American Geosciences Institute’s Critical Issues program


The Arizona Geological Survey’s winter e-magazine features an article about the American Geosciences Institute’s Critical Issues program (

The aim of this AGI program is to pioneer a new approach to sharing societally-relevant science with state and local decision makers. “Here in Arizona, we are sharing this with state and local decision-makers to help them wrap their heads around the complex issues involving groundwater, geologic hazards, and sustainable natural resource management.”

The program aims to support connections and communication between the geoscience community and decision makers. Although the program caters to decision makers at all levels, it particularly focuses on state and local decision makers because these stakeholders are commonly underserved by geoscience policy efforts.

The program convenes meetings, such as the AGI Critical Issues Forum, but its main interface is a web-based platform of resources that bring the expertise of the geoscience community to decision makers by offering a curated selection of information products from sources that include state geological surveys, federal and state agencies, and AGI’s member societies.

The Critical Issues program offers the following freely accessible information services:

Research database: Over 4,000 publications primarily from state geological surveys and the U.S. Geological Survey.

Webinars: Free webinars on a variety of topics that bring geoscientists and decision makers together to discuss potential solutions to challenges at the interface of geoscience and society.

Maps & Visualizations: 144 interactive maps and visualizations covering all 50 states and the District of Columbia.

Case studies: A new product that is coming online in Spring 2017. Specific applications of geoscience to societal problems.

Fact Sheets: A new product that is coming online in Spring 2017. Provide more in-depth information on the big issues.

Frequently Asked Questions: 105 questions on topics including: climate, energy, hazards, mineral resources, and water.

Read more at:

This AZGS e-Magazine also includes an article about groundwater use in the United States.


Caliche – natural concrete, can you dig it?

Caliche 3
If you try to dig a hole in your yard in Tucson, chances are that you will soon hit a very hard, almost impenetrable layer.
The term “caliche” is a colloquial word that means different things in different places. In the Sonoran Desert, it means a mixture of gravel, sand, clay and other desert debris cemented by porous calcium carbonate and is  more properly called a calcic horizon. These calcic horizons generally occur two to four feet below the surface and can be inches to many feet thick. Caliche forms only in arid and semi-arid areas. In Tucson, with an average annual rainfall of 10 to 12 inches, caliche forms more than ten inches below the surface. In contrast, in Yuma, which receives about four inches of rain annually, caliche may form at the surface or just a few inches below the surface.
Caiche formation
According to the Arizona-Sonora Desert Museum:
“Thick, strongly-cemented calcic horizons take a long time to form. They start as thin, patchy coats of whitish calcium carbonate on the lower surfaces of pebbles and small stones. In fine-grained parent materials, such as dune sand, that lack coarse materials, calcium carbonate first appears as thin, white, thread-like accumulations where small roots have extracted soil water and caused the calcium carbonate to precipitate. These weakly-developed calcic horizons can form within a few thousand years. Accumulation of more calcium carbonate eventually produces thicker, continuous coatings on pebbles and stones or pronounced whitish nodules in fine-grained parent materials. Eventually, additional accumulation of calcium carbonate fills the soil interstices between pebbles or nodules and the calcic horizon becomes plugged, greatly restricting the downward movement of water. Once this occurs, calcium carbonate may continue to accumulate on the top of the calcic horizon in hard, cemented layers and may literally engulf and obscure overlying soil horizons in the process. It takes many tens to hundreds of thousands of years for such strongly-developed calcic horizons to form.” (Source)
Caliche can form in soil developed from rocks that have little or no calcium carbonate. The calcium carbonate is derived from dust in the atmosphere and from calcium carbonate dissolved in rainwater. Dust that falls on the ground is gradually dissolved as the slightly acidic rainwater penetrates the surface. Calcium carbonate precipitates out of solution as the soils dry and provides the cement to hold the soil particles together to form the concrete-like calcic horizon.
In very arid regions, calcium sulfate (gypsum) and sodium chloride (salt) is formed instead of calcium carbonate. In the Atacama Desert of Chile, caliche also contains sodium nitrate and potassium nitrate. Nitrate, a major ingredient of explosives, was mined and exported to Europe. The importance of this source of nitrate lead to naval battles between Germany and England at the start of WWI. (Source)
In many parts of the world, caliche is used as road pavement or underlayment. It is also used as a source of calcium for manufacture of cement.
The ancient Mayan culture used caliche for building construction.
Caliche layers can be a problem for agriculture and gardening, mainly by preventing drainage. The University of Arizona College of Agriculture has some helpful advice here. Basically they recommend that if you can’t dig through all of the caliche, at least punch some drainage holes in it.

