Geological environment and engineering properties of caliche in the Tucson area, Tucson, Arizona

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Authors Cooley, Donald B., 1937-

Publisher The University of Arizona.

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Link to Item http://hdl.handle.net/10150/551826 GEOLOGICAL ENVIRONMENT AND ENGINEERING PROPERTIES

OF CALICHE IN THE TUCSON AREA, TUCSON, ARIZONA

by Donald B. Cooley

A Thesis Submitted to the Faculty of the

DEPARTMENT OF GEOLOGY

In Partial Fulfillment of the Requirements For the Degree of

MASTER OF SCIENCE

In the Graduate College

THE UNIVERSITY OF ARIZONA

19 6 6 STATEMENT BY AUTHOR

This thesis has been submitted in partial fulfillment of requirements for an advanced degree at The University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library.

Brief quotations from this thesis are allowable without special permission, provided that accurate acknowledgment of source is made. Requests for per­ mission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in his Judgment the proposed use of the material is in the interests of scholarship. In all other instances, however, permission must be obtained from the author.

SIGNED! 'f

APPROVAL BY THESIS DIRECTOR

This thesis has been approved on the date shown below;

Date Professor of Mining and Engineering Geology AKNOWLEDGMENTS

I should like to thank the many people who have given so freely of their time in my behalf. I should like to thank especially Dr. W. C. Lacy, Dr.

J. s. Sumner, and Dr. L. K. Lustig for their guidance and helpful criticisms in the form and content of this thesis. The base map was supplied by the University of

Arizona Agricultural Engineering Department. In particular I would like to thank Mr. James Post for his help in the laboratory portion of this study. I also thank my brother Steven for swinging a 12 pound hammer in the hot sun, and my wife for all her invaluable aid in this project.

ill TABLE OF CONTENTS

Page

ABSTRACT vili

INTRODUCTION 1

Location Environment

Methods of study -prtvro

PREVIOUS WORK 7

Mode of Deposition 7 Physical Characteristics 10 Physiographies Relations 13 Cementation 16 Relation to Rainfall 18 Age Determinations 19

TERMINOLOGY 20

DESCRIPTION AND DISTRIBUTION 26

Alluvial Fans 26 Caliche on Sentinel Peak 32

SAMPLE TESTING PROCEDURES 35

GEOPHYSICAL INVESTIGATIONS 40

THE CALICHE PROFILE 48

Growth of the Caliche Profile 50 Source of Cementing Agents 54

CALICHE AND ENGINEERING 57

CONCLUSIONS AND RECOMMENDATIONS 61

Conclusions 61 Recommendations 64

USES OF CALICHE 66

iv V

Page

REFERENCES CITED 68

APPENDIX

Typical Caliche Profile-Pinal Soil Series 74 Selected Seismic Velocities in the Caliche 75 Seismic Velocities and Rippability of Materials 77 Selected Bibliography 80 LIST OF ILLUSTRATIONS

Figure Page

I PHYSIOGRAPHIC UNITS OF THE TUCSON AREA 14

II CALICHE-GROUND SURFACE RELATIONSHIPS 25

III ISOPACHOUS MAP OF THE SUBSURFACE CALICHE IN THE TUCSON AREA 31

IV SEISMIC VELOCITY CURVE; 14TH STREET AT TULLER SCHOOL 45

V SEISMIC VELOCITY CURVE; CORNER OF SPEEDWAY AND CAMPBELL AVENUE 46

VI SEISMIC VELOCITY CURVE; SOUTHWEST CORNER OF SPEEDWAY AND QUEEN AVENUE 4?

VII GENERALIZED CALICHE PROFILE 49

VIII ILLUSTRATION OF TYPICAL CALICHE PROFILE- FINAL SOIL SERIES 74

IX RELATION BETWEEN CARBONATE CONTENT AND UNCONFINED COMPRESSIVE STRENGTHS OF CALICHE 78

X RELATION BETWEEN CARBONATE CONTENT AND INFILTRATION RATE 79

XI MAP OF SURFACE AND NEAR SURFACE CALICHE DISTRIBUTION IN THE TUCSON AREA (in pocket)

vi LIST OF TABLES

Table

I UNCONFINED COMPRESSIVE STRENGTHS OF SOME CALICHE SAMPLES IN THE TUCSON AREA

II RIPPING, COST, PRODUCTION BY SHOCK WAVE VELOCITIES

III RIPPABILITY VELOCITY CHART

IV SELECTED SEISMIC VELOCITIES AND LOCATIONS

V SEISMIC VELOCITIES AS RELATED TO RIPPABILITY OF MATERIALS ABSTRACT

The caliche in the Tucson area is present at or near the surface in much of the area, and is more indurated at the toe of the fans than near the apex or in the

interior. The caliche caps most of the ridges and is probably responsible for their preservation as ridges as

the fans are dissected. Seismic velocities range from

1000 fps to 4500 fps for the caliche and unconfined com­ pressive strengths range from 200 to 300 psl to 2500 to

3000 psl depending on the orientation of the sample

during testing and the type of caliche present. The

seismic velocities are related to the thickness of the cap

and to the continuity of the cap.

The caliche profile is one of increasing carbonate

cementation from the bottom to the top of the profile.

Caliche development on the fans is due to the weathering

of limestones in the drainage area and limestone fragments

carried onto the fan. The carbonate material may be trans­

ported many times before it becomes fixed into the caliche profile. The significance of the caliche to engineering

projects is primarily the increased cost of excavation.

viii INTRODUCTION

In the Tucson area, caliche is present in many places at or near the surface of the ground. The presence of caliche at a construction site usually in­ creases the cost of excavation. A knowledge of where caliche might be encountered and how difficult it may be to excavate would be of value to a contractor in estimating costs and assigning equipment.

This report is a preliminary study of some engineering properties of the caliche and methods used to predict the excavation properties of the caliche.

Some seismic velocities have been determined for the caliche, and an attempt to correlate them with equipment requirements for excavation of the caliche has been made.

In addition, some unconflned compressive strengths have been determined for a few caliche samples. The map in the pocket shows distribution of the caliche at or near the surface. The degree of induration seems to be related to the physiography of the area. At least two environments of deposition are present in this area; one is on the alluvial fans in the basin, and the other is in the basic volcanic rocks to the west of Tucson.

1 2

Location

The area under study is essentially within the

Tucson Quadrangle (32° 001 to 32° 15* North latitude;

110° 45* to 111° 00* West longitude), in and around the city of Tucson, Pima County, Arizona.

The area is bounded by the Santa Cruz River on the west, Rillito Creek on the north, Pantano Wash on the east, and the southern limit of the fan on which

Tucson is located, on the south. Small areas just east of Pantano Wash and on Sentinel Peak were examined.

The caliche distribution map is prepared for the entire area but the analysis of engineering properties pertains to the northern half of the area. This is primarily because most of the active and projected con­ struction is taking place in the northern part of the area.

Environment

The Tucson area is typical of most of the country in the desert portion of the southern part of the Basin and Range province. The central portion of

the area is a structural and sedimentary basin with gentle slopes rising to the mountains that surround the area. Caliche is present at or very near the surface of

these slopes. 3 The climate is semi-arid with an average of about ten inches of precipitation per year. Most of this

occurs as thunder showers, and a great amount of sediment

is carried in the washes after major rains. In this

climate, the storm runoff is more devastating than would

be the case if more vegetative cover was present and

storm erosion is more pronounced. The vegetation of the

area, which is adapted to a dry climate and has a minimum

of leaves, offers little protection to the soil from the

rains. Within the area, creosote bush, cacti, and

rabbitbrush are dominant (Shreve and Mallory, 1933)•

Because of the warm climate and the tendency for

the water which is not carried away in the washes to be

spread out over the surface in thin layers, much of the

water is evaporated and recharge takes place primarily

along the bottoms of the washes following the rains.

The major drainage of the area is the Santa Cruz

River which flows northward along the west side of the

basin. Rillito Creek and its tributary, Pantano Wash,

drain into the Santa Cruz River in the northwest comer

of the area.

The streams now run along the edges of the basin at approximately the contact between the alluvial fill

and the rocks of the surrounding mountains. 4

The area has been one of aggradation Interspersed with short periods of erosion. Bryan (1925) has dated

the present period of channel entrenchment in this area as beginning in the 1880's or about the time man intro­ duced large herds of grazing animals into the area. When

the Army moved into Fort Lowell (1872), the area along

Rillito Creek supported a heavy stand of willow and

cottonwood, and grass hay was very abundant. At that

time, the water table was within twenty feet of the sur­

face. The water table is now being depressed by withdrawal

of groundwater for use in Tucson and surrounding areas.

Methods of Study

The field work for this study was undertaken

during the summer of 1965 and a total of 73 days was

spent in the field observing exposures and collecting

samples.

Areal photographs and a semi-controlled mosaic

of these same photographs were used to prepare the

(figure XI) map. The photo interpretations were cross

checked against known exposures of caliche in the field.

The photographs selected were taken in 1936 and were

used because a minimum area was covered by the city at

that time. The exposures, once verified, were transferred to the base map enlarged to the same scale. The base map 5 was supplied through the courtesy of the Agricultural

Engineering Department of the University of Arizona.

In the northern half of the area, the map could

"be checked readily by walking along the streets at the edges of the exposure. Where construction since the photographs were taken obscured the exposure, a check with many homeowners gave information about the presence or lack of caliche. Many conversations with engineers, equipment operators and contracting firms, gave valuable information about the location, characteristics, and excavation properties of caliche in many areas.

In the southern part of the area, access is more difficult and observations were made along the few roads and by walking along ridges and washes of the area.

Reliability is somewhat less than in the northern half of

the area, but is sufficient for the purpose of this report.

The areas occupied by Davis-Monthan Air Base and the Air Force Bombing Range to the south were not

investigated because of the access problem.

A total of 32 samples was examined to determine

the percentage of carbonate present and the insoluble

residues were examined to determine rock type and mineral

content. Those samples of the indurated cap examined

were also sieved to determine the size distribution of

the residue 6

Seismic velocities were determined at a number of locations. Most of these sites were chosen for their position in the caliche profile because it was thought that the physical condition of the cap was the most sig­ nificant factor in excavation of the caliche.

A number of samples were trimmed and broken and the unconfined compressive strength of the caliche was calculated. As much of the profile as possible was sampled and tested in each instance. The results of these studies are general and a great many more questions arose than were answered. PREVIOUS WORK

Within the United States, caliche occurs in the

Ogallala Formation in the High Plains Province from

Nebraska to Texas, through New Mexico, Arizona, Utah and Nevada and as far north as eastern Washington. Much of this distribution is recorded in the Soil Survey Series published by the Department of Agriculture, but some geologists have worked specifically on this subject.

