Geology Overview ~ The Abiquiu Area By: Connie B. Burkhart
Located on HWY 84 mile marker 215.5 the Abiquiu Dome sits at the junction of two amazing geologic zones, the Rio Grande Rift, a long, narrow dropped down section of the earth that runs from the Gulf of Mexico to central Colorado, and the Colorado Plateau, a 600-million-year-old, relatively stable, large, uplifted horizontal structure of rocks that covers the four corners region. The deep red cliff you see at the hill just past the dome marks the boundary between these two geologic zones. One other important geologic feature that lends to the beautiful landscape of Abiquiu is the Jemez mountain volcanic region. The story these rocks tell speak to primordial times when volcanoes exploded and giant rivers ran wild as the land stretched, pulled, rose and fell to create the stunning views you see around you. The landscapes also tell the stories of the people who came to this land for its resources and beauty.
THE COLORADO PLATEAU
Seen to the west and north as you look up HWY 84 and Red Wash arroyo, which borders the Abiquiu Dome property, the Plateau is a major geologic structure that extends across the 4-corners area. Looking north up Red Wash canyon from the dome, you’ll immediately notice the iconic red and yellow cliffs that Georgia O’Keeffe made famous from her views up the road at Ghost Ranch. These are the rocks of the 160-million-year-old Entrada formation that were formed during the Jurassic period when a large Saharan-like desert was home to enormous sand dunes which migrated over most of what is now the four corners area. The rocks you see here have faulted down and tilted from the fracturing at the edge of the Rio Grande Rift at the fault of the Colorado Plateau. These are the same rocks found hundreds of feet higher in the cliffs surrounding Ghost Ranch and this Jurassic, petrified dune formation is one of the same group of rocks that make up the landscape of Arches National Park near Moab, Utah.
Another obvious feature when looking up Red Wash, is the exposed edge of the Colorado Plateau that runs along the deep-red cliffs of the Cañones Fault. This is a major fracture in the earth’s crust and the cliffs draw a line between the extensive Plateau and the Rio Grande Rift zone. The deep-red rocks of the lower edge of the cliffs are 300-million-year-old muddy deposits of the Cutler formation. This pre-dinosaur rock has produced fossils of Dimetrodon, the sail-finback reptile. Another feature of this formation are ‘hoodoos’, unique towers of petrified mud with solid rock caps that can be seen near Coyote, NM and in parts of Copper Canyon to the north. This cliff line marks the Eastern-most edge of the Colorado Plateau which extends west to the St. George area of Utah and the Wasatch mountains of Salt Lake City, south to the Mogollon Rim in Arizona, and north to the Utah/Wyoming border at the Uinta mountains. As mentioned before, the rocks of the plateau have remained mostly horizontal for about 600 million years and the sediments are mostly Mesozoic, dinosaur-age deposits. Just 9 miles up HWY 84 at Ghost Ranch in the Petrified Forest member in the Chinle formation, the oldest dinosaur of North America has been unearthed! Along with the state fossil, Coelophysis, these meat eaters put Ghost Ranch and the nearby area on the paleontological map for the Triassic period finds. That land is currently yielding new discoveries at the Hayden Quarry, one of the top 10 Triassic fossil sites in the world!
THE RIO GRANDE RIFT
To the west, out of sight from the Abiquiu area, is the Basin and Range faulting zone that extends through Nevada to the Sierra Mountains of California. This series of north/south basins and mountains is of importance to us because as it shows that the North American land mass was quickly moving west and north, creating the Basin and Range zone and the Rio Grande Rift area. The land in New Mexico, from the line of the Sangre de Cristo Mountains, was holding back from this westward movement creating the extreme opportunity for the land to fracture. The more the land stayed put here, the more “ripping” strain was put on the fracture zone, thus creating a “tear” in the earth’s crust that currently extends from the Gulf of Mexico to Buena Vista, Colorado, below Leadville. Imagine holding three blocks in your hands, the middle one held by the pressure of the two on each side. As the gap opens, the middle block falls. This is the process that created the Rio Grande Rift and the basin and range zone in Nevada with its north and south-trending valleys and alternating mountain ranges. It also created Death Valley, a below sea level ‘block’ that dropped as the west coast pulled westward! The Rio Grande Rift is only about 20 miles wide (east to west) and over 300 miles long (north to south). The Sangre de Cristo and Sandia Mountains border the rift on the east side. The Rift sank as the land pulled away creating a break in the North American plate deeper than the Grand Canyon! We don’t see a canyon here simply because the land was sinking, not rising for the river to cut through it. Instead of a great canyon, the low land filled with sediment. What we do have are deep channels along the Rift that allowed hot magma to ooze its way up the fractures and veins of the rocks creating huge volcanic eruptions and explosions as seen at Bandelier/Los Alamos, Mt. Taylor, the Jemez Calerda and the Questa Calerda above Taos. These deep faults on the east and west side of the Rift brought us the volcanoes, mesas, gorges and canyons that are a hallmark of New Mexico landscape.
