Prepared in cooperation with the Pyramid Lake Paiute Tribe 

and the Pyramid Lake Museum Visitor Center 

The Tufas of Pyramid Lake, Nevada 

U.S. Geological Survey Circular 1267 

U.S. Department of the Interior 

U.S. Geological Survey 

The Tufas of Pyramid Lake, Nevada 

By Larry Benson 

Prepared in cooperation with the Pyramid Lake Paiute Tribe 

and the Pyramid Lake Museum Visitor Center 

U.S. Geological Survey Circular 1267 

U.S. Department of the Interior 

U.S. Geological Survey 
ii 

U.S. Department of the Interior 

Gale A. Norton, Secretary 

U.S. Geological Survey 

Charles G. Groat, Director 

U.S. Geological Survey, Reston, Virginia, 2004 

Free on application to: U.S. Geological Survey, Information Services 

Box 25286, Denver Federal Center 

Denver, CO 80225 

For more information about the USGS and its products: 

Telephone: 1-888-ASK-USGS 

World Wide Web: http://www.usgs.gov/ 

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply 

endorsement by the U.S. Government. 

Suggested citation: 

Benson, L.V., 2004, The Tufas of Pyramid Lake, Nevada: U.S. Geological Survey Circular 1267, 14p. 

Library of Congress Cataloging-in-Publication Data 

Benson, Larry V. 

The tufas of Pyramid Lake, Nevada I by Larry Benson 

p. em/ -- (U.S. Geological Survey circular ; 1267) 

"Prepared in cooperation with the Pyramid Lake Paiute Tribe and the Pyramid Lake 

Museum Visitor Center." 

ISBN 0-607-97555-5 (alk. paper) 

1. Rocks, Carbonate--Nevada--Pyramid Lake. 2. Calcium carbonate--Nevada--Pyramid 

Lake. 3. Geology, Stratigraphic--Quaternary. 4. Geology--Nevada--Pyramid Lake. 

5. Petrology--Nevada--Pyramid Lake. 6. Pyramid Lake (Nev.)--Geology. I. Title. II. Series 

OE471.15.C3B46 2004 

552' .5--dc22 2004049410 
iii 

Contents 

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

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

Tufa Varieties and Forms ............................................................................................................................. 3 

The Elevation of Tufa Deposits And Their Relation To Overflow Points ............................................ 10 

The Terraces of Anaho Island .................................................................................................................. 10 

Elevational History of Pyramid Lake/Lake Lahontan ............................................................................. 12 

Recent Tufa Formation ............................................................................................................................... 12 

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

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

Figures 

Figure 1. Photo of Pyramid Island along the east shore of Pyramid Lake ........................................ 1 

Figure 2. Schematic of Pluvial Lake Lahontan at its highstand about 15,000 years ago ................ 2 

Figure 3. Graph of lake elevation in the Pyramid Lake subbasin between 35,000 and 9,500 calendar years before present (cal. yr. B.P.) .................................................................................. 2 

Figure 4. Map of locations of tufa sites described in this report ........................................................ 2 

Figure 5. Photo of dense tufa coating volcanic cobbles in the Terraced Hills area ........................ 3 

Figure 6. Photo of tubular tufas from the Popcorn Rocks site ............................................................ 3 

Figure 7. Photo of tufa pillows at Doghead Rock composed of branching tufa (B) and dense (D) 

tufa pendants and nodules ......................................................................................................... 3 

Figure 8. Photo of thinolite crystals exposed atthe base of the Blanc Tetons site ......................... 4 

Figure 9. Photo of calcium-carbonate cemented thinolite crystals at the Pelican Point site ....... 4 

Figure 10. Photo of large mushroom tufas at the Pelican Point site composed of layers of broccoli-like branching tufa and dense tufa nodules .................................................................... 5 

Figure 11. Photo of layers of beachrock adjacentto and north of Indian Head Rock ....................... 5 

Figure 12. Photo of the southern Blanc Tetons mound .......................................................................... 6 

