Origin of Meter-Size Granite Basins in the 

Southern Sierra Nevada, California

U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2008-5210
Cover—Rainwater pond in granite basin at Quail Flat site. Water is 110 cm in diameter and 20 cm 

deep; upper white rim is 148 cm in diameter.
Origin of Meter-Size Granite Basins in the 

Southern Sierra Nevada, California

Scientific Investigations Report 2008-5210

By James G. Moore, Mary A. Gorden, Joel E. Robinson, and Barry C. Moring

U.S. Department of the Interior

U.S. Geological Survey
ii

U.S. Department of the Interior

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2008

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Produced in the Western Region, Menlo Park, California

Manuscript approved for publication, October 29, 2008

Text edited by Peter Stauffer

Layout and Design by Jeanne S. DiLeo
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Previous Work ................................................................................................................................................3

Location, Vegetation, and Associated Features.......................................................................................3

Geology............................................................................................................................................................7

Volume of the Basins.....................................................................................................................................7

Size and Shape of the Basins ......................................................................................................................8

Age of the Basins...........................................................................................................................................9

Natural Versus Manmade Origin...............................................................................................................10

Excavation of the Basins ............................................................................................................................11

Uses of the Basins.......................................................................................................................................12

Conclusions...................................................................................................................................................13

Acknowledgments.......................................................................................................................................13

References....................................................................................................................................................14

Figures

 1. Examples of granite basins.............................................................................................................1 

 2. Granite basin sites and giant sequoia groves .............................................................................2

 3. Elevation distribution of 224 basin sites shown as cumulative percent .................................3

 4. Map of basin sites showing general restriction to elevation range of 1,700-2,300 m...........4 

 5. Proposed origins of granite basins as reported in publications spanning 130 years...........5 

 6. Numbers of basins and mortars per site for the entire belt of sites, plotted as 

cumulative percent ..........................................................................................................................5

 7. Distribution of aspect of basin sites, showing the direction that the topographic slope 

faces at each of 216 sites ...............................................................................................................5 

 8. Map of selected forest types in southern Sequoia and Kings Canyon National Parks 

(modified from National Park Service, 2007) ...............................................................................6 

 9. Plot of diameter versus depth of basin.........................................................................................7

 10. Average dimensions and trend lines of all of the basins in each of four sites.......................8

 11. North-south variation of basin dimensions ..................................................................................9 

 12. Dimensions of an experimental mortar compared with two groups of bedrock mortars, 

one at Round Meadow in Giant Forest (Stewart, 1929) and one at Nelson Cabin site at lat 

36°16’N.............................................................................................................................................11 
Blank page
Origin of Meter-Size Granite Basins in the Southern Sierra Nevada, California

By James G. Moore1, Mary A. Gorden2, Joel E. Robinson1, and Barry C. Moring1

Abstract

Meter-size granite basins are found in a 180-km belt 

extending south from the South Fork of the Kings River to 

Lake Isabella on the west slope of the southern Sierra Nevada, 

California. Their origin has long been debated. A total of 

1,033 basins have been inventoried at 221 sites. The basins 

occur on bedrock granitic outcrops at a median elevation of 

1,950 m. Median basin diameter among 30 of the basin sites 

varies from 89 to 170 cm, median depth is 12 to 63 cm. Eighty 

percent of the basin sites also contain smaller bedrock mortars 

(~1-2 liters in capacity) of the type used by Native Americans 

(American Indians) to grind acorns. Features that suggest a 

manmade origin for the basins are: restricted size, shape, and 

elevation range; common association with Indian middens 

and grinding mortars; a south- and west-facing aspect; presence of differing shapes in distinct localities; and location in 

a food-rich belt with pleasant summer weather. Volcanic ash 

(erupted A.D. 1240±60) in the bottom of several of the basins 

indicates that they were used shortly before ~760 years ago 

but not thereafter. Experiments suggest that campfires built on 

the granite will weaken the bedrock and expedite excavation 

of the basins. The primary use of the basins was apparently 

in preparing food, including acorns and pine nuts. The basins 

are among the largest and most permanent artifacts remaining 

from the California Indian civilization. 

Introduction

Numerous round, meter-size basins are found on the 

west slope of the southern Sierra Nevada. They are carved in 

granitic bedrock (fig. 1) and are abundant in a belt extending 

180 km south from the South Fork of the Kings River to a site 

Figure 1. Examples of granite basins. A, Nelson Cabin site; 

hammer is 30 cm long. Some rain water remains in bottom, and pine 

needles mark the high-water mark. B, Three rock basins at Alpine 

Creek site; that on right contains some water. Hammer is 30 cm long. 

C, Man near two granite basins. Three grinding mortars are visible in 

foreground at Methusula site near Balch Park (Dulitz, 2000).

A

B

C

1

U.S. Geological Survey, Menlo Park, California 94025 

2 Southern Sierra Archaeological Society, PO Box 44066, Lemoncove, 

California 93244 
2 Origin of Meter-Size Granite Basins in the Southern Sierra Nevada, California

W

Lindsey

Porterville

Woodlake

Independence

Cartago

Lone Pine

Middle Fork

East Fork

Kings River

South Fork

Lake Kaweah

Kaweah River

Tule

River

South Fork

Deer

Creek

South

Fork

Kern

River

Bear

Creek

Owens

River

Owens

Lake

Dry

Creek

South Fork

White River

Poso Creek

Isabella

Lake

Kern

River

Middle Fork

North Fork

0 5 10 15 20

36o N

36.5o N

119o W 118.5o W 118o W

Tahoe Glaciation

Sequoia Grove

Granite Basin

Kilometers

Explanation

Figure 2. Granite basin sites (gray circles) and giant sequoia groves (green triangles). Extent of the earliest and most extensive 

documented glaciation (Tahoe) is shown by blue color (after Moore and Mack, 2008). 
Location, Vegetation, and Associated Features 3

west of Lake Isabella (fig. 2). Most of the northern part of the 

belt is in Sequoia National Park, and much of the southern part 

is in the southern section of Giant Sequoia National Monument. These basins commonly occur in clusters or lineaments 

on bedrock outcrops and are concentrated near streams, mostly 

in the elevation range of 1,700–2,300 m (figs. 3, 4). They are 

clearly higher in elevation than the core Indian habitation areas 

in the lowlands (Elsasser, 1972). 

In the 1970’s Mary Gorden of the Southern Sierra 

Archaeological Society began an inventory of basin sites 

(Gorden, 2007), and nomenclature was standardized in 

collaboration with Louise Hastrup. The inventory has been 

supplemented more recently by data from the Southern Sierra 

Archaeological Society, the California Division of Forestry 

and Fire Protection (Sandelin, 2000), and investigators of the 

National Park Service and Sequoia National Forest. Much 

of the descriptions and conclusions in this report rely on the 

inventory, which contains data on 1,033 basins at 221 sites. In 

this report we analyze and summarize the data now available 

on the basins and propose what process produced them and for 

what purpose.

1,200

1,400

1,600

1,800

2,000

2,200

2,400

2,600

2,800

.1 1 5 10 20 30 50 70 80 90 95 99 99.9

Elevation, in Meters

Cumulative Percent of Sites

Median: 1,950 m

 (6,400 ft)

Previous Work

Local residents, foresters, sheepherders, cattlemen, hikers, 

and fishermen have long known of the basins. Early explorers 

and residents were unable to learn from the Native Americans 

then living about the history of the basins, how they were 

formed, and if they had a practical use (Stewart, 1929).

