U.S. Department of the Interior

U.S. Geological Survey

Professional Paper 1776-C

Studies by the U.S. Geological Survey in Alaska, 2008–2009

Depositional Setting and Geochemistry of Phosphorites 

and Metalliferous Black Shales in the CarboniferousPermian Lisburne Group, Northern Alaska
Cover photograph: Photomicrograph of phosphatic ooids and peloids in carbonate cement.
Studies by the U.S. Geological Survey in Alaska, 2008–2009

Depositional Setting and Geochemistry of Phosphorites 

and Metalliferous Black Shales in the CarboniferousPermian Lisburne Group, Northern Alaska

By Julie A. Dumoulin, John F. Slack, Michael T. Whalen, and Anita G. Harris

Professional Paper 1776-C

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2011

This report and any updates to it are available online at:

http://pubs.usgs.gov/pp/1776/c/

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Suggested Citation

Dumoulin, J.A., Slack, J.F., Whalen, M.T., and Harris, A.G., 2011, Depositional setting and geochemistry of phosphorites and metalliferous black shales in the Carboniferous-Permian Lisburne Group, northern Alaska, Dumoulin, J.A., 

and Galloway, J.P., eds., Studies by the U.S. Geological Survey in Alaska, 2008–2009: U.S. Geological Survey Professional Paper 1776–C, 64 p.
Figures

1. Outcrop belt of the Lisburne Group in northern Alaska and location of 

 major phosphorite occurrences..........................................................................................................2

2. Palinspastic restoration of northern Alaska......................................................................................3

3. Stratigraphic nomenclature of the Mississippian part of the Lisburne Group in the 

 Kelly River Allochthon (KRA) and Endicott Mountains Allochthon (EMA)...................................4

4. Stratigraphic position of phosphorites in the Lisburne Group........................................................5

Contents

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

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

Geologic Framework .....................................................................................................................................2

Methods and Terminology............................................................................................................................4

Geographic and Stratigraphic Variation of Phosphorites.......................................................................7

EMA—Central and West-Central Brooks Range ............................................................................7

KRA—Western Brooks Range............................................................................................................8

Ikpikpuk Well—North Slope ...............................................................................................................8

Lithologic Features of Phosphorites and Associated Rocks..................................................................8

Phosphorites..........................................................................................................................................8

Black Shales........................................................................................................................................10

Carbonate Rocks and Chert .............................................................................................................10

Lithofacies Associations....................................................................................................................11

Less-Phosphatic Strata...............................................................................................................................11

Whole-Rock Geochemistry ........................................................................................................................11

Black Shales........................................................................................................................................11

Phosphorites........................................................................................................................................13

Discussion.....................................................................................................................................................14

Depositional Setting ...........................................................................................................................14

Evidence for Upwelling......................................................................................................................16

Carbon-Sulfur Relationships.............................................................................................................17

Element Trends and Mineralogical Residence..............................................................................18

Redox Conditions during Sedimentation.........................................................................................18

Depositional Models...........................................................................................................................19

Diagenetic Effects...............................................................................................................................20

Redox Conditions during Deposition of the Kuna Formation.......................................................21

Sources of Metal Concentrations in the Black Shales ................................................................21

Environmental Synthesis ...................................................................................................................22

Paleogeography..................................................................................................................................22

Acknowledgments.......................................................................................................................................24

References Cited..........................................................................................................................................24

Tables 1–3 .....................................................................................................................................................31

Appendix. Additonal Geochemical Data.................................................................................................55

iii
 5. Phosphorite and phosphate rock in the Lisburne Group..............................................................6

 6. Lithologic features of phosphorites and related rocks in the Lisburne Group..........................9

 7. Detailed stratigraphy of the phosphorite-bearing interval 

at Confusion and Skimo Creeks .....................................................................................................12

 8. Total organic carbon (Corg) versus S plot.......................................................................................13

 9. Binary trace-element plots ..............................................................................................................14

 10. Binary plots discriminating suboxic denitrifying depositional conditions...............................15

 11. Binary marine Mo versus Re plot ...................................................................................................15

 12. Shale-normalized REE plots showing representative data ........................................................16

 13. Binary P2O5 plots................................................................................................................................17

 14. Lithofacies and spectral gamma-ray response of the shale and 

phosphorite unit at Skimo Creek ....................................................................................................18

 15. Schematic reconstruction of lithofacies and water circulation during 

deposition of Lisburne Group phosphorites .................................................................................23

 16. Recent reconstructions of Mississippian paleogeography .......................................................23

Tables

1. Phosphorite localities in the Lisburne Group, northern Alaska..................................................32

2. Less-phosphatic localities in the Lisburne Group, northern Alaska..........................................40

3. Compositions of black shales, phosphorites, and phosphorite nodules

 from the Lisburne Group, northern Alaska.....................................................................................52

A1. Complete geochemical data from black shales and phosphorites 

 from the Lisburne Group, northern Alaska. ....................................................................................57

A2. Varimax normalized factor loadings for bulk compositions of 17 black shales 

 from the Lisburne Group, northern Alaska ....................................................................................64

A3. Varimax normalized factor loadings for bulk compositions of 24 phosphorites 

 from the Lisburne Group, northern Alaska ....................................................................................64

iv
Studies by the U.S. Geological Survey in Alaska, 2008–2009

Edited by Julie A. Dumoulin and John P. Galloway

U.S. Geological Survey Professional Paper 1776–C

Depositional Setting and Geochemistry of Phosphorites 

and Metalliferous Black Shales in the CarboniferousPermian Lisburne Group, Northern Alaska

By Julie A. Dumoulin1, John F. Slack2, Michael T. Whalen3, and Anita G. Harris4

Abstract 

Phosphatic rocks are distributed widely in the Lisburne 

Group, a mainly Carboniferous carbonate succession that 

occurs throughout northern Alaska. New sedimentologic, 

paleontologic, and geochemical data presented here constrain 

the geographic and stratigraphic extent of these strata and 

their depositional and paleogeographic settings. Our findings 

support models that propose very high oxygen contents of the 

Permo-Carboniferous atmosphere and oceans, and those that 

suggest enhanced phosphogenesis in iron-limited sediments; 

our data also have implications for Carboniferous paleogeography of the Arctic.

Lisburne Group phosphorites range from granular to 

nodular, are interbedded with black shale and lime mudstone 

rich in radiolarians and sponge spicules, and accumulated 

primarily in suboxic outer- to middle-ramp environments. 

Age constraints from conodonts, foraminifers, and goniatite 

cephalopods indicate that most are middle Late Mississippian 

(early Chesterian; early late Visean). Phosphorites form 2- to 

40-cm-thick beds of sand- to pebble-sized phosphatic peloids, 

coated grains, and (or) bioclasts cemented by carbonate, silica, 

or phosphate that occur through an interval ≤12 m thick. High 

gamma-ray response through this interval suggests strongly 

condensed facies related to sediment starvation and development of phosphatic hardgrounds. Phosphorite textures, such as 

unconformity-bounded coated grains, record multiple episodes 

of phosphogenesis and sedimentary reworking. Sharp bed 

bases and local grading indicate considerable redeposition of 

phosphatic material into deeper water by storms and (or) gravity flows.

Lisburne Group phosphorites contain up to 37 weight 

percent P2O5, 7.6 weight percent F, 1,030 ppm Y, 517 ppm 

La, and 166 ppm U. Shale-normalized rare earth element 

(REE) plots show uniformly large negative Ce anomalies 

1

U.S. Geological Survey, Anchorage, Alaska.

2

U.S. Geological Survey, Reston, Virginia.

3

University of Alaska, Fairbanks.

4

U.S. Geological Survey, Reston, Virginia (retired).

(avg. Ce/Ce*=0.11���  ±  0.03) that are interpreted to reflect phosphate deposition in seawater that was greatly depleted in Ce due 

to increased oxygenation of the atmosphere and oceans during 

the Carboniferous evolution of large vascular land plants.

Black shales within the phosphorite sections have up to 

20.2 weight percent Corg and are potential petroleum source 

rocks. Locally, these strata also are metalliferous, with up 

to 1,690 ppm Cr, 2,831 ppm V, 551 ppm Ni, 4,670 ppm Zn, 

312 ppm Cu, 43.5 ppm Ag, and 12.3 ppm Tl; concentrations 

of these metals covary broadly with Corg, suggesting coupled 

redox variations. Calculated marine fractions (MF) of Cr, V, 

and Mo, used to evaluate the paleoredox state of the bottom 

waters, show generally high CrMF/MoMF and VMF/MoMF ratios 

that indicate deposition of the black shales under suboxic 

denitrifying conditions; Re/Mo ratios also plot mainly within 

the suboxic field and support this interpretation. Predominantly seawater and biogenic sources are indicated for Cr, V, 

Mo, Zn, Cd, Ni, and Cu in the black shales, with an additional 

hydrothermal contribution inferred for Zn, Cd, Ag, and Tl in 

some samples.

Lisburne Group phosphorites formed in the Ikpikpuk 

Basin and along both sides of the mud- and chert-rich Kuna 

Basin, which hosts giant massive sulfide and barite deposits 

of the Red Dog district. Lisburne Group phosphatic strata 

are coeval with these deposits and formed in response to a 

nutrient-rich upwelling regime. Phosphate deposition occurred 

mainly in suboxic bottom waters based on data for paleoredox 

proxies (Cr, V, Mo, Re) within contemporaneous black shales. 

Recent global reconstructions are consistent with Carboniferous upwelling in northern Alaska, but differ in the type of 

upwelling expected (zonal versus meridional). Paleoenvironmental data suggest that meridional upwelling may better 

explain phosphorite deposition in the Lisburne Group.

Introduction

 Phosphatic rocks form a small but conspicuous and 

widespread part of the Lisburne Group, a chiefly Carboniferous carbonate-platform succession found throughout northern 

Alaska (fig. 1; Armstrong and Mamet, 1977, 1978; Dumoulin 
2 Depositional Setting and Geochemistry of Phosphorites and Metalliferous Black Shales, Northern Alaska

and Bird, 2001; Dumoulin and others, 2004). Lisburne Group 

phosphorites are of middle Late Mississippian (mainly early 

Chesterian) age and are interbedded with organic-rich black 

shale and lime mudstone; radiolarians and sponge spicules are 

common components of all three lithologies. The black shales 

are potential petroleum source rocks (Dumoulin and others, 

2008) and locally are metalliferous, with high concentrations 

of Cr, V, Ni, Zn, Cu, Ag, Se, and Tl (Dumoulin and others, 

2006b, 2006c). Phosphorites in the Lisburne Group formed 

at a time of great geologic activity in northern Alaska. They 

are coeval with the formation of world-class deposits of zinc 

and barite in the Red Dog district (Kelley and Jennings, 2004; 

fig. 1) and with the drowning of carbonate platforms across 

much of north-western and north-central Alaska (Dumoulin 

and others, 2004, 2008; Whalen and others, 2006).

Carboniferous phosphorites are uncommon worldwide 

(for example, Shields and others, 2000), and granular phosphorites that correlate precisely with those of the Lisburne 

Group have not been reported elsewhere. The purpose of this

paper is to present new sedimentological, paleontological, and 

geochemical data that allow us to define the geographic and 

stratigraphic extent and depositional setting of these temporally unusual phosphorites. Our findings have implications for 

oxygen levels of the Permo-Carboniferous atmosphere and 

oceans, support recent models of phosphogenesis in suboxic 

iron-limited sediments, and constrain paleogeographic reconstructions of the Arctic.

Geologic Framework

The mainly Carboniferous Lisburne Group crops out 

throughout the Brooks Range (fig. 1) and is found in the subsurface beneath much of northern Alaska and adjacent offshore 

areas, where locally it is as young as Permian. The Lisburne 

Group consists chiefly of carbonate rocks that were deposited 

in a range of shallow- and deep-water settings. Shallow water, 

as used here, implies peritidal to subtidal photic-zone settings; 

deep water refers to outer-ramp to basin environments (for 

example, Burchette and Wright, 1992; Wright and Burchette, 

1998). Facies patterns of the Lisburne Group reflect a complex 

late Paleozoic paleogeography that was rearranged by later 

tectonism. The unit was deposited on an uneven topography 

shaped by extensional and transpressional deformation that 

began in the Devonian and persisted into the Permian (Dumoulin and Bird, 2001; Dumoulin and others, 2004). Structural 

features that were active during Carboniferous time include the 

Ikpikpuk-Umiat Basin beneath the west-central North Slope 

De Long Mts.

Quad

Killik River

Misheguk Mt. Howard Pass

Brooks Range

Arctic Ocean

Chukchi Sea

Alaska

Ikpikpuk 

150o

165oW

162o 159o 156o 153o

69oN

68o

0 100 200

km

141o

Figure 1

Area of

Lisburne

Peninsula

Hanna

trough

Prudhoe

Bay

IkpikpukUmiat Basin

Red Dog

N P R A

Chandler Lake

1 2 3

4

5

13

6 7

8 9

10

LLD 12

11

D

Figure 1. Outcrop belt of the Lisburne Group (shaded) in northern Alaska (modified from Armstrong and Mamet, 1978) and location of major 

phosphorite occurrences, quadrangles, and localities mentioned in the text (see table 1 for additional data). D, Drenchwater deposit; LLD, 

Lawrence Livermore Laboratory drill holes; gray line, boundary of NPRA (National Petroleum Reserve–Alaska). See Mayfield and others 

(1988), Young (2004), and references therein for details of allochthon distribution; individual allochthons are imbricated internally and made 

up of plates and thrust sheets, some of which are named. Endicott Mountains Allochthon (EMA) occurs throughout the western and central 

Brooks Range; Kelly River Allochthon (KRA) is found chiefly west of 159°; Picnic Creek Allochthon (PCA) chiefly west of 155°; localities 

1–3 are in KRA, localities 4–12 occur in EMA, and locality 13 is in parautochthonous subsurface strata. Skimo and Tiglukpuk thrust sheets 

(Dumoulin and others, 2008) occur in the Chandler Lake quadrangle and are two of numerous imbricated thrust sheets that make up the EMA.
 Geologic Framework 3

and the Kuna Basin in the western Brooks Range (Bird, 2001; 

Young, 2004) as well as a number of other basins and intervening highs (see fig. 8 by Hubbard and others, 1987). Thrust and 

extensional faulting during the Mesozoic and Tertiary Brooks 

Range orogeny further complicated facies distribution of the 

Lisburne Group; we use the nomenclature of Young (2004) 

and Dumoulin and others (2008) for structural features such as 

allochthons that formed in this orogeny. 

The diverse facies of the Lisburne Group are part of a 

single, structurally dismembered depositional system (fig. 2). 

Deep-water facies of the Lisburne Group predominate in parts 

of the Endicott Mountains Allochthon (EMA) in the western 

Brooks Range and throughout the structurally higher Picnic 

Creek and Ipnavik River allochthons; shallow-water strata 

prevail elsewhere in the EMA and throughout most of the Kelly 

River Allochthon (KRA; Dumoulin and others, 2004). The 

Lisburne Group in the subsurface formed mainly in shallow 

water, but includes some deeper-water rocks (Dumoulin and 

Bird, 2001). Palinspastic models of Mayfield and others (1988) 

and Young (2004) imply that deep-water strata of the Lisburne 

Group accumulated in a sediment-starved, extensional basin 

about 200 km wide by 600 km long (Kuna Basin), which was 

bounded on the north and southwest (present-day coordinates) 

by extensive carbonate platforms. The platforms consist largely 

of shallow-water carbonate rocks, but include local tongues of 

deeper-water strata (Dumoulin and others, 2004; Whalen and 

Figure 2. Palinspastic restoration of northern Alaska, adapted from Young (2004); subsurface data from Dumoulin and Bird (2001). 

Lisburne Group phosphorites formed during late Meramecian-early Chesterian time along the margin of the Ikpikpuk-Umiat Basin and 

on both sides of the Kuna Basin, which encompasses all deeper water and deep-water facies shown in southern part of reconstruction; 

triangles indicate approximately coeval occurrences of less-phosphatic strata (1-6 weight percent P2O5) in the Lisburne. Other 

occurrences of less-phosphatic rocks in the Lisburne Group that likely are older (Osagean) or younger (Morrowan or younger) are not 

shown here but are listed in table 2 and are found, respectively, west of and mainly east of locality 8.

Palinspastic Restoration

of Northern Alaska

Earliest Chesterian Time

Arctic Slope parautochthon

Drenchwater

Red

Dog

Ikpikpuk - Umiat Basin

Itkilyariak

Akmalik

Nuka

Kuna

Basin

Kelly

Platform

(Kogruk)

Wolverine, Ivotuk, and related plates

of Endicott Mountains Allochthon

Drenchwater, Key Creek, and related

plates of Endicott Mountains Allochthon

Picnic Creek Allochthon

Kelly River Allochthon

Ipnavik River Allochthon

Nuka Ridge Allochthon

Lithofacies and Depositional Settings

Nonmarine to shallow-marine

siliciclastic strata

Shallow-water carbonate strata

Deeper water carbonate, shale,

and chert

Deep-water chert, lesser shale

and carbonate

200 km

* * *

13

** *

13

4 5 6+78 9 12

10+11 4 5 6+78 9 12

10+11

+

+ +

+

?

1

2 3

1 2 3
4 Depositional Setting and Geochemistry of Phosphorites and Metalliferous Black Shales, Northern Alaska

others, 2006). Facies patterns indicate that the southern margin 

of the main (northern) platform was not uniform, but changed 

from a gently sloping homoclinal ramp in the east to a distallysteepened margin along which locally abundant carbonate 

turbidites accumulated in the west (Dumoulin and others, 2004). 

Basins farther north in the subsurface beneath the Arctic coastal 

plain, such as the ~200 by 150 km Ikpikpuk-Umiat Basin (figs. 

1, 2), were filled with thick, rapidly deposited, chiefly shallowwater strata that include some deeper-water intervals (Dumoulin 

and Bird, 2001).

Strata deposited in the Kuna Basin (fig. 2) mainly are 

organic-rich, biosiliceous black shale and mudstone and lesser 

calcareous radiolarite and carbonate turbidites of the Kuna 

Formation and related units (Dumoulin and others, 2004). 

Geochemical, petrographic, and sedimentologic data indicate 

that black shales of the Kuna Formation accumulated under 

chiefly suboxic, denitrifying depositional conditions (Dumoulin and others, 2004; Slack and others, 2004a; this paper).

Following Patton and Matzko (1959), Trappe (1998), and 

Cook and Shergold (2005), we define phosphorites as rocks 

that contain ≥18 weight percent P2O5, and we use the term 

phosphate rock to refer to samples having 13–17 weight percent P2O5. Phosphorites in the Lisburne Group contain 18–37 

weight percent P2O5. They are most abundant in, and were 

first described from, the EMA (figs. 1, 2; Patton and Matzko, 

1959; Kelley and Mull, 1995; Kurtak and others, 1995; Whalen and others, 2006; Dumoulin and others, 2008). Similar 

phosphorites were recognized more recently in the KRA in the 

western Brooks Range and in the parautochthonous subsurface 

succession in the Ikpikpuk well (Dumoulin and Bird, 2001; 

Dumoulin and others, 2004, 2006b, 2006c) and also may occur 

in parautochthonous strata of the Lisburne Peninsula (Armstrong and Mamet, 1977). All of these phosphorites are of late 

Meramecian-early Chesterian age (fig. 3) and occur within a 

distinctive subunit of the Lisburne Group, typically ~3–35 m 

thick, which also contains black shale, characteristic carbonate 

lithologies (described below), and local chert (fig. 4).

Various formal and informal stratigraphic names have 

been applied to the phosphorite-bearing interval of the Lisburne Group in the western and central Brooks Range (fig. 3). 

Workers in the central Brooks Range have called these strata the 

lower Kiruktagiak member (Brosgé and Reiser, 1951), the black 

chert and shale member (Bowsher and Dutro, 1957; Patton and 

Matzko, 1959), the shale and phosphorite unit (in the Skimo 

thrust sheet of the EMA; Dumoulin and others, 2008), and the 

chert and phosphorite unit (in the Tiglukpuk thrust sheet of the 

EMA; Dumoulin and others, 2008); all of these are considered 

subunits of the Alapah Limestone. In the western Brooks Range, 

equivalent rocks have been referred to as the Tupik and Kuna 

Formations (Curtis and others, 1984, 1990), or are included in 

the Kogruk Formation (Dumoulin and others, 2004).

Less-phosphatic rocks (1–6 weight percent P2O5) occur 

more widely throughout the Lisburne Group. Some are coeval 

with the major episode of Lisburne phosphorite formation, but 

others are older (late Early Mississippian; Osagean) or younger 

(latest Mississippian-Middle Pennsylvanian; late early Chesterian-Morrowan). These less-phosphatic strata occur in the 

western and central Brooks Range in the EMA and KRA, and 

in the Picnic Creek Allochthon (PCA), and include phosphatic 

black shale in the Kuna Formation and phosphatic limestone in 

various units of the Lisburne Group (Slack and others, 2004a, 

2004c, 2004d; Dumoulin and others, 2006c). 

Methods and Terminology

We studied phosphatic rocks of the Lisburne Group as 

part of regional mineral and energy resource assessments by 

the U.S. Geological Survey (USGS) that were focused on the 

western Brooks Range (Red Dog area) and Chandler Lake 

quadrangle (fig. 1). Phosphatic strata in the Lisburne Group 

were investigated and sampled at 54 outcrop localities in 

the west, west-central, and central Brooks Range, and also 

were examined in cuttings from the Lisburne and Ikpikpuk 

wells and in drill cores from the Red Dog district (figs. 1, 2; 

tables 1, 2; note that tables 1–3 are found at the back of this 

report). We visited and sampled most Lisburne Group phosphorites reported in the literature and discovered several new 

occurrences during the course of our studies. Sections were 

measured through the phosphorite-bearing interval of the 

Mississippian

Osagean Meramecian Chesterian

Lower Upper

K R A

E M A

West Central

Kogruk Fm.

Kuna Fm.

Tupik

Fm.

Kuna

Fm.

Utukok Fm. Wachsmuth

 Lms.

Alapah

 Lms.

Figure 3

Figure 3. Stratigraphic nomenclature of the Mississippian part 

of the Lisburne Group in the Kelly River Allochthon (KRA) and 

Endicott Mountains Allochthon (EMA). Dashed lines indicate 

approximate age range (late Meramecian-early Chesterian) 

of phosphorite interval, based on conodonts, foraminifers, and 

goniatite cephalopods; where most tightly dated, phosphorites are 

early Chesterian (shaded interval). 
 Methods and Terminology 5

Lisburne Group at all localities where strata were sufficiently 

well exposed (see table 1 for details). Age control for the 

sections comes mainly from conodonts, augmented by data 

from foraminifers and goniatite cephalopods (Dumoulin and 

Bird, 2001; Dover and others, 2004; Dumoulin and others, 

2006a, 2008 and references therein). Petrographic interpretations are based on examination of 389 thin sections (tables 1, 

2). Carbonate rocks are classified according to the scheme of 

Dunham (1962), as modified by Embry and Klovan (1972). 

We use the term “supportstone” to encompass packstone and 

grainstone. 

Phosphorites in the Lisburne Group have two main 

forms: (1) Granular phosphorites are grain-supported lenses 

or beds made up of >90 volume percent phosphatic grains, 

which are mostly sand-sized and vary in type and texture 

(fig. 5A,B). (2) Phosphorite nodules are round to ovoid and 

range from a few millimeters to more than 15 cm long; most 

are made up of sand-sized phosphatic grains in a matrix of 

carbonate or silica cement, but some nodules consist mainly 

of fine-grained phosphate and lesser carbonate and (or) 

siliceous material (fig. 5C). Phosphate rocks are similar to 

granular phosphorites in outcrop and thin section texture, 

but contain more nonphosphatic material—mainly carbonate 

Figure 4. Stratigraphic position of phosphorites in the Lisburne Group; section locations shown in figure 1. Lower part of sections 2 

and 3 are modified from Armstrong (1970).

Ikpikpuk Well

Lisburne Gp.

continues

P

C

M-C

C

M

C

M

Siksikpuk 

Fm.

Siksikpuk 

Fm.

Kelly River

Plate

Amphitheatre

Plate

26/3

Lisburne Gp.

(Kogruk Fm.)

continues

14/7.7

Kelly River Allochthon Parautochthon

Utukok Fm.

(Lisburne Gp.)

Endicott Gp.

Endicott Mountains Allochthon

O

M

C

P 

200 m section not shown

Skimo Creek

Siksikpuk 

Fm.

Siksikpuk 

Fm.

Siksikpuk 

Fm.

Siksikpuk 

Fm.

22/8 + 26/20

13.7/4.5 32/17

Shainin Lake

Holocene

erosion

surface

O-M

O

K

M

C

Kayak Sh.

150 m section not shown

Holocene

erosion

surface

Base not

exposed

Mt. Bupto

Lisburne

Ridge Ivotuk Hills Lisburne

Well

M

O-M

O

K-O

M-C

M

O-M

C

M

O

M

O-M

Fault

Base not

exposed

Fault

Base not

exposed

C

2 5

3 4 6

7

11

12 

13 

EXPLANATION

Porous dolostone 

Organic-rich shale

 and phosphorite

Other rock types 

Covered interval 

MISSISSIPPIAN STAGES 

C Chesterian 

M Meramecian

O Osagean

K Kinderhookian

0

50

100

METERS

High metal v alues in shale

P2

O5 obser ved in ts

P2

O5 reported by Bowsher and D utro (1957)

Maximum wt % 2

O5 26/ 3 /C

*

+

P - PENNSYLVANIAN 

* *

org

-

-

-

-

P

Figure 4
6 Depositional Setting and Geochemistry of Phosphorites and Metalliferous Black Shales, Northern Alaska

cement, lime mud matrix, and calcareous and (or) silicified 

bioclasts (fig. 5D).

We obtained a spectral gamma-ray profile from the 

upper part of the Lisburne Group at Skimo Creek (loc. 11, 

fig. 1) using a Scintrex model 512 gamma-ray spectrometer 

that measures naturally occurring gamma-ray emissions 

(Dumoulin and others, 2008). This section was selected for 

profiling because it contains one of the thickest and most complete exposures of the phosphorite-bearing interval observed 

in this study, and because contacts with overlying and underlying subunits are well exposed. Measurements were taken 

every 0.5 m within the shale and phosphorite unit. The instrument provides total gamma-ray counts, as well as quantitative 

K (percent), U (ppm), and Th (ppm) concentrations.

Geochemical samples were selected to maximize geographic and lithologic coverage (fig. 1, table 1); we attempted to 

sample only fresh, unweathered rock but all samples analyzed 

for this study are from outcrop. At some localities with a range 

of phosphorite lithologies, several samples were taken to represent this range. Samples used for geochemical analysis were 

trimmed of weathered surfaces and veins and then pulverized in 

an alumina-ceramic mortar. All analyses were done at Activation Laboratories in Ancaster, Ontario. Major, selected trace, 

and rare earth elements (REE) were determined by inductively 

coupled plasma-mass spectrometry (ICP-MS) on rock powders 

fused with lithium metaborate/tetraborate in order to insure 

complete acid dissolution of minerals such as zircon, monazite, 

xenotime, and barite prior to analysis. Instrumental neutron 

activation analysis (INAA) was used for As, Sb, Sc, and Cr. 

Concentrations of Li, B, Ga, Co, Cd, Au, Pb, Mo, Re, Te, and Se 

were acquired by high-precision ICP-MS following a multi-acid 

digestion of powders. Analyses were made on duplicate samples 

Figure 5. Phosphorite and phosphate rock in the Lisburne Group. A, Granular phosphorite (21–26 weight percent P2O5) in EMA at Lisburne 

Ridge (loc. 5, fig. 1). B, Photomicrograph of bed shown in A contains phosphatic ooids and peloids in carbonate cement; phosphatic grain in 

lower left includes abundant white quartz silt. C, Photomicrograph of phosphorite nodule (4 cm maximum diameter; 31 weight percent P2O5) 

in KRA (loc. 1, fig. 1); it consists of finely intergrown phosphatic and lesser chalcedonic cement with abundant partly pyritized radiolarians 

(R) and sponge spicules. D, Photomicrograph of phosphate rock (14 weight percent P2O5) in KRA (loc. 3, fig. 1); it consists of phosphatic 

peloids and partly silicified calcareous bioclasts in a matrix of mud and carbonate cement; large shell (G) is a gastropod.

A B

C D

1 mm

Figure 5

0.3 mm

0.3 mm

R

G

l
 Geographic and Stratigraphic Variation of Phosphorites 7

and on 8–12 standards. Precision and accuracy for concentrations ≥100 times the minimum detection limit (MDL) generally 

were better than  ± 5-percent relative, and in many cases, such 

as for major elements, were better than  ± 1-percent relative. For 

concentrations approximately 10 times the MDL, precision and 

accuracy were about  ± 10–20-percent relative depending on 

the method used. Details of the various analytical methods are 

available online at www.actlabs.com.

Geographic and Stratigraphic Variation 

of Phosphorites

Phosphatic rocks in the Lisburne Group occur in a number of structural and geographic settings (tables 1, 2). The 

palinspastic models of Young (2004) and subsurface data of 

Dumoulin and Bird (2001) provide a basis for a reconstruction of North Alaskan paleogeography during Late Mississippian time (fig. 2). Lisburne Group phosphorites (P2O5 ≥18 

weight percent) and phosphate rock (P2O5 13–17 weight percent)—the focus of this paper—formed at least locally along 

the margin of the Ikpikpuk-Umiat Basin and along both 

sides of the mud-rich Kuna Basin. Roughly coeval occurrences of less-phosphatic rocks (P2O5 1–6 weight percent) 

occur in the Wolverine and Key Creek plates of the EMA, 

the PCA, and the KRA; these strata accumulated adjacent to 

the major phosphorites along both margins of the Kuna Basin 

and within the basin (fig. 2). Less-phosphatic rocks also are 

found in the slope and basin succession of the Kuna Formation of the Lisburne Group and in platformal successions 

that commonly contain glauconite. In contrast, glauconite is 

absent from virtually all intervals of phosphorite and phosphate rocks we studied in the Lisburne Group. 

EMA—Central and West-Central Brooks Range

Lisburne Group phosphorites in the EMA occur in a 

discontinuous belt that extends through the ChandlerLake, 

Killik River, and Howard Pass quadrangles for >250 km 

(figs. 1, 2, locs. 4–12; table 1). Phosphatic strata in this belt 

have many similarities, but differ from east to west in cumulative thickness and relative stratigraphic position (fig. 4). We 

examined phosphorites from 14 surface localities throughout 

this belt (table 1) and from drill cores of the Lisburne 1 well 

(loc. 7, fig. 1). Phosphorites also occur in cuttings from two 

boreholes drilled by Lawrence Livermore Laboratory(fig. 1; 

table 1; Brosgé and Armstrong, 1977). Occurrences of 

conodonts, foraminifers, and goniatite cephalopods indicate 

that all phosphorite strata in this belt are late Meramecianearly Chesterian, and where most tightly dated are early Chesterian (table 1; Dumoulin and others, 2006a, 2006c, 2008).

In the eastern part of the EMA phosphorite belt (from the 

central Killik River quadrangle eastward; locs. 8–12, figs. 1, 

2; table 1), the phosphatic interval occurs in the upper (but not 

uppermost) part of the Lisburne Group (fig. 4). The thickness 

of Lisburne strata overlying the phosphate zone increases to 

the east, from 18 m in the central Killik River quadrangle 

(loc. 8, fig. 1; C.G. Mull, written commun., 2005) to 60 m near 

Monotis Creek (loc. 9, fig. 1; Patton and Matzko, 1959) to 170 

m at Skimo Creek (loc. 11, fig. 1; Dumoulin and others, 2008). 

Granular phosphorites in the Lisburne Group are most 

abundant in the western half of the Chandler Lake quadrangle 

(locs. 9–11, fig. 1), where they occur chiefly in the Skimo 

and Tiglukpuk thrust sheets of Dumoulin and others (2008) 

and consist of 2- to 40-cm-thick beds of sand- to pebblesized phosphatic peloids, coated grains, and (or) bioclasts in 

a matrix of calcite, silica, or phosphate  ±  fluorite cement and 

(or) lime or phosphatic mud. Phosphorite nodules, typically a 

few millimeters to 2 cm in diameter, also occur at most localities. As many as 10 discrete granular phosphorite beds have 

been found in some outcrops; most have a lens-like form and 

cannot be traced laterally for more than a few hundred meters. 

Phosphorites are interbedded with organic-rich black shale and 

lime mudstone (Dumoulin and others, 2008), contain 18–37 

weight percent P2O5, and occur through an interval ≤12 m 

thick. Shale and limestone interbeds in this interval have as 

much as 10 weight percent P2O5 (Patton and Matzko, 1959). 