Figure 13. Photo of tufa pillows making up a reef-like tufa on Anaho Island ..................................... 6 

Figure 14. Photo of tufa tubes at the base of Dog Head Rock .............................................................. 6 

Figure 15. Photo of broken tufa barrel at Needles Rocks site .............................................................. 6 

Figure 16. Photo of reef-like tufa sheets and drapes near the summit of Anaho Island ................... 6 

Figure 17. Photo of multiple generations of thinolite crystals inside an overturned tufa barrel at 

the Needles Rocks site ............................................................................................................... 7 

Figure 18. Photo of the Indian Head Rock tufa mound ........................................................................... 7 

Figure 19. Photo of a tufa mound at the Needles Rocks site composed of interlocking spheres 

and barrels ................................................................................................................................... 7 

Figure 20. Photo of the Pyramid Island tufa mound ............................................................................... 8 

Figure 21. Photo of the tufa reefs coating Marble Bluff ......................................................................... 8 

Figure 22. Photo of cross-sectional view through a tufa reef at Marble Bluff .................................. 8 

Figure 23. Schematic sequence of tufa deposition at the Blanc Tetons site .................................... 9 

Figure 24. Photo of the Needles Rocks site at the north end of Pyramid Lake .................................. 9 
iv 

Figure 25. Schematic of the relation of tufa dome heights and Marble Bluff tufa varieties and 

forms to overflow (sill) elevations .......................................................................................... 10 

Figure 26. Photo of Anaho Island ............................................................................................................ 11 

Figure 27. Photo of broken tufa mound at Dog Head Rock showing tubes and surrounding tufa 

that have been thoroughly cemented with younger calcium carbonate .......... " ............. 12 

Figure 28. Photo of tufa mound at the Needles Rocks site, whose base has been heavil ... 

cemented with younger calcium carbonate .......................................................... " ............ 13 
The Tufas of Pyramid Lake, Nevada 

By La rry Benson 

ABSTRACT 

Pyramid Lake is the site of some of the Earth's 

most spectacular tufa deposits. The tufas are composed of calcium carbonate (CaC03

). The large 

tufa mounds, reef- and sheet-like tufas formed 

within Pyramid Lake, between 26,000 and 13,000 

years (yr) ago, when the lake was part of pluvial 

Lake Lahontan. The mounds are composed of large 

interlocking spheres that contain multiple generations of a crystalline (thinolite) variety of tufa. 

Over time many of the mounds have fallen apart, 

exposing an internal network of tubes. The tubular 

structures are thought to have been created when 

springs discharged from the bottom of Pyramid 

Lake, supplying calcium that combined with carbonate dissolved in lake water to form the mounds. 

The reef- and sheet-like deposits contain pillow and 

pendant forms made up of a branching variety of 

tufa that often grades into dense layers or nodules. 

Dense layers of tufa also coat cobbles and boulders 

that were deposited in near-shore shallow-water 

areas. The thickest tufa deposits formed at lake-bottom sites of ground-water discharge and at overflow 

elevations' where the lake was held at near-constant 

levels for long periods of time. 

INTRODUCTION 

The U.S. Geological Survey, in cooperation 

with the Pyramid Lake Paiute Tribe, has obtained 

radiocarbon ages of many of the tufa deposits that 

border Pyramid Lake in order to obtain a record of 

lake level change for the past 35,000 years. This 

record has been used to construct a theory of climate change wherein changes in lake level are 

associated with the position of the polar jet stream 

relative to the Lahontan Basin (Benson and others, 

Figure 1. Pyramid Island along the east shore of Pyramid Lake. The 

white band along the shore is composed of calcium carbonate 

that precipitated from the lake when its level was at or near its 

overflow point to the Winnemucca Lake subbasin. 

1995). When the jet stream passes over the basin, 

Pyramid Lake increases in size in response to the 

increased precipitation that accompanies the frontal 

systems that define the boundary of the jet stream 

(Benson and others, 1995). The tufa deposits that 

border Pyramid Lake are unique in terms of their 

size and beauty. By drawing attention to their history of formation we hope to alert the public to their 

special nature and the need for their preservation. 