As you travel south on HWY 84 (coming from Ghost Ranch) just up the road you drive down the cliff created by the Colorado Plateau fault along the Chama river canyon and you arrive onto the ”Abiquiu arm” of the Rio Grande Rift, where the Abiquiu Dome is located. The age and composition of the rocks change drastically, as does the age of the landscape you see. You have journeyed from 300 million-year-old rocks to 20 million-year-old rocks in less than a mile! The Rio Grande Rift began sinking about 30 million-years-ago allowing for the creation of the landscape that you see in Abqiuiu.
The long, low mesas you see to the East from the dome are capped by lava flows from the Jemez volcanic region, as are the mesas to the south across the Chama River (Rio Chama). Even Pedernal, the famous flat-topped mountain you view out the front of the casita as it peeks over the mesa, is capped with an 8-million-year-old lava flow from the rift volcano of the Jemez Mountains. When lava flowed from eruptions it filled the ancient valleys where rivers and streams ran hundreds of feet higher then their present day elevation. With their course blocked by hard rock, the water found new paths and scoured away the softer sediments to the Chama and Rio Grande rivers. This erosion left what we call an inverted valley; the ancient low waterway is now the mesa top, capped with hard basalt rock that is resistant to the ongoing erosion. In addition the earlier volcanoes of the Taos/Latir area produced new rocks and debris that were eroded and transported by large rivers and deposited in the ‘new’ lower area of the Rio Grande Rift. Without the rift, the deep earth magma would not have reached the surface and the vistas you see would not be present today.
ABIQUIU ROCK FORMATIONS
There are four sandstone rock formations from Rio Grande Rift fill sediments that are seen in Abiquiu. They exist from the process of reconfiguring existing material by way of great river deposition that left large sections of sandstone conglomerates. Some of these rock units are composed of volcanic sediments, ash, mud and boulders ripped out of ancient existing rock of rising mountains to the north and west. Rivers ran to the newly formed rift “depression” and piled up layer upon layer filling the rift in epic proportion.
ROCK FORMATION # 1: The oldest Tertiary deposit is the El Rito conglomerate, 45 – 35 million years ago. This red sandstone with distinct huge boulders and rounded rock beds first presents itself just beyond the dome before you drive up the red cliff toward Ghost Ranch. Rivers depositing this rock flowed from rising rocky Mountain uplifts of the Tusas (north) and Nacimiento Mountains (west). It can be seen about a mile up Red Wash canyon and it is one of the expansive formations in the eroded/tilted walls of Copper Canyon arroyo to the north and other unnamed canyons to the east.
ROCK FORMATION # 2: Above the El Rito deposit is the 29 million year old Ritito formation. It presents itself right across HWY 84 in the gray, low cliff at the edge of Red Wash. If you hike up Red Wash just a ¼ mile you’ll see rounded river rocks and boulders piled up in the eroded wall cuts of the arroyo on your first major left turn in the drainage. This rock holds rounds stone of Ortega Quartzite, some of the oldest rocks in New Mexico, eroded from the core of the Tusus Mountains. This matrix of this rock is strong until it receives rain and then the cobbles and stones are released to the waiting arroyo and the rocks are moved down to the Chama River in high water floods. As you walk Red Wash arroyo you will see an amazing display of rocks, many of which were carried and deposited millions of years ago, then eroded out again on their journey to sea level. Although this rock formation may not have the ‘beauty’ of other Abiquiu rocks, take the time to look closely at the amazing array of stones the river carried 29 million years in the past.
ROCK FORMATION # 3: Above the Ritito formation is the 22 million-year-old white sandstone of the Abiquiu Formation. It is less rocky than the Ritito, composed of ashy fine sand and smaller river deposit conglomerate. Just down the road the Abiquiu Formation at Plaza Blanca, the White Place, was made famous by Georgia O’Keeffe, who loved the forms this rock created and painted there often. A hike in this area will produce a moon-like landscape of white sandstone pillars and canyons.
From the Abqiuiu Dome the Abiquiu formation is best seen looking south across the Chama River where you see the white rock in the cliffs of the mesa. From that view you can also take note of the basalt lava flow capping the ‘mountain’. The amazing rock spires and canyons just behind the elementary school in Abiquiu are also part of the rock formation.
The Abiquiu formation is often confused with the white rock that makes up the cliffs at Bandelier National Monument to the south. It is not the same rock. Those rocks are younger and were formed just over 1.5 million years ago when the volcano of the Jemez Mountains experienced a catastrophic explosion, dumping debris on the side of the volcano forming the Bandelier white sandstone and sending ash as far away as what is now Oklahoma! A fabulous drive through Los Alamos to the Valles (pronounced ‘Vayes’) Caldera, the heart of the volcano is quite stunning and the layers and volcanic deposits viewed on the road up from Española are unique to the region.