Frye and Elias in Kansas, Lonsdale in Oklahoma, Price and Brown in Texas, Bretz and Horberg in New Mexico, and Breazeale and Smith in Arizona are the main contri­ butors to the knowledge on caliche. The geology of

caliche deposits elsewhere is not much different from

that in Arizona, and only a few of the more important

contributions will be discussed here to show the similarity and serve as a background for the following discussion.

Mode of Deposition

The reasons for Investigating caliche are quite varied but nearly all Investigators have given an opinion

on the origin of caliche. Bretz and Horberg (1949) com­ piled a general list of the theories of caliche formation

under consideration at that time. Following is an updated

7 8 modification of that list (In the appendix is a selected bibliography that shows the world wide distribution of

this material throughout the arid and semi-arid regions

of the earth):

1. Deposition in extensive shallow lakes by

algae and inorganic processes as proposed for the Ogallala

caprock by Ellas (1931, 1948).

2. Deposition in small disconnected lakes and

ponds by physical and/or organic processes. (Theis, 1936;

Frye, 1945; Vinson, 1916; Griffin, 1920)

3» Deposition along streams, especially inter­

mittent streams by physical and/or organic processes.

(Trowbridge, 1926; Miller, 1937; Price, Ellas and Frye,

1946)

4. Deposition by rising artesian waters, either

at the water table or at the surface. (Blake, 1901;

Smith, 1938)

5« Deposition by capillary rise of water from

the watertable, especially under conditions of high water

table (Lee, 1905), or a rising water table brought about

by aggradation (Theis, 1945).

6. Deposition in the B zone of the soil by

descending surface waters of the capillary rise of surface

waters following saturation of the soil zone. (R. H.

Forbes in Lee 1905; Glinka, 1914; Marbut, 1923; Udden, 9 1923; Gould and Lonsdale, 1926; Hawker, 1927; Price, 1933;

1940; Sayer, 1937; Sidwell, 1943; Bretz and Horberg, 1949;

Brown, 1956 (Cca horizon); Swinford, Leonard and Frye,

1958; Gile, 1961; Stuart, Forsberg and Lewis, 1962).

7 . Various combinations of the above. (Lee,

1905; Trowbridge, 1926, Breazeale and Smith, 1930; Price,

Ellas and Frye, 1946)

Breazeale and Smith (1930) drew the following conclusions about caliche formation in Arizona and have been widely quoted:

1. Caliche, wherever found in Arizona, was formed by solution, transportation and precipitation of calcium carbonate.

2. Water when charged with carbon dioxide dissolves calcium carbonate and forms calcium bicarbonate.

The calcium bicarbonate is carried in solution and is precipitated as calcium carbonate, or caliche, when the water is evaporated or when there is a decrease in pressure which drives off COg.

3. Caliche strata may be formed beneath the sur­

face of a soil either by the evaporation of descending

surface water, or by the evaporation of ascending ground- water.

4. Caliche may be formed in a soil by means of plant roots. Plants growing upon the surface absorb 10 soil water for transpiration purposes, and the calcium carbonate that is dissolved in the soil solution is pre­ cipitated as caliche.

5. As long as they are permeable to water, caliche strata will move downward in a soil as fast as erosion removes the upper soil surface.

6. Caliche is probably formed upon the surface of a soil by the evaporation of surface or flood water.

The formation under such conditions is hastened by the presence of algae and other water plants.

Blank and Tynes, (1965) cite instances of "in place" transformation of carbonates into a soft or spongy caliche. This transformation apparently results in an increase in volume and is often associate with local, small, often very tight folds near the surface of the type described by Price (1925)• Jennings and

Sweeting (1961) discuss similar occurrences of caliche in

Western Australia.

Physical Characteristics

Other investigators have classified caliche on the basis of physical characteristics, primarily the hardness of the dense indurated cap or the caliche profile.

Price (1933) has related this to maturity of the caliche profile in his classification: 11

Young Caliche: Incipient and young accumulations of soil lime in the form of grains, flakes, nodules, irregular aggregates, and unconsolidated beds of soil

carbonates. (Modem writers usually refer to this as a limey subsoil horizon.)

Mature Caliche: Consolidated beds of calcium

carbonate•

Old Caliche: Tough soil minerals of arid (desert) regions including dense hard caliche limestone, desert

glazes, vitreous varieties of siliceous caliche and

similar surface and soil deposits of deserts. Price used

caliche as a generic term for all types of soil-mineral accumulations including ferriginous, siliceous, and aluminous varieties, glazes of manganese, and vitreous

or opaline silica.

Gile (1961) also classified caliche according to

its physical characteristics. He classified the Ca-

bearing soil horizons as indurated and unindurated on the

basis of slaking or not slaking when placed into water,

and then further subdivided them as follows:

1. Very strongly indurated; material extremely

hard, has unconfined strength range from 3000-8000 psi, difficult to remove from the horizon, difficult to break

with a hammer and difficult to score with a knife. 12

2. Strongly Indurated; material is very hard, has unconfined compressive strength range from 750-3000 psi, breaks readily with a hammer, but is difficult to remove from the horizon, and can be scored with a knife.

3. Moderately indurated; Hard, compressive strength from 150-750 psi, readily removed from the horizon, breaks easily with a hammer, and scores easily with a knife.

4. Slightly Indurated; not very hard, compressive strength less than 150 psi, easily removed from the horizon, easily broken with a hammer.

Non-indurated horizons slake in water, have soft to hard consistency, compressive strength (air dry) ranges from 0 to 800 psi, but most are less than 25 psi; may be hard to remove from the horizon or may be loose; are readily broken with a hammer and are easily scored with a knife.

The carbonate content is reported by Gile to be

from less than one percent to more than ninety-three percent. The unconflned compressive strengths increased with a corresponding increase in carbonate content. On

the basis of the above characteristics, Gile classified

the Ca horizons as weak, moderate, strong and very strong. 13 Physiographic Relations

A number of authors have discussed caliche in relation to physiography.

G. E. P. Smith (1938) noticed that all caliche in the Tucson area was not the same and described a

characteristic type of caliche for each of the terraces.

The University Terrace, which is the highest,

has the hardest caliche. This caliche also contains the

coarsest material, except locally. The Cemetery Terrace

is the next highest and is represented by level surfaces

between University ridges. This terrace has a caliche

zone that is much softer than the University type. The

Jaynes Terrace, below the Cemetery Terrace, is repre­

sented by surfaces below and between the Cemetery remnants,

and has a limey subsoil. The fourth bench is the Bottom­

lands which is the present day floodplain of the Santa

Cruz River and Rillito Creek; it is characterized by

having no carbonate accumulation in the subsurface.

Other writers, Babcock and Cushing (1952), Cooley

(1961), Streitz (1962), and Lacy (1964), have all observed

that there is no caliche formation below stream beds and

their floodplains. Cooley believed this to be the result

of the rapid rate of deposition there and Lacy attributed

the absence of caliche to down flushing. 14

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Canyon area was most indurated on the higher terraces and stated:

The more favorable places for caliche development are in areas where little erosion or sedimentation occurs and where residual deposits can accumulate. These areas are mostly along gentle bed­ rock and alluvial slopes which bordered the floodplains of old through flowing streams and on the top of terraces com­ posed principally of sand and gravel.

He also states that in each locality the local physiography and hydrologic conditions control the mode of formation of the caliche. Vfoolnough (192?) made a similar statement about the duricrust in Australia.

Stuart, Fosberg, and Lewis (1962) also found that

the caliche is most indurated on the higher terraces in

southern Idaho, which are dated as Early and Late

Pleistocene. They also found that caliche does not

form on slopes steeper than 12 to 15 percent.

Price (1933) stated that caliche is a protective

agent against weathering and erosion, that preserves

plateaus and prevents the erosion of outcrops.

Bretz and Horberg (1949a) described the caprock

of the caliche as a dense limestone a few feet thick,

but one that is topographically prominent because it has

great resistance to erosion. 16

Brown (1956) stated that the upper caliche sur­ face forms the backbone of the landscape even though it is only a few feet thick.

Judson (1950) discussed the relation between caliche and depressions in the southern High Plains. He argued that the depressions are not collapse features, due to the solution of the caliche, but are the result of leaching and deflation. A very interesting question that arises is whether the depressions represent the trace of a buried pre-Pleistocene drainage pattern or some other condition. The depressions are developed along lines that parallel the inferred strike of under­ lying folded and eroded Mesozoic rocks.

Cementation

One of the characteristics of caliche is the predominant cementation by calcium carbonate. Some of the cementing material is magnesium carbonate but the percentage is so low, that it is customarily reported to consist entirely of calcium carbonate. Several re­ searchers (Sidwell, 1943; Brown, 1956; Stuart, Forsberg and Lewis, 1962; and Reeves and Suggs, 1964) have all found small percentages of silica within the cementing agents. Reeves and Suggs found mappable trends in the carbonate percentages. 17 Brown (1956), Van Siclen (1957)* Bretz and Horberg

(19^9) have all stated that the caliche on the high plains

seems to represent a surface of equilibrium between

erosion and depostion and that the source of the caliche

is the limestone gravels in the Ogallala Formation. At a single horizon the "algal limestone" has been formed.

This "algal limestone" was first named by Elias (1931) and the term was further applied by Price, Elias, and

Frye (1946). However since then many authors (Brown, 1956;

Bretz and Horberg, 1949; Swineford, Leonard and Frye, 1958;

and Price, 1965 and others) have debated this and all

descriptions of the "algal limestone" zone seem to be of

a massive, recemented, brecciated caliche layer. Swineford,

Leonard and Frye (1958) have stated that this deposit was

not formed by algae and the following conditions are

necessary for formation of the "algal" horizon: 1) presences

of soluble materials rich in Ca*H ions, 2) permeable

materials, 3) deficient rainfall and long dry periods,

4) low topographic relief and 5) time.

W. Armstrong Price (1965) stated that he no longer

retains his original opinion on the "algal" caliche, as

stated in Price, Ellas and Frye (1946); however, he offers

no other solution to the problem. 18

Relation to Rainfall

Many authors have stated that rainfall must be considerably less than evaporation to form caliche. This is true at all places where caliche is now found, but carbonate nodules are known to be forming in the sub­ surface of glacial materials in the northeastern part of the United States where the tills contain limestone fragments. (Flint, 1957. Bryan and Albritton, 19^3)

Weeks (1933) stated that caliche formation generally occurs west of the 32 inch rainfall line.

