11]	A rostral ramus of a lacrimal, and a partial skull and postcranial skeleton of an adult individual.[11]	A eutyrannosaur tyrannosauroid also known from the Kirtland Formation.[11]
Dromaeosauridae[12]	Indeterminate[12]	Fossil Forest[12]	Numerous isolated teeth.[12]	Indeterminate dromaeosaurid remains.[12]
Ornithomimidae[12]	Indeterminate[12]	Fossil Forest[12]	Distal end of metatarsals, distal end of a phalanx, and foot-bone fragments.[12]	Indeterminate ornithomimid ornithomimosaur remains.[12]
cf. Ornithomimus[12]	cf. O edmontonicus[12]	Fossil Forest[12]	A manual ungual.[12]	Material possibly referable to Ornithomimus.[12]
?Troodontidae[13]	Indeterminate[13]	Fossil Forest[13]	Isolated teeth.[14]	Formerly identified as Paronychodon sp., referral to Troodontidae doubtful.[15]

 

The Fruitland Formation contains beds of bituminous coal that are mined in places along the outcrop. Original reserves of coal in the formation have been estimated at 200 billion tons.^[16]

Since the 1980s, the coal beds of the Fruitland Formation have yielded large quantities of coalbed methane. The productive area for coalbed methane straddles the Colorado-New Mexico state line, and is one of the most productive areas for coalbed methane in the United States. The methane released from the Fruitland Formation, through oil and gas production and a bit of natural seepage, contributes to the Four Corners Methane Hot Spot.^[17][18]

• List of stratigraphic units with dinosaur body fossils
• List of fossiliferous stratigraphic units in Colorado
• List of fossiliferous stratigraphic units in New Mexico