114°58’ W 114°57’ W 114°56’ W

38°43’ N

38°44’ N

38°45’ N

1 km

DU

D

D

D

D

D

U

U

U

U

U

Q

Q

Q

K

K

Ess

K-Pspb

K-PspbP-Espc

P-Espc

EspdEspd

Espe

Espe

Q

K-Pspb

E-Ogr

Ninemile Fau lt

Blue Sprin

g Fa

ult

D U

Garrett Ranch

Quaternary

Stinking Spring

E-Ogr

Q

Ess

K-Pspb

P-Espc

Espd

Espe

Kspa

LEGEND

K

Paleocene

Eocene

Oligocenevolcanics

Conglomerate

Members E-F

Member D

Member C

Member B

Member A

SHEE

P PA

SS F

M.

PzPALEOZOIC Paleozoicundifferentiated

Pz

Pz

Pz

Pz

N

B

Q

Q

Met.

Met.Trb

Trb

Tg

Tg

Tg

Pzg

Tr Pg

Mzg

Mzg

10 km

118°0’ W 117°40’ W

35°30’ W

35°20’ WMet.

Pzg

Mzg

Tr Pg

Q

Trb

Tg

Metamorphic Rx

Garlock Fm.

Mesozoic granite

Permo-Triassicplutonics

Goler Fm.

Ricardo Fm.

Quaternary

Paleocene

Miocene

TRIASSICPERMIAN

PALEOZOIC

LEGEND

N

A

The Basin and Range Province of the western United States is one of the premier examples of diffuse continental extension in the world. Esti-mates of extension across the Basin and Range during the Cenozoic range from 200% province-wide to locally as great as 400%. However, crustal thicknesses across this region, as derived from a variety of geo-physical methods, are remarkably uniform and, at ~35 km thick, are similar to global averages. Reconciling large-magnitude crustal exten-sion with observed crustal thicknesses is difficult without calling on one of three possible alternatives: (1) an Andean-plateau crustal thickness of ~60 km at the termination of the Sevier Orogeny and prior to exten-sion; (2) substantial addition of material to the crust by syn-extensional magmatism or (3) mobilization and redistribution of fluid lower crust during extension. Quantitative paleoelevation histories can help dis-criminate between these competing mechanisms for widespread Ceno-zoic extension. New estimates of pre-extensional paleoelevations for the northern and central Basin and Range are presented using clumped isotope (Δ47) thermometry of lacustrine carbonates that suggest modest (~2-3 km) pre-extensional elevations for the northern Basin and Range and quite low (< 1 km) elevations for the southern Basin and Range. These paleoelevations are incompatible with mass balance considerations based on the observed magnitude of crustal extension and modern crustal thicknesses, and imply that crustal mass was added to the Basin and Range during extension, either from magma-tism or crustal flow.

A Paleoelevation History of the Basin and Range and Its Relation to Cenozoic Extensional TectonismNathan A. Niemi

CIRES Sabbatical Fellow and University of Michigan

Abstract

Background and Methods

Discussion

Acknowledgements

Conclusions

Much of this work formed the basis of the PhD dissertation of Alex Lechler at the University of Michigan, and he is acknowledged for providing many of the figures presernted here. Discus-sions and collaborations with Kacey Lohmann, Mike Hren, Brice Lacroix, and many others have helped to improve this work. Funding for this research was provided by the University of Michigan, a Sabbatical Fellowship from CIRES and a CAREER grant from the National Science Foundation.

Eocene Paleoelevations Miocene Paleoelevations

Goler

SP

ColoradoPlateau

Sierra

Nevadapaleo-Pacific

Ocean

60 Ma

Modern

ColoradoPlateau

SP

Goler

Baja CA AZ

NV UT

CONM

CA AZ

NVUT

CONM

Sierra

Nevada

Figure5.2A

Figure5.2B

-60 -40 -20 200-2.5

-2.0

-1.5

-1.0

-0.5

0.0 Heated GasEquilibrated CO2

DV0804 - Marble Canyon pisolitesDV0811 - Bat Mountain limestone

SS0810 - Bena micriteAV0807 - Rocks of Pavits Spring

Carrara marble

∆ 47(‰

)

δ47(‰)

15 20 25 30 35 40 45

10

12

14

16

18

20

22

Age

(Ma)

Δ47 Temperature (°C)

Marble Canyonpisolites

(DV0804)

Bena micrite(SS0810)

Bat Mountainlimestone(DV0811)

Rocks of Pavits Spring

(AV0807)

Ghosh et al. (2006a)Dennis et al. (2011)

