Friday, July 25, 2014

Pebble Pups Conserve Cripple Creek's Mineral Collection

     The Pikes Peak Pebble Pups are taking turns this year to work on the mineral collection displayed at the Cripple Creek District Museum. The museum is located in Cripple Creek, Colorado on 5th and Bennett Avenue in what was the Midland Railroad depot.

Figure 1: Ben Nemo, who is in 5th grade, spent a day at the museum
working on conserving one of Colorado’s most important
mineral collections. Photo credit: Steven Veatch.
     The mineral and rock collection is from the historic mines of the Cripple Creek and Victor Gold Mining District. Gold tellurides make up the majority of the collection. Pebble pups take turns working a shift with three scientists where they learn the procedures involved with conserving and cataloging this remarkable collection. The pebble pups learn and then perform a number of steps while working at the museum. First, the specimen is imaged in a photography light tent. The specimen is then examined with a microscope. During this examination Dr. Bob Carnein describes the specimen.  A museum technician types Dr. Carnein’s description in a computer. John Rakowski, a geologist, also writes the description in a lab notebook. Next measurements (in the metric system) are taken and recorded.

Steven Marquez will be starting 8th grade. Steven measured specimens,
learned how to take photos through the microscope, and painted labels
on each specimen. Photo credit: Steven Veatch.
     The second step it to brush a strip of archival white paint on the specimen; after the paint dries an archival pen is used to write a unique catalog number directly on the paint strip. Steven Veatch, the project leader at the museum and the pebble pup leader, creates in the final step a photomicrograph—or an image with a microscope—of the specimen. The pebble pups, who range in age from 10 to 16 years old, work on all steps of the cataloging and conservation effort. The pebble pups, at the end of their work, receive a certificate of training from Kathy Reynolds, the museum director.

A microphotograph of a crystal of gold-bearing calaverite.
Photo credit: Steven Marquez. 
 

     The Pikes Peak Pebble Pup program (PPPP) includes students K-12 who explore the geosciences in the Pikes Peak region of Colorado. The program participates with the Future Rockhounds of America under the American Federation of Mineralogical Societies. The PPPP is composed of the youth of the Lake George Gem and Mineral Club (Teller County), and the Colorado Springs Mineralogical Society (El Paso County). A number of students from the United Kingdom participate in the program through the Internet. The goal of the program is to teach pebble pups to become rockhounds. Teen members of the group are called earth science scholars. The program focuses on communication, collaboration, creativity, and critical thinking. Communication is achieved through a blog site (http://pebblepups.blogspot.com/) where merit badge assignments, lessons, and pebble pup written work or art work is posted. The PPPP use Facebook™ as a method of communication within the group. Collaboration is through local and regional museums, the Florissant Fossil Beds National Monument, the Science Olympiad, and Cool Science.
     Accomplishments of the PPPP include first place and third place awards in the National Park Service’s art contest for National Fossil Day; monthly articles published in the Ute Country News; and researched articles are published in an international magazine. Two pebble pups entered a poetry contest sponsored by the Library of Congress: one pebble pup was a finalist in the nation and received a medal from the U.S. Poet Laureate while another pebble pup won first place in Colorado. A book of collected poems on geoscience by the PPPP has been published with all of the books sold within weeks. A teen PPPP presented a paper at an Ice Age symposium last year at the Colorado School of Mines campus. Several PPPP were coauthors on papers presented at the University of Denver and the New Mexico Institute of Mining and Technology in Socorro, New Mexico.
     The pebble pups meet monthly during the academic school year. As there are so many ways for the PPPP to express their creative energies; the retention rate is very high. The informal setting allows for a more complete understanding of geoscience due to a more focused learning environment. The informal setting also allows for more personal and meaningful interaction between the informal educator and student. Students engaged in informal education are benefited on a personal level more than they would be in a formal setting. The informal education of the PPPP has proven to be more supportive to the development and growth of a student both intellectually and emotionally compared to education in a strictly controlled, formal learning environment. For more information on the PPPP contact Steven Veatch through his email at: steven.veatch@gmail.com.

Saturday, December 7, 2013

Cripple Creek's District Museum Mineral Collection



Each month, for the past several years, I go twice  a month with two other scientists (Bob Carnein and John Rakowski) to catalog, photograph, and record detailed information on each specimen we work with. We donate our time to this important project. The Cripple Creek & Victor Gold Mining Company provided the funding for the archival materials that includes special paint and ink pens for catalog numbers, an ultrasonic cleaner, and other miscellaneous materials for the project. In addition to standard photographs of the specimens we work with, microphotographs are taken of certain specimens.I have a few microphotographs of selected specimens I would like to share with you.