Sections as much as 6 m thick averaging 19–26 weight percent P2O5 have been documented at several localities (Patton 

and Matzko, 1959; Kurtak and others, 1995).

Where detailed studies have been made in the central 

Chandler Lake quadrangle, Lisburne phosphorites were found 

in several distinct thrust sheets in the EMA (Dumoulin and 

others, 2008). They occur at the same stratigraphic level in all 

sheets, based on fossil age control and sequence stratigraphic 

analysis, but differ in thickness and associated lithofacies. 

Phosphorite layers are thicker, more numerous, and associated with greater amounts of black shale in the Skimo thrust 

sheet than in the Tiglukpuk thrust sheet to the north. Coeval 

phosphorites also were reported from thrust sheets south of 

the Skimo sheet (Porter, 1966; Armstrong and Mamet, 1978) 

but little lithologic detail is available for these strata. Paleogeographic reconstructions and structural studies indicate 

that Lisburne strata in the Skimo thrust sheet accumulated in 

a more distal setting, ~12–17 km seaward of coeval strata in 

the Tiglukpuk sheet (Dumoulin and others, 2008); equivalent 

rocks in thrust sheets south of the Skimo sheet were deposited 

still further offshore, but precise lateral displacements for 

these thrust sheets have not yet been determined. 

The western part of the EMA phosphorite belt is in rocks 

of the Ivotuk plate (Young, 2004) and includes occurrences at 

Mount Bupto and Lisburne Ridge (fig. 5A,B) in the Howard 

Pass quadrangle, and in the Ivotuk Hills and Lisburne 1 well 

in the western Killik River quadrangle (locs. 4–7, figs. 1, 2, 4; 

table 1). The phosphorite interval here has similar lithofacies, 

P2O5 content, and associated rock types, but is thinner (generally ≤1–3 m thick) and occurs at or just below the top of the 

Lisburne Group. Granular phosphorites like those that crop out 

in the Ivotuk Hills (Kelley and Mull, 1995) also occur in the 

subsurface just to the east in the Lisburne 1 well (Dumoulin 

and Bird, 2002), which penetrated five imbricated thrust sheets 
8 Depositional Setting and Geochemistry of Phosphorites and Metalliferous Black Shales, Northern Alaska

made up mostly of the Lisburne Group (Cole and others, 

1997). We observed granular phosphorites in cuttings ~7–20 

m below the top of the Lisburne in four of the five thrust 

sheets (sheets 1, 2, 4, and 5).

KRA—Western Brooks Range

Lisburne Group phosphorites in the KRA are found 

mainly in the eastern De Long Mountains and western 

Misheguk Mountain quadrangles (locs. 1–3, figs. 1, 2; table 

1), where they crop out at scattered localities in the Wulik 

Peaks, Amphitheatre, and Kelly thrust plates (Dumoulin and 

others, 2004). Phosphatic rocks within this allochthon occur 

in a zone of organic-rich black shale ≤15 m thick at the top 

of the Lisburne Group (fig. 4) and consist of layers of ovoid 

phosphorite nodules as much as 15 cm long (26–31 weight 

percent P2O5; fig. 5C) and lenses, typically 10–30 cm thick, 

of phosphatic limestone grading to granular phosphate rock 

(2–14 weight percent P2O5; fig. 5D). Black shale at these 

localities has as much as 10 weight percent P2O5, chiefly as 

disseminated phosphatic peloids and small nodules. Nodules 

contain abundant and locally very well-preserved radiolarians 

(fig. 5C), as well as lesser sponge spicules and rare nautiloid(?) fragments. Chemical analyses and thin-section examinations (tables 1, A1) indicate that granular phosphatic strata 

in the KRA have more nonphosphatic grains (mostly calcareous bioclasts) than equivalent strata in the EMA. Conodonts 

from phosphatic limestone at several KRA localities are early 

Chesterian (Dumoulin and others, 2004, 2006a).

Ikpikpuk Well—North Slope

The Ikpikpuk well (loc. 13, figs. 1, 2; table 1) was drilled 

on the northwestern flank of the Ikpikpuk-Umiat Basin, a large 

complex sag initiated in Early Mississippian or Devonian time 

(Dumoulin and Bird, 2001). More than 1,000 m of parautochthonous Lisburne Group strata, ranging in age from Late Mississippian through Permian, were penetrated in this well. Cuttings through a 12-m-thick zone ~990 m below the top of the 

Lisburne Group (fig. 4; 14,600–650 ft depths) contain grains 

of calcite-cemented granular phosphorite, texturally identical 

to those seen elsewhere in the Lisburne, associated with dark 

mudstone, spiculite, and muddy skeletal packstone. Foraminifers indicate an age of late Meramecian-early Chesterian for 

these rocks (Dumoulin and Bird, 2001).

Lithologic Features of Phosphorites 

and Associated Rocks

Phosphorites 

Granular phosphorites in the Lisburne Group vary in 

composition and texture among localities and between (and 

within) individual beds at a single locality. Most are grainstones, packstones, or rudstones in which virtually all grains 

are phosphatic (fig. 6A–F). Rare beds contain <10 percent 

nonphosphatic grains, mainly calcareous lithic clasts or 

bioclasts. The phosphate grains typically are packed loosely 

and cemented by coarsely crystalline sparry calcite (less commonly, dolomite or silica), but some layers are packed tightly 

and contain little matrix or cement; these highly compacted 

samples generally are cemented by phosphate or fibrous 

chalcedony (fig. 6A,B,D). Lime or phosphatic mud forms the 

matrix in some samples, and patchy purple fluorite occurs 

locally. A few phosphorite layers are graded normally, whereas 

others show reverse grading, or coarse-tail grading (fig.6B,F). 

Bed bases typically are sharp. 

Phosphatic particles in the granular phosphorites mainly 

are peloids, coated grains, and bioclasts that range in size from 

very fine sand to pebbles (fig. 6B). Peloids (structureless phosphatic particles, see Föllmi, 1996) vary from round to elongate 

to irregular; most are internally featureless but some contain 

silt- to sand-sized fragments of quartz, carbonate, or organic 

material (fig. 5B). Many of the coated grains have rims made 

up of either one or a few different-colored phosphatic laminae, 

but some have thick rims with >10 laminae; color variation 

may reflect different amounts of organic material in the laminae (fig. 6B,D). Some coated grains contain internal discordances and appear to be unconformity-bounded coated grains 

as defined by Pufahl and Grimm (2003). Most coated-grain 

nuclei are phosphatic peloids, but quartz grains, possible lithic 

clasts, and bioclasts also were observed (fig. 6E). Phosphatic 

bioclasts chiefly are conodonts and ichthyoliths; phosphatized 

bioclasts are less common and include crinoid, bryozoan, and 

brachiopod fragments. Composite grains—aggregates of two 

or more peloids or coated grains—occur locally (fig. 6B,C).

Peloids are the dominant phosphatic particle in most 

Lisburne Group samples, but coated grains are unusually 

abundant (≥50 percent of all grains) at Lisburne Ridge (western EMA; loc. 5, fig. 1) and near the middle of the phosphatic 

section at Confusion Creek (eastern EMA; Skimo thrust sheet; 

loc. 10, fig. 1). Phosphatized bioclasts are a notable component at Tiglukpuk Creek (eastern EMA; Tiglukpuk thrust 

sheet; 7 km north of loc. 11, fig. 1). Composite grains are most 

common in the upper part of the phosphatic zone in the Confusion Creek and Skimo Creek sections (locs. 10 and 11, fig. 1). 

Complex textural variations occur locally at a microscopic scale in the granular phosphorites. Thin sections 

indicate that some phosphorite intervals, 1–7 cm thick, which 

appear homogeneous in outcrop, contain ≥4 distinct layers, 

3–10 mm thick (fig. 6F). These layers have erosional bases, 

different matrix compositions (including various proportions 

of lime and phosphatic mud and calcite, silica, phosphate, and 

fluorite cement), and different proportions of phosphatic particle types (some layers are dominated by coated grains, others 

by peloids). Layers also differ in average grain size and type of 

grading (normal, coarse-tail, or reverse). Boundaries between 

some layers appear to be truncation surfaces, are marked by 

burrows or borings and rare truncated grains, and may be 
 Lithologic Features of Phosphorites and Associated Rocks 9

Figure 6. Lithologic features of phosphorites and related rocks in the Lisburne 

Group; all samples are from EMA. A and F

are thin section scans; B-E and H are photomicrographs; G and I are outcrop views. 

A and B, Phosphorite (19 weight percent 

P2O5) from Monotis Creek (loc. 9, fig. 1), 

composed of a loosely packed layer with 

white silica cement above a tightly packed 

layer with phosphatic cement; B shows 

coarse-tail grading and variety of phosphatic peloids (P), coated grains (Co), and 

composite grains (CG). C, Large composite 

phosphatic grain (CG) made up of numerous smaller grains, Lisburne Ridge (loc. 5, 

fig. 1). D, Tightly packed phosphorite with 

phosphatic cement (37 weight percent 

P2O5), Killik River area (loc. 8, fig. 1); prominent grain left of center contains numerous radiolarians (dark spots) and several 

grains (UB) have internal discordances 

and appear to be unconformity bounded 

(Pufahl and Grimm, 2003). E, F, and I, Tiglukpuk Creek (7 km north of loc. 11, fig. 1); 

E, Phosphorite (21 weight percent P2O5) 

in which quartz grains and possible lithic 

clasts form nuclei for many phosphatic 

clasts. F, Complex phosphorite representing multiple episodes of reworking and 

redeposition; note the four distinct layers 

(that differ in composition, grain size, 

packing, and grading; the light layer near 

top is graded reversely) bounded by truncation surfaces that may be hardgrounds; 

phosphatic cement decreases upwards;

the small zone of coarser-grained material 

in the center of the photo likely is a burrow 

or boring I, A chert nodule with laminated 

(wood-grained) texture. G, Black shale 

interbedded with light-gray-weathering 

lime mudstone, Skimo Creek (loc. 11, fig. 1). 

H, Carbonate concretion with well-preserved radiolarian tests (replaced by pyrite 

and calcite) in a matrix of fine-grained 

carbonate, Akmagolik Creek (10 km east of 

loc. 11, fig. 1). 

A B

C

D

E

F

H

I

3 mm

G

CG

P

Co

UB

UB

CG

P

Co

UB

UB

0.5 mm

0.5 mm

0.1 mm

3 mm

1 mm

1 mm

Figure 6
10 Depositional Setting and Geochemistry of Phosphorites and Metalliferous Black Shales, Northern Alaska

hardgrounds (fig. 6F). Composite phosphorite intervals are 

especially abundant in the eastern EMA.

Phosphorite nodules occur in beds and lenses of granular phosphorite and are scattered within, or along, discrete 

horizons in black shale and lime mudstone. They are largest 

(3–>15 cm long) and most abundant at several localities in 

the KRA and also are notable at the tops of granular phosphorite beds at Skimo and Confusion Creeks. Some nodules 

have internal textures similar to those of granular phosphorites 

and consist of closely packed phosphatic peloids cemented 

by calcite or phosphate. Others are made mostly of massive 

phosphate, complexly intergrown with chalcedony or calcite, 

and may contain abundant bioclasts (chiefly radiolarians) and 

(or) minor siliciclastic or carbonate detritus (fig. 5C).

Radiolarians and lesser sponge spicules are important 

constituents of both granular and nodular phosphatic rocks in the 

Lisburne Group. Thin-section observations indicate that radiolarian tests, commonly coated with probable organic matter and (or) 

replaced by pyrite, occur in phosphatic nodules in the KRA (fig. 

5C) and in phosphatic peloids and both rims and cores of coated 

grains (fig. 6D) at numerous localities in the EMA (table 1).

Black Shales 

Fissile black shales (fig. 6G) are interbedded with phosphorites at virtually all known phosphorite localities in the 

EMA and KRA. Shales are mildly to moderately calcareous 

and organic-rich (1.34–20.2 weight percent Corg) and some 

are phosphatic (0.54–11.54 weight percent P2O5; 5 samples 

have >7 weight percent P2O5). Shale intervals are 0.1–5 m 

thick, laminated in thin section and outcrop, and generally 

lack evidence of bioturbation, although a few samples contain 

irregular concentrations of silt that could reflect some microbioturbation. Signs of floccule ripple bedding (Schieber and 

others, 2007) are absent. At Confusion Creek (loc. 10, fig. 1), 

shales contain 5–50 volume percent elongate (flattened?) clasts 

of carbonate and (or) phosphate; carbonate clasts (made mostly 

of micrite; 0.2–3mm long) and disseminated micrite and calcite 

silt increase upward through the section. Carbonate clasts were 

not seen in shales at other localities, but scattered, fine-grained 

carbonate is common; dolomite euhedra are notable in shale 

samples from Mount Bupto and Lisburne Ridge (locs. 4, 5, fig. 

1). Phosphatic peloids, ubiquitous in shale beds interbedded 

with phosphorites at all localities, are mostly ovoid to irregular 

and are 0.1–0.6mm in diameter. They typically are disseminated, but locally are concentrated into layers and lenses a few 

millimeters thick, making up 1–30 volume percent of most 

shale samples. Rare bioclasts in shale beds include phosphatic 

skeletal fragments, calcareous and siliceous spicules, radiolarians, ostracodes, and possible calcispheres.

Carbonate Rocks and Chert 

Lime mudstone is the main carbonate rock type interbedded with phosphorites in the eastern EMA (Chandler Lake 

quadrangle), whereas bioclastic supportstone predominates in 

the KRA. Carbonate rocks associated with phosphorite in the 

western EMA (Howard Pass and western Killik River quadrangles) are dolomitized extensively, but include protoliths ranging 

from bioclastic packstone to mudstone. Calcareous strata intercalated with phosphorite in the Ikpikpuk well also range from 

bioclastic (in part spiculitic) packstone to mudstone.

In the eastern EMA, lime mudstone to wackestone, intercalated with phosphorite, forms laterally continuous beds a few 

centimeters to >1.5 m thick (fig. 6G), as well as subordinate 

round to ellipsoidal concretions 0.1–1.3 m in maximum diameter 

(fig. 6H). Most beds are finely laminated, but a few appear partly 

bioturbated. Micritic clasts and phosphatic peloids, like those 

in the black-shale interbeds, occur locally, and many samples 

contain abundant radiolarians (fig. 6H) and (or) calcareous or 

siliceous sponge spicules. Goniatite cephalopods were found at 

several localities (Gordon, 1957; Dumoulin and others, 2008). 

Carbonate associated with phosphorite in the KRA is 

mainly thin- to medium-bedded bioclastic supportstone and 

lesser wacke-packstone in intervals 0.3–>1.0 m thick. Some 

beds contain abundant phosphatic grains (typically 10–30 

volume percent, locally as much as 80 volume percent), in 

places grading into granular phosphate rock. Bioclasts in these 

strata are brachiopod and pelmatozoan fragments with lesser 

ostracodes, gastropods, and coral debris (fig. 5D). 

Bored bioclasts are a notable component of carbonate 

beds in the phosphorite zone of the KRA and western EMA 

and a less common constituent of equivalent strata in the 

eastern EMA. Borings occur chiefly in brachiopod shells in 

supportstone and phosphatic limestone, are 10–40 μm in 

diameter, as much as 0.4 mm long, and of unknown origin; 

most borings are filled with dark, noncarbonate mud, but some 

contain phosphatic material.

Biofacies of conodont faunas from lime mudstones 

intercalated with phosphorites in the EMA and from phosphatic limestones in the KRA indicate that most assemblages 

accumulated as distal winnows into deeper-water settings 

(Dumoulin and others, 2006a, 2008). A radiolarian-rich carbonate concretion in the eastern EMA (loc. 9, fig. 1) contains 

a conodont assemblage characteristic of a deep-water, poorly 

oxygenated setting (table 1; Dumoulin and others, 2008).

Black to dark gray chert forms local, decimeter-thick concretions and lenses in phosphorite-bearing sections throughout 

the EMA. Many samples contain abundant sponge spicules and 

(or) radiolarians. In some occurrences, chert is complexly intergrown with, or partly to completely replaces, calcite or dolomite. 

Chert lenses in the western EMA retain well-preserved textures 

of skeletal packstone; bioclasts include pelmatozoans, bryozoans, 

brachiopods (locally bored), and nautiloids, as well as spicules 

and radiolarians. Several cherty layers in the eastern EMA are 

laminated concentrically (fig. 6I); different proportions of chert, 

organic material, and fine-grained carbonate define the laminae. 
 Whole-Rock Geochemistry 11

Lithofacies Associations

Granular phosphorites in the eastern EMA are interbedded with black shale and lime mudstone to wackestone. 

Coarsening-upward sequences, 0.5–1.5 m thick, of shale 

grading up into lime wackestone and capped by granular 

phosphorite or phosphate rock, occur at Confusion and Skimo 

Creeks (fig. 7). Sections in the western EMA and KRA contain 

dolostone and bioclastic supportstone, respectively, in place 

of lime mudstone, but are otherwise similar to those in the 

eastern EMA. Exact compositions of beds in the Ikpikpuk well 

are less certain, but detailed study of cuttings composited over 

10-ft intervals suggests similarities to lithofacies in the eastern 

EMA. Phosphorite nodules are most abundant near or at the 

tops of granular phosphorite layers; in the KRA, they also are 

notable in black shale layers. 

Less-Phosphatic Strata

Intervals within the Lisburne Group, mostly ≤2 m thick, 

that contain minor to moderate amounts of phosphate, but no 

true phosphorites, have been found at 50 outcrop and subsurface localities in the western and central Brooks Range (fig. 

2; table 2). These rocks typically contain ≤30 volume percent 

phosphatic grains visible in thin section, abundant phosphatic 

grains and (or) phosphatized bioclasts in conodont sample 

residues, and 1–6 weight percent P2O5 where chemical analyses are available. Most such strata appear to be coeval with the 

late Meramecian-early Chesterian Lisburne Group phosphorites, but others definitely are older or younger. 

Less-phosphatic intervals that likely are coeval with the 

main episode of Lisburne Group phosphorite formation have 

been found in drowned platform facies near the top of the Lisburne in the western Brooks Range (Wolverine plate of EMA; 

KRA) and in slope and basinal facies of the Kuna Formation 

in the western and west-central Brooks Range (Red Dog and 

Key Creek plates of EMA; PCA). Intervals younger than the 

main Lisburne Group phosphorites occur mainly at the top of 

shallow-water sections of the Lisburne in the central Brooks 

Range (EMA); conodont data and regional correlations indicate that some of these are late early Chesterian-earliest Morrowan but others are early Morrowan (Early Pennsylvanian) or 

younger. Phosphatic intervals of Early Mississippian (Osagean) age are less common, but have been found in basinal 

strata in the western Brooks Range (PCA, EMA?) and in the 

lower part of the Lisburne Group in the Ivotuk Hills and the 

Lisburne well (locs. 6, 7, fig. 1; Dumoulin and Harris, 1993). 

Phosphatic grains in all of these sections mainly are sand-sized 

peloids and phosphatic and phosphatized bioclasts disseminated in skeletal supportstones (platform facies) or in shales 

and carbonate turbidites (basinal facies). Coated phosphatic 

grains and (or) millimeter-scale phosphatic nodules occur in 

some younger samples. Glauconite is a notable component 

of many of the younger phosphatic intervals and of Osagean 

phosphatic strata in the Ivotuk Hills area (Dumoulin and Bird, 

2002); it occurs chiefly as scattered, sand-sized grains mixed 

with phosphate particles in skeletal supportstone and makes up 

as much as 30–40 volume percent of some samples.

Whole-Rock Geochemistry

Black Shales

We obtained whole-rock geochemical data (tables 3, A1) 

for 17 samples of Lisburne Group black shales interbedded 

with phosphorite including 13 samples from 7 locations in the 

EMA and 4 samples from 3 locations in the KRA; 6 of the 

EMA samples are from a single section through the phosphorite-bearing interval at Confusion Creek. Factor analysis of 

the whole-rock data (table A2) shows four main factors, which 

in decreasing order of abundance are marine, hydrothermal, 

detrital, and phosphate. Compared to contemporaneous black 

shales of the Kuna Formation (Slack and others, 2004a), the 

phosphorite-related black shales in our present sample set typically are less siliceous and more calcareous and phosphatic. 

Phosphorite-associated black shales also are characterized by 

higher Corg values, mostly in the range of 4–6 weight percent, 

and include three very Corg-rich (>15 weight percent) samples 

from the Ivotuk Hills and Lisburne Ridge. Rock-eval analysis 

of a black shale from Lisburne Ridge yields a Corg value of 20.2 

weight percent. Molar Corg/molar P ratios vary widely, from 

1.56 to 116, with a median of 25.3. For comparison, molar 

Corg/molar P ratios of 42 black shales of the Kuna Formation (Slack and others, 2004a) range from 1.37 to 396, with 

a similar median of 22.8. With few exceptions, manganese 

concentrations in the phosphorite-related black shales are very 

low (≤0.01 weight percent MnO) as are those in black shales 

of the Kuna Formation (Slack and others, 2004a). Corg-rich 

(>4 weight percent) Lisburne black shales are depleted in S 

compared to typical oxidized marine sediments (fig. 8); data for 

these low-S samples plot mainly within the field of sulfate- and 

iron-limited sediments. An important caveat here is that all of 

these samples come from surface outcrops or talus, not from 

drill cores as is preferred for such analyses of black shales. 

Noteworthy in many of our samples are very high 

contents of Cr and V, ranging up to 1,690 ppm and 2,831 

ppm, respectively. These maximum values are much higher 

than those in the Kuna Formation (Slack and others, 2004a); 

they are within the upper range of concentrations of Cr and V 

reported for black shales worldwide (for example, Desborough 

and Poole, 1983; Yudovich and Ketris, 1997; Coveney, 2003) 

and for modern organic-rich sediments (Brumsack, 2006). 

Data for both Cr and V covary broadly with Corg (fig. 9A,B), 

but no trends exist with respect to Al2O3 or K2O. Molybdenum, which varies from 15.8 to 135 ppm in the black shales 

(table 3), shows broad correlations with both Corg and S 

(fig. 9C,D). Other metals that are concentrated locally in the 

phosphorite-related black shales include Zn (up to 4,670 ppm), 
12 Depositional Setting and Geochemistry of Phosphorites and Metalliferous Black Shales, Northern Alaska

Figure 7. Detailed stratigraphy of the phosphorite-bearing interval at Confusion and Skimo Creeks (locs. 10, 11, figs. 1, 2). 

Phosphorite beds are interbedded with organic-rich black shale and fine-grained radiolarian and spiculitic limestone. Corg

values are shown only for shale samples. See figure 14 for a spectral gamma-ray profile of the Skimo Creek section.

SKIMO CREEK

Samples Clasts Corg Samples Clasts Corg

Samples

T Thin section

C Conodont

G Geochemistry

Go Organic 

geochemistry only

Clasts

CC Calcareous

P Phosphatic

R Radiolarian

S Spicule

T

T

T

T

T

T

T

T

T

T

T

T P

T 

T PR

T

T

T

8 %

P

P

P

P

S

S

S

S

S

Go PR

Go PS

Go

 G

G PR

R

C

C

C

 5.13 %

5.5 %

5.3 %

35

m

30

25

20

15

10

5

0

35

m

30

25

Rock Types

P

rudstone

hosphatic grainstone, 

Chert (concretion)

Lime mudstone-wackestone

(concretion)

Organic-rich black shale

Dolostone (crinoid grainstone)

with intercrystalline

porosity and dead oil

Figure 7
 Whole-Rock Geochemistry 13

black shales from the EMA. All of these data reflect paleoredox conditions in bottom waters, with limited influence from 

authigenic reactions involving pore fluids (Piper and Calvert, 

2009, and references therein).

Data for REE in the phosphorite-related black shales are 

broadly similar with respect to overall patterns and magnitude of Ce anomalies (fig. 12A). For most samples, shalenormalized data show consistent trends with abundance levels 

(excluding Ce) of ~0.5 to ~5x Post Archean Average Shale 

(PAAS), and middle REE (MREE) < heavy REE (HREE). 

This range of REE abundance levels mainly reflects relative 

proportions of phosphate, terrigenous detrital material, and 

biogenic silica. Characteristic are large, negative Ce anomalies 

(calculated Ce/Ce*; table 3) of 0.16–0.34, and no Eu anomalies. Smaller negative Ce anomalies (Ce/Ce*=0.46–0.78) 

occur in three samples, all of which are from the KRA; data 

for two of these samples also fall off the expected inverse 

trend between P2O5 and Ce/Ce* (fig. 13D). 

Phosphorites

Whole-rock analyses were obtained for 24 granular phosphorites from 13 locations in the EMA and 3 phosphorite nodules 

from 2 locations in the KRA; 9 samples are from a single section 

through the phosphorite interval at Confusion Creek. Major differences in bulk composition among the granular phosphorites 

(table 3) mainly reflect variations in the amount of silica cement 

and the amount and type of carbonate cement, including relative proportions of calcite and dolomite. Compared to the black 

shales, the phosphorites typically contain less Corg, although one 

Figure 7. Detailed stratigraphy of the phosphorite-bearing interval 

at Confusion and Skimo Creeks (locs. 10, 11, figs. 1, 2). Phosphorite 

beds are interbedded with organic-rich black shale and fine-grained 

radiolarian and spiculitic limestone. Corg values are shown only for 

shale samples. See figure 14 for a spectral gamma-ray profile of the 

Skimo Creek section.—Continued.

Figure 8. Total organic carbon (Corg) versus S plot, showing that 

most Lisburne Group phosphorite-related black shales have low 

S/Corg ratios, falling within the field of sulfate- and iron-limited 

sediments, similar to black shales of the Kuna Formation (Slack 

and others, 2004a).

Ni (up to 551 ppm), Cu (up to 312 ppm), U (up to 118 ppm), 

As (up to 78 ppm), Se (up to 111 ppm), Cd (up to 142 ppm), 

Ag (up to 43.5 ppm), and Tl (up to 12.3 ppm). 

With few exceptions, data for the calculated marine 

fractions of Mo versus those of V and Cr for the black shales 

plot above the sulfate-reducing lines (fig. 10), consistent with 

deposition under suboxic conditions (see Perkins and others, 2008). These diagrams ignore possible contributions of 

the biogenic fraction, which for Mo, V, and Cr are negligible 

(Piper, 1994). Several samples, all from the KRA, plot on or 

close to these lines; these samples also have anomalously high 

contents of MnO (0.10–0.19 weight percent) relative to the 

other phosphorite-related black shales (<0.01 weight percent). 

A plot of the marine fraction of Mo versus Re (fig. 11) indicates that samples plot within the suboxic field, except for four 

CONFUSION CREEK

(4.5 km W of Skimo)

Clasts

T

T (4)

T

T G

G

G

G (2)

G 

G 

G 

G 

G 

G 

G 

G 

G (2)

T

T

T (2)

T

T (2)

T (2)

T 

T

T (2)

T

T (2)

T (2)

T

T (2)

T

T

T

T (3)

T

T

T

T

T (2)

T

P

P

P

P

P

P

P

P

P

P

P

P

P

P

P

P

?

?

S

S

S

S

S

S

S

S

S

S

S

S

Samples

CC

CC

CC

CC

CC

R

R

R

R

R

R

R

R

R

R

 2.92%

 4.19, 5.14%

 9.43%

 8.05%

 6.38%

12

m

10

5

0

 Corg

0 4 8 12 16 20

0

1

2

3

S (WEIGHT PERCENT)

Corg (WEIGHT PERCENT)

Black shale Phosphorite Phosphorite nodule

Regression line for

oxidized marine sediments

(S/Corg = 0.36)

Sulfate- and iron-limited

sediments

Figure 8
14 Depositional Setting and Geochemistry of Phosphorites and Metalliferous Black Shales, Northern Alaska

sample has 6.7 weight percent. As a result of these generally low 

Corg contents, metal concentrations that occur in the black shales 

mostly are absent from the phosphorites (fig. 9), except for locally 

elevated V (up to 763 ppm). Factor analysis of the whole-rock 

data (table A3) shows four main factors, which in decreasing 

order of loadings likely are phosphate, LREE+Y, detrital, and 

marine components.

Abundances of some trace elements covary with P2O5. 

Such trends are shown by F and Sr, and to a lesser extent by 

U (fig. 13A–C). The three phosphorite nodules are distinctive 

in having much higher Sr concentrations than do the granular 

phosphorites (fig. 13B). Shale-normalized REE data show 

overall abundances (excluding Ce) of ~0.4 to 15x PAAS, 

MREE < HREE, uniformly large, negative Ce anomalies (Ce/

Ce*) of 0.08–0.19, and no Eu anomalies (fig. 12B). The three 

phosphorite nodules, in contrast, have much smaller negative Ce 

anomalies of 0.61–0.79 (figs. 12C, 13D).

Discussion

Depositional Setting

Lisburne Group phosphorites are intercalated with lithofacies, such as organic-rich black shale and radiolarian-bearing 

lime mudstone and chert, that contrast strongly with those of 

underlying (and in the eastern EMA and Ikpikpuk well, overlying) platformal-carbonate successions (fig. 4). This lithologic 

change marks an abrupt shift in the depositional regime of the 

Lisburne Group linked to widespread drowning of carbonate 

platforms (Dumoulin and others, 2004, 2008; Whalen and others, 2006), primarily those adjacent to the Kuna Basin (fig. 2). 

We interpret granular phosphorites in the Lisburne 

Group as a hybrid of condensed and allochthonous phosphate 

(Föllmi, 1996). Complex textures of individual phosphatic 

Figure 9. Binary trace-element plots. A, Corg versus Cr. B, Corg versus V. C, Corg versus Mo. D, S versus Mo. Corg, total organic carbon.

0 4 8 12 16 20

0

400

800

1,200

1,600

2,000

Cr (WEIGHT PERCENT)

Corg (WEIGHT PERCENT)

A

Black shale Phosphorite Phosphorite nodule

0 4 8 12 16 20

0

1,000

2,000

3,000 

Corg (WEIGHT PERCENT)

V (WEIGHT PERCENT)

B

2,500

1,500

 500

Mo, IN PARTS PER MILLION

Corg (WEIGHT PERCENT)

C

0 4 8 12 16 20

0

40

80

120

160

Mo, IN PARTS PER MILLION

S (WEIGHT PERCENT)

D

0.0 0.4 0.8 1.2 1.6 2.0

0

40

80

120

160

Figure 9
 Discussion 15

grains, such as composite grains and unconformity-bounded 

coated grains (fig. 6B–D), as well as the co-occurrence of 

peloids and coated grains within individual phosphorite layers 

(figs. 5B, 6B), reflect multiple episodes of phosphogenesis and 

sedimentary reworking during times of stratigraphic condensation (for example, Pufahl and Grimm, 2003). Composite phosphorite intervals, internally bounded by truncation surfaces 

that may be hardgrounds (fig. 6F), further support this model. 

Sharp bed bottoms and local grading (fig. 6B,F), however, 

suggest redeposition of phosphatic particles into deeper water 

settings by storms or gravity flows; many Lisburne Group 

phosphorites and phosphatic limestones show some evidence 

of redeposition. Some composite phosphorites may be amalgamated allochthonous beds.

In the Skimo thrust sheet of the EMA (locs. 9-11, fig. 1; 

table 1), Lisburne Group phosphorites are interbedded with 

>30 m of black shale and fine-grained limestone (fig. 7) that 

accumulated as hemipelagic strata in an outer-ramp to basinal 

environment (Dumoulin and others, 2008). Conodont biofacies, a limited, largely pelagic fauna, and scarce evidence 

of bioturbation all suggest a deep-water, poorly oxygenated 

setting. Rare benthic faunal elements in these lithologies 

appear transported. Thin concentrations of calcareous clasts 

in shale and limestone are most likely distal-storm or gravityflow deposits. Phosphatic rocks in this thrust sheet also are at 

least partly allochthonous, although local phosphate cement 

indicates some in-place phosphatization. The source of most 

phosphorites likely was no shallower than the middle ramp 

because radiolarians are abundant, both within and among 

phosphatic grains, and because definitively shallow-water 

bioclasts are absent. 

A spectral gamma-ray profile (fig. 14) through the shale 

and phosphorite unit at Skimo Creek (loc. 11, fig. 1) provides 

additional support for condensed sedimentation. High gammaray response occurs throughout the unit and suggests that 

these facies underwent considerable condensation, probably 

due to sediment starvation and development of phosphatic 

hardgrounds (Loutit and others, 1988; Föllmi, 1996; Lanci 

and others, 2002). U dominates the gamma-ray response, 

with little of the signal originating from K or Th. Uranium 

enrichment of phosphorites and black shales is corroborated 

by our geochemical analyses (fig. 13C) and likely reflects the 

suboxic, reducing depositional setting interpreted for these 

strata. Although the identification of uranium-enriched intervals is not unequivocal evidence of condensation (Posamentier 

and Allen, 1999), condensed sections typically show high 

Figure 10. Binary plots discriminating suboxic denitrifying 

depositional conditions from sulfate-reducing conditions (dashed 

lines). A, marine Mo versus marine V. B, marine Mo versus marine 

Cr. Marine fractions of Mo, V, and Cr were determined by using 

the methods of Perkins and others (2008).