30 35 40 45 50 55 60 650

20

40

60

80

100

120

140

160

180

200

−500

−400

−300

−200

−100

0

100

200

300

400

500ρmantle = 3.4 g/cm3

ρmantle = 3.3 g/cm3

ρcrust = 2.7 g/cm3

Modern CBR

30 35 40 45 50 55 60 650

20

40

60

80

100

120

140

160

180

200

−500

−400

−300

−200

−100

0

100

200

300

400

500ρmantle =

3.4 g/cm3

ρmantle = 3.3 g/cm3

ρcrust = 2.75 g/cm3

Modern CBR

30 35 40 45 50 55 60 650

20

40

60

80

100

120

140

160

180

200

Crustal Thickness (km)

Lith

osph

eric

Man

tle T

hick

ness

(km

)

−500

−400

−300

−200

−100

0

100

200

300

400

500

ρmantle = 3.4 g/cm3

ρmantle = 3.3 g/cm3

ρcrust = 2.8 g/cm3

Elevation difference relative to m

odern (m)

Modern CBR

Hwy 95 Tps

TpsPz

Pz

Pz

Pz

Pz

pC4 km

116°20’ 116°17’

36°4

0’36

°37’

Tps

mid-MioceneRocks of Pavits

Spring Fm.

Precambrian

pC

5 km

36°1

9’30

’’N36

°22’

30’’N

116°33’N 116°30’N

Tby

Tbm

Tbm

TbmTbm

TtcTtc

Pz

Pz

Pz

Q

QQ

Q

Tbmmid-MioceneBat Mountain

Fm.

Paleozoic

TtcOligo-MioceneTitus Canyon

Fm.

TbyPliocene

basalt

Bat Mountain Amargosa Valley

TuTu

36°3

9.22

’N

500 m

Pz

Pz

Pz

Pz

Pz

Pz

Pz

Pz

Tu

Tu

Tu

Tu

Tu

Tu

Tu

Tu

Tp

Tp Tp

Tp

Tp

Tp

Tp

Tn

Tn

Tn

Tn

TnTn

Tn

To

To

To

To

To

ToTo

Q

Q

Q

Q

Q

Q

Entrance Narrows

117°17.79’W

36°3

8.95

’N

117°17.45’W

36°3

8.68

’N

Tnmid-to-lateMiocene

Navadu Fm.

Quaternary

Tu

early-to-midMiocene

Ubehebe Fm.

Tpmid-MiocenePanuga Fm.

ToPlioceneNova Fm.

Q Pz

C D EMarble Canyon

118°W 116°W117°W119°W

35°N

36°N

37°N

100 km

Fig. 3C

Fig. 3E

Fig. 3F

Fig. 3G

A

SS

DV AV

1 km

Tbg

Tbg

Tbg

Mg

Mg

Tw

Tw

Tw

Tos

Tos

Trm

Trm

TcTkr

Q

Q

QQ

D

D

D

U

U

U

35°2

5’N

35°2

3’N

118°47’30”W 118°45’W

Mg

Tw

ms

ms

Quaternary

Kern River Fm.

Q

Tkr

TcChanac Fm.

TbgBena gravel

TwWalker Fm.

TosOlcese sand

TrmRound Mtn.

silt

Mggranite

msmetasediments

Mesozoic

EoceneOligocene

Miocene

Pliocene

QB Cottonwood Creek

Fan

Paralic

ParalicBen

a G

rave

l

200 mSS0810

COTTONWOOD CREEK

SOUTHERN SIERRAA *3.2 Ma

*12.1 Ma

Pd

Nav

adu

Fm.

Pan

uga

Fm.

Ube

hebe

Fm

. *19.6 Ma*20.4 Ma

*6.2 Ma

DV0804

MARBLECANYON

*15.7 Ma

B

I

*13.5 Ma

*22.6 Ma

*24.7 Ma (ktb 27 Ma)

Dl

*21.2 Ma

ktb 12.8 Ma

ktb 13.5 Ma

Dl

*15.9 Ma

*26.0 Ma

*14.6 Ma

Roc

ks o

f Win

api W

ash

Roc

ks o

f Pav

is

Spr

ing

Allu

vium

Bat

Mou

ntai

n Fm

.A

mar

gosa

Val

ley

Fm.

DV0804DV0811

AV0807

BATMOUNTAIN

AMARGOSAVALLEY

Kel

ley’

s W

ell

Lim

esto

ne

DEATH VALLEY REGION

Geologic setting of Sheep Pass and Goler Formations carbonate sample locations. (A) Geologic map of the El Paso Mountains of southeastern California, modified from Cox [1982]. The Paleo-cene Goler Formation unconformably overlies metamorphic rocks of the Paleozoic Garlock For-mation and Mesozoic plutonic rocks associated with the onset of regional Sierra Nevada arc mag-matism and is unconformably overlain by Miocene Ricardo Formation volcanics. Red star marks location of Goler Formation Member 4a micritic carbonate sample. (B) Detailed geology of Sheep Pass Canyon, southern Egan Range, Nevada where the type section of the late Cretaceous-Eo-cene Sheep Pass Formation is exposed [modified from Druschke et al., 2009b]. Yellow stars mark Sheep Pass carbonate sample locations. Both lacustrine carbonate and fossil mollusc shells were collected from the same location within Member B (K-Pspb).