Sylvanite crystals in quartz.  Sylvanite is a gold
telluride mineral. Photo © by S. W. Veatch
Calavarite gold telluride mineral specimen no. 196
Photo © by S. W. Veatch
Sylvanite crystal. Specimen no. 196.
Photo © by S. W. Veatch

Sylvanite crystal..  Specimen no 229.
Photo © by S. W. Veatch

Large gold blister from roasted gold sample.
Specimen no. 245. Photo © by S. W. Veatch
Roasted gold specimen no. 246.
Photo © by S. W. Veatch
Roasted gold specimen no. 248.
S. W. Veatch photograph




Another view of specimen 248 showing multiple gold blisters from roasting.
Photo © by S. W. Veatch


Cripple Creek gold ore sliced by diamond rock saw.
Gold and fluorite is present.
Photo © by S. W. Veatch


Calavarite specimen no. 81
Photo © by S. W. Veatch


Group of calavarite gold telluride specimens
Photo © by S. W. Veatch


Krennerite (?) gold telluride specimen no. 129
Photo © by S. W. Veatch

Krennerite (?) gold telluride specimen.
Photo by S. Veatch


Twin crystal of sylvanite. Specimen no. 146.Photo © by S. W. Veatch






Sunday, July 28, 2013

Remarkable Trace Fossil Found Near Woodland Park May Hold Clues to an Ancient Sandstone

By Steven Wade Veatch and Zachary Sepulveda

Winding into the mountains, U.S. highway 24 closely follows the Ute Pass fault, a major fault that separates the Rampart Range from the Pikes Peak massif and the rest of the Front Range. Starting southeast of Cheyenne Mountain, the Ute Pass fault can be traced for about 60 miles, and heads north along state highway 67 beyond Woodland Park. The fault zone is relatively wide and filled with broken and fractured rocks that create the course of Fountain Creek in Ute Pass.
There are at least three resistant ridges made up of sandstone exposed along Ute Pass and in the Woodland Park area. These can be thought of as “fault slices” of a sandstone rock unit “jammed” in Pikes Peak Granite during past movements of the Ute Pass fault. The sandstone rocks are called “injectites” by a number of geologists to describe this remarkable formation. Generally, the color of the injectites is reddish or maroon, but some of the weathered injectites have a buff discoloration on weathered surfaces that is related to the iron oxide cement present in the sandstone.

Today the injectites remain a source of much scientific debate. This was thought to be a sandstone unit called the Sawatch Sandstone that was deposited during the Paleozoic Era in the Cambrian Period—when there was an explosion of multicellular life. Geologists give names to units of rock that were formed generally in the same way at the same time so they can talk about them and map them. Upon closer examination, it is clear this is probably not Sawatch Sandstone. During a recent field trip attended by  seven geologists studying these features in Woodland Park, the scientists began to consider this sandstone was perhaps pre-Cambrian, formed at a time before there was multicellular life on Earth. During the intense and concentrated discussion during this field trip, the scientists considered it a distinct possibility this sandstone was laid down before larger life forms were present; Steve Spence, a geology student at Pikes Peak Community College, climbed a steep slope of this enigmatic sandstone while the geologists were fervently debating.  He came back down with an object he had never seen before and brought it to one of the authors (Veatch) and said, “What is this unusual looking thing?”

Steve Spence, a Pikes Peak Community College Student
with the trace fossil he found. Photo © by S.W. Veatch
Veatch knew exactly what it was—it was a trace fossil of a larger, multicellular creature that once crawled its way through the wet and moist sand millions of years ago. This large trace fossil put the primordial sandstone back in the Paleozoic when there were large, multicellular organisms.


The tube-like structure or the trace fossil was formed by the creature crawling through this ancient
sand and can be clearly seen from this side view. Steven Spence specimen. Photo © S. W. Veatch.

Trace fossils, also known as ichnofossils, are a very important kind of fossil, they record behavior exhibited by prehistoric creatures. They are formed by animals performing actions, rather than animals dying and being preserved in sediment. For instance, a trace fossil might be formed by a worm burrowing its way through the sand, leaving a trail that gets preserved for all of eternity; or a dinosaur traveling to its nesting site and leaving a trail of footprints in deep mud. The term trace fossil may also include other things like remnants organisms left behind, for example, egg shells or coprolites (scat or droppings). Trace fossils leave us with indirect evidence of how past animals lived their lives and how they may have behaved.