Motts (1958) has made some interesting correlations concerning caliche genesis and rainfall. A curve showing the relation of rainfall and caliche thickness should show an increase in thickness of caliche corresponding to an increase in rainfall, to a critical point; however this curve has not been published. Below this critical precipitation value, successively greater amounts of carbonates are deposited in the subsoil. Above this value, more carbonates are carried down to the water table. "Relatively thick caliche profiles formed by weathering in sediments of similar texture, composition, and sedimentation rate may indicate either areas of greater water inundation or the former existence of pluvial cycles." 19 ' Age Determinations

Many writers; Price, 1933; Antevs, 1955; Bretz and Horberg, 1949; Smith, 1938, and others have ascribed

the deposition of caliche to the climatic conditions of

the interglacial or glacial stages. Van Siclen (1957) believes most of the caliche is Late Pleistocene,

Sangamon, age.

Damon, Long and Sigalove, (1963) on the basis of 14 C dating state that caliche formation at Brown Mountain

occurred during the last pluvial period. They state that,

in general, caliche is more radioactive near the top of

the profile. Caliche collected from lava flows in the

San Francisco Volcanic Field was thicker on the older

flows than on the younger flows. Damon, Haynes and Long,

(1964) give an average date of about 9800 years B.P. for

caliche dated in Avra Valley and an approximate rate of

formation of one inch per thousand years.

Buol (1964) and Buol and Yeslloy (1964) give

dates of caliche formation, based on methods ranging

from 32,000 to less than 2,300 years B.P., with age

decreasing upward in the caliche profile. TERMINOLOGY

Caliche, as a scientific term is in danger of becoming useless. The term, has been used to describe

too many different materials and should be carefully

described each time it is used.

In the southwest, caliche is used to refer to

a hard, more or less massive carbonate layer, on or near the surface of the ground with a laminar, dense,

indurated cap at the top of the caliche profile. The

caliche profile must consist of a zone of carbonate

accumulation, and subsequent cementation of the material

involved must produce a relatively coherent mass. The

term caliche as used in this report shall include both

the indurated cap and the underlying cemented material.

In other parts of the world, caliche is applied

to other substances. The term is derived from the Latin

Calx, and was first used by the Spaniards to describe

the flakes of whitewash that weathered from the mud

houses of southern Spain.

Pay (1910) lists the following meanings for the

term caliche:

Caliche: 1. (Chile and Peru) impure native nitrate of soda. 2. (Uco, Peru) A thin layer of clayey soil capping auriferrous

20 21

veins. 3* (Chile) Whitish clay in the selvage of veins. 4. (Mexico) Feldspar: a white clay. 5» (Mexico) a compact transition limestone. 6. (Colombia) A mineral vein recently discovered. 7. (Colombia) In placer mining, a bank composed of clay, sand, and gravel (Halse). 8. (Mexico and the Southwest United States) Gravel, sand or desert debris cemented by porous calcium carbonate, also the calcium carbonate itself.

The American Geological Institute Glossary (i960) merely repeats the list given by Fay. A valid scientific term should not imply so many divergent meanings.

The Soil Survey Manual (1962) offers croute calcalre as an alternate term for caliche with the state­ ment that it must be hardened and not simply a lime- accumulation horizon.

The Seventh Approximation (Soil Survey Staff,

I960) uses duripan to classify horizons in the soil that are cemented, usually by silica, aluminum silicate and/or carbonates. In a memorandum, dated June, 1964, on changes in nomenclature for the Seventh Approximation, the terms "petrocalcic** and ’’durlnodes" were proposed.

Their meaning is as follows:

Petrocalcic horizon: A massive calcic horizon cemented with carbonates and at times with accessory silica, and having a laminar surface layer in at least part of the pedon. The laminar layer has a hard­ ness of 3 or more (Mohs scale) when dry. More than half of the layer breaks down under treatment with acid but not with water. It has an abrupt, smooth or wavy upper boundary and has included gravel, sand or silt grains that are separated by 22

the carbonates. The horizons may be a meter or more thick, but if the laminar layer has a lithic contact at its lower boundary, the horizon may be as thin as 2.5 cm. Durlnodes: (L. durus hard; nodus knot) Durinodes are weakly cemented to indurated nodules that break down in concentrated KOH after treatment with HCl to remove carbonates, but that do not break down on treatment with HCl alone. The cement is SiOg, presumably opal. Dry durinodes do not^slake in water. They are firm to extremely firm, and brittle when wet, be­ fore and after acid treatment; they are discontinuous and range upward in size from about one centimeter.

Woolnough in Australia (192?) defined the term

"duricrust" as a remnant of a peneplaned surface which has been cemented. The cement can be silica, carbonates, aluminous or ferriginous, largely depending upon the parent material. He ascribes the formation of durlcrust to topographic relief and seasonal rainfall, all other factors being subordinate. According to Woolnough, some of the calcium carbonate duricrust has been called travertine in the past, and this may or may not be caliche as we know it.

Lamplugh (1907) in the Zambesi Basin of Africa described a material like caliche and duricrust. Those materials cemented by calcium carbonate he termed calcrete, and those materials cemented by silica and iron, he termed silicrete and perricrete, respectively.

In Australia and Africa, the term duricrust is

commonly used to include all cemented soil materials; 23 duricrust is subdivided into calcrete, silcrete, and ferrlcrete. Ruhe (I962) used the term calcrete when referring to caliche in southern New Mexico. In Egypt, caliche is known as Sabath, and in India as Reh. (Twenhofel,

1950, p. 376.)

The term caliche is interpreted as a hard calcareous zone at or near the surface of the ground by people in the southwestern United States, but other possibilities exist elsewhere. Many terms now in use describe the material very well and are more explicit.

The term duricrust, and its subdivision calcrete, or even croute calcaire is probably of greater validity.

A distinction must be made here between caliche and a limey subsoil horizon. Caliche is hard and well cemented, digging is difficult, and sometimes the in­ cluded particles will break rather than the surrounding cement. Soil horizons in which lime accumulates are usually dissagregated by Immersion in water and certainly by treatment with HC1. Breazeale and Smith (1930) dis­

cuss a "soft caliche" and remark about its permeability and the remarkable characteristic of remaining at about

the same depth below the surface (2-3 feet) ♦ Most caliche

is found at or near the surface, but the depth is not as

constant as is normally reported, although there are places where the uniformity of depth is quite constant. 24

In certain portions of the great plains, degradation has been on the order of a hundred feet, but the caliche zone always remains at the same approximate depth below this surface. Stuart, Fosberg and Lewis (I96I) found this relation to hold in parts of southern Idaho.

Probably the "soft caliche" of Breazeale and

Smith is not caliche but a soil lime accumulation horizon. It is not hard, and must be quite permeable if it can be dissolved and carried downward so easily in a degrading environment. This "soft caliche" also cuts across the soil group boundaries and must be of a pedo- loglcal origin. This material is the zone of lime accumulation. In time and with equilibrium conditions a cap could probably be developed on this "soft caliche". ELEVATION IN FEET Figure II. Cross-section of a railroad cut In arid an cut railroad a of Cross-section II. Figure between the present ground surface and the and surface ground thepresent between n tes 1961) others,and einta eosrts h correlation the demonstrates that region o fclcehrzn (rmSur, D.M. (FromStuart, horizon. caliche of top RY K A E W Y ER V O CALICHE NO OR 10 FEET RUD SURFACE GROUND AIH SURFACE C A F R U S CALICHE

25

DESCRIPTION AND DISTRIBUTION

Alluvial Fans

The Tucson area is located on a large alluvial fan which has been deposited by the ancestral Pantano

Wash. The main source of material has been in the head­ waters of this stream. The northern and highest parts of Tucson are located on a smaller fan that is derived from the Santa Catalina Mountains. Arroyo Chico is now present approximately at the toe of this fan. The caliche deposits are reasonably coincident with the present surfaces of these fans. The caliche within the

Tucson area is of several types and seems to be related to the source of supply and to position on the fan.

The Pantano drainage that deposited the main fan, which has its apex in the Cienega Gap area, includes large areas of limestone and silty sediments within its basin. The caliche on this fan is characterized by the predominance of fine grained materials and is the type of caliche described by Smith (1938) as characteristic of the Cemetery Terrace. In many areas, especially in

the central interior portions of this fan, the surface

has no cap or only a very thin cap locally, and only the

26 27 lower portions of the carbonate profile are present.

Much of the central part of the fan exhibits deposits that are more like soil lime accumulations than like caliche. This may be because only the very lowest parts of the profile remain after erosion. The caliche In the east and central portions of the fan show all the charac­ teristics of the normal caliche profile. Including the fractured caps, but the entire profile is very weak.

This caliche can be easily excavated by hand, and when portions of the profile are removed from the ground, they often crumble in the hand. This caliche forms low ridges with a gentle rounded outline. In general, the caliche becomes more indurated toward the toe of the fan.

The caliche on this fan is associated with rocks from the drainage of the Pantano Wash. Limestone frag­ ments are the most common rock type, especially in the southern part of the fan, along with some pieces of quartzite. A few pieces of andesite porphyry are present, and near the west edge of the fan some basalt fragments have been found. Many of the limestone fragments are good examples of Bryan’s Msolution faceted” pebbles (1929) with caliche deposited on the under side. The amount of gneissic material decreases away from the Catalina and

Rincon Mountain sources. South of Arroyo Chico and west of Pantano Wash, very little gneissic material is included in the caliche. 28

The northern and northwestern extensions of the

Cemetery Terrace along the Rillito Creek floodplain con­ tain a similar type of caliche. It is predominantly fine grained material and very similar to the caliche at approximately the same level on the main fan to the south, except that occasional cobbles and boulders of gneissic material are included and no limestone fragments are present.

In the central part of the fan, at the toe, a

small terrace occurs on the east bank of the Santa Cruz

floodplain. This is the lowest known exposure of caliche

in the area. This caliche matches all the descriptions

of "algal caliche". Many conversations with contractors

and equipment operators indicate that this is the most

difficult type to excavate in the area. It is composed

mostly of recemented fragments of caliche, most of which

are rounded. This area shows the greatest amount of

solution among those investigated.

In the northern part of the area, the caliche

is not the same as that previously described. It is

the type described as characteristic of the University

Terrace by Smith (1938). This caliche profile, in general,

is more difficult to excavate than that found associated

with the Cemetery surface. 29 This caliche is a cemented sand and gravel with larger fragments cemented by the carbonates. The materials are mostly gneissic and the larger cobbles and boulders are well rounded and appear to have come from the Catalina

Mountains. Some of these boulders are fresh in appearance, whereas others seem to be quite weathered, perhaps indi­ cating a reworking of a previous alluvial deposit. No associated limestone fragments have been found. The rock types that occur include red granite, diabase, andesite porphyry, and a few fragments of a vitrophyre in addition to the gneissic materials. Underlying this caliche, in many places, is a tight, very sharp, and angular red

sand that is slightly cemented and very compact that is almost as difficult to excavate as the caliche itself.

The only known source for all of these materials is at

Twin Hills, 22nd Street and Freeman Road.