Tufa is a rock composed of calcium carbonate 

(CaC03

) that forms at the mouth of a spring, from 

lake water, or from a mixture of spring and lake 

water. Tufas in the Pyramid Lake subbasin were 

first mentioned in the literature by Fremont (1845), 

who erroneously believed they had formed above 

water. Fremont named the lake after the pyramidalshaped island that lies along the eastern shore of 

the lake (Fig. 1). The Paiute name for the island is 

Wono, meaning cone-shaped basket; and the Paiute 

name for the lake is Cui-Ui Panunadu, meaning fish 

in standing water. 
2 The Tufas of Pyramid lake, Nevada 

Pyramid Lake is one of seven water bodies that 

coalesced to form pluvial Lake Lahontan (Fig. 2). 

At its highstand, Lake Lahontan was 281 m deep 

in the Pyramid Lake subbasin (compared to 106 

m today) and covered 22,800 km2

, a surface area 

slightly larger than present-day Lake Ontario. During the very wet period that caused Lake Lahontan 

to form and grow (Fig. 3), massive tufa deposits 

formed in the Pyramid Lake subbasin (Benson and 

others, 1995). 

Figure 2. Pluvial Lake Lahontan at its highstand about 15,000 

years ago. The blue area indicates the surface area of Lake 

Lahontan. The black areas indicate perennial lakes that exist 

today. The gray areas indicate ephemeral lakes and sinks. The 

red lines indicate overlfow points (sills) between subbasins. 

Sill elevations around Pyramid Lake are Darwin Pass (1 ,265 m), 

Mud Lake (1,177 m), Astor Pass (1 ,222 m), and Emerson Pass 

(1 ,207 m). 

41 ' 

40 ' 

1 Pronto 

2 Chocolate 

3 Adrian Valley 

4 Darwin Pass 

5 Mud Lake 

6 Astor Pa ss 

7 Emerson Pass 

SUBBASINS 

Smoke Creek-Black 

Rock Desert SC 

Carson Desert CD 

Buena Vista BV 

Walker Lake WL 

Pyramid Lake PL 

Winnemucca Lake WI 

Honey Lake HL 

1300 

1250 

1200 

10 15 20 25 30 35 40 

AGE (103 CALENDAR YR BEFORE PRESENl) 

Figure 3. Lake elevation in the Pyramid Lake subbasin between 

35,000 and 9,500 calendar years before present (cal. yr. B.P.) 

Dates on packrat middens indicate times during and after which 

lake level could not have risen to the elevations of the middens 

without destroying them (Benson and others., 1995). 

PYRAMID 

LAKE 

Figure 4. Locations of tufa sites described in this re port. 
TUFA VARIETIES AND FORMS 

The locations of tufas described in this report 

are shown in Figure 4. Pyramid Lake tufas can be 

classified, if somewhat arbitrarily, by variety, form, 

and megaform. Russell (1885) was the first to suggest that there were three tufa varieties, including 

lithoid (dense), thinolitic (crystalline), and dendritic 

(branching). Two other varieties have been noted 

in the Pyramid Lake area: A fine-grained carbonate 

that cements sand and gravel forming beachrock, 

and a thin white porous carbonate that coats the 

outer surfaces of older tufas. 

Figure 5. Dense tufa coating volcanic cobbles in the Terraced Hills 

area. 

The dense variety of tufa is found as a coating 

on gravel and cobbles (Fig. 5), as concentric layers 

in the outer parts of tubes (Fig. 6), and as nodules 

and pendants that formed when branching tufa 

coalesced (Fig. 7). Thinolitic tufa consists of long 

fragile crystals (Fig. 8); however, if the thinolitic 

tufa is later exposed to lake water, it may become 

cemented with additional CaC03

, giving it a dense 

and massive appearance (Fig. 9). Branching tufa 

often looks like composite heads of broccoli (Fig. 

