Arizona geology

New releases from the Arizona Geological Survey – September 2017

The Arizona Geological Survey is in the process of digitizing both new and older geological reports and releasing them to the public as free downloads.

This month they released a classic work by E.D. Wilson et al.: “Arizona Lead and Zinc Deposits, Part 1″ which was originally published in 1950. (146 p., 19 plates)

Download it here: http://repository.azgs.az.gov/uri_gin/azgs/dlio/1729

They have also released an index of mining properties in Santa Cruz County, Arizona (100 pages). http://repository.azgs.az.gov/uri_gin/azgs/dlio/1730

 

Previous releases available for free down include:

(Note: some of these links take you first to my review of the papers.)

 

A guide to the geology of the Sedona & Oak Creek Canyon area of Arizona

A Guide to the Geology of the Santa Catalina Mountains

A Guide to the Geology of Organ Pipe Cactus National Monument and the Pinacate Biosphere Reserve

A Guide to the Geology of the Flagstaff Area

A Guide to Geology of Petrified Forest National Park

A Guide to Oak Creek-Mormon Lake Graben

AZGS Guides to Northern Arizona Geology

AZGS field guides to Arizona Geology

Eldred Wilson’s Proterozoic Mazatzal Revolution Arizona

 

History of the Ajo Mining District, Pima County, Arizona

History of the Warren (Bisbee) Mining District

History of the San Manuel-Kalamazoo Mine, Pinal County, Arizona

Recovery of Copper by Solution Mining Techniques

Superior, Arizona – An Old Mining Camp with Many Lives

History of the Copper Mountain (Morenci) Mining District

History of Helvetia-Rosemont Mining District, Pima County, Arizona

History of the Silver bell mining district

 

 

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Roadside Geology – Wupatki and Sunset Crater Volcano National Monuments

The Arizona Geological Survey has just released another booklet in its “Down to Earth” series.

Sunset crater cover

The geologic setting in Wupatki National Monument is distinctly different from that in Sunset Crater Volcano National Monument, even though the monuments are side by side. At Wupatki, sedimentary rocks that were deposited by ancient seas and river systems more than two hundred million years ago during the Permian and Triassic Periods dominate the landscape.

The landscape at Sunset Crater is dramatically different. Although underlain by the same rocks

exposed at Wupatki, the Sunset Crater area is covered with cinders and cooled lava flows from intermittent volcanic eruptions during the last few million years. The most recent eruption was that of Sunset Crater Volcano, only about 900 years ago.

Sunset crater map
This guide provides only a glimpse of what can be found in these areas. By hiking the trails and perusing the displays at the Visitor Centers, you will get a much more in-depth view of the monuments.

Most visitors to these monuments travel north from Flagstaff, enter Sunset Crater Volcano National Monument, and drive north on the Loop Road to Wupatki. This road log, therefore, is organized to follow the Loop Road in that direction.

You can download the 36 -page booklet (34Mb) here:

http://repository.azgs.az.gov/sites/default/files/dlio/files/nid1527/dte-15_wupatki_and_sunset_crater-ocr.pdf

 

For other booklets in this series see:

https://wryheat.wordpress.com/2016/07/27/azgs-down-to-earth-series-available/

AZ Geological Survey to release County geologic maps online

In 1959 and 1960, The Arizona Bureau of Mines – University of Arizona, predecessor to the Arizona Geological Survey published the Arizona County Geologic map series. Until now, these important maps were only available in printed form.

Over the next two weeks, The Arizona Geological Survey will release the maps online for free download. The map scale is 1:375,000 and the contour interval is 500 feet.

You can check their facebook page for release announcements:

https://www.facebook.com/AZ.Geological.Survey

So far AZGS has release maps for:

Apache and Navajo counties: http://repository.azgs.az.gov/uri_gin/azgs/dlio/1618

Coconino County: http://repository.azgs.az.gov/uri_gin/azgs/dlio/1620  A portion of this map is shown below.