The University Terrace type of caliche also has multiple caps. These caps are usually thin and are

separated by a few centimeters of soil or cemented sand

and gravel. The caps of the University type of caliche

are usually very hard and brittle, whereas the caps of

the Cemetery type of caliche is tougher and not so brittle.

Caps, of all types and locations have surfaces that show

many fractures that are similar (in appearance only) to

mudcracks. There are many possible explanations for these 30 fractures; dessicatlon, consolidation of underlying materials, or because they are rigid, they may fracture from stresses induced by ground tremors.

Most of the ridges of the area are capped by caliche; all of the higher ridges are capped. The higher the ridge, the more likely that it has been preserved by an indurated caliche cap. The ridges capped by Cemetery type caliche are more rounded in outline than those capped by the University type of caliche. Some of them in the extreme eastern part of the area seem to be pre­ served mostly by the large size of the rock fragments, as the caliche there is quite weak.

Strietz (1962) compiled an isopachous map of the caliche in the northern part of the area in the course of a hydrologic study. This map shows a general thick­ ening of the caliche to the southeast, which is the presumed source area, and thinning in areas of surface drainage.

Well logs of this area Indicate the presence of caliche at some depth below the surface. In a number of wells, several subsurface layers of caliche have been recorded. Some layers are quite thick and over 200 feet below the surface (see Maddox, i960, appendix). TANQUE FT. IQWF I I

g r a n t r d .

s p r f n w a .-v

BROADWAY

Contour I n t e r v a l 10 feet 32 Caliche on Sentinel Peak

The caliche found on Sentinel Peak, locally known as "A" Mountain, is unique in this area because the probable origin and source are known. This hill is capped by a vesicular basalt. The weathering of the calcic plagioclases in the basalt is the proposed source of the calcium. Precipitation picks up carbon dioxide in the atmosphere and forms a very weak carbonic acid solution. This weathers the calcic plagioclases and produces a calcium carbonate crust on the rocks and slopes below.

The calcium carbonate in the runoff is carried downhill and where evaporation or turbulence and a temperature rise, with subsequent loss of carbon dioxide, the calcium carbonate is precipitated from solution.

The increase in temperature is probably the most important agent in the precipitation of carbonates from the solution.

The caliche on Sentinel Peak ranges from very thin crusts on the basalt at or very near the top of the hill, to several feet in thickness at the bottom of the hill, depending on local relief. The caliche at the top of the slope is more accurately called a carbonate crust, but at the base of the hill, the caliche resembles con­ crete. Rocks of all sizes are cemented into a very hard, tough mass by the calcium carbonate. 33 The crusts are thin layers of calcium carbonate on the rocks and show evidence of being transient features.

Each rain probably dissolves and carries down hill as much carbonate as It deposits In this Instance.

Nearly every slope, except those that are very steep have this caliche at the surface. The main dralnageways give the appearance of white cemented ditches; these show most prominently on the hill at about the same distance below the basal contact of the upper basalt and at about the upper contact of the lower basalt.

The profile for this type of caliche varies

considerably and local relief Is the major Influencing

factor. Bare rock shows only an encrustation, whereas

rock with debris above it exhibits a more typical profile.

The cemented profile varies from a few inches thick to

several feet with boulders sometimes included. The

caliche profile generally increases in thickness downhill,

and is thicker and more indurated in the dralnageways.

In all cases where bedrock Is exposed, the profile Is

cemented from top to bottom.

The drainage ditches along the roads to the top

of Sentinel Peak are now lined with a caliche much like

concrete in appearance, with a cap over much of the con­

glomerate. These ditches were probably scraped to bare

rock when the roads were built, but the caliche is, in

places, about a foot thick now. 34 The caliche from this area is very difficult to dissagregate. The cemented sand and gravel portion breaks down readily with acid, but the indurated cap requires several treatments. SAMPLE TESTING PROCEDURES

Representative samples were taken from many exposures for laboratory testing. Because engineering projects might involve any part or the entire caliche profile, as much of the profile was sampled as possible.

Samples were marked in the field to denote the top when taken from the profile. Usually only the upper foot, or less, could be sampled in this manner. The remainder of the caliche profile was too friable to be removed in sizeable pieces. Other locations were sampled from top to bottom of the caliche profile to determine the carbonate content in relation to position of the sample within the profile.

The caliche samples were treated with 3 normal

HC1 to determine the percent of carbonate as cement.

This treatment usually did not dissolve all fragments of the cap, and in order to prevent loss of the included limestone fragments present in some of the caliche, the samples were then treated in a boiling 5% NaCO^ solution and then placed in the acid again. The sodium carbonate method is a standard method for dissaggregating clays; it also aids in removal of silica, which may have been

35 present in the cementing medium. The HCl probably would have dissolved the carbonates, given sufficient time, but the permeability of the cap material is very low and the time required would have led to a complete breakdown of the limestone fragments also. In some parts of the area, the silt and clay content seems to be a significant factor in the cementation of sand and gravel into caliche.

The caliche profile is one of increasing carbonate cementation upward toward the surface. All of the sedi­ ments examined exhibited some reaction to the acid, even those below the caliche profile proper. The sediments below the cemented caliche zone may contain as much as five percent carbonate, none of which is visible. When the carbonate content is greater than about ten percent, it is obvious to the unaided eye. Even then the sand and gravel is not well cemented. Some drusy calcite may be found in the larger openings, but it does not completely

fill the openings.

In the caliche profile proper, the alluvium is obviously cemented with carbonate. The carbonate seems

to be completely interstitial, and no evidence has been

found of displacement by growth of the caliche. This

zone contains 25 to 35 percent by weight of carbonate

and most of the rest of the material is sand and gravel

sizes with some silt and minor clay and few larger

fragments. 37 At the top of the caliche profile is a dense, laminar cap. This cap contains ?8 to 91 percent carbonate by weight, 6 to 16 percent silt, and 3 to 6 percent clay in the samples tested. Occasionally larger fragments are present, but they seem to be completely surrounded by carbonate and are not in contact. Some of these larger quartz particles have a frosted surface. These caps are always fractured and have laminations that are parallel to the surface.

Sand and gravel particles freed from the matrix during carbonate determination were examined to see if any characteristic lithologic types could be determined.

Limestone fragments were not found in the University type of caliche, and very little gneissic material was found in the other deposits, except those from the north- westernmost parts of the Cemetery Terrace. The only rock type common to all areas is the andesite porphyry, but very few fragments were found; this type of rock was absent in some of the samples that were examined.

Samples were trimmed and broken to allow deter­ mination of their unconfined compressive strength. The samples included as much of the caliche profile in them as possible for these tests. Trimming these samples was difficult in the portions below the cap and most of the samples were not good geometric forms, thus effective 38 cross-sectional areas had to be computed. The values obtained are considerably lower than those reported by

Gile (1961). His samples consisted of a cube cut from

the cap only, however the writer's tests performed on the

cap alone approached Gile's results.

The compressive strength values for normally oriented samples ranged from 218 psi to 1,120 psi. Tests on two samples which were oriented at right angles to

the normal orientation produced values of 2?00 psi and

3360 psi. All samples tested had a cap at the top with

varying thicknesses. Except for the laterally oriented

caps, there seemed to be no relation between the thickness

of the cap and the compressive strength of the caliche

sample. TABLE I

UNCONFINED COMPRESSIVE STRENGTHS OF SOME

CALICHE SAMPLES IN THE TUCSON AREA

21st* Street and Rubio

470 psl 805 psl 215 psl

E. 14th. Street near Tuller School

235 psl 2700 psl* 1120 psl

E. 2nd Street and Palm

218 psl 470 psl

Glenn and Swan Road

320 psl 280 psl

4th. Avenue and Freeway

3360 psl*

*Cap only tested at 90° to normal orientation GEOPHYSICAL INVESTIGATIONS

Earthwork is very competitive and bids involve large amounts of money. Estimators involved in excavation must plan for every contingency in order to make a profit.

One of the most used "modem** techniques for estimating costs of excavation is refraction seismic surveying.

Many contractors use this method for fast, economical, and reliable information for planning excavation operations in soil and rock.

The seismic Information for this report was obtained with the use of a portable single channel timer utilizing a single geophone. The energy is imparted to the ground by means of a 12 pound hammer and received at the geophone. The time of the first arrival is read at the timer in milliseconds.

Church (1964) made a study of more than 150 engineering operations in the southwest with subsequent investigation after the initial work was accomplished.

Some of this work was still in progress at the time of his writing. He made the following statements in his paper:

1. Shock wave velocities are directly related to the degree of consolidation of the media.

40 41

2. Both shock wave velocities and depths to the denser materials can be determined by refraction studies.

3. Excavation costs may be estimated, qualitatively by seismic velocities of the media, and quantitatively by volume of material derived from depth determinations.

Church included the following chart on rlppablllty in relation to seismic velocities of the material. This is for a heavy tractor; a tractor-ripper combination having a total weight of 100,000 to 110,000 pounds and an engine rated at 380 to 460 horsepower. Lighter tractor ripper combinations do not follow a tifcrict linear relation in their ability to rip materials.

TABLE II

soft medium hard ripping ripping ripping

Shock wave velocities (fps) 1500-3000 3000-4500 4500-6000

Production/60 minute working hour (yds3)3200-950 950-350 350-120

Direct job unit cost (cents) 1 to 3 3 to 10 10 to 34

Church also has included a special sedimentary

category: "Desert residuals and conglomerates: These recent deposits in many cases have been fairly tightly

cemented in a few thousand years. Velocities reach

3500 fps, calling for up to medium ripping." 42

The Caterpillar Tractor Company (i960), as a service to their customers, published a Hlppability

Velocity Chart based on refraction seismic surveying.

This chart, including caliche, is as follows:

TABLE III

Could be ripped * 3000-5500 fps

Marginal zone : 5500-8000 fps

Could not be ripped: 8000-10,000 fps

Of special interest is the fact that caliche has been included on every version of these charts.

Lacy (1964) in the Tucson area determined seismic velocities of 1000 to 15,000 fps for the University

Terrace and 500 to 800 fps for the Cemetery Terrace.

These are average values including both caliche and non­

caliche bearing soils.

It was hoped that seismic velocity differences

would be sufficiently distinctive to enable mapping within

the area. Unfortunately, this was not the case. Field

work showed that Church was correct; seismic velocities

vary with the amount of consolidation and cementation,

and thus with the vertical position in the caliche profile.

The velocities in the caliche have a large range

and only general correlations can be made. Velocities

below 2000 fps occur in the absence of caps where only the upper portion of the cemented sand and gravel parts of the caliche profile are present. In a few instances, profiles with a very thin, highly fractured cap also produce velocities within this range. Caps an inch or less in thickness, with only a few minor fractures have seismic velocities between 2000 fps and 3200 fps. Caps thicker than one inch are present where velocities exceed

3200 fps and are fairly continuous. The velocities seem to be related to the amount of fracturing in the caps.