Geologic Setting

Study Area

Clumped Isotope Thermometry

Geologic Setting

Sampled Localities

Sampled Localities

Paleotemperature Results from Clumped-Isotope ThermometryPaleotemperature Results from Clumped-Isotope Thermometry

Geologic setting of sampled Miocene localities in the Sierra Nevada and Death Valley region. (A) Hillshade map of the southern Sierra Nevada-Death Valley region with extents of Cottonwood Creek (B), Marble Canyon (C), Bat Mountain (D), and Amargosa Valley (E) simplified geologic maps. Map extents are outlined and color-coded by sample localities, as shown in stratigraphic columns (below). Inset shows location and extent of hillshade map. SS = southern Sierra Nevada; DV = Death Valley; AV = Amargosa Valley. (B) Simplified geologic map of the Cottonwood Creek area of the southern Sierra Nevada where the peralic facies of the Bena Gravels were sampled (red star; modified from Bartow [1981]). (C) Simplified geologic map of the Marble Canyon area of the Cottonwood Mountains (modified from Snow and Lux [1999]) with sample location of Ubehebe Formation pisolites marked by blue star. (D) Simplified geologic map of the Bat Mountain area of the Funeral Mountains (modified from Fridrich et al. [2008]), where the Kelley‘s Well Limestone member of the Bat Mountain Formation was sampled (light blue star). (E) Simplified geologic map of the Amargosa Valley area where the Rocks of Pavits Spring were sampled (purple star; simpli-fied from Burchfiel [1966]). Thick, black lines on geologic maps mark mapped surface faults.

(A) Stratigraphic column for Bena Gravels which outcrop in the southern Sierra Nevada (Cotton-wood Creek) [Bartow and McDougall, 1984] (B) Stratigraphic columns for sampled Neogene sedi-mentary basins in the Death Valley region with marker beds and associated radiometric ages labeled (simplified from Fridrich and Thompson [2011] and references therein). 200 m strati-graphic scale bar applicable to both (A) and (B).

Age- Δ47 temperature plot for Bena Gravels and Death Valley area carbonate samples. Tempera-tures are plotted for Δ47-temperature calibrations of Ghosh et al. [2006a; circles] and Dennis et al. [2011; squares]. Samples are color-coded and labeled for clarification. Temperature differences between Bena micrite from the Sierra Nevada and samples in Death Valley indicate that the Death Valley region was not colder than the sea-level samples from the Sierra Nevada, suggesting that the Death Valley region was at low elevations prior to the onset of extension in middle-late Miocene time.

Early Cenozoic paleotopography and paleogeography of the western U.S. Cordillera with ret-rodeformed state boundaries. Locations of reference physiographic provinces (gray polygons) from McQuarrie and Wernicke [2005]. Paleotopographic contours and paleodrainages for the southern Sierra Nevada-Death Valley domain and ‗Nevadaplano‘ region are based on the re-sults of this and published studies [Gregory-Wodzicki, 1004 1997; Wolfe et al., 1998; Cassel et al., 2009a; Lechler and Niemi, 2011b]. Remaining contours and paleodrainages compiled from1006 various sources (Sierra Nevada: Mulch et al. [2006]; Cassel et al. [2009b]; Hren et al. [2010]; Cecil et al. [2010]; Henry et al. [2012]; southern Basin and Range: Abbott and Smith [1989]; Howard [2000]; Wernicke [2011]; Sevier orogen: Henry [2008]; Fan and Dettman [2009]). SN =Sierra Nevada, SP = Sheep Pass, DV = Death Valley.

Isostatic calculations of central Basin and Range (CBR) (paleo)elevations following the method of Lachenbruch and Morgan [1990] and Schulte-Pel-kum et al. [2011]. Elevationcalculations are presented for crust = 2.7, 2.75, and 2.8 g/cm3 and mantle (mantle lithosphere) = 3.3 and 3.4 g/cm3. Colorbar shows calculated elevation values relative to modern mean CBR elevations of 1 km; the – 500 to 500 m range equates to pa-leoelevations of 500 – 1500 m, which is the constrained paleoelevation range for the Middle Miocene Death Valley area based on carbonate Δ47 analysis. Dashed lines show maxi-mum crustal thicknesses permitted for ~ 1500 m paleoelevations (heavy, black lines and boxes for density combinations that produce total litho-spheric thickness comparable to modern CBR estimates [> 100 km; Schulte-Pelkum et al.,2011], gray lines and boxes for thicknesses that do not match modern observations).