These maps are valuable in that they give the big picture of County and State geology. For a list of all maps available for download, see: http://repository.azgs.az.gov/facets/results/maps

Coconino county geologic map

 

 

 

Arizona Oil and Gas well viewer now online

The Arizona Geological Survey has developed an Arizona Oil & Gas Well viewer for about 1,100 wells in Arizona. The viewer is hosted at the Arizona Oil and Gas Conservation Commission site, which piggybacks on AZGS.  The viewer is at http://welldata.azogcc.az.gov/

The viewer presents a scalable map showing location of wells within the state.  Clicking on any well brings up basic information and links to various downloadable data.  An example is shown in the graphic below.

AZ-oilgas-viewer

The AZGS says it purchased Neuralog software in 2011 to digitize Arizona well logs into LAS (log ASCII Standard) format to aid analysis for CO2 sequestration potential. The digitizing effort focused on deep wells across northeastern Arizona including wells that penetrated Precambrian basement and wells in the oil and gas fields with the highest cumulative production. The AZGS developed a user-friendly web application to make the digitized well data available online to facilitate the widest possible access and use of the data. The search and download map includes more than 1100 well folders, 2500 scanned tiff images of well logs, and the newly digitized LAS data.

Steve Rauzi, Oil & Gas specialist at AZGS says, “The viewer is user friendly and makes it simple and easy to access and download oil and gas data in Arizona including well files, scanned tiff images of logs, and log ASCII standard (LAS) digital data. The oil and gas data is useful in a broad range of investigations including oil and gas, geothermal, mining, environmental, and hydrologic studies.”

I have been playing with the viewer and agree with Rauzi’s statement.

Just about two weeks ago, AZGS made available Arizona’s first online Natural Hazard Viewer.

This new viewer is part of an AZGS program to make information readily available to the public. The two new viewers complement the AZGS online document repository where hundreds of reports and maps are available.

Arizona Geological Survey celebrates its 125th anniversary

Interest in geology and mining is an integral part of Arizona history. In 1888, the Arizona Territorial Legislature appointed John Blandy as Territorial Geologist. From that point, what became AZGS grew under several names from the University of Arizona Bureau of Mines (1893 – 1915), Arizona Bureau of Mines (1915 – 1977), and the Arizona Bureau of Geology and Mineral Technology (1977 – 1988), to the Arizona Geological Survey (1988 to present).

To help celebrate this anniversary, AZGS has created a special webpage:

http://www.azgs.az.gov/125th-anniversary-azgs.shtml

Included on that page is “Geosnaps – Image of the Day” a new photo every day depicting some aspect of Arizona geology or mining history.

Some other features will include:

Arizona Mining Review – a monthly webinar hosted by State Geologist Lee Allison to discuss Arizona mining – past, present and future.

Release of new & old geologic products bearing the 1888 – 2013, 125th anniversary logo.

Timeline graphic demarcating milestones in the history of Arizona geology.

A retrospective review on the state of geology of Arizona ca. 1888. Arizona Geology Magazine 125th year anniversary issue.

125th anniversary field trip(s).

Beginning January 23, there is the “Arizona Mining Review” with news and updates on the state of Arizona mining. Each month they will introduce a new topic and select a format – featured guest, panel discussion, Q&A session – to draw the most out of the topic.

Visit the anniversary site often.

Earthquake hazard near Flagstaff assessed, Video

Flagstaff, Arizona sits in the middle of the San Francisco volcanic field and at the northern end of the Lake Mary fault which poses a potential earthquake hazard for the city. The Lake Mary fault (yellow lines in map below) extends about 25 miles from Mormon Lake in the south into the city of Flagstaff on the north.

Lake-mary-fault-overview

Dr. David Brumbaugh, Arizona Earthquake Information Center (AEIC) at Northern Arizona University, estimates that there is 50% chance for a magnitude 6.9 to 7.0 earthquake sometime in the next 30 years.  Such an earthquake could do great damage especially to older structures in town.  Three such earthquakes have occurred in the region between 1906 and 1912.   A swarm of very small quakes occurred along the fault this past June.

Flagstaff lies astride the Northern Arizona Seismic Belt and is considered second only to Yuma,  Arizona for potential seismic hazard.

The Arizona Geological Survey is currently featuring a 5-minute video by Dr. Brumbaugh which explains the geology and the hazard at Flagstaff. (Link to video).

