Geology

Ice Age Mammals of the San Pedro River Valley, Southeastern Arizona

If you had been in Southeastern Arizona eleven or twelve thousand years ago, it would look much different from today. The climate was cooler and wetter, and the rivers actually flowed. Also, you would encounter a suite of large mammals which became extinct in North America. These animals included horses, camels, mastodons, mammoths, long-horned bison, tapirs, shrub oxen, and ground sloths, which were preyed upon by dire wolves, jaguars, cougars, bears, the American lion, and man. (Horses and camels were re-introduced from Europe and Asia.)

We know this because remains of all these animals were found in several sites along the San Pedro River between Tombstone and Bisbee and at other sites in southern Arizona.

At the end of the last glacial epoch, climate became very unstable with the result that many of these megafauna became extinct in North America and the human Clovis culture dispersed. I go into greater detail on extinction hypotheses in my article “Cold case: What Killed the Mammoths?” linked below.

The Arizona Geological Survey published a paper about these animals in 1998 which has recently become available for free download:

http://repository.azgs.az.gov/uri_gin/azgs/dlio/1682

Within this 32-page publication are drawings and brief descriptions of the animals and information about Clovis culture humans who hunted them. The paper describes how people hunted and speculates on causes of extinction.

According to AZGS:

Popular literature and illustrations often depict Clovis hunters using stone-tipped spears to attack full-grown mammoth. Archaeological evidence indicates, however, that they more often concentrated their efforts on calves and young adults, sometimes ambushing them near or at watering places. At the Lehner Mammoth Site bones of nine mammoths, all juveniles, were recovered. They were apparently trapped and killed in the stream bed where archaeologists uncovered their bones thousands of years later. The mammoth killed at the Naco Site was also a young adult.

Bison meat appears to have been popular among the Clovis people. At Murray Springs bones of eleven young bison were found along with bones of one mammoth. Both the mammoth and the bison were likely ambushed when they came to water.

Being so large and cumbersome to transport, a mammoth carcass was butchered where it fell. The presence of hearths at kill sites, such as Murray Springs and the Lehner Site, suggests that the hunters also ate some of the meat on the spot, perhaps roasting it as they proceeded with the butchering. Cut marks on bone surfaces, and broken cutting tools indicate that the meat was stripped from the carcass and transported to a nearby camp, where more of it could have been eaten or dried for future consumption.

See also:

Cold Case: What Killed the Mammoths?

A Very Brief History of Climate Change in the Sonoran Desert

Where the Glyptodonts roamed

 

 

 

 

 

 

 

 

 

 

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Rocks in the Chiricahua National Monument and Fort Bowie National Historic Site

The Arizona Geological Survey has made available for free download a 48-page booklet which explains geologic features of two areas of southeastern Arizona. This well-illustrated booklet is intended for the layman but is also interesting to experienced geologists.

The Chiricahua mountains are known for their thousands of rock pinnacles formed in volcanic rocks by weathering during the last glacial epoch. In a previous article, I explain “The Explosive Geology Of The Chiricahua Mountains.”

 

 

The new booklet provides photos and descriptions that allow you to find many volcanic features along major roads and trails in the monument. None of these features are designated by markers along the trail.

The geology of Fort Bowie is quite different and consists of sediments and granite intrusive rocks.

As described in the booklet:

“Fort Bowie was built to guard Apache Pass, a natural passage between the Dos Cabezas and Chiricahua Mountains that connects the San Simon and Sulphur Springs Valleys. The

dependable springs, including Apache Spring, that have attracted humans to this narrow passage for thousands of years are also the result of geology, specifically the Apache Pass fault.”

The booklet starts out by describing the past 30 million years of geologic history which includes plate tectonics and volcanism – the processes which gave rise to the features visible today.