A Guide to the Geology of the Santa Catalina Mountains

Cover santa catalina mtnsThe Arizona Geological Survey (AZGS) has just released a new publication that is available for free download here:
The paper citation is: “Bezy, J.V., 2016, A Guide to the Geology of the Santa Catalina Mountains, Arizona: The Geology and Life Zones of a Madrean Sky Island. Arizona Geological Survey Down-to-Earth # 22, 83 p
The description from AZGS:
This is a non-technical treatment of the geology and ecology of the Santa Catalina Mountains, Tucson, Arizona. Natural landscapes have distinctive personalities. Each is the product of the interplay of geology, climate, vegetation, time, and often, human activities. The landscapes that form the Santa Catalina Mountains of southeastern Arizona give that range a unique personality like no other in the American Southwest. Rising as a great mountain island to over 9000 feet in elevation at their summit, Mount Lemmon, the Santa Catalina Mountains are the greatest expanse of high country within the Sonoran Desert. An unusual dome-like profile  sets it apart from the numerous, steep, sharp-crested mountain ranges in the region. This distinctive profile is a legacy of the range’s remarkable geologic history and the structure of its bedrock. Formed miles deep within Earth’s crust before being exhumed, this ancient structure has guided surface weathering and erosion for millions of years. The result is a mosaic of mountain landscapes of singular beauty and complexity.
This publication contains some 83 spectacular photos and figures.  It gives a very good introduction to the geology and geological processes that formed the range and also describes its life zones.
The rocks in the Santa Catalina Mountains record 1.65 billion years of history. The publication is written for both the general public and geologists.  Take a look and gain an appreciation of that history for when you travel the mountains.

AZ Geological Survey makes 20,000 documents available for free

Unpublished one-of-a-kind Arizona mining documents – once filed away in cabinets and cardboard boxes – are now online, discoverable, and accessible at the Arizona Geological Survey Mining Data website (

More than 20,000 files, maps, and reports contributed by dozens of exploration geologists and mining firms are now available. The website exposes more than 8,500 geologic and engineering reports; 6,800 maps – geologic maps, mining claim maps, maps with assays, plats, underground maps and cross sections; and 5,500 historic photographs dating from the 1890s to 2000.

“The ability to deliver such a large volume of historical mining maps and documents to the public, free of charge, fills a critical need for bolstering mining efforts in Arizona. It provides an invaluable resource for planning future mineral exploration efforts.” according to Lee Allison, State Geologist and Director of the Arizona Geological Survey.

This new online resource is being premiered in time for the 2016 Society for Mining, Metallurgy & Exploration Annual Conference and Expo in Phoenix from Feb. 21 – 24. The collection includes major exploration holdings from the Arizona Department of Mines and Mineral Resources, Walter E. and Grover Heinrichs, James Sell, A.F. Budge Mining Ltd., Cambior Exploration, among many others.

Since the 1850s, Arizona has been a mecca for prospectors, exploration geologists and mining firms seeking copper, gold, silver, molybdenum, zinc, lead, manganese, tungsten, uranium, and coal, turquoise and semi-precious gems. Collectively, they left a mile-high paper trail of hundreds of thousands of pages, tens of thousands reports, well logs, letters, photographs, and geologic and mine maps.

The documents comprising this online repository were originally provided to the Arizona Mines and Mineral Resources Department by exploration geologists and mining firms.

The Mining Data site includes an applied search tool filtered by key words, mine names, collections, time and place. The geographic search tool provides for a radius search of 1 to 100s of miles from a point of interest for these georeferenced data.