The Arizona Geological Survey has two featured sections near the bottom of its webpage dealing with earth fissures and earthquakes.  Take a look at the earthquake hazards page here for some information on past Arizona earthquakes.

 

Arizona Geology: earthquakes, potash and education

The Arizona Geological Survey has just released its newest issue of Arizona Geology Magazine. This issue features photos of earth fissures in Cochise County and an update on seismicity in Arizona. Seismometers recorded 17 earthquakes in Arizona from January to March.

Also featured is “SCINEWS” a link between classroom content and everyday life through the use of science current events. This adds relevancy to science education.

The new issue presents a summary of oil and gas activities in Arizona. Included within that article is a report on Potash mining. What’s that? Potash is potassium salts used mainly for fertilizers. Exploration is being conducted west of Petrified Forest National Park near Holbrook. Mining is usually by in situ solution extraction rather than digging holes.

Also featured  are papers on evaluation of basins for carbon dioxide sequestration and geothermal potential.

There are also links to new, downloadable publications. One not to miss is a paper on geological hazards in Sabino Canyon. You can see the whole issue here.

Arizona Geological History Chapter 7: The Cenozoic Era

Cenozoic Era, Arizona was squeezed, then stretched; steamed and frozen.

The Cenozoic era represents the most recent 65 million years. (See the geologic time chart for the subdivisions.)

Paleomap 50

 

Construction of the Rocky Mountains, volcanism, and emplacement of our major copper deposits, all of which began in Cretaceous time,  continued in the Cenozoic Era until about 40 million years ago.   During this time, the oceanic crust of the Pacific Ocean was being subducted beneath the westward-moving North American continental plate.  The resulting compression caused southern and western Arizona to be topographically higher than the Colorado Plateau, the opposite of current topography.

The compression produced large thrust faults which led to mountain building. The Front Range of the Rocky Mountains in Colorado has a structure similar to the diagram below.

blindthrust

 

 

By about 20 million years ago, Arizona was covered with thousands of feet of volcanic rocks, locally punctured by calderas.

The photo below (from the Arizona Geological Survey) shows erosional remnants of a volcanic ash-flow in the Chiricahua Mountains. These rocks were expelled from the Turkey Creek caldera 27 million years ago. The spire forms, called “hoodoos,” result from mass wasting by ice and water.

Hoodoo

 

Sometime between 30- and 20 million years ago the north American tectonic plate overrode a spreading center called the East Pacific Rise. This area is similar to the spreading center of the Mid-Atlantic ridge that gradually separated Africa from South American, and Europe from North America. Today, this western spreading center runs up the Gulf of California and separates Baja from mainland Mexico. It is also the driver of the San Andreas fault in California. By over-riding the spreading center, the tectonic regime changed from compression to extension. Arizona began to be pulled apart to form the Basin and Range physiography of today.

Initially, crustal extension was characterized by widespread normal faulting and fault-block rotation. Movement occurred along high-angle normal faults some of which may flatten at depth into low-angle detachment faults. Later extension resulted in high-angle faults which bound our valleys and make some of the valleys as much as 15,000 feet deep to bedrock.

NormalFault

Detachment fault from Arizona Geology

All of this faulting sometimes makes the life of exploration geologists very interesting when hunting for porphyry copper deposits, because some of those deposits were cut and fanned out like a deck of cards. Finding all the pieces takes some geologic detective work.

Perhaps the most famous local case of geological detective work is that of John Guilbert and David Lowell who studied the San Manuel mine north of Tucson. They noticed that the arrangement of mineralization and alteration formed shells around the generating intrusive. But the model they constructed implied that the deposit was lying on its side, and half of it was missing. It was removed by faulting. By applying their model, Lowell and Guilbert found the other half.

South of Tucson, the Mission-Pima mine and the San Xavier mine seem to be slices removed from top of the Twin Buttes deposit by low-angle faulting.. The Sierrita mine, located on the opposite side of a major high-angle fault from Twin Buttes is still intact (we think).

Middle Cenozoic veins host gold, silver, and base-metal deposits. Copper-gold mineralization is associated with the detachment faults. Manganese and uranium deposits occur in the basins resulting from the extension.