Footprint fossils can give us insight not only into the behavior of prehistoric animals, but also into their physical attributes. By looking at footprints we can determine the size, speed, and weight of the animal creating the print. Trace fossils are a valuable source of information on prehistoric animals' behavior and biology.

This is a good example of how science works, and how something can change like the name and age of a sandstone unit. Geologists for decades thought it was the Sawatch Sandstone, and now geologists do not know what the name of the sandstone is or the age of it. Now science has a trace fossil from Woodland Park to add to the understanding of this puzzling sandstone. Scientists will soon probe the mysteries of this ancient sandstone embedded in Pikes Peak Granite and hopefully assign a name and age to it.

About the authors:

Steven Veatch is from a descendant from Cripple Creek miners who mined in the Cripple Creek and Victor Mining District from 1892 to the late 1930s. He teaches the Pikes Peak Pebble Pups to become responsible rock hounds, writers, poets, and scientists. 











Zachary Sepulveda attends Palmer Ridge High School in Monument, Colorado. He is from Southern California, and has always been interested in geology, paleontology and biology. He is looking forward to making a meaningful contribution to the field of science.  His other interests include creative writing and drawing. Some of his poetry and drawings have been published in magazines such as Deposits and in local newspapers. Zachary is a member of the Colorado Springs Mineralogical Society (CSMS) and participates actively in the Pebble Pup/Junior program. He is also a member of the Colorado Scientific Society. 

Monday, March 25, 2013

Dr. John Allen Veatch: A Wayfaring Pioneer in Science and Politics

One hot summer day I was leading a field trip to a site not far from the Colorado School of Mines in Golden, Colorado. As the Colorado sun climbed to its meridian in a blue sky, we explored the local areas where paleontology presented itself in a profusion of mystery and wonder. The most interesting sites to me were narrow and deep slot ravines, cut from clay mining decades ago that now exposed fossil dinosaur tracks, fossil foliage, and a prehistoric rainstorm—where individual rain drops were preserved in mud that had turned, over time, into a layer of sedimentary rock. By the time I arrived with my field party to the mined out slot ravines, the sun was shining directly into them, making the temperature in the ravines seem like the heat of an assayer’s oven.

By the afternoon, we needed a place to cool off from a long day in the summer heat, so I took my group to the Colorado School of Mines Geology Museum. Once we went inside, we were greeted with welcomed cool air flowing from air conditioning vents. In this excellent museum, I showed my field party—a group of people of mixed ages and backgrounds—the section where Colorado gold ore and gold nuggets glittered in the light. Everyone’s eyes were wide, and I could see the sparkling gold reflected in their eyes. A number of jaws silently dropped. All of these gold specimens were from historic Colorado mining sites. Soon, I lost the group as they spread out to look at the fabulous Colorado crystals, rocks, and fossils on display.

I knew on the lower level in the museum the location of an uncommon mineral with an unusual name: veatchite, a strontium borate. I saw this mineral in the museum’s case on a previous trip. After a good hour had passed I went back upstairs and herded my entire group to the lower level of the museum, where I showed everyone that specimen of veatchite in the mineral cabinet.  I wished I could tell them I discovered it, but I had not. This specimen was named after one of my ancestors.  Even though I can’t claim to be its namesake, veatchite and especially the man it was named for had an impact on my life. Is it possible that the passions of your ancestors, especially if they are on both sides of your family, can become your passions?

Image of Veatchite at the Colorado School of Mines Musuem.
© by Steven Wade Veatch
John Allen Veatch was a surgeon, surveyor, and scientist. He was born March 5, 1808, the first of eight children in a Kentucky frontier family. John Veatch’s mother died when he was fourteen. This was a very difficult time for his family. Money was scarce. The Veatch family decided to move to Spencer County, Indiana to start a new life. Another part of the Kentucky Veatch family—attracted by good farmland—moved from Kentucky to northeast Missouri. I am a direct descendent of the Missouri group.
Dr. J. A. Veatch, courtesy photo.

 At the age of nineteen, John Veatch knew that he had to make his own way in the world and look for fresh opportunities. He returned to Kentucky where he started his studies of medicine under a practicing physician, Dr. John Work in Louisville and soon became part of his practice. I noticed in those days it did not take as long to become a medical doctor as it does today.

John Veatch had a restless side to him, and after he had learned as much as he wanted to about the medical profession, he decided to leave Kentucky in 1829. He moved to Louisiana on the Pearl River near Covington and landed a job teaching school. He married Charlotte Edwards in 1831 and had two children:  Andrew Allen Veatch was born in 1832 in Covington and a year later Samuel Houston Veatch was also born in Covington. Samuel Houston Veatch was named after the great Texas General Sam Houston. Charlotte Veatch was so impressed with his "manners and distinguished presence” that she decided that her newborn child would be named Samuel Houston.