10); however, it can assume other forms (for example, Fig. 7). Beachrock forms where calcium-rich 

ground water mixes with carbonate·-rich lake water, 

precipitating CaC03 that cements sand and gravel 

into concrete-like layers. Layers of beachrock are 

visible at the Indian Head Rock site (Fig. 11) and 

just upslope from the Popcorn Rocks site. A porous 

white coating of tufa can be found on the bases of 

Tufa Varieties and Forms 3 

many of the mounds that surround Pyramid Lake 

(Fig. 12). The coating does not extend above an 

elevation of 1,183 m and probably formed at times 

during the last 9,500 years when the lake was below 

its overflow point to Winnemucca Lake subbasin. 

Tufa varieties combine to become tufa forms. 

Common forms include: (1) tufa pillows (Figs. 7, 

13), composed of branching tufa and dense tufa 

nodules; (2) tufa tubes, composed of dense (Fig. 14) 

Figure 6. Tubular tufas from the Popcorn Rocks site. The outer 

light-colored concentric layers are composed of dense tufa (D); 

the inner dark areas are composed of thinolite crystals (T). The 

labeled tube is about 35 em in diameter. 

Figure 7. Tufa pillows at Doghead Rock composed of branching 

tufa (B) and dense (D) tufa pendants and nodules. 
4 The Tufas of Pyramid Lake, Nevada 

Figure 8. Thinolite crystals exposed at the base of the Blanc 

Tetons site. 

or branching (Fig. 15) varieties of tufa that sometime surround a thinolitic crystal mesh (Fig. 8); (3) 

tufa sheets and drapes (Fig. 16), which are primarily 

composed of branching tufa; and ( 4) tufa spheres 

or barrels (Fig. 17), commonly composed of one 

or more layers of thinolitic crystals. In some situations, tufa forms combine to create tufa megaforms, 

such as tufa mounds (Figs.12, 18, 19, 20) and tufa 

reefs (Figs. 21, 22). The constructional history of 

the mounds can be complex as indicated by a structural schematic of the Blanc Tetons mound (Fig. 

23). At this site, tubes in the center of the mound 

are overlain by a thick layer of thinolitic tufa (Fig. 

8). The next layer that was deposited consists of 

thinolitic tufa that grades into a branching variety 

of tufa. Two layers of branching tufa were then 

deposited and capped by a thin layer of dolomite 

(CaMg(C03)) and a dense layer of laminated tufa. 

Two layers of porous encrusting tufa coat the laminated tufa. 

The largest collection of mounds occurs at the 

north end of Pyramid Lake at the Needles Rocks 

site. At this site, calcium from hot springs mixed 

with carbonate from lake water to form mounds that 

straddle two fault lines (Fig. 24). 

Thinolitic tufas, or thinolites are thought to be 

chemical precipitates that originally had the composition CaC03

·6HfO; that is, they precipitated as the 

mineral ikaite, which suggests the presence of very 

cold water (Shearman and others, 1989). The thinoFigure 9. Calcium-carbonate cemented thinolite crystals at the 

Pelican Point site. Note the outer porous-tufa coating. 

lites have since recrystallized to a more stable form 

of calcium carbonate (calcite). Given their fragile 

nature, the ikaite crystals probably grew within lake 

sediments. The branching variety of tufa may have 

been deposited in association with algae. Enormous 

calcareous cyanobacterial (blue-green algae) microbialities (stromatolites) that resemble Pyramid Lake 
Figure 10. Large mushroom tufas atthe Pelican Point site composed of layers of broccoli-like branching tufa and dense tufa 

nodules. 

Tufa Varieties and Forms 5 

tufa mounds have been found growing in the saline 

waters of Lake Van, Turkey (Kemp and others, 

1991). The dense forms of tufa may have precipitated chemically (for example, cobble coatings) 

or they may have been associated with algae (for 

example, the concentric dense layers that formed 

the outer parts of tubular tufas). 