Volcanic activity resumed 2- to 3 million years ago with eruption of basalt which produced flows and cinder cones (see map below). The rocks of the San Francisco volcanic field near Flagstaff, the Springerville-Show Low field, the San Bernardino field east of Douglas, and the Pinacate field in Mexico are examples of this episode. The most recent volcanism was at Sunset Crater near Flagstaff. It erupted about 1,000 years ago. The San Francisco field is considered active and the most likely place in Arizona to have another eruption. The map below, from the Arizona Geological Survey shows the extensive Cenozoic volcanism.

Volcanic-AZ-young

The Grand Canyon was formed during the late Cenozoic. The Colorado Plateau initially tilted to the northeast and rivers, including the ancestral Colorado River, flowed in that direction into Utah and Colorado. Beginning about 18 million years ago, crustal stretching formed the Basin and Range province west and south of the plateau. Also around this time, plate tectonic adjustment began to tilt the Plateau toward the southwest. Sometime around 10 million years ago, plate tectonic movement began to open the Gulf of California and a river at its north end began to cut northward. At about the same time, the northeastward flowing rivers of the Colorado Plateau reached the southern escarpment of the plateau and began to flow south forming lakes along what is now the course of the Colorado River. Actual cutting of the Grand Canyon probably began about 5.5 million years ago.

Climate in the early Cenozoic continued to be hot and steamy, about 18̊F warmer than today, even though atmospheric carbon dioxide had been decreasing for 80 million years due to coal formation in the Cretaceous. Around 55 mya, there was a sudden temperature spike that lasted for about 100,000 years. (That’s geologically sudden = 10,000 years.) The spike is known as the Paleocene-Eocene Thermal Maximum (PETM). Data, derived from drill cores brought up from the deep seabed in the Atlantic and Pacific Oceans, show that the surface temperature of the planet rose by as much as 15̊F over the already warm temperatures. The cause is controversial.

Carbon dioxide levels rose from 1000 ppm to 1700 ppm–more than four times higher than today’s level of 400 ppm, but that rise began after the start of the temperature spike.

Isotopic analysis of carbon suggests that the culprit was methane, which is 65 times more powerful as a greenhouse gas than carbon dioxide. There are two hypotheses as to the source of methane: microbially generated methane buried in sediments along the slopes of the continental shelves; and methane clathrates. Methane clathrates are crystalline structures of methane bound to water. They form at near freezing temperatures under high pressure. They are stable up to 64̊F under high enough pressure. This form of methane exists along our coasts today, frozen in the sediment at low temperatures and high pressures. They are being investigated as a source of energy.

It is speculated that volcanism and tectonic disturbance released pressure that was holding the methane in clathrates or in sediments themselves. This “sudden” release of methane caused the temperature spike. (There is nothing to prevent this from happening again.)

After that temperature spike subsided, temperatures remained warm until about 34 mya when global temperatures began to drop. Antarctica had separated itself from Africa, Australia, and South America which caused the southern circumpolar ocean current to be established which isolated Antarctica from warm tropical waters. Global temperatures continued to drop. About 2.6 mya, continental ice formed at lower latitudes and initiated the glacial epochs and interglacial periods of our current ice age.

References:

Shellito, Cindy, 2006, Catastrophe and Opportunity in an Ancient Hot-House Climate, Geotimes, October 2006.

In Arizona Geological Society Digest 17:

Lucchitta, Ivo, 1989 History of the Grand Canyon and of the Colorado River in Arizona.

Lynch, D.J., 1989, Neogene volcanism in Arizona.

Menges, C. M., 1989, Late Cenozoic Tectonism in Arizona and its impact on regional landscape evolution.

Pearthree, P., House, K., (now with USGS), and Perkins, M., Stratigraphic evidence for the role of lake spillover in the inception of the lower Colorado River in southern Nevada and western Arizona, Geological Society of America Special Paper 439

Scarborough, R., 1989, Cenozoic erosion and sedimentation in Arizona.

 

Arizona Geological History Chapter 6, The Cretaceous Period

The Cretaceous Period (145- to 65 million years ago) was hot and steamy. There was no ice at the poles. Global temperature is estimated to have been about 18 F warmer than today. Atmospheric carbon dioxide began a 145-million-year decline from about 2,000 ppm to the 380 ppm of today, in part, due to carbon sequestration by formation of coal deposits. Flowering plants appeared.