In 1834, Dr. Veatch moved to Texas with his family. While in Texas he bought land in Hardin, Trinity, and Jefferson counties. He later obtained additional land in the Zaval Land Grant from the Mexican government. This land would become, fifty years later, sites (Sour Lake and Spindletop) of significant oil discoveries and was some of the most valuable land in Texas. Although he no longer owned all of his holdings in the original Zaval Land Grant at his death, his grandson inherited what was left, 284 acres of oil land in the central part of the Sour Lake District.

The Texas Handbook describes Dr. Veatch as a giant man, standing 6' 4" tall and weighing over 200 pounds. His complexion was fair; he had blue eyes and auburn hair. Is it too much of a stretch to think some of those traits still exist in the Veatch bloodline? After all, I’m 6’ 2” and mild tempered. And, more to the point, I’m also a geologist. I like to think Dr. Veatch would have been proud of me and interested in my geological studies.

Dr. Veatch, during this time, wore more clothing than we do. Because there was no sunscreen, he wore shirts with high necks and long sleeves and long trousers during his field work. He also wore a wide-brimmed hat to have added protection from the sun. Since zippers and snaps had not been invented yet, he relied on buttons, hooks, and eyes for closure. He was characterized as a strong Democrat and was skilled in making friends. The Democrats at this time in history were the party of tradition—the successors of the Jeffersonian agrarians who looked back to the past and were suspicious of banks and corporations. Democrats had a strong commitment to states' rights, a limited federal government, and a continued agrarian ideal. The Democrats (during this time period) were composed of northern craftsman who felt vulnerable to the expansion of industry, farmers who were unhappy with tariffs, immigrants who wanted to maintain their own traditions, southerners who believed in the right to own slaves, and westerners who were in favor of land acquisition by any means, including war.

Dr. Veatch was a capable man and had many intellectual interests. Books became his college. He began to study botany and mineralogy while in Texas. Dr. Veatch was an emissary of science and medicine with wide sympathies, probity, and a strong sense of purpose. He was involved in the political movement seeking the independence of Texas. He was elected as a delegate from Bevil’s settlement (a pre-republic community of settlers between the Neches and Sabine rivers) to the Consultation of 1835, a crowded and raucous assembly that met to consider independent rule for Texas and even armed rebellion to achieve it.  Samuel Houston attended this consultation. Did my ancestor pound his fists on the table like some of the others at the meeting, demanding to be heard? Or did he merely stand on the sidelines, offering considered commentary later in the quiet of a side room conversation? Maybe he gestured and waited to be recognized, making the right point at just the right moment, helping Texas seal it history, if only for a few remembered years?

I’ve given my fair share of speeches in my own career as a geologist but, somehow what I learned about Dr. Veatch feels more impressive. He must have been considered an activist in his times. He even joined the militia during the battles for the independence of Texas. Surely he influenced others with his opinions.  For my part, I prefer exploring the landscape and playing a guitar in old mining camps. To each his own.

The following year (1836), the Texas Declaration of Independence was signed by Samuel Houston and the Battle of the Alamo occurred, where defenders, with infinite courage, held out for 13 days against General Antonio López de Santa Anna's army. The rallying cries “Remember the Alamo!" filled the ranks of the Texan Army led by General Sam Houston. On April 21, his militia attacked the Mexican army at the Battle of San Jacinto, where General Santa Anna was defeated and captured. The independence of Texas was now certain.

The Texas landscape is seemingly endless, like eternity. In the 1840s Dr. Veatch practiced medicine in the new settlement of Town Bluff, Texas. Summer in the area was beautiful: the sun’s light nurtured a landscape dotted with wild flowers that filled the mind with the music of nature. At sundown, the Texas bluebonnets and crimson clover blaze in the golden sunlight of evening while coyotes carefully stalk their prey.