Higher velocities are associated with less fractured and generally thicker caps. Considerable lateral variations occur within very short distances and seismic investi­ gations of local sites should reveal such changes. There­ fore, the method is useful in site investigations.

In some areas (especially the sites at 1500 E. 36th

Street and the east end of 14th Street near the Tuller

School) where the caliche cap is well developed, it was possible to map the larger fractures by the seismic velocity curves. Displaced sets of points on seismic curves with the same slope coincided exactly with locations of fractures recorded during the preliminary measuring and description of the area. In areas of little or no cap development, this was not observed. In areas that are very highly fractured, even with good cap development,

the velocities are somewhat lower and no displaced sets of points could be determined. 44

In areas where large boulders are present In the caliche, the velocities are slower than elsewhere; this relation is independent of cap presence and development. 45

DISTANCE

Figure IV. 14th Street southwest of fuller School

Cap very Indurated, 2-4 Inches thick, fracture in cap corresponds to break in seismic curve. 46

1 I ■ i___ _.i o 10 20 30 4 0 5 0 DISTANCE

Figure V. Corner of Speedway and Campbell Avenue

Cap 1-2" thick, very fractured, many large gneiss boulders (to 12* dia.) 47

DISTANCE

Figure VI. Southwest corner Speedway and Queen Avenue near bottom of cemented sand and gravel portion of the caliche profile, carbonate content 18#. THE CALICHE PROFILE

The generalized caliche profile in the Tucson area is one of increasing cementation from bottom to

top. The base of the profile usually consists of sand

and gravel which is only slightly calcareous, and is not

cemented. Frequently, this portion of the profile will

show cut-and-fill structures.

The next higher portion of the profile is more

calcareous and carbonates are visible. Drusy calcite

occurs in some places (Guild, 1910). The sand and gravel

is weakly cemented near the top of this part of the

caliche profile.

The next zone upward exhibits a greater degree

of cementation and the material is entirely cemented.

Essentially this is a cemented sand and gravel, or a

conglomerate cemented by calcium carbonate (possibly with

some silica). This zone is usually 1 to 2 meters thick,

but will vary with the original permeability of the

material. On Sentinel Peak and Tummamoc Hill this zone

may be only a few centimeters thick.

The uppermost zone or caprock also varies in

thickness. It is a very hard (3 or more on the Mohs

scale), laminar, and the surface is smooth and flat or

48 #9

Soil cover may be present •• •« •' Cap, may be multiple

Cemented sand and gravel

Sand and gravel Incompletely cemented by carbonates

< •• ; i p-?. •° '• e - b ^ - e » . '

Sand and gravel with no visible % o ’v » V 0'-.<-- • . *'#'"» a.*. » carbonates

o » o' .0 0 - •:.:v:

"» • Sediments may show scour i o%- • ° /o^C

All contacts are gradational except at the cap.

Figure VII. Generalized Caliche Profile 50 exhibits smooth undulations. This surface often exhibits many recemented fractures, especially if it has been exposed for some time. This zone is high in carbonate content and the larger particles within the cap are separated by cement and are seldom in contact. This cap- rock contains small amounts of silt and clay and a few larger particles. The toughness of the caliche may be related to the clay and silt content.

Frequently the cap of the profile contains several distinct layers that are separated by earthy or less indurated material. This may result from floods that wash material over a cap that is exposed at the

surface.

Radiocarbon dating (Buol and Yesiloy, 1964)

indicates an upward growth as the amount of m o d e m

carbon increases upward in the profile.

Growth of the Caliche Profile

Drill-hole records and open excavations indicate

that more than one layer of caliche exists below the

surface in this area. Any attempt to explain the

environment of caliche deposition must also account for

these multiple layers which have often been explained

by groundwater deposition in the past.

Breazeale and Smith (1930) produced a caliche-

like material in the laboratory. Calcium bicarbonate 51 was allowed to drip into a cloth bag filled with sand and gravel which hung in an oven at a temperature of about 90°C.

The flow of the bicarbonate solution was adjusted so that as much of the solution as possible evaporated within the sand and gravel. After several weeks a core of moder­ ately hard caliche-like material, that resembled the natural product, was obtained.

Most of the waters in the area contain some carbonates in solution and, as previously noted, all of the soil profiles examined reacted with acid whether carbonates were visible or not. Water in the soil, whether runoff with carbonates already in solution or meteoric water that picks up carbonates from the soil, percolates down through the soil under the influence of

gravity. This action leaves the soil and sediments near

the surface in an unsaturated condition with films of water around the grains and along the sides of the pores.

This water that remains near the surface (upper 2-3 feet),

then contains some carbonates in solution. Normally in

this climate, the rainfall is of short duration and occurs

as thundershowers. As the atmosphere warms up, especially

in the summer, evaporation takes place. Evaporation of

the water from the soil concentrates the carbonates in

the intergranular films of water. When sufficient

evaporation has taken place, the calcium carbonate is 52 precipitated as solid material around the grains and along the sides of the soil pores. Capillary action in the sediments will supply additional water for evaporation.

With time and many repetitions of this process, the soil openings in the sediments will fill up, the size of the pores will be reduced, more water will be held near the surface and evaporated there and carbonate concentration increased, and then that part of the profile is cemented into caliche.

When all the pore space is filled, very little water can penetrate through the profile and surface run­ off will result. Some water, with dissolved carbonates assimilated from carbonate material it has already passed over, will remain at the surface, either as thin films

or shallow puddles. This water then would be evaporated

and development of the cap will begin. This process

would produce the smooth undulating laminar caps of the

caliche profile. According to Vinson (1916) and Griffin

(1920), lime-secreting algae may also help to develop

this part of the profile.

This process can take place on large surfaces

such as the surface of an alluvial fan or on the bottom

and sides of small drainageways. Miller (1937) reports

on drainage lines with bottoms and sides composed of 53 caliche in eastern Saudia Arabia. This caliche is harder than the surrounding material which has been eroded away, leaving caliche capped ridges as a fossil drainage pattern. Somewhat similar features are developing on Sentinel Peak where the bottoms and banks of the drainageways are lined with caliche.

The multiple caps found at the surface of many caliche layers are explained by the same process. Once a surface developes a cap, runoff from the rains will move over it rapidly. This runoff may carry some sediment with it. The process of carbonate deposition builds a cap over this new layer of material. Apparently the evaporation draws the water to the surface of the new material and deposits the carbonates there. This process results in a new, thin cap a few centimeters above the previously formed cap with uncemented or slightly cemented material between. Locally several thin caps may be found within a few inches above the main cap of

the caliche layer. Likewise the stray, individual pieces of sand and gravel frequently observed attached to the

cap can be explained. A single fragment can be rolled along and come to rest on the cap. The laminations in

such cases seem to wrap around the fragment and cement

it to the top of the cap. 54

To develop the caliche profile, static conditions approaching equilibrium between erosion and deposition must be present* As long as sedimentation is continuous, permeability is maintained and the carbonates are not concentrated to develop the caliche profile. Once deposition is reduced to material from solution or colloidal suspension, caliche accumulation begins. If erosion is dominant, the accumulation of carbonates will be removed before they become concentrated into the caliche profile. In effect, a surface of weathering and accumulation of weathering products, with a very gently

sloping surface to prevent the materials in solution from being carried away must exist to develop the full caliche profile.

This is one explanation for not finding caliche

beneath the major drainages of the area. The materials

of the stream bottom certainly are not in a static sur­

face condition. Each time water flows in the streams,

the sediment is moved and new material is deposited.

Before these streams became intermittent, continued sat­

uration probably did not allow the process of deposition

to operate.

Source of Cementing Agents

The source of the carbonate cementing material

is readily determined for the Sentinel Peak area. The 55 caliche in the alluvial basin area requires a different source.

The Pantano Wash drainage basin contains large outcrop areas of Paleozoic limestones and many fragments of the limestones are found on the fan built up by ancestral Pantano Wash. This is the proposed source of the carbonate cementing agents in the main fan. This limestone and the fragments on the fan supply additional carbonates to the waters passing over and around them.

This carbonate in solution is then deposited on the fan and may eventually be moved into the caliche profile.

This is a process of dissolution and concentration.

Because all waters on the fan move down slope, the tendency is for the carbonates in solution to accumulate near the toe of the fan where the slopes are more gentle.

Carbonate material may be dissolved and transported many times before it becomes a part of the caliche profile.

The weathering of the feldspars in the Santa

Catalina and Rincon Mountains supplies some calcium and silica to the waters which naturally contain COg. This and perhaps a reworking of some previously existing

caliche nearer the foothills of the mountains have supplied

the cementing agents within the sediments of the University

Terrace.

In the Southwest, caliche is usually considered

to be cemented only by carbonates. This may be true in general, but there may also be some silica in the cement.

Laboratory tests have indicated that carbonate is present in large percentages. However chunks of caliche placed in dilute HC1 do not always disaggregate. The lower portion of the caliche profile comes apart easily in the acid, but the caps and sometimes the 2 or 3 centimeters immediately below the cap, do not fall apart with the acid treatment alone. When placed in boiling sodium carbonate, these portions do come apart. This may in­ dicate that some silica is present in the caliche as a cementing agent, or it may be that the fine silts and clays are helping to bind the caliche together. The HC1 may not be able to dissolve the caliche caps because of the very low permeability of the cap and because insufficient time was allowed, although some samples were immersed in HC1 for up to 3 months.

Silica could be released from the feldspars of the Catalina Mountains and could also be derived from the silts in the area which Pantano Wash drains. Several investigators; Krauskopf (1956), Siever (1957. 1962), and Gifford and Prugoli (1964), have shown that some

silica could be included in the cementing material. CALICHE AND ENGINEERING

The greatest significances of caliche in engineering is the increase in cost of excavation. The fact that caliche may hold water near the surface, due to its lack of permeability is of lesser importance♦

Many light structures have been built on caliche in the older parts of Tucson and have no defects traceable to the caliche as foundation material.

When caliche is present, costs of excavation increase. Normally heavier equipment is required for its removal. Often light equipment is brought to a location and is found to be inadequate; then heavier equipment must be brought in at added expense. If it is known or thought that caliche is present then this heavier equipment can be brought to the site first.

The heaviest equipment known to be used to remove the most difficult caliche in this area is a D-9 Cater­ pillar tractor with a hydraulic ripping tooth, or its equivalent. The normal procedure, where scrapers cannot do the work alone, is to rip the caliche and then push the scraper with a tractor. Fortunately, the hardest material is the cap, which is usually only a few inches thick, is quite brittle, and often cracked and broken.