Paleomap 94

The North American continent was split by a sea connecting the Gulf of Mexico with the Arctic Ocean. Transgressions and regressions of this sea formed conditions ripe for coal formation similar to those in the Paleozoic Era In Southern Arizona, the lower Cretaceous Bisbee Group, consisting of the basal Glance conglomerate, the Morita formation sandstones and mudstones, the distinctive Mural Limestone (which forms the cliffs just east of Bisbee), and the sandstones and mudstones of the Cintura Formation record the changes in sea level. Upper Cretaceous rocks, the Fort Crittenden Formation lie unconformably (representing erosion or structural change) upon the Bisbee Group. The lower Fort Crittenden is dominated by marginal wetland to deep-water lake deposits, whereas the upper Fort Crittenden is characterized by wetland to deltaic deposits. These rocks contain organic geochemical evidence of wildfires which suggest that seasonal aridity and wildfires were common occurrences.

There are no early Cretaceous rocks recognized in northern Arizona. Thick sequences of upper Cretaceous rocks were deposited on what is now the Colorado Plateau. These represent near-shore marine, coastal, and river-deposited sands, mudstone, and coal. Coal is mined from the Dakota sandstone at Black Mesa in Navajo County, AZ. This is overlain by the Mancos Shale, and several other sedimentary formations.

The Laramide orogeny of late Cretaceous to early Tertiary time (80- to 40 million years ago) built the Rocky Mountains and closed the inland Cretaceous sea. Subduction of oceanic crust under continental rocks along the west coast caused compression and uplift of the continent.

This was the time of emplacement of most of the porphyry copper deposits in the western U.S. Volcanism was extensive, and included the volcano that produced the rocks of the Tucson Mountains.

sonorasaurusDinosaurs roamed the land, including Arizona’s Sonorasaurus thompsoni, a new species of brachiosaurid dinosaur whose remains were first discovered in the Whetstone mountains by UofA graduate geology student Richard Thompson in 1994. Sonorasaurus is estimated to have been about 50 feet long and 27 feet tall, about one third of the size of other brachiosaurus. It may have been a juvenile or just a small dinosaur species. Sonorasaurus was an herbivore. Tooth gouges on its bones suggest it was killed and eaten by a larger dinosaur. A single blade-like tooth of a huge meat eater called Acrocanthosaurus was found near the bones and suggests that this was the predator that killed Sonorasaurus. You can see an exhibit dedicated to Sonorasaurus at the Arizona-Sonora Desert Museum.

The end of the Cretaceous Period saw another major extinction of life. Dinosaurs, pterosaurs, many marine reptiles, some marine invertebrates, some groups of mammals, and a few plant groups became extinct. The reasons are still controversial. We know that an asteroid impacted near Yucatan, Mexico and formed the Chicxulub crater about 65 million years ago. The impact is said to have vaporized rock into clouds of dust, that cooled temperatures, and created clouds of sulfurous gas, which may have killed plants with acid rain. The impact is also said to have deposited a thin clay layer containing iridium and strained quartz. However, the extinction occurred during an 800,000-year eruption of basalts that form the Deccan Traps in India. Volcanic eruptions can also product dust and sulfur dioxide emissions (and layers of iridium which characterize the K/T boundary). More precise dating shows that the Chicxulub impact occurred 300,000 years before the mass extinction. Evidence suggests that the extinctions occurred over a period of several million years.

Cretaceous Trivia:

The white cliffs of Dover, England are Cretaceous age chalk deposits.

Paul Spur, a rail stop between Bisbee and Douglas exists because Mural limestone was mined for smelter flux.

Mural Hill Bisbee 1902

Hills carved from Cretaceous beds east of Bisbee. View is northward across Mule Gulch. The prominent white band is the upper member of the Mural limestone, forming the top of Mural Hill on the left and showing the dislocation due to the Mexican Canyon fault. Cochise County, Arizona. December 1, 1902. Plate 9-B in U.S. Geological Survey. Professional paper 21. 1904, figure 7 in U.S. Geological Survey Folio 112. 1904.

References:

Dickinson, W.R., et al., 1989, Cretaceous Strata of Southern Arizona, in Geologic Evolution of Arizona, Arizona Geological Society Digest 17.