Figure 11. Binary marine Mo versus Re plot discriminating 

suboxic, anoxic, and euxinic depositional settings. Data for Re 

(total concentrations) are considered equivalent to the marine 

fraction (see text). Fields are from Ross and Bustin (2009).

Figure 10

0 40 80 120 160 200

0

1,000

2,000

3,000

MARINE V, IN PARTS PER MILLION

MARINE Mo, IN PARTS PER MILLION

A

Sediment accumulation

under sulfate-reducing conditions

0 40 80 120 160 200

0

400

800

1,200

1,600

2,000

MARINE Cr, IN PARTS PER MILLION

MARINE Mo, IN PARTS PER MILLION

B

Sediment accumulation under 

sulfate-reducing conditions

Black shale Phosphorite Phosphorite nodule

Figure 11

0 40 80 120 160 200

0.0

0.2

0.4

0.6

0.8

1.0

Re, IN PARTS PER MILLION

MARINE Mo, IN PARTS PER MILLION

Sulfidic (?)

Anoxic

Sea water 

Re/Mo = 0.8 x 10-3

Suboxic

Re/Mo = 15 x 10-3

Black shale Phosphorite Phosphorite nodule
16 Depositional Setting and Geochemistry of Phosphorites and Metalliferous Black Shales, Northern Alaska

gamma-ray response (Creaney and Peasey, 1993; Lanci and 

others, 2002).

In the Tiglukpuk thrust sheet of the eastern EMA (table 

1), western EMA, KRA, and Ikpikpuk well, phosphorites 

also formed through both condensation and redeposition and 

are associated with organic-rich shale and (or) radiolarian 

or spiculitic lime mudstone and chert. However, the interval 

containing these distinctive lithologies generally is thinner 

(3–20 m versus 30 m) and has more bioclastic supportstone 

and fewer discrete phosphorite beds. Radiolarians and sponge 

spicules are abundant in these phosphorites, but a more varied 

biota occurs in the carbonate supportstone interbeds. Rounded 

to angular quartz grains and quartzose lithic clasts form nuclei 

for many coated grains in the Tiglukpuk phosphorites (fig. 

6E). These differences suggest somewhat shallower settings 

on the middle to outer ramp. Structural studies indicate that 

strata in the Tiglukpuk thrust sheet accumulated ~12–17 km 

landward of coeval strata in the Skimo thrust sheet (Dumoulin and others, 2008); if the slope of the Lisburne ramp was 

~0.15–0.25° (Burchette and Wright, 1992), these distances 

imply a water-depth differential of 35–75 m between the two 

sections. It is likely that phosphorites in the western EMA, 

KRA, and Ikpikpuk well also were deposited closer to land 

(further upramp) than those in the Skimo thrust sheet. 

In the KRA and western EMA, phosphorites occur at or 

very near the top of the Lisburne Group (fig. 4) and formed 

during final drowning of the Lisburne carbonate platform. 

Shallow-water carbonate deposition never resumed in these 

areas during Paleozoic time. Phosphorites in the eastern 

EMA and the Ikpikpuk well, however, are overlain by >100 

m, and nearly 1,000 m, respectively, of latest Mississippian 

and younger Lisburne Group strata, indicating that platform 

drowning associated with phosphatization in these areas was 

temporary. Final drowning of the Lisburne carbonate platform 

occurred during the Early Pennsylvanian (Morrowan) in the 

central Brooks Range (Dumoulin and others, 2008), but did 

not take place until the Early Permian in the Ikpikpuk-Umiat 

Basin (Dumoulin and Bird, 2001).

Evidence for Upwelling

Paleontologic and sedimentologic data are consistent 

with the hypothesis that Lisburne Group phosphorites formed 

as part of a nutrient-rich, upwelling regime (Dumoulin and 

others, 2004, 2008). Abundant radiolarians within the phosphorites, as well as within associated limestone, shale, and 

chert, may be analogous to modern plankton accumulations 

in high-productivity upwelling zones. Faunal shifts in the Lisburne Group provide additional evidence for nutrient-rich conditions during phosphatization. In the Skimo Creek section, 

200 m of middle- to inner-ramp carbonate strata that underlie 

the phosphorite and black shale interval show a clear faunal 

and lithologic progression indicative of increasing eutrophication (for example, Caplan and others, 1996): coralline biotas 

are succeeded by faunas that lack corals but contain algae and 

foraminifers, which are in turn overlain by pelmatozoan- and 

Figure 12. Shale-normalized REE plots showing representative 

data. A, Black shales; B, phosphorites; C, phosphorite nodules. 

Normalizing values from PAAS (Taylor and McLennan, 1985).

0.1

1

10

La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

50

Sample/PAAS

Black shales A

0.1

1

10

La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

50

Sample/PAAS

Phosphorites B

0.1

1

10

La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

50

Sample/PAAS

Phosphorite nodules C

Figure 12
 Discussion 17

Figure 13. Binary P2O5 plots. A, P2O5 versus F; B, P2O5 versus Sr; C, P2O5 versus U; D, P2O5 versus Ce/Ce*. Ce/Ce* is the calculated Ce 

anomaly, relative to PAAS; see table 3 headnote for formula used.

bryozoan-rich assemblages. Calcareous peloids and micritized 

grains become less abundant upward and are absent from the 

pelmatozoan- and bryozoan-dominated rocks. A mirror image 

of this succession is seen in 100 m of ramp carbonate strata 

that overlie the phosphatic zone. Less detailed faunal studies 

suggest that similar patterns characterize other Lisburne Group 

sections that contain phosphorites.

Occurrences of organic-rich shale and multiple beds of 

granular phosphorite also suggest a setting with high productivity (for example, Parrish, 1982). Final drowning of the 

Lisburne carbonate platform in the western Brooks Range, 

and its penultimate drowning in the central Brooks Range 

(fig. 4), were synchronous with phosphatization associated 

with suboxic conditions near the upwelling-induced oxygen 

minimum zone; thus, the Lisburne platform drowning likely 

was due, at least partly, to nutrification produced by upwelling (Dumoulin and others, 2004, 2008; Whalen and others, 

2006). High productivity also has been linked to metallogenesis in the Red Dog Zn-Pb-Ag district (fig. 1), which is 

approximately coeval with the major episode of phosphogenesis in the Lisburne Group. Abundant organic carbon 

in host black shales of the Kuna Formation there served as 

an important reductant during mineralization (Kelley and 

others, 2004b), and biosiliceous cap rocks may have focused 

mineralizing fluids in the shallow subsurface (Slack and 

others, 2004a). 

Carbon-Sulfur Relationships

The low Corg/S ratios of the black shales (fig. 8) could 

reflect surficial weathering, nonmarine deposition, or an 

iron-poor provenance (Slack and others, 2004a, and references therein). Given the absence of extensive weathering 

0 10 20 30 40

0

2

4

6

8

10

F (WEIGHT PERCENT)

P2O5 (WEIGHT PERCENT)

A

0 10 20 30 40

0

400

800

1,200

1,600

2,000

2,400

Sr, IN PARTS PER MILLION

B

0 10 20 30 40

0

40

80

120

160

200

U, IN PARTS PER MILLION

C

0 10 20 30 40

0.0

0.2

0.4

0.6

0.8

1.0

Ce/Ce*SN

D

Black shale Phosphorite Phosphorite nodule

Figure 13

P2O5 (WEIGHT PERCENT)

P2O5 (WEIGHT PERCENT) P2O5 (WEIGHT PERCENT)
18 Depositional Setting and Geochemistry of Phosphorites and Metalliferous Black Shales, Northern Alaska

of our samples, selective oxidation of iron sulfides is considered unlikely. Nonmarine deposition is precluded, based 

on widespread occurrence of marine fauna in the sampled 

sections (Dumoulin and Harris, 1993; Dumoulin and others, 

2006a, 2008). As a result, we infer that an iron-poor sedimentary provenance is the most reasonable explanation for 

S-deficiency in the Lisburne Group black shales, as in the 

interpretation of Slack and others (2004a) for black shales of 

the correlative Kuna Formation (avg Fe/Ti=6.34; n=49). This 

model is supported by the low average Fe/Ti ratio of 5.12 for 

17 black shales of the Lisburne Group, compared to the ratio 

of 10.5 for the North American Shale Composite (Gromet and 

others, 1984).

Element Trends and Mineralogical Residence

Trends between some elements in the black shales 

and phosphorites allow for interpretations of mineralogical 

residence of the elements. Broad covariance of both Cr and 

V with Corg (fig. 9A,B) suggests residence mainly in organic 

matter (for example, Algeo and Maynard, 2004), whereas 

the lack of trends with respect to Al2O3 or K2O (not shown) 

argues against a clay-mineral host (cf. Peacor and others, 

2000). Trends between Mo and Corg and S (fig. 9C,D) imply 

a dual residence of Mo in organic matter and pyrite (Ripley 

and others, 1990; Algeo and Lyons, 2006). Mineralogical 

hosts of Zn, Cu, Ag, As, Se, Cd, and Tl concentrations in the 

black shales are unknown, but likely are in both organic matter 

and sulfides (Slack and others, 2004a, 2004b, and references 

therein). High contents of Se and Cd that characterize these 

strata (tables3,A1) may present environmental problems due 

to the toxicity of such elements, in elevated concentrations, to 

animals and people (for example, Piper and others, 2000).

Among the phosphorites, the covariance of P2O5 and F 

(fig. 13A) is consistent with fluorapatite and francolite (carbonate fluorapatite) being the dominant host minerals for both components. Data points that fall off this trend, and others involving 

Sr and U (fig. 13B,C), may reflect dilution by other phases, or in 

the case of anomalously high values, enrichment during diagenesis. The latter explanation is favored for a phosphorite sample 

that contains 1,030 ppm Y and 517 ppm La, which could record 

the presence of one or more discrete Y- and (or) REE-rich minerals, such as xenotime, monazite, and bastnaesite (Vallini and 

others, 2002; Baturin and Dubinchuk, 2005).

Redox Conditions during Sedimentation

Myriad studies have used whole-rock geochemistry to 

evaluate the redox state of bottom waters and pore waters 

during marine sedimentation. The focus of many such studies 

has been on black shales, utilizing data for a variety of components including Mn, Corg, S, and the redox-sensitive trace 

elements V, Cr, U, Ni, Mo, Re, and Ce (for example, Rimmer, 2004; Piper and others, 2007; Algeo and Maynard, 2008; 

Ross and Bustin, 2009). Paleoredox conditions of phosphorite 

deposition have been investigated chiefly through the use of 

Figure 14. Lithofacies and spectral gamma-ray response of the shale and phosphorite unit (~30 m thick) at Skimo Creek (loc. 11, fig. 1). 

M, mudstone; W, wackestone; P, packstone: G, grainstone; F/R, floatstone/rudstone. To the right of the lithologic column are quantitative 

spectral gamma-ray data illustrating percent K and ppm U and Th. Shales in the lower 20 m of the unit have slightly elevated K contents, 

reflecting an abundance of clay minerals. Elevated U contents in the upper 10 m reside mainly in phosphorites (see fig. 13C).

Explanation Calcareous shale

Phosphorite

Chert Lenses

Covered interval

Argillaceous limestone

Thin-bedded limestone

Thin-bedded dolostone

Th

U

Gamma Ray

10

0

20

30

0

30

40

50

M W P G F/R 0 1 2 0 20 40 60 80 100 120

Meters

%K ppm

Figure 14
 Discussion 19

shale-normalized REE patterns, especially the nature and magnitude of Ce anomalies (for example, McArthur and Walsh, 

1984; Piper and others, 1988; Watkins and others, 1995; 

Baturin, 2005; Daessle and Carriquiry, 2008). Early paleoredox studies of black shales typically produced conflicting or 

equivocal results, in many cases because the whole-rock analyses were not screened to use data selectively for the marine 

fraction and to exclude the terrigenous and biogenic fractions 

(Piper, 1994, 2001; Perkins and others, 2008). In the present 

study, we adopt this newer approach and use calculated marine 

fractions of selected elements in evaluating paleoredox conditions during black-shale and phosphorite deposition within the 

Lisburne Group. It is important to note here that the biogenic 

fractions for V, Cr, and Mo are quantitatively unimportant, 

constituting less than a few parts per million each based on 

analogy with compositions of modern marine plankton (Piper, 

1994); thus, we have not applied correction factors to our data 

for any biogenic fraction that may be present. For Re, the total 

(uncorrected) concentration is used because the terrigenous 

fraction of this element is less than 0.5 ppb based on data for 

average continental crust, and the biogenic fraction likely is 

negligible given the very low Re/Mo ratios of about 10-2 to 

10-4 that characterize black shales elsewhere (Crusius and 

others, 1996); hence, the marine fraction of Re in our samples 

is considered equivalent, within analytical uncertainty, to the 

total concentration. Significantly, the redox conditions inferred 

here, based on marine fractions of V, Cr, Mo, and Re, lack 

major influence from pore fluids during diagenesis because 

accumulation of high contents of these hydrogeneous elements 

(for example, V) requires renewal of bottom waters from overlying seawater (Piper and Calvert, 2009), a process that is not 

quantitatively important in subsurface pore fluids. 

Geochemical analyses of the phosphorite-related black 

shales suggest deposition under suboxic, denitrifying conditions. Evidence for this redox setting is provided by high V/

Mo and Cr/Mo ratios (all marine fractions) of most samples 

(fig. 10), based on the destabilization of aqueous V- and Crbearing species within denitrifying regions of modern oxygenminimum zones (Piper, 2001; Sageman and others, 2003). 

Similarly, the generally high Re/Mo ratios (fig. 11) reflect 

preferential reduction of Re, relative to Mo, in suboxic bottom 

waters (Crusius and others, 1996). Also significant are the 

high Cr+V marine fractions (MF), showing a mean of 1,572 

ppm, with most samples having 1,594–4,422 ppm CrMF+VMF. 

Among all 17 samples, CrMF/VMF ratios vary widely 

(0.12–4.33), suggesting different degrees of denitrification 

(Piper, 1994), the low and high ratios implying strongly and 

mildly denitrifying conditions, respectively. Most CrMF/VMF

ratios are 0.8 to 1.9, which indicate moderate to strong denitrification. In the Confusion Creek section, CrMF/VMF ratios 

for five samples decrease systematically upsection, from 3.34 

(0.4 m above base) to 0.17 (7.5 m above base); this pattern 

suggests increased denitrification with time, accompanying a 

shallowing-upward trend as defined by petrographic and biotic 

data. In a geochemical study of Devonian black shales of the 

Appalachian Basin, Sageman and others (2003) interpreted 

high contents of Cr+V as reflecting both redox oscillations in 

denitrifying bottom waters and the extent of sediment condensation. Gamma-ray profiles of the Skimo Creek section (fig. 14; 

Dumoulin and others, 2008) also suggest that this interval of 

black shale and phosphorite is highly condensed. We conclude, 

therefore, that phosphorite-related black shales of the Lisburne 

Group mainly formed by condensed sedimentation under suboxic denitrifying conditions. Exceptions occur for coeval black 

shales of the KRA, which have relatively high MnO contents 

(0.10–0.19 weight percent) and lower VMF/MoMF and CrMF/

MoMF ratios (fig. 10) compared to other phosphorite-related 

black shales of the Lisburne Group. These data suggest that 

the KRA black shales were deposited in more oxidizing bottom waters, although probably not fully oxic waters as exist 

typically in modern oceans. Their smaller negative Ce anomalies (fig. 12A), relative to other black shales of the Lisburne 

Group, are consistent with this interpretation because analyses 

of these KRA samples fall off the inverse trend in P2O5 versus 

Ce/Ce* shown by samples from other localities in the Brooks 

Range (fig. 13D). In contrast, all other black shales in our study 

display large negative Ce anomalies that follow the inverse 

trend towards the larger negative Ce anomalies of the granular 

phosphorites (average Ce/Ce*=0.11 ± 0.03; table 3). Coeval, 

variably phosphatic black shales of the Kuna Formation show 

a similar trend (fig. 8F in Slack and others, 2004a). Possible 

effects of high concentrations of Corg and inferred organic 

complexation on Ce anomalies in the black shales, as shown by 

experimental data (Davranche and others, 2005), apparently are 

unimportant because our Corg-rich samples lack evidence for 

suppression of Ce anomalies.

In modern oceans, very large negative Ce anomalies 

(<0.15) occur in seawater only at or below water depths of 

~400 m (for example, German and others, 1995; Alibo and 

Nozaki, 1999). Assuming that the redox profiles of Carboniferous oceans were similar to those of today (excluding time periods of global ocean anoxia; Arthur and Sageman, 1994), the Ce 

anomalies of the granular phosphorites could reflect deposition at water depths of ≥400 m. A similar model was proposed by Bonnot-Courtois and Flicoteaux (1989) and Baturin 

and Yushina (1998) for Late Cretaceous to early Tertiary 

phosphorite deposition, based on REE patterns and Ce data. 

Elderfield and Pagett (1986) and Grandjean and others (1987) 

found analogous contrasts in the Ce anomalies of modern fish 

remains from shallow shelf versus deep-sea settings. Based on 

these data and related sedimentological evidence, we present 

two models for the depositional setting and redox evolution of 

the Lisburne Group phosphorites and associated black shales.

Depositional Models

The first model involves suboxic deposition under 

relatively deep-water (≥400 m) conditions. Projection of the 

inverse trend in P2O5 versus Ce/Ce* for the black shales (fig. 

13D) implies that these Corg-rich strata also were deposited 

under the same depth constraints as the granular phosphorites. 
20 Depositional Setting and Geochemistry of Phosphorites and Metalliferous Black Shales, Northern Alaska

This interpretation is based on the assumption that the REE 

contents and Ce anomalies are contained mainly in minor 

apatite; several samples having <5 weight percent P2O5 do 

not follow this trend, probably due to influence by REErich detrital minerals such as monazite and xenotime (for 

example, Lev and others, 1999), and (or) to later diagenetic 

effects. However, uniformly low contents of MnO and 

consistent data for V, Cr, Mo, and Re (figs. 10, 11) preclude 

their formation in fully oxic seawater, instead suggesting 

deposition chiefly under suboxic conditions, in agreement 

with models proposed by numerous other workers (Arning 

and others, 2009b, and references therein). This model is 

supported by the nature of Ce anomalies in Quaternary and 

Recent phosphorites, which typically display small negative 

to small positive anomalies in samples from present water 

depths of ≤353 m (avg Ce/Ce* = 0.99  ±  0.09, n = 29; Piper 

and others, 1988; Watkins and others, 1995; Rao and others, 

2000, 2002; Baturin, 2005), whereas large negative anomalies like those in many of the Lisburne Group phosphorites 

(avg Ce/Ce* = 0.11  ±  0.03; table 3) occur in samples from 

modern seamounts at water depths of 1,400 and 2,000 m 

(avg Ce/Ce* = 0.10  ±  0.10, n = 3; Bau and others, 1996). 

A major problem with this deep-water model is the presence, several tens of meters below and above the phosphorites at Skimo and Tiglukpuk creeks, of sedimentary features 

(thick- and cross-bedded grainstones) and faunal components (foraminifers, algae, micritized bioclasts) that indicate 

midramp or shallower depositional settings (Dumoulin and 

others, 2008). Such settings occur above storm wave base at 

water depths of 100–200 m or less (for example, Wilson and 

Jordan, 1983). Thus, water-depth fluctuations of several hundred meters would be implied both before and after deposition 

of the phosphorites. Eustatic effects of Gondwanan glaciation 

were felt in Laurussia by late Visean time (Smith and Read, 

2000), roughly coeval with Lisburne phosphogenesis, and 

extensional faulting affected northern Alaska throughout much 

of the Mississippian (Young, 2004). However, relative sealevel changes of several hundred meters seem unlikely, even if 

both eustatic and tectonic factors are invoked.

A second, preferred model involves suboxic deposition 

of the phosphorites and black shales under shallower water 

depths of ~100–200 m. This model is supported by the sedimentologic and faunal data outlined above and is consistent 

with settings of modern sedimentary phosphate deposits 

forming in suboxic bottom waters on the Namibian and 

Peruvian shelves (Kuypers and others, 2005; Piper and Perkins, 2011). However, the model does not explain the lowest 

Ce/Ce* values (<0.1) of the phosphorites, which, based 

on modern settings, imply deposition at or below a water 

depth of 400 m. To our knowledge, no REE data are available for suboxic seawater in a modern, open-ocean ramp or 

shelf environment, thus redox-based analogs to the Lisburne 

Group are unknown. Nevertheless, some data are consistent 

with this model, such as the low Ce/Ce* values that occur at 

and near the upper oxic-suboxic interface off the northeast 

coast of Oman in the Northwest Indian Ocean (German and 

Elderfield, 1990). Especially important is the likelihood of a 

large spike in oxygenation of the Permo-Carboniferous ocean 

(Holland, 2006), owing to its equilibrium with a highly 

oxygenated atmosphere that developed following the evolution of large vascular land plants and concomitant burial of 

organic carbon (Berner and Canfield, 1989; Berner, 2006). 

This inferred major oxygenation of the ocean would have 

greatly decreased Ce concentrations and Ce/Ce* values in 

seawater due to increased scavenging of Ce by Mn oxides 

and oxyhydroxides (for example, Byrne and Sholkovitz, 

1996; Ohta and Kawabe, 2001) that likely precipitated during this time period. Piper and others (2007) first proposed 

this model in order to explain the large negative Ce anomalies of phosphorites in the Permian Phosphoria Formation 

of southeastern Idaho and western Wyoming. We suggest 

that the model also applies to the uniformly large negative 

Ce anomalies of phosphorites in the mainly Carboniferous 

Lisburne Group (fig. 12B) and in the Mississippian Deseret 

Limestone and Woodman Formation of eastern Nevada and 

western Utah (Jewell and others, 2000). 

Both abiotic and biotic processes have been proposed for 

the precipitation of marine phosphate deposits (for example, 

Föllmi, 1996). Abiotic processes are constrained by kinetic 

limitations. A growing consensus argues for microbial activity 

as the predominant mechanism for phosphate precipitation 

(Nathan and others, 1993; Schulz and Schulz, 2005; Arning 

and others, 2009a). Recent experimental work by Goldhammer and others (2010) indicates that apatite is sequestered 

preferentially by sulfur bacteria in anoxic pore fluids, especially those in iron-limited sediments that lack sufficient Fe 

for authigenic pyrite formation. Within subsurface pore fluids, 

such iron-limited sediments generate abundant H2S and, as 

a result, increased amounts of sulfur bacteria that mediate 

apatite precipitation. This bacteriogenic model is consistent 

with the apparently iron-limited nature of Lisburne Group 

black shales (avg Fe/Ti=5.12) and related low S/Corg ratios 

(fig. 8), and it also explains their low median Corg/P ratio of 

25.3 relative to those of black shales of Carboniferous age 

elsewhere (range of median Corg/P ratios 36–176; Algeo and 

Ingall, 2007).

Diagenetic Effects

The redox signatures of the black shales and phosphorites of the Lisburne Group also could have been affected 

by interaction with pore fluids during diagenesis. In modern marine sediments having appreciable organic-carbon 

contents, such pore fluids vary in redox state from suboxic to 

anoxic to locally sulfidic. Reactions among oxygen-depleted 

pore fluids, organic carbon, and sedimentary minerals in 

these settings may produce diagenetic growth of new phases 

and different redox signatures including, for example, 

formation of Mn carbonates and (or) Fe sulfides, higher 

mineral and bulk Fe2+/(Fe3++Fe2+) ratios, and higher Ce/Ce* 

values. Possible changes in Ce anomalies during diagenesis 
 Discussion 21

are especially important because such anomalies serve as 

important monitors of paleoredox history; we thus focus here 

on Ce anomalies for evaluating possible diagenetic effects 

on redox signatures. Excluding the three samples from the 

KRA, all of the Lisburne Group black shales have similar Ce 

anomalies (Ce/Ce*=0.16–0.34; figs. 12A, 13D), thus suggesting either minimal influence by pore fluids or similar and 

pervasive overprinting during diagenesis. The former explanation is favored here because Ce/Ce* values in the phosphorites and P-rich (>7 weight percent P2O5) black shales all 

are ≤0.21, in contrast to values of >0.5 inferred for partial 

to complete equilibration with anoxic pore fluids, which in 

modern marine sediments have Ce/Ce* values mainly in the 

range of ~0.7–1.1 (Elderfield and Sholkovitz, 1987; Haley 

and others, 2004). However, we cannot rule out some diagenetic mobility of REE (Lev and others, 1999), especially for 

the low-P (<4 weight percent P2O5) black shales that fall off 

the inverse trend in Ce/Ce* versus P2O5 as defined by other 

samples from the Lisburne Group (fig. 13D), and for the 

four black shales that plot within the anoxic field on the Mo 

versus Re discrimination diagram (fig. 11).

Unlike massive granular phosphorites that generally are 

believed to form on or close to the sea floor coeval with sedimentation, discrete phosphorite nodules are viewed as products of subsurface diagenesis (for example, Jarvis and others, 1994; Cook and Shergold, 2005). The three phosphorite 

nodules in our Lisburne Group database show small, negative 

Ce anomalies (Ce/Ce*=0.61–0.79) that contrast with the much 

larger negative anomalies of the P-rich black shales and phosphorites (fig. 12). These smaller Ce anomalies are consistent 

with phosphate precipitation from anoxic pore fluids, based on 

similar ranges shown by anomalies that occur in the modern 

examples described above; however, diagenetic growth of 

the nodules within suboxic pore fluids cannot be ruled out. 

The mostly flat patterns of the MREE within the nodules 

(fig. 12C) differ greatly from the typical concave-downward, 

“hump-type” patterns that occur in many phosphate nodules 

elsewhere, owing to preferential mobility of MREE during 

diagenesis (for example, Jarvis and others, 1994; Kidder and 

others, 2003; Jiang and others, 2007).

Redox Conditions during Deposition 

of the Kuna Formation

Slack and others (2004a) interpreted whole-rock geochemical data for black shales of the Kuna Formation as 

recording deposition mainly in anoxic bottom waters, based 

on low MnO contents of <0.01 weight percent (with several 

exceptions) and generally high Cr and V concentrations; 

however, in their study, marine fractions of V, Cr, and Mo 

were not calculated for discriminating anoxic and suboxic 

conditions of bottom waters during Kuna sedimentation. 

Using this approach yields mostly high VMF/MoMF and CrMF/

MoMF ratios like those shown by the coeval Lisburne Group 

phosphorite-related black shales (fig. 10). These new data 

suggest, therefore, that the Kuna Formation black shales 

were deposited chiefly in suboxic, not anoxic, bottom waters. 

Sources of Metal Concentrations 

in the Black Shales

Metalliferous black shales have been studied for decades, 

but the sources of metal concentrations within them have 

remained controversial. Four principal sources have been 

identified (for example, Piper, 1994): terrigenous (detrital), 

biogenic, hydrogenous (seawater), and hydrothermal. A 

detailed quantitative evaluation of these possible sources is 

beyond the scope of the present study; herein, we focus on 

the overall metal concentrations and qualitatively evaluate 

their origins. Highlighted for 17 Lisburne Group black shales 

are the average contents (table 3) of Cu (144 ± 72 ppm), Zn 

(1,112 ± 1,081 ppm), Cd (52.5 ± 48.6 ppm), Ni (283 ± 137 ppm), 

Ag (13.4 ± 12.3 ppm), and Tl (2.1 ± 3.3 ppm), which are higher 

than those of most black shales worldwide (for example, 

Yudovich and Ketris, 1997). Ratios of these averages for Zn/

Cu, Cd/Cu, and Ni/Cu are similar to ratios of these metals in 

modern plankton (fig. 1 in Piper, 1994), as are the trends of Zn 

versus Cu, Cd versus Cu, and Ni versus Cu for the majority 

of our black shale samples, thus suggesting that these metals 

were derived largely from biogenic sources. However, a few 

samples have Zn and Cd contents (up to 4,670 ppm and 142 

ppm, respectively) and Zn/Cd ratios that are much higher than 

those of modern plankton, consistent with an additional hydrothermal component. We propose that this component was 

derived from the giant stratiform Zn-Pb-Ag deposits of the 

Red Dog district (Slack and others, 2004b) and (or) the coeval 

Drenchwater Zn-Pb-Ag deposit (fig. 1; Graham and others, 

2009) which, like similar deposits worldwide, formed by 

synsedimentary-hydrothermal processes (for example, Leach 

and others, 2005). In our model, metal-rich hydrothermal 

fluids vented (exhaled) into bottom waters of the Kuna Basin 

were transported by upwelling currents to outer ramp settings, 

and precipitated metals syngenetically (from seawater) during 

deposition of Lisburne Group phosphorites and black shales. 

Some of the phosphorite-related black shales also have 

high contents of Tl, including four samples that contain 

3.5–12.3 ppm; for comparison, Tl contents of 49 unaltered 

and unmineralized black shales of the coeval Kuna Formation 

are ≤1.1 ppm (Slack and others, 2004a, d). Relative to this 

threshold value, most sulfide ores and hydrothermally-altered 

black shales of the Red Dog district have very high Tl concentrations of up to 313 ppm and 110 ppm, respectively (Slack 

and others, 2004b), as does the Drenchwater deposit (Graham 

and others, 2009). We infer that the locally high Tl contents 

in the phosphorite-related black shales reflect a hydrothermal 

component derived from one or more sedimentary-exhalative 

(sedex) systems within the Red Dog district and (or) the 

Drenchwater area. The high Ag contents (up to 43.5 ppm) 

that characterize the majority of the phosphorite-related black 

shales similarly may reflect contributions from these distal 
22 Depositional Setting and Geochemistry of Phosphorites and Metalliferous Black Shales, Northern Alaska

sedex-type hydrothermal systems. A more detailed, quantitative evaluation of the sources of metals in the Lisburne Group 

black shales will be the focus of a future study.

Environmental Synthesis

Phosphorites and associated black shales of the Lisburne 

Group likely accumulated in middle to outer ramp settings. 

Geochemical data, in concert with paleogeographic reconstructions, imply that the black shales in the phosphorite 

interval were deposited when suboxic, denitrifying bottom 

water upwelled from the Kuna Basin onto the margins of 

adjacent carbonate platforms. Lithologic and paleontologic 

data indicate similar, coeval incursions in the Ikpikpuk-Umiat 

Basin. Sedimentologic and faunal evidence suggest that these 

upwelling pulses were linked to relative sea-level rise, which 

in turn reflected eustatic and (or) tectonic changes (Dumoulin 

and others, 2008); sea-level rise commonly is associated with 

phosphogenesis (for example, Föllmi, 1996). 

Upwelling systems, due to cool-water intrusion, high 

nutrient loads, enhanced productivity, and related dysoxic conditions, can reduce carbonate production and lead to carbonate-platform drowning (Hallock and Schlager, 1986; Whalen, 

1995). Many workers have noted the abundance of upwellinginfluenced, heterozoan-dominated carbonate ramps during 

the Carboniferous (for example, Wright, 1994; James, 1997). 

The Lisburne ramp also appears to have been influenced and 

partially drowned by an associated upwelling system. Schematic reconstructions of continental margin upwelling zones 

(Parrish, 1982; James, 1997; Parrish and others, 2001) provide 

insight into the distribution of upwelling-related lithofacies in 

the Lisburne Group (fig.15). Decay of organic matter in the 

most productive part of the upwelling zone forms a belt of 

organic-rich sediment beneath oxygen-depleted water, with 

phosphate precipitation favored on the landward margin of 

this zone (Parrish and others, 2001). Organic-rich black shale, 

fine-grained limestone, and phosphorite were deposited along 

the ramp in the transition between these two zones; phosphate likely precipitated within suboxic bottom waters at and 

just below the sediment-water interface (Föllmi, 1996; Piper 

and Perkins, 2011). Glauconite formation is favored further 

landward in more oxygenated water. Less-phosphatic Lisburne 

Group strata that contain up to 40 volume percent glauconite 

may have formed in this more shoreward setting; these strata 

are not interbedded with organic-rich rocks. All highly glauconitic facies in the Lisburne Group are older or younger than 

the phosphorites, however, forming prior to or after the period 

of most intense primary productivity and suboxia. Because the 

formation of glauconite (Fe3+-rich mica) requires a source of 

iron in local sediments, its abundance in the glauconitic facies 

suggests that iron-limited conditions largely were restricted 

to the phosphorite and interbedded black shale sequence. A 

corollary of this interpretation is that iron-limited detritus was 

contributed intermittently to the Lisburne depositional system, 

mainly during late Meramecian to early Chesterian time.

