Geology Question - type of formation

[CRL]

Does anyone know what type of rock strata formation this is? Location in SE Arizona. I know it’s volcanic ash layers that have been eroded, but the name escapes me. Thanks.

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[wazzou]

Basalt?

[Jbub]

Tuff

[Jbub]

If you know the exact location there is this map to help identify what you're looking for.

http://data.azgs.az.gov/geologic-map-of-arizona/#

Just click on the location and it will tell you what type of formation it is.

[CRL]

If you know the exact location there is this map to help identify what you're looking for.

http://data.azgs.az.gov/geologic-map-of-arizona/#

Just click on the location and it will tell you what type of formation it is.

Thanks for the map, which says: Moderately to strongly consolidated conglomerate and sandstone deposited in basins during and after late Tertiary faulting. Includes lesser amounts of mudstone, siltstone, limestone, and gypsum. These deposits are generally light gray or tan. They commonly form high rounded hills and ridges in modern basins, and locally form prominent bluffs. Deposits of this unit are widely exposed in the dissected basins of southeastern and central Arizona.

Basically, I guess, random crap and sandstone.

[peteski]

Thanks for the map, which says: Moderately to strongly consolidated conglomerate and sandstone deposited in basins during and after late Tertiary faulting. Includes lesser amounts of mudstone, siltstone, limestone, and gypsum. These deposits are generally light gray or tan. They commonly form high rounded hills and ridges in modern basins, and locally form prominent bluffs. Deposits of this unit are widely exposed in the dissected basins of southeastern and central Arizona.

Basically, I guess, random crap and sandstone.

Sounds like an ancient ocean floor material.

[Chris333]

This guy has some good stuff that might help:

[CRL]

Sounds like an ancient ocean floor material.

You’re probably correct... really ancient. The mustard color shows the volcanic tuff areas at higher elevations nearby. One of the interesting things of this area is the strata appear to be relatively level. Almost perfect for modeling.

[Philip H]

SE Arizona is definitely relict ocean bottom.

[Jbub]

I can't remember what National Parks visitor center it was in but the display showed a timeline that had the whole southwest as ocean bottom at least a couple of times in ancient history. It was either Grand Canyon, Arches, Bryce Canyon or Canyonlands.

[sirenwerks]

You’re probably correct... really ancient. The mustard color shows the volcanic tuff areas at higher elevations nearby. One of the interesting things of this area is the strata appear to be relatively level. Almost perfect for modeling.

More like lahar deposits, I think. Lahars are the mud and debris flows that come after the initial release, and build with local water sources. Basically, natures cement mixer.

[Vince P]

Interesting learned something new today just thought it was Basalt.

[CRL]

More like lahar deposits, I think. Lahars are the mud and debris flows that come after the initial release, and build with local water sources. Basically, natures cement mixer.

Except you need a substantial snow cap to melt and release the water that forms the lahar. I doubt the southwest had sufficient snow to support this... unless eruption occurred during one of the ice ages.