One of the earliest reports on the basins is that of Barton 

(1881; see fig. 5), who stated that “some ancient people have 

scalloped out holes in the rock, large enough, in some cases, 

to hold eight or ten barrels of water” (as quoted by Wallace, 

1993). Barton believed them to be man-made and commented 

that apparently “work had been done with a chisel” (as quoted 

by Stewart, 1929). 

 In a pioneering report based on 1925 fieldwork in 

Sequoia National Park, Stewart (1929) described 42 basins 

from 5 clusters near Park Headquarters in Giant Forest, and 

provided measurements of their size and descriptions of their 

excavated contents. The team that investigated the basins at 

that time included geologist François Matthes, known for his 

exhaustive study of the origin of Yosemite Valley (Matthes, 

1930). The team concluded that the basins were manmade. A 

letter from Matthes to C. Hart Merrium dated March 21, 1926, 

states, “I took pains to examine a number of basins of this type 

in different localities (Giant Forest, Redwood Meadows, etc.) 

with a special view to ascertaining whether by any chance they 

might be produced by natural processes, but am convinced 

that they are of artificial making” (Plotnicov and Elasser, 

1961). Matthes, shortly before his death in 1947, reportedly 

changed his opinion and opted for a natural origin for the 

basins (Plotnicov and Elsasser, 1961). This reversal in thought 

is partly responsible for the debate that has continued—

whether the basins are of natural or man-made origin (fig. 5). 

Three reports have attributed the origin of the basins to pits 

formed by weathering (Hall, 1930; Plotnicov and Elsasser, 

1961; Otter; 1979); two to potholes created by millstones 

in a subaerial or subglacial stream (Schutt, 1962; Barnes, 

1984); four to unspecified natural processes (Elsasser, 1972; 

Mundy, 1990; Foster and others, 1991; Dillon, 1992); six to an 

unknown origin (Pusateri, 1962; Weinberger, 1981; Wallace, 

1993; Dulitz, 2000; Sandelin, 2000; and Gorden, 2007); and 

four to a manmade origin (Barton, 1881; Stewart, 1929; Gehr 

and others, 1979; this study). Dillon (1992, p. 72) states, “With 

only one or two notable exceptions, the consensus of opinion 

amongst most Sierra Nevada archaeologists is that in every 

case the large hemispherical bedrock basins are of natural, 

not cultural, origin.” Several of those authors who support a 

natural origin also suggest that the Indians selected campsites 

that had natural basins, made use of them, and possibly 

modified them. 

Location, Vegetation, and Associated 

Features

Most of the inventoried basins occur in a belt or zone on 

the west slope of the southern Sierra extending south from 

the South Fork of the Kings river to a point west of Lake 

Isabella—from lat 37.4° to 35.75°N—a distance of 180 km 

(fig. 2). The basins at 221 sites in this zone are those considered in this report. Scattered basins are also reported north of 

the zone, including one site near Yosemite (Presnell, 1930). 

The median elevation of the mapped sites in the main belt is 

1,950 m (6,400 ft), and 80 percent of the sites tabulated occur 

between 1,700 and 2,200 meters (fig. 3). The width of the 

basin belt generally varies from a few kilometers to about 7 

km, but near its center at lat 36.02°N it broadens to a width 

Figure 3. Elevation distribution of 221 basin sites shown as 

cumulative percent. Median elevation is 1,950 m (6,400 ft).
4 Origin of Meter-Size Granite Basins in the Southern Sierra Nevada, California

General Grant

 Grove

119°W 118.25°W

36.5°N

36°N

Elevation, in Meters

3,000 - 3,600

2,300 - 3,000

1,700 - 2,300

1,100 - 1,700

500 - 1,100

0 - 500

Camp Nelson

Balch Park

Giant Forest Kilometers

0 5 10

Figure 4. Map of basin sites (gray circles) showing general restriction to elevation range of 1,700-2,300 m. Rectangle is 

area of figure 8, and boundary of Sequoia and Kings Canyon National Parks is shown (irregular white line).
Location, Vegetation, and Associated Features 5

of 30 km, partly in the relatively flat country where the Little 

Kern and Kern Rivers join (figs. 2, 4). 

Generally the basins occur in groups of 2-4, but their 

numbers range from 1 to 31 at a single site. The most 

crowded sites (10 percent of all sites) contain more than 11 

individual basins (fig.6). Typical bedrock mortars of the type 

used by Native Americans to grind acorns are commonly 

associated with the basins (fig. 1C). Of 221 basin sites, 176 

(80 percent) also have mortars on the same bedrock outcrop. 

Where both occur at the same site, in most cases there are 

more mortars than basins (fig. 6). 

The topographic information employed for elevation 

data in the map region (fig. 2) is the U.S. Geological Survey 

National Elevation Dataset gridded at 30-m spacing. Using 

1880 1900 1920 1940 1960 1980 2000 2020 Natural

Undecided

Pothole

Weathering

 Pit

Manmade

Pusateri

Weinberger

Wallace

Dulitz

Gorden

Schutt

Barnes

Matthes

Elsasser

Plotnicov

 Elsasser

Hall

Otter

 This

Study Barton Stewart Gehr

Mundy

Foster

Dillon

Sandelin

Figure 5. Proposed origins of 

granite basins as reported in 

publications spanning 130 years. 

0

10

20

30

40

50

60

70

.1 30 50 70 80 90 95 99

Mortars

Basins

99.9

Number Per Site

Cumulative Percent

1 5 10 20

Figure 6. Numbers of basins and mortars per site for the entire 

belt of sites, plotted as cumulative percent. The median number of 

basins per site is about 3, and the median number of mortars about 

9. The ratio of mortars to basins per site is variable, but the median 

ratio is about 3 to 1. 

these data, we calculated the aspect of each basin site (the 

direction that the 30-meter-size slope containing the site 

faces). The result of this determination is that the most common aspect for the basin sites is toward the south and west 

(fig. 7). Of a total of 216 basin sites, 9 percent face within 40° 

of north (from 320° to 40° azimuth) and 39 percent face within 

40° of south (from 140° to 220°). We believe that the most reasonable explanation for this preferred aspect is that the Native 

Americans chose their campsites (with rock basins) in areas 

of sunny exposure. Because of snow cover and other weather 

patterns, such locations could be occupied earlier in the spring 

and later in the fall.

The elevation belt of the basin sites is similar to that of 

the giant sequoia (Sequoiadendron giganteum) groves (fig. 2). 

It also contains most of the desirable campgrounds and cabins 

that residents of the San Joaquin Valley use to avoid the summer heat. These include Grant Grove, Giant Forest, Mineral 

0

10

20

30

40

50

0 60 120

Facing direction of basin sites

n = 216

180 240 300 360

Number of Sites

Aspect, in Degrees

N E S W N

Figure 7. Distribution of aspect of basin sites, showing the 

direction that the topographic slope faces at each of 216 sites. 

South and west exposures predominate over north and east. 
6 Origin of Meter-Size Granite Basins in the Southern Sierra Nevada, California

King, Mountain Home, Balch Park, Camp Wishon, Camp Nelson, and Johnsondale. The monthly means of the maximum 

daily temperatures for Porterville in the San Joaquin Valley 

are: June, 34°C; July, 37°C; August, 36°C; and September, 

33°C. The monthly means of the maximum daily temperatures for Giant Forest in the basin belt are: June, 22°C; July, 

26°C; August, 26°C; and September, 22°C. This 10°C+ difference in mean maximum temperature inspires a migration 

118.75° W 118.5° W

36.75°N

36.5°N

Forest Types

California black oak 

Giant sequoia 

Jeffrey pine 

Sugar pine

Sequoia-Kings Canyon

National Parks

0 5

Kilometers

to the mountains in the spring and summer after melting of 

the heavy winter snow. 

