Geology

This page brings you on a virtual tour of our Geology Interpretive Trail (opened summer 2016), created by 
Dr. Spencer Lucas, Director of Research and Collections at the 
New Mexico Museum of Natural History and Science.  

Use the information provided to get a better understanding of the geologic features and the history they tell of our part of the mountain.  

A copy of the trail brochure can be downloaded at the bottom of this page, 
as well as a paper further detailing SMNHC geology written by Dr. Spencer Lucas, et al.

 


Stop 1: Fossil Area

Stop #1


This area has cobbles of Pennsylvanian limestone full of fossils of marine animals – crinoids, brachiopods, bryozoans, corals, and sponges. These cobbles are loose deposits, not bedrock. The bedrock here is Triassic mudstone.

To learn more about animal fossils found here, download our Fossil Hunt Guide at the bottom of this page.


Close-up of a bryozoan fossil
Close-up of a Bryozoan Fossil

Stop 2: Glorieta-San Andres Contact

Stop #2



The contact between Glorieta Sandstone and overlying limestone of the San Andres Formation is exposed here. This records the change from land (sandstone) to sea (limestone) during the Permian, about 270 Ma.

          
Future sandstone: dunes alongside the sea                                 Future limestone: sea floor during the Permian


Stop 3: Oldest Bedrock

Stop #3


  
 
Ripple marks
      

   

Reddish brown sandstone and siltstone (some with ripple marks) of the Permian Yeso Group are the oldest bedrock exposed on the SMNHC trails. 

 
Thin section closeups of Yeso sandstone


Stop 4: Shark's Tooth

Stop #4


                                    Shark tooth embedded in limestone                                        Artist's representation of Petalodus shark

This block of limestone has a large tooth of the shark Petalodus. The block is loose and also contains brown nodules of chert, unlike any of the local Permian limestone bedrock. This is evidence that it is actually Pennsylvanian limestone which moved from a different location.


Stop 5: Glorieta Sandstone

Stop #5




The outcrop of Glorieta Sandstone here is about 10 meters of sandstone exposed along the canyon wall. This sandstone formed around 270 million years ago as part of a vast desert that covered part of the Southwest.

Thin section closeups of Glorieta sandstone


Stop 6: Paradise Benches

Stop #6


Limestones of the San Andres Formation exposed here were formed on muddy seafloors during the Early Permian. Above and below are Glorieta sandstones. The pattern of sandstone-limestone-sandstone-limestone records the march of desert (sandstone) and sea (limestone) back and forth over time on this landscape.

Stop 7: Strike Valley

Stop #7


Thin beds of reddish sandstone are river deposits of a vast Middle Triassic floodplain. These rocks of the Moenkopi Formation are softer than underlying sandstones and limestones and overlying sandstones and conglomerates. Thus, they form a “strike valley” between two ridges (cuestas).

     
Thin section closeup of Moenkopi sandstone


Stop 8: Overlook

Stop #8




The view to the north/northwest shows the basic geological structure of the SMNHC. The center sits near the base of the vast dipslope of the Sandia Mountains, which is underlain by Pennsylvanian limestone that is exposed at the crest of the mountains. The trail apex on the west side of the property is on the cuesta formed by Permian sandstone and limestone.  The SMNHC buildings sit in the Triassic strike valley, and this overlook is on the Triassic cuesta along the SMNHC’s eastern boundary.


Stop 9: Triassic Cuesta

YouTube Video



Late Triassic sandstone and conglomerate form a ridge here, also known as a cuesta. These 230-million-year-old rocks represent huge, Mississippi-size rivers that flowed from what is now Texas to a seashore near what is now the Utah-Nevada border.


 Artist's representation of Triassic riverbed  


    
  
 Artist's representation of a Triassic amphibian



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Fiana Shapiro,
Aug 5, 2016, 10:42 AM
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Fiana Shapiro,
Jul 18, 2016, 9:59 AM
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Fiana Shapiro,
Jul 20, 2016, 2:23 PM
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