ROCK FORMATION # 4: The youngest formation seen in Abiquiu is the pinkish orange Tesuque formation, a well-cemented, conglomerate sandstone which is 20 – 8 million years old and represents deposits from rivers coming off of the Sangre de Cristo Mountains and other mountains to the north. Cerrito Blanca is the iconic high mesa behind Bodes store and it is composed of Tesuque rock that has been ‘pushed’ up in a thrust fault as the Rio Grande Rift continued to spread. At Plaza Blanca, this resistant, dense rock with multi-colored rocks in its mix is resting on the surface of the Abiquiu formation and, as erosion removes the softer matrix of this lower rock unit, heavier stones are ‘dropped’, often creating a ‘pavement’ effect. It is a stark contrast to the main white landscape. These are “left over” heavy components of Tesuque formation also make interesting landscapes. Much like a hard, crusty topping may slide off a soft pudding-like base; this heavy rock is often seen tilted after sliding down the softer, unstable Abiquiu formation. If you hike the Plaza Blanca trail you will see this event to the right just before the trail turns left up the canyon…it’s worth looking at. The Tesuque formation takes over through the rest of the Chama river valley down into the Española area.
HISTORY ~ TREASURES FOR RESOURCE & BEAUTY
The Abiquiu area is truly a geologic wonder with all its features, faults, volcanoes and river erosion! Not only are the natural vistas something to explore and admire today, they are the reason many people came to this area over 13 thousand years ago. Volcanoes produced rocks like chert, flint, and obsidian that were treasured for making stone tools and weapons. The muddy rock formations of the Chinle and Cutler provided clay deposits rich with mica and other minerals, perfect for firing and decorating pottery. The ancient Pueblo cultures that migrated along the river drainages after the fall of Chaco Canyon near 1150AD left pieces of this pottery everywhere along the Chama river valley mesas. In the 1300’s & 1400’s many Pueblos with large plazas and room blocks were constructed in this area adjacent to Sunflower Canyon Casita, yet today they escape the view of many visitors.
Mesas around Abiquiu hold ancient adobe pueblos, melting with age but full of evidence of past people who called this place home. The area provided a wealth of materials used for hunting, agriculture, and trading. Everyone, from early mammoth hunters to the ancient Pueblo people, found this region to be a desired place to come and, due to that, there arose conflict for space, land and resources.
In recent geologic history, the Chama River cut a canyon through the large cliff fault at the edge of the Colorado Plateau and provided a never-ending supply of water to animals and people. It was a natural access point back and forth from the high country of the plateau to the Rio Grande and was used as a gateway to the land north and west, including Chaco canyon and the Hopi Mesas. This eventual path, now known as the Old Spanish Trail, was used in 1776 by the Escalante/Dominguez expedition, looking for a way from Santa Fe to Monterey, CA. The area where the Abiquiu Dome now sits is known as Los Silvestres, the place of the wild ones. In those unsettled times in the early 1700’s it served as a buffer for the Pueblo of Abiquiu and the threat of hostility from the unsettled country to the west.
In the 1830’s this trail was used with horse and mule to create a trade route between Santa Fe and the Los Angeles region. Families from Abiquiu also migrated to Southern CA to find new places to build their own futures. One of those groups included the Chavez family, who used the Old Spanish Trail and settled in the hills of Southern CA. Today the area is know as Chavez Ravine and is home to Dodger Stadium. The Old Spanish Trail was a hard, long, varied route of travel that terminated at Olivera Street in Los Angeles.
Until the early 1900’s, the area west of Abqiuiu was still wild and mostly unsettled with a few homesteads from cattle rustlers and camps of the UTE and Apache tribes. In fact one of the last areas of settlement travelers passed was this area of Los Silvestres, where the dome is located. Still today, when hiking in the hills, you can find evidence of cultural sites: cowboy campsites, tee pee rings, ancient artifacts, arrowheads, and flakes from tool making that were harvested from the geologic deposits in the surrounding hills. In our current age, you may stumble upon fossil sites as well! Just a few miles away up HWY 84, a hiker found a mammoth site in 2015! Mammoth wallows can be found on the ancient Chama River terraces right up stream from the casita. Ice Age mammal fossils are also found down in the Española area as well and speak to a time when the climate was moist and the air was cold. During this period, The Rio Grande River pooled up in lakes before cutting its course through the land, becoming a continuous river, flowing through to the Gulf of Mexico.
There are so many stories to tell of the rocks, fossils and the ancient ones, but for now, we invite you to take a deep breath and enjoy your time here in the unique and amazing Abiquiu area. As you venture out and about, keep your eyes open. You never know what you may discover!