Generally, the axis of the belt of basin sites is remarkably close to that of the Sequoia groves. However, in the 

north, the basin belt south of the South Fork of Kings River 

occurs west of numerous groves. On the other hand, numerous basins occur east of groves in the lower Little Kern River 

area. The basins also extend an additional 14 km south of the 

Figure 8. Map 

of selected forest 

types in southern 

Sequoia and 

Kings Canyon 

National Parks 

(modified from 

National Park 

Service, 2007). 

“California black 

oak” includes 

two forest types, 

each including 

black oak; “giant 

sequoia” includes 

three forest types 

including giant 

sequoia, one 

of which also 

includes sugar 

pine; “Jeffrey 

pine” includes 

six forest types 

containing Jeffrey 

pine; “sugar 

pine” includes 

two forest types 

containing 

sugar pine. Gray 

circles are basin 

sites. Area of 

map shown by 

rectangle in 

figure 4.
Volume of the Basins 7

southernmost grove (Deer Creek Grove at lat 35.88°N) and 

end at lat 35.75°N. 

Detailed vegetation mapping in Sequoia and Kings 

Canyon National Parks (National Park Service, 2007) provides 

a basis to compare location of the basins with distribution of 

forest types (fig. 8). This area has the advantage that it has 

undergone no logging since creation of the parks in 1890. In 

addition to the giant sequoia, the belt of basins is associated 

with white fir (Abies concolor), red fir (Abies magnifica), 

incense cedar (Calocedrus decurrens), Jeffrey pine (Pinus 

jeffreyi), ponderosa pine (Pinus ponderosa), sugar pine (Pinus 

lamberiana), and California black oak (Quercus kellogii). 

The tree species in this area that produce edible pine nuts, a 

valuable food source to the Indians, are primarily the sugar 

pine and also the Jeffrey pine and ponderosa pine. Forests 

containing these pines are closely associated with the basin 

belt, especially the sugar pine (fig. 8), which is the largest of 

the pines and has the longest cone of any conifer, 25-50 cm in 

length. The black oak, which provides the acorns most prized 

by the Indians, occurs up to the belt elevation (fig. 8). Acorns 

were no doubt processed in the mortars. The proximity of the 

large-cone pine nut trees to the basin sites, and the fact that 

basins are absent in all the other regions of California where 

oak trees and mortars are common, suggests that the basins 

were used in pine-nut processing.

Geology

Generally the north part of the basin belt is close to, but 

slightly west of the mapped western limit of the Tahoe stage 

glaciation in the Sierra (fig. 2). This glaciation is the earliest (and most extensive) that has been mapped on the west 

slope of the southern Sierra (Moore and Mack, 2008). In two 

small areas the basins are near the lower courses of major 

trunk glaciers that extended to relatively low elevation. Some 

basin sites are near the terminus of the glacier occupying the 

canyon of the Marble Fork of the Kaweah River. Also, several 

basin sites occur at the north margin of the glacier occupying 

the canyon of the East Fork of the Kaweah River. However, 

the great majority of the basin sites are unassociated with the 

areas of glaciation. The area of glaciation extended south to 

about lat 36.25°N, but, significantly, the belt of basins extends 

an additional 57 km south. 

The basins are excavated entirely in medium- to coarsegrained granitic rock, granodiorite and granite in the classification of Streckheisen (1973). No basins are reported 

in metamorphic rocks, a rock type in which river potholes 

are common. Most of the basins in the northern third of the 

belt, north of Giant Forest at lat 36.55°N, are carved in the 

Giant Forest Granodiorite, a rather dark granodiorite that 

contains about 17 volume percent dark minerals (hornblende 

and biotite), has a SiO2

 content of 60-66 weight percent, and 

was emplaced 102–97 million years ago (Moore and Sisson, 

1987; Sisson and Moore, 1994). However, a few basins in 

the extreme north (Princess Campground, Pennys Pride, and 

Azalia Campground) occur in a much lighter colored rock, the 

granite of Grant Grove, which contains only 5 percent dark 

minerals, has a SiO2

 content of 71-76 weight percent, and was 

emplaced in the interval 128–106 million years ago (Moore 

and Nokleberg, 1992). No difference in character is noticed in 

the basins hollowed out of these two somewhat different rock 

types. The Case Mountain area (lat 36.4°N) has basins in the 

granodiorite of Case Mountain, a coarse-grained granodiorite 

with 1–9 volume percent dark minerals and SiO2 content of 

69-73 weight percent. 

The rocks hosting basins south of Giant Forest in the 

southern half of the basin belt are not as well known, because 

detailed published geologic mapping is not available. Several 

of the basins in the region near the southeastern corner of the 

Mineral King 15-minute quadrangle (lat 36.2°N) are carved 

in the porphyritic biotite granodiorite of Castle Rock, which 

contains ~12 volume percent dark minerals (D. C. Ross, U. 

S. Geological Survey, written commun., 1988). This rock is 

characterized by scattered large crystals of potassium feldspar 

1-4 cm in size.

Volume of the Basins

Most of the basins closely approach a round shape in 

plan, and oval ones are not common. The basins range in 

volume from 40 to 1,400 liters. A distinct gap exists between 

the volume of the basins and that of the associated bedrock 

mortars, the larger of which are about 1-2 liters in volume. 

0

20

40

60

80

100

0 40 80 120 160 200

Giant Forest

(Stewart, 1929)

Depth, in Centimeters

Diameter, in Centimeters

Depth = radius

10 L

50 L

100 L

250 L

500 L

1,000 L

Depth = 1/2 radius

Depth = 1/4 radius

Figure 9. Plot of diameter versus depth of basins. Lines of equal 

basin volume (blue lines) are based on the assumption that the 

basins are the shape of a spherical segment (volume = 1/6  h 

[3a2+ h2], where a is the radius and h the depth). The volumes of 

Giant Forest basins range from about 45 to 600 liters. Red lines 

show selected diameter-to-depth ratios.
8 Origin of Meter-Size Granite Basins in the Southern Sierra Nevada, California

Some of the basins attain a depth that is equal to their radius, 

and hence they approximate a hemisphere in shape. However, 

such deep basins are not common, and most have a depth 

ranging from one-eighth to one-half of the radius. A good 

approximation of the shape of the basins is a segment of a 

sphere, that is, the part of a sphere cut off by a plane. A few 

basins may be either flatter or more pointed on the bottom 

than is a spherical segment, but generally this shape provides a 

good approximation of the volume of the basins (fig. 9). Such 

a segment has a volume equal to 1/6  h (3a2 + h2), where a is 

the radius and h is the depth of the spherical segment representing the granite basin. In this way, the volume of the basins 

can be approximated by reference to their diameter and depth. 

The largest basin has a volume about 1,400 liters, the median 

maximum volume of basins at the 30 sites with more than five 

basins each is about 300 liters, and the overall median volume 

is about 130 liters. 

Size and Shape of the Basins

The diameter and depth of basins are variable at sites 

with multiple basins, as well as between the separate sites 

within the main 180-km-long belt of sites. Within each of 30 

groups of basins at which five or more basins occur, the diameter-depth plots commonly show a range of 50 cm or more 

in diameter and as much as 40 cm in depth, but these plots 

0

20

40

60

80

100

0 40 80 120 160 200

Sunset Point Rock basins

Shake Flat

Halstead Creek

Quail Flat

Depth, in Centimeters

Average Diameter, in Centimeters

Mortars

Figure 10. Average dimensions (diameter and depth) and trend 

lines of all of the basins in each of four sites. The Halstead Creek 

and Quail Flat sites are considerably north of the Sunset Point and 

Shake Flat sites. All trend lines (least squares) project to about 50 

cm diameter at zero depth, suggesting that the basins began their 

growth at that diameter. The depth, when projected to a diameter 

of 125 cm, is about 25 cm for shallow northern sites and 50 cm for 

deep southern sites. A major gap occurs between the dimensions 

of mortars (navy blue bar) and the much larger basins.

usually define a distinct trend line, such that the larger basins 

are closer in shape to a hemisphere than the smaller basins, 

which are flatter—less deep in proportion to their diameter 

(fig. 10). This relationship seems to hold for all of the sites. 

