U. S. DEPARTMENT OF THE INTERIOR 

U. S. GEOLOGICAL SURVEY

GEOLOGIC IMPLICATIONS OF DATA FROM THE AMERICAN QUASAR 27-22 

HAGENBARTH DRILLHOLE, BEAVERHEAD COUNTY, MONTANA

by 

William J. Perry, Jr. 1

OPEN-FILE REPORT 98-30

This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey 

editorial standards.

1 MS 939, Federal Center 

Box 25046 

Denver, CO 80225-0046
GEOLOGIC IMPLICATIONS OF DATA FROM THE AMERICAN QUASAR 

27-22 HAGENBARTH DRILLHOLE, BEAVERHEAD COUNTY, MONTANA

by 

William J. Perry, Jr.

INTRODUCTION

The American Quasar 27-22 Hagenbarth was drilled to a total depth of 12,048 ft 

(3,672 m) as a rank-wildcat exploratory test for oil and gas in the south-central part of the 

McCartney Mountain salient, a second-order salient within the northern part of the 

southwestern Montana recess of the Cordilleran thrust belt (fig. 1, table 1). The Hagenbarth 

drillhole is significant for a number of reasons: (1) it reached crystalline basement; (2) it 

appears to have encountered a thin sequence of Proterozoic Belt sandstone just above 

crystalline basement and thus appears to help define the southern margin of the Belt 

embayment in this area; (3) thermal maturation data, analyzed from cuttings of this drillhole, 

help define the oil and gas potential of the region, and (4) a close comparison of the 

computed thicknesses of the different units encountered in the drillhole with nearby surface 

sections help better define paleotectonic features in the area surrounding the McCartney 

Mountain salient.

The geology of the McCartney Mountain salient was principally studied by Brumbaugh 

(1973), Brumbaugh and Hendrix (1981), Brandon (1984) and Schmidt and others (1988). 

Lopez and Schmidt (1985, fig. 7) show an east-west structural section, near the drillhole, 

based in part on a seismic reflection line. They interpret an east-vergent thrust complex, 

containing abundant imbricated thrusts of relatively small individual (generally less than 1 km) 

displacement (Lopez and Schmidt, 1985, fig. 7 ; Schmidt and others, 1988, fig. 23). I 

measured the length of the Triassic/Permian (Mz/P) contact on their cross section to be 40.8 

km over a horizontal distance of 22.3 km. The indicated shortening is thus 18.5 km over an 

estimated original distance of 40.8 km. The shortening ratio Al/lo , where Al is the shortening 

in km and lo is the calculated original distance in km, is 0.4534 which rounds to 45% 

shortening. Thus, in spite of the modest amount of shortening represented by any one 

thrust, the cumulative shortening in the McCartney Mountain salient is quite significant.

A preliminary K/Ar date of 70 ± 1.5 my from a stock that cross-cuts the thrusts, 

reported by Brumbaugh (1973), has been widely used to date this part of the thrust belt 

(Ruppel and Lopez, 1984; Schmidt and others, 1988). It should be emphasized that this may 

be younger than the bulk of the thrusting in the area, but contractional deformation farther 

east, along the eastern edge of the Helena salient (fig. 1) continued into the late Paleocene 

and earliest Eocene (Harian and others, 1988).

ACKNOWLEDGMENTS

I wish to thank officials with the former American Quasar Petroleum Company for 

providing logs and cuttings from the 27-22 Hagenbarth drillhole; Juanita McKenzie, formerly 

with USGS, for laboratory preparation and description of cuttings obtained from American 

Quasar; Jerry L. Clayton, USGS, for providing RockEval results, Alonzo H. Love, USGS, 

for kerogen color and TAI; Mark J. Pawlewicz, USGS, for vitrinite reflectance 

measurements, and Charles A. Sandberg, USGS, forconodont age and CAI results as well 

as helpful suggestions concerning the present report. I also wish to thank J. Michael O'Neill 

for many helpful comments.
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Figure 1. Index map showing front of Cordilleran thrust belt in Montana as well as tectonic 

features described by Perry and others (1989). Location of 27-22 Hagenbarth drillhole 

shown by dry hole symbol just below MMS. BMS - Blacktail Mountains salient; BSU - 