Finkelstein, D.B, et al., 2005, Wildfires and seasonal aridity recorded in Late Cretaceous strata from south-eastern Arizona, USA, Sedimentology, Volume 52, Issue 3 , Pages587 – 599, International Association of Sedimentologists

Krantz, R.W., 1989, Laramide Structures of Arizona, in Geologic Evolution of Arizona, Arizona Geological Society Digest 17.

Nations, J.D., 1989, Cretaceous History of Northeastern and East-Central Arizona, in Geologic Evolution of Arizona, Arizona Geological Society Digest 17.

Arizona Geological History Chapter 4: Triassic Period

With this chapter we begin the Mesozoic (middle life) Era which extended from 251 million years ago to 65 million years ago. The Mesozoic is divided into three Periods: the Triassic (251- to 202 million years ago), the Jurassic (202- to 145 mya), and the Cretaceous (145- to 65 mya).

The preceding Paleozoic Era (542- to 251 mya) ended with a mass extinction and with most of the landmass forming a massive continent called Pangea. Arizona was just barely north of the equator, and once again, emerging from the sea which still existed in California and Nevada.

Paleomap 237

By Triassic time, dinosaurs, pterosaurs (flying reptiles), lizards, mammals, and possibly even the earliest birds, had all evolved from Permian stock. In Arizona, there were Phytosaurs, crocodile-like animals (2- to 12 meters long) which inhabited streams and ponds.

Triassic sedimentary rocks, well-exposed on the Colorado Plateau, are represented by the Moenkopi Formation and the Chinle Formation. The Moenkopi consists of continental redbeds (sandstones, shales, and conglomerates) in the northeastern part of the plateau, and minor mixed carbonates of fluvial (river), tidal flats, and shallow marine origin in the west. After a period of erosion, continental sandstones, mudstones, and lake-formed carbonates of the Chinle Formation were deposited. Most Triassic sediments represent deposition well-inland from the sea. The climate was semi-arid in the interior and wet and swampy in the lowlands. Temperatures were 15 -to 20 F warmer than today.

Petrified1

Southern Arizona was a major volcanic province. Many of the mountain ranges contain Triassic volcanic rocks. In the Santa Rita Mountains, for instance, almost 10,000 feet of volcanics were deposited. The Recreation Redbeds in the Tucson Mountains represent an inter-volcanic period of erosion in upper Triassic time.

Volcanism and the high-energy continental deposits made poor hosts for fossils of terrestrial animals and plants. However, the Chinle Formation contains the silicified trunks of large trees preserved and exposed in the Petrified Forest of Arizona, and colorful Chinle rocks are exposed in the Painted Desert.

In mid-Triassic time, the mega-continent of Pangea began splitting into two parts: Gondwana (South America, Africa, India, Antarctica, and Australia) in the south and Laurasia (North America and Eurasia) in the north. This split caused massive volcanism along a rift that would become the Atlantic Ocean.

The Triassic Period ended with another mass extinction of about 76% of marine species and some terrestrial species. Again, the reason is not known, but speculative theories attribute it to comet impacts and volcanism. According to The Resilient Earth: ” At least two impact craters have been found from around the time of this extinction. One is in Western Australia, where scientists have discovered the faint remains of a 75 mile (120 km) wide crater. The other is a 212 million year old crater in Quebec, Canada, forming part of the Manicouagan Reservoir. The Manicouagan impact structure is one of the largest impact craters still visible on the Earth’s surface, with an original rim diameter of approximately 62 miles. Others have suggested that a sudden, gigantic overturning of ocean water created anoxic conditions causing the massive die-off of marine species.”

 

Blakey, R.C., 1989, Triassic and Jurassic Geology of the Southern Colorado Plateau, in Geologic Evolution of Arizona, J.P. Jenney and S. J. Reynolds, eds. Arizona Geological Society Digest 17.

Hayes, P.T. and Drewes, Harald, 1978, Mesozoic Depositional History of Southeastern Arizona, in Land of Cochise, New Mexico Geological Society Guidbook 29.

Moore, R. C., 1958, Introduction to Historical Geology, McGraw-Hill.