The peaceful beauty did not last long—tragedy struck with the untimely death of Dr. Veatch’s wife Charlotte in 1844. Then the tensions between the United States and Mexico intensified and ultimately reached a breaking point: Between 1846 and 1848, the United States and Mexico went to war. In the war with Mexico, Dr. Veatch served as first lieutenant in Mirabeau B. Lamar’s Independent Volunteer Company during 1846-47. He was the surgeon for this military unit. He also raised a company of men in 1847 that included his two sons, Andrew Allen Veatch and Samuel Houston Veatch. Samuel Houston Veatch was only 14 when he served in his father’s company in the War with Mexico. Later Dr. Veatch served as a Captain in the Texas Mounted Volunteers, who defended the Texas frontier from 1847-1848. The Treaty of Guadalupe Hidalgo, signed on February 2, 1848, ended the war between the United States and Mexico. By the end of the war, Mexico lost nearly half of its territory—the American Southwest from Texas to California.

By 1850, Veatch had moved to San Antonio and continued amassing widespread landholdings in Texas. Dr. Veatch married Ann M. Bradley while living in San Antonio. She had five children from her former marriage—all born in Alabama. Restless for adventure, Dr. Veatch gathered his reins and rode for California where many men were still searching for a golden bonanza. Following a crumbling marriage, Dr. Veatch and Ann divorced while he was in California. His sons Andrew and Samuel came with him to California and kept busy while they panned gold in the gravel bars of streams and rivers.  California continued to experience a large number of people coming into the state looking for gold deposits. It was during Dr. Veatch’s explorations in California that he discovered large deposits of borax (borate related minerals or chemical compounds) in Lake County in 1856.  I can see the site in my mind: the mineral pools, water running over stones, and natural gardens of cactus. Nothing moves other than heat waves, a slight breeze, and a lizard running over a rock slab. As a result of his work there, he published “The Report of Dr. John A. Veatch to the Borax Company of California” in 1857. Subsequently borax became “white gold.” Borax, boric acid, and other compounds of boron were used for medicine, the preservation of food, in glass blowing, and in other industrial applications.

Veatchite, a borate mineral, was discovered in 1938 at the Sterling Borax Mine in Tick Canyon, Los Angeles County, California. Veatchite was named to honor John Veatch. The Sterling Borax Mine is the type locality for veatchite.  To have a new species of mineral or fossil named after a person is a high honor in the world of science. Sometimes, a new mineral, plant, or animal species is named after the scientist who first worked with it, or it can be named after a colleague, a poet, or anyone to honor that person. Generally, the discoverer has the privilege of naming the new species. Since veatchite was not discovered until decades after Dr. Veatch’s investigations, the new mineral was named to honor his scientific work and contributions. Dr. Veatch passed away before the great fortunes were made in the borax industry by 20-mule teams pulling wagons full of borax to processing plants. Dr. Veatch, however, at the time of his death, was far from penniless; he still owned some of the most valuable land in Texas that contained “black gold.”

Dr. Veatch put much in motion when he conducted his studies on the mineral waters in California. While still in California, Dr. Veatch also explored and surveyed Carros Island (off Lower California) in 1858, and then he was the curator of conchology (study of molluscs) at the California Academy of Sciences from 1858 to 1861. He also authored several scientific papers during this period.

In 1862, Dr. Veatch moved yet again.  I think he sought out the wild places where the thunder roared, dust devils whirled, and where he could study the Earth where it revealed itself in the rock record. This time he headed for the gold and silver fields of the Comstock Lode in Nevada—the first major discovery of silver ore in the United States. The Comstock Lode discovery was announced in 1859, starting the “Rush to Washoe” and the establishment of Virginia City almost overnight. Dr. Veatch arrived, after the dust of discovery settled, in 1862—to explore a new mining district. It is hard for any geologist to resist the call of a new discovery of ore and have the chance to study the geological conditions that formed it.

Dr. Veatch practiced medicine and worked in geology in the Comstock Mining District for two years. His son Andrew was superintendent of the reduction works of the Central Mill in the district. Andrew Veatch studied mining and became a prominent mining engineer. I’m not certain how Andrew died, only that he didn’t outlive his father and was sadly buried in 1872, at the young age of 40, in California.  Mentzelia veatchiana or Veatch's blazingstar, when discovered and described by scientists, was named to honor Andrew Veatch.  Samuel Houston Veatch served in the Confederate army and became a Christian minister.

By 1865, Dr. Veatch married a third wife, Samanthe Brisbee. After Dr. Veatch left Virginia City, he worked as a geologist in San Francisco. He maintained an office at 712 Montgomery Street. If his desk was anything like mine, and I like to think it might have been, it surely was cluttered with mineral samples, dusty scales, rock fragments next to a petrographic microscope, and stacks of colorful geologic maps.

Dr. Veatch made an unsuccessful attempt to become state geologist of Oregon in 1868 while still working in San Francisco. He remained in San Francisco until 1869, when his wife Samanthe died.