The inability of carbonate platforms in the western 

Brooks Range to recover from the early Chesterian drowning 

episode, in contrast to platforms to the east and north, suggests 

that upwelling and consequent nutrification were more intense 

to the west (for example, Whalen, 1995; Caplan and others, 

1996). Additionally, or alternatively, tectonically enhanced 

rates of sea-level rise may have been higher to the west; this 

hypothesis is supported by abundant evidence for Late Mississippian extensional faulting in the Red Dog district (Young, 

2004; Kelley and others, 2004a). Downdropping of parts of 

the central Brooks Range (eastern EMA) along reactivated 

extensional structures is a likely cause of final drowning of 

the Lisburne platform in this area during the early Morrowan. 

Nutrification appears to have been less important in this 

drowning as it is associated only with minor phosphatization 

and deposition of much less organic-rich shale (Whalen and 

others, 2006; Dumoulin and others, 2008).

Paleogeography

Development of a Carboniferous upwelling system 

in northern Alaska requires specific paleogeographic and 

paleoceanographic conditions. Wind-driven, ocean-surface 

currents must parallel the coastline, induce offshore Ekman 

transport, and drive either meridional or zonal coastal upwelling (Parrish, 1982). Parrish (1982) did not predict upwelling in 

northern Alaska during Carboniferous time, but the Paleozoic 

position of northern Alaska in the global reconstructions that 

formed the basis for her predictions was poorly constrained. 

More recent paleogeographic reconstructions (Lawver and 

others, 2002; Colpron and Nelson, 2009) are consistent with 

Carboniferous upwelling in northern Alaska, but differ in the 

type of upwelling expected. 

Lawver and others (2002) suggested that Arctic Alaska 

formed a roughly east-trending, peninsular extension of Laurussia that was situated at about 30°N during the Late Mississippian (fig. 16). This model is compatible with zonal marine 

upwelling along Arctic Alaska, produced by circum-polar 

easterly currents that generated northerly-directed Ekman 

transport and southerly-directed upwelling. The modern 

Antarctic circum-polar current reaches north to latitudes of 

approximately 40°S; development of zonal upwelling along 

the Arctic Alaska continental margin would require a circumpolar current that reached a paleolatitude of about 30–40°N.

Colpron and Nelson (2009) showed Arctic Alaska as a 

north-trending peninsula of Laurussia that lay between ~30° 

and 40°N in Late Mississippian time; this reconstruction is 

consistent with meridional marine upwelling along the west 

side of Arctic Alaska, analogous to that found along the modern Pacific margin of the northwestern United States. Meridional upwelling also was favored by Kelly and others (2007) to 

explain deposition of Triassic phosphorites in northern Alaska.

Paleoenvironmental data suggest that meridional upwelling better explains phosphorite deposition in the Lisburne 

Group. The climate in northern Alaska became increasingly 
 Discussion 23

Figure 15. Schematic reconstruction of 

lithofacies and water circulation perpendicular 

to the paleoshoreline along the northern side 

of the Kuna Basin during deposition of Lisburne 

Group phosphorites, after Burchette and Wright 

(1992), James (1997), and Parrish and others (2001); 

maximum water depth on left side of the figure 

is likely ~300 m. Lisburne Group phosphoritebearing strata formed in the transition zone 

between organic-rich and phosphatic facies. 

Less-phosphatic limestones, with as much as 40 

volume percent glauconite, were deposited further 

shoreward in the transition between phosphatic 

and glauconitic facies; such limestones are 

observed only locally and mostly are older or 

younger than the phosphorites. 

LITHOFACIES

Organic-Rich

Sea surface Shoreline

Phosphatic Glauconitic

Oxygen-depleted

bottom

waters Organic-rich

shale, limestone,

redeposited and 

pristine 

phosphorite

Phosphatic

limestone and

pristine 

phosphorite

Glauconitic

limestone with

minor phosphate

High biologic

productivity

0.2 ml/L O2

Nutrient-laden

 waters

Figure 15

Outer ramp to basin Middle ramp Inner Ramp

Figure 16

60°N

30°

0°

30°S

A B

60°N

30°

0°

30°S

Arctic Alaska terrane

Laurussia

Greenland

Cordilleran allochthonous terranes

Ocean surface currents

Siberia

Kazakhstan

Baltica

Gondwana

Ekman transport/upwelling 

Figure 16. Recent reconstructions of Mississippian paleogeography. A, In the model of Lawver and 

others (2002), northern Alaska is shown as a roughly east-trending peninsular extension of Laurussia. A 

zonal marine upwelling system along Arctic Alaska could have been produced by circum-polar easterly 

currents that generated northerly-directed Ekman transport and southerly-directed upwelling. B, In the 

model of Colpron and Nelson (2009), northern Alaska is shown as a roughly north-trending peninsular 

extension of Laurussia. Meridional marine upwelling, analogous to that found along the modern Pacific 

margin of the northwestern United States, could have developed under this paleogeographic arrangement.
24 Depositional Setting and Geochemistry of Phosphorites and Metalliferous Black Shales, Northern Alaska

arid during Late Mississippian (late Meramecian-Chesterian) 

time (Dumoulin and Bird, 2001; Dumoulin and others, 2004). 

Aridity is associated with many meridional upwelling regimes 

(for example, present-day Peru, Namibia, and California; 

Permian Phosphoria Formation), but is less common in zonal 

upwelling environments (for example, present-day Venezuela).

Development of phosphatic rocks on opposing sides of 

the Kuna Basin presents a paleoceanographic conundrum. 

A modern analog for this distribution may be the Gulf of 

Mexico, where the loop current (Hofmann and Worley, 1986) 

sets up a system of circulation that generates upwelling along 

opposing continental shelves. The Gulf of Mexico loop current 

is a clockwise flow northward into the Gulf of Mexico (Hofmann and Worley, 1986); recent upwelling associated with 

loop-current dynamics has been documented on both the eastern margin of the Yucatan Peninsula (Merino, 1997) and along 

the west Florida shelf (Li and Weisberg, 1999; Weisberg and 

others, 2000). Detailed paleogeography and paleoceanography 

of the Kuna Basin is poorly understood, but circulation involving a loop current similar to that in the modern Gulf of Mexico 

could explain the development of upwelling and concomitant 

phosphatic deposits on both sides of the basin.

Formation of less-phosphatic strata within the Lisburne 

Group also may be linked to upwelling. Such facies are coeval, 

older, and younger than Lisburne Group phosphorites. Those of 

late Meramecian-early Chesterian age may have formed along 

parts of the Lisburne platform that were less intensely and (or) 

less consistently affected by upwelling than were the areas of 

phosphorite formation. Older (Early Mississippian) and younger 

(latest Mississippian-Pennsylvanian) less-phosphatic strata 

bracket the time of Lisburne phosphorite deposition, commonly 

contain notable glauconite, and are not associated with organicrich facies. These relations suggest that weaker and (or) more 

intermittent upwelling prevailed during waxing and waning of 

the main episode of Lisburne phosphogenesis, and that phosphate accumulated at these times in a more oxygenated (and 

landward) environment (phosphate-glauconite transition zone of 

Parrish and others, 2001; fig. 15).

Acknowledgments

We thank the Mineral Resources and Energy Resources 

Programs of the USGS for financial support of this study, the 

Alaska Division of Geological and Geophysical Surveys and 

Petro-Canada Oil and Gas for logistical support of fieldwork 

in the central Brooks Range, and Mike Kunz (U.S. Bureau of 

Land Management) for providing camp facilities at Ivotuk and 

Utukok River. We particularly acknowledge Robert Burruss, 

Craig Johnson, and Karen Kelley (USGS), Ellen Harris and 

Paige Delaney (Alaska Division of Geological and Geophysical Surveys), Gil Mull (Alaska Division of Oil and Gas), and 

Jeff Bever, Jeff Lukasic, and Mike McDonough (Petro-Canada 

Oil and Gas) for their help and discussions in the field and 

office. Thanks also to Erin Marsh and Theresa Taylor of the 

USGS for assistance with the figures and to Ken Bird and David 

Piper (USGS) for thorough reviews of an early version of the 

manuscript. Comments by Kurt Grimm, Joe Macquaker, Gene 

Rankey, Peir Pufahl, and an anonymous referee are appreciated. 

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H.A., and Siwiec, B., 2008, Bedrock geologic map of 

the southern Brooks Range, Alaska, and accompanying 

conodont data: U.S. Geological Survey Open-File Report 

2008-1149, 88 p., 2 sheets, sheet 1-scale 1:500,000, sheet 

2-scale 1:600,000.

Trappe, J., 1998, Phanerozoic phosphorite depositional 

systems—A dynamic model for a sedimentary resource 

system: Berlin, Springer-Verlag, Lecture Notes in Earth 

Sciences, v. 76, 316 p.

Vallini, D., Rasmussen, B., Krapež, B., Fletcher, I.R., and 

McNaughton, N.J., 2002, Obtaining diagenetic ages from 

metamorphosed sedimentary rocks—U–Pb dating of 

unusually coarse xenotime cement in phosphatic sandstone: 

Geology, v. 30, p. 1,083–1,086.

Watkins, R.T., Nathan, Y., and Bremner, J.M., 1995, Rare earth 

elements in phosphorite and associated sediment from the 

Namibian and South African continental shelves: Marine 

Geology, v. 129, p. 111–128.

Weisberg, R.H., Black, B.D., and Li, Z., 2000, An upwelling 

case study on Florida’s west coast: Journal of Geophysical 

Research, v. 105, no. C5, p. 11,459–11,469.

Whalen, M.T., 1995, Barred basins—A model for eastern ocean 

basin carbonate platforms: Geology, v. 23, p. 625–628.

Whalen, M.T., Dumoulin, J.A., Lukasic, J.J., and White, J.G., 

2006, Simultaneous carbonate platform progradation and 

drowning, Lisburne Group, eastern and central Brooks 

Range, Alaska [abs.]: Geological Society of America 

Abstracts with Programs, v. 38, no. 5, p. 86.

Wilson, J.L., and Jordan, C., 1983, Middle shelf, in Scholle, 

P.A., Bebout, D.G., and Moore, C.H., eds., Carbonate depositional environments: American Association of Petroleum 

Geologists Memoir 33, p. 297–344.

Wright, V.P., 1994, Early Carboniferous carbonate systems—

An alternative to the Cainozoic paradigm: Sedimentary 

Geology, v. 93, p. 1–5.

Wright, V.P., and Burchette, T.P., 1998, Carbonate ramps; 

an introduction: Geological Society of London Special 

Publication 149, 465 p. 

Young, L.E., 2004, A geologic framework for mineralization 

in the western Brooks Range, Alaska: Economic Geology, v. 

99, p. 1,281–1,306.

Yudovich, Ya.E., and Ketris, M.P. 1997, Geochemistry of 

black shales, Part I—Outline: Syktyvkar, Russia, Russian 

Academy of Sciences, Komi Science Centre, 52 p. [in 

English].
Tables 1

–3

31
32 Depositional Setting and Geochemistry of Phosphorites and Metalliferous Black Shales, Northern Alaska

Table 1. Phosphorite localities in the Lisburne Group, northern Alaska. 

[Localities listed from most allochthonous (Kelly River Allochthon) to parautochthonous; within each structural level, localities listed from west to east. In Chandler Lake quadrangle, Skimo thrust sheet localities listed first, followed by Tiglukpuk thrust sheet, and then thrust sheets south of Skimo thrust sheet. Column 1: numbered localities are shown in 

figure 1; field numbers in bold indicate localities investigated for this study, or older stations that yielded samples analyzed for this study. Other field numbers from references in 

Column 9. Collectors (all with U.S. Geological Survey unless stated otherwise): ABe, W. Brosgé; ABo, A. Bowsher; AD, J. Dumoulin; AGr, G. Gryc; AKa, K. Adams (University 

of Alaska, Fairbanks); AKe, B. Kent; AMu, C. Mull (Alaska Division of Geological and Geophysical Surveys [ADGGS]); APa, W. Patton; ASi, J. Siok (University of Alaska, 

Fairbanks); (A)Tr, I. Tailleur; CMD, J. Kurtak and co-workers (U.S. Bureau of Mines); JS, J. Slack; My, B. Murchey; PP, Paige Peapples (now Delaney; ADGGS). Column 3: EMA, 

Endicott Mountains Allochthon; KRA, Kelly River Allochthon; distance below top of Lisburne is to top of phosphorite and black shale or chert interval. Column 5 [and 6-9]: CO, 

conodont sample; GX, geochemical sample; MS, measured section (of entire exposed Lisburne Group, unless stated otherwise); TS, thin section. Rock types are BS, black shale; G, 

grainstone; GP, granular phosphorite; M, mudstone; P, packstone; PG, packstone-grainstone; PL, phosphatic limestone; PN, phosphorite nodule; PR, phosphate rock; W, wackestone; WP, wackestone-packstone. Column 6: Thin section data from J. Dumoulin unless stated otherwise in column 9. Column 7: Conodont data from Anita Harris; radiolarian data 

from Paula Noble; other data from listed sources. CAI, conodont color alteration index. Conodont data sources: (1), Dumoulin and others (2006a); (2), unpublished fossil report; (3), 

Dumoulin and others, 2008. Column 8: values are maxima for each rock type analyzed from locality; see Appendix table A1 for complete geochemical data for sample numbers in 

bold; other geochemical data from Patton and Matzko (1959); Corg, total organic carbon. Column 9, CHMC, conodont heavy mineral concentrate]

1

Locality

no., name 

(field no.)

2

Quadrangle,

latitude N.,

longitude W.

(Sec., T, R)

3

Structural and

stratigraphic

setting 

4

Thickness and

characteristics of

phosphate zone

5

Data base 

6

Thin section

features 

Loc. 1

(00AD04,

JS-00-02)

De Long Mtns. 

B-3 

68°17.370’

163°22.040’

KRA (Wulik Peaks 

plate); uppermost 

Lisburne Group.

~3 m of recessive black shale 

contains radiolarian-bearing phosphorite nodules 3-4 cm in diameter.

1 CO

2 GX (BS, PN; see table A1)

2 TS (BS with small PN, PN)

PN: radiolarians, siliceous and calcareous 

sponge spicules, minor 

barite. 

Loc. 2

(03AD27,

JS-04-23)

De Long Mtns. 

B-1

68°23.662’

162°27.326’

KRA (Amphitheatre 

plate); uppermost 

Lisburne Group.

<15 m of carbonaceous black shale 

interbedded with phosphatic limestone that grades to limy phosphate 

rock; phosphorite nodules to 15 cm 

in diameter. 

1 MS (phosphorite zone only, 

03AD27)

2 CO (1 barren)

5 GX (BS, PN; see table A1)

11 TS (BS, PL, PN, PR)

PN: radiolarians, sponge 

spicules, phosphatic 

clasts, minor barite. 

PR, PL: phosphatic 

peloids > composite 

grains, ooids; phosphatic crust?; bored 

bioclasts.

Loc. 3

(03AD38)

Misheguk Mtn.

 B-5

68°27.627’

161°58.391’

KRA (Kelly plate); 

uppermost Lisburne 

Group.

≤10 m of carbonaceous black shale 

interbedded with phosphatic 

limestone that grades to phosphate 

rock.

1 MS (phosphorite zone only, 

03AD38)

1 CO

3 GX (BS, PL, PR; see table 

A1)

10 TS (BS, PL, PR)

PL, PR: phosphatic 

peloids, a few ooids?, 

partly phosphatized 

and bored bioclasts 

(some borings filled 

with phosphate).

Loc. 4

Mt. Bupto

North side

(90AD54,

05AD56,

JS-05-93;

50ATr160 

near here)

Top (south)

(92AD32-34)

Howard Pass C-3

North side:

68°31.154’

157°30.188’

Top (south):

68°30.660’

157°30.920’

EMA (Ivotuk plate); 

uppermost Lisburne 

Group.

~5-20 m of thinly interbedded mudstone, chert, and dolostone; all 

lithologies are black, phosphatic, 

and intergradational.

50Tr160 is slumped cutbank of calcareous phosphate rock interbedded with black, bituminous shale, 

sooty chert, and fine-grained, fetid 

limestone.

1 MS (92AD33)

2 CO

2 GX (BS; see table A1)

12 TS (BS; also chert, 

dolostone, and mudstone 

that contain 1-2% P2O5)

Chert, dolostone, and 

mudstone contain small 

PN, phosphatic peloids 

and coated grains (with 

1 or 2 layers), radiolarians, spicules.

Loc. 5

Lisburne Ridge

West side

(65Tr75,

92AD31,

CMD 5803;

50ATr61)

East side

(92AD16)

Howard Pass C-2

West side:

CMD, TR:

68°38.070’

156°44.526’

92AD31: 

68°37.967’

156°43.750’

East side:

68°37.400’

156°37.080’

EMA (Ivotuk plate); 

uppermost Lisburne 

Group.

~1.5-2.4 m of thinly interbedded 

dolostone, chert, black shale, and 

granular phosphorite; at least 2 

discrete phosphorite intervals, 

~10-15 cm thick, made up of 2- to 

5- cm-thick beds. 

2 MS (92AD16; Armstrong, 

1970)

3 CO

4 GX (BS, GP; see table A1)

14 TS (BS, GP; also chert, 

dolostone, partly silicified 

WP) 

GP: phosphatic peloids, 

ooids + pisoids (30-

50% of some samples, 

2 >8 layers), notable 

radiolarians, quartz silt; 

matrix is dolomite and 

organic(?) material.

WP: bored bioclasts.
 Tables 1–3 33

7

Age control,

biofacies, CAI

8

Geochemical data

9

Remarks

P2O5 wt % Corg wt %

Conodonts (from skeletal P just below 

phosphorite zone): probable Mississippian age; CAI >2 to 3.5-4 (1). 

30.91 (00AD4A, PN)

9.51 (JS-00-02, BS)

4.41 (JS-00-02, BS) 

2.76 (00AD4A, PN)

Loc. 1, Dumoulin and others (2004); loc. 5, Dumoulin and others 

(2006a).

Conodonts (from skeletal WP ~5 m 

below top of phosphorite zone): early 

Chesterian (late Late Mississippian); 

CAI 2-2.5 (1).

26.22 (03AD27L, PN)

10.12

(JS-04-23A, BS)

3.04 (03AD27A, BS)

1.50 

(03AD27C, PN)

Loc. 15, Dumoulin and others (2004); loc. 94, Dumoulin and others 

(2006a). 

CHMC mainly phosphatic clasts and lesser phosphatized and phosphatic bioclasts.

Conodonts (from skeletal WP ~1 m 

below top of phosphorite zone): early 

Chesterian; CAI 2-2.5 (1). Radiolarians (basal 2 m of overlying Etivluk 

Gp.): late Atokan-Artinskian (middle 

Pennsylvanian-late Early Permian)(2).

14 (03AD38A, PR)

1.5 (03AD38K, PL)

0.92 (03AD38C, BS)

7.68 (03AD38C, BS)

1.25 (03AD38K, PL)

Loc. 17, Dumoulin and others (2004); loc. 116, Dumoulin and others 

(2006a); GX data for 38A, 38K are from J. Dumoulin and J. Slack, 

unpub. data.

CHMC mainly phosphatic and phosphatized rock fragments, minor 

phosphatic brachiopod fragments, and rare glauconitic grains.

Conodonts (from calcareous radiolarite 

interbedded with slightly phosphatic 

chert and dolostone): likely early 

Chesterian; normal marine, gnathodid biofacies; CAI 1-1.5 (2). 

13.7 (50Tr160, PR)

1.42 (JS-05-93, BS)

4.47 (JS-05-93, BS) 50ATr160 (GX) in Patton and Matzko (1959).

See loc. 71, Dover and others (2004) for conodont data from MS.

CHMC mainly phosphatic grains and bioclasts; some fluorite. 

Conodonts (from dolostone at top 

of 1.5-m interval of BS, GP): late 

Meramecian-earliest Chesterian; 

relatively deep water gnathodid 

biofacies; CAI 1-1.5 (2; revised by A. 

Harris 10/04).

26.02 (65Tr75, GP)

7.69 (92AD31H, BS)

15.90 (92AD31A, BS; 

20.15 wt % Corg from 

split of this sample 

analyzed by USGS 

lab in Denver, CO)

3.84 (65Tr75, GP)

See Armstrong (1970) for MS; see locs. 1-3 (Dumoulin and others, 

1993) for more conodont data.

See Kurtak and others (1995) for more phosphorite geochemistry and 

discussion of resource potential.

50Tr61 (GX, TS) in Patton and Matzko (1959) contains large 

dolomite rhombs (confirmed by x-ray analysis) that partly replace 

some phosphatic peloids; many rhombs have ragged edges due to 

solution.
34 Depositional Setting and Geochemistry of Phosphorites and Metalliferous Black Shales, Northern Alaska

1

Locality

no., name 

(field no.)

2

Quadrangle,

latitude N.,

longitude W.

(Sec., T, R)

3

Structural and

stratigraphic 

setting 

4

Thickness and 

characteristics of

phosphate zone

5

Data base 

6

Thin section

features 

Loc. 6

Ivotuk Hills

 West 

South outcrop

(90AD59)

North outcrop

(JS-05-82,

05AD44 [also 

see table 2])

Killik River B-5

South outcrop:

68°28.833’

155°42.750’

North outcrop:

68°28.906’

155°42.703’

EMA (Ivotuk plate); 

upper Lisburne 

Group (probably 

≤10 m below top); 

north outcrop is 

folded, structurally 

complex repeat of 

upper part of main 

Lisburne section to 

south.

North outcrop: ≤3 m (tectonically 

thickened?) of interbedded phosphorite and dark gray shale that 

overlies black fetid dolostone; at 

least 3 normally graded phosphorite beds, 2-8 cm thick; phosphatic 

clasts (to 2 cm in diameter) in 

shale, dolostone.

2 MS (90AD59; 05AD44 of 

phosphorite zone only)

2 CO (1 barren)

3 GX (BS, GP; see table A1)

9 TS (GP, BS, phosphatic 

dolostone)

GP: phosphatic peloids 

dominant, many with 

“wormy” (bored?) 

texture; <5-30% ooids 

(2-7 layers); minor 

composite grains, 

quartz silt, radiolarians, spicules; dolomite 

( ±  calcite?) cement, 

phosphatic(?) mud.

Dolostone: phosphatic 

peloids, ooids.

Loc. 7

Lisburne 1 well

(7,450-15,350 ft 

[also see table 

2]))

Killik River B-5

68°29.133’

155°41.417’

EMA (Ivotuk plate; 

5 distinct thrust 

sheets); uppermost 

Lisburne Group.

Clasts of granular phosphorite seen 

in cuttings ~7-21 m (24-70 ft) 

below top of Lisburne Group (as 

located in Legg, 1983) in plates 1, 

2, 4, and 5. 

5 TS (cuttings) with GP 

[7,450-80 ft (2 ts); 9,710-

40 ft; 13,760-90 ft; 15,320-

50 ft (#2)]

GP: phosphatic peloids, 

coated grains (1-2 layers), composite grains, 

spicules, radiolarians.

Ivotuk Hills 

 East

(05AD42)

Killik River B-5

68°28.423’

155°33.642’

EMA (Ivotuk plate); 

upper Lisburne 

Group.

~1-2 m total section; fine rubble of 

granular phosphorite, phosphatic 

dolostone, and radiolarian chert in 

grassy tundra, between exposures 

of main Lisburne section and overlying Siksikpuk Formation.

4 TS (GP, phosphatic 

dolostone; also radiolarian 

chert, silicified skeletal P)

GP: phosphatic peloids, 

~5% ooids (≤4 layers); 

spicules, radiolarians; 

phosphatic mud matrix 

and phosphatic cement.

Loc. 8

Akmalik Creek 

 East

(05AD65,

~85AMu2 [also 

see table 2]))

Killik River B-2

68°22.055’

154°10.401’

EMA (Killik River 

sequence of Mull 

and others, 1994); 

upper Lisburne 

Group (~15-20 m 

below top).

~17-20 m of black shale, platy 

limestone, and phosphorite (C.G. 

Mull; unpub. field notes, 1985); 

phosphorite layer at least 40 cm 

thick. 

1 MS (C. Mull)

1 CO 

2 GX (GP) 

5 TS (GP)

GP: phosphatic peloids, 

ooids (≤80%); bored 

hardground(?); radiolarians; calcite and 

phosphatic cement.

Okpikruak

 River

(85ASi18;

Petro-Canada section)

Killik River C-1

Siok section: 

68°32.300’

153°28.500’

PC section: 

68°32.355’

153°27.783’

EMA (Okpikruak River sequence of Mull 

and others, 1994); 

upper Lisburne 

Group (~10-20 m 

below top); section 

here <50 m thick 

(fault at base).

 ~15 m of interbedded black sooty 

shale, lime mudstone, peloidal 

phosphorite, and chert (chert beds 

thin and decrease upward); local 

carbonate concretions contain 

radiolarians.

1 CO 

1 GX (BS)

No TS data available. 

Loc. 9

Monotis Creek

(05AD6, 7;

CMD 4518)

Chandler Lake B-5

05AD6: 

68°22.900’

152°51.490’-530’

05AD7:

68°22.800’

152°50.915’

EMA (Skimo thrust 

sheet); top of shale 

and phosphorite unit 

is ~185 ft (~56 m) 

below top of Lisburne Group (Patton 

and Matzko, 1959).

Three distinct phosphorite occurrences here: on both sides of an 

anticline and at a 2nd locality to 

the south. ~7-10 m of interbedded granular phosphorite, black 

shale, and fine-grained carbonate 

(beds and concretions [60 cm max 

diam]); 2-4 phosphatic zones, 30 

cm-3.4 m thick. Beds cannot be 

correlated across 600 m (Patton 

and Matzko, 1959).

8 MS (Brosgé and Reiser 

1951; Patton and Matzko; 

1959; Kurtak and others, 

1995)

1 CO

2 GX (BS, GP; see table A1)

8 TS (BS, GP; also chert, 

dolostone, lime M)

GP: phosphatic peloids> 

ooids, composite 

grains; phosphatic 

crust(?); radiolarians, 

spicules, quartz silt; 

silica> carbonate cement.

BS: abundant phosphatic 

peloids.

Little Chandler 

 Lake

(45AGr21; locs. 

in Brosgé and 

Reiser, 1951) 

Chandler Lake B-5

(several sites, approximately located, in T13S, 

E part R3W and 

W part R2W)

EMA (Skimo thrust 

sheet and 2 others to 

south); ~35 m below 

top of Lisburne 

Group.

Black, medium- to coarse-grained 

oolitic phosphatic rock, in float and 

possibly in place. 

2 MS (Brosgé and Reiser 

1951)

1 GX (GP)

1 TS (GP)

GP: phosphatic peloids, 

ooids (0.5–1.4 mm 

diam) in matrix of 

calcite, dark (organic?) 

material, and purple 

fluorite.

Siksikpuk

 River

(05PP63)

Chandler Lake B-4

68°19.015’

152°20.216’

EMA (Skimo thrust 

sheet); likely ~60-

110 m below top of 

Lisburne Group.

Small phosphorite outcrop in cutbank 

on east side unnamed fork of Siksikpuk River, associated with large 

carbonate concretions.

1 CO

2 GX (GP, see table A1)

1 TS (GP)

GP: phosphatic peloids, 

minor coated grains (1 

layer); abundant quartz 

silt; rare spicules, 

radiolarians.

Table 1. Phosphorite localities in the Lisburne Group, northern Alaska.—Continued
 Tables 1–3 35

7

Age control,

biofacies, CAI

8

Geochemical data

9

Remarks

P2O5 wt % Corg wt %

Conodonts (from dolostone 2 m above 

GP at north outcrop): early

Chesterian; CAI 1-1.5 (2).

See Dumoulin and Harris (1993) for 

conodont data from south outcrop 

(90AD59).

31.56 (JS-05-82B, GP)

2.42 (JS-05-82C, BS)

17.36 (JS-05-82C, BS)

3.22 (JS-05-82B, GP)

North outcrop: 

Kelley and Mull (1995) show phosphorite here.

See Kurtak and others (1995) for more phosphorite geochemistry 

and discussion of mineralogy, extent, and resource potential of 

phosphorite; these authors interpreted host unit as Otuk Formation, 

but conodont data disprove this. 

South outcrop: 

Slump swale on south-facing dip slope exposes upper 5 m of Lisburne 

Group, which is thinly interbedded black limestone, chert, and 

phosphorite (C.G. Mull, written commun., 2005).

Foraminifers indicate an age of late 

Meramecian-early Chesterian (Mamet Zone 14-16) for the phosphatic 

interval in all 4 plates (Legg, 1983).

GP grains in plates 1, 2, and 5 have a matrix of phosphatic(?) mud and 

dolomite cement; those in plate 4 have a matrix of spiculitic chert.

GP here contains 5-10% glauconite grains, and several clasts of glauconitic spiculitic siltstone.

Conodonts (from ~5-8 above top 

of phosphorite interval): early 

Chesterian; relatively shallow to 

moderately deep biofacies; 

CAI 2.5 (2).

36.98 (05AD65K2, GP) 1.52 (05AD65K2, GP) 85AMu2 in C.G. Mull, unpub. field notes, 1985.

Kelley and Mull (1995) show phosphorite here, and suggest “considerable” lateral extent for the phosphorite in the Killik River 

quadrangle. 

Conodonts (from highest exposed 

Lisburne Group): no older than earliest Morrowan (Early Pennsylvanian) 

with redeposited Chesterian forms; 

CAI 1-1.5 (2).

8.84 (BS, J. Lukasic, 

written commun., 

2005)

85ASi18 in J. Siok, unpub. field notes, 1985; other information from 

J. Lukasic and M. McDonough, Petro-Canada Oil and Gas Co., 

2005.

Structurally, rocks are ~on trend with (just north of) Tiglukpuk thrust 

sheet to east and Ivotuk plate to west. Lithologically, they resemble 

rocks of the Killik River sequence of Mull and others (1994).

Conodonts (from 8x30 cm concretion of carbonaceous lime M with 

radiolarians and spicules; GP beds 

occur 1-2 m above and below): early 

Chesterian; deep, anoxic biofacies; 

CAI 1-1.5 (3).

Earliest Chesterian cephalopods from 

phosphatic interval at several localities near here (Gordon, 1957).

19.35 (CMD4518, GP)

7.91 (05AD6E, BS)

15.0 (05AD6E, BS)

1.48 (CMD4518, GP)

Loc. 5, Dumoulin and others (2008).

See Kurtak and others (1995) for 5 MS and data on phosphorite geochemistry, mineralogy, extent, and resource estimate; see Patton and 

Matzko (1959) for 2 MS and Brosgé and Reiser (1951) for 1 MS.

Conodonts in concretion abundant (>500 specimens) but low diversity; many pristine, delicate forms, suggesting deposition via fecal 

pellets.

25.6 (45AGr21, GP) Phosphatic interval occurs in lower Kiruktagiak member of Lisburne 

Group of Brosgé and Reiser (1951), who map it in 3 thrust sheets 

here and show it in 2 MS; 45AGr21 (GX and TS) in Patton and 

Matzko (1959).

Conodonts (from 05PP59C, bioclastic G slightly SE of 63, near top of 

Lisburne Group): Chesterian; CAI 

1.5-2 (3).

20.57 (05PP63CG, GP) 

13.36 (05PP63FG, GP)

3.52 (05PP63CG, GP)

2.25 (05PP63FG, GP) 

Close to loc. 8 (05PP59C, Dumoulin and others, 2008).

Note lower P2O5 + Corg content in more loosely packed rock with 

calcite cement (63FG) versus tightly packed rock with silica cement 

(63CG).
36 Depositional Setting and Geochemistry of Phosphorites and Metalliferous Black Shales, Northern Alaska

1

Locality

no., name 

(field no.)

2

Quadrangle,

latitude N.,

longitude W.

(Sec., T, R)

3

Structural and

stratigraphic 

setting 

4

Thickness and 

characteristics of

phosphate zone

5

Data base 

6

Thin section

features 

Loc. 10 

Confusion 

 Creek

(04AD9, CCP 

[J. Dumoulin 

section]; PetroCanada section)

Chandler Lake B-4

68°17.500’

152°01.061’

EMA (Skimo thrust 

sheet); ~110 m below top of Lisburne 

Group (J. Lukasic, 

written commun., 

2003). 

Ten discrete phosphorite intervals 

(4-40 cm thick) in 8.25-m-thick 

zone within 12 m section of upper 

part of shale and phosphorite unit; 

phosphorites typically cap cycles 

of shale grading up into lime mudstone  ±  chert. Local chert and lime 

mudstone concretions; abundant 

radiolarians, especially in lower 

part of section.