It may result because the smaller, shallower basins at each 

site are those in an early stage of construction. If the trends 

are projected back to zero depth on the plots, the resulting 

diameter is about 50 cm. In the Mountain Home State Forest 

area, Dulitz (2000) has shown that the smallest basins have 

a diameter of about 55 cm. He concludes this indicates, “the 

basins start development with a diameter of about this size and 

are not formed by the enlargement of a small diameter hole.” 

The diameter-depth plots show a general tendency for northern 

sites to be shallower than southern sites (fig. 10). 

A few incipient basins have been noted in several of the 

basin clusters. These appear to be basins in the early stage of 

construction, which have a normal diameter but are extremely 

shallow. Stewart (1929) describes a feature in the Giant Forest 

region that is 65 x 95 cm in horizontal dimensions but has 

negligible depth and only a faint, slightly etched outline. 

No basins are known that display a prominent bump in 

the center; such bumps are common in potholes formed by 

stream action. They form where cobbles rotate and erode 

around the circumference of the growing depression and leave 

a vertical protuberance standing in the middle.

When all of the 30 sites for which there are several measured basins at each site are compared, the median diameter 

among the sites ranges from 89 to 170 cm and the median 

depth among the sites ranges from 12 to 63 cm (fig. 11A). The 

overall median diameter and depth are 125 cm and 25 cm, 

respectively. A trend of increasing size northward is distinct, 

and one of decreasing depth northward is less distinct.

The relation of depth to diameter is characteristic of 

individual areas and changes systematically from one geographical area to another. One measure of the ratio of depth 

to diameter for each group of basins is the projected depth 

where the diameter equals the overall median of 125 cm. This 

projected depth, determined by a best fitting least squares line, 

ranges from 7 to 60 cm (fig. 11B). 

The typical shape of the basins varies geographically in the southern Sierra. For example, two basins near lat 

36.2°N average about 50 cm in depth at 125-cm diameter, 

whereas two near lat 36.6°N (44 km to the north) average 

about 25 cm in depth at that diameter (fig. 10). On this basis, 

the region can be divided north to south into three districts: 

north, lat 37.4°–36.5°N (north of Middle Fork of Kaweah 

River); middle, lat 36.5°–36°N (between Middle Fork of 

Kaweah River and South Fork of the Middle Fork of the Tule 

River); and south, lat 36°–35.7°N (south of the South Fork of 

the Middle Fork of the Tule River). Distinct differences are 

evident when the characteristics of basins are examined for 

each district. The median dimensions of basins in the north 

district tend to be greatest in diameter and shallowest, those 

in the middle district are medium in diameter and deepest, 

and those in the south district are smallest in diameter and 

medium in depth (fig. 11A). 
Age of the Basins 9

Figure 11. North-south variation of basin dimensions. Arrows 

separate three latitude-defined districts of basin sites with 

different basin shapes. North district is north of the Middle Fork 

of the Kaweah River and south district is south of the South Fork 

of the Middle Fork of the Tule River. The middle district is between 

the north and south districts. A, Latitude of 30 basin sites with 

median diameter and median depth of basins at each site. B, 

Latitude of 30 basin sites with depth (normalized to a diameter of 

125 cm) and maximum volume of basins at each site.

37.5

37.0

36.5

36.0

35.5

37.5

37.0

36.5

36.0

35.5

0 50 100 150 200

Diameter

Depth

Degrees North Latitude

Median Dimension, in Centimeters

North

Middle

South

North

Middle

South

A

1 10 100 1,000 104

Depth (cm)

Volume (liters)

Dimensions

B

Similarly, with the depth normalized to a diameter of 125 

cm, the north district contains the shallowest basins, while the 

middle and south districts contain basins that are deeper, with 

those of the middle district being slightly deeper yet (fig. 11B). 

Basins in the middle district tend to have a greater maximum 

volume than those north and south, because of their greater 

depth (fig. 11B). 

These differences are difficult to explain by natural 

causes and suggest that the basins are manmade, with the differences resulting from the culture of the tribelets that made them. 

Since basins of the middle district are the deepest and most 

voluminous, we infer that they were the first to be made and 

underwent construction and refinement for the longest period. 

Age of the Basins

A few constraints can provide some information on the 

age of the basins. They must postdate the settlement period if 

they were indeed made by Native Americans. Archaeological 

investigation in the Mountain Home State Forest uncovered 

cultural material similar to that in use during the Late Prehistoric Period in the southern Sierra Nevada (Dillon, 1992; 

Wallace, 1993). This material included pottery, steatite vessels 

and beads, triangular arrowheads, and mortars using cobble 

pestles. This phase of Native American history is believed to 

have begun around A.D. 1200–1300 (Moratto, 1984). However, other artifacts in this area apparently reach back into the 

Archaic Period, perhaps as early as 2500-2000 B.C.; a single 

radiocarbon age at the Sunset Point site indicates an age of 

6000 B.C. (Dillon, 1992). 

In general, the basins look older and more weather-beaten 

than the mortars. The basins commonly truncate exfoliated 

shells of granite 10 cm or so thick (fig. 1). At one site a large 

boulder of vein quartz was apparently washed up onto the rock 

outcrop by the rise of a nearby creek. This boulder has since 

disintegrated into a pile of angular fragments averaging 5-10 

cm in size that has partly migrated into one of the basins filled 

with forest litter. Clearly this basin has not been used for a 

considerable time. 

Excavation of undisturbed basins in the Giant Forest area 

in 1925 revealed a basal white layer identified as rhyolitic 

volcanic ash (Stewart, 1929; Wood, 1977). Subsequent examination at numerous sites on the west slope of the Sierra in 

meadowland soils led to the identification of two volcanic ash 

layers that originated from explosive eruptions in the Mono 

Lake area northeast of the basin belt. The older ash erupted 

between A.D. 680 and 940 from Panum Crater, in the Mono 

Craters, and the younger ash erupted between A.D. 1180 

and 1300 (dated at A.D. 1240±60) from the Deadman Creek 

Domes area (Wood, 1977). 

The older ash is limited to regions north of Sequoia 

National Park, but the younger one occurs over much of that 

Park (Wood, 1977) and has been identified in sinkholes in the 

Redwood Canyon region of the Park (Tinsley, 1982), located 

16 km northwest of the Giant Forest area. Consequently, this 

younger ash is considered to correlate with that found in the 

Giant Forest basins, indicating that these basins were formed 

before A.D. 1240±60. It should be noted, however, that the 

ash has not been resampled or recovered from any basins since 

the original work of Stewart (1929). Because that ash lay on 

bedrock at the very bottom of the basins with no forest litter 

below it, yet was covered by forest debris when they were 

excavated in 1925, the basins were evidently in use when the 

ash was deposited. They had not been used since, however, 

because such use would have removed the ash (Stewart, 1929). 

The original construction of the basins may have been very 
10 Origin of Meter-Size Granite Basins in the Southern Sierra Nevada, California

early, but they were in use at A.D. 1240±60, nearly 800 years 

ago and were abandoned at that time or shortly thereafter. A 

possible reason for their abandonment was the environmental 

disturbance caused by the ashfall (Stewart, 1929).