Figure 11. Layers of beachrock adjacent to 

and north of Indian Head Rock. 
6 The Tufas of Pyramid Lake, Nevada 

Figure 12. The southern Blanc Tetons mound. Large tufa spheroids 

have been coated and cemented with white porous tufa. 

Figure 13. Tufa pillows making up a reef-like tufa on Anaho Island. 

Figure 14. Tufa tubes at the base of Dog Head Rock. The tubes 

range in diameter from 1 to 3 em. 

Figure 15. Broken tufa barrel at Needles Rocks site. Vertical 

tubes are composed of dense tufa near the base that becomes 

more branching in character near the top of the barrel. Note the 

multiple layers of thinolite crystals (T) that drape the branching (B) 

part of the barrel. The barrel is about 4 m high. 

Figure 16. Reef-like tufa sheets and drapes near the summit of 

Anaho Island. 
Figure 17. Multiple generations of thinolite crystals inside an overturned tufa barrel at the Needles Rocks site. 

Figure 19. A tufa mound at the Needles Rocks site composed of 

interlocking spheres and barrels. The center barrel is about 4 m 

high. 

Tufa Varieties and Forms 7 

Figure 18. The Indian Head Rock tufa mound composed of interlocking tufa spheres and barrels. 
8 The Tufas of Pyramid Lake, Nevada 

Figure 20. The Pyramid Island tufa mound. Note the girdle of carbonate cement located about one-fifth up the mound. This girdle 

formed when Pyramid Lake was at or near its overflow point to the 

Winnemucca Lake subbasin. 

Figure 21. The tufa reefs coating Marble Bluff. Note that the tufa 

pillows at the top of the outcrop tend to be aligned horizontally, 

whereas the tufa sheets near the base of the outcrop tend to be 

near vertical. 

Figure 22. Cross-sectional view through a tufa reef at Marble 

Bluff. The outer half of the reef consists of pillow forms (P) and 

the inner half of the reef is characterized by dense nodular (N) 

tufa. 
Tufa Varieties and Forms 9 

ELEVATION 1174 m 

\ /-...... 

\I \ 

-----

v \ 

I EPOSIT 1167 :0 \ 

~~

PALEOBEACH .£. - - ;-" ;"i o \ 

~ 

cP, ocf' o'1 /, ...... \ 

I 1 I \ \ 

I I \ \ \ 

I I \ \ 

I I \ '-

1 I \ \ 

I I \ 

I TUBULAR \ 

I TUFA COMPLEX \ 

I \ 

I \ 

/ \ 

~ / \ 

~OUNG THINOLITIC TUFA 

FRACTURED TUFA SPHEROID 

ELEVATION 1160 m J 

THINOLITIC-BRANCHING TUFA TRANSITION - -

------ ---- POORLY ORIENTED YOUNG BRANCHING TUFA 

Figure 23. Schematic sequence of tufa deposition at the Blanc Tetons site. The mound is approximately 17m high. 

Figure 24. The Needles Rocks site at the north end of Pyramid Lake. The top of the white carbonate coating/ 

cement at the base of the mounds is at the elevation of the overflow point from the Pyramid Lake subbasin to the 

Winnemucca Lake subbasin. The tallest ofthe mounds reaches and elevation of 1,265 m, or about 105m above 

lake level. 
10 The Tufas of Pyramid Lake, Nevada 

THE ELEVATION OF TUFA DEPOSITS 

AND THEIR RELATION TO OVERFLOW 

POINTS 

Because tufas form in lake water, it follows that 

their vertical growth is limited by lake level. In the 

Pyramid Lake subbasin, the elevations of the tops 

of many tufa mounds correspond to elevations of 

intersubbasin overflow points (Fig. 2). The tops of 

the tallest mounds in the Needles Rocks site (Figs. 

4, 24) and the top of Pyramid Island (Fig. 20) reach 

the height of Darwin Pass Sill that connects the 

Pyramid Lake and Carson Desert subbasins (Fig. 2). 