The features of the Chiricahua Mountains are put in context as follows:

“The landscape of Chiricahua National Monument, like that of much of the Earth’s surface, is a complex mosaic of large and small geologic features. Some of these features were produced by processes that were more active in past geological time but have now slowed or ceased. Other features are the result of past and currently active processes; only a few owe their origin solely to recently active processes. Welded tuff, fiamme, surge beds, fossil fumaroles, and the dacite caprock, for example, were all produced during the eruption of the Turkey Creek caldera, about 27 million years ago. Some joints and spherulites formed as the ash sheet cooled. Other joints and the region’s mountain ranges and intervening basins are the result of Basin and Range faulting during the period 25 to 5 million years ago. Willcox Playa, talus cones, pinnacles, and slot canyons were produced by processes that were more active during the wetter, cooler climate of the glacial epochs from 1.6 million to 10,000 years ago. Tafoni, rock varnish, lichens, case-hardened surfaces, chicken heads, exfoliation shingles, horizontal ribs, solution ponds and the rounded form of the columns are all forming today. Unraveling the evolution of such complex landscapes makes geology a particularly challenging science.” If you are unfamiliar with some of the names of features, read the booklet.

URL to the booklet: http://repository.azgs.az.gov/sites/default/files/dlio/files/nid1731/dte-11chirichua_mtns.pdf

 

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

 

 

Houston’s long history of flooding

Houston, Texas, seat of Harris County, has a long history of flooding because the city was built on a flood plain. The deluge generated by hurricane Harvey in August, 2017, is only the latest episode.

Houston lies within a coastal plain about 50 miles northwest of Galveston. The area has very flat topography which is cut by four major bayous that pass through the city: Buffalo Bayou, which runs into downtown and the Houston Ship Channel; and three of its tributaries: Brays Bayou, which runs along the Texas Medical Center; White Oak Bayou, which runs through the Heights and near the northwest area; and Sims Bayou, which runs through the south of Houston and downtown Houston. The ship channel goes past Galveston and into the Gulf of Mexico.

The land around Houston consists of sand, silt, and clay deposited by local rivers.

The sedimentary layers underneath Houston ultimately extend down some 60,000 feet, with the oldest beds deposited during the Cretaceous. Between 30,000 feet and 40,000 feet below the surface is a layer of salt, the primary source of salt domes which dot the metropolitan area. Since salt is more buoyant than other sediments, it rises to the surface, creating domes and anticlines and causing subsidence due to its removal from its original strata. These structures manage to capture oil and gas as it percolates through the subsurface. [source]

Groundwater pumping also causes subsidence in parts of the city. (See: Geologists find parts of Northwest Houston, Texas sinking rapidly )

Hurricane damage in Houston:

As described by the Harris County Flood Control District (HCFCD) [link]:

When the Allen brothers founded Houston in 1836, they established the town at the confluence of Buffalo and White Oak Bayous. Shortly thereafter, every structure in the new settlement flooded. Early settlers documented that after heavy rains, their wagon trips west through the prairie involved days of walking through knee-deep water. Harris County suffered through 16 major floods from 1836 to 1936, some of which crested at more than 40 feet, turning downtown Houston streets into raging rivers.

Houston was flooded during the September, 1900, hurricane which wiped out Galveston.

In December of 1935 a massive flood occurred in the downtown Houston as the water level height measured at Buffalo Bayou in Houston topped out at 54.4 feet which was higher than Harvey. There have been 30 major floods in the Houston area since 1937 when the flood control district was established in spite of construction of flood control measures.

In June, 2001, Harris County suffered widespread flooding due to hurricane Allison. According to HCFCD, before leaving the area, Allison would dump as much as 80 percent of the area’s average annual rainfall over much of Harris County, simultaneously affecting more than 2 million people. When the rains finally eased, Allison had left Harris County, Texas, with 22 fatalities, 95,000 damaged automobiles and trucks, 73,000 damaged residences, 30,000 stranded residents in shelters, and over $5 billion in property damage in its wake.

Some climate alarmists are claiming that global warming has played a part in the flooding produced by hurricane Harvey. Dr. Roy Spencer debunks that notion here and here. Storms of or greater than Harvey’s magnitude have happened before. Storm damage is not due entirely to weather. Some is due to local infrastructure.

It all boils down to the luck of the draw: if you choose to inhabit a flood plain, you will get wet from time to time.

P.S. Prior to Harvey, which made landfall as a Category 4 storm, the U.S. had gone a remarkable 12 years without being hit by a hurricane of Category 3 strength or stronger. Since 1970 the U.S. has only seen four hurricanes of Category 4 or 5 strength. In the previous 47 years, the country was struck by 14 such storms.

