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SAN JON CANYON

WHEATLAND - NEW MEXICO, USA

JAN 20th 2020 | UPDATED AUG 10th 2021

THIS LOCATION IS ON PRIVATE PROPERTY AND IS INACCESSIBLE TO THE PUBLIC

GEOLOGY

San Jon Canyon is located in the Pecos Valley section of the Great Plains of New Mexico, the area is relatively flat till the edge of the plains. The Ogallala Formation caps the plains to the East and forms the Mescalero escarpment which is the Eastern boundary of the Pecos Valley further south. 

The Ogallala Formation was deposited during the late Tertiary, Miocene to Pliocene (23-5 million years old). It's a combination of thick eolian and Fluvial deposits (Sand, Silt, Clay with local gravel deposits). The caprock of the formation is comprised of calcrete zones. The Pecos River has eroded the overlying Ogallala Formation from the base of the Sangre De Cristo Mountains. Layers of the Ogallala Formation do exist under the exposed rock layers in the San Jon Canyon but are not visible, as the area is higher than where the formation was deposited.

  

The Western boundary of the Pecos Valley is defined by discontinues mountain ranges, the underlying rock of the plains is mostly Paleozoic limestone (542 - 251 million years old) which is why there are so many caves and sinkholes in the area. 

San Jon Canyon New Mexico

Modern Playa

Most of the layers located in the canyon are too young to be named and thus remain nameless. The age these layers are dated to is around 15,000 - 13,000 years old, which puts strata in the late Pleistocene. The Unnamed layers are Modern Playa (Temporary Lakes), the older lake basin that formed part of San Jon canyon was around 1 kilometre wide with lacustrine sediments building up the canyon walls visible today while the younger basin was much smaller and formed the newer layers towards the top of the canyon. These temporary lakes are formed by depressions in the High Plains region, which periodically fill with water after spring storms and summer monsoons. 

Saltwater Playas also form in the Great Plains but are filled by water supplied by underground Aquifers. The salt moves up through the soil and dissolves into the water, then when the water evaporates the salt is left behind. The depressions are formed in several different ways. The most widely accepted theories are that they are formed by wind, areas with poorly developed Fluvial drainage systems, underlined by unsaturated clastic/calcrete systems or ground subsidence (sink Holes). 

San Jon Canyon New Mexico
San Jon Canyon New Mexico
San Jon Canyon New Mexico

Formation

The Canyon was formed by seasonal river flows, flash floods from Monsoon thunderstorms during the summer, this will erode the sediment away. The continuation of erosion over the seasons moves the sediment away and breaks the formation into smaller clastic sediments. Canyons like this is also associated with Mass Wasting also known as Landslides, rocks are dislodged from the canyon rims and fall down the slope to the canyon floor and later get washed away with the summer monsoons. 

San Jon Canyon New Mexico
San Jon Canyon New Mexico
San Jon Canyon New Mexico
San Jon Canyon New Mexico
San Jon Canyon New Mexico
San Jon Canyon New Mexico

Fossils

Vertebrate Fossils found in San Jon Canyon:

Bison Antiquus & Mammuthus Columbi

Bison Antiquus was a large and prevalent herbivore that once roamed the Great Plains of the American Continent, they were most common over 10,000 years ago. Modern Bison are direct decedents of the extinct Ancient Bison.  

 

Vertebrate Fossils are found in two separate layers in the late Pleistocene age, Bison and Mammoth fossils are the only types that have been found in the canyon. Paleoindian artifacts have also been found and age dated to 12,510 - 11,450 using radiocarbon to date, these artifacts are located under the upper Bison Bone Bed and above the Bone Bed associated with the Mammoth bones which were found by Frank Hibben in 1940.

San Jon Canyon New Mexico Bison Antiquus Fossil

Upper Bison Bone Bed

REFEreNCES

Spencer G. Lucas. (2015). Vertebrate Paleontology in New Mexico: Bulletin 68. New Mexico Museum of Natural History and Science.

 

John W. Hawley. (1993). The Ogallala and Gatuna Formations in the southeastern New Mexico region: A progress report. New Mexico Geological Society Guidebook, 44th Field Conference, 261–269.

Donald E. Trimble. (1980). The Geologic Story of the Great Plains Geological Servey Bulletin 1493. United States Geologiccal Survey.)

Bison antiquus (Ancient bison). (n.d.). Prehistoric Fauna, Roman Uchytel. Retrieved August 10, 2021.

 

US EPA. (2021, May 7). Playa Lakes. United States Environmental Protection Agency. 

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