Mission Valley Formation facts for kids
Quick facts for kids Mission Valley FormationStratigraphic range: Paleogene |
|
|---|---|
| Type | Geologic formation |
| Underlies | Pomerado Conglomerate |
| Overlies | Stadium Conglomerate |
| Thickness | 0–60 metres (0–197 ft) |
| Lithology | |
| Primary | sandstone |
| Location | |
| Region | San Diego County, California |
| Country | United States |
| Type section | |
| Named for | Mission Valley, San Diego |
The Mission Valley Formation is a type of sandstone rock layer found in the Mission Valley area of southwestern San Diego County in Southern California. It was formed a very long time ago in the ocean.
About the Mission Valley Formation
This rock layer is made mostly of sandstone. It is soft and crumbles easily. The color is a light olive gray. The sand grains that make up the rock are small to medium in size. These grains are mostly made of quartz (a common mineral) and potassium feldspar (another type of mineral).
The Mission Valley Formation is not the same thickness everywhere. It gets thinner as you go from the west to the east. At its thickest, it can be up to 0–60 metres (0–197 ft) deep.
Where It Is Found
This rock layer is part of a series of rock formations. It sits on top of the Stadium Conglomerate formation. This means the Stadium Conglomerate formed first, and then the Mission Valley Formation was laid down on top of it.
Above the Mission Valley Formation, you will find the Pomerado Conglomerate formation. So, the Pomerado Conglomerate formed after the Mission Valley Formation.
Ancient Life: Fossils
The rocks in the Mission Valley Formation hold fossils. These fossils are like clues from the past. They tell us about life that existed during the Paleogene period. This period was part of the Cenozoic Era, which began about 66 million years ago.
In the western and central parts of the formation, scientists have found fossils of mollusks. Mollusks are creatures like snails and clams. In the eastern parts, fossils of land mammals have been discovered. These fossils help us understand what animals lived in this area millions of years ago.