Eldred Wilson’s Proterozoic Mazatzal Revolution Arizona

The Arizona Geological Survey has just made available for download papers by Eldred Wilson, a pioneer of Arizona geology.

Eldred Dewey Wilson & the Proterozoic ‘Mazatzal Revolution’

Study area map of Wilson (1937)

In 1937, geologist Eldred Dewey Wilson coined the phrase ‘Mazatzal Revolution’ to describe mountain building along the western edge of the North American craton. While the Mazatzal Revolution occurred in the Proterozoic – more than 1.6 billion years ago – it continues to influence Arizona geology and mineral exploration to this day. Wilson’s 1937 Ph.D. research is now available online for the first time.

In about 1920, twenty-two-year old Eldred Dewey Wilson joined a handful of geologists – N.H. Darton, Carl Lausen and Olaf P. Jenkins, among them – wrestling with the complex geology of the rugged mountains of southern and central Arizona. Wilson was an assistant geologist at the Arizona Bureau of Mines and working on his M.S. thesis, ‘The Mazatzal Quartzite, a new pre-Cambrian formation of central Arizona’ at the University of Arizona. In 1924 Wilson was promoted to geologist at the Bureau, where he remained, with a short leave of absence to begin his doctoral research in 1931-1932 at Harvard University, until his death in 1965.

Wilson set out in 1930 to address, ‘the chief features of pre-Cambrian regional structure within part of central Arizona’, for his Ph.D. dissertation – ‘‘The Pre-Cambrian Mazatzal Revolution in Central Arizona’. His field area included the Mazatzal Mountains, Pine Creek, eastern Tonto Basin or northern Sierra Ancha, Del Rio, and the southern Black Hills areas, all of which contained extensive outcrops of Proterozoic-age rocks. Wilson concluded from his observations of the field relationships of rocks and structures that the ‘principal features of regional structure originated from a great pre-Cambrian crustal disturbance’, which he called the ‘Mazatzal Revolution’.

Wilson’s ‘Mazatzal Revolution’ was an early contribution to deconstructing the processes responsible for the geology of central Arizona. He noted, ‘The subparallel folds, thrust faults, and imbricate, steeply dipping reverse faults clearly resulted from intense north­west-southeastward regional compression. The transverse faults are believed to have been formed, also during the compression, by shearing normal to the trend of the folds.’

Wilson hypothesized, too, that, ‘structural weaknesses inherited from the Mazatzal Revolution may have influenced the localization of many of Arizona’s prevailingly north­eastward-trending veins and the pattern of the Tertiary Basin and Range faulting.’ The orogenic Mazatzal Revolution continues to impact Arizona geology today.

E.D. Wilson ca. 1960s.

Reynolds & Others (2013) on Eldred Dewey Wilson’s contribution to Arizona geology. Wilson published a number of important papers on Arizona geology. According to Reynolds and others (2013), Eldred D. Wilson provided the first geologic map and cogent discussion of the geology and mineral resources of southern Yuma County: “Wilson mapped this hitherto unknown area of southwestern Arizona from 1929-1932. In the process, he discovered a new set of mountains that had been overlooked by previous geologists and explorers. He named this range the Butler Mountains after G. M. Butler, former Director of the Bureau and Dean of the College of Mining and Engineering (Wilson, 1931). Wilson was the first person to describe and map the geology of a large number of mountain ranges in southwestern Arizona. The data from Wilson’s 1933 geologic map were incorporated into the 1969 state geologic map.”

See James T. Forrester and Richard E. Moore’s ‘Memorial to Eldred Dewey Wilson 1898-1967’ for more about the life and times of Dr. Wilson.

Note: AZGS thanks an anonymous patron who arranged at his/her own expense with Harvard University to scan Wilson’s dissertation and secure copyright permission from Dewey Wilson to re-release Dr. Wilson’s work as CR-17-C.

References 
 
Forrester, J.T. and Moore, R.E., 1965 Memorial to Eldred Dewey Wilson 1898-1967. Geological Society of America Bulletin, V. 76, p. 187-191.