New Release – AZGS field guides to Arizona Geology

The Arizona Geological Survey has just e-published field guides to Arizona geology. The 422-page series of illustrated guides is available for free download at

These guides were originally published as the proceedings of the 100th annual meeting of The Geological Society of America (GSA) was held in Phoenix, Arizona in October 1987. The newly available online guides are organized into separately downloadable sections.

One guide that may be of interest to laymen is “The Archaeological Geology of Paleo.-Indian Sites in Southeastern Arizona” which begins on page 212 of the Southern Arizona section. This paper discusses the late Quaternary geologic history preserved in the sediments in the San Pedro Valley and the Sulphur Springs Valley in southeastern Arizona . “These sediments are host to some of the oldest archaeological remains in North America.” Along the San Pedro River near Tombstone, “The Murray Springs Clovis site is unique in that it contains three distinct activity areas where a band of Clovis hunters killed a mammoth and several bison and occupied a small campsite during two or three brief visits 11,000 years ago. The buried occupation surface is clearly displayed in the arroyo walls as an erosional contact at the base of a distinctive black organic mat that preserved artifacts and extinct animal bones in their original position, and mammoth tracks, just as they were left 11,000 years ago.”

Here are the papers and guides:


Field-Trip Guide for Marble Canyon and Eastern Grand Canyon

Field Guide to the Lower Grand Canyon, from Peach Springs to Pierce Ferry

Geology of the Lower Grand Canyon and Upper Lake Mead by Boat–An Overview

Geology of the Grand Canyon – A Hike Through Time

Upper Holocene Alluvium of the Southern Colorado Plateau

Late Pleistocene Alluvium and Megafauna Dung Deposits of the Central Colorado Plateau

Late Cenozoic Volcanism in the San Francisco and Mormon Volcanic Fields

A Field Guide to the Jemez Mountains Volcanic Field, New Mexico

Stratigraphy, Correlation, and Tectonic Setting of Late Cretaceous Rocks in the Kaiparowits and Black Mesa Basins

Field Guide to Sedimentary Structures in the Navajo and Entrada Sandstones in Southern Utah and Northern Arizona


Late Paleozoic Depositional Systems, Sedona-Jerome Area, Central Arizona

Tectonic and Magmatic Contrasts Across a Two-Province Proterozoic Boundary in Central Arizona

Geomorphology and structure of the Colorado Plateau/Basin and Range Transition Zone


Land Subsidence and Earth-Fissure Formation in Eastern Phoenix Metropolitan Area, Arizona

Selected Hydrogeologic Problems in Central Arizona

The Archaeological Geology of Paleo-Indian Sites in Southeastern Arizona

Terraces of the Lower Salt River Valley in Relation to the Late Cenozoic History of the Phoenix Basin, Arizona

Late Cenozoic Deposits, Vertebrate Faunas, and Magnetostratigraphy of Southeastern Arizona

Caldera Structures Along the Apache Trail in the Superstition Mountains, Arizona

Field Guide to Lower- and Upper-Plate Rocks of the South Mountains Detachment Zone, Arizona

Structural Geology of the Rincon and Pinaleno Metamorphic Core Complexes, Southeast Arizona

Pinto Valley Copper Deposit

Tectonic Setting and Sedimentological Features of Upper Mesozoic Strata in Southeastern Arizona

Lower Cretaceous Coral-Algal-Rudist Patch Reefs in Southeastern Arizona


Paleoecology and Taphonomy of Recent to Pleistocene Intertidal Deposits, Gulf of California

Volcanic Structures and Alkaline Rocks in the Pinacate volcanic field of Sonora, Mexico

The Mesquite and Picacho Gold Mines: Epithermal Mineralization localized within Tertiary Extensional Deformation

Mesozoic Tectonics of Southeastern California

Field-Trip Guide to Parts of the Harquahala, Granite Wash, Whipple, and Buckskin Mountains,
West-Central Arizona and Southeastern California

Metamorphic Core Complexes, Mesozoic ductile Thrusts, and Cenozoic Detachments: Old Woman Mountains-Chemehuevi Mountains Transect, California and Arizona

Miocene Extension, Volcanism, and Sedimentation in the Eastern Basin and Range Province, Southern Nevada

Crustal Transect: Colorado Plateau-Detachment Terrane-Salton Trough

Field Guide – Oak Creek-Mormon Lake Graben Northern Arizona

The Oak Creek-Mormon Lake Graben lies between Flagstaff and Sedona, Arizona. The Arizona Geological Society and geologist Paul A. Lindberg have produced a 13-page field guide to the geology of the area (shown on the map below).