Natural Versus Manmade Origin

Some workers have called on natural processes to 

produce the basins. In the forefront of these explanations 

is the role of running water forming bedrock potholes, 

where turbulent water rotates loose rocks in streambed 

irregularities, thereby grinding cylindrical holes in bedrock. 

A variant of this model, which can account for the presence 

of basins distant from a steam course, is the notion that water 

flowing beneath a glacier or at the edge of a glacier can 

activate rotating stones that mill the basins (Turner, 1892; 

Gilbert, 1906; Barnes, 1984; Schutt, 1962).

Another class of natural processes produces 

weathering pits, particularly where an existing depression 

traps rainwater. Wetting and drying (perhaps abetted by 

organically derived acids) and freezing and thawing can 

over time attack and disaggregate rock. Fragmental material 

is then removed from the deepening cavity by wind gusts, 

permitting the depression to accumulate more water 

(Stewart, 1929). This process generally produces shallow 

irregular depressions and is best suited to horizontal, not 

domical, bedrock exposures. A related process calls on 

granite disintegrating beneath a layer of overlying sand or 

soil that undergoes cycles of wetting and drying, causing 

the underlying bedrock to be attacked in favorable places 

(Twidale, 1982).

Many of the proposals for a natural origin add the 

condition that Native Americans took advantage of existing 

natural depressions made by one of the above processes and 

enlarged and deepened them to serve their own purpose.

The basins commonly occur near the top of domical 

outcrops, a site unlikely for streambed potholes. The 

restricted size of the basins, their near circularity, and their 

separation from their neighbors make them unlike river 

potholes, which commonly range greatly in size and shape 

and are intergrown with one another. Some potholes are deep 

and cylindrical in shape, with depth greater than diameter, 

and some are cylindrical and inclined with overhanging walls 

(Turner, 1892). Such features almost never are seen in the 

basins, which approach a shallow spherical segment in shape. 

Potholes commonly have a central basal protuberance. This 

feature, formed by boulders rotating by stream action in the 

bottom of the growing pothole, does not occur in the basins. 

The basins are generally larger than 55 cm in diameter 

and apparently start development with a large diameter 

(fig. 10). None occur in the size range between the smallest 

basins, with a diameter of about 40 cm, and the largest 

mortars, with a diameter of about 22 cm (fig. 10). The basins, 

therefore, are not formed by the enlargement of a smalldiameter hole, as would be the case for river potholes. 

Most of the basins are west of the terrain covered by ice 

in the last glacial periods, although a few are near the western 

margin of the ice. More than half of the basin belt is south of 

the apparent ice limit (fig. 2), thereby demonstrating that they 

are not features formed by stream flow beneath or marginal to 

glacial ice. 

The basins do not show the irregular outlines of weathering pits, and they are not restricted to the horizontal or 

depressed part of an outcrop where water would naturally 

pond. In fact, some basins occur on the flank of a domical 

outcrop and have the uphill side distinctly higher than the 

downhill side. They do not show the overhanging lips or localized control by joints and fractures (Migon, 2006) common in 

weathering pits. They are, however, all capable of holding a 

considerable volume of liquid.

We believe that the preponderance of evidence indicates 

that the basins are manmade. The regional restriction of the 

basin belt to a narrow elevation range near nut-producing 

pines and at the upper limit of acorn-producing oaks argues 

for the desirability of this zone for summer harvesting camps 

(figs. 2, 4, 8). Other evidence concerns the basin shape, size, 

and associated features. 

The basin sites are restricted to an elevation belt of 

1,700-2,200 m, with a median of 1,950 m (6,400 ft). This 

forested belt includes the most pleasant elevation for summer 

camping and contains an important nut-bearing tree, the sugar 

pine (fig. 6). It also lies adjacent to, but slightly higher than, 

black oak forests, which provide the most desirable acorns for 

food purposes. The predominant location of basin sites is on 

the southern and western slopes, sunny locations that can be 

occupied first after spring snowmelt and latest before fall rains 

and cool temperatures.

A few extremely shallow basins of normal diameter show 

only a faintly scored but quite circular outline. These appear to 

be incipient basins in the earliest stage of manual formation. 

Other basins show a slick inner surface, apparently smoothed 

by hand. 

Three general categories of basin shape can be differentiated (fig. 11). Generally these groups are geographically separated within the overall basin belt. This grouping suggests that 

some intelligence established the basin shape in a given area, 

possibly the differing traditions of separate tribal groups.

At eighty percent of the basin sites, typical bedrock mortars, undoubtedly of Native American origin, occur together 

on the same outcrop. Generally, more mortars occur per site 

than basins, with an overall ratio of 3 to 1 (fig. 6). Archaeological excavations near several of the basin sites have revealed 

middens containing artifacts that indicate a camp of some size 

was maintained at the site for a considerable length of time 

(Wallace, 1993; Dulitz, 2000). Obsidian chips are commonly 

found scattered in and near the basins. 

Several groups or triblets of Native Americans lived in 

the general region of the basin belt. The Yokuts occupied 

the low Sierra foothills and San Joaquin Valley on the west, 

and the Owens Valley Paiutes occupied the region east of the 

Sierra. In between, on the west slope of the Sierra, lived the 
Excavation of the Basins 11

Figure 12. Dimensions of an experimental mortar compared with 

two groups of bedrock mortars, one at Round Meadow in Giant 

Forest (Stewart, 1929) and one at Nelson Cabin site at lat 36°16’N. 

Diameter as measured at the top of the mortar holes is larger than 

the main shaft. Five and eight hours of continuous pestle pounding 

produced the experimental mortar (Osborn, 1998). 

0

5

10

15

20

25

0 5 10 15 20 25

Rock mortars

Round Meadow

Nelson Cabin

Depth, in Centimeters

Diameter at Top, in Centimeters

X8

X5

X Experimental (hours)

Monachi (Western Mono) in the north and the Tubatulabal in 

the south. These last two tribelets bordered one another near 

the course of the Middle Fork of the Kaweah River (Kroeber, 

1925; Elsasser, 1972). The most marked difference between 

the three basin districts occurs between the middle and north 

districts (fig. 11), which also meet near the Middle Fork of 

the Kaweah River (lat 36.5°N). We suggest, therefore, that the 

different tribelets (or their predecessors) who made the granite 

basins controlled the differences in their shape. The most 

refined basins, those that are smallest and deepest, occur in 

that district occupied by the Tubatulabal tribelet at the time of 

European contact. Both triblets spoke Shoshonean languages, 

but the differences in vocabulary led Kroeber (1925) to believe 

that the Tubatulabal had a longer separate history and had 

resided in their area adjacent to the Kern River several times 

longer than their Monachi neighbors to the north. Perhaps 

significantly, the name Tubatulabal is a Shoshonean word 

meaning “pine nut eaters” (Kroeber, 1925).

Excavation of the Basins

Considering that the granite basins are manmade, one 

would assume that they were hollowed out in the same fashion 

as were the neighboring bedrock mortars—by pounding, pecking, and grinding with a pestle stone. However, studies have 

shown that this method of boring a hole in granite is extremely 

laborious and slow. Careful experiments with continuous 

pounding (42,000 strikes) for five hours with a hard stone 

produced a hole 11 cm in diameter and 2 cm deep. Continued pounding (67,200 strikes) for a total of 8 hours enlarged 

the hole to a depth of 3.5 cm and a total volume of 140 mL 

(Osborne, 1998; fig. 11). This pounding at a quarrying rate 

of 17.5 mL/hr was so bone-jarring that one individual could 

continue only for about one hour at a time. The final hole was 

considerably shallower than the typical acorn mortars, which 

are about 15 cm deep (fig. 12) with a volume of about a liter 

(McCarthy and others, 1985). Work to create a typical mortar 

would, therefore, take seven 8-hour days of continuous pounding of stone on stone. (A longer time would be required if the 

mortar contained acorn meal.) Because the median volume of 

the maximum-sized basins at the 30 sites reported here (fig. 

