John Day Fossil Beds: When Mammals Rule

JODA 621: Mammal Fossil from the Order Rodentia

Thomas Condon was a missionary who learned about the John Day fossil beds in 1862 from soldiers who attended his church in Oregon. Three years later he ventured into the John Day basin and began excavating fossils. After obtaining verification from eastern museums that the fossils were authentic, he was appointed Oregon State Geologist and later professor of geology at the University of Oregon. Condon is credited with recognizing the importance of the fossil beds as a principal site for paleontological research. He also remained true to his faith and believed that science provided an avenue by which one could understand how God created all things.

JODA 14963: Hypsidoris oregonensis, Catfish

John Day Fossil Beds National Monument includes three locations, the Painted Hills, Clarno Unit, and Sheep Rock Unit as well as the Thomas Condon Paleontology Center. John Day provides a glimpse into the last 40+ million years of earth’s history, including one of the most extensive and best preserved plant and animal fossil assemblages in the world. These assemblages allow paleontologists to explore climate change, changes in landscape, plant and animal evolution, and the effects of catastrophic events on ecosystems during the Cenozoic Era. The Cenozoic represents the Age of Mammals or the time when mammals rule. This is a time when mammals become the larger, dominant terrestrial animals and increase in population size and diversity.

Today, central Oregon is dry and arid. However, 44 million years ago, during the time of the Clarno Nut Bed assemblage, we would have encountered a semitropical environment filled with dense forest and hundreds of plant and animal species. Plant enthusiasts would have marveled at the distant relatives of walnut, oak, magnolia and palm trees and perhaps encountered distant relatives of the tapir, crocodile, tortoise, catfish and a variety of insect species.

JODA 15869: Magnoliopsida, Petrified Wood

The Clarno Nut Bed assemblage has more species of fossil wood than any site and for any time period in the world.  Mammals like the three toed horse, Orohippus major, roamed the dense forest floor. This mammal was accompanied by the more ferocious Pristichampsus sp., the ancient relative of the modern crocodile. Pristichampsus sp. had heavy armor, serrated teeth, and long legs that allowed it to hunt terrestrial animals on land as well as along waterfronts.

About 33 million years ago Antarctica broke from Tasmania and South America. This break led to Antarctica being surrounded by the Antarctic circumpolar current, effectively shutting the continent off from warmer currents. Through time Antarctica became completely and permanently covered with ice sheets. The persistence of ice sheets on an entire continent effected the global climate. The climate of Oregon dropped three to six degrees Celsius during this period. The drop in climate temperatures led to more seasonal rainfall, a drier environment, and the formation of a temperate deciduous hardwood forest in eastern Oregon. The Bridge Creek Flora assemblage documents these changes. Its most prominent flora fossil, Metasequoia, is also the Oregon state fossil.

JODA 13512: Metasequoia Fossil

JODA 6451: Micropternodus cf. Fossil

JODA 1910: Unidentified Camelid Fossil

The climate continued to get drier and grasses spread across open habitats as evidenced in the Turtle Cove and John Day Assemblages. In the Turtle Cove Assemblage, a tiny relative of the mole, the Micropternodus morgana, roamed the floor and feed on worms and insects. Camels appear in the John Day Assemblage. A return to a predominantly temperate forest environment occurred during the Mascall Formation 15 million years ago. This environment suited the bone crushing dog Tephrocyon and the ancient horse Merychippus. The seven million year old Rattlesnake assemblage documents the transition from riparian woodlands and meadows to an environment similar to the John Day River Valley today. This included tall grasslands and semiarid wooded shrubland. This new terrain was well suited for horses, camels, burrowing animals, and the 12 foot tall distant bear relative Indarctos.

JODA 14135: Tephrocyon rurestros

JODA 14144: Merychippus sp. Fossil Astragalus Bone

JODA 15273: Indarctos oregonensis Fossil

In more recent times, Native Americans occupied the area. At Picture Gorge you will find ancient Native American pictographs depicting animals, humans, and an array of geometric designs. The paint for this art was made by combining red ochre with a binder consisting of eggs, blood, fat, or plant juice. The paint was then applied to the rock surface by finger. Fresh pigment was immediately absorbed into the pores of the rock, effectively staining the rock. As the rock weathers away, so do the pictographs. The weathering of rocks at Picture Gorge, however, is a very slow process and so it is estimated that some of its pictographs are several thousand years old. Visit the John Day Fossil Beds National Monument to learn more about climate change, geologic formations, and plant and animal evolution during the Cenozoic as well as the history of human occupation in the monument.

Reference:

http://www.nps.gov/JODA