Welcome to the Perea Nature Trail Area! This is an 

easy, one-mile loop trail along a riparian area just 

outside the village of San Ysidro. Take in the sweet 

sounds of nature while viewing the colorful cliffs and 

high desert landscape as you relax on a bench in the 

shade of a giant cottonwood.

Pets

Pets are welcome but please remember 

to pick up after them and keep them on a 

leash at all times.

Location

From Bernalillo, travel about 20 miles north on US 550, 

cross the Rio Salado bridge and turn left (west) on the 

paved access road just before the village of San Ysidro. 

A brown state highway recreation sign is posted on US 

550 at the turnoff.

Latitude/Longitude: 35.54561944 / -106.7817506

A Riparian-Wetland Area

Riparian-wetland areas occupy a unique position in the 

landscape and life of the western United States. They 

are a great deal more important than we might expect, 

given their relatively small acreage (less than 2 percent 

of the land in New Mexico).

Riparian-wetland ecosystems are areas near rivers, 

lakes or springs and are important islands of 

environmental diversity. Lying within much larger, drier 

and higher (“upland”) ecosystems, these small areas 

attract greater numbers and more use by wildlife and 

livestock than their size would suggest. In terms of the 

total volume of plants they support, they are generally 

more productive than the nearby uplands. They also 

add to the supply of groundwater, reduce the effects of 

flooding, and remove pollutants.

Wetlands have a water table at, near or above the land 

surface. They are waterlogged for a long enough period 

to support “hydric” soils (with a higher level of the 

element hydrogen and less oxygen) and “hydrophytic” 

vegetation (those plants that grow well in very wet soil). 

Plants in wetlands are especially good at producing 

oxygen.

Wetlands are so productive because they can catch 

large amounts of the sun’s energy and store it as 

chemical energy, and they recycle much of the energy 

they produce on their own. These areas and their plants 

are nutrient traps that help with air and water pollution.

Perea Nature 

Trail Area

U.S. Department of the Interior

Bureau of Land Management

Geology and Wetland

Parking

Bench

Bird Viewing Area

Trail

550

Bureau of Land Management

Albuquerque District, Rio Puerco Field Office

100 Sun Ave. NE

Pan American Bldg., Suite 330

Albuquerque, New Mexico 87109

505/761-8700

or

www.blm.gov/new-mexico

In case of emergency:

Immediate Emergency – 911

BLM 24-hour Dispatch – 1/800/637-9152

BLM/NM/GI-06-05-1220

Perea Nature Trail

(one-mile loop)
Geologic Time Scale

Subdivisions Based on 

Strata/Time 

Systems/Age

Radiometric Dates

(millions of years ago)

Quaternary 0-2?

Tertiary 2?-63

Cretaceous 63-145

Jurassic 145-210

Triassic 210-255

Permian 255-280

Pennsylvanian 280-320

Mississippian 320-360

Devonian 360-415

Silurian 415-465

Ordovician 465-520

Cambrian 520-580

Precambrian 580-3,000

The view to the North, from the Perea Nature Trail, is 

dominated by a mountain peak, meagerly covered with 

native juniper and grasses. The mountain highlights the 

Jemez Mountain range, which is the southern start of 

the Rocky Mountains that extend northward to Alaska.

1. The western reaches of the mountain peak, and its 

crest, are composed of a white-to-tan sand-stone that 

forms sharp ridges. It is of the Triassic Age and called 

the Agua Sarca formation.

2. Lower, on the east side of the peak, an overlay of grey 

Permian-Age sandstone appears. The sand stone is 

called the Glorieta formation and is a cliff-forming rock.

North View 1

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3. The slope breaks abruptly, and forms a brilliant red, 

vertical face at the San Ysidro Fault. Here, the mountain 

is striped with shades of red. This was developed during 

the Permian Age and these stripes are out-crops of 

the Abo and Yeso formations. The Abo formed in river 

channels and on floodplains, while the Yeso formed in 

a shallow marine environment with local wind-blown 

sands.

4. The high rock formations with purple hues seen in 

the distance are part of the Nacimiento Mountain chain. 

These are principally granite, gneiss, and schist that 

formed during the Precambrian Age. The gneiss and 

schist form the core of the Nacimientos, and are the 

oldest rocks in the area.

Visitors to the Perea Nature Trail may look to the southwest, over the Rio Salado river bed, to view an out-standing geologic setting.

 1. The Todilto layer forms the edge of a large flat mesa 

known as ‘Blanco Mesa’, for its unusual white surface. 

The mesa has been used as a creative background for 

motion picture scenes and photographic productions, 

and for the mining of gypsum. Gypsum is mined and 

shipped to Albuquerque and Bernalillo for manufacture 

of wall-board to be used nationwide in home construction.

2. At the upper reaches of the existing cliffs, layers of 

near-white rock can be seen. These layers are known 

as the Todilto Formation, also of the Jurassic Age. The 

Todilto Formation is composed of brown limestone at 

the base and is overlain by white gypsum up to 100 feet 

thick. 

3. This layer is composed of light tan-to-yellowish sandstone cliffs, and is part of the Jurassic Age it is called 

the Entrada formation. The sandstone was formed from 

ancient sand dunes.

4. Rising from the sparsely vegetated grazing lands are 

small hills and mounds of landslide deposits, fallen from 

centuries of decay of the rocky cliffs above. These show 

an inter-mix of colors from red-to-orange in the lower 

layer, and grey-to-white material deposited from above. 

The lower layer was formed during the Triassic Age and 

is part of a group of rocks called the Chinle formation.

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South View

Geology