57 58 Once this cap is penetrated and removed, the excavation

is much easier. Where the caliche must be removed to meet grade requirements, the usual practice is to remove

the entire cemented portion of the profile. If areas of

more rigid material are left surrounded by uncemented

material, the possibility of differential compaction

exists. If the caliche or soil profile is uniform at

grade level the problem is not crucial. This material,

if crushed, watered, and carefully compacted, makes a

stable subbase because it partially recements itself in

a short time. It must be mixed with additional material

to become a stabilized base material.

As indicated by the seismic velocities (see table

IV) there is probably no caliche in the area under con­

sideration that cannot be ripped. Some of the caliche,

however, may need rather large equipment for its removal.

This is confirmed by conversations with many contractors

and equipment operators. Very often the difficulty in

ripping and excavation is related to the size, shape, and

rock type of the included material. The most difficult

to excavate are those deposits which are essentially

cemented boulders and gravels. The ripper tooth and

scraper blades often just slide off the fairly smooth and

rounded gneiss boulders. The Cemetery Terrace deposits

of the interior of the fan and along Rillito Creek 59 Floodplain are among the easiest to excavate# Frequently this caliche layer can be removed by the scraper alone or by a small bulldozer. Very often this material is easily removed by small trenching machines used to dig utility line trenches, even where the caliche exceeds two meters in thickness.

The most difficult non-conglomeratic caliche to excavate appears to be in the southern part of Tucson.

It occupies an approximate area bounded on the east by

6th Avenue, the Benson Highway to the south, extends to the limit of mapped caliche on the west, and approximately l?th Street to the north. North and east of this area, this type of caliche is probably present under softer materials or may grade upward into softer materials.

This is the lowest exposed caliche in the area, and seems

to be largely composed of the "algal" type of caliche, at least in its upper portions. Smith (1938) includes

this area in his Jaynes Terrace, and it lies below the

general elevation of the Cemetery Terrace deposits. The material, other than carbonates, is mostly silt with some

clay and many reworked, rounded, cemented fragments of

caliche. It is very difficult to disaggregate. Possibly

this deposit, being at the very toe of the fan, and

perhaps a part of the river bank, was partially formed

by the evaporation of seeps, and since being exhumed by 60 erosion at a recent time, it has undergone extensive casehardening. The difficulty in removing this material is as much one of toughness of the deposits as it is of hardness. This may be because of the fine material in

the deposit. The thickness of this particular unit is unknown, but exceeds 1& meters at the thickest observed

exposure. Some tuff and basalt fragments have been

found on the surface of this unit, but none within the

caliche itself. The only caliche more difficult to dis­

aggregate is the caliche from Sentinel Peak. CONCLUSIONS AND RECOMMENDATIONS

Conclusions

In summary, several conclusions have been drawn:

1. To form the caliche in this area several conditions must exist. A source of lime, a climate in which potential evaporation exceeds the rainfall, per­ meable sediments, slopes sufficiently gentle to allow the carbonates to accumulate, and stable conditions with respect to erosion and sedimentation are required.

2. In the Tucson area, the basalts of the mountains to the west and the Paleozoic limestones to the east are the sources of the lime. The gneissic com­ plexes of the Rincon and Santa Catalina Mountains furnish some cementing materials.

3. The dense caps probably form at the surface.

The rest of the caliche profile represents in place cementation of the sand and gravel. The depth and amount of cementation is probably related to the original permeability of the sediments.

4. The caliche of the Cemetery Terrace is essentially the B horizon of a fine grained soil profile that is highly cemented by calcium carbonate; a cap occurs locally.

61 62

5. The terraces seem to have subterraces. One of the lower subterraces of the Cemetery Terrace, next

to the river, has the most difficult to excavate caliche

in this area. It apparently represents the "algal"

caliche deposits in this area.

6 . The induration of the caliche increases

toward the toe of the fan, and represents a surface of

weathering and accumulation.

?• University Terrace deposits overlie the

Cemetery surface in the northern one-third of the area,

and are composed of gneissic boulders, gravel and sand

cemented into a caliche conglomerate by the carbonates.

Some of the materials seem to have been reworked from an

older alluvial deposit.

8 . The University Terrace caliche is difficult

to work because of the large size and shape of the in­

cluded rocks, as well as the firm cementation.

9* The University Terrace material is a remnant

of a debris apron or series of coalescing fans that pre­

viously extended into the Catalina Foothills. Recently

the University Terrace deposits have been isolated by

the downcutting of Rillito Creek.

10. A fracture in the sediments of the basin in

the vicinity of present day Rillito Creek must be

postulated. This is the most obvious explanation for 63 the m o d e m drainage pattern of Rillito Creek and Pantano

Wash. It explains why the stream has cut into the slope and isolated the southern remnant of that slope.

11. Gneissic material south of Arroyo Chico decreases rapidly and is present only as scattered frag­ ments. North of Arroyo Chico the University Terrace deposits are composed entirely of gneissic materials.

12. The deposition of materials correlative with the University Terrace deposits is still doubtful.

It seems that little coarse material was being added to the southern portion of the area during that period of deposition. Coarse material is not present to the

degree it is in the University Terrace deposits and is mostly limestone with some quartzite.

13* Seismic velocities are related to the amount of cementation and degree of induration. The

thicker the cap and the more continuous it is, the

greater the velocities. The cemented sand and gravel

portions of the profile have slower velocities.

14. It would be impractical to attempt to make

a seismic velocity map of the caliche of the entire area,

due to the irregular lateral variations in the caliche.

Each site should be investigated as an entity and

differences in induration should be readily observed in

small areas. Of equal importance is the size and shape 64 of the included material in the caliche. The velocity varies with the degree of induration, and different velocities are recorded at different levels within the profile; velocity increases upward in the caliche profile.

Recommendations

As a result of this investigation, recommendations can be made.

1. The entire area within the city and in pro­ posed areas of further expansion should be covered by a series of engineering geology maps similar to the U. S.

Geological Survey soil engineering maps. This would in­ clude all of the soil (and caliche) engineering properties pertinent to the problem. This would be an aid to the construction industry and to planning and zoning commissions. These maps would delimit low density sensitive soils, the areas of troublesome caliche, and the areas of "easy" construction. On this basis a more efficient method of community planning could be devised.

2. A program of careful sampling and radioactive dating should be conducted. Possibly a rate of growth of the caliche profile and age of the surfaces represented can be determined.

3. A careful, complete, chemical analysis of the caliche could lead to a better understanding of natural 65 cementing agents. Also a continuation of Breazeale and

Smith’s experiments in producing caliche in the laboratory might provide useful information as to origin.

4. A careful study of drillers logs, even though

somewhat unreliable, should reveal the presence or absence of previous equilibrium surfaces within the fan.

If these layers can be mapped as surfaces and dated, and

the volume of material between the caliche layers deter­ mined, an estimate of the rates of alluvial accumulation

can be made. USES OF CALICHE

Caliche is considered a nuisance in this area; many contractors have lost money because of its presence and crops and lawns do not grow on it. At least one road failure is blamed on the caliche (Krupp, 1958).

This is the road to the Silver Bell Mine northwest of

Tucson. Apparently the caliche was mixed in with some borrow material and was of the non-indurated type with large amounts of included clay. Careful engineering and inspection probably could have avoided this failure.

Caliche does have some uses and has been used as a foundation for light structures with satisfactory re­ sults. The building at the corner of Broadway and Main in downtown Tucson has been standing for many years and is built on a caliche base.

Blake (1901) reports that calcined caliche with sand makes a strong quick-setting mortar or cement and apparently caliche was used as a foundation at Casa

Grande Ruins.

Reeves and Suggs (1964) report that at Bushland,

Texas, Southwestern Portland Cement Company has recently

constructed a plant to utilize caliche for the manufacture

of portland cement.

66 67 Breazeale and Smith (1930) reported that caliche was burned for lime with good results and that caliche was used as a binder with sand and gravel for road material.

Bryan (1925) stated that on the highway leading south from Tucson, caliche mixed with sand and gravel was used as a satisfactory road metal.

The Texas State Highway Department (1940) set up standards for caliche-cement stabilization because much of their aggregate in West Texas contains caliche

(Roads and Streets, 1959), and nothing better is available for base material.

On the academic side, many authors have suggested

the use of caliche formations as correlations of the

inter-glacial stages. More work needs to be done to

determine the exact climatic requirements for caliche

formation before this material can be used as a paleo-

climatic indicator. REFERENCES CITED

American Geological Institute, i960. Glossary of geology and related sciences, second edition: Am. Geol. Inst., J. V. Howell Chairman, Williams and Heintz Lithograph Corp., Wash. D.C., p. 42.

Antevs, Ernst, 1955a. Geologic-climatic dating in the west: Am. Antiquity, v. 20, p. 31?-335»

______, 1955b, Geologic-climatic method of dating in geochronology: Physical Science Bull. No. 2, Univ. Ariz. Bull. Series, v. 26, n. 2, Univ. Ariz. Press, Tucson.

Babcock, H. M., and Cushing, E. M., 1958, Recharge to groundwater from floods in a typical desert wash, Pinal County, Arizona: Ariz. Geol. Soc. Guidebook for field trip excursions in southern Ariz. p. 221. Reprinted from 1942 Trans. Am. Geophys. Union.

Blake, W. P., 1901, The caliche of Arizona: an example of deposition by the vadose circulation: Am. Inst. Mine Engr. Trans., v. 31* P* 220-226.

Blank, H. R., and Tynes, E. W . , 1965. Formation of caliche, in situ: Geol. Soc. Am. Bull., v. 73, p. 1387- 1392.

Bretz, J. H., and Horberg, Leland, 1949, Caliche in southwestern New Mexico: Jour. Geol., v. 57. p. 477-491.

Breazeale, J. F., and Smith, H. V., 1930, Caliche in Arizona: Ariz. Agr. Expt. Sta. Bull. 131.

Brown, C. N., 1956, The origin of caliche on the northwest Llano Estacado, Texas: Jour. Geol., v. 64, p. 1-16.

Bryan, Kirk, 1925, The Papago Country, Arizona, geographic, geologic, and hydrologic reconnaissance: U.S. Geol. Survey Water Supply Paper 499, P» 370.

______, 1929, Solution faceted limestone pebbles: Am. Jour. Sci., v. 18, 5th series, p. 193-209.

68 69 Buol, S. W., CalcisoIs in Arizona: Progressive Agr. in Ariz., College of Agr., Univ. Ariz., v. 16, no. 6.

______, and Yesiloy, M.S.A., 1964, A genesis study of a Mohave sandy loam profile: Soil Sol. Soc. Am. Proc., v. 28, p. 253-256.

Caterpillar Tractor Company, 1959, Ripping with seismic analysis: Caterpillar Tractor Co., Form 717- 33793., Peoria, 111.