After his disappointment of not becoming Oregon’s state geologist and the loss of his wife, Dr. Veatch moved to Oregon to join the faculty of Oregon’s first medical school—Willamette University Medical School (in 1913 it became the University of Oregon School of Medicine). He was the professor of chemistry and toxicology. Unfortunately, Dr. Veatch did not hold his new position very long; he died of pneumonia in Portland on April 24, 1870. A new plant species was officially named in 1873 by the California Academy of Science in honor of Dr. Veatch for his pioneering botanical work: Garrya veatchii or Canyon siltassel.  Lotus dendroideus variety veatchii; and Acmispon dendroideus variety veatchii or San Miguel Island deerweed were also named to honor Dr. Veatch.

At the Colorado School of Mines Geology Museum, the group that I led on the field trip that summer day would not know this story of Dr. Veatch by looking through the glass case at veatchite. I did gather the story, and piecing together Dr. Veatch’s life and sharing his name  has helped me to find meaning in my life and helped me to understand why we I enjoy geology so much. In the quest to understand my own life’s path, I believe that the groundwork of my ancestors paved the way for me to do the work I was born to do and that I am now doing today.  

In contrast to Dr. Veatch and countless other wanderers in our nation’s early history—I remain tied to Colorado—just as some of my other ancestors did in the Caribou, Nederland, and Cripple Creek mining camps of Colorado. I made a commitment to Colorado’s mountains, mines, minerals, and fossils to stay in one place so that I could really know the geology of the ground I walk over.

Tuesday, February 26, 2013

Earth Science and Archaeology Haiku Poetry for Fun


 Through many seasons
An ancient volcanic field
Evokes thoughtful pasts 



 
Ancient tree of stone
Herald of another world
Revealing the past



                 
 
 
 
 
Stone Nefertiti
The Queen of Akhenaten
Shifted by a fault






 

 

The sky rejoices
A time for tomorrow’s dreams
Whispering new thoughts








 


A bear carved in rock
Watching the canyon spirits
As a shaman chants




 
 Ancient petroglyph
Art pecked in dark rock varnish
A sacred message




Winter forest realm
Snow spreads its gleaming blanket
A stream turns to ice






The Ice Age icon
A mighty mammoth rules all
Until man arrives













Guest Blogger: Ice Age Poetry by Zach Sepulveda

Twilight of the Mammoths


Perched upon a grassy hill ancient hunters prepare to make a kill…

Blaring trumpets shatter the air
Terrified voices echo despair
Hurtling towards their own demise
A chance at life, their fate denies

The blood of giants spills forth upon the grass
Brought forth by razor-edged volcanic glass
Marching closer to defeat with each fresh laceration
Panicking behemoths flee from inevitable damnation

Perfectly adapted to a dying world
Their fate was sealed when their blanket of ice unfurled
Their fragile world was brought to bear before the fury of the sun
And before they even knew it, their time on earth was done.


Sketch of a Columbian mammoth
© Zachary J. Sepulveda





                                             
 























About the author: Zachary Sepulveda recently moved to the Pikes Peak region from San Diego, CA. He became interested in paleontology by visiting the La Brea Tar Pits in Los Angeles as often as he could. He is a junior member of the Colorado Springs Mineralogical Society and is part of the Pikes Peak Pebble Pups and Earth Science Scholars Program. Zach is 15 years old and is in 10th grade at Palmer Ridge High School in Monument, Colorado.

Note: Zachary will be representing the Colorado Springs Mineralogical Society and the Colorado Scientific Society at the Western Interior Paleontological Society's Founders Symposium: Ice Worlds and Their Fossils. He will present a poster as part of a section on "Bringing the Past to Life (Artist Scientist Panel)." His poster is on poetry and art.



   

Thursday, December 27, 2012

THE RIO GRANDE RIFT

By Steven Wade Veatch

Introduction
A major break in the Earth’s crust – the Rio Grande rift – starts in central Colorado’s Rocky Mountains and runs southward through Colorado and New Mexico into the Mexican State of Chihuahua. The rift is formed where a section of the Earth’s crust arched, weakened, and spread apart due to heat from basaltic magma welling up from the mantle 29 million years ago.

The stretched and brittle crust in the rift thinned and fractured. As tensional forces pulled apart the crust, sections subsided along north-south faults. Some sections dropped more than 8,000 meters. The rifting process resulted in a long rift valley dominated by four connected closed basins in which lava, volcanic ash, and sediments accumulated.