2 MS (Petro-Canada; CCP [J. 

Dumoulin] of phosphorite 

zone only)

1 CO

15 GX (6 BS, 9 GP; see table 

A1)

39 TS: 6 BS, 11 GP, 15 lime 

M, 7 chert

GP: phosphatic peloids 

(some with quartz silt, 

radiolarians, spicules, 

bioclasts), lesser ooids 

(≤10 layers), composite 

grains, nodules. 

Calcite cement in most 

samples; local quartz, 

fluorite, dolomite 

cement.

Loc. 11

Skimo Creek

(03AD2; SKB 

[J. Dumoulin, 

M. Whalen 

section], SKBo; 

see Remarks 

for other sections)

Chandler Lake B-4

SKB: 

68°17.735’

151°54.869’

SKBo:

 68°17.773’

151°54.609’

EMA (Skimo thrust 

sheet); ~170 m below top of Lisburne 

Group.

Shale and phosphorite unit is ~30 m 

thick; contains 5 phosphorite intervals (10-40 cm thick, in upper 9-12 

m of unit) that cap cycles of shale 

grading up into lime mudstone.

Locally abundant carbonate and chert 

concretions contain radiolarians 

and sponge spicules.

5 MS (see Remarks) 

3 CO

6 GX (4 BS [3 Corg only], 2 

GP; see table A1) 

21 TS (4 BS, 6 GP, 2 PL, 4 

lime M, 4 carbonate and 

chert concretions, 1 P)

GP: phosphatic peloids 

(quartz silt), lesser 

ooids (≤10 layers), 

composite grains, 

nodules (to 1 cm 

diam), ?crusts; local 

radiolarians. Matrix: 

calcite, quartz, minor 

fluorite cement; minor 

phosphatic mud.

South 

 Tiglukpuk 

 Creek

(04AD8; CMD 

4617, 75Tr1, 

and 80My7-10

near here) 

Chandler Lake B-4

68°18.180’

151°50.400’

EMA (Skimo thrust 

sheet); ~160 m below top of Lisburne 

Group.

9.8 m of oolitic to pisolitic phosphorite interbedded with black 

shale and limestone; 5 phosphorite 

beds ~5-35 cm thick and several 

thinner beds. Local phosphorite 

nodules (to 2 cm max diam); zone 

of siliceous concretions (to 0.5 x 3 

m) ~6 m below main phosphorite 

interval.

2 MS near here (section SC3 

in Kurtak and others, 1995, 

and section 2 in Patton and 

Matzko, 1959)

6 CO (Tr, My)

2 GX (GP; see table A1) 

3 TS (GP)

GP: phosphatic peloids, 

ooids (1-50%, ≤7 layers), composite grains; 

some layers normally 

graded. Radiolarians, 

elongate shells. Cement: quartz, dolomite 

[8D]; calcite, phosphatic mud [CMD].

Akmagolik 

 Creek

(03AD10; 

50AKe279 near 

here)

Chandler Lake B-3

68°17.860’

151°42.660’

EMA (Skimo thrust 

sheet); probably 

~150 m below top of 

Lisburne Group.

25-30 m of interbedded black shale, 

lime mudstone, and phosphorite 

(several beds, ≤40 cm thick; nodules to 0.5 cm). Minor chert beds 

and nodules; abundant carbonate 

concretions (10-30 cm max diam). 

2 GX (GP; see table A1) 

3 TS (GP, lime M) 

GP: phosphatic peloids 

(some contain abundant quartz silt), lesser 

ooids (2->4 layers); 

calcite, minor fluorite 

cement.

Anaktuvuk 

 River West

(50ABo76; loc. 

in Brosgé and 

Reiser, 1951)

Chandler Lake B-3

(secs. 13 and (or) 

24, T13S, R2E) 

EMA (Skimo thrust 

sheet); ~150->170 

m below top of 

Lisburne Group.

Phosphatic rock similar to that at 

Anaktuvuk River East locality but 

from dipslope on opposite side of 

river.

1 MS (Brosgé and Reiser, 

1951)

1 GX (PR?)

1 TS (PR?)

PR?: phosphatic peloids 

(with abundant quartz) 

and ooids in calcite 

matrix with fluorite and 

carbonaceous matter.

Anaktuvuk

 River East

(50ABo78; near 

Petro-Canada 

loc.)

Chandler Lake B-3

(secs. 28 and (or) 

33, T13S, R3E) 

EMA (Skimo thrust 

sheet?); ≥150 m below top of Lisburne 

Group.

Phosphorite is thin stringers in 

calcareous shale with chert and 

limestone nodules (concretions?); 

~13 m above base of black chert 

and shale member and >800 m 

above base of Lisburne Group. 

1 GX (GP)

1 TS (GP)

GP: phosphatic peloids 

(with abundant quartz) 

and ooids in calcite 

matrix with fluorite and 

carbonaceous matter.

Lawrence

 Livermore 

 Drillholes

(Brosgé and Armstrong, 1977)

Chandler Lake 

B-4 (sec. 26, 

T12S, R1W; 2 

drillholes, 170 

m apart; DH 1 

[west] and DH 2 

[east])

EMA (likely Tiglukpuk thrust sheet); 

~100-120 m below 

top of Lisburne 

Group.

Peloidal phosphorite occurs near 

base of ~20 m of black shaly 

limestone with chert nodules; 

phosphorite in layers 1-1.5 m thick 

(1 layer in DH1, 2 in DH2).

Lithology and geochemistry 

of cuttings reported in 

Brosgé and Armstrong 

(1977)

GP: black phosphatic 

peloids to 1 mm. 

West 

 Tiglukpuk 

 anticline

(05AD2)

Chandler Lake B-4

68°22.595’

151°57.078’

EMA (Tiglukpuk 

thrust sheet); ~110 

m below top of 

Lisburne Group.

Rubble of phosphorite, phosphatic 

limestone, spiculitic chert, and 

lime mudstone (10 cm thick bed) 

overlie skeletal supportstone (with 

bored bioclasts seen in TS).

1 CO

1 GX (GP; see table A1)

13 TS (GP, PL, also spiculitic 

chert, lime M, peloidalskeletal PG) 

GP: phosphatic peloids, 

ooids (≤7 layers), 

nodules (≤7 mm diam); 

spicules, radiolarians. 

Matrix: quartz and 

calcite cement, lime 

and phosphatic mud.

Table 1. Phosphorite localities in the Lisburne Group, northern Alaska.—Continued
 Tables 1–3 37

7

Age control,

biofacies, CAI

8

Geochemical data

9

Remarks

P2O5 wt % Corg wt %

Conodonts (from skeletal PG ~40 m 

above top of shale and phosphorite 

unit): early Chesterian; high energy, 

near- shoal biofacies; CHMC has 

abundant phosphatic clasts and 

bioclasts; CAI 1.5-2 (3).

25.67 (CCP-4.85, GP)

11.54 (CCP-3.4, BS)

9.43 (CCP-3.4, BS; 

Corg values in BS 

increase up section, 

then decrease)

6.73 (04AD9H, GP)

Loc. 4, Dumoulin and others (2008). MS from J. Lukasic and M. 

McDonough, Petro-Canada Oil and Gas Co., 2003. Some phosphorite layers reversely graded; others normally graded. Ooids 

most abundant (30-50%) near middle of section; composite grains 

most notable in upper half of section. One TS from this locality is 

a complex granular phosphorite with 4 distinct layers that differ in 

composition and grain size.

Conodonts (from within, and ~38 m 

above, GP zone): earliest Chesterian; 

sample from lime M in GP zone is a 

winnow into relatively deep water; 

CAI 1 or 1.5-2 (3). Early Chesterian 

cephalopods from just above phosphatic zone (Gordon, 1957).

23.84 (03AD2B, GP)

0.5 (SKBo25, BS)

5.32 (SKBo25, BS; 

see Dumoulin and 

others, 2008 for Corg 

data from 3 BS in 

SKB)

3.78 (03AD2B, GP); 

Loc. 1, Dumoulin and others (2008).

See Patton and Matzko (1959) and Kurtak and others (1995) for MS 

and more on phosphorite chemistry, extent, and resource estimate; 

MS also in Brosgé and Reiser (1951), Armstrong and others (1970), 

and Armstrong and Mamet (1977, 1978).

Black shales examined in TS from this locality contain abundant 

phosphatic peloids and nodules.

Also see table 2.

Conodonts all from limestone beds 

in shale and phosphorite unit; most 

restricted age (80My7C) is early 

Chesterian; CAIs are 1.5, 1-5-2, 

and 2 (2). 

22.04 (CMD 4617-1, 

GP)

30 (GP, Patton and 

Matzko, 1959)

9-15.5 (BS, Kurtak and 

others, 1995) 

3.57 (04AD8D, GP) Loc. 7, Dumoulin and others (2008).

See Patton and Matzko (1959) and Kurtak and others (1995) for MS 

and more on phosphorite chemistry, extent, and resource estimate.

Ro and Tmax data from upper Lisburne Group near here in Johnsson 

and others (1999) and K. Bird, written commun., (2002).

28.62 (03AD 10B, GP)

27.9 (50AKe 279, GP)

1.21 (03AD 10B, GP) Loc. 3, Dumoulin and others (2008); local brachiopods, notable nautiloid cephalopods here.

50AKe279 (GX) in Patton and Matzko (1959) from ~1-1.5 mi north 

(3 mi south of Natvakruak Lake).

 ±  15 (50ABo76, PR?) 50ABo76 (GX, TS) in Patton and Matzko (1959); MS in Brosgé and 

Reiser (1951). 

Late Mississippian (~late Meramecian) 

cephalopods (Gordon, 1957) from 86 

m (282 ft) below top of black chert 

and shale member. 

21.4 (50ABo78, GP) 50ABo78 (GX, TS) in Patton and Matzko (1959); Petro-Canada 

locality a few mi to east (secs. 35 and (or) 36, T13S, R3E; written 

commun., Paige Peapples, 2005). 

Foraminifers from nearby outcrops 

suggest a Meramecian-early 

Chesterian age for these rocks 

(Brosgé and Armstrong, 1977). 

9.41 (DH2, sample 36) Brosgé and Armstrong (1977); P2O5 values from testing with ammonium molybdate; other samples in DH2 had values of 0.74, 2.14, 

and 5.92 wt % P2O5.

Conodonts (from peloidal-skeletal 

PG, likely just below GP): early 

Chesterian; abundant (>700) and 

represent a winnow; CAI 1.5-2 (3). 

21.35 (05AD2C, GP) 1.84 (05AD2C, GP) Loc. 11, Dumoulin and others (2008); similar rocks occur 2 km SW 

at loc. 12. 

One TS from this locality is a complex granular phosphorite with 4-6 

unconformably bounded layers that differ in grading, matrix composition, and phosphatic particle types and sizes.

CHMC contains glauconite and pyrite.
38 Depositional Setting and Geochemistry of Phosphorites and Metalliferous Black Shales, Northern Alaska

1

Locality

no., name 

(field no.)

2

Quadrangle,

latitude N.,

longitude W.

(Sec., T, R)

3

Structural and

stratigraphic 

setting 

4

Thickness and 

characteristics of

phosphate zone

5

Data base 

6

Thin section

features 

North 

 Tiglukpuk 

 Creek

(TNC [M. Whalen, J. Dumoulin section]) 

Chandler Lake B-4

68°21.870’

151°52.440’

EMA (Tiglukpuk 

thrust sheet); ~110 

m below top of Lisburne Group. Main 

phosphorite at TNC 

191.6 m; phosphatic 

limestone from 

189.3-199 m.

Rubble of lime mudstone and granular phosphorite (beds ≤5 cm thick; 

interval ≤1-2 m), overlain by graded skeletal-peloidal supportstone 

(bioclasts variously micritized and 

phosphatized), underlain by lime 

mudstone and spiculitic chert.

1 MS [TNC; part of TN]

1 CO

1 GX (GP, see table A1)

8 TS (GP, PL) 

GP: phosphatic peloids, 

many ooids and pisoids 

(100 μ-4 mm diam, ≤6 

layers); notable quartz 

silt, some bioclasts; 

cement: silica, minor 

calcite and fluorite.

Loc. 12

Shainin Lake

(KW91V [K. 

Watts, J. 

Dumoulin 

section]; Bowsher and Dutro, 

1957)

Chandler Lake B-2

KW91V, 105.6 m:

68°20.3’

151°00.6’ 

EMA (Tiglukpuk 

thrust sheet, or a 

structural level between the Skimo and 

Tiglukpuk sheets, 

W. Wallace, pers. 

commun., 2006); 

~26 m below top 

of Lisburne Group 

(Dumoulin and others, 1997). 

Black chert and shale member of 

Bowsher and Dutro (1957) is ~11-

15 m thick and contains 2 intervals, 

0.75-1 m thick, of interbedded 

grayish brown, calcareous, carbonaceous shale and black phosphorite(?) in thin beds and nodules. 

3 MS (Bowsher and Dutro, 

1957; Armstrong and 

Mamet, 1977; Dumoulin 

and others, 1997)

1 CO

1 TS (skeletal P)

No TS data available on 

phosphorite.

Skeletal P that yielded 

conodonts contains 

bored bioclasts; some 

bioclasts have micritic 

rims.

East and West 

 of Anaktuvuk

 Pass

(Porter, 1966)

Chandler Lake A-3

(SW 1⁄4 T14S, 

R2E; NW 1⁄4 

T15S, R3E)

EMA (unnamed thrust 

sheets south of 

Skimo thrust sheet); 

~243 m below top of 

Lisburne Group.

Middle member of Alapah (75-83 m 

thick) consists of dark, recessive, 

calcareous shale, chert, platy 

limestones, and argillaceous 

phosphorite.

No TS data available. 

“Agiak Lake”

(51APa52, 53; 

51ABe92, 93)

Wiseman D-6

(southern third 

T37N, R23W; 

north of Agiak 

Creek)

EMA (south of Toyuk 

thrust fault); at top of 

Lisburne Group.

Grainy phosphate interval ≤3 m thick 

overlies massive black chert (~5 

m thick) above ~30 m of black, 

locally calcareous shale.

1 MS (Brosgé, unpub. field 

notes)

No TS data available. 

Ekokpuk Creek

(78ABe232, 233; 

84AKa15)

Chandler Lake A-5

AKa15:

68°4.000’

152°45.700’

EMA (south of Toyuk 

thrust fault); near 

top of Lisburne 

Group (78ABe 232); 

~15 m below top 

(78ABe233).

232: ~15 m of black laminated chert 

and sooty limestone with two 

phosphatic, fluoritic intervals.

233: ~15 m of shale with scattered 

phosphate grains; underlies 15 m 

of black limestone and overlies 

15-30 m of black chert.

3 MS (2 in W. Brosgé, unpub. 

field notes; 1 [upper Lisburne Gp. only] in Adams, 

1991).

No TS data available on 

phosphorite.

TS from associated 

lithologies (from K. 

Adams) are spiculite, 

chert, dolostone.

“Ekokpuk Mt.”

(75Tr15.2)

Chandler Lake A-4

(sec 2, T17S, 

R2W [loc. 

approximate, 

near confluence 

of John River 

and Ekokpuk 

Creek])

EMA (south of Toyuk 

thrust fault); 45 m 

below top of Lisburne Group.

~10 m of peloidal phosphorite interbedded with dark limestone (with 

local phosphatic peloids, bioclasts) 

and chert; 2 or 3 graded(?) phosphatic zones (5-20 cm thick) ~3-6 

m above base of interval have 

phosphatic peloids to 1.5 cm diam.

1 MS (I. Tailleur, unpub. field 

notes)

2 CO 

No TS data available. 

Till Creek

(Armstrong and 

Mamet, 1978; 

A. Armstrong, 

unpub. notes)

Wiseman D-4 

(NW 1⁄4 sec. 11, 

T36N, R19W)

EMA (>2 thrust sheets 

south of Soakpak 

Mtn.; south of Toyuk 

thrust fault); ~140 

m below top of 

Lisburne Group.

5-10 m of interbedded chert and lime 

mudstone with abundant blue-gray 

phosphatic pisolites above 32 m 

of thinly interbedded black shale, 

radiolarian chert, and argillaceous, 

spiculitic, locally phosphatic lime 

mudstone. 

1 MS and TS data (Armstrong and Mamet, 1978; 

A. Armstrong, unpub. 

notes)

GP (235, 237 m in MS): 

phosphatic peloids (≤2 

mm diam) in sparry 

calcite matrix.

PL (213, 209 m in MS): 

10-30% phosphatic 

peloids (50-150μ).

Tinayguk River

(Armstrong and 

Mamet, 1978; 

A. Armstrong, 

unpub. notes; 

84AKa1)

Wiseman D-3 

(NE 1⁄4 sec. 35, 

T37N, R16W)

EMA (thrust sheet 

south of sheet that 

contains Alapah 

Mt; south of Toyuk 

thrust fault); ~168 

m below top of 

Lisburne Group.

~30 m of phosphatic lime mudstone 

to skeletal packstone, interbedded 

with black shale and spiculitic 

limestone; megafossils include 

mollusks, cephalopods, pelecypods, and brachiopods. 

2 MS (Armstrong and 

Mamet, 1978; K. Adams, 

unpub. notes)

1 CO

10 TS (PL, lime M, WP, PG 

from K. Adams)

PL  ±  PN at 345, 354, 

356, 372 in MS (A. 

Armstrong, unpub. 

notes); PL [TS from K. 

Adams]: phosphatic 

nodules (3-7 mm 

diam.), radiolarians.

Table 1. Phosphorite localities in the Lisburne Group, northern Alaska.—Continued
 Tables 1–3 39

7

Age control,

biofacies, CAI

8

Geochemical data

9

Remarks

P2O5 wt % Corg wt %

Conodonts (from PL just above GP): 

early Chesterian; abundant (>2000) 

and represent a winnow; CAI 1.5-2 

(3). 

20.62 (TNC 191.6F, 

GP)

2.25 (TNC 191.6F, 

GP)

Loc. 2, Dumoulin and others (2008); chert and phosphorite unit ≥35 

m thick.

Phosphatic peloids here contain notable quartz silt and aggregate 

grains. Skeletal PG just above GP (TNC 208.6 m) contains some 

calcareous ooids. 

CHMC contains abundant phosphatized rock fragments and bioclasts.

Conodonts (from skeletal P ~6 m 

above base of black chert and shale 

member), foraminifers, and goniatite 

cephalopods (G. americanus [was G. 

crenistria]): late Meramecian-early 

Chesterian; CAI 2 (2).

MS, description of phosphorite, cephalopod data: Bowsher and 

Dutro (1957); MS, foraminifer data: Armstrong and others (1970), 

Armstrong and Mamet (1977); additional cephalopod data: Dutro 

(1987); MS: Dumoulin and others (1997).

Diverse conodont assemblage indicates normal-salinity, open-marine 

setting (A. Harris, unpub. fossil report).

Porter (1966, pp. 956 [map], 967 [lithologic description]).

W. Brosgé, unpub. notes; unpub. MS provided by K. Bird. Lisburne 

Group here ~110 m thick; underlies Siksikpuk Fm. (yellow clay at 

base), overlies Kayak Shale; consists of ~70 m of black shale and 

chert above ~40 m of limestone.

Phosphatic intervals at 78ABe 232, 

233 yielded goniatite cephalopod G. 

americanus (late Meramecian-early 

Chesterian) (W. Brosgé, unpub. 

notes).

W. Brosgé, unpub. field notes (1978); unpub. MS provided by K. 

Bird. At 232, ≤21 m of Lisburne Group underlies Siksikpuk Fm.; 

lower 6 m is radiolarian chert; base of section is a fault.

Uppermost Lisburne yielded middle Chesterian foraminifers (Mamet 

Zone 18) at 232 and latest Chesterian goniatites at AKa15 (Dutro, 

1987). 

GP interval yielded late Meramecianearly Chesterian brachiopods but also 

Osagean conodonts (reworked?); 

Mid. Devonian-Early Mississippian 

conodonts occur ~25-50 m below 

GP; CAI 5, 5.5 (2).

I. Tailleur, unpub. field notes (1975); unpub. MS provided by K. Bird. 

Lisburne Group here ~150-155 m thick; underlies Siksikpuk Fm. 

(orange-weathering at base), above Kayak Shale (contact covered); 

consists of ~45 m of limestone above a 10-m-thick phosphatic zone 

above 95 m of cherty limestone, chert, and dolostone.

Foraminifers of early Chesterian 

(Mamet Zone 16s) age 40 m above 

top of GP interval (Armstrong and 

Mamet, 1978).

Thickness, lithologies, and microfacies of phosphatic zone here, as 

described by Armstrong and Mamet (1978), sound very similar to 

that of phosphatic zone at Skimo Creek (loc. 11 above). 

Phosphatic interval yields late Meramecian foraminifers (Armstrong and 

Mamet, 1978) and late Meramecianearly Chesterian conodonts; CAI 

4-4.5 (2).

MS, TS descriptions from Armstrong and Mamet (1978) and A. Armstrong, unpub. notes; MS (phosphatic zone only), TS (examined by 

J. Dumoulin) from K. Adams. Uncertain if these strata are phosphorites or less-phosphatic rocks. Phosphatic nodules in AKa TS made 

up mostly of phosphatic peloids and bioclasts. 
40 Depositional Setting and Geochemistry of Phosphorites and Metalliferous Black Shales, Northern Alaska

Table 2. Less-phosphatic localities in the Lisburne Group, northern Alaska.

[All samples were analyzed for this study unless stated otherwise in column 9. Samples included have ≥1 wt % P2O5, and (or) contain visible phosphate in thin section and (or) conodont 

heavy mineral concentrates. Samples grouped by age and then structural level (structurally highest [Kelly River Allochthon] to lowest [parautochthonous]); within these groupings, listed 

from west to east. Diamond drill hole localities from Red Dog district listed in increasing numeric order. Column 1: numbered localities are shown in figure 1. Collectors (all with U.S. 

Geological Survey unless stated otherwise): ACh, R. Chapman; AD, J. Dumoulin; AKa, K. Adams (University of Alaska, Fairbanks); ALS, A. Strauch (Alaska Division of Geological 

and Geophysical Surveys [ADGGS]); AMu, C. Mull (ADGGS); ASi, J. Siok (University of Alaska, Fairbanks); DDH, diamond drill core samples from deposits in the Red Dog district, 

collected by J. Slack; JS (1991-94), J. Schmidt; JS (2003-05), J. Slack; KE, K. Evans; PP, Paige Peapples (now Delaney; ADGGS). MS, measured section (of entire exposed Lisburne 

Group unless stated otherwise). Column 3: EMA, Endicott Mountains Allochthon; PCA, Picnic Creek Allochthon; KRA, Kelly River Allochthon; distance below top of Lisburne Group 

is to top of phosphatic interval. Akmalik Chert, Kuna Formation, and Tupik Formation are formations of the Lisburne Group. Column 5 [and 6-9]: For most localities, only phosphatic 

GX and TS samples are listed; other GX and TS samples of non-phosphatic lithologies may have been taken at these stations. CHMC, conodont heavy mineral concentrate; CO, 

conodont sample; GX, geochemical sample; TS, thin section. Rock types are BS, black shale; G, grainstone; M, mudstone; P, packstone; PBS, phosphatic black shale; PG, packstonegrainstone, PL, phosphatic limestone; PW, packstone-wackestone. Other abbreviations: abt, abundant; ph, phosphatic. Column 6: Thin section data from J. Dumoulin unless stated 

otherwise in column 9. Column 7 (and 9): Conodont data from Anita Harris; other data from listed sources. CAI, conodont color alteration index. Data sources: (1), unpublished USGS 

fossil report; (2), Dumoulin and Harris (1993); (3), Dumoulin and others (2006a); (4), Dover and others (2004); (5), Dumoulin and others (1993); (6), Dumoulin and others (2008); (7), 

Dumoulin and others (1997); (8) Till and others (2008). Column 8: n.a., not available]

1

Locality no., 

name 

(field no.)

2

Quadrangle,

latitude N.,

longitude W.

3

Structural and 

stratigraphic 

setting

4

Thickness and characteristics of 

phosphatic strata

5

Data base 

6

Evidence for and (or) 

details of phosphate

Phosphatic strata of known or probable 

(06AD22) Misheguk Mt. C-5

68°32.778’

161°48.181’

PCA?; position 

within Lisburne 

Group uncertain.

Phosphatic, skeletal grainstone (1- 

to 8-cm thick platy beds); forms 

1-m-thick lens in section of thinly 

interbedded carbonate and noncarbonate mudstone.

1 CO (22B) 

1 TS (22B: PL)

CHMC: Very abt ph clasts and 

>1500 conodonts.

TS: few-5% ph peloids (200μ1.5 mm diam). 

Loc. 6

Ivotuk Hills

 West 

(90AD59 [MS], 

91JS39 [also 

see table 1])

Killik River B-5

68°28.906’

155°42.703’

EMA (Ivotuk plate); 

lower Lisburne 

Group (Dumoulin 

and Bird, 2002; 

these rocks called 

Kayak Shale by 

Dumoulin and Harris, 1993).

45 m of black shale and mudstone, 

subordinate beds of chert, spiculite, 

and dolostone. Basal 2.1 m has 2 

intervals of supportstone (lower is 

1.5 m thick, upper is 0.5 m thick, 

5-to 10-cm-thick beds) that contain 

tracks and possible mud cracks.

1 CO (59C)

2 GX (39B, C: both BS)

3 TS (59A: lower PG 

[PL]; 59C, CC: upper 

PG [PL])

TS: lower PG has minor 

ph patches; upper PG 

(hardground?) has 5-25% ph 

bioclasts > clasts (irregular 

peloids, ooids?, ≤5 mm diam). 

Loc. 7

Lisburne 1 well

(7,450-15,350 

ft [also see 

table 1])

Killik River B-5

68°29.133’

155°41.417’

EMA (Ivotuk plate; 

5 distinct thrust 

sheets); lower Lisburne Group (unit I 

of Legg, 1983).

Interval of shale, mudstone, quartz 

siltstone to sandstone, and limestone that is locally glauconitic 

and phosphatic; found in plates 

1, 3, 4, and 5; interval thickness 

varies from 9 m (plate 4) to ≤45 m 

(plate 3).

6 TS (cuttings) contain 

PL with ph grains; 2 

in plate 3 (12,390-420, 

510-540 ft) and 4 in 

plate 5 (16,270-310 ft).

Additional cuttings data in 

Legg (1983).

TS (cuttings) from unit I in plates 

3 and 5 contain skeletal P, G 

with notable phosphatic bioclasts and clasts (like those in 

90AD59C described above).

1

Locality

no., name 

(field no.)

2

Quadrangle,

latitude N.,

longitude W.

(Sec., T, R)

3

Structural and

stratigraphic 

setting 

4

Thickness and 

characteristics of

phosphate zone

5

Data base 

6

Thin section

features 

Lisburne 

 Peninsula

(Section 68A-9; 

Armstrong and 

Mamet, 1977)

Point Hope C-2

(NW 1⁄4 sec. 33, 

T8S, R60W; 

S side of Cape 

Lewis) 

Parautochthonous 

(Young, 2004) or 

EMA (Lisburne Hills 

sequence; Mayfield 

and others, 1988); 

~792-914 m (2,600-

3,000 ft) below top 

of Lisburne Group.

Phosphatic nodules in shale, limestone, and sandstone ~30-60 m 

(100-200 ft) and 182 m (600 ft) 

above base of Lisburne Group, in 

lower part of Nasorak Fm.

1 MS and TS data (Armstrong and Mamet, 1977)TS data (in Armstrong 

and Mamet, 1977) 

indicates phosphatic 

rocks are interbedded 

with glauconitic P and 

spiculite.

Loc. 13

Ikpikpuk 1 well

(14,600-650 ft)

Teshekpuk B-3

70°27.333’

154°19.883’

Arctic Slope parautochthon (Young, 

2004); ~990.6 m 

(3,250 ft) below top 

of Lisburne Group.

Phosphatic grains in cuttings 

from 14,600-14,650 ft (~15 m 

thick zone) associated with dark 

mudstone, spiculite, and muddy 

skeletal packstone.

4 TS (cuttings) with GP 

[14,600 ft, 14,610 ft, 

14,630 ft, and 14,640 ft]

GP: peloids, ooids(?), 

rare quartz sand and 

bioclasts; calcite cement.

Table 1. Phosphorite localities in the Lisburne Group, northern Alaska.—Continued
 Tables 1–3 41

7

Age control, biofacies, CAI

8

Geochemical data

9

Remarks

P2O5 wt % Corg wt %

Osagean (late Early Mississippian) age

Conodonts (from 22B): middle Osagean (Sc. anchoralis-D. latus Zone); 

mixed biofacies; CAI 2.5-3 (1).

Grainstone layer may be a turbidite; highly irregular shape 

of some ph clasts suggests they may have been deposited 

while semi-lithified; some ph clasts contain quartz silt.

Conodonts (from upper PG): early 

Osagean; derived from a range of 

shelf environments; fauna has mix 

of traits characteristic of both Kuna 

Formation and Kayak Shale; CAI 

1.5 (1, 2).

No GX from phosphatic 

rocks.

39B: 1.38

39C: 1.31

Conodont data (Dumoulin and Harris, 1993) suggest possible 

unconformity between early Osagean strata (called Kayak 

Shale by these authors) and overlying late Meramecian 

strata (lower unit of Lisburne Group of these authors). 

39C GX data are intermediate between those typical of Kayak 

Shale and Kuna Formation.

Foraminifers indicate that this interval 

in all plates is of Mamet Zone 

12/13 age (Osagean-Meramecian 

boundary; Legg, 1983).

These rocks may be low-stand deposits (above an unconformity) and may represent a hardground and (or) exposure 

surface. Core 18 spans the unit I/J boundary; the mixed 

age fauna from this core (Dutro and Silberling, 1988) may 

reflect older forms reworked along the unconformity.

7

Age control,

biofacies, CAI

8

Geochemical data

9

Remarks

P2O5 wt % Corg wt %

Foraminifers indicate an age of early 

Chesterian (Mamet Zone 16) for both 

phosphatic zones.

Armstrong and Mamet (1977; see plates 40, 41). Uncertain if these 

strata are phosphorites or less-phosphatic rocks. Stratigraphic 

position near base of Lisburne Group is like that of phosphorite in 

Ikpikpuk well.

Foraminifers indicate an age of early 

Chesterian (Mamet Zone 16) for the 

phosphatic interval (Dumoulin and 

Bird, 2001).

Phosphatic interval occurs near top of lower limestone unit of Dumoulin and Bird (2001, p. 148).
42 Depositional Setting and Geochemistry of Phosphorites and Metalliferous Black Shales, Northern Alaska

Table 2. Less-phosphatic localities in the Lisburne Group, northern Alaska.—Continued

1

Locality no., 

name 

(field no.)

2

Quadrangle,

latitude N.,

longitude W.

3

Structural and 

stratigraphic

setting

4

Thickness and characteristics of 

phosphatic strata

5

Data base 

6

Evidence for and (or) 

details of phosphate

 Phosphatic strata of known or probable middle or late Meramecian-early Chesterian (Late Mississippian) age; 

(04AD39) De Long Mts. A-3

68°13.725’

163°13.020’

KRA (?Wulik Peaks 

plate); uppermost 

Lisburne Group.

At least several meters of crinoidalbrachiopod packstone-wackestone, 

locally dolomitic, glauconitic, and 

phosphatic.

1 CO (39A)

3 TS (39A, D, E: all PL).

CHMC: abt ph bioclasts. TS 

(PL): ≤15% ph bioclasts (some 

bored), clasts, nodules (≤2 

mm).

(06AD21) Misheguk Mt. C-5

68°32.447’

161°41.036’

KRA (Kelly plate); 

highest exposed 

Lisburne Gp. 

(rubble), overlain 

by 2 m of grassy 

cover, then rubble 

of Siksikpuk Fm.

2 rubbly layers, each several dm 

thick, of crinoidal supportstone (in 

irregular, 5-cm-thick beds) with 

≤5% black phosphatic grains.

1 CO (21C)

4 TS (21C-E, CC: all PL)

PL (4 TS) contains ph peloids, 

rare composite ph grains, and 

partly ph bioclasts.

(99AD19) De Long Mts. B-2

68°21.933’

162°49.908’

PCA (Wulik plate); 

highest carbonate 

bed in Lisburne 

Group; underlies 

grassy swale with 

float of black silicified mudstone.

0.5-m-thick irregular outcrop of 

crinoidal grainstone with 3- to 

4-mm-long black mud clasts; many 

bioclasts partly or totally replaced 

by phosphate.

1 CO (19D)

1 TS (19D: PL)

CHMC: ph composite grains, 

bioclasts, and steinkerns.

TS (PL): 10-25% ph clasts, 

bioclasts, patches (≤1.7 mm 

diam).