Blacktail Snowcrest uplift; MMS - McCartney Mountain salient.
EXPLANATION OF TABLE 1 WJP 12/04/97

Formation and member tops and bases, in the American Quasar 27-22 Hagenbarth drill-holes (table 

1) are based primarily on my interpretation of the borehole compensated sonic log, both sonic and 

gamma ray curves, in conjunction with the formation density log and mudlog record of lithology of 

returned drill cuttings. I calculated formation thicknesses from drilled intervals (log tops minus log 

bases) based on the publicly released dipmeter1 arrow plots (dip azimuth vs. dip magnitude) for the 

drill-hole interval 1,002 to 7,918 ft. I used an eyeball average for consistent (more than three) nearby 

readings, eliminating data scatter that is likely due to fractures, cross-stratification, or miscorrelation of 

resistivity curves:

For Cretaceous rocks at less than 1,810 ft - - - -12° N

1,810-3,000 ft ------------------- -15° N

3,000-3,960 ft ------------------- -15° NW (based on data from 3,810-3,900 ft)

3,960-4,610 ft ------------------- -17° NW (consistent dips from 3,900-4230 ft

range from 10-25° NW) 

4,610-5,385 ft ------------------- -19° N (consistent dips from 4,900 to 5,000

range from 15-22° N) 

5,385-5,570 ft ------------------- -20° NW (consistent dips from 5,250-5,500

range from 18-22° NW) 

5,570-5,712 ft ------------------- -18° NW (consistently 18°NW, 5,550-5,585)

5,712-5,781 ft ------------------- -15° NW (consistently 15°NW, 5,690-5,780)

5,781-5,902 ft ------------------- -22° NW (consistently 22°NW, 5,825-5,900)

5,902-6,560 ft ------------------- -20° NW

6,560-6,782 ft ------------------- -18° NW (consistently 18°NW, 6,560-6,600)

6,782-7,245 ft ------------------- -26° WNW (consistent dips from 6,800-6,960

range from 20-30°WNW) 

7,245-7,300 ft ------------------- -26° WNW (consistent dips from 7,080-7,250

range from 18-33° WNW) 

7,300-7,442 ft ------------------- -32° W (consistent dips from 7,300-7,365

range from 28-42°W)2 

7,8802-11,909 ft ---------------- -18° NW (based on consistent dips from

7,884-7,918, ranging from 14-26° NW)

1. The dipmeter HOT logging tool uses "4 pads, 90° apart, mounted on hydraulically actuated arms" 

which provide focused "micro-resistivity curves" of the adjacent borehole margin, giving deeper and 

narrower penetration than the older three pad COM tool (Schlumberger, 1970, Fundamentals of 

dipmeter interpretation, p. 1). The four resistivity curves are normally matched by computer analysis; 

the released arrow plot specifies that it was obtained from a "cluster program", computed October 15, 

1980.

2. Dip magnitudes decrease from 7,770 to 7,774 ft from 45°NE to 42°NNE in a tight group of three; 

next reading is @ 7,790 ft: 23°N, followed by 13°NE @ 7,792 and 18°N @ 7,796 and 7,798 ft. Possible 

thrust fault @ 7,788 ft, based on GR-Sonic log character, is consistent with dip changes. Three 

relatively consistent attitudes are recorded from 7,802 to 7,814 ft: 56°W, 50°WSW and 58°WSW. Dips 

drop back to 188NW at 7,884 ft. Correction as follows: a = (7880-7788) x cos54.66667° = 53.207; b = 

(9158-7880) x cos!8° = 1215.45; a + b = 1268.66; rounds downward to 1268 ft estimated thickness of 

Mission Canyon.
TABLE 1. American Quasar 27-22 Hagenbarth, drilled in SE NW Sec. 27, T. 5 S., R. 9 W. (Lat.

45.3733TN Long. 112.70201°W), Beaverhead County, MT. This oil and gas test was completed 

as a dry hole (D&A) December 5, 1980, at a total depth of 12,048 ft. Ground surface elevation at 

the wellsite was 5,410 ft. KB elevation, the datum for the borehole logs, was 5,431 ft. A dipmeter 

arrow plot, available from 1,002-7,918 ft, was used to calculate estimated true thickness of drilled

intervals. True thickness [corrected.

