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Geology, Paleontology and Archaeology

Geology and Paleontology

A remarkable display of Colorado’s geologic record can be seen at Ken-Caryl in the short six miles between the western border at Tincup and Beacon Hill and the eastern border at Kipling Parkway. Generally speaking, Ken-Caryl Ranch is divided in half by the north-south trending Hogback, with the western portion considered as the Valley, and the eastern portion as the Plains. The Hogback tells the story of geologic drama, played out over more than 600 million years.

ValleyRocksThe Front Range forms the western backdrop of the Ranch, marked by the sharp break in topography rising to Tincup and Beacon Hill. Tincup is the high peak west of the Manor House. Beacon Hill is the shoulder on the south side of Tincup. More than 600 million years ago the great mass of igneous granite was subjected to heat and pressure to become the metamorphic rock, gneiss, that today lies under the pinons and scrub oak. Quartz, small garnets, and pegmatite, among other minerals, are found in the gneiss which prompted local prospecting and mining during the late nineteenth century.

Some 300 to 500 million years ago the land began to sink, forming a shallow sea. The Front Range was the shoreline of this ancient sea. Sand, mud, the remains of shells and organic materials were deposited in horizontal layers over the bedrock and hardened into sedimentary rock. When the sinking stopped, the basement rock of granite gneiss began to uplift to form the Ancestral Rocky Mountains. The uplift lasted for 150 million years. The sedimentary layers were broken during the uplift and the edge exposed to the elements. The remnants are the red rocks of the Fountain Formation, the flanks of the Ancestral Rockies, which are locally prominent from Roxborough Park, through Ken-Caryl and South Valley Park, to Red Rocks Amphitheatre.

As the waters receded, deserts covered the region about 280 million years ago, the time of the supercontinent Pangaea. The Lyons Formation of calcite cemented sandstones can be considered as fossilized “sand dunes.” On the eastern slope of the Lyons Formation, in the narrow intermediate valley, are the eroded remains of the shale and limestone Lykins formation, created by the muds and calcium carbonate (lime) that were deposited when the sea returned and the area was a tidal flat. This corresponds to the period of the Permian-Triassic mass extinction event 252 million years ago. Scientists estimate that 90 percent of the marine life and 70 percent of terrestrial life died out. Possibly 10 million years passed before life on Earth recovered.

As Pangaea broke apart, the low coastal plain became a riparian paradise for dinosaurs during the time of the Morrison Formation of the late Jurassic period (145 to 165 million years ago). The Morrison Formation, named for the town of Morrison to the north of Ken-Caryl, is notable for the quantity of dinosaur fossils that have been found within its matrix. The great reptiles continued to roam this region for the next few million years until the seas again returned to form the beaches of the Dakota Sandstone, 100 million years ago. Evidence of the dinosaurs walking these ripple marked beaches can be seen along Alameda Parkway as it crosses the Hogback north of the Ranch. The ripple marked beaches and the dinosaur footprints and bones are preserved there in stone at Dinosaur Ridge National Historic site.

The narrow north-south valley, formed at the end of the old uplift period of the Ancient Rockies, lies between the Lyons Formation and the Dakota Hogback. The softer materials of the Lykins and Morrison formations eroded and the lower part of the valley was filled with alluvial materials of a relatively recent (Quarternary, or 2.6 million years ago to the present) age.

Alluvium filled the valleys, not only between the Lyons and Dakota Hogback, but between the Hogback and the granite mountains, and out east to the plains. Development is founded for the most part on alluvium of the Quaternary period, formed as erosion washed down materials from the uplifted west. Beneath the alluvium to the east, lay shale and coal deposits that were mined near Ken-Caryl in the twentieth century. Perhaps the most significant geologic feature of the eastern plains is the occurrence of swelling soils, which are clays that can swell when exposed to water. The force exerted is enough to cause major damage to roads and buildings. When turned on end, as is the case along the Hogback, the swelling soils are called “heaving bedrock,” and the swelling results in ridges. These ridges are evident along Highway C-470 and on Kipling Parkway in Ken-Caryl, imparting a roller-coaster ride on the drive.

The alluvial fans in the Valley are interrupted by a small ridge or outcrop of gneiss, located to the south of the residential development and west of Mann Reservoir. This was formed by a small wrinkle on the Ken-Caryl Fault that intruded through the sedimentary layers about 70 million years ago.

Archaeology

Ken-Caryl Ranch is located in an area rich in archaeological discovery. The Hogback through Jefferson and Douglas Counties provided numerous sites that were attractive to early man. The south and west facing rock outcrops of the Fountain and Lyons Formations captured the sun’s warmth and provided shelter, although these outcrops were probably too warm for comfort during the summer months. Quartz and granite were available for toolmaking. Wild plums and chokecherries lined the nearby creeks, which also attracted wildlife.

Archaeology2The Colorado Archaeological Society conducted 33 archaeological digs on Ken-Caryl Ranch, beginning in 1973. The South Valley Archeological District, Bradford House II, and Bradford House III sites are listed on the National Register of Historic Places. Bradford House II and III are rock shelters located in the North Ranch area. Five distinct periods of occupation were identified in Bradford House III, including two from the Archaic period and three of the Plains Woodland period. Bradford House II is a small rock shelter used for 4,500 years, from approximately 3000 BC to 1540 AD. The South Valley District consists of multiple sites, dating from about 3000 BC to 1000 AD.

The investigations uncovered artifacts such as pottery, projectile points and hide scrapers used by the people of the Archaic and Woodland period. The people were probably hunters and gatherers with little knowledge of farming, since no farming tools have been found. Archaeological sites found on the Ranch also yielded human burials. The Colorado Archaeological Society has published a volume on the investigations at Ken-Caryl Ranch, by Ann M. Johnson, available at the Jefferson County Public Library and the Ken-Caryl Ranch Historical Society archives.

Human occupation necessitated animals for food. Deer constituted the primary protein source. Evidence of butchered bison vertebra was exposed in the stream cut bank of Massey Draw on an alluvial terrace southwest of and adjacent to Massey Draw. Similar evidence delayed C-470 Highway construction for many months. Natives probably ran herds of bison through the narrow openings of the Hogback, then killed and butchered their prey. In addition to buffalo and small game, antelope and mountain sheep roamed the area.

On June 1, 2009 two Ken-Caryl boys, Jake Carstensen and Tyler Kellett stumbled across a mastodon mandible in Massey Draw that had been uncovered by flood waters. The Denver Museum of Nature & Science reported that it was the best example of a mastodon ever found in Colorado to date, the third such find in the state, and could be 50,000 to 150,000 years old. Further investigation uncovered a tusk as well. Both the mandible and tusk were donated to the Denver Museum of Nature & Science. The significance of the find was overshadowed by the major find at Snowmass Village on October 14, 2010.

Ken-Caryl Ranch