Reynolds, S., Spencer, J.E., Richard, S.M., Pearthree, P.A. 2013, The Geological Exploration of Arizona: The Role of State and Federal Surveys and the Geologic Map of Arizona, Arizona Geology Magazine, Winter 2013.

Wilson, E.D., 1922, The Mazatzal Quartzite, a new pre-Cambrian formation of central Arizona. Univ. of Arizona M.S. thesis, 40 p.

Wilson, E.D., 1937, The Pre-Cambrian Mazatzal Revolution in Central Arizona. Ph.D. Dissertation, Harvard University, Cambridge, MA, 335 p.

This post is reblogged from Arizona Geology

Site Investigation of Tributary Drainages to the San Pedro River, Arizona

The Arizona Geological Survey has just released a new paper: Site Investigation of Tributary Drainages to the San Pedro River, Arizona (Open-file Report OFR-15-02) which is available for free download at: http://repository.azgs.az.gov/uri_gin/azgs/dlio/1724

The paper begins:

In late 2013 the Arizona Geological Survey (AZGS) partnered with the Arizona Department of Water Resources (ADWR) to investigate sedimentary relationships at numerous sites along the San Pedro River in southeastern Arizona. This project supplemented previous work along the San Pedro River. In 2007, AZGS conducted surficial geologic mapping along the San Pedro River, Aravaipa Creek, and the Babocomari River. These maps and a report are available in AZGS DM-RM-1.2. The goal of the 2013 project was to conduct site investigations along the San Pedro River to determine whether sedimentary relationships between San Pedro River and tributary alluvium are accurately represented by their mapped location on the surface. This document includes a brief summary and description of sites along the San Pedro River visited by AZGS geologists in late 2013 and early 2014.

The report describes the geology of 39 sites with text, photos, and maps.

Related:

San Pedro River Geology – Implications for water law

West Antarctica ice-sheet calving due mainly to geology

Sometime between Monday 10th July and Wednesday 12th July, a 2,239 square mile section of Larsen C ice sheet finally broke away. As the media put it, that’s about the size of the State of Delaware. The Larsen C ice sheet is located in the Weddell Sea near the tip of the West Antarctica peninsula. The resulting iceberg has been designated Larson A68. Some of the media claimed this calving was due to human-induced global warming and portends a scary future. (See LA TimesNew York Times , and CNN stories. CNN headline: “That huge iceberg should freak you out” )

The LA Times story does note that in the year 2000, a 4,200 square mile chuck of ice calved from the Ross Sea ice shelf.

A scientist from Project MIDAS, a UK-based Antarctic research project investigating the effects of a warming climate on the Larsen C ice shelf in West Antarctica, said that they were “not aware of any link to human-induced climate change…” (Source)

The geology of West Antarctica is discussed in a long post by geologist James Kamis (read full post).

As shown on Kamis’ figure 2 above, West Antarctica is within a major rift zone which is pulling the continent apart. There are also 61 recognized volcanos on the surface, on the sea bed, and under the ice, all of which provide heat and tectonic instability. Kamis contends that the geology is driving ice shelf calving.

Calving of giant ice bergs is not a new phenomenon. A 1956 newspaper story found by Tony Heller of RealScience.com documents two large icebergs. One, spotted by a Navy icebreaker was 208 miles long and 60 miles wide (12,480 square miles, about the size of Massachusetts and Connecticut combined). During the same year another iceberg measuring 200 miles long and 10 miles wide calved from the Ross Ice Shelf. The same story notes that the Navy Hydrographic Office reports a 100 mile by 100 mile iceberg (10,000 square miles) spotted by a whaling ship in 1927. (Source) Remember that good coverage of ice shelf calving is made possible by satellite observation which began in 1979. Before that, it was by chance observation from ships.

See also:

The “Unstoppable Collapse” of the West Antarctic ice sheet

Geology is responsible for some phenomena blamed on global warming

A Simple Question for Climate Alarmists

Out of the wildfire and into the flood – Arizona Summer 2017

After several quiet years, Arizona has had a very active wildfire season. Halfway through 2017, just over 352,000 acres have been burned in Arizona by wildfires of >100 acres in size (Inciweb for Arizona: https://inciweb.nwcg.gov/state/3/). This was the worst fire season since the record burns of 2011, and is almost 4 times as many acres burned than in 2013 (Table 1; Southwest Coordination Center: https://gacc.nifc.gov/swcc, accessed July 12, 2017). While the worst part of the fire season is likely behind us, based on recent years we can expect to see more wildfires in the fall. Most of the 2017 burned acreage has been on land managed by the U.S. Forest Service (USFS), followed by Arizona State lands (AZFD), Bureau of Indian Affairs (BIA), and Bureau of Land Management (BLM).