Log Tops Drilled thickness for interpreted dip]

Stratigraphy ^tilf feet feet feet meters

Quaternary valley fill 0 265 265 81

Upper Cretaceous rock 265 2,085(?) 2,039(?) 621(?)

Frontier Formation 265 2,085(?) 2,039(?) 621(?)

Lower Cretaceous rocks 2,350(?) 1,253(?) 1,210(?) 369(?)

Blackleaf Formation 2,350(?) 845(?) 816(?) 157(?)

Vaughan Member 2,350(7) 730(?) 705(?) 215(7)

Flood Member 3,080 115 111 34

Kootenai Formation 3,195 408 394 120

Pryor Conglomerate Mbr. 3,528 75 72 22

Jurassic rocks 3,603 472 456 139

Morrison Formation 3,603 199 192 59

Ellis Group 3,802 273 264 80

Triassic rocks 4,075 1,310 842 257

Thaynes(?) Limestone 4,075 130 124 38

Woodside(?) Formation 4,205 405 387(?) 118

thrust fault or faults 4,610 NA

Thaynes(?) Limestone 4,610 125 119+ 36+

Woodside(?) Formation 4,735 405 383 117

Dinwoodie Formation 5,140 245 232 71

Permian rocks 5,385 517 487 149

PhosphoriaFm. 5,385 517 487 149

Blacktail Shale Member 5,385 185 174 53

Shedhorn Sandstone Mbr. 5,570 142 135 41

Tosi Chert Member 5,712 16 15.5 4.7

Retort Member 5,728 55 53 16

Meade Peak Member 5,860 3 2.8 0.85

Grandeur Member 5,863 39 36 11 

Pennsylvanian rocks

Quadrant Sandstone 5,902 658 618 188

Mlsslsslppian rocks 6,560 3,413 3,189 972

Snowcrest Range Group 6,560 882 796 243

Conover Ranch Formation 6,560 222 211 64

Lombard Limestone 6,782 463 416(?) 127

decollement or thrust fault(?) 7,030 NA

Kibbey Formation (siltstone) 7,245 197 169 52

Madison Group 7,442 2,531 2,407(?) 734(?)

Mission Canyon Formation 7,442 1,716 1,632(?) 497(?)

thrust fault? 7,788 NA NA NA

Mission Canyon Formation 7,788 1,370 1,268(?) 387(?)

Lodgepole Formation 9,158 812 775 236

Paine Member 9,495 475 452 138

Cottonwood Canyon Mbr. 9,970 3 2.9 0.87
TABLE 1 (continued).

Devonian rocks 9,973 645 613 187

Three Forks Formation 9,973 155 147 45

Sappington Member 9,973 29 27.6 8.4

Unit 1 (lower Bakken) 9,986 (16) (15) 5

Trident Shale Member 10,002 28 26.6 8

Logan Gulch Member 10,030 98 93 28

Jefferson Dolomite 10,128 490 466 142

Cambrian rocks 10,618 1,215 1,156 352

Pilgrim Dolomite 10,618 302 287 88

Park Shale 10,920 122 116 35

Meagher Dolomite 11,042 545 518 158

Wolsey Shale 11,587 163 155 47

Flathead Sandstone 11,750 83 79(?) 24(?) 

Precambrian? sedimentary

rocks (Belt?) 11,833 76(?) 72(?) 22(?) 

Precambrian metamorphic

rocks 11,909

Total Depth 12,048
METHODS

Formation and member tops, in the American Quasar 27-22 Hagenbarth drillhole 

(table 1), are based primarily on my interpretation of the borehole compensated sonic and 

gamma ray (BHC/GR) log, in conjunction with the compensated neutron-formation density 

(FDC/CNL) log and log of lithology of returned drill cuttings, commonly known as a mudlog. 