11B) is 300 liters, the excavation of such a basin at this rate 

would take about five years of continuous work. Moreover, 

living at the basin sites is only possible for half of the year 

because of snow cover. Hence, an enormous, decade-long 

effort would be required to make each basin, if the traditional 

pounding and grinding method used to quarry the mortars 

were employed. 

Heating the rock will expedite excavation of the 

basins (Stewart, 1929). The effect of fire in cracking, weakening, and spalling rock is well known. Forest fires are implicated in degrading native art by spalling off sheets of decorated rock (Johnson, 2004); bedrock is spalled from the ceiling 

and walls of tunnels from the heat generated by burning 

vehicles (Larsen, 2006); and mining and quarrying operations 

commonly make use of fire to fracture rock (Gage and Gage, 

2005). Stone buildings subjected to fire may fail because of 

degradation and loss of strength of the stone, and the heated 

stone is commonly unsatisfactory for rebuilding because of its 

reduced strength.

Heating experiments conducted on building stones show 

that coarse-grained rocks are less resistant to heating than finegrained rocks and that granite is less resistant to heating than 

limestone and sandstone. Tar (1915) prepared cubes of several 

types of granitic rock, 2 inches on a side, and heated them 

in a furnace to known temperatures. The principal minerals 

in the rocks were quartz and feldspar, and to a lesser degree, 

biotitic, and hornblende. After quenching in either air or water, 

all of the heated rocks were tested for crushing strength. The 

unheated granites ranged in crushing strength from 25,100

to 34,960 pounds per square inch (1,770–2,460 kg/cm2). The 

average of the granitic rock samples showed a loss of 29 percent in strength after heating to 500°C and a loss of 63 percent 

in strength after heating to 750°C (Tarr, 1915). Little difference was noted in strength loss between the air-quenched and 

water-quenched samples. 

Microscopic examination of the heated samples showed 

that they were minutely cracked. The extensive cracks, which 

passed around most mineral grains and across the larger 

grains, tended to disaggregate the rock and induce its reduction in strength. The cracking was apparently caused by 

internal stresses set up by the differing thermal expansion of 

mineral grains (Tarr, 1915). The thermal expansion of quartz is 

twice that of feldspar.
12 Origin of Meter-Size Granite Basins in the Southern Sierra Nevada, California

We have heated hand samples of granodiorite in a 

box furnace to 500°C and 700°C for half an hour and then 

air-cooled the specimens. When cooled samples were struck 

sharply with a geologist’s 24-oz (0.7 kg) hammer, they shattered into several fragments, a behavior quite unlike untreated 

samples, which are much more difficult to break. When the 

fragments were forcefully rubbed together, they shed a sandy, 

grus-like material.

In another experiment, glowing charcoal briquettes 

were heaped on a large slab of fresh Carson Pass porphyritic 

granodiorite 1.37 m long, 1.04 m wide, and 18-30 cm thick. 

After several hours of heating, pounding with a stone pestle 

excavated a shallow basin. At this point the depression was 14 

cm in diameter and about 1 cm deep and held 60 mL of water 

before overflowing. A second period of heating used 3.2 kg of 

glowing charcoal that was replenished twice to heat the same 

depression for 3.5 hours. A thermister probe was inserted 

beneath the charcoal atop the rock. Temperature measurements indicated that the base of the coals was over 200°C for 

the entire period, was above 300°C for more than 2 hours, and 

attained a maximum temperature of 550°C. After 20 minutes 

of pounding with a granite pestle, the volume of the depression was increased to 95 mL. Hence excavation was at the rate 

of 107 mL/hr, six times faster than Osborne’s (1998) rate with 

unheated rock of 17.5 mL/hr. 

From this information we conclude that the granite basins 

could have been more easily quarried if a hot fire was built on 

the outcrop and within the basins, in order to minutely crack 

and weaken the underlying stone. A campfire can attain temperatures comparable to those employed in the experiments. 

Aluminum cans (melting point of 660°C) melt in a hot campfire. Iron can be heated to a red glow in the hottest core of a fire, 

indicating a temperature of ~700°C. However, even after several 

hours of heating, high temperatures would affect only about 1 

cm of the rock because of its insulating properties. After heating 

the rock, the time needed to produce a basin by the traditional 

pounding and grinding would be greatly reduced, but of course 

time and energy would be required to maintain a fire and heat 

the rock. The fire could burn at night and the pounding done in 

the daytime. In any event, sustained labor over a long period 

would still be required to hollow the basins. 

After a basin was made, containment of the fire would be 

easier and the heat more concentrated. The size of the basins 

is comparable to that of a campfire that could produce a good 

bed of coals without constant attention. If, indeed, the basin 

was used periodically to contain a fire, as would be needed for 

heating cooking stones, burning pitch off pine cones, roasting 

meat, or perhaps for ceremonial purposes, then the heating 

from each fire would hasten the disintegration of the granite 

and accommodate the subsequent deepening of the basin. 

Uses of the Basins

Many uses have been suggested for the basins, including 

water or steam bathing, tanning of hides, storage of food and 

water, and food preparation. The common juxtaposition of the 

basins with mortars strongly suggests that their chief purpose 

was in food preparation, because the primary use of the mortars for grinding acorns is well established. Preparing enough 

food to last through the winter was essential for survival. 

The black oak ranges higher in elevation than other oaks 

and is commonly found at 1,200-1,800 m in the lower reaches 

of the basin belt. Its acorns were among the most desirable 

types of oak acorns because their low tannin content required 

less leaching. The acorns were first shelled. For green acorns, 

the women commonly did this directly with their teeth. If dry, 

acorns were cracked in a shallow mortar by a single blow with 

a stone (Gayton, 1948). On other occasions, dry acorns were 

soaked in a waterproof basket to soften the tough shells to prepare them for easy opening by the teeth. The kernels were next 

removed from the shell and dried and the nutmeats ground 

in mortars to produce a fine meal to expedite leaching. The 

meal was then mixed with water and the batter was placed in a 

reservoir in which fresh water was added to remove the tannic 

acid and render the batter edible. In some cases hot water was 

poured over the meal. The reservoir commonly pictured is a 

depression in sand, which is about a meter in size, close in 

size to the rock basins (Morrato, 1984, his figure 1.1). Water 

was changed or added in the basin several times until bitterness disappeared from the meal. After leaching, the meal was 

removed from the basin taking care to prevent mixing with 

the sand. It was spread out in the sun to dry for later use, or 

cooked to a mush in a waterproof basket by adding hot stones, 

or baked into cakes. An early resident of the Springville area 

reported the use of a rock basin for hot-stone cooking of acorn 

mush (Wallace, 1993). 

The basins could be used during the three processes of 

acorn preparation—soaking, leaching, and cooking. They 

could serve the same purpose as the waterproof baskets used 

by Native Americans for containment of water and other liquids, and for cooking, without the problems of leakage, wear, 

and burning. The leaching process would be conveniently 

close to the mortar grinding activity. Because of their great 

volume, they would require fewer changes of the leaching 

water and could make use of water warmed by the sun for 

more efficient leaching. They would have the distinct advantage during leaching of keeping the meal free of sand. The 

meal could then be removed from the basins with a basket 

strainer. After leaching the meal could be hot-stone boiled in a 

basin to produce mush or baked wok-fashion on the side of a 

basin to produce cakes. A fire maintained in one of the basins 

would facilitate the heating of cooking stones and baking of 

acorn cakes. Watertight baskets would be needed to carry 

water to the basins from a nearby stream, except when they 

were filled by rainwater. Water could be continually added to 

the basins, always using the freshest water for the final leach. 