The eroded top of Indian Head Rock (Figs. 4, 18) 

reaches 1,207 m, the same elevation as the Emerson 

Pass Sill that connects the Pyramid Lake and Smoke 

Creek-Black Rock Desert subbasins (Fig. 2). Tops 

of mounds at the Pelican Point, Popcorn Rocks, 

and Blanc Tetons sites (Fig. 4) have been eroded to 

1350 

1340 

1330 

1320 

1310 

w,..._ 1300 >N 

0~ 1290 

Cl):::> 

<(I- 1280 

(/)<( 1270 o::::o 

1,177 m, the present elevation of the Mud Lake Sill 

that connects the Pyramid Lake and Winnemucca 

Lake subbasins (Fig. 2). The elevations of tufa 

forms and varieties that coat bedrock on the sides 

of the Pyramid Lake subbasin also can be related to 

overflow elevations. Figure 25 shows the relation of 

tufa dome heights and Marble Bluff tufa forms and 

varieties to overflow elevations. 

THE TERRACES OFANAHO ISLAND 

When the level of Pyramid Lake was held constant by overflow to an adjacent subbasin, erosion 

of tufa and sediment occurred at and slightly above 

the overflow level, and deposition of tufa occurred 

below the overflow level. Four principal terraces 

were created by both erosional and constructional 

wz 1260 

tu<( 

~0 1250 

zO:::: 1240 -w 

z~ 1230 Q<( 

BR~~~~7N~P~~~~LIK \j. '$. AND PENDULAR TUFAS (/'/ 

UPPER LIMIT OF YOUNG f?, REEFS 

THINOLITIC 

HIGHLY 

TU FA~ 

WEATHERED 

I-I 1220 

<(I- >0:::: 1210 

UNDIFFERENTIATFD CARBONATE 

TUFAS CEMENTED TALUS 

EMERSON PASS SILL 

wo ------- ......lz w 

1200 

1190 

YOUNG DENSE LAMINATED TUFA 

Figure 25. The relation of tufa dome heights and Marble Bluff tufa varieties and forms to overflow (sill) elevations. Because of their complexity, the internal structures of the tufa mounds that border Pyramid Lake have not been illustrated. 
processes at elevations of the Lahontan highstand 

and the Mud Lake, Emerson Pass, and Darwin Pass 

sills. The lowest of four principal terraces occurs 

between elevations of 1, 177 and 1, 183 m, the 

elevational range of the Mud Lake Sill. The white 

"bathtub ring" that surrounds Pyramid Lake (Fig. 

1) coats this terrace. On Anaho Island this terrace 

is represented by a broad flat erosional surface that, 

in some places, is coated with a white carbonate 

cement (MT in Fig. 26). The middle terrace also is 

clearly visible on Anaho Island. It consists of a low, 

relatively flat bench (ET in Fig. 26) that extends 

from 1,207 to 1,210 m, the elevation of the overflow point (Emerson Pass Sill) to the Smoke Creek 

Desert. The outer edge of the upper terrace is at 

1,267 m, approximately the elevation of the overflow point (Darwin Pass Sill) to the Carson Desert 

subbasin. The uppermost terrace on Anaho Island 

The Terraces of Anaho Island 11 

(labeled DT in Fig. 26) and on Marble Bluff (Fig. 

25) is constructional in nature, consisting of reefform tufas (pendants and pillows) that extend tens 

of meters below 1,267 m. A poorly developed erosional terrace also is present at 1,267 m. The highest 

terrace in the Pyramid Lake subbasin occurs at an 

elevation of 1,337 m. It consists of a wedge-shaped 

platform of rounded cobbles and gravel (Fig. 25) 

and indicates the maximum level achieved by Lake 

Lahontan about 15,000 years ago. Anaho Island did 

not record this terrace as the island is only 1,334 m 

in height. 

Figure 26. Anaho Island. The top of the island is at an elevation of 1,334 m, 3m below the Lahontan highstand. A change from steeply 

dipping sheet- to quasi-horizontal pillow-form tufas occurs at 1,267 m where a poorly developed erosional terrace is sometimes present. 

