A Gap in the Geologic Record

A Gap in the Geologic Record (HM1AZN)

Location: Petrified Forest National Park, AZ 86028 Apache County
Buy Arizona State flags at Flagstore.com!
Country: United States of America
Buy United States of America flags at Flagstore.com!

N 35° 4.14', W 109° 47.677'

  • 0 check ins
  • 0 favorites
The black basalt that caps the cliffs before you stands in stark contrast to the colorful Chinle Formation visible throughout the Painted Desert.

Below this layer of basalt, a horizontal line cuts across the face of the mesa and separates rocks of two different geologic periods. The pink mudstone below this line belongs to the Chinle Formation deposited about 225 million years ago. The brown mudstone and basalt layers above the line represent the Bidahochi Formation deposited only 5 to 8 million years ago.

How is it that only this thin line represents more than 200 million years of geologic history? This gap is known as an "unconformity." Geologists believe the missing layers were more than 1,000 feet (305 m) thick and that they were eroded over the years by running water and wind - forces that continue to shap this landscape. The emplacement of the basalt has temporarily stopped erosion on the Painted Desert rim, while it has continued in the valley below.
Placed ByNational Park Service, U.S. Department of the Interior
Marker ConditionNo reports yet
Date Added Friday, September 19th, 2014 at 11:14am PDT -07:00
Sorry, but we don't have a picture of this historical marker yet. If you have a picture, please share it with us. It's simple to do. 1) Become a member. 2) Adopt this historical marker listing. 3) Upload the picture.
Locationbig map
UTM (WGS84 Datum)12S E 609903 N 3881359
Decimal Degrees35.06900000, -109.79461667
Degrees and Decimal MinutesN 35° 4.14', W 109° 47.677'
Degrees, Minutes and Seconds35° 4' 8.40" N, 109° 47' 40.62" W
Driving DirectionsGoogle Maps
Area Code(s)928
Closest Postal AddressAt or near 301-399 Unnamed Road, Petrified Forest National Park AZ 86028, US
Alternative Maps Google Maps, MapQuest, Bing Maps, Yahoo Maps, MSR Maps, OpenCycleMap, MyTopo Maps, OpenStreetMap

Is this marker missing? Are the coordinates wrong? Do you have additional information that you would like to share with us? If so, check in.

Check Ins  check in   |    all

Have you seen this marker? If so, check in and tell us about it.

Comments 0 comments

Maintenance Issues
  1. Is this marker part of a series?
  2. What historical period does the marker represent?
  3. What historical place does the marker represent?
  4. What type of marker is it?
  5. What class is the marker?
  6. What style is the marker?
  7. Does the marker have a number?
  8. What year was the marker erected?
  9. This marker needs at least one picture.
  10. Can this marker be seen from the road?
  11. Is the marker in the median?