Stack barite 

 deposit

(05AD50)

Howard Pass C-3

50F: 68°36.056’

157°30.160’

50L: 68°36.031’

157°36.032’

PCA; Akmalik Chert. Layer (~0.5 m thick) of distinctive, 

lightweight, silver-weathering, 

phosphatic “oil shale” (interbedded 

with radiolarian chert, calcareous 

radiolarite); underlies barite.

1 CO (91TR23)

2 TS (50F, L: both “oil 

shale”)

“Oil shale” in TS: ph clasts (60-

300μ, ovoid to elongate) are 

10-15% in 50F, few % in 50L.

Bion barite 

 deposit

(05AD51, 

91JS31)

Howard Pass C-3

68°37.032’

157°30.160’

PCA; Akmalik Chert. Distinctive, lightweight, silverweathering, phosphatic “oil shale” 

(interbedded with radiolarian chert 

and calcareous radiolarite) in rubble 

and subcrop; underlies barite.

1 CO (91Tr17)

1 GX (31D: “oil shale”)

2 TS (31D, 51C: both “oil 

shale”)

“Oil shale” in TS: ph clasts (60-

200μ, ovoid to elongate) are 

10-20% in 31D and abt in 51C.

(94JS17) Howard Pass C-5

68°33.132’

158°44.316’

EMA (Key CreekAniuk plates); 

near top of Kuna 

Formation. 

Platy black shale (beds <5 cm thick, 

laminae <1 mm), yellow bloom on 

weathering surface.

1 GX: (17T: PBS) GX only; no TS data. 

(94JS19) Howard Pass C-5

68°33.636’

158°38.586’

EMA (Key CreekAniuk plates); 

Kuna Formation.

Black siliceous mudstone without 

obvious coarser-grained layers.

1 GX (19A: PBS) GX only; no TS data. 

(94JS7) Howard Pass B-4

68°20.484’

158°09.666’

EMA (Key CreekAniuk plates); 

Kuna Formation 

above Kayak Shale.

Black sooty shale (laminae ≤5 mm 

thick).

1 GX (7A: PBS) GX only; no TS data. 

(92AD74,

JS-05-96)

Howard Pass B-3

68°19.500’

157°43.830’

EMA (Key CreekAniuk plates); 

Kuna Fm. (74: 

near top of formation; 96: position 

unknown).

74 is black, platy, silty mudstone 8 

m below contact with Siksikpuk 

Fm.; 96 is black mudstone from 

lower(?) in section.

2 GX (74C, 96: both PBS)

1 TS (74C: PBS)

74C TS: abt quartz silt, ≤10% 

ph bioclasts and clasts (most 

irregular, silt-sized).

(94JS9) Howard Pass B-3

68°26.286’

157°40.632’

EMA (Key CreekAniuk plates); 

upper part of Kuna 

Formation.

H, K: spiculitic, cherty mudstone 

interbedded with bioturbated limestone ~5 m below top of Lisburne 

Group; L: chert ≥20 m lower.

3 GX (9H, K, L: all PBS) GX only; no TS data. 

(JS-05-94,

05AD57)

Howard Pass C-3

68°31.000’

157°35.695’

EMA (Key CreekAniuk plates); 

Kuna Formation. 

Black sooty shale (94) interbedded 

with dolostone (57A) and chert 

(57D).

1 GX (94; no TS match)

2 TS (57A, D)

57A TS: few % ph clasts and 

bioclasts to 2 mm diam.

(93JS7) Howard Pass B-2

68°19.668’

156°55.536’

EMA (Key CreekAniuk plates); 

Kuna Formation 

above Kayak Shale. 

Black, sooty, laminated shale associated with gray bioturbated 

limestone. 

2 GX (7C, J: both PBS) GX only; no TS data. 
 Tables 1–3 43

7

Age control, biofacies, CAI

8

Geochemical data

9

Remarks

P2O5 wt % Corg wt %

some samples from Kuna Formation could be older (Osagean?, late Early Mississippian)

Conodonts (from PL): late Meramecian-early Chesterian; outer shelf or 

deeper; CAI 2 (3). 

Loc. 8, Dumoulin and others (2006a). 39A from uppermost 

Lisburne Gp. (beds 10-30 cm thick); D, E from distinctive 

yellow-weathering interval, with platy beds (1-2 cm thick), 

2-4 m lower in section.

Conodonts (from PL): Mississippian 

(likely Late Mississippian); CAI 

2.5-3 (1).

Grassy zone may be underlain by shale.

CHMC is chiefly phosphatized composite grains, crinoid columnals, and tube fillings, plus phosphatic shell fragments.

Conodonts (PL): early Chesterian or 

younger (with re-worked Osagean 

forms); lag concentrate with mix 

of mostly outer-shelf to off-shelf 

forms; CAI 2.5 (3).

Loc. 35, Dumoulin and others (2006a). In TS, see one composite grain made of smaller phosphatic peloids, at least 

some of which are coated grains (1-2 layers).

Conodonts (from calcareous radiolarite layer in the barite body): late 

Osagean-Meramecian (probably 

middle Meramecian); 

CAI 1.5-2 (4).

Loc. 40, Dover and others (2004). 

Conodonts (from limy layer in barite): 

Mississippian; CAI 1.5-2 (4). 

31D: 1 31D: 22 Loc. 30, Dover and others (2004); Slack and others (2004d). 

Ph bioclasts? (≤1 mm diam) in 31D TS; trace glauconite? 

in 51C TS.

Chert (25 m above 91Tr17) contains Late Mississippian-Early 

Pennsylvanian radiolarians (4).

No age control here, but sample from 

upper part of Kuna Fm.

1.38 n.a. Slack and others (2004d). Drenchwater area.

No age control here. 1.02 n.a. Slack and others (2004d). Drenchwater area.

No age control here. 3.68 n.a. Slack and others (2004d).

Conodonts (8 m below top of nearby 

section 92AD35): late OsageanMeramecian; CAI 3 (4).

74C: 5.59

96: 3.36

74C: 8.4

96: 5.41

Type section of Kuna Fm., loc. 146, Dover and others (2004); 

Slack and others (2004d). Other TS from beds a few meters 

above and below 74C are mudstone with silt, radiolarians, 

and (or) spicules.

No age control here. H: 5.60

K: 1.31

L: 1.68

n.a. Slack and others (2004d).

91Tr05b near here: Silurian-Permian 

conodonts; CAI 1.5-2) (4).

1.24 11.02 J. Slack, unpub. GX data (2008).

No age control here. 7C: 3.15 

7J: 2.69

7C: 6.38

7J: 6.58

Slack and others (2004d). Near Kuna Basin-carbonate platform transition.
44 Depositional Setting and Geochemistry of Phosphorites and Metalliferous Black Shales, Northern Alaska

Table 2. Less-phosphatic localities in the Lisburne Group, northern Alaska.—Continued

1

Locality no., 

name 

(field no.)

2

Quadrangle,

latitude N.,

longitude W.

3

Structural and 

stratigraphic

setting

4

Thickness and characteristics of 

phosphatic strata

5

Data base 

6

Evidence for and (or) 

details of phosphate

(92AD9) Howard Pass C-2

68°36.666’

156°45.414’

EMA (Key CreekAniuk plates); 

Kuna Formation.

Sooty mudstone with dolostone beds 

(and concretions?).

2 GX (9B, C: [P]BS)

2 TS (9B, C: [P]BS)

9B TS: mudstone with ≤10% 

orange ph clasts (200-400μ 

diam).

(91JS19) Howard Pass B-1

68°20.682’

156°06.336’

EMA (Key CreekAniuk plates); 

Kuna Formation.

Sooty, platy, locally phosphatic 

black shale; stratigraphic position 

within Lisburne Group uncertain.

1 GX (19B: PBS)

1 TS (19B: PBS)

TS is spiculitic shale with few % 

ph bioclasts and clasts.

(91JS20) Howard Pass B-1

68°21.300’

156°03.834’

EMA (Key CreekAniuk plates); 

Kuna Formation. 

Cherty section with rare shaly, locally phosphatic? laminae (1-3 mm 

thick).

1 GX (20C: PBS) GX only; no TS data. 

(91AD1 [MS],

91JS4)

Killik River B-5

68°19.800’

155°30.916’

EMA (Key CreekAniuk plates); 

Kuna Formation 

(23.5 m above 

Kayak Sh., upper 

contact of Kuna 

Fm. not exposed 

here.)

Siliceous, phosphatic mudstone 

with thin, clast-rich layers; local 

spicules, radiolarians, and evidence 

of bioturbation.

2 CO

2 GX (1B-3.0, 4G: both 

PBS)

2 TS

No TS match GX, but TS from 

~0.4 m below, and 1.7 m 

above, 1B-3.0 have abt ph? 

mud clasts (0.3-1 mm diam).

Oolamnagavik 

 River

(50ACh55)

Killik River B-3

(NW 1⁄4 T11S, 

R11W)

EMA (Key CreekAniuk plates); 

Kuna(?) Formation.

~9 m of black shaly siltstone with 

beds and concretions (0.3-1 m 

diam) of petroliferous limestone.

1 GX (55)

1 TS (55)

TS: quartz siltstone with carbonaceous cement and a few ph 

nodules.

(99AD4 

[MS]; near 

98AD10)

De Long Mts. A-2

68°14.340’

162°54.85’

EMA (Red Dog 

plate); Kuna 

Formation (chertrich upper part of 

Ikalukrok unit).

≥15 m of interbedded chert, siliceous 

mudstone, and carbonate rocks 

(including calcareous radiolarite).

2 CO (98AD10A, 8-16-

83C)

1 GX (4L)

1 TS (4L)

TS: siliceous mudstone with 

crystalline apatite, minor spicules and radiolarians.

Shear Creek

(JS03-1B, 

03AD20)

De Long Mts. A-2

68°08.073’

162°47.85’

EMA (Red Dog 

plate); Kuna Formation (Ikalukrok 

unit).

Black shale. 1 GX (JS03-1B) GX only; no TS data. 

(DDH 551A, 

88.5 ft)

De Long Mts. A-2

68°04.609’

162°50.320’

EMA (Red Dog 

plate); Kuna Fm. 

(Ikalukrok unit); 

Aqqaluk deposit.

Siliceous black shale with fluorapatite and pyrite laminae.1 GX (88.5 ft) GX only; no TS data. 

(DDH 552, 

624.5 ft)

De Long Mts. A-2

68°04.644’

162°49.706’

EMA (Red Dog 

plate); Kuna Fm. 

(Ikalukrok unit); 

Aqqaluk deposit.

Black shale with pyrite laminae, 

minor sphalerite and galena.

1 GX (624.5 ft) GX only; no TS data. 

(DDH 806, 

1,866.5, 

2,305 ft)

De Long Mts. A-2

68°09.688’

162°57.344’

EMA (Red Dog 

plate); Kuna Fm. 

(Ikalukrok unit); 

Anarraaq deposit.

1866.5: siliceous black shale; 2305: 

black shale with pyrite and fluorapatite.

2 GX (1,866.5, 2,305 ft) GX only; no TS data. 

(DDH 809, 

2,006-

2,427 ft)

De Long Mts. A-2

68°09.688’

162°57.745’

EMA (Red Dog 

plate); Kuna Fm. 

(Ikalukrok unit); 

Anarraaq deposit.

2,006, 2,275.5: black shale with 

pyrite and minor sphalerite; 2,079: 

calcareous lithic turbidite; 2,288, 

2,295: black shale; 2,363.5: black 

shale with abundant pyrite, minor 

sphalerite, and fluorapatite; 2,427: 

black shale with pyrite, sphalerite, 

galena, and fluorapatite.

7 GX (2,006, 2,079, 

2,275.5, 2,288, 2,295, 

2,363.5, 2,427 ft)

1 TS (2,079 ft)

TS from lithic turbidite (2079 ft) 

contains notable phosphatic 

clasts.

(DDH 812, 

1,981 ft)

De Long Mts. A-2

68°09.583’

162°58.533’

EMA (Red Dog 

plate); Kuna Fm. 

(Ikalukrok unit); 

Anarraaq deposit.

Calcareous lithic turbidite. 1 GX (1,981 ft) No TS match GX, but see 

Remarks.

(DDH 924, 

2,169.5, 

2,197.5 ft)

De Long Mts. A-2

68°09.810’

162°57.544’

EMA (Red Dog 

plate); Kuna Fm. 

(Ikalukrok unit); 

Anarraaq deposit.

2,169.5: black shale with pyrite and 

sphalerite; 2,197.5: siliceous, semimassive pyrite with fluorapatite.

2 GX (2,169.5, 2,197.5 ft) GX only; no TS data. 
 Tables 1–3 45

7

Age control, biofacies, CAI

8

Geochemical data

9

Remarks

P2O5 wt % Corg wt %

No age control here. 9B: 1.20 9B: 5.39

9C: 4.84 

Slack and others (2004d). Near Kuna basin-carbonate platform transition. 9B TS much like samples from Mt. Bupto 

(loc. 4, table 1) and 91JS31D (Bion barite deposit, above).

Conodont sample here (19A) was 

barren.

4.68 5.54 Loc. 10, Dumoulin and others (1993); Slack and others 

(2004d). Near Kuna Basin-carbonate platform transition.

No age control here. 2.73 4.55 Slack and others (2004d). Near Kuna Basin-carbonate platform transition; chert beds near GX sample contain minor 

radiolarians and spicules.

Conodonts (from 12.25 m and 21 m 

above base of section): OsageanMeramecian; CAI 3 (5). 

1B-3.0: 3.89

4G: 1.58

1B-3.0: 5.01

4G: 3.98

Loc. 14, Dumoulin and others (1993); Slack and others 

(2004d). 1B-3.0 from ~20 m below top of Kuna Fm.; 4G 

from “upper Kuna Formation.” Locality is close to Kuna 

Basin-carbonate platform transition.

No age control here. 1.4 TS and GX from Patton and Matzko (1959); location approximate. 

Combination of conodont and radiolarian data here restricts age to early 

Chesterian; CAI~3, 4 (3).

2.25 1.37 Loc. 3, Dumoulin and others (2004); loc. 41, Dumoulin and 

others (2006a); Slack and others (2004d).

No age control on 

Ikalukrok unit here.

2.91 3.96 Slack and others (2004d).

No age control here. 1.51 1.01 Slack and others (2004c); see also fig. 8, Slack and others 

(2004b).

No age control here. 1.06 7.49 Slack and others (2004c); see also fig. 9, Slack and others 

(2004b).

No age control here. 1,866.5: 1.24

2,305: 2.44

1,866.5: 3.98

2,305: 5.42

Slack and others (2004c); see also fig. 10, Slack and others 

(2004b).

No age control here. 2,006: 1.09

2,079: 1.43

2,275.5: 1.02

2,288: 1.18

2,295: 1.01

2,363.5: 5.44

2,427: 6.11

2,006: 2.73

2,079: 0.96

2,275.5: 2.71

2,288: 1.88

2,295: 1.72

2,363.5: 3.15

2,427: 1.53

Slack and others (2004c); see also fig. 11, Slack and others 

(2004b).

No age control here. 1.63 2.26 J. Slack, unpub. data (2004). TS from similar turbidite <1 m 

higher (1.978.5 ft) has phosphatic clasts (≤1 mm diam) that 

contain radiolarians.

No age control here. 2,169.5: 1.19

2,197.5: 2.78

2,169.5: 3.77

2,197.5: 3.20

Slack and others (2004c).
46 Depositional Setting and Geochemistry of Phosphorites and Metalliferous Black Shales, Northern Alaska

Table 2. Less-phosphatic localities in the Lisburne Group, northern Alaska.—Continued

1

Locality no., 

name 

(field no.)

2

Quadrangle,

latitude N.,

longitude W.

3

Structural and 

stratigraphic

setting

4

Thickness and characteristics of 

phosphatic strata

5

Data base 

6

Evidence for and (or) 

details of phosphate

(DDH 942, 

1,912.5 ft)

De Long Mts. A-2

68°09.891’

162°57.736’

EMA (Red Dog 

plate); Kuna Fm. 

(Ikalukrok unit); 

Anarraaq deposit.

Calcareous gray shale. 1 GX (1912.5 ft) No TS match GX, but see 

Remarks.

(KE98-25) De Long Mts. A-2

68°07.000’

163°08.600’

EMA (Wolverine 

Creek plate; Rok 

window); top of 

Lisburne Group.

Dolomitic, silicified skeletal grainstone with local vugs that contain 

dead oil.

1 CO (25A) CHMC: Abt ph composite grains 

and bioclasts.

(00AD21) De Long Mts. A-2

68°05.900’

163°06.950’

EMA (Wolverine 

Creek plate; Rok 

window); ~10 

m below top of 

Lisburne Group.

Dolostone with chert and relict 

crinoidal debris.

1 CO (21A) CHMC: notable ph bioclasts and 

steinkerns.

(KE98-27) De Long Mts. A-2

68°12.598’

162°52.800’

EMA (Wolverine 

Creek plate; Mt. 

Raven window); 

position within 

Lisburne Group 

uncertain.

Partly silicified dolostone with local 

vugs that contain dead oil.

1 CHMC (27)

1 TS (27: dolostone)

CHMC: ph bioclasts. 

TS: minor intercrystalline ph(?) 

material.

(99AD13) De Long Mts. A-2

68°13.470’

162°50.473’

EMA (Wolverine 

Creek plate; Mt. 

Raven window); 

highest carbonate 

bed in Lisburne 

Group.

Carbonate bed is fine-grained, 

organic-rich dolostone with peloids 

and rare bioclasts; underlies a few 

meters of black chert.

1 CO (13I)

1 TS (13I: phosphatic 

dolostone)

CHMC: abt ph peloids, composite grains, and steinkerns.

TS: few % ph clasts.

 Phosphatic strata of known or probable late early-late Chesterian (late Late 

(06AD27) Misheguk Mt. C-4

68°33.120’

161°12.200’

KRA; uppermost 

Lisburne Group 

(uppermost Tupik 

Formation).

35-cm-thick layer of phosphatic 

crinoidal supportstone is highest 

exposed Lisburne Group here.

1 CO (27L)

5 TS (27 G, H, I, J, L: all 

are GP with minor ph)

CHMC: abt conodonts, (>900), 

ph bioclasts.

TS: minor ph, bored bioclasts, 

micritic clasts.

(05AD64) Killik River B-3

68°122.839’

154°12.404’

PCA; basal unit of 

Imnaitchiak Chert 

(unit F of Siok, 

1985) just above 

Akmalik Chert.

Silicified oncolitic grainstone, with 

local phosphate, glauconite, and 

barite; layer ≤50 cm thick; oncolites ≤11 cm in diam.

2 TS (64D, 04ADonc: 

both are oncolitic G 

with ph)

TS: minor ph as clasts (≤4 mm), 

matrix, and replacing and filling radiolarian tests.

Loc. 6

Ivotuk Hills

 West (top of 

south section)

(85ASi14-18, 

92AD41, 

05AD58 [see 

table 1])

Killik River B-5

68°28.600’

155°42.500’

EMA (Ivotuk plate); 

uppermost Lisburne Group.

10 m of outcrop (dipslope; ~4? m 

section) of bioturbated siliceous 

spiculite interbedded with siltstone 

and silty mudstone, beds even to 

nodular, 2-15 cm thick; overlies 

30-50 m of cover above top of 

main Ivotuk section (90AD59); 

Siksikpuk Formation exposed in 

nearby scarp.

2 CO (Si14-18; 41A)

8 TS (41A-C, AA; 58AD)

TS: minor ph clasts, bioclasts 

(and glauconite clasts) in silty 

mudstone (58A), siliceous and 

(or) calcareous spiculite (41A, 

AA, 58B-D), and quartz-carbonate siltstone (41B).

Loc. 6

Ivotuk Hills

 West (top of 

north section)

(05AD44 [see 

table 1])

Killik River B-5

68°28.906’

155°42.703’

EMA (Ivotuk plate); 

uppermost Lisburne Group.

Uppermost 6-10 m of section are 

green-gray, glauconitic, carbonate 

siltstone in undulatory beds 1-40 

cm thick; abundant trace fossils 

include Zoophycus.

1 CO (44N)

12 TS (44S, W: ph 

dolostone; 44E, K, L, 

N, P, R, T; Ivo-0, -3, -4: 

slightly ph dolostone 

[44N has spicules; 44P, 

Ivo-4 have quartz silt])

TS: 5-25% ph peloids, ≤15% 

glauconite in 44S, W; others 

have minor ph and glauconite; 

a few ph ooids in 44L, S; ph 

nodules (>1.3 cm diam) in 

44T.
 Tables 1–3 47

7

Age control, biofacies, CAI

8

Geochemical data

9

Remarks

P2O5 wt % Corg wt %

No age control here. 1.16 0.85 Slack and others (2004c). TS (1,908.8 ft) from 1.5-m-thick 

turbidite that begins immediately above this shale contains 

notable (≤5%) phosphatic clasts.

Conodonts (from dolomitic G): 

Chesterian; outer shelf or deeper; 

CAI 2.5 (3).

Loc. 14, Dumoulin and others (2004); loc. 73, Dumoulin and 

others (2006a).

Conodonts (from dolostone): very 

early Chesterian; shallow-water, 

near high-energy setting; CAI 3.5-4 

(3).

Loc. 15, Dumoulin and others (2004); loc. 75, Dumoulin and 

others (2006a).

Conodont sample from this locality 

was barren (3). 

Loc. 44, Dumoulin and others (2006a).

Conodonts (from ph dolostone): late 

Meramecian-early Chesterian; 

slope setting; CAI 4 (3).

Loc. 4, Dumoulin and others (2004); loc. 42, Dumoulin and 

others (2006a).

Ph clasts and bioclasts in TS mostly 140-400 μ diam; clasts 

rounded to ovoid.

Mississippian) and (or) very earliest Morrowan (early Early Pennsylvanian) age

Conodonts (27L): late Chesterianmiddle Morrowan (with redeposited 

late Early and early Late Mississippian forms); CAI 3-3.5 (1).

Akmalik Chert is Early-Late Mississippian (Blome and others, 1998).Radiolarians of Meramecian-Chesterian age occur below unit 

F; radiolarians of Morrowan (to Chesterian?) age occur 

above unit F (Siok, 1985).

Conodonts (Si14-18, “gray-black 

micrite to sparite, 11 m below top 

of Lisburne,” J. Siok unpub. notes, 

1985): latest Chesterian; CAI 1.5 

(2).

41A (siliceous spiculite with minor glauconite, matrix of mud 

and carbonate, 1 m below top of outcrop) yielded conodont 

fragments of indeterminate age, CAI 1-1.5; CHMC is 

chiefly fluorite, phosphatized composite grains, and probable pyrite.

Lithologies here similar to SKA 219-221 (Skimo Creek section; see below) but conodonts are older.

Conodonts (from dolostone 2 m 

above ph rocks): early Chesterian? 

(if single element of B. utahensis

in this fauna is reworked, sample 

could be of younger Chesterian 

age); CAI 1-1.5 (1).

Lithologies here resemble those of SKA 187, 219-221 

(Skimo Creek section), suggesting late early Chesterian (or 

younger) age.

CHMC contains abundant phosphatized composite grains 

(including some bioclasts) as well as phosphatic brachiopod 

fragments.
48 Depositional Setting and Geochemistry of Phosphorites and Metalliferous Black Shales, Northern Alaska

Table 2. Less-phosphatic localities in the Lisburne Group, northern Alaska.—Continued

1

Locality no., 

name 

(field no.)

2

Quadrangle,

latitude N.,

longitude W.

3

Structural and 

stratigraphic

setting

4

Thickness and characteristics of 

phosphatic strata

5

Data base 

6

Evidence for and (or) 

details of phosphate

Loc. 8

Akmalik Creek

 East

(05AD65

~85AMu2 [see 

table 1])

Killik River B-2

68°22.055’

154°10.401’

EMA (Killik River 

sequence of Mull 

and others, 1994); 

~5-6 m below top 

of Lisburne Group.

4-5 m of dark-weathering skeletal 

packstone-wackestone, beds 5-25 

cm thick; uppermost ≥10 cm of 

this interval contains notable glauconite and phosphate.

1 CO (Mu2-10)

4 TS (65D: glauconitic 

P; 65E: glauconitic ph 

quartz sandstone 

(hardground?); 65F, G: 

glauconitic ph PW)

TS: 65E (highest) has 30-40% 

glauconite, 20-30% ph clasts 

(peloids, a few ooids) and 

nodules; 65F, G have ≤5% ph 

clasts and bioclasts.

(05AD8; 

05PP22 very 

near here)

Chandler Lake B-4

68°16.905’

152°11.621’

EMA (unnamed 

thrust sheet just 

south of Skimo 

thrust sheet); upper 

Lisburne Group.

35-cm-thick bed of crinoidal supportstone (with ≤10% glauconite) 

overlain by 6-8 m of dark, laminated mudstone.

1 CO (8C)

2 TS (8C, 22: PL)

TS: minor ph grains (8C); 2 

partly ph nodules (≤2 mm 

diam; 22).

Northwest

 Soakpak Mt. 

(04AD13)

Chandler Lake A-4

68°11.728’

151°53.967’

EMA (unnamed 

thrust sheet south 

of Skimo thrust 

sheet); upper Lisburne Group.

Outcrop and rubble of skeletal 

supportstone and wackestone and 

quartz-carbonate sandstone; all 

lithologies bioturbated, and contain 

notable phosphate and glauconite.

1 CO (13A)

5 TS (13A, AA, E: ph PG; 

D: ph W; F: ph quartzcarbonate sandstone)

TS: ph bioclasts, pore fillings, 

patches in A, AA; ph bioclasts, 

clasts (≤2 mm diam; contain 

spicules, silt) in D-F.

Northwest

 Soakpak Mt.

(04AD12)

Chandler Lake A-4

68°11.998’ (to 

11.881’)

151°51.953’ (to 

51.509’)

EMA (unnamed 

thrust sheet south 

of Skimo thrust 

sheet); upper Lisburne Group.

Subcrop and rubble of bioturbated, 

phosphatic skeletal supportstone 

(with glauconite, quartz, pyrite) 

and variously phosphatic and glauconitic quartz and (or) carbonate 

siltstone.

6 TS (12B, C, H: ph PG; 

12F, G, J: ph siltstone).

TS: ph peloids (≤3.5 mm diam), 

bioclasts in all; ph ≤7-10% in 

12H, J, minor in others; silt, 

spicules in ph clasts in 12J; ph 

nodule (1 cm diam) in 12B.

West Soakpak

 Mt. area

(84/85AKa16 

[MS, plate 

5 in Adams, 

1991])

Chandler Lake A-4

68°12.25’

151°51.35’

EMA (unnamed 

thrust sheet south 

of Skimo thrust 

sheet); uppermost 

Lisburne Group.

Crinoidal limestone with notable 

glauconite, phosphatic clasts and 

nodules, and pyrite; some bioclasts 

bored and (or) partly phosphatized; 

directly underlies Siksikpuk Fm. 

(contact is sharp and undulatory).

1 CO (16-1)

1 TS (16-1: PL)

TS: skeletal PW-M with ph nodule (>1cm diam; cut by borings?), few % ph peloids and 

bioclasts, and ≤5% glauconite; 

may be a hardground.

East side of 

 Soakpak Mt. 

(SOAK-TOP)

Chandler Lake A-3

~68°13’

151°40’

(location approximate)

EMA (unnamed 

thrust sheet south 

of Skimo thrust 

sheet); uppermost 

Lisburne Group.

Pelmatozoan-bryozoan grainstone 

with notable ph clasts + bioclasts.

1 CO

1 TS 

[both from same bed]

TS: few % ph bioclasts (some 

only partly replaced) and 

rounded ph peloids (200-400μ 

diam).

Gray Mt. 

(84AKa17 

[MS, plate 

2 in Adams, 

1991])

Wiseman D-3

67°56.300’

151°15.200’

EMA (south of 

Toyuk thrust 

fault); uppermost 

Lisburne Group.

Uppermost Lisburne Group is calcareous siltstone; basal Siksikpuk 

Formation is sandy siltstone with 

phosphatic pebbles (≤5 cm diam).

Lithologic description in 

Adams (1991).

Adams reports pyrite-rimmed 

ph? clasts (≤2 cm diam.) in uppermost Lisburne Group.

Siksikpuk

 River

(05PP59)

Chandler Lake B-4

68°18.664’

152°19.981’

EMA (Skimo thrust 

sheet); upper Lisburne Group.

Crinoid-bryozoan grainstone (59C) 

overlain by silty mudstone (59A) 

and siliceous spiculite (59Y, Z).

1 CO (59C)

4 TS (59A, C, Y, Z)

TS: minor ph patches (59C), ph 

bioclasts and clasts (59A), and 

2 ph nodules (≤ 2 mm; 59Y).

Loc. 11

Skimo Creek 

(SKA 178-

187 [Dumoulin, Whalen 

MS]; also see 

table 1)

Chandler Lake B-4

~68°17.840’

151°55.070’

EMA (Skimo thrust 

sheet); ~34 m 

below top of Lisburne Group.

SKA 178-186: brachiopod supportstone, overlain by calcareous shale 

and mudstone. SKA187: 45-cmthick interval (omission surface?) 

of bioturbated skeletal grainstone 

with notable ph clasts, glauconite, 

lesser quartz sand; some bioclasts 

bored.

2 CO (SKA 178, 187)

2 GX (Corg only: SKA 

180.5, 183.5; both BS)

5 TS with ph and (or) 

glauconite (SKA 180.5, 

181: BS; 186.75, 

187.05, 187.1C: ph G)

TS: ?ph nodule (1x2cm) in 

SKA 181 (BS); ph bioclasts in 

SKA 186.75, 187.05, 187.1C; 

rounded ph clasts in SKA 

187.1C.

Encampment 

 Creek

(05AD9 [MS, 

upper Lisburne Group 

only])

Chandler Lake B-4

68°22.592’

152°06.565’

EMA (Tiglukpuk 

thrust sheet); upper 

Lisburne Group.

Poorly exposed interval (1-2 m thick) 

of bioturbated, muddy, calcareous 

siltstone, with 5-10% glauconite 

and pyrite, and a few phosphatic 

clasts and nodules.

1 CO (9I)

3 TS (9I, J, K: all ph 

muddy siltstone)

TS: I, J, K have minor rounded 

to irregular ph clasts (≤300μ 

diam); ph bioclasts and nodules (to 800μ diam) in I.
 Tables 1–3 49

7

Age control, biofacies, CAI

8

Geochemical data

9

Remarks

P2O5 wt % Corg wt %

Conodonts: very abundant; 

Chesterian; moderate water 

depth or deeper; CAI 2.5 (1).

CHMC: abt ph bioclasts, including 

crinoid, ostracode, and bryozoan 

fragments (1).

65E likely correlates with SKA 187 (Skimo Creek section); 

65D, F, G may correlate with ~SKA 181.

Additional TS data: 65D has fitted fabric, ≤10% glauconite. 

65E has 10-20% quartz sand, ≤10% pyrite, silica cement; 

some ph peloids contain abt spicules. Bored bioclasts in 

65D, F.

Conodonts (8C): Chesterian, CAI 

1.5-2 (6).

Loc. 9, Dumoulin and others (2008).

8C may correlate with SKA 187 (Skimo Creek section). 

Bored bioclasts (8C, 22?); CHMC yielded glauconite-filled 

radiolarians(? ) and ph steinkerns.

Conodonts (from 13A): 

Chesterian (not earliest); CAI 

1.5-2; CHMC chiefly ph clasts 

and bioclasts(6).

Loc. 14, Dumoulin and others (2008).

13A, AA may correlate with ~SKA 178 (Skimo Creek section); 13D-F correlate with SKA 187.

Additional TS data: most abt, biggest ph grains in F (≤7%); 

some bored bioclasts (and ph clasts?) in E.

No age control here. Close to K. Adams measured section 84/85AKa16.

Glauconite ≤10-20% in 12H, J, ≤5% in others.

12B, C, could correlate with SKA 178 (Skimo Creek section); 

12H, J, very similar to SKA 187; 12F, G could correlate 

with SKA 219-221, or 05AD9 siltstone (Encampment 

Creek, see below).

Conodonts: latest Mississippian-earliest Pennsylvanian (no younger 

than lower D. noduliferus Zone); 

CAI 2.5-3 (6).

Loc. 15, Dumoulin and others (2008). K. Adams (unpub. field 

notes) describes “phosphatic clasts” (≤1 cm diam) near top 

of Lisburne Group here; her MS of upper Lisburne Group 

only. TS (from K. Adams, examined by J. Dumoulin) contains some bioclasts with phosphate-filled borings.

Conodonts: very late Chesterian; lag 

concentrate; CAI 2.5-3 (6).

Loc. 18, Dumoulin and others (2008); sample collected by 

geologists from Petro-Canada Oil and Gas Co.

CHMC: mostly ph brachiopod fragments, lesser phosphatized 

lithic and crinoid fragments.

