Kirtland Formation Outcrops Near Coal Creek by Nick Longrich

The Kirtland Formation (originally the Kirtland Shale) is a

sedimentary Sedimentary rocks are types of rock formed by the cementation of sediments—i.e. particles made of minerals (geological detritus) or organic matter (biological detritus)—that have been accumulated or deposited at Earth's surface. Sedime ...

geological Geology (). is a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. Modern geology significantly overlaps all other Earth s ...

formation.

Description

The Kirtland Formation is the product of alluvial muds and overbank sand deposits from the many channels draining the coastal plain that existed on the inland seashore of

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

, in the late

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

period. It overlies the Fruitland Formation. It is found in the

San Juan Basin The San Juan Basin is a geologic structural basin located near the Four Corners region of the Southwestern United States. The basin covers 7,500 square miles and resides in northwestern New Mexico, southwestern Colorado, and parts of Utah a ...

in the states of

New Mexico New Mexico is a state in the Southwestern United States, Southwestern region of the United States. It is one of the Mountain States of the southern Rocky Mountains, sharing the Four Corners region with Utah, Colorado, and Arizona. It also ...

and

Colorado Colorado is a U.S. state, state in the Western United States. It is one of the Mountain states, sharing the Four Corners region with Arizona, New Mexico, and Utah. It is also bordered by Wyoming to the north, Nebraska to the northeast, Kansas ...

, in the

United States of America The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 states and a federal capital district, Washington, D.C. The 48 contiguo ...

. The base of the Kirtland Formation and its lowest sub-unit, the Hunter Wash member, has been dated to 75.02 ± 0.13 Ma. Together with the upper part of the underlying Fruitland Formation, this contains fossils representing the Hunter Wash local fauna. The border between the Hunter Wash member and overlying Farmington member dates to approximately 74 million years ago. The top of the Farmington member and bottom of the overlying De-na-zin member has been radiometrically dated to 73.83 ± 0.18 Ma ago. The top of the De-na-zin member, which contains the Willow Wash local fauna, has been dated to 73.49 ± 0.25 Ma ago. Overlying the De-na-zin member is a unit called the Naashoibito member This has often been considered to be part of the Kirtland formation, but more recently has been transferred back to the overlying

Ojo Alamo Formation The Ojo Alamo Formation is a geologic Formation (geology), formation in New Mexico spanning the Mesozoic/Cenozoic boundary. Non-avian dinosaur fossils have controversially been identified in beds of this formation dating from after the Cretaceous ...

, which it had originally been part of.

History of investigation

The formation was named by C.M. Bauer in 1916 for exposures near the Kirtland Post Office.

Stratigraphy

Vertebrate paleofauna

Saurischians

Ornithischians

Pterosaurs

Crurotarsans

Turtles

Bony fish

Cartilaginous fish

References

Bibliography

* * * * * * * * * * * * * * * * {{Chronostratigraphy of Colorado, Mesozoic state=expanded Cretaceous formations of New Mexico 01 Upper Cretaceous Series of North America Campanian Stage Sandstone formations of the United States Shale formations of the United States Mudstone formations of the United States Conglomerate formations Deltaic deposits Fluvial deposits