The Darwin Terrace (DT) corresponds in elevation to the Darwin Pass Sill (elevation= 1,265 m). The Emerson Pass Terrace (ET) occurs 

as a broad erosional platform about one-fifth up the side of the island. It corresponds in elevation to the Emerson Pass Sill (elevation= 

1,207 m). The Mud Lake Terrace (MT) is the broad platform at the bottom of the photo. It corresponds in elevation to the Mud Lake Sill 

(elevation = 1,177-1,183 m). 
12 The Tufas of Pyramid Lake, Nevada 

ELEVATIONAL HISTORY OF PYRAMID 

LAKE/LAKE LAHONTAN 

Many of the tufas illustrated in this and other 

reports (Benson, 1994) have been dated using the 

radiocarbon method (Benson and others, 1995). 

The dates were converted to calendar years using a 

correlation between the layer-counted oxygen-18 

(8 180) record from the Greenland Ice Sheet Project 

2 (GISP2) ice core and the radiocarbon dated 8'80 

record in a sediment core from the North Atlantic 

(Voelker and others, 1998). The elevations and ages 

of the tufa samples allow the construction of a lakelevel envelope for the last 35,000 years (Fig. 3). 

The data indicate that the lake in the Pyramid Lake 

subbasin rose sharply about 26,000 years ago and 

was maintained at an elevation of about 1 ,265 m 

from 25,000 to 18,000 years ago by overflow to the 

Carson Desert. After a brief fall to less than 1,250 

m, Lake Lahontan rose rapidly to its highstand 

about 15,000 years ago and then fell rapidly about 

14,000 years ago. 

RECENT TUFA FORMATION 

Deposition of tufa megaforms appears to have 

ended with the fall of Lake Lahontan between 

14,000 and 13,000 years ago (Fig. 3). We do not 

know why tufa deposition essentially ceased after 

that time; however, decreases in the discharge of 

lake-bottom springs may have sharply lessened the 

amount of calcium available for tufa precipitation. 

Accurate dates for apparently recent encrusting 

varieties of tufa are not available. Their ages are 

estimated to range from 2,055 to 5,820 calendar 

years before present (BP); however, these estimates 

may be too large, depending on how much "old" 

carbon was introduced into the tufas by groundwater sources during their precipitation (Benson and 

others ,1995). For example, modem tufa, precipitated from a hot spring that emerges from the side 

of Pyramid Island, has yielded a date of about 1,900 

calendar years BP. 

Tufa re-exposed to lake water, either by a rise 

in lake level or by removal of the surrounding lake 

sediment, may acquire additional calcium carbonate derived from lake water. In addition, areas such 

as Needles Rocks may have experienced continued 

discharge of calcium-bearing waters into the bases 

of the tufa mounds. This younger calcium carbonate may fill preexisting pore spaces in the tufa 

or add calcium carbonate to the outside of a tufa. 

Many of the bases of tufa mounds that surround 

Pyramid Lake have been cemented with younger 

tufa (Figs. 9, 27), as indicated by the addition of a 

girdle of calcium carbonate (Figs. 20, 28), whos~ 

upper limit is at the elevation of the Mud La~e Sill. 

Existing data indicate that the level of Pyramid Lake 

often did not exceed the Mud Lake Sill elevation 

(1, 177-1, 183 m) during the past 8,000 years (Benson and others, 2002), suggesting that cementation 

of the old tufa mounds occurred during that time 

interval. 

Calcium carbonate continues to precipitate 

from Pyramid Lake's mixed layer. The mixed layer 

is the volume of warm water that lies above the 

thermocline (the water layer that separates a warm 

upper water layer from a cold bottom water layer 

in a lake) during the warm season. The carbonate 

(aragonite) makes up 10 to 15 weight percent of 

Pyramid Lake's sediment (Benson et al., 2002). 