No age control here; regional relations suggest upper Lisburne Group 

is late Late Mississippian.

Adams (1991); MS of upper Lisburne Group only.

Conodonts: abt (>500); Chesterian; 

relatively shallow water, high 

energy setting; CAI 1.5-2 (6).

Loc. 8, Dumoulin and others (2008).

59C likely correlates with SKA 178 (Skimo Creek section); 

59C TS contains some partly ph bioclasts.

Glauconite minor in 59C; 5-30% in Y and Z.

Conodonts (from both): Chesterian; 

CAI 1.5. Conodonts (from SKA 

187): not earliest Chesterian; 

drowned lag concentrate (6).

180.5: 1.79

183.5: 1.68

Loc. 1, Dumoulin and others (2008).

Conodonts in SKA 187 fairly abundant (>180); CHMC 

mainly pyritic, glauconitic, ph carbonate rock fragments, 

with minor ph bioclasts and fluorite crystals. CHMC from 

SKA 178 contains glauconite.

Conodonts (from 9I): early 

Chesterian; CAI 1.5-2 (6).

Loc. 13, Dumoulin and others (2008).

This interval may correlate with SKA 187 (Skimo Creek 

section).
50 Depositional Setting and Geochemistry of Phosphorites and Metalliferous Black Shales, Northern Alaska

Table 2. Less-phosphatic localities in the Lisburne Group, northern Alaska.—Continued

1

Locality no., 

name 

(field no.)

2

Quadrangle,

latitude N.,

longitude W.

3

Structural and 

stratigraphic

setting

4

Thickness and characteristics of 

phosphatic strata

5

Data base 

6

Evidence for and (or) 

details of phosphate

Erratic Creek

(PP 03 026, 27)

Chandler Lake B-2

68°21.552’

150°47.663’

EMA (thrust sheet 

uncertain); upper 

Lisburne Group.

Crinoidal supportstone with minor 

phosphatic bioclasts.

1 CO (27)

1 TS (26: ph PG)

[both from same bed]

TS: minor ph bioclasts and 

glauconite.

Atigun Gorge

 West

(90KW H [Dumoulin, Watts 

MS, upper 

Lisburne 

Group])

Philip Smith Mts. 

B-5 

(NW 1⁄4 sec. 25, 

T12S, R10E)

EMA (unnamed 

thrust sheet); upper 

Lisburne Group.

Uppermost 7.5 m of Lisburne Group 

is bryozoan wackestone (with 

lenses of supportstone) that contains rare to minor phosphate, most 

notably in the upper 1 m of section. Overlying Siksikpuk Fm. is 

heterogeneous, ranging from lime 

mudstone to pebbly sandstone.

3 CO

51 TS (43 from Lisburne 

Group; 8 from Siksikpuk Formation)

TS: minor ph bioclasts, rounded 

ph clasts, and ph skeletal pore 

fillings.

Atigun Gorge

 East

(90KW F 

[Dumoulin, 

Watts]; 

AKa21 [Adams]; both 

are MS, upper Lisburne 

Gp. )

Philip Smith Mts. 

B-4 

KW F:

68°29.25’

149°08.833’

AKa21:

68°27.583’

149°16.0’

EMA (unnamed 

thrust sheet); upper 

Lisburne Group.

Uppermost 15 m of Lisburne Group 

consists of several cycles of 

skeletal grainstone grading up into 

wackestone and (or) packstone; 

overlying Siksikpuk Fm. is quartz 

siltstone and sandstone. Minor 

phosphate and glauconite in 

uppermost Lisburne and lower 

Siksikpuk.

2 CO 

23 TS (Lisburne Group: 

7 from KW F, 11 from 

AKa21; Siksikpuk Formation: 5 from KW F)

TS: minor rounded ph and 

glauconite clasts in KW F, with 

possible ph hardground ≥10 m 

below top of Lisburne Group. 

Ph nodules (≤6 mm diam) and 

bioclasts in AKa TS.

 Phosphatic strata of early (but not earliest) 

Loc. 8

Akmalik Creek

 East

(05AD65,

~85AMu2 [see 

table 1])

Killik River B-2

68°22.055’

154°10.401’

EMA (Killik River 

sequence of Mull 

and others, 1994); 

uppermost Lisburne Group.

Highest exposed Lisburne Gp., 

<1-2 m below exposed base of 

Siksikpuk Fm., is 3.5 m of gray, 

skeletal supportstone (with black 

phosphatic grains) in 40-cm-thick 

beds.

1 CO (Mu2-9)

1 TS (65B)

TS: 10-25% ph clasts (including 

ooids with >15 layers); some 

clasts contain silt, radiolarians; 

notable bored bioclasts.

05ALS15 Chandler Lake B-4

68°16.058’

152°03.320’

EMA (sheet just 

south of Skimo 

thrust sheet); upper 

Lisburne Group.

Interbedded muddy siltstone to very 

fine grained sandstone and spiculitic mudstone.

1 TS (15B: bioturbated 

silty ph M with spicules 

and glauconite)

TS: Few % ph clasts and bioclasts, rounded to irregular, 

≤200μ diam.

Loc. 11

Skimo Creek 

(SKA 210-

221 [Dumoulin, Whalen 

MS])

Chandler Lake B-4

~68°17.864’

151°54.952’

EMA (Skimo thrust 

sheet); uppermost 

2 m of Lisburne 

Group.

Lime mudstone with 5- to 15-cmthick, more resistant, partly bioturbated intervals of dark shale that 

contain lenses (≤ a few cm thick) 

of glauconitic, phosphatic, silty to 

muddy spiculite.

2 CO (219, 221)

8 TS (SKA 210, 210.5, 

210.5A, 219A, 219AA 

221, 221A, 221B: all 

ph spiculite with quartz 

silt, ≤5% glauconite)

TS: 5-20% ph peloids (≤600 μ 

diam) > bioclasts in all 221 

TS; minor ph (mostly bioclasts 

≤200 μ diam) in all 210 and 

219 TS.

Bombardment 

 Creek 

(89AD44, 45 

[MS upper 

Lisburne 

Group])

Wiseman D-2

44:68°55.467’

150°42.667’

45: 68°54.917’

150°40.333’

Parautochthonous 

(e.g., Young, 2004) 

[Doonerak antiform]; uppermost 

Lisburne Group.

Upper 5 m of Lisburne Group is 

skeletal supportstone; basal 80 

cm of overlying Echooka Fm. is 

quartz-carbonate siltstone to very 

fine grained sandstone. Notable 

phosphate ~4.4 m below top of 

Lisburne and in basal Echooka.

5 CO (44C, Z; 45F; 

AKa4-1, 4-3)

31 TS (Lisburne Group: 

10 from 44, 10 from 45, 

2 from AKa4; Echooka 

Formation: 3 from 44, 1 

from 45).

TS: in 44K (4.4 m below top of 

Lisburne Gp.) ≤10% ph material, mostly filling bryozoan 

pores, lesser clasts (≤ 800μ 

diam; 1 ?composite grain).
 Tables 1–3 51

7

Age control, biofacies, CAI

8

Geochemical data

9

Remarks

P2O5 wt % Corg wt %

Conodonts: abt (>500); Chesterian 

(likely very late Chesterian); CAI 

2-3 (6).

Loc. 19, Dumoulin and others (2008).

Samples taken ~5 m below base of Siksikpuk Formation.

Conodonts (from ≤7.5 m below 

top of Lisburne Group): latest 

Chesterian; shallow-water biofacies (lowest sample, shallow to 

moderate water depths; others, 

high-energy settings); CAI 2-2.5 

(1, 7).

Loc. 3, Dumoulin and others 1997. 

TS from Siksikpuk Fm. contain locally abt clasts of phosphate 

and glauconite.

Conodonts (from 1 and 8 m below 

top of Lisburne Group): Chesterian, possibly late Chesterian; 

relatively shallow-water biofacies; 

CAI 2-2.5 (1, 7).

90KW F is loc. 2, Dumoulin and others (1997); AKa21 data 

from plate 7, Adams (1991) and K. Adams, unpub. field 

notes (thin sections provided by Adams and examined by J. 

Dumoulin). 

Several AKa TS contain ≤5% ph clasts and 30-70% glauconite clasts and resemble SKA 187 (Skimo Creek section). 

TS from Siksikpuk Fm. contain locally abt clasts of phosphate and glauconite.

Morrowan (Early Pennsylvanian) or younger age

Conodonts (from 0.5 below top of 

Lisburne Group): late Morrowan 

or younger, with redeposited 

Chesterian forms; CAI 3 (1).

65B taken <1 m below top of highest Lisburne Gp. exposure, 

and <1-2 m below basal Siksikpuk Fm. [grassy covered 

zone lies between]; 65B likely from same bed as 2-9. 

Strata here are slightly younger, and a different lithology, than 

SKA 221 (Skimo Creek section).

No age control here. Loc. 10, Dumoulin and others (2008).

Lithologies here most like SKA 219-221 (Skimo Ck. section) 

but could also correlate with SKA 187.

Conodonts: abundant (>300 in SKA 

219; >550 in SKA 221); early 

(but not earliest) Morrowan; CAI 

1.5-2 (6).

Loc. 1, Dumoulin and others (2008).

CHMC from SKA 221 contains phosphatic clasts and bioclasts. 

221B TS contains a 1-mm-wide burrow(?) filled with ph 

peloids (20-80 μ in diam).

Also see table 1.

Tightest ages from conodonts: from 

44C (highest Lisburne Gp.), early 

(not earliest) Morrowan; from 44Z 

(10 m lower), very latest Chesterian-very earliest Morrowan; CAI 

4.5-5 (1, 8).

Near MS 74-1 (Armstrong and Mamet, 1978) and 84AKa4 

(Adams, 1991; MS of upper Lisburne Gp. only). 

TS from Echooka Formation: ≤5% ph clasts (≤4 mm diam) 

and bioclasts in 44A, 10-30% ph clasts in 44D (filling burrow or boring on top of Lisburne Group).
52 Depositional Setting and Geochemistry of Phosphorites and Metalliferous Black Shales, Northern Alaska

Table 3. Compositions of black shales, phosphorites, and phosphorite nodules from the Lisburne Group, northern Alaska. 

[For statistical calculations the censured values (<x.xx) are assigned one-half the analytical detection limit (Sanford and others, 1993). REE anomalies 

are calculated by shale normalization (SN) using data for PAAS (Taylor and McLennan, 1985): Ce/Ce*(SN) = 2CeSN/(LaSN+PrSN); Eu/Eu*(SN) = 2EuSN/

(SmSN+GdSN). MF, calculated marine fraction (see text)]

Component Black Shales (n =17) Phosphorite (n=24) Phosphorite Nodules (n=3)

Mean S.D. Range Mean S.D. Range Mean S.D. Range

SiO2 (wt %) 41.50 ± 18.57 11.91-67.12 18.88 ± 16.91 1.99-46.89 18.69 ± 4.66 13.31-21.43

TiO2 0.256 ± 0.131 0.017-0.510 0.011 ± 0.006 <0.001-0.027 0.024 ± 0.010 0.018-0.036

Al2O3 4.88 ± 2.35 0.46-9.27 0.35 ± 0.18 0.11-0.88 1.24 ± 0.71 0.49-1.89

Fe2O3 1.65 ± 0.52 0.70-2.62 0.26 ± 0.24 0.07-1.25 0.52 ± 0.16 0.35-0.67

MnO 0.042 ± 0.054 0.005-0.190 0.013 ± 0.031 0.001-0.148 0.025 ± 0.009 0.017-0.035

MgO 1.81 ± 2.21 0.53-9.90 0.68 ± 1.13 0.03-4.70 1.23 ± 1.02 0.06-1.90

CaO 19.66 ± 14.55 4.22-47.21 40.76 ± 9.42 24.85-53.72 42.42 ± 2.05 40.92-44.76

Na2O 0.32 ± 0.21 0.09-0.84 0.17 ± 0.07 <0.01-0.32 0.17 ± 0.18 0.06-0.38

K2O 1.32 ± 0.74 0.13-2.72 0.09 ± 0.05 <0.01-0.22 0.09 ± 0.06 0.04-0.13

P2O5 4.20 ± 3.61 0.54-11.54 23.49 ± 4.56 17.63-36.98 27.6 ± 2.84 25.80-30.91

LOI 23.49 ± 8.52 8.12-36.06 11.65 ± 6.07 3.98-21.49 6.66 ± 0.34 6.26-6.87

F 0.76 ± 0.60 0.17-2.01 4.29 ± 1.51 1.95-7.63 5.07 ± 1.18 4.28-6.43

Total C 10.71 ± 3.97 3.20-17.10 4.72 ± 1.94 2.05-8.28 2.65 ± 0.47 2.11-3.00

Corg 7.53 ± 5.15 1.34-17.36 3.01 ± 1.30 1.21-6.73 1.69 ± 0.99 0.81-2.76

CO2 12.41 ± 11.93 0.53-33.40 8.47 ± 6.61 0.9-18.10 3.52 ± 2.26 0.92-4.90

S 0.89 ± 0.59 0.28-2.60 0.45 ± 0.16 0.25-0.90 0.49 ± 0.18 0.30-0.66

SO4 0.70 ± 0.63 0.05-2.10 1.01 ± 0.50 0.12-1.90 0.42 ± 0.03 0.40-0.45

Li (ppm) 17.5 ± 13.2 2.4-43.7 2.5 ± 1.8 1.1-10.5 1.4 ± 0.4 1.1-1.8

Be 2 ± 2 <1-6 1 ± 1 <1-3 <1 <1

B 45 ± 27 10-104 9 ± 4 5-23 8 ± 3 5-11

Sc 7.5 ± 3.9 2.5-19.3 2.1 ± 1.0 0.6-3.9 8.2 ± 1.6 6.8-9.9

Zr 75 ± 27 26-120 19 ± 7 8-39 26 ± 9 16-35

Hf 2.0 ± 0.9 0.7-3.5 0.4 ± 0.2 0.1-1.0 0.8 ± 0.3 0.5-1.0

Nb 3.6 ± 1.8 1.2-8.7 0.5 ± 0.4 <0.2-1.4 1.3 ± 0.7 0.7-2.0

Ta 0.26 ± 0.16 <0.01-0.57 <0.01 <0.01-0.43 0.05 ± 0.01 <0.01-0.06

Cr 759 ± 561 39-1,690 117 ± 54 35-297 31 ± 8 23-38

V 881 ± 767 55-2,831 371 ± 161 79-763 26 ± 7 21-34

Co 4.8 ± 3.1 1.4-12.8 0.8 ± 0.3 0.6-1.7 2.0 ± 1.5 0.8-3.7

Ni 283 ± 137 87-551 50 ± 21 20-110 20 ± 3 16-23

Cu 144 ± 72 28-312 39 ± 58 <10-300 57 ± 72 13-140

Zn 1,112 ± 1,081 <30-4,670 283 ± 149 90-710 115 ± 112 32-242

Cd 52.5 ± 48.6 1.01-142 21.5 ± 13.1 5.74-61.0 0.55 ± 0.19 0.42-0.77

Mo 56.5 ± 35.1 15.8-135 8.77 ± 5.08 2.25-21.0 4.62 ± 1.15 3.74-5.92

Re 0.299 ± 0.225 0.084-0.855 0.138 ± 0.088 0.033-0.326 0.034 ± 0.011 0.022-0.043

Au (ppb) 5.49 ± 14.7 <0.5-58.7 <0.5 <0.5 <0.5 <0.5

Ag 13.4 ± 12.3 <0.5-43.5 0.9 ± 0.5 <0.5-2.48 <0.5 <0.5

Tl 2.08 ± 3.26 <0.05-12.3 0.76 ± 1.28 <0.05-5.94 <0.05 <0.05-0.09

Pb 9.79 ± 4.37 3.79-19.6 4.82 ± 1.74 2.51-10.1 3.64 ± 0.86 2.89-4.58

Ga 3.85 ± 2.16 0.58-8.67 0.23 ± 0.19 <0.02-0.60 0.79 ± 0.55 0.32-1.39

Ge 2.3 ± 2.6 <0.5-10 <0.5 <0.5-2.3 <0.5 <0.5

Rb 40 ± 22 2.5-88 3 ± 2 <1-7 3 ± 2 <1-4

Sr 315 ± 267 67-1,010 688 ± 133 457-969 1,930 ± 147 1,800-2,090
 Tables 1–3 53

Component Black Shales (n =17) Phosphorite (n=24) Phosphorite Nodules (n =3)

Mean S.D. Range Mean S.D. Range Mean S.D. Range

Sn <1 <1-4 <1 <1-5 <1 <1

W 1.1 ± 0.8 <0.5-3.5 <0.5 <0.5-1.9 <0.5 <0.5

Th 3.86 ± 1.73 0.93-7.18 0.47 ± 0.65 0.11-3.36 1.36 ± 1.33 0.34-2.86

U 37.0 ± 25.5 9.47-118 93.3 ± 35.0 45.2-166 91.4 ± 32.3 60.2-125

As 29.0 ± 18.1 9.8-77.9 4.6 ± 7.9 <0.5-33.4 6.1 ± 4.0 2.1-10

Sb 8.8 ± 4.8 2.4-19.0 1.7 ± 1.9 0.5-9.9 1.0 ± 0.2 0.9-1.3

Te 0.33 ± 0.17 0.15-0.67 0.06 ± 0.03 <0.02-0.12 0.10 ± 0.03 0.08-0.14

Se 45.2 ± 24.2 22.7-111 12.2 ± 6.00 4.60-27.2 11.9 ± 4.47 8.30-16.9

Ba 899 ± 2,090 83.0-8,770 595 ± 1,159 37-4,060 3,707 ± 627 3,140-4,380

Y 139 ± 92.6 26.1-340 232 ± 202 72.7-1030 216 ± 110 94.4-308

La 70.2 ± 40.4 26.4-150 113 ± 103 35.9-517 82.5 ± 40.6 40.9-122

Ce 32.3 ± 14.7 12.3-68.4 21.5 ± 25.8 5.20-132 124 ± 73.4 55.4-201

Pr 11.6 ± 6.39 4.26-25.3 13.7 ± 16.7 3.56-82.8 19.3 ± 10.3 8.05-28.3

Nd 47.1 ± 27.1 16.1-117 49.7 ± 60.1 11.6-298 86.9 ± 47.5 34.5-127

Sm 9.06 ± 4.92 2.87-21.0 9.18 ± 11.7 2.17-58.5 22.4 ± 12.8 8.58-33.8

Eu 2.215 ± 1.231 0.619-4.978 2.288 ± 2.856 0.560-14.30 6.157 ± 3.432 2.319-8.932

Gd 10.5 ± 6.19 2.50-26.1 12.7 ± 15.0 3.46-75.6 24.7 ± 13.4 9.41-34.7

Tb 1.79 ± 0.99 0.47-3.89 2.00 ± 2.25 0.51-11.3 4.45 ± 2.39 1.78-6.40

Dy 11.2 ± 6.38 3.26-24.4 12.9 ± 13.6 3.28-68.6 26.1 ± 13.5 10.7-36.0

Ho 2.45 ± 1.44 0.74-5.67 3.15 ± 2.98 0.86-15.0 5.41 ± 2.60 2.41-7.08

Er 7.58 ± 4.21 2.87-16.2 10.2 ± 9.01 3.08-45.3 16.7 ± 7.31 8.32-21.7

Tm 1.101 ± 0.586 0.471-2.330 1.481 ± 1.207 0.461-6.040 2.480 ± 0.997 1.329-3.080

Yb 6.73 ± 3.52 2.83-14.5 9.06 ± 6.88 2.83-34.2 14.5 ± 5.23 8.49-17.6

Lu 1.056 ± 0.554 0.432-2.350 1.390 ± 0.962 0.438-4.740 2.248 ± 0.785 1.358-2.842

Ce/Ce*(SN) 0.305 ± 0.174 0.156-0.780 0.113 ± 0.027 0.084-0.188 0.701 ± 0.089 0.612-0.790

Eu/Eu*(SN) 1.102 ± 0.045 1.036-1.182 1.070 ± 0.037 0.970-1.116 1.232 ± 0.045 1.198-1.282

Table 3. Compositions of black shales, phosphorites, and phosphorite nodules from the Lisburne Group, northern Alaska.—Continued 
This page left intentionally blank
Appendix. Additonal Geochemical Data

55
This section presents additional geochemical data on phosphorites and metalliferous black 

shales in the Carboniferous-Permian Lisburne Group. Table A1 contains complete geochemical 

analyses for all samples used in our study. Tables A2 and A3 contain results of statistical factor 

analyses of black shales and phosphorites, respectively.

Samples for geochemical analysis were trimmed of weathered surfaces and veins and then 

pulverized in an alumina-ceramic mortar. All analyses were done at Activation Laboratories in 

Ancaster, Ontario. Major, selected trace, and rare earth elements (REE) were determined by 

inductively coupled plasma-mass spectrometry (ICP-MS) on rock powders fused with lithium 

metaborate/tetraborate in order to insure complete acid dissolution of minerals such as zircon, monazite, xenotime, and barite prior to analysis. Instrumental neutron activation analysis 

(INAA) was used for As, Sb, Sc, and Cr. Data for Li, B, Ga, Co, Cd, Au, Pb, Mo, Re, Te, and 

Se were acquired by a multi-acid digestion of powders followed by ultratrace ICP-MS analysis, 

which has higher precisions and lower detection limits than the fusion ICP-MS method. Analyses were obtained on duplicate samples and 8-12 standards. One sample, phosphatic limestone 

03AD27B, was not analyzed using the ultratrace ICP-MS method; data reported for Ga, Co, 

Au, Pb, and Mo were determined by fusion ICP-MS; data for Cd and Se were determined by 

INAA; Li, B, Re, and Te were not analyzed. Results for the following elements (by fusion ICPMS) generally were below limits of detection as listed in parentheses: Cs (<0.1 ppm), In (<0.1 

ppm), Ta (<0.1 ppm), W (<0.5 ppm), and Sn (<1 ppm), and thus are not reported. Details of the 

various analytical methods are available at www.actlabs.com. 

Table A2 lists results of a statistical factor analysis of the bulk compositions of 17 samples of black shale from the Lisburne Group. The limited number of samples in this database 

restricts the number of elements; hence, those considered the most informative and representative were selected. Elements not included in the factor analysis, among 65 determined, have 

uniformly very low concentrations, were not detected, or were not analyzed by the ICP-MS or 

INAA methods used. Examples are the alkali and alkali earth elements Li and Be; transition 

metals such as Nb, Tc, Ru, Rh, Pd, Hf, Ta, W, Os, Ir, Pt, Au, and Hg; most middle and heavy 

REE; halogens including Cl, Br, I, and At; all noble gases; and all actinide elements except Th 

and U. Using four factors, significant loadings of ≥0.5 show that predominant factor 1 (31.0 

percent) comprises, in decreasing order of loading, V, Ni, Cd, Mo, Cu, Zn, Corg, Cr, and Se, 

which is a factor composed mainly of seawater-and biogenically- derived constituents (for 

example, Piper, 1994). Factor 2 (25.6 percent) consists of Ge, Re, Ag, Tl, and Se, and may be 

partly hydrothermal in origin. Factor 3 (17.4 percent) includes Al, Ti, and Corg, and clearly is 

detrital. Factor 4, the least dominant (12.2 percent), comprises P, La, and U, and is a phosphaterelated factor. Occurrence of V, Cr, Ni, Cu, Zn, Cd, Mo, and Se together with Corg in Factor 1 

supports inferred associations for these elements and Corg (fig. 9).

A statistical factor analysis of the bulk compositions of 24 phosphorite samples is listed in 

table A3. Using four factors, significant loadings of ≥0.5 show that predominant factor 1 (23.5 

percent) comprises, in decreasing order of loading, P, Sr, Ca, and F, and clearly is phosphatebased. Factor 2 (16.0 percent) consists of La, Y, Ce, Gd, and Cr, reflecting a factor composed 

mainly of LREE and Y. Factor 3 (15.5 percent) includes Mg, Ti, Ba, Al, K, Fe, and V, and 

largely is detrital in origin, perhaps excluding some Mg and Ba. Factor 4, the least dominant 

(14.9 percent), comprises Ni, Zn, Cu, U, and Corg, suggesting mostly seawater- and biogenically-derived constituents (for example, Piper, 1994). The presence of F and Sr in phosphatebased Factor 1 supports associations of F and Sr with P (fig. 13), but not for Y, LREE, and U 

that occur in different factors than P. The latter relationships are consistent with the general 

scatter of these elements relative to P2O5 in the phosphorites (fig. 13C), implying that they 

reside only partly in phosphate.

56
 Appendix. Additonal Geochemical Data 57

Table A1. Complete geochemical data from black shales and phosphorites from the Lisburne Group, northern Alaska. 

[REE anomalies are calculated by shale normalization (SN) using data for PAAS (McLennan, 1989): Ce/Ce*(SN) = 2CeSN/(LaSN+PrSN); Eu/Eu*(SN) = 2EuSN/

(SmSN+GdSN). n.a., not analyzed; phos., phosphatic; ls, limestone]

Sample no. SKBo-25 92AD31A 92AD31H 92AD32B 03AD27A 03AD38C 05AD6E CCP-0.4 CCP-1.35

Rock type Black shale Black shale Black shale Black shale Black shale Black shale Black shale Black shale Black shale

Latitude 68o17.773’ 68o37.967’ 68o37.967’ 68o30.660’ 68o23.662’ 68o27.627’ 68o22.900’ 68o17.500’ 68o17.500’

Longitude 151o54.609’ 156o43.750’ 156o43.750’ 157o30.920’ 162o27.326’ 161o58.391’ 152o51.490’ 152o01.061’ 152o01.061’

Major elements (weight percent)

SiO2 19.54 41.63 39.35 65.97 67.12 61.61 49.25 54.84 65.55

TiO2 0.166 0.439 0.387 0.258 0.513 0.206 0.279 0.240 0.202

Al2O3 3.12 8.39 7.44 5.20 9.27 4.68 4.99 4.23 3.76

Fe2O3

T 1.36 2.62 2.37 1.65 2.07 1.46 2.09 1.62 1.43

MnO 0.008 0.099 0.033 0.069 0.010 0.101 0.006 0.009 0.005

MgO 1.00 2.39 1.21 3.24 1.37 2.43 0.53 1.31 0.57

CaO 37.50 8.17 12.63 7.61 4.83 6.66 10.77 15.27 8.69

Na2O 0.01 0.39 0.40 0.09 0.42 0.43 0.21 0.26 0.30

K2O 0.80 2.09 1.77 1.14 2.46 2.06 1.74 1.14 1.05

P2O5 0.54 3.31 7.69 1.33 3.04 0.92 7.91 2.34 3.76

LOI 34.66 29.02 25.33 12.24 8.12 18.22 22.44 19.06 14.49

Total 98.70 98.55 98.61 98.80 99.22 98.78 100.22 100.32 99.81

F 0.17 0.66 1.27 0.56 0.78 0.19 1.27 0.40 0.58

Corg 5.32 15.9 14.7 2.69 3.00 7.68 15.0 6.38 8.05

CO2 27.9 4.45 2.06 8.10 0.73 6.80 0.53 10.1 3.04

S 1.14 1.53 1.16 0.28 1.04 0.60 1.57 0.73 0.82

SO4 0.23 0.21 0.09 0.03 0.05 0.06 0.50 1.20 0.90

Trace elements (ppm)

Li 6.4 28.3 25.4 7.6 34.4 35.1 14.2 9.9 11.7

Be <2 2 2 <1 2 1 6 2 2

B 31 65 66 73 67 53 31 23 23

Sc 4.6 11.0 8.0 7.0 12.4 6.6 7.7 6.5 6.1

V 1,870 1,720 1,180 169 249 160 2,831 346 576

Zr 52 116 79 86 120 69 89 68 67

Hf 1.1 3.1 3.0 2.1 3.5 1.7 1.6 1.8 1.7

Nb 2.3 5.8 4.9 3.8 8.7 3.9 3.4 3.1 2.6

Cr 241 1,690 1,340 573 205 39 1,660 1,060 1,070

Ni 423 461 379 135 87 285 551 263 268

Co 2.9 6.5 3.3 5.2 5.6 8.2 1.8 3.3 2.1

Cu 127 200 230 100 84 140 312 139 131

Pb 8.99 13.9 15.2 5.65 8.61 6.86 15.9 9.07 8.92

Zn 4,670 882 1,300 436 176 639 1,740 895 1,050

Cd 142 126 52.6 10.3 1.01 3.3 136 44.1 43.9

Mo 110 74.6 92.6 26.0 18.8 23.5 135 18.5 46.8

Re 0.239 0.187 0.166 0.112 0.084 0.114 0.495 0.321 0.367

Au (ppb) 0.3 58.7 21.4 <0.5 <0.5 <0.5 9.1 <0.5 <0.5

Ag 8.7 32.1 25.8 0.3 2.1 6.0 43.5 18.2 17.9

Tl 12.3 0.54 0.05 0.0 0.61 0.06 1.80 0.64 0.65

Ga 2.48 4.06 4.92 4.54 6.76 3.64 3.80 3.20 3.26

Ge 1.00 0.50 0.50 0.50 0.50 0.80 10.0 2.20 4.10

Rb 21 70 56 40 88 36 44 35 31

Sr 301 129 293 68 328 136 226 186 146

Th 2.09 6.82 7.18 4.61 5.42 3.88 4.22 3.87 3.40

U 53.5 31.4 49.9 13.0 22.3 14.7 59.4 16.7 25.7

As 61.9 45.0 44.0 27.0 13.3 9.84 23.9 21.3 22.0

Sb 11.0 19.0 18.0 7.2 2.4 5.9 15.4 5.9 6.6

Te 0.18 0.61 0.67 0.25 0.34 0.18 0.53 0.28 0.24
58 Depositional Setting and Geochemistry of Phosphorites and Metalliferous Black Shales, Northern Alaska

Table A1. Complete geochemical data from black shales and phosphorites from the Lisburne Group, northern Alaska.—Continued 

Sample no. SKBo-25 92AD31A 92AD31H 92AD32B 03AD27A 03AD38C 05AD6E CCP-0.4 CCP-1.35

Rock type Black shale Black shale Black shale Black shale Black shale Black shale Black shale Black shale Black shale

Latitude 68o17.773’ 68o37.967’ 68o37.967’ 68o30.660’ 68o23.662’ 68o27.627’ 68o22.900’ 68o17.500’ 68o17.500’

Longitude 151o54.609’ 156o43.750’ 156o43.750’ 157o30.920’ 162o27.326’ 161o58.391’ 152o51.490’ 152o01.061’ 152o01.061’

Se 48.9 65.0 55.8 51.3 29.2 33.9 111 25.7 38.0

Ba 91 850 980 326 2,050 150 291 122 106

Y 90.8 160 340 87 26.1 52.2 232 157 250

La 65.8 76.2 150 46.2 26.4 27.6 117 73.0 121

Ce 22.8 45.0 57.4 29.0 37.0 23.7 39.4 30.6 33.2

Pr 9.49 11.7 25.3 8.21 4.42 5.09 18.9 12.6 19.3

Nd 39.8 54.1 117 35.9 16.1 21.5 73.1 46.2 72.9

Sm 7.48 9.73 20.9 6.64 2.87 4.66 13.9 9.38 13.8

Eu 1.677 2.183 4.978 1.531 0.619 1.067 3.570 2.400 3.540

Gd 8.65 11.3 26.1 7.47 2.50 4.69 16.7 10.5 15.3

Tb 1.39 1.82 3.89 1.24 0.47 0.83 2.88 1.90 2.82

Dy 8.45 11.6 24.4 7.29 3.26 4.91 18.5 12.1 18.1

Ho 1.85 2.53 5.67 1.62 0.74 1.07 4.00 2.56 3.87

Er 5.97 8.47 16.2 5.08 2.87 3.52 12.3 7.63 11.6

Tm 0.891 1.263 2.163 0.719 0.528 0.544 1.820 1.130 1.600

Yb 5.45 7.48 12.0 4.11 3.62 3.35 11.6 6.98 9.49

Lu 0.844 1.154 1.785 0.638 0.599 0.542 1.890 1.090 1.440

Ce/Ce*SN 0.205 0.341 0.212 0.341 0.780 0.459 0.190 0.230 0.156

Eu/Eu*SN 1.037 1.036 1.101 1.066 1.047 1.081 1.138 1.144 1.143

Table A1. Complete geochemical data from black shales and phosphorites from the Lisburne Group, northern Alaska.—Continued

Sample no. CCP-3.4 CCP-5.8 CCP-5.8A CCP-7.5 JS-00-02 JS-04-23A JS-05-82C JS-05-93 03AD27B

Rock type Black shale Black shale Black shale Black shale Black shale Black shale Black shale Black shale Phos. ls.