As the monsoon season ramps up, it is time to be cognizant of potential post-fire flooding and debris flows. Both floods and debris flows pose significant hazards to human health, property and infrastructure, and both carry a significant amount of sediment, woody material and rocks. Debris flows can be more dangerous, however, as they resemble slurries of dense, fast-moving concrete that carry more sediment and woody debris and larger caliber rocks (maybe up to basketball sized rocks in floods and car or truck sized boulders in debris flows).

Wildfires significantly impact watershed hydrology, causing much more runoff to occur and frequently triggering post-fire floods and debris flows. In the absence of wildfire, unburned vegetation intercepts raindrops, mitigating the impacts of high-velocity drops on soils. Depending on the burn severity of the wildfire, interception of rainfall by plants can be severely reduced or completely eliminated. At the same time, infiltration of water into the soil is impeded by the presence of ash and fire-related changes to soils (e.g. hyper-dry soils, hydrophobicity, and the destruction of organic matter). These changes result in increased runoff volumes and velocities such that smaller, short-lived monsoon storms can generate tremendous runoff, flooding, and debris flows, and do a huge amount of geomorphic work (i.e. erosion and transportation of sediment) in a very short period of time.

Post by Ann Youberg

Read more at: http://arizonageology.blogspot.com/2017/07/out-of-wildfire-and-into-flood-arizona.html

Mineral Resources of some Arizona National Monuments

In view of President Trump’s program to reassess some National Monuments, the Arizona Geological Survey has released flyers regarding the mineral potential of four Arizona monuments: Ironwood Forest, Grand Canyon-Parashant, Sonoran Desert, and Vermilion Cliffs. You may read these short flyers here: http://repository.azgs.az.gov/uri_gin/azgs/dlio/1715

Ironwood Forest, about 35 miles northwest of Tucson, has an active copper mine and, according to local geologists, much more potential resources both east and west of the active mine. You can read about the history of the Silver Bell mine in a new paper by geologist David Briggs here: http://repository.azgs.az.gov/uri_gin/azgs/dlio/1714 Briggs notes: “Over the past 130 years, the Silver Bell mining district yielded approximately 2.27 billion pounds of copper, 6.6 million pounds of molybdenum, 3.7 million pounds of lead, 40.8 million pounds of zinc, 2,100 ounces of gold and 5.95 million ounces of silver.”

The Grand Canyon-Parashant area has produced copper, uranium, lead, zinc, gold, and Silver from breccia pipe deposits within what is now the monument. Breccia pipes are vertical pipe-like structures comprising broken rock (breccia). They are collapse features that originate in the cavernous Redwall Limestone and subsequently propagate upward through upper Paleozoic and lower Mesozoic rock formation. A recent review by the Arizona Geological Survey indicates that there could be thousands of yet unexplored breccia pipes within the monument. (See my article: Breccia pipes of northwestern Arizona and their economic significance)

The Sonoran Desert monument west of Phoenix has historically produced , gold, silver, copper, and manganese from small mines. The Aguila manganese mineral district in the Big Horn Mountains produced 42 million pounds of manganese.

The Vermilion Cliffs area in northwestern Arizona has had some small production of uranium, but the AZGS concludes “ there is little geologic evidence for economic minerals deposits in the monument.”

Two of the monuments, Ironwood Forest and Grand Canyon-Parashant, have had significant mineral production and more inferred resources. Local geologists suspect there are more copper resources east and west of the active mining area of the Silver Bell mine, but that ground is effectively off-limits because it lies within Ironwood Forest National Monument. The monument was imposed over valid pre-existing mining claims. This should be taken into account in assessing their status. The imposition of National Monument designation greatly inhibits or even prevents development of valuable mineral resources.