Indians harvested pine nuts in the autumn from sugar 

pines (Gayton, 1948; Corliss, 1989) and probably also from 

Jeffrey pines and ponderosa pines. Sugar pines are particularly 

abundant in the basin belt, and carbonized sugar pine nuts 

were excavated from an Indian campsite at Sunset Point (Dil-
Acknowledgments 13

lon, 1992). Sugar pine cones were obtained by men climbing 

trees and picking cones by twisting, cutting with a sharp rock, 

or knocking them off with a club. The cones were not permitted to ripen on the tree because when they matured and opened 

the seeds would be scattered irretrievably. Each cone would 

be a prize, containing on average 150 seeds weighing a total 

of about 32 g and containing 190 Kcal of nourishment (Farris, 

1982). The women collected the cones in piles and burned off 

the pitch. Then the nuts were released from the cone by “setting the butt down on a rock and striking the tip with a heavy 

stone. They split into about three sections and the nuts fell 

out. . . The nuts to be eaten were first parched with coals on 

a basket tray. Care was needed to prevent scorching. Sometimes after being cooked, they were pounded in a mortar hole, 

the greasy mass then being rolled into balls and eaten as an 

accompaniment to acorn mush.” (Gayton, 1948). 

The basins could be used to store the cones, and as a 

place to split and pound them in order to collect and save the 

released seeds. The basins could also provide a receptacle 

to burn the pitch off cones or to serve as an oven to heat the 

cones, causing them to release nuts (Dillon, 1992). Kroeber 

(1925) mentions, in referring to habits of the Tubutalabal 

tribelet, that pine nuts were “. . . cached in circular stone-lined 

pits about five feet in diameter and two and one-half feet deep, 

located near the piñon gathering areas.” The granite basins, 

which were of this size, would be ideal for such storage and 

could be rendered more rodent proof. Fires in the basins would 

be convenient to provide coals for parching and hot stones for 

boiling. These fires would also disaggregate the underlying 

stone, thereby facilitating the further deepening of the basins. 

Conclusions

A total of 221 sites of meter-size granite basins are 

found in a 180-km belt extending south from the South Fork 

of the Kings River to a site west of Lake Isabella on the west 

slope of the southern Sierra Nevada. Most basins occur in 

clusters on bedrock outcrops at an average elevation of 1,950 

m. Individual sites have 1 to 31 basins, and 80 percent of the 

sites also contain bedrock mortars of the type used by Native 

Americans to grind acorns. The north half of the basin belt is 

close to the western limit of the earliest and most extensively 

documented glaciation on the west slope of the southern 

Sierra, but the south half is not adjacent to any known past 

glacial action.

The median basin diameter among the basin sites 

ranges from 89 to 170 cm, the median depth ranges from 

12 to 63 cm, and the volume from 40 to 1,400 liters. The 

median maximum volume of basins at the 30 sites measured 

in detail is about 300 liters. In median diameter and depth, 

basins in the north district of the overall belt of sites tend to 

be greatest in diameter and shallowest, those in the middle 

district are medium in diameter and deepest, and those in the 

south district are smallest in diameter and medium in depth. 

The boundary between the north and middle district is close 

to the boundary of the lands occupied by the Monache and 

Tubutalabal tribelets, respectively.

The basins do not appear to be natural features—neither 

waterworn bedrock potholes nor weathering pits. Features that 

suggest a manmade origin for the basins are the following: 

(1) restricted size, shape, and elevation range, (2) common 

association with Indian middens and grinding mortars, (3) 

a south- and west-facing aspect, (4) the concentration of 

different shapes in distinct localities, and (5) their location in 

a food-rich belt with pleasant summer weather. A volcanic 

ash that erupted from the Mono Lake area at A.D. 1240±60 

has been found in the very bottom of several of the basins, 

indicating that they were used shortly before that time but not 

thereafter. 

It is likely that the basins were made by grinding and 

hammering with stones (as with the smaller mortars), probably 

after heating the rock up to about 500°C with campfires. Such 

heating would weaken the stone and greatly reduce the time 

and effort needed to deepen the basins. 

The common association of mortars with basins strongly 

suggests that the primary purpose of the basins was in 

processing of food, primarily acorns and pine nuts. Acornbearing black oaks and pines that bear nuts—sugar, Jeffrey, and 

ponderosa—grow abundantly near the basin zone. Acorns were 

normally processed in a water-containing vessel three times: for 

soaking to soften shells, leaching to remove tannin, and cooking 

(hot-stone boiling of mush or baking of cakes). Traditionally, 

the soaking and cooking were done in watertight baskets and 

the leaching in sand basins. The granite basins could serve 

all three purposes. Likewise, the basins would be useful for 

processing pine nuts—storing cones and nuts, burning the pitch 

off cones, and splitting cones to release and collect the nuts. 

The 180-km-long belt of granite basins at mid elevations 

on the west slope of the Sierra Nevada is indeed a remarkable 

feature. More than 1,000 basins averaging 130 liters in volume 

were apparently excavated by a civilization that left few other 

lasting relicts. The quarrying of this 130,000 liters (325 tons) 

in solid granite represents an enormous expenditure of energy. 

The basins are among the largest and most permanent artifacts 

remaining from the California Indian civilization.

Acknowledgments

Special recognition is due the numerous workers 

who contributed information on the basins as part of a 

multiagency program that includes members of the Southern 

Sierra Archaeological Society, the California Division of 

Forestry and Fire Protection, Sequoia National Forest, the 

U.S. National Park Service, and the U.S. Geological Survey. 

Thomas Sisson aided in field mapping as well as heating 

experiments to assess rock strength. Silvia Haultain provided 

data and advice on vegetation types in Sequoia National Park. 

John Gallaway, Gail Mahood, Jack Stewart, and Muriel Myers 

reviewed the manuscript and offered valuable advice. We are 

grateful for this help. 
14 Origin of Meter-Size Granite Basins in the Southern Sierra Nevada, California

References

Barnes, E.K., 1984, Sierra sub-glacial potholes; their significance in California geology, with a note on archaeology: 

Research paper on file at Sequoia National Park [cited in 

Dulitz, 2000]. 

Barton, Orlando, 1881, Early history of Tulare County; important facts gathered from reliable sources preserved in ink: 

Letter to H. H. Bancroft as reported in Visalia Daily Times, 

17 October 1905. 

Corliss, D.W., 1989, Native food resources and archaeological 

sites in the Tule River drainage, Tulare County, California: 

U. S. Forest Service, Tule River Ranger District, Oct. 1989, 

53 p.

Dillon, B.D., 1992, Excavations at the Sunset Point Site (CATUL-1052) Mountain Home Demonstration State Forest, 

Tulare County, California: California Division of Forestry 

Archaeological Reports, no. 11, p. 69-108, reprinted by 

Coyote Press, Salinas, California. 

Dulitz, D., 2000, Rock basins in Mt. Home State Forest and 

immediate vicinity: Manuscript on file at California Division of Forestry Archaeology Office, Sacramento, and 

posted on the California Division of Forestry Archaeology 

Program Web Site.

Elsasser, A.B., 1972, Indians of Sequoia and Kings Canyon 

National Parks: Three Rivers, Calif., Sequoia Natural History Association, 56 p. 