These data were then compared with those of other drillholes from southwest Montana (Perry 

and others, 1981; Perry, 1986) as well as descriptions of stratigraphic units by Lowell (1949, 

1963), Pecora (1981), and Hildreth (1981). I calculated formation thickness from drilled 

intervals, picked on the BHC/GR log, on the basis of publicly released dipmeter arrow plots 

(dip azimuth vs. dip magnitude) for the drill-hole interval 1,002 to 7,918 ft. I used an eyeball 

average for consistent (more than three) nearby readings, eliminating data scatter that is 

likely due to fractures, cross-stratification, or miscorrelation of resistivity curves. As always, 

the reported depths of drill cuttings need to be adjusted to those of lithology changes 

indicated by the geophysical borehole log curves (table 1).

One- to 5-pound, cloth-bagged samples of borehole cuttings were obtained from the 

operator for 10 ft intervals from 9,820-10,270 ft, from the lower Lodgepole through upper 

Jefferson Formations. Cuttings from the intervals 9,820-50, 9,950-60 and 9,990-10,000 ft 

were processed for conodonts by C. A. Sandberg. Conodont elements and fragments of 

elements from all three intervals indicate a CAI of 3 (C.A. Sandberg, 1997, written 

communication). The bagged cuttings appear to be about 30 ft low at the base of the 

Lodgepole (9,973 ft, table 1) with respect to the BHC/GR log: well cuttings from the depth 

interval 9,990-10,000 ft which yielded Kinderhookian (basal Mississippian as well as basal 

Lodgepole) conodonts, reported by C.A. Sandberg (1997, written communication). Lag 

(depth of cuttings vs. geophysical borehole depths) appears to vary, as black shale of the 

Cottonwood Canyon? Member of the Lodgepole Limestone (upper Bakken equivalent?) first 

appears in the cuttings in the interval 9,980-90 ft (10% shale); the gamma radiation marker 

on the gamma ray-sonic log places the Cottonwood Canyon at 9,970-9,973 ft. The 

proportion of black shale to limestone climbs to 95% black shale in the interval 10,000-10 ft 

and is approximately 90% in the interval 10,010-20 ft. The strong gamma radiation marker 

for the basal black shale of the Sappington Member of the Three Forks (lower Bakken 

equivalent?) is from 9,986-10,002 ft (table 1) based on geophysical borehole logs. Here the 

lag appears to be of the order of 14 to 18 ft, consistent with the organic carbon values 

reported (table 2). The usual downhole contamination from borehole cavings complicates the 

story; shales cave much more readily than carbonate rocks.

The interval 9,820-10,100 ft, which spanned expected Lower Mississippian through 

Upper Devonian potential hydrocarbon source rocks, was analyzed by Rock-Eval pyrolysis 

(Jerry Clayton, 1981, written communication). Organic carbon (TOG) determinations of these 

26 samples were conducted by Rinehart Laboratories, Inc. Both sets of results are 

summarized in table 2. Rock-Eval pyrolysis is the controlled heating of a rock sample under 

dry conditions. It is currently the most common laboratory screening technique in 

hydrocarbon source rock evaluation (Bordenave and others, 1993) and was conducted on 26 

samples in conjunction with the present study (table 2). Tmax is the temperature in °C 

(degrees Celsius) recorded for the maximum generation of hydrocarbons from kerogen, the 

insoluble organic material in the cuttings, during the artificial maturation caused by dry 

pyrolysis. It is a measure of thermal maturity. The high-temperature end of the oil window in 

source rocks occurs at a Tmax of about 460°C (Tissot and Welte, 1978, p. 454, fig. V.1.16). 

More recently, Bordenave and others (1993, fig. 2-17) showed that the oil and gas window 

varies slightly for different types of organic matter. Highly mature Type III organic matter can 

give Rock-Eval TOG values as much as 48 percent lower than actual (Bordenave and others, 

1993, table 2-4), because 600° combustion does not completely oxidize such material. The 

boldface values of Tmax (table 2) for samples containing more than 0.9% TOG are believed
Table 2.