Twenty million years ago, as the North American plate continued to scrape along the east edge of the Pacific plate, crustal stresses resulted in a period of regional uplift, raising much of the southwestern United states to its present elevation. Colorado and adjacent states rose 1,500 meters higher than before the uplift (Chapin and Cather, 1994). During this time of uplift rivers, including the Rio Grande, began flowing into closed basins along the rift. As sand, gravel, and volcanic deposits filled the basins and valleys, the streams ultimately came together forming the Rio Grande River.

Beginning of Rifting
The Rio Grande rift is geologically young, starting 29 million years ago in the Leadville area. Two major episodes of extension have formed the Rio Grande rift. The fist occurred in late Oligocene to early Miocene time beginning 29 million years ago and lasting 10 to 12 million years. Strain rates were less during this early phase of rifting, except where volcanism and high heat flow caused local concentration of extensional strain.

Rifting began to separate the Colorado Plateau from the Great Plains. West of the rift the crust of the Colorado Plateau is approximately 45 kilometers thick; east of the rift the crust beneath the Great Plains is 50 kilometers thick; beneath the rift zone the crust is only 35 kilometers thick (Chapin and Cather, 1994).

Faulting began with the onset of rifting, causing earthquakes along certain areas of the rift zone. Several of New Mexico’s early pueblos were partially destroyed by earthquakes caused by the Rio Grande rift. Faulting and associated earthquakes continue today as the Rio Grande rift continues to widen.

The second episode of extension, the mid-Miocene to Quaternary phase, began about 17 million years ago and continues today. The most rapid phase of regional extension was during this period, from middle to late Miocene time. Evidence of continuing rifting includes young fault scarps, seismiscity, high heat flow, and ongoing uplift as established by geodetic measurements.

Rift Volcanism
The onset of rifting coincided with a period of intense volcanism associated with the early rift basins - as is common in other rift valleys of the world. As extensional forces continued and the crust beneath the widening rift zone was thinned, magma surged to the surface. Most of the volcanism was concentrated on the western side of the Rio Grande rift, where immense eruptions spewed ash over the region. In some areas magma flowed onto the surface and created vast lava fields. Some lavas flowed quietly from vents, forming broad flows that accumulated in layers to form expansive, gently sloping shield volcanoes. In other areas thick lava flows eventually built up to form major mountains. Huge calderas were created when the volcanoes collapsed into vacated magma chambers beneath the volcanoes. Much of the lava is basaltic, evidence that the faults along the rift reach down to the mantle, the source of most basaltic magma (Lipman and Mehnert, 1975).

Smaller volcanic eruptions, some of them within the last few thousand years, have added cinder cones, flows of dark basalt, squeeze-ups, and lava tunnels to the area. These volcanic episodes may have been witnessed by some of North America’s early human inhabitants – Clovis and Folsom Man. It is thought that early man may have witnessed the eruption that formed the Capulin cinder cone at what is now the Capulin Mountain National Monument in northern New Mexico. Capulin Mountain is near the center of the Raton-Clayton volcanic field, which is related to the Rio Grande rift (Stormer, 1987).

The intense volcanic activity along the Rio Grande rift fractured the nearby rocks and permitted the movement of superheated, mineral-rich solutions that formed hydrothermal deposits. These deposits brought in a later group of human inhabitants – the prospectors and miners. Most of New Mexico’s mining districts with their deposits of gold, silver, lead, copper, zinc, molybdenum, fluorite, and barite are concentrated along this mineralized trend near the edges of the Rio Grande rift.

Basins
The Rio Grande rift first developed as a chain of closed basins or half grabens (trench-like features formed by down-dropped blocks of crustal rocks), which gradually filled with lava, ash flows, and sediments that washed in from nearby mountain ranges. Large amounts of sand, gravel, lava, and volcanic ash fill the rift basins to a depth as great as 7.3 kilometers. Sedimentation began in most rift basins in late Oligocene to early Miocene time; however, the basin fill deposits of middle to late Miocene age are dominant in volume. The sedimentary and volcanic deposits of the Rio Grande rift are collectively known as the Santa Fe Group. The Santa Fe Group includes fine to coarse-grained sandstone interbedded with siltsone, conglomerate, and volcanic material. The sediments are generally soft and easily eroded.

Today, starting near Leadville, Colorado and southward to Soccorro, New Mexico, a distance of 550 kilometers, the north-trending rift consists of a series of four en echelon (staggered) basins that join. These basins range from 80 to 240 kilometers in length and from 5 to 95 kilometers in width. The average basin width is 50 kilometers (Chapin and Cather, 1994).