This geologic field trip guide circumnavigates a loop of ~120 miles from Flagstaff to Sedona along Highway 89A and returns to Flagstaff along the Lake Mary Road. The guide contains many illustrations and photographs and may be downloaded from:

Lindberg introduces us to the local geological setting:

“The Oak Creek-Mormon Lake graben (a rift valley formed by extension of the earth’s crust) has been faulted into the southwestern margin of the Colorado Plateau as basin and range crustal extension has migrated eastward across Western U.S. over time. The graben may be as young as 2-3 million years old, based upon the youthful appearance of numerous V-shaped canyons (Oak Creek, West Fork, Munds, Woods and Rattlesnake Canyons) that cut the minimally eroded original surface of the largely basalt covered core of the graben. That morphology is in sharp contrast to more maturely eroded landforms along the northeast margin of 10 Ma Verde graben near Sedona. Timing of the genesis of the Oak Creek-Mormon Lake graben may be contemporaneous with the main eruptive cycle of San Francisco Peaks north of Flagstaff, Arizona.”

The 12 geologic stops focus on recent faulting and the encroachment of Basin and Range extensional structures on the Colorado Plateau. Each stop is detailed in the text, which is amply illustrated with photographs and colored geologic sketches.

Oak Creek Graben map

Arizona Geological Survey adds Jim Sells data collection to database

Mining collectionsThe Arizona Geological Survey (AZGS) has a new website for mining data. This is a culmination of consolidation of the now defunct Arizona Department of Mines and Mineral Resources (ADMMR) with the AZGS.

Over the past several years, AZGS has performed a comprehensive inventory of the 30 archival collections, creating finding aids for the more than 10,000 folders, 6,000 maps, and 7,000 photographs.

Visit the new Mining Collections site here:         

On July 2, 2014, the James Doyle Sell collection, which include more than 800 Arizona mine file records, was added to the Arizona Geological Survey Mine Site. The Sell mining collection comprises over 1,800 folders containing geologic reports and mineral exploration data from around the world, but primarily from Arizona and other states in the Southwest.

James (Jim) Sell was a native Arizonan, born in Casa Grande in 1930; he passed away on 18 Feb. 2011. For 32 years, Jim worked for ASARCO, where he served for some years as Southwest Exploration Manager. During his long career, Jim engaged in 100s of exploration and mining projects. A meticulous fellow, Jim kept records of most of these endeavors and donated his entire collection to the Arizona Dept. of Mines and Minerals Resources (ADMMR). See an article in Arizona Geology Magazine here.

Go to to see an inventory of material in the collection.

An experimental virtual tour through the Grand Canyon

The Arizona Geological Survey is experimenting with new ways of communicating geology and geologic stories to Arizonans and K-12 educators.

AZGS has produced its first-ever map story which follows geologist Steve Rauzi and a team of geoscientists as they raft through Grand Canyon.

“In a sequence of 29 captioned images, you’ll see Grand Canyon and some of its tributary canyons as a geologist sees them. Rauzi fingers individual rock units and puts a face – of sorts – to the names of famous rock formations: Devil’s Ramp and Vulcan’s Forge – products of the Pleistocene Uinkaret volcanic field, Kiabab Limestone, Coconino, Tapeats and Muav Sandstone, Bright Angel and Hermit Shale, the Redwall, Temple Butte, and Bass Limestone, and the Vishnu Schist.

