Buttes are tall, flat-topped, steep-sided towers of rock. Buttes were created through the process of erosion, the gradual wearing away of earth by water, wind and ice.
Buttes were once part of flat, elevated areas of land known as mesas or plateaus. In fact, the only difference between a mesa and a butte is its size. Most geographers say a butte is taller than it is wide, while a mesa is a much larger, slightly less elevated feature.
Buttes are created as streams slowly cut through a mesa or plateau. The hard top layers of buttes, called caprock, resist weathering and erosion. As a result, the formations stay about the same height as the original plateau or mesa.
Weathering and erosion, most often by wind and rainwater, slowly erode the softer rock surrounding the caprock. Caprock protects the more vulnerable rock beneath it. Buttes slowly become slender spires.
Eventually, even the caprock falls prey to severe weathering and erosion. Debris that falls to the side of buttes is called scree or talus.
Above text about buttes is attributed to THE NATIONAL GEOGRAPHIC EDUCATION WEBPAGE.
At this location and the surrounding area of Northwest New Mexico and Southwest Colorado the following geologic features were created.
The Menefee Formation is the oldest exposed unit of the Mesa Verde Group within the main body of the canyon and shows an upwards transition from fluvial sandstone and shale to carbonaceous shale, coal, and interbedded sandstones as it approaches the contact with the Cliff House Formation. The Menefee Formation is visible in Chaco Canyon as a slope forming unit that underlies the steep mesa walls of the more resistant Cliff House Sandstone. It is especially prominent on the south side of the canyon, with a number of excellent exposures visible on Fajada Butte.
The Menefee Formation is interpreted to have been formed from sediments deposited on a deltaic coastal plain by rivers flowing north and east across New Mexico toward the retreating sea. At the edge of the sea, the streams meandered through a wide, flat, coastal plain with deltas, shallow swamps, and lagoons accumulating plant material which would eventually form thin coal beds.
Vertebrate fossils found regionally within the Menefee Formation include turtles, fish and crocodile as well as fragmentary evidence of larger creatures such as hadrosaur, ankylosaur, and ceratopsian dinosaurs and giant marine lizards known as mosasaurs. At Chaco, remains of a Cretaceous side neck turtle (Testudines pelomedusidae), a soft shell turtle (Trionychid), an unidentified hadrosaur dinosaur, and an unidentified theropod dinoasur have been recovered from the upper Menefee Formation.
Plant fossils found in the Menefee include leaf impressions of palm and conifer as well as specimens closely resembling modern laurel, witchhazel and camellia, suggesting a warm, moist, subtropical environment. At Chaco, plant fossil specimens are predominantly conifer with occasional broad leaf angiosperms and palm leaf impressions.
On top of the Menefee formation is the Cliff House Sandstone. The Cliff House Sandstone is a transgressive sequence of marine sandstones which overlies the Menefee Formation. The three principle Cliff House units (Lower, Intermediate, and Upper) visible in Chaco Canyon represent the beach, near shore marine, and offshore marine deposits produced near a barrier island beach front by repeated incursions of the Western Interior Seaway.
The Lower Sandstone unit, a massive marine sandstone, forms the 80 - 100 foot prominent cliffs visible throughout the canyon. This sandstone was deposited just off of a Late Cretaceous beach, in relatively shallow water still affected by wave and storm action. An abundance of ripple marks are visible in this unit. Fossils include shells and casts from clams, ammonites (including possible Placenticeras) snails, and shark's teeth. Iron-cemented, knobby casts of burrows known as Ophiomorpha ("serpent shape") Nodosa ("nodular") are particularly abundant. These casts are thought to be the fossilized remains of burrows left by a small shrimp-like crustacean known as Callianasa.
Immediately above the Lower Sandstone unit is the Intermediate unit. Although primarily a shallow water marine sandstone, it has locally interbedded shales which were deposited in deeper water. This unit is less resistant to erosion than the Lower Sandstone and forms gentle slopes rather than cliffs. Fossils found in this unit are generally similar to that of the Lower Sandstone but Ophiomorpha burrows are often less abundant and accumulations of the large clam Inoceramus are often more abundant.
The uppermost unit exposed in the main body of Chaco Canyon is the Upper Sandstone unit. It is similar in composition to the Lower Sandstone and also forms steep cliffs, but is generally only 30-60 feet in thickness. This unit represents a beach and barrier island environment and was deposited in shallower water than the Intermediate unit which reflects a lowering of local sea level as the Western Interior Seaway receded for a period of time. Fossils found in this unit include abundant invertebrate shells and shark teeth, and bone debris probably from marine lizards.
The above information about the Menefee Formation and Cliff House Sandstone is cited and attributed to the National Park Service Webpages on Chaco Culture National Historical Park.
To log this EarthCache please EMAIL me the answers to the following questions with the GC number and name of the cache and the names of the people in your party to receive credit. We reserve the right to delete your log for failing to fulfill the requirements below:
1) About almost halfway up from the bottom is a thin black band, what is it made of? How do you think this layer was formed and of what material?
2) Above this band the formation is called? And is made up of primarily what?
3) Below this band the formation is called? And is made up of primarily what?
4) Fajada means "banded". How many distinctive bands do you see? Do the Cliff House Sandstone bands vary in thickness? What do you think caused this variance to occur?
5) What is the name of the waterbody that covered this area? Why do you think the sea level varied?
6) Please post a picture of you with your GPS and the Butte in the background on your log.
Info for answering the questions is available at the coordinates of the cache, on the cache page and personal observations.
Permission for this Earthcache was granted by the Chaco Culture Park Supervisory Ranger.
Congrats to kurtbec for the FTF!!!