Latitude 68o17.500’ 68o17.500’ 68o17.500’ 68o17.500’ 68o17.370’ 68o23.662’ 68o28.906’ 68o31.263’ 68o23.662’

Longitude 152o01.061’ 152o01.061’ 152o01.061’ 152o01.061’ 163o22.040’ 162o27.326’ 155o42.703’ 157o30.214’ 162o27.326’

Major elements (weight percent)

SiO2 34.63 22.21 26.07 12.44 49.42 11.91 49.59 34.36 8.94

TiO2 0.222 0.207 0.163 0.098 0.457 0.017 0.316 0.189 0.028

Al2O3 4.51 4.01 3.13 2.01 8.12 0.46 5.98 3.65 0.58

Fe2O3

T 1.57 1.39 1.21 0.91 2.12 0.70 2.12 1.32 0.98

MnO 0.006 0.008 0.008 0.005 0.038 0.190 0.010 0.109 0.212

MgO 0.65 0.95 0.91 0.91 1.28 0.93 1.21 9.90 1.38

CaO 24.34 35.54 34.89 44.13 14.37 47.21 4.22 17.36 48.48

Na2O 0.35 0.15 0.13 0.09 0.18 0.18 0.65 0.84 <0.02

K2O 1.26 0.83 0.73 0.24 2.72 0.13 1.57 0.72 0.02

P2O5 11.54 1.96 1.79 1.76 9.51 10.12 2.42 1.42 9.14

LOI 21.29 33.05 31.08 36.06 11.43 26.85 27.22 28.83 28.96

Total 100.37 100.31 100.11 98.65 99.65 98.70 95.31 98.70 98.74

F 2.01 0.36 0.35 0.31 1.53 1.88 0.43 0.21 1.86

Corg 9.43 5.14 4.19 2.92 4.41 1.34 17.4 4.47 0.91

CO2 7.18 26.5 26.3 33.4 1.65 25.6 1.14 25.5 27.50

S 0.91 0.50 0.50 0.52 0.38 0.55 2.60 0.32 0.62

SO4 2.10 1.00 1.40 1.60 0.09 0.31 0.90 0.60 0.34

Trace elements (ppm)

Li 34.5 10.8 8.4 3.4 43.7 4.4 17.6 2.4 n.a.

Be 3 3 3 2 1 <1 6 1 <2

B 82 37 30 17 104 10 33 13 n.a.

Sc 7.2 6.6 5.9 2.5 19.3 3.6 7.1 4.7 4.3
 Appendix. Additonal Geochemical Data 59

Table A1. Complete geochemical data from black shales and phosphorites from the Lisburne Group, northern Alaska.—Continued

Sample no. CCP-3.4 CCP-5.8 CCP-5.8A CCP-7.5 JS-00-02 JS-04-23A JS-05-82C JS-05-93 03AD27B

Rock type Black shale Black shale Black shale Black shale Black shale Black shale Black shale Black shale Phos. ls.

Latitude 68o17.500’ 68o17.500’ 68o17.500’ 68o17.500’ 68o17.370’ 68o23.662’ 68o28.906’ 68o31.263’ 68o23.662’

Longitude 152o01.061’ 152o01.061’ 152o01.061’ 152o01.061’ 163o22.040’ 162o27.326’ 155o42.703’ 157o30.214’ 162o27.326’

V 906 1,134 905 947 190 55 1,499 233 52

Zr 76 74 61 34 113 26 92 51 15

Hf 2.0 1.6 1.3 0.7 3.5 0.7 2.4 1.5 0.6

Nb 2.9 2.8 2.2 1.5 4.5 1.2 4.1 2.8 0.9

Cr 1,290 951 765 170 210 77 1,150 410 79

Ni 260 410 298 176 150 105 394 159 97

Co 4.5 3.3 2.5 1.4 12.8 7.3 2.4 8.7 5

Cu 234 176 136 72 104 28 179 54 29

Pb 19.6 7.33 5.87 5.06 11.1 7.55 13.0 3.79 13

Zn 981 1,520 1,110 2,130 15 188 835 338 117

Cd 86.0 40.5 33.2 81.9 1.89 2.63 80.3 6.55 2.3

Mo 80.3 54.0 49.4 50.4 15.8 56.0 84.1 24.7 53

Re 0.855 0.260 0.274 0.091 0.200 0.527 0.695 0.093 n.a.

Au (ppb) <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 3

Ag 20.2 11.8 10.5 1.6 0.3 1.5 19.5 8.3 2.0

Tl 0.73 3.88 3.47 7.33 0.03 0.69 1.99 0.44 1.43

Ga 8.67 3.30 2.39 1.63 7.66 0.58 3.12 1.52 <1

Ge 5.2 5.0 3.6 2.3 0.3 0.3 1.0 0.9 <0.5

Rb 36 29 26 12 65 2.5 56 25 2

Sr 432 282 311 482 875 1,010 77 67 1,100

Th 3.58 2.81 2.21 1.42 4.91 0.93 5.13 3.20 1.16

U 45.2 36.7 28.4 41.2 35.9 118 27.2 9.47 66.0

As 20.5 22.1 19.2 21.3 22.7 77.9 26.1 14.5 30.0

Sb 7.7 8.0 6.0 8.9 4.3 6.1 11.8 4.7 6.5

Te 0.55 0.28 0.21 0.16 0.42 0.15 0.40 0.19 n.a.

Se 52.9 24.3 42.3 22.7 25.2 23.8 85.8 32.8 8

Ba 150 122 97.0 83.0 8,770 237 715 147 210

Y 314 101 89.6 59.1 112 130 97.2 58.9 208

La 147 47.1 41.7 33.7 56.5 80.5 51.4 32.3 140

Ce 40.6 20.2 16.8 12.3 68.4 23.0 28.7 20.1 41.2

Pr 22.4 8.59 7.31 4.26 10.7 13.2 9.31 5.65 23.9

Nd 83.9 35.8 29.8 16.2 46.8 57.3 33.4 20.6 103

Sm 15.8 7.23 5.87 2.97 10.4 11.5 6.70 4.12 20.9

Eu 4.110 1.920 1.540 0.779 2.480 2.670 1.600 0.992 4.65

Gd 19.1 8.46 6.91 3.61 12.7 13.1 7.21 4.50 22.9

Tb 3.43 1.48 1.25 0.65 2.20 2.08 1.22 0.80 3.53

Dy 22.5 9.32 7.96 4.43 14.1 11.8 7.28 5.03 19.9

Ho 4.96 1.95 1.65 1.00 3.10 2.46 1.58 1.07 4.15

Er 15.5 5.85 5.14 3.16 9.62 7.86 4.83 3.24 12.9

Tm 2.330 0.842 0.751 0.479 1.390 1.110 0.682 0.471 1.71

Yb 14.5 5.25 4.73 3.09 9.36 6.37 4.19 2.83 9.35

Lu 2.350 0.864 0.778 0.529 1.460 0.943 0.612 0.432 1.38

Ce/Ce*SN 0.160 0.230 0.220 0.226 0.639 0.161 0.300 0.340 0.154

Eu/Eu*SN 1.129 1.182 1.148 1.135 1.047 1.086 1.115 1.095 0.653
60 Depositional Setting and Geochemistry of Phosphorites and Metalliferous Black Shales, Northern Alaska

Table A1. Complete geochemical data from black shales and phosphorites from the Lisburne Group, northern Alaska.—Continued

Sample no. 65ATR-75 CMD-4518 CMD-4617 CMD-5803 03AD2B 03AD10B 04AD8D 04AD9G 04AD9H

Rock type Phosphorite Phosphorite Phosphorite Phosphorite Phosphorite Phosphorite Phosphorite Phosphorite Phosphorite

Latitude 68o38.070’ 68o22.900’ 68o18.180’ 68o38.070’ 68o17.735’ 68o17.860’ 68o18.180’ 68o17.500’ 68o17.500’

Longitude 156o44.526’ 152o51.490’ 151o50.400’ 156o44.526’ 151o54.869’ 151o42.660’ 151o50.400’ 152o01.061’ 152o01.061’

Major elements (weight percent)

SiO2 5.42 44.24 5.42 14.68 28.32 5.25 36.99 41.30 2.44

TiO2 0.027 0.012 0.009 0.022 0.006 0.004 0.008 0.0005 0.0005

Al2O3 0.51 0.28 0.37 0.51 0.33 0.36 0.31 0.11 0.18

Fe2O3

T 0.31 0.07 0.12 1.25 0.17 0.09 0.24 0.52 0.09

MnO 0.042 0.002 0.003 0.148 0.002 0.002 0.002 0.004 0.005

MgO 3.39 0.07 0.34 4.70 0.07 0.12 0.06 0.05 0.70

CaO 45.34 29.41 49.91 38.77 32.99 45.99 28.47 30.89 51.39

Na2O 0.26 0.21 0.13 0.17 0.17 0.19 0.14 0.18 0.14

K2O 0.14 0.08 0.12 0.15 0.06 0.06 0.09 0.07 0.12

P2O5 26.02 19.35 22.04 20.73 23.84 28.62 21.04 21.54 21.83

LOI 14.6 5.03 14.6 13.1 8.56 12.3 8.00 3.98 21.49

Total 96.10 98.75 93.06 94.26 94.52 92.96 95.35 98.64 98.39

F 5.09 4.17 1.95 3.01 5.84 6.67 4.89 2.93 3.01

Corg 3.84 1.48 3.16 1.99 3.78 1.21 3.57 2.97 6.73

CO2 9.45 5.15 14.9 12.7 2.58 12.0 1.10 1.21 18.1

S 0.49 0.45 0.68 0.90 0.56 0.28 0.54 0.32 0.46

SO4 0.12 0.84 1.62 1.62 0.50 0.90 0.80 0.60 1.30

Trace elements (ppm)

Li 2.3 10.5 2.3 1.7 2.7 2.2 4.7 2.1 1.7

Be <1 <1 <1 <1 2 2 2 1 1

B 13 23 9 10 11 11 13 11 5

Sc 3.2 3.2 3.2 3.9 1.4 2.2 1.0 0.6 1.2

V 419 329 404 442 466 185 318 215 325

Zr 29 9 17 39 22 19 20 9 16

Hf 0.8 0.3 0.4 0.6 0.4 0.2 0.4 0.1 0.3

Nb 0.1 1.0 1.1 1.1 0.5 1.4 0.4 0.1 0.1

Cr 133 160 89 100 84 58 88 188 79

Ni 62 24 51 58 45 20 41 40 60

Co 1.1 0.6 0.8 1.3 0.7 0.8 0.6 0.7 0.6

Cu 48 5 28 67 18 18 16 30 40

Pb 4.61 4.03 6.32 5.71 5.72 2.97 3.63 4.08 3.38

Zn 172 137 298 540 312 224 264 170 390

Cd 14.3 17.2 22.9 33.9 23.9 15.0 13.2 6.63 11.9

Mo 6.31 4.37 10.3 14.4 8.85 5.15 7.56 13.3 3.17

Re 0.036 0.259 0.236 0.033 0.172 0.048 0.124 0.046 0.083

Au (ppb) <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5

Ag 2.5 1.6 1.0 1.6 0.3 0.9 0.6 0.9 0.9

Tl 0.23 0.03 0.03 0.11 0.20 5.94 0.27 0.21 0.27

Ga 0.23 0.39 0.32 0.43 0.32 0.01 0.04 0.06 0.01

Ge 0.3 0.9 0.3 0.3 0.3 0.3 0.3 0.3 0.3

Rb 4 3 3 4 2 2 2 0.5 1

Sr 467 499 770 666 675 903 627 703 642

Th 0.90 0.25 0.31 0.41 0.28 0.18 0.24 0.18 0.16

U 65.3 79.6 162 68.0 120 66.1 64.9 60.2 83.9

As 6.6 1.0 4.2 24.8 0.3 1.9 2.3 1.0 0.3

Sb 2.0 1.7 1.5 9.9 0.9 0.7 1.4 0.7 0.8

Te 0.06 0.03 0.07 0.07 0.10 0.06 0.03 <0.02 0.06

Se 19.3 8.0 13.2 17.3 8.6 5.7 9.6 5.8 7.6

Ba 316 101 259 4,060 79 272 61 62 39
 Appendix. Additonal Geochemical Data 61

Table A1. Complete geochemical data from black shales and phosphorites from the Lisburne Group, northern Alaska.—Continued

Sample no. 65ATR-75 CMD-4518 CMD-4617 CMD-5803 03AD2B 03AD10B 04AD8D 04AD9G 04AD9H

Rock type Phosphorite Phosphorite Phosphorite Phosphorite Phosphorite Phosphorite Phosphorite Phosphorite Phosphorite

Latitude 68o38.070’ 68o22.900’ 68o18.180’ 68o38.070’ 68o17.735’ 68o17.860’ 68o18.180’ 68o17.500’ 68o17.500’

Longitude 156o44.526’ 152o51.490’ 151o50.400’ 156o44.526’ 151o54.869’ 151o42.660’ 151o50.400’ 152o01.061’ 152o01.061’

Y 270 237 284 251 160 93 96 72.7 112

La 127 109 135 108 72.3 42.8 45.7 35.9 49.4

Ce 22.9 15.6 28.7 25.5 11.5 5.20 7.26 5.20 7.33

Pr 14.0 12.2 14.2 11.7 7.81 3.91 4.97 3.56 4.57

Nd 58.2 50.3 56.4 46.6 28.6 13.9 17.3 11.6 15.4

Sm 9.02 7.97 8.89 7.54 5.14 2.54 3.22 2.17 3.04

Eu 2.288 1.972 2.257 2.007 1.310 0.688 0.803 0.560 0.786

Gd 14.5 12.7 14.4 12.3 6.86 3.46 4.08 3.62 5.22

Tb 2.15 1.69 2.07 1.83 1.18 0.62 0.71 0.51 0.75

Dy 14.8 11.6 14.7 13.1 8.07 4.52 4.73 3.28 4.92

Ho 4.21 2.86 3.73 3.38 2.03 1.15 1.13 0.86 1.35

Er 13.1 9.19 12.5 11.3 6.91 3.85 3.89 3.08 4.48

Tm 1.811 1.384 1.960 1.854 1.040 0.610 0.589 0.461 0.662

Yb 12.5 7.85 11.4 11.1 6.92 4.01 3.77 2.83 4.17

Lu 2.007 1.248 1.851 1.829 1.130 0.652 0.604 0.438 0.666

Ce/Ce*SN 0.118 0.093 0.140 0.154 0.104 0.084 0.104 0.097 0.102

Eu/Eu*SN 1.056 1.085 1.069 1.100 1.080 1.116 1.075 1.082 1.060

Table A1. Complete geochemical data from black shales and phosphorites from the Lisburne Group, northern Alaska.—Continued

Sample no. 04AD9J 04AD9K 04AD9L 05AD2C 05AD65K1 05AD65K2 05PP063 SKB-28.5C TNC-191.6F

Rock type Phosphorite Phosphorite Phosphorite Phosphorite Phosphorite Phosphorite Phosphorite Phosphorite Phosphorite

Latitude 68o17.500’ 68o17.500’ 68o17.500’ 68o22.595’ 68o22.055’ 68o22.055’ 68o19.015’ 68o17.735’ 68o21.870’

Longitude 152o01.061’ 152o01.061’ 152o01.061’ 151o57.078’ 154o10.401’ 154o10.401’ 152o20.216’ 151o54.869’ 151o52.440’

Major elements (weight percent)

SiO2 1.99 39.60 4.80 42.22 13.90 3.71 6.83 46.89 32.16

TiO2 0.009 0.0005 0.004 0.010 0.015 0.015 0.008 0.013 0.008

Al2O3 0.19 0.13 0.17 0.41 0.88 0.48 0.39 0.34 0.28

Fe2O3

T 0.09 0.42 0.10 0.18 0.17 0.21 0.19 0.30 0.27

MnO 0.003 0.004 0.002 0.001 0.049 0.003 0.007 0.002 0.002

MgO 0.24 0.04 0.24 0.05 1.25 0.14 0.32 0.06 0.13

CaO 53.72 32.75 51.57 27.60 41.34 46.42 46.27 24.85 32.25

Na2O 0.01 0.13 0.13 0.15 0.16 0.23 0.21 0.15 0.24

K2O 0.01 0.06 0.04 0.09 0.22 0.13 0.09 0.09 0.05

P2O5 21.68 22.13 21.51 21.35 19.27 36.98 20.57 17.63 20.62

LOI 20.8 5.35 20.07 4.36 17.7 4.71 20.0 5.48 8.66

Total 98.71 100.61 98.64 96.42 94.94 93.03 94.90 95.81 94.67

F 3.43 3.07 3.06 4.34 4.03 7.63 5.24 3.68 4.45

Corg 2.43 2.24 3.34 1.84 1.23 1.52 3.52 2.53 2.25

CO2 17.7 2.04 17.9 0.94 15.0 1.74 14.2 0.90 4.64

S 0.41 0.28 0.34 0.32 0.25 0.43 0.60 0.38 0.58

SO4 0.32 0.60 1.00 0.70 0.80 1.30 1.60 0.50 1.60

Trace elements (ppm)

Li 2.0 2.0 1.8 2.2 1.7 2.9 2.0 1.8 2.9

Be <1 1 <1 2 1 2 3 2 <1

B 7 14 5 6 5 11 6 9 8

Sc 0.8 1.1 1.0 1.7 2.8 2.8 3.0 1.6 2.4

V 258 309 188 435 320 415 763 582 79
62 Depositional Setting and Geochemistry of Phosphorites and Metalliferous Black Shales, Northern Alaska

Table A1. Complete geochemical data from black shales and phosphorites from the Lisburne Group, northern Alaska.—Continued

Sample no. 04AD9J 04AD9K 04AD9L 05AD2C 05AD65K1 05AD65K2 05PP063 SKB-28.5C TNC-191.6F

Rock type Phosphorite Phosphorite Phosphorite Phosphorite Phosphorite Phosphorite Phosphorite Phosphorite Phosphorite

Latitude 68o17.500’ 68o17.500’ 68o17.500’ 68o22.595’ 68o22.055’ 68o22.055’ 68o19.015’ 68o17.735’ 68o21.870’

Longitude 152o01.061’ 152o01.061’ 152o01.061’ 151o57.078’ 154o10.401’ 154o10.401’ 152o20.216’ 151o54.869’ 151o52.440’

Zr 8 20 21 12 10 21 15 28 12

Hf 0.3 0.3 0.4 0.3 0.3 0.7 0.3 0.4 1.0

Nb 0.5 0.1 0.1 0.3 0.7 0.6 0.4 0.4 0.3

Cr 35 141 52 132 106 297 105 142 151

Ni 28 50 60 33 22 60 47 43 69

Co 0.8 1.7 0.7 0.6 0.8 1.0 0.8 0.6 0.6

Cu 10 30 40 22 10 62 13 19 22

Pb 4.06 3.67 5.45 4.78 2.85 10.1 3.66 3.38 5.18

Zn 222 150 460 179 173 390 501 203 230

Cd 16.3 5.74 25.8 23.1 41.7 15.4 35.1 14.9 8.56

Mo 5.27 9.60 7.63 2.25 2.89 21.0 9.05 14.1 7.06

Re 0.096 0.080 0.104 0.075 0.137 0.274 0.085 0.103 0.174

Au (ppb) <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5

Ag 0.6 0.7 0.7 0.3 1.1 1.3 0.3 1.1 0.3

Tl 0.13 0.19 1.21 1.86 0.52 0.30 0.55 1.03 2.84

Ga 0.01 0.01 0.01 0.48 0.27 0.39 0.21 0.25 0.54

Ge 0.3 0.3 0.3 0.3 0.6 1.2 0.3 0.3 1.0

Rb 0.5 2 2 3 7 5 3 3 2

Sr 656 648 818 457 528 969 750 567 744

Th 0.21 0.11 0.14 0.34 0.37 0.85 0.39 0.28 3.36

U 92.0 88.6 140 86.3 57.5 129 78.2 45.2 81.5

As 33.4 4.0 3.0 1.6 2.1 3.2 0.3 3.4 0.3

Sb 0.9 0.5 1.6 0.7 1.4 3.1 1.5 1.3 1.3

Te 0.05 0.02 0.05 0.07 0.04 0.10 0.08 0.06 0.12

Se 10.1 7.1 12 12.4 7.3 24.5 10.5 9.4 23.5

Ba 37 72 64 592 295 679 318 71 230

Y 118 125 166 219 165 532 175 111 1030

La 63.3 63.7 75.6 116 63.2 275 85.4 50.1 517

Ce 12.5 7.81 10.6 16.6 14.8 46.1 17.1 6.90 132

Pr 6.55 5.97 7.19 12.5 7.66 37.9 8.70 5.69 82.8

Nd 27.5 20.3 24.8 42.1 26.7 139 29.9 19.6 298

Sm 4.58 3.88 4.94 7.41 5.18 25.4 5.35 3.71 58.5

Eu 1.101 0.966 1.210 1.910 1.310 6.260 1.430 0.971 14.30

Gd 6.41 6.03 8.75 9.65 6.27 31.9 7.37 5.01 75.6

Tb 1.03 0.92 1.31 1.64 1.22 5.31 1.29 0.87 11.3

Dy 6.62 6.16 8.65 11.2 8.46 33.4 8.69 5.76 68.6

Ho 1.62 1.58 2.29 2.68 2.07 7.85 2.14 1.46 15.0

Er 5.44 5.45 7.38 8.84 6.74 25.3 7.28 4.98 45.3

Tm 0.819 0.840 1.050 1.330 1.020 3.680 1.130 0.761 6.040

Yb 4.86 5.32 6.30 8.65 6.71 22.4 7.04 4.89 34.2

Lu 0.781 0.898 0.957 1.380 1.030 3.330 1.050 0.798 4.740

Ce/Ce*SN 0.130 0.084 0.095 0.094 0.147 0.101 0.133 0.089 0.145

Eu/Eu*SN 1.025 1.039 0.970 1.110 1.059 1.087 1.107 1.098 1.115
 Appendix. Additonal Geochemical Data 63

Table A1. Complete geochemical data from black shales and phosphorites from the Lisburne Group, northern Alaska.—Continued

Sample no. CCP-1.8 CCP-3.7 CCP-4.85 CCP-10.1 JS-05-82A JS-05-82B 00AD4A 03AD27C 03AD27L

Rock type Phosphorite Phosphorite Phosphorite Phosphorite Phosphorite Phosphorite Phos. nodule Phos. nodule Phos. nodule

Latitude 68o17.500’ 68o17.500’ 68o17.500’ 68o17.500’ 68o28.906’ 68o28.906’ 68o17.370’ 68o23.662’ 68o23.662’

Longitude 152o01.061’ 152o01.061’ 152o01.061’ 152o01.061’ 155o42.703’ 155o42.703’ 163o22.040’ 162o27.326’ 162o27.326’

Major elements (weight percent)

SiO2 6.82 43.23 5.68 3.11 7.62 10.38 13.31 21.43 21.32

TiO2 0.009 0.0005 0.004 0.0005 0.013 0.018 0.018 0.018 0.036

Al2O3 0.50 0.15 0.47 0.14 0.45 0.49 1.89 0.49 1.34

Fe2O3

T 0.22 0.48 0.23 0.10 0.18 0.23 0.67 0.35 0.54

MnO 0.005 0.004 0.007 0.002 0.005 0.005 0.017 0.035 0.024

MgO 1.35 0.03 1.12 0.21 1.11 0.64 0.06 1.90 1.74

CaO 48.46 29.42 50.28 52.97 44.31 42.89 44.76 41.58 40.92

Na2O 0.02 0.09 0.02 0.12 0.32 0.26 0.06 0.08 0.38

K2O 0.03 0.02 0.005 0.15 0.08 0.17 0.13 0.01 0.04

P2O5 24.86 20.71 25.67 22.90 31.28 31.56 30.91 25.80 26.22

LOI 15.42 4.78 15.12 19.26 8.48 7.67 6.84 6.87 6.26

Total 97.69 98.91 98.61 98.96 93.85 94.31 98.67 98.56 98.82

F 3.55 2.98 3.42 3.13 6.78 6.66 6.43 4.51 4.28

Corg 5.52 3.57 3.90 3.74 2.75 3.22 2.76 1.50 0.81

CO2 11.9 0.95 12.9 17.8 4.89 2.51 0.92 4.90 4.75

S 0.46 0.27 0.35 0.26 0.60 0.60 0.30 0.51 0.66

SO4 1.40 0.60 1.10 0.80 1.90 1.80 0.45 0.40 0.41

Trace elements (ppm)

Li 2.6 1.3 2.4 1.1 1.9 1.8 1.1 1.3 1.8

Be 1 1 2 <1 2 2 <1 <1 <2

B 5 7 5 5 11 9 11 5 7

Sc 2.8 0.6 2.4 1.4 2.6 2.4 9.9 8.0 6.8

V 537 327 383 106 505 597 23 21 34

Zr 27 22 19 19 15 17 35 16 28

Hf 0.7 0.5 0.3 0.3 0.3 0.5 1.0 0.5 0.9

Nb 0.5 1.3 0.2 0.1 0.4 0.4 2.0 0.7 1.1

Cr 137 139 114 53 95 137 32 38 23

Ni 110 50 80 30 39 73 16 23 21

Co 0.8 0.7 0.8 0.6 0.9 1.5 3.7 0.8 1.6

Cu 300 30 40 30 13 35 140 13 18

Pb 6.07 2.51 6.40 3.39 6.29 7.42 3.46 4.58 2.89

Zn 710 160 290 90 274 243 242 32 69

Cd 61.0 18.6 20.3 7.64 21.8 41.8 0.77 0.47 0.42

Mo 6.32 8.54 8.58 2.38 20.6 11.8 5.92 4.2 3.74

Re 0.227 0.122 0.307 0.080 0.078 0.326 0.043 0.037 0.022

Au (ppb) <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5

Ag 0.3 0.8 0.3 0.6 1.0 0.9 0.3 0.3 0.2

Tl 0.51 0.05 0.55 0.11 0.42 0.70 0.09 0.03 0.03

Ga 0.60 0.01 0.27 0.01 0.31 0.37 1.39 0.32 0.66

Ge 2.3 0.3 0.7 0.3 0.3 0.3 0.3 0.3 0.3

Rb 0.5 2 0.5 1 4 4 4 0.5 4

Sr 711 604 879 786 778 657 1,900 1,800 2,090

Th 0.56 0.25 0.35 0.13 0.46 0.50 0.88 0.34 2.86

U 141 50.8 166 82.7 99.4 130 89.2 125 60.2

As 0.3 3.0 0.3 2.0 3.0 7.3 2.1 6.3 10

Sb 1.0 0.8 0.9 0.5 1.5 3.0 0.9 0.9 1.3

Te 0.06 0.08 0.09 0.05 0.10 0.08 0.08 0.14 0.09

Se 16.1 7.5 27.2 4.6 12.1 13.1 16.9 8.3 10.5

Ba 44 52 60 61 3,850 2,598 4,380 3,140 3,600
64 Depositional Setting and Geochemistry of Phosphorites and Metalliferous Black Shales, Northern Alaska

Table A2. Varimax normalized factor loadings for bulk compositions of 17 black shales from the Lisburne Group, northern Alaska. 

[Significant loadings of ≥0.5 are shown in bold type]

Element Factor 1 Factor 2 Factor 3 Factor 4

Al 0.0621 -0.2565 0.8743 0.0096

Ti 0.0555 -0.2158 0.8676 0.0194

P -0.0115 -0.2344 0.0842 0.9205

Corg 0.6826 -0.0880 0.5473 0.2265

V 0.9408 -0.0839 0.0734 0.0469

Cr 0.6475 -0.0381 0.4869 0.3320

Ni 0.9011 -0.1421 0.1928 0.0017

Cu 0.7533 0.0695 0.4072 0.3245

Zn 0.6961 -0.2778 -0.4369 -0.2710

Cd 0.8488 0.3136 -0.1521 0.0060

Mo 0.7979 0.3657 -0.2267 0.2877

Re -0.1340 0.9377 -0.2324 -0.0290

Ag 0.2603 0.9229 -0.0294 0.1348

Tl -0.0734 0.9100 -0.3131 -0.0924

Ge -0.0796 0.9417 -0.2382 -0.0062

U 0.0377 0.3981 -0.5973 0.5315

Se 0.5764 0.6552 0.1554 0.1448

La 0.3754 0.2500 0.0078 0.7631

Proportion 31.0 % 25.6 % 17.4 % 12.2 %

Table A3. Varimax normalized factor loadings for bulk compositions of 24 phosphorites from the Lisburne Group, northern Alaska. 

[Significant loadings of ≥0.5 are shown in bold type]

Element Factor 1 Factor 2 Factor 3 Factor 4

Si -0.0165 0.0197 -0.1160 -0.6514

Al 0.3468 0.1996 0.6890 0.0620

Fe -0.0426 -0.0771 0.6044 -0.0386

Mg -0.0433 -0.1026 0.8228 0.2888

Ca 0.7760 -0.1216 0.0494 0.4230

K 0.2476 0.0142 0.6215 -0.2391

Ti -0.2951 0.2746 0.7959 0.0133

P 0.8596 0.2490 0.2121 0.0904

F 0.6522 0.3676 0.2799 -0.1809

Corg 0.4307 -0.3136 -0.1331 0.5435

V 0.3252 -0.0984 0.5245 0.1863

Cr 0.0656 0.6160 0.1572 -0.1603

Ni -0.4099 0.3009 0.0235 0.7653

Cu -0.1962 0.1065 0.0775 0.7454

Zn 0.2745 0.0206 0.2657 0.7526

Mo -0.8714 0.1239 -0.0291 0.1173

Sr 0.8211 0.1693 -0.1265 0.2333

U 0.1534 0.2110 -0.1887 0.6888

Ba 0.0508 0.0721 0.7415 0.0566

Y 0.0946 0.9075 0.0241 0.1904

La 0.0033 0.9294 -0.0136 0.1974

Ce -0.5267 0.7768 -0.0919 0.1888

Gd -0.7301 0.6242 -0.1348 0.1802

Yb -0.8676 0.3700 -0.0838 0.1737

 Proportion 23.5 % 16.0 % 15.5 % 14.9 %

Table A1. Complete geochemical data from black shales and phosphorites from the Lisburne Group, northern Alaska.—Continued

Sample no. CCP-1.8 CCP-3.7 CCP-4.85 CCP-10.1 JS-05-82A JS-05-82B 00AD4A 03AD27C 03AD27L

Rock type Phosphorite Phosphorite Phosphorite Phosphorite Phosphorite Phosphorite Phos. nodule Phos. nodule Phos. nodule

Latitude 68o17.500’ 68o17.500’ 68o17.500’ 68o17.500’ 68o28.906’ 68o28.906’ 68o17.370’ 68o23.662’ 68o23.662’

Longitude 152o01.061’ 152o01.061’ 152o01.061’ 152o01.061’ 155o42.703’ 155o42.703’ 163o22.040’ 162o27.326’ 162o27.326’

Y 435 105 215 124 199 281 308 94.4 247

La 218 55.6 94.3 57.4 90.7 153 84.6 40.9 122

Ce 34.2 7.57 27.9 7.45 15.9 28.7 114 55.4 201

Pr 23.9 5.68 11.2 4.90 9.90 22.1 21.7 8.05 28.3

Nd 79.6 18.4 38.9 16.4 34.8 78.0 98.8 34.5 127

Sm 15.4 3.50 8.09 3.08 6.65 15.1 25.0 8.58 33.8

Eu 3.680 0.888 1.960 0.825 1.710 3.710 7.221 2.319 8.932

Gd 22.9 5.37 11.8 5.68 8.36 17.4 30.0 9.41 34.7

Tb 3.42 0.78 1.89 0.89 1.53 3.05 5.16 1.78 6.40

Dy 21.2 5.02 11.8 6.06 10.5 18.6 31.6 10.7 36.0

Ho 5.30 1.33 3.06 1.68 2.63 4.21 6.73 2.41 7.08

Er 17.0 4.23 9.87 5.71 8.89 13.1 20.1 8.32 21.7

Tm 2.380 0.623 1.440 0.855 1.390 1.810 3.031 1.329 3.080

Yb 14.0 3.85 8.98 5.52 9.19 10.9 17.6 8.49 17.5

Lu 2.100 0.593 1.410 0.890 1.420 1.570 2.842 1.358 2.543

Ce/Ce*SN 0.102 0.091 0.188 0.091 0.114 0.111 0.612 0.702 0.790

Eu/Eu*SN 1.027 1.089 1.018 1.017 1.088 1.100 1.282 1.198 1.216
Produced in Menlo Park, California

Manuscript approved for publication February 3, 2011

Edited by Tracey Suzuki

Layout by David R. Jones
Dumoulin and others—Depositional Setting and Geochemistry of Phosphorites and Metalliferous Black Shales—Professional Paper 1776-C