Satellite Image of northern extension of the Rio Grande Rift starting
 near Leadville, Colorado.Image courtesey of NASA.
From north to south these basins are the Upper Arkansas, San Luis, Española, and Albuquerque Basins. The Upper Arkansas Basin is the least understood of the basins as seismic profiles and deep drill hole studies are not available. Rift sedimentary deposits in the Upper Arkansas Basin are named the Dry Union Formation. The best exposures are in the Salida, Colorado area at the south end of the basin. The Dry Union Formation, 1,500 meters thick, contains vertebrate fossils of very late Miocene age (Halley, 1978).

The San Luis Basin is 75 kilometers wide and 160 kilometers long, with the deepest part of the rift just northwest of the Great Sand Dunes National Monument in south central Colorado. The basin is filled with 6.4 kilometers of sediments, mostly Oligocene in age or younger, from the Sangre de Cristo Mountains. The Alamosa basin is the northern part of the San Luis Basin, and is bordered by the San Juan Mountains to the west and the San Luis Hills to the east. The San Luis Hills are erosional remnants of a once extensive volcanic field.


Satellite image of San Luis Valley. Image courtesy of NASA.

South of the Colorado-New Mexico state line is the Taos Plateau, the southern subdivision of the San Luis Basin. This region of broad plains is underlain by basalt. The mountains and hills on the plateau are volcanic features. The Taos Plateau is trenched by gorges of the Rio Grande. Where the Rio Grande Bridge crosses U.S. 64, the Rio Grande is entrenched 185 meters below the bridge and the gorge is 370 meters wide. The gorge cuts into the Serrvilleta Formation (Pliocene), a sequence of coarse-grained and vuggy basalt flows that erupted as highly fluid pahoehoe lava that traveled many kilometers and formed individual units only a few meters thick.

Satellite image of the Taos Plateau. Note extinct volcanic cinder cones
at lower end of the image.  Image courtesy of NASA.
The Española Basin extends 40 kilometers north to south and 64 kilometers east to west. The western half of the basin is a volcanic field; Tertiary sediments fill the remaining portions. The basin ends near the Cerros del Rio volcanic field to the south. The Española Basin, tilted by faulting, contains the Barrancas or badlands, which are carved on volcanic ash deposited before the Rio Grande became a through-flowing river. This volcanic ash weathers to clay that erodes easily to form the badlands. Deposits of the Barrancas contain fossils of extinct mammal, ancestral horses, deer, camel, and bears that thrived here in the early days of the Rio Grande rift. Hot, mineralized water rises along a fault in the Española Basin and surfaces at the hot springs of Ojo Caliente – a site visited by early Indians.

The Albuquerque Basin is one of the largest and deepest basins of the Rio Grande rift. The width varies from about 20 kilometers in the north to 60 kilometers of sediments in the central region. The deepest part of the basin is filled by 7.3 kilometers of sediments.

South of the Albuquerque Basin the rift branches out and widens into a pattern of tilted ranges and parallel basin that resembles the Basin and Range province. Some researchers consider the rift south of the Albuquerque Basin to be part of the Basin and Range province. Others feel the Rio Grande rift should be distinguished from the adjacent Basin and Range province on the basis of its high heat flow, more frequent Pliocene and Quaternary faulting, deep basins, and late Quaternary volcanism (Chapin and Cather, 1994).

Summary
The Rio Grande Valley is not a usual valley – it was not cut by a river and does not branch upstream, as do most river valleys. The Rio Grande, instead, followed a pre-established and partly filled rift valley. The Rio Grande rift is geologically young and resulted from a process of regional extension and mantle upwelling in Neogene times. The Rio Grande rift continues to widen today, and ongoing geologic activity is evident through high heat flow, hot springs, continued siesmicity, geodetic observations, and some of North America's most recent lava flows.

Acknowledgments
Donald A. Coates provided critical review, which improved this paper.


References Cited:

Chapin, Charles E., and Cather, Steven M., 1994, Tectonic setting of the axial basins of the northern and central Rio Grande rift, Geological Society of America Special Paper 291

Halley, J.W., 1978, Guidebook to Rio Grande rift in New Mexico and Colorado, New Mexico Bureau of Mines and Mineral Resources, Circular 163

Lipman, P.W. and Mehnert, H.H., 1975, Late Cenozoic basaltic volcanism and development of the Rio Grande depression in the southern Rocky Mountains: Geological Society of America, Mem. 14

Stormer, John C. Jr., Capulin Mountain volcano and the Raton-Clayton volcanic field, northeastern New Mexico: Geological Society of America Field Guide – Rocky Mountain Section