What type of rock is Mancos Shale?
Mancos shale. Dark-gray or lead-colored shales, nearly always somewhat sandy. Contains thin calcareous layers which in places become almost limestones and are usually rich in fossils. Sand locally increases to form sandstone, but no limestone or sandstone layer is persistent and prominent enough to be traced far.
When was the Mancos shale deposited?
95 million years ago
The Mancos was deposited during the Cenomanian (locally Albian) through Campanian ages, approximately from 95 million years ago (Ma) to 80 Ma.
What is an approximate age for the Mancos Shale?
The Mancos was deposited during the Cenomanian through Campanian Age (geology) approximately from 95 Ma to 80 Ma. The Mancos Shale was first described by Cross and Purington in 1899 and was named for exposures near the town of Mancos, Colorado.
Which region in Colorado is known to geologists as having the best land in the world for learning about the Earth’s history?
The Grand Valley
The Grand Valley has a rich geologic history that includes 225 million years of life preserved within the various rock layers that make up the area.
What is the size of the clastic grains within the Mancos shale?
In the Gigapan image location, the Mancos shale is dark gray. -Sandstone grains are coarser than shale. Grains are typically about 2 to 4 mm.
How was the Dakota Formation formed?
This marine transgression of the ocean onto what was formerly land, was completed by the late Albian (~100 MA) thereby dividing North America in half. On the eastern side of the Seaway, sediments that would become the Dakota Formation were deposited as coastal and nearshore marine sands and silts.
How was the Dakota formation formed?
How did the alcove caves at Mesa Verde form?
Pieces of sandstone, created during the formation of alcoves, were shaped and used by the Ancestral Pueblo people to construct their homes. Water seeps from the cliff face and forms a pool on the alcove floor. Alcove formation is assisted by water that is absorbed into and percolates through pores in the sandstone.
When was the Pierre Shale unit deposited?
70-80 million years ago
Pierre Shale It was deposited during the Campanian and Maastrichtian (~70-80 million years ago). This unit consists of dark gray/black shales that were deposited in deep marine waters. Within the shale unit are several distinct ash layers (bentonites), which have been used to help date the formation.
Did Colorado used to be underwater?
A hundred million years ago, instead of the ridge and foothills that are there now, the area was a flat sandy beach with rivers flowing into the ocean. At one, about 92 million years ago, everything in Colorado was underwater.
What is special about the Colorado Plateau?
The plateau is dominated by high mountains that are gashed by river canyons or scarred with dry gullies and washes and the beds of intermittent streams. Other topographic features include great shallow basins, sunken deserts, picturesque buttes and mesas, and rare verdant sections of valley.
How are alcoves formed?
Alcoves form where chemical and physical weathering is concentrated along horizontal discontinuities where water and salts concentrate, such as the contact between a sandstone and an underlying shale bed. In the case of layered sandstones, an alcove may later be enlarged by exfoliation of upper layers.
What is the sharp tongue of Mancos Shale?
Thin tongues of Mancos Shale separate the Corcoran from the underlying Sego Sandstone and overlying Cozzette Member (Young, 1955; Gill and Hail, 1975). Its contact with the underlying shale tongue is gradational, and its contact with the overlying shale tongue is sharp.
Where are the Mancos Shale and Mesaverde Group?
Stratigraphy of the Upper Cretaceous Mancos Shale (Upper Part) and Mesaverde Group in the Southern Part of the Uinta and Piceance Basins, Utah and Colorado Chapter 12 Stratigraphy of the Upper Cretaceous Mancos Shale (Upper Part) and Mesaverde Group in the Southern Part of the Uinta and Piceance Basins, Utah and Colorado
What are the stratigraphic relations between the Neslen formation and coastal plain?
Significant stratigraphic relations are described in the following: 1. The Neslen Formation is interpreted to be dominated by coal-bearing coastal plain deposits and estuarine complexes based on Franczyk and others (1990), Lawton (1983), and Kirschbaum and Hettinger (1998).
Where are the coeval strata in the Price River and Farrer formations?
Coeval strata in the Price River and Farrer Formations extend over the Bluecastle Tongue of the Castlegate Sandstone and the Neslen Formation between Price Canyon (loc. 1) and the Colorado-Utah border (near loc. 20). Correlations are based on the measured sections of Lawton (1983) and Franczyk and others (1990). 2.