Farris, G.J., 1982, Pine nuts as an aboriginal food source in 

California and Nevada; some contrasts: Journal of Ethnobiology, v. 2, p. 114-122. 

Foster, D.G., Kauffman, E., Jenkins, R., and Betts, J., 1991, 

Archaeological testing at the Salt Creek Ridge Site (CATUL-472); a southern Sierra rock basin and bedrock mortar 

encampment on Case Mountain, Tulare County, California: 

California Department of Forestry and Fire Protection, 

Archaeological Reports No. 5, 22 p.

Gage, M., and Gage, J., 2005, The art of splitting stone; early 

rock quarrying methods in pre-industrial New England, 

1630–1825 (2nd ed): Amesbury, Maryland, Powwow River 

Books, 88 p. 

Gayton, A. H., 1948, Yokuts and western Mono ethnography, 

Tulare lake, Southern Valley, and Central Foothills Yokuts: 

Berkeley, University of California Press, Anthropological 

Records, v. 10, no. 1, 142 p.

Gehr, E., Conton, L, Parella, D., and Stott, J., 1979, Cultural 

resources survey and evaluation of Range 31 E, Tule River 

Indian Reservation: Tuscon, National Park Service, Western 

Archaeological Center, 20 p.

Gilbert, G.K., 1906, Moulin work under glaciers: Geological 

Society of America Bulletin, v. 17, p. 317-320. 

Gorden, M., 2007, Granite basins in the Sierra Nevada mountains of California (abs.): Society for California Archaeology, 2007 annual meeting, March 22-25, San Jose, California, p. 73. 

Hall, A.F., 1930, A guide to Sequoia and General Grant 

National Parks: Berkeley, Calif., National Parks Publishing 

House, 151 p.

Johnson, Clay, 2004, Archaeological sites and fire-induced 

changes, in Runswig, R.H., and Butler. W.B., eds., Ancient 

and historic lifeways in North America’s Rocky Mountains: 

Proceedings of the Rocky Mountain Anthropological Conference, Estes Park, Colorado, 16 p.

Kroeber, A.L., 1925, Handbook of the Indians of California: 

Washington, D.C., Bureau of American Ethnology, Smithsonian Institution, 995 p.

Larsson, Kristina, 2006, Fires in tunnels and their effect on 

rock: Lulea, Sweden, Lulea University of Technology, 

Research Report, 48 p. 

Matthes, F.E., 1930, Geologic history of the Yosemite Valley: 

U.S. Geological Survey Professional Paper 160, 137 p. 

McCarthy, H., Hicks, R.A. and Blount, C.M., 1985, A functional analysis of bedrock mortars; western Mono food processing in the southern Sierra Nevada, in Cultural Resources 

of the Crane Valley Hydroelectric Project Area: Pacific Gas 

and Electric Company, p. 303–356. 

Migon, Piotr, 2006, Granite landscapes of the world: Oxford 

Press, 384 p.

Moore, J.G., and Mack, G., 2008, Limits of Tahoe glaciation 

in Sequoia and Kings Canyon National Parks, California: U. 

S. Geological Survey Scientific Investigations Map 2945, 

scale 1:125,000.

Moore, J.G., and Nokleberg, W.J., 1992, Geologic map of the 

Tehipite Dome quadrangle, Fresno County, California: U. 

S. Geological Survey Geologic Quadrangle Map GQ-1676, 

scale 1:62500.

Moore, J.G., and Sisson, T.W., 1987, Preliminary geologic 

map of Sequoia and Kings Canyon National Parks: U. 

S. Geological Survey Open File Report 87–651, scale 

1:125,000. 

Moratto, M.J., 1984, California archaeology: Orlando, Fla., 

Academic Press, Inc., 757 p.

Mundy, W.J., 1990, The 1985 and 1986 Generals Highway 

Archaeological Survey, Sequoia National Park, California: 

Yosemite Research Center, National Park Service, Publications in Anthropology, no. 10, 26 p. 
References 15

National Park Service, 2007, Vegetation map for Sequoia 

and Kings Canyon National Parks: National Park Service, 

Sequoia and Kings Canyon National Parks, Three Rivers, CA 93271 [http://science.nature.nps.gov/nrdata/, last 

accessed May 15, 2008].

Osborne, R.H., 1998, The experimental replication of a stone 

mortar: Lithic Technology, v. 23, no. 2, p. 116-123.

Otter, F., 1979, The view from Hatchet Peak; ‘bathtubs’ probably natural: Tule River Times, September 6; and The view 

from Hatchet Peak; does weathering explain bathtubs?: Tule 

River Times, September 13. 

Plotnicov, L. and Elsasser, A.B., 1961, Additional notes on the 

granite basins in Sequoia National Park: Report to National 

Park Service, p. 24-37. 

Presnell, C.C., 1930, Unusual rock basins in Yosemite: 

Yosemite Nature Notes, v. 9, p. 107-108.

Pusateri, S.J., 1962, Rock basins of Sierra; natural or made by 

man?: Woodlake, Calif., Woodlake Echo, a series of three 

articles on August 9, 16, 23 appearing also in Exeter, Calif., 

Exeter Sun [cited in Barnes, 1984]. 

Sandelin, L.C., 2000, Inventory project of the rock-basin sites 

of the southern Sierra Nevada of California: California 

Department of Forestry and Fire Protection Special Report, 

February 14, 2000, 10 p. 

Schutt, H.G., 1962, Prehistoric Rock Basins: Visalia, Los 

Tulares, Quarterly Bulletin of the Tulare County Historical 

Society, v. 54, p. 1-2. 

Sisson, T.W., and Moore, J.G., 1994, Geologic map of the 

Giant Forest quadrangle, Tulare County, California: U. S. 

Geological Survey Geologic Quadrangle Map GQ-1751, 

scale 1: 62,500. 

Stewart, G.W., 1929, Prehistoric rock basins in the Sierra 

Nevada of California: American Anthropologist, new series, 

v. 31, no. 3, p. 419-430. 

Streckeisen, A., chairman, 1973, Plutonic rocks—classification and nomenclature recommended by the IUGS Subcommission on the systematics of igneous rocks: Geotimes, v. 

18, no. 10, p. 26-30. 

Tarr, W.A., 1915, A study of some heating tests, and the light 

they throw on the cause of the disaggregation of granite: 

Economic Geology, v. 10, p. 348-367. 

Tinsley, J.C., 1982, Tephrochronology of sinkhole deposits 

in the Redwood Canyon karst, Sequoia and Kings Canyon 

National Parks: Washington, D.C., Cave Research Foundation Annual Report, p. 23-25.

Turner, H.W., 1892, Glacial pot-holes in California: American 

Journal of Science, v. 44, p. 453-454.

Twidale, C.R., 1982, Granite landforms: Amsterdam, Elsevier, 

372 p. 

Wallace, W.J., 1993, The great Indian bathtub mystery 

solved?: California Division of Forestry Archaeological 

Reports, no. 13, p. 373-378, reprinted by Coyote Press, 

Salinas. 

Weinberger, Gay, 1981, Indian slides and “bathtubs”—archaeological enigmas of the southern valley and foothill Yokuts: 

Southern Sierra Archaeological Society Meeting, Bakersfield, April, 1981.

Wood, S.H., 1977, Distribution, correlation and radio-carbon 

dating of late Holocene tephra, Mono and Inyo craters, 

eastern California: Geological Society of America Bulletin, 

v. 88, p. 89-95. 
Moore and others—Origin of Meter-Size Granite Basins in the Southern Sierra Nevada, California—Scientific Investigations Report 2008-5210