Steve and his companions ramble across ancient stromatolite beds – some of Earth’s earliest life forms, bushwhack across faults and massive rockfall deposits, and close in on the Vishnu Schist (river-mile 78), Arizona’s oldest rock formation, at the bottom of Grand Canyon’s inner gorge. At river mile 98, you’ll see a dory run Crystal Rapid, and at river mile 179 scout Lava Falls Rapids from a beach safely upstream.”

You can begin the journey here: A Geologist in Grand Canyon – Map Story. The graphic below shows the main page and the third image. Mousing over the inset on the right allows you to expand the image. Clicking the “x” on the bottom right of the expanded image returns you to the main page.


Here is the third image expanded. The caption reads “Peering upriver of Vasey’s Paradise. Springs flow from the Mississippian Redwall Limestone. The overlying cliffs are formed of Permian Supai Group, Hermit Shale, Coconino Sandstone, Toroweap Formation, and Kaibab Limestone.” The boats provide a sense of scale.


AZGS is soliciting comments from the public on improving the model. Comments may be sent to Mike Conway ( | 520.209.4146)

I learned something from this tour. I didn’t know that the Grand Canyon contains stromatolite beds (image 5) which are fossils of the earliest known life form on Earth.

Check it out. You may learn some geology and, if nothing else, there is some great scenery.

Arizona Geology e-magazine for summer 2013 now online

The Arizona Geology Survey has just released its summer, 2013, issue of Arizona Geology which features seven articles.  See the whole issue at

Most interesting to me is the article: Ground-Source Geothermal Heating and Cooling: Sustainable and Affordable Energy for Arizona and the U.S.  The article begins:

“This past August 12th was the first day of the new school year for ~ 1,000 students at Lookout Mountain Elementary School in Phoenix, Arizona. The high temperature that day was a torrid 109 degrees Fahrenheit while inside the newly constructed 50,000 square foot wing of the school, temperatures were a balmy 76 degrees Fahrenheit, thanks to a new ground-source geothermal system that exchanges heat with the cooler earth hundreds of feet below the ground surface.”

The other articles:

Arizona Seismic Update – January – July 2013

“The Arizona Broadband Seismic Network documented over 50 earthquakes in Arizona from January to July 2013. The quakes were mostly located in northern Arizona and were at depths ranging from 1.4 to 26 km (0.9 to 16.25 miles depth)”

Earthquake Shakes North Rim Area

“On July 7that 1:38 MST, a magnitude 3.5 earthquake shook the towns of Fredonia, Jacobs Lake, and Havasu . The earthquake was followed by a series of aftershocks, with two registering Md ~ 2.0 and several in the 1.0 range.”

Digitizing, Cataloging, and Publishing Arizona’s Mining Legacy Online: Mine Maps, Reports, and Photographs

“In 2011, the financially troubled Arizona Department of Mines and Mineral Resources (ADMMR) and the Arizona Mining and Minerals Museum shuttered their doors. The Arizona Geological Survey (AZGS) received the Department’s maps, photos and manuscript collections. That year, AZGS began a comprehensive inventory of the 30 archival collections, creating finding aids1 for the more than 10,000 folders, 6,000 maps, and 7,000 photographs.”

Update on the STATEMAP mapping program in Arizona

“The STATEMAP program is a component of the National Geologic Mapping Act of 1992. STATEMAP is a matching fund program whereby State general funds are matched one-to-one by federal funds to support geologic mapping by the states. The Arizona Geological Survey (AZGS) has participated in the STATEMAP program since its inception, and has produced 1:24,000-scale geologic maps of a large fraction of the State with funding from this program.”

Making Geologic Maps with GIS

“Geologic map production begins in the field. Geologists spend several months traversing pre-defined areas of Arizona’s landscape to collect geologic information about that area. Geologists collect qualitative and quantitative information in the form of observations in a field notebook or on a topographic map. Geologists use a GPS (global positioning system receiver) to identify observation locations.”

Summary of oil and gas activity in Arizona – January to June 2013

Besides oil & gas, this article provides brief information on drilling for carbon dioxide, CO2 sequestration, geothermal energy, and potash exploration.

Check it out.