______, 1961, Handbook of ripping: Form 728-33704-1, Caterpillar Tractor Co., Peoria, 111.

Church, H. K., 1964, Geophysical examination can make earthmoving a profitable science in the southwest: Southwest Contractor and Buildfer, Mar, 13, 1964.

Cooley, M. E., 1961, Description and origin of caliche in the Glen-San Juan Canyon region, Utah and Arizona: Ariz. Geol. Soc. Digest, v. 9.

Damon, P. E., Long, A., and Sigalove, J. J., 1963, Arizona radiocarbon dates IV: Radiocarbon, v. 6, p. 283- 301. Univ. Ariz. Geochronology Contribution No. 60.

______, Haynes, C. V., and Long, A., 1964, Arizona radiocarbon dates V: Radiocarbon, v. 6, p. 91- 107. Univ. Ariz. Geochronology Contribution No.88.

Ellas, M. K., 1931, The geology of Wallace County, Kansas, Kans. State Geol.: Survey Bull. 18, p. 140.

______, 1948, Ogallala and post-0gallala sediments: Geol. Soc. Am. Bull., v. 59, P* 609-642.

Fay, A. H., 1920, A glossary of the mining and mineral industry: U.S. Bureau of Mines Bull. 95*

Forbes, R. H., 1905, in Lee, Underground waters of the Salt River Valley: U.S. Geol. Survey Water Supply Paper 136, p. 107-111.

Frye, J. C., 1954, Valley erosion since Pliocene Malgal limestone'* deposition in central Kansas: Kans. State Geol. Survey Bull. 60.

Gifford, R. 0., and Frugoli, D. M., 1964, Silica source in soil solutions: Science, v. 145, P» 386-388. 70 Gile, L. H., 1961, A classification of calcium horizons in soils of a desert region. Dona Ana County, New Mexico: Soil Sci. Soc. Am. Proc., v. 25, P- 52. Glinka, K. D., 1914, The great soil groups of the world and their development: (translated by D. F. Marbut, 192?)• Edward Bros., Ann Arbor, Mich., P. 157-159. Gould, C. N., and Lonsdale, J . T., 1926, Geology of Texas County, Oklahoma: Okla. Geol. Sur. Bull. 37* P. 29-33. Griffin, S. W., 1920, Caliche: a study of so called desert limestones of Arizona. Were biological factors concerned in its deposition: Unpub. Univ. of Ariz. Master’s thesis.

Guild, F. N ., 1910, Mineralogy of Arizona: The Chemical Pub. Co., Easton, Pa., p. 48-54.

Hawker, H. W. , 1927, Soil survey of Hidalgo County, Texas and the stages of their lime accumulation: Soil Sci., v. 23, p. 475-485.

Krauskopf, K. B., 1956, Dissolution and precipitation of silica at low temperatures: Geochim. Cosmochim. Acta., v. 10, p. 1-26.

Jennings, W. D., and Sweeting, M. N., 1961, Caliche psuedo-antidines in the Fitzroy Basin, Western Australia: Am. Jour. Sci., v. 259. P* 635-639*

Judson, Sheldon, 1950, Depressions of the northern portions of the southern High Plains of eastern New Mexico: Geol. Soc. Am. Bull., v. 61, . P* 253-274.

Krupp, L. M., 1958, Better roads for lower costs: Mining Engr., v. 10, p. 1167-1168.

Lacy, W. C., 1964, Geological causes of foundation failures in the area of Tucson, Arizona: Trans. Am. Inst. Min. Engr., v. 299. p. 40-44.

Lamplugh, G. W . , 1907, The geology of the Zambesi Basin and around Batoka Gorge: Quart. Jour. Geol. Soc. London, v. 63, p. 162-276. 71 Lee, W. T., 1905. Underground waters of the Salt River Valley, Arizona: U.S. Geol. Survey Water Supply Paper 136, p. 107-111.

Maddox, G. E., 1969. Subsurface geology along northwest Rillito Creek: Unpub. Univ. of Ariz. Master's thesis.

Marbut, C. P., 1933. Soils of the Great Plains: Assoc. Am. Geog. Annals., v. 13, p. 41-66.

Miller, R. P., 1937. Drainage lines in bas-relief: Jour. Geol., v. 45, p. 432-438.

Motts, W. S., 1958, Caliche genesis and rainfall in the Pecos Valley of southeastern New Mexico: (abs.) Geol. Soc. Am. Bull., v. 69. P« 1737•

Price, W. A., 1925, Caliche and psuedo-anticlines: Am. Assoc. Petrol. Geol. Bull., v. 9. P» 1009-1017.

______, 1933, Reynosa problem of south Texas and origin of caliche: Am. Assoc. Petrol. Geol. Bull., v.17. p • 488—522.

______, 1940, Origin of caliche: (abs.) Geol. Soc. Am. Bull., v. 51, P» 1938.

______, 1965, personal communication.

Reeves, C. C., and Suggs, J. D., 1964, Caliche of central and southern Llano Estacado, Texas: Jour. Bed. Pet., v. 34, p. 669-672.

Roads and Streets, 1959, Flexile base specialist. West Texas style: Roads and Streets, v. 102, Nov. 1959, P. 54-56.

Sayer, A. N., 1933. Groundwater resources of Duval County, Texas: U.S. Geol. Survey Water Supply Paper 776, p. 65-72.

Sidwell, R., 1943, Caliche deposits on the Southern High Plains, Texas: Am. Jour. Sci., v. 241, p. 257- 261.

Siever, R. M. , 1957. The silica budget in the sedimentary cycle: Am. Min., v. 42, p. 821-841. 72

______, 1962, Silica solubility, 0-200° C, and the diagenesis of siliceous sediments: Jour. Geol. v. 70, p. 127-150.

Smith, G. E. P., 1938, The physiography of Arizona valleys and the occurrence of groundwater: Univ. Ariz. Agr. Engr. Tech. Bull. 77•

Soil Survey Staff, 1951» Soil Survey Manual: U. S. Dept. Agr. Handbook 18.

______, i960, Soil classification system— ?th approximation: U. S. Dept. Agriculture.

______, 1964, Soil classification system— 7th approximation, memorandum on nomenclature: U. S. Dept. Agriculture.

Strietz, Robert, 1962, Subsurface stratigraphy and hydrology of the Rillito Creek-Tanque Verde Wash area, Tucson, Arizona: Unpub. Univ. of Ariz. Master's thesis.

Stuart, D. M., Fosberg, M. A., and Lewis, G. C., 1961, Caliche in southwestern Idaho: Soil Sci. Soc. Am. Proc. v. 25, p. 132.

Swlnford, Ada, Leonard, A. B., and Frye, J . C., 1958, Petrology of the Pliocene pisolitic limestone in the Great Plains: State Geol. Sur. Kans. Bull. 130, p. 97-116.

Texas Highway Department, 1940, Caliche-cement stabili­ zation: Information Exchange No. 83, p. 5-22.

Theis, C. V., 1936, Possible effects of groundwater on the Ogallala Formation on Llano Estacado: (abs.) Wash. Acad. Sci. Jour., v. 26, p. 390-392.

Trowbridge, A. C., 1926, Reynosa Formation in Lower Rio Grande region, Texas: Geol. Soc. Am. Bull., v. 37. p. 455-462. Twenhofel, W. H., 1950, Principles of sedimentation, 2nd. ed: McGraw-Hill Book Co., New York.

Udden, J. A., 1923. The "rimrock" of the High Plains: Am. Assoc. Petrol. Geol. Bull., v. 7. P» 72-74.

Van Siclen, D. C., 1957. Cenezoic strata on the south­ western Osage Plain of Texas: Jour. Geol., v. 65. p. 47-60. 73 Vinson, A. E., 1916, 27th annual report: Ariz. Agr. Expt. Sta., p. 298-299.

Weeks, W. W ., 1933. Lissle, Reynosa and the upland terrace deposits of the coastal plain of Texas between Brazos River and Rio Grande $ Am. Assoc. Petrol. Geol. Bull., v. 17, p. 4^3-487.

Woolnough, W. G., 1927. The duricrust of Australia: Jour. Roy. Soc. New South Wales, v. 58, p. 1-53• APPENDIX I 74

The surface six Inches of soli Is a loamy sand containing 23 percent of material not passing through a 2 mm. selve. This coarser material has the appearance of lime concentrations but a close examination shows them to be only lime-coated pebbles. Immediately below this loose surface material, as shown In figure VII , is a dense layer of softer caliche which has a lower lime content. Another half-inch of softer caliche, very compact material Is found under this chalky layer and as in the upper compact layer its lime content is higher than the less dense IOO-?S?S^S strata above or below the one extending Zb Inches below. At a depth of 13 inches a little gravel appears to be mixed with the lime and the whole is cemented into a hard, solid mass.

The percentage of sand and gravel in­ 150 creases slightly to a depth of 30 inches where a vein of gravel is encountered. These llme-and-gravel mixed deposits contain in the neighborhood of 40 percent lime which is the maximum amount possible in this type of soil as only the pore spaces are to be filled.

The gravelly strata which underlie the caliche-cemented layers become less rich In lime with Increased depth until at the 82 inch depth only percent lime is found. Below this only traces of lime occur to the bottom of the hole, 158 inches below the surface. The log of a well drilled to furnish water for the estates shows a repetition of these caliche strata down to a depth of at least ?1 feet, and possibly more, although caliche as such is not indicated In the log below this level.

Figure VIII. Illustration showing a typical caliche profile. From Pinal Soil Series, El Encanto Estates. (After Breazeale and Smith, 1930) 75

TABLE IV

SELECTED SEISMIC VELOCITIES AND LOCATIONS

Velocity Condition of Cap and Location ft./sec. Location Within Profile

New Civil Engineering Bldg. one foot below cap, cemented sand and 2nd St. and Palm 2000 gravel, 32$ carbonate

E. side of Swan Rd., 300 ft. very thin, very fractured cap, overall south Glenn and Swan Rd. 2800 carbonate content 28$

2943 N. Castro 2500 very hard cemented sand and gravel with boulders SW comer Kelso & 14th Ave. 3266 multiple thin caps at surface, fractures minor

2444 N. Geronlmo 3125 multiple caps, mostly fine material NW comer Warren & Hampton 2762 one foot below cap, cemented sand and gravel NE comer Speedway & Campbell 970 hard, very fractured cap, many gneiss boulders to 12" dla.