Figure 27. Broken tufa mound at Dog Head Rock showing tubes 

and surrounding tufa that have been thoroughly cemented with 

younger calcium carbonate. 
CONCLUSIONS 

Many of the spectacular tufa deposits that surround Pyramid Lake were formed when the climate 

was much wetter and Pyramid Lake was joined 

to lakes in nearby basins. At that time (26,000 

to 13,000 years ago) many calcium-rich springs 

discharged from the lake bottom. The calcium in 

the springs combined with carbonate in the lake 

water to form large tufa mounds. In addition, many 

other reef-like tufa deposits formed on rocky headland areas when the level of Pyramid Lake was kept 

relatively constant during overflow to adjacent lake 

basins. 

Conclusions 13 

The elevations and ages of the tufa allow the 

construction of a lake-level envelope for the last 

35,000 years. The data indicate that the lake in the 

Pyramid Lake subbasin rose sharply about 26,000 

years ago and was maintained at about 1,265 m 

from 25,000 to 18,000 years ago by overflow to the 

Carson Desert. After a brief fall to less than 1,250 

m, Lake Lahontan rose rapidly to its highstand 

(1,335 m) about 15,000 years ago and then fell rapidly about 14,000 years ago. 

(Footnotes) 

1 Elevations in this paper are referenced to North American Datum 83 

(NAD 83). 

Figure 28. Tufa mound at the Needles Rocks site, whose base has 

been heavily cemented with younger calcium carbonate. This 

girdle of cement probably formed over the past 10,000 years when 

the level of Pyramid Lake rarely exceeded its overflow level to the 

Winnemucca Lake subbasin. 
14 The Tufas of Pyramid Lake, Nevada 

REFERENCES 

Benson, L.V., 1994, Carbonate deposition, Pyramid Lake 

subbasin, Nevada: 1. Sequence of formation and elevational 

distribution of carbonate deposits (tufas): Palaeogeography, 

Palaeoclimatology, Palaeoecology, vol. 109, p. 55-87. 

Benson, L.V., Kashgarian M., and Rubin, M., 1995, Carbonate 

deposition, Pyramid Lake subbasin, Nevada: 2. Lake levels 

and polar jet stream positions reconstructed from radiocarbon ages and elevations of carbonate deposits (tufas): 

Palaeogeography, Palaeoclimatology, Palaeoecology, vol. 

117,p.1-30. 

Benson, L., Kashgarian, M., Rye, R., Lund, S., Paillet, F., 

Smoot, J., Kester, C., Mensing, S., Meko, D., and Lindstrom, S., 2002, Holocene multidecadal and multicentennial 

droughts affecting northern California and Nevada: Quaternary Science Reviews vol. 21, p. 659-682. 

Fremont, J. C., 1845, Report of the Exploring Expedition to 

the Rocky Mountains in the Year 1843 and to Oregon and 

North California in the Years 1843-'44: Washington D.C. 

Kempe, S., Kazmierczak, J., Landmann, G., Konuk, T., 

Reimer, A., and Lipp, A., 1991, Largest known microbialites discovered in Lake Van, Turkey: Nature, vol. 349, p. 

605-608. 

Russell, I. C., 1885, Geological History of Lake Lahontan, a 

Quaternary Lake of Northwestern Nevada: U.S. Geological 

Survey Monograph 11, 287 pp. 

Shearman, K. J., McGugan, A., Stein, C. and Smith, A. J., 

1989, Ikaite CaC03

.6H20, precusor of the thinolites in Quaternary tufas and tufa mounds of the Lahontan and Mono 

Lake Basins, western United States: Geology Society of 

America Bulletin, vol. 101, 913-917. 

Voelker, A. H., Sarnthein, M., Grootes, P.M., Erlenkeuser, H., 

Laj, C., Mazaud, A., Nadeau, M., and Schleicher, M., 1998, 

Correlation of marine 14C ages from the Nordic seas with 

the GISP2 isotope record: implications for 14C calibration 

beyond 25 ka BP.: Radiocarbon, vol. 40, p. 517-534.