Map of sample locations. Upper map shows carbonate sample locations (stars) in modern geographic coordinates with major physiographic provinces of the western US shown in gray. Inset map of the continental US indicates map extent. Lower map shows sample site locations in their Paleocene paleogeographic positions prior to Tertiary Basin and Range extension. Pa-leocene sample locations and paleogeography of retrodeformed state boundaries and physio-graphic provinces are based on palinspastic reconstructions of McQuarrie and Wernicke (2005). SP = Sheep Pass Formation; Goler = Goler Formation.

Simplified stratigraphic columns (Goler Fm. - Cox, 1982; Sheep Pass - Fouch, 1979; Drus-chke et al., 2009b) are included to provide stratigraphic correlation of the Goler (red lines) and Sheep Pass (blue lines) Forma-tions. Dashed lines indicate approximate cor-relations. Stars mark approximate stratigraph-ic position of analyzed carbonate samples. Sampled molluscs from Sheep Pass Member B also shown. North American Land Mammal Age (NALMA) assignments and age uncer-tainties are based on Sheep Pass molluscan biostratigraphy (Good, 1987) and radiometric dating (Druschke et al., 2009b) and Goler For-mation biostratigraphy (e.g. Lofgren et al., 2008) and magnetostratigraphy (Albright et al., 2009). NALMA abbreviations: Puer. = Puercan, Torr. = Torrejonian, Tiff. = Tiffanian, Clark. = Clarkforkian, Was. = Wasatchian, Brdg. = Bridgerian, Uint. = Uintan.

45

EOC

ENE

PALE

OC

ENE

K

NALMA

Puer.

Torr.

Tiff.

Clark.

Was.

Brdg.

Uint.

65

45

50

55

60

AGE(Ma)

250

m

E-F

A

B

C

D

1000

m

StinkingSpringscong.

1

2

3a

4a

3b

3c

4b

4c4d

GO

LER

Fm

. Mem

ber

81.3 ± 3.7 Ma

66.1 ± 5.4 Ma

37.7 ± 0.6 Ma

SHEE

P PA

SS F

m. M

embe

r

40 35 30 25 20 15T (°C)

45

δ18OPDB

-0.5 0 0.5 1.0 1.5

GolerSheep Pass

*Zachos et al., 2001

shells

Carbonate clumped isotope temperature record. Age-temperature plot for Goler and Sheep Pass carbonate samples. Dashed gray line marks average carbonate clumped isotope temperature for Sheep Pass Formation Members B and E (~ 23.5ºC). Zachos et al. (2001) marine δ18O record is shown for reference. Temperature difference between Sheep Pass Formation and presumed Pa-leocene sea-level temperatures at that time suggest that the paleoelevation of the Sheep Pass Formation was not significantly different from its modern elevation. This implies that there was not significant topographic change in concert with large-magnitude extension of the northern Basin and Range.

Heated gas line and isotopo-logue data. δ47 versus Δ47 for Goler and Sheep Pass carbon-ate samples, the Carrara marble interlab carbonate stan-dard, and heated CO2 gases.See text for discussion of heated gas line. Linear regres-sion of heated gas isotopo-logue values includes analyses of heated CO2 gases with δ47 values ranging from -54 to +10‰.Temperature values for carbonate samples are deter-mined by normalizing mea-sured Δ47 values using stochas-tic heated gas compositions at equal δ47 values.analytical results and calculat-ed temperatures.

Clumped isotope thermometry is based on the temperature dependence of the “clumping” of rare heavy isotopes in isotopologues. For paleoelevation studies, the isotopologue of mass 47 of CO3 in calcium carbonate is frequently used to measure the formation temperature of carbonate, a ubiquitous geo-logic material in lakes, soils, and other archives. The occurrence of this par-ticular isotopologue can be used to infer paleo-surface temperatures.

This preliminary study of Basin and Range paleoelevations from the Paleocene, just at the end of the compressional Sevier Orogeny, and from the Miocene, just prior to the onset of Basin and Range extension, suggests that paleoelevations of the Basin and Range are similar to observed modern elevations, despite >200% extension. These results suggest that crustal extension and thinning must be countered by another process that adds material to the crust to compen-sate for extensional strain. Lower crustal flow and magmatic addition are both possible mechanisms to accomplish this. Further work is required to discrimi-nate between these two possibilities.

Paleocene Shoreline

1000 m

1000

m

2000 m

2000

m

3000 m

enilerohS enecoelaP

LEGENDPaleogene basin

1000 m

1000 m

Constrained Contour

Inferred Contour Known paleodrainage

Inferred paleodrainage

‘Nevadaplano’

Normal fault

ColoradoPlateau

Baja

SN

SP

Goler

DV