West Plata, blocks west of tough not hard, small material, part Miracle Mile 3088 cap gone

SW comer Speedway & Queen Ave. 1071 near bottom of profile Across from 316 S. Main 1862 typical Cemetery Terrace caliche, joints filled

21st St. & Rubio 2702 cap hard, jointed, carbonate content 88$

SW comer 8th Ave. & 21st St. 1470 similar to 21st & Rubio, more coarse material

7th Ave. between 29th & 30th St. 2500 cemented sand and gravel

NW comer 32nd St. & Euclid 4675 very hard bouldery cap, no other profile exposed

1500 E. 36th St. 4800 very hard, much gravel, cap thick, only cap exposed

SW comer S. Park & 28th St. 3281 very hard cap in ditch 76

IV (continued)

Velocity Condition of Cap and Location ft./sec. Location Within Profile

Bottom Arroyo Chico at Campbell 21?0 lightly cemented sand and gravel, some boulders

141 N. Santa Rita 2500 1" cap part way, cemented sand and gravel below E. Terra Alta Blvd. ^ block east of Country Club 4444 1" cap exposed Intermittently

SW comer Poe & RoJen Ct. 1818 slightly cemented sand and gravel

SW comer Bently & Helen 2100 thin cap exposed Intermittently

NW comer 6th St. & Norris 1688 thin cap over cemented sand and gravel

Entrance to El Conquistador on Broadway 4166 fractured cap exposed at surface

NW comer Edison and Rita Ave. 4000 cap exposed, can pick up fractures on seismic profile

NE comer Sycamore & Bellvue 3888 cap exposed, partly removed

SW comer Irving & Holmes 1985 caps exposed, lower profile very soft

W side Rosemont at Julia 1333 thin cap partly exposed, much gravel 14th St. near Tuller School 4500 very hard cap exposed, can pick up fractures on seismic profile

E. side B u m s at Chantilly 4000 cap partly exposed

NW comer Speedway & Tucson Blvd. 2777 multiple caps, cap 30" below surface NW comer Kenyon & Langly 2500 cemented sand and gravel below cap, some cobbles, very tough to dig 77

D9 NO.9 RIPPER PERFORMANCE AS RE LATE 0 TO SEISMIC WAVE VELOCITIES V E LO C IT Y IN FEET PER SECOND X MOO 0 1 2 3 4 5 G 7 # 9 10 H 12 13 14 15 topsoil CLAY GLACIAL TILL IGNEOUS ROCKS granite basalt trap rock SEDIMENTARY ROCKS shale sandstone

si 11 s t o n e c I a y s t o n e conglomera te breccia c a I i c h n limestone MET AMORPHIC ROCKS schist quartzite gneiss slate MINERALS & ORES coal iron ore

rip p a b I e L marginal E non r i pp abIe Table V. Seismic velocities as related to rlppabllity of materials. (After Caterpillar Tractor Co., 1961) UNCONFINED COMPRESSIVE STRENGTH (p$l) Figure IX. Relation between carbonate content and content carbonate between Relation IX.Figure unconfined compressive strength of strength compressive unconfined aih. Fo le 1961) (From Glle, caliche. MOIST I DRY AIR E T A N O B R A C T N E C R E P DRY R I A • • r= O Y=2.1Q LOG LOG Y= Y= LOG 0 . 7 i

64+0. 317X .0 0 + 4 .6 0 U2X 2 .U 0 +

90 100

IT I HI 78 Figure X Figure INFILTRATION RATE (in/ht) Relation between carbonate content and content carbonate between Relation nitainrt. Fo le 1961) (From Glle. rate. Infiltration O Y . 009 X 0.0199 Y=8LOG 0.7 CARBONATE T N E C R E P 90 100

i Mill SELECTED BIBLIOGRAPHY

The term caliche was introduced into the literature in 1901 by Blake, but it was many years before it became generally accepted and used. Prior to that time, many papers were published that described caliche but referred to the material as travertine. Many authors have described caliche without giving the described material a specific name.

Most geologists considered caliche to be a problem for the soil scientists and overlooked or ignored the caliche in their reports. Consequently, most of the pub­ lished material on caliche is to be found in soil science journals, especially the reports of the U. S. Department of Agriculture Soil Survey Reports.

Papers on Pleistocene or Quaternary geology of an arid or semi-arid region often mention caliche. Fre­ quently soil reports of the same area discuss these

deposits as a zone of lime accumulation in the soil, rather than calling it caliche.

This bibliography is not a comprehensive review

of the literature on caliche, but it is representative

and indicates the more common sources of information.

80 81

Albritton, G. C., Jr., and Bryan, Kirk, 1939. Quaternary stratigraphy in the Davis Mountains, Trans-Pecos, Texas: Geol. Soc. Am. Bull., v. 50, p. 1423-1474.

American Association of Petroleum Geologists, 1945. Note on field conference to study caliche on the High Plains: Am. Assoc. Petrol. Geol. Bull., v. 29, no. 9, p. 1374.

American Geological Institute, i960. Glossary of geology and related sciences, second edition: Am. Geol. Inst., J. V. Howell Chairman, Williams and Heintz Lithograph Corp., Wash. D. C., p. 42.

Antevs, Ernst, 1955a > Geologic-climatic dating in the west: Am. Antiquity, v. 20, p. 317-335*

______, 1955b. Geologic-climatic method of dating in geochronology: Physical Science Bull. No. 2, Univ. Ariz. Bull. Series, v. 26, no. 2, Univ. Ariz. Press, Tucson.

Ariz. Agr. Expt. Sta., 1916, 27th annual report: p. 298.

Armstrong, C. A., and Yost, G. B., 1958, Geology and groundwater resources of the Palomas Plaln-Dendora Valley area, Maricopa and Yuma Counties, Arizona: Water Resources Report 4, Ariz. State Land Dept.

Babcock, H. M., and Cushing, E. M., 1952, Recharge to groundwater from floods in a typical desert wash, Pinal County: Ariz. Geol. Soc. Guidebook for field trip excursions in southern Ariz. p. 221. Reprinted from 1942 Trans. Am. Geophys. Union.

Back, William, 1961, Calcium Carbonate saturation in groundwater: U. S. Geol. Survey Water Supply Paper 1535. part D.

Barrell, J., 1908, Relation between climate and terrestrial deposits: Jour. Geol., v. 16, p. 159-384.

Bissell, H. J., 1963. Lake Bonneville: geology of southern Utah Valley, Utah: U. S. Geol. Survey Prof. Paper 257-B, P* 107.

Blake, W. P., 1901, The caliche of Arizona: an example of deposition by the vadose circulation: Am. Inst. Mine Engr. Trans., v. 31. P* 220-226. 82 Blank, H. R. and Tynes, E. W., 1965, Formation of caliche, in situ: Geol. Soc. Am. Bull., v. 73. p. 138?- 1392.

Brace, 0. L., 1931, Factors governing accumulation of oil and gas in Miranda and Pettus districts. Gulf Coastal Texas and their application to other areas: Am. Assoc. Petrol. Geol. Bull., v. 51. P» 762.

Bretz, J. H., and Horberg, Leland, 1949a, Caliche in southeastern New Mexico: Jour. Geol., v. 57, n. 5. P* 491.

______, 1949b, Ogallala Formation west of the Llano Estacado: Jour. Geol., v. 57, n. 5. P» 477-491.

Breazeale, J. F., and Smith, H. V., 1930, Caliche in Arizona: Ariz. Agr. Expt. Sta. Bull. 131.

Brown, C. N ., 1956, The origin of caliche on the north­ east Llano Estacado, Texas: Jour. Geol., v. 64, n. 1, p. 1—16.

Brown, V. J., and Runner, D. G., 1938, Engineering terminology: Gillette Pub. Co., Chicago.

Brown, W. H., 1939, Tucson Mountains, an Arizona Basin Range type: Geol. Soc. Am. Bull., v. 50, p. 697-760.

Bryan, F., 1938, A review of the geology of the Clovis finds reported by Howard and Cotter: Am. Antiquity, v. 4, p. 113-130.

Bryan, Kirk, 1923, Erosion and sedimentation in the Papago Country: U. S. Geol. Survey Bull. 730-B, p. 31.

______, 1925, The Papago Country, Arizona, geographic, geologic, and hydrologic reconnaissance: U. S. Geol. Survey Water Supply Paper 499, p. 370.

______, 1928, Historic evidence on changes in the channel of Rio Puerco, a tributary of the Rio Grande in New Mexico: Jour. Geol., v. 37, p. 265-282.

______, 1929, Solution faceted limestone pebbles: Am. Jour. Sci., v. 18, 5th ser., p. 193-209. 83 Buol, S. W ., 1964, Calcisols in Arizona: Progressive Agr. in Arlz., College of Agr., Univ. Ariz., v. 16, no. 6.

______, 1965, Present soil-forming factors and pro­ cesses in arid and semi-arid regions: Soil Sci., v. 99, p. 45-49.

______, and Yeslloy, M. S. A., 1964, A genesis study of a Mohave sandy loam profile: Soil Sci. Soc. Am. Proc., v. 28, p. 254-256.

Caterpillar Tractor Co., 1959, Ripping with seismic analysis: Caterpillar Tractor Co., Form 717- 33793., Peoria, 111.

______, 1961, Handbook of ripping: Form 728-33704-1, Caterpillar Tractor Co., Peoria, 111.

Cannon, W. A., 1913, Botannical features of the Algerian Sahara: Carnegie Inst. Was. Pub. 178.

Chao, Lance Lah-Sing, 1957, Some physical and chemical differences in soils of the Mohave and related series: Unpub. Univ. of Ariz. Master's thesis.

Church, H. K., 1964, Geophysical examination can make earthmoving a profitable science in the southwest: Southwest Builder and Contractor, Mar. 13, 1964.

Cooley, M. E., 1961, Description and origin of caliche in the Glen-San Juan Canyon region, Utah and Arizona: Ariz. Geol. Soc. Digest, v. 9*

Coulsen, B. 0., 1950, Geology of the Sweetwater Drive area and correlation of the Santa Cruz Valley gravels: Unpub. Univ. of Ariz. Master's thesis.

Cuyler, R. H., 1930, Caliche as a fault indicator: (abs.) Geol. Soc. Am. Bull., v. 41, n. 1, p. 109.

Davidson, W. C., 1925, Caliche and other native road materials: New Mexico Hwy. Jour., July, 1925.

Damon, P. E., Long, A., and Sigalove, J. J., 1963, Arizona radiocarbon dates IV: Radiocarbon, v. 5, P» 283- 301. Univ. Ariz. Geochronology Contribution No.60.

______, Haynes, C. V., and Long, A., 1964, Arizona radiocarbon dates V: Radiocarbon, v. 6, p. 91- 107. Univ. Ariz. Geochronology Contribution No.88. 84

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______, 1931» Soil survey of the Tucson area, Arizona: U. S* Dept. Agr. Soil Survey Series 1931. no. 19.

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Yesiloy, M. S. A., 1962, Characteristics and genesis of a Mohave sandy loam profile: Unpub. Univ. Ariz. Master's thesis. j yuui 03003 1184 I Map 1965 r

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