SAN JON CANYON
THIS LOCATION IS ON PRIVATE PROPERTY AND IS INACCESSIBLE TO THE PUBLIC
NEW MEXICO U.S.A
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.
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 10,000 - 15,000 years old, which puts strata in the late Pleistocene and the Holocene.
The Unnamed layers are Modern Playa (Temporary Lakes). They 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).
The Canyon was formed by seasonal river flows, flash floods from Monsoon thunderstorms during the summer will erode the sediment. This continuation of erosion over the seasons moves the sediment away and breaks the rocks into smaller clastic sediments.
The Formation of 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.
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 under the upper Bison Bone Bed and above the Bone Bed associated with the Mammoth bones which were found by Frank Hibben in 1940.
Upper Bison Bone Bed
Page 393 (137. San Jon)
Site Number LA/MNM site 6437
New Mexico Geological Society. Carlsbad Region (New Mexico and West Texas), Love, D. W.; Hawley, J. W.; Kues, B. S.; Austin, G. S.; Lucas, S. G.; [eds.], New Mexico Geological Society 44th Annual Fall Field Conference Guidebook, 357 p.
W. R. Osterkamp, Warren W. Wood. Playa-Lake Basins on the southern high plains of Texas and New Mexico: part 1. Hydrologic, Geomorphic, and Geologic evidence for their development. Playa-lake basins on the Southern High Plains of Texas and New Mexico: Part I. Hydrologic, geomorphic, and geologic evidence for their development. GSA Bulletin; 99 (2): 215–223.