Organic carbon (TOC) and Rock-Eval analyses well cuttings - American Quasar 27-22 Hagenbarth drillhol

DEPTH (ft)

9,820-30

9,830-40

9,850-60

9,850-60

9,860-70

9,860-70

9,870-80

9,870-80

9,880-90

9,880-90

9,890-9,900

9,890-9,900

9,900-10

9,900-10

9,910-20

9,910-20

9,920-30

9,920-30

9,930-40

9,940-50

9,940-50

9,950-60

9,960-70

9,970-80

9,980-90

9,990-10,000

10.000-10

10.000-10

10.010-20

10.010-20

10.020-30

1 0.030-40

1 0.040-50

10.060-70

10.070-80

1 0.080-90

10,090-100

10,090-100

FORMATION

Lodgepole

-do-

-do-

-do-

-do-

-do-

-do-

-do-

-do-

-do-

-do-

-do-

-do-

-do-

-do-

-do-

-do-

-do-

-do-

-do-

-do-

-do-

-doThree Forks

Sappington

-dolower Bakken

lower Bakken

-do-

-doTrident Mmbr

Logan Gulch

-do-

-do-

-do-

-do-

-do-

-do-

%TOC

0.88

0.88

0.89

0.85

0.83

0.79

0.82

0.36

0.36

0.83

0.78

0.38 0.39

0.77

0.27

0.29

0.16 0.18

0.54

0.60

6.98 7.01

3.50

0.40

0.32

0.40

0.55

0.34

0.23

0.40

S1

0.049

0.051

0.154

0.095

0.056

0.048

0.269

0.082

0.076

0.071

0.054

0.038

0.046

0.017

0.046

0.047

0.001

0.157

0.054

0.062

0.007

0.047

0.072

0.012

0.057

0.005

S2

0.148

0.081

0.091

0.313

0.214

0.057

0.160

0.087

0.101

0.039

0.441

0.099

0.189

0.043

0.129

0.057

0.283

0.149

0.104

0.076

0.032

0.161

0.122

0.030

0.198

0.086

0.111

0.152

0.098

0.036

0.154

0.027

0.154

0.152

0.071

0.163

0.073

0.029

S3

0.35

0.37

0.42

0.32

0.35

0.33

0.38

0.31

0.34

0.37

0.23

0.35

0.32

0.36

0.34

0.45

0.25

0.24

0.25

0.21

0.33

0.36

0.26

0.24

0.2

0.18

Tmax1

379

359

355

433

355

436

364

439

356

441

372

437

370

436

360

427

372

442

356

361

421

362

367

339

337

369

355

522

360

526

365

357

360

361

358

360

357

443

S1+S2

0.197

0.132

0.558

0.366

0.303

0.188

0.809

0.314

0.262

0.503

0.158

0.146

0.207

0.139

0.075

0.245

0.087

0.420

0.188

0.216

0.034

0.201

0.224

0.083

0.22

0.107

HI

17

9

45

32

30

18

66

64

22

55

27

14

60

42

17

37

14

4

4

39

8

39

28

21

71

25

1. The boldface Tmax values are considered the most reliable; these indicate late postmaturity with respect to oil; dry 

the expected hydrocarbon.
the most reliable. These are well above the oil window. The S, peak (table 2) is a measure 

of hydrocarbons that exist in a rock sample and "can be used as a tool to detect migrated 

hydrocarbons" (Bordenave and others, 1993, p. 241). The S2 peak represents hydrocarbons 

produced by heating of kerogen (Types I, II III). It "gives a reasonable evaluation of the 

current [hydrocarbon generation] potential of a rock sample"; 70-80 percent of Type I, 45-50 

percent of Type II, and only 10-25 percent of Type III kerogen are transformed into 

hydrocarbons during pyrolysis (Bordenave and others, 1993, p. 242). Rocks with S2 < 4 mg/g 

of sample have low or no hydrocarbon generation potential; S2 between 4 and 8 indicates fair 

potential (Bordenave and others, 1993, p. 260). None of our samples had S2 values as high 

as 0.5 (table 2). The S3 peak is a measure of carbon dioxide generated in the sample during 

pyrolysis of oxygen-bearing organic compounds. It is recorded below 400°C because of 

thermal decomposition of some carbonates and other poorly crystallized inorganic crystalline 

materials occurs at higher temperatures. The accuracy of this peak is low for rocks with low 

organic content (TOC < 0.5 percent, especially those containing a large amount of siderite), 

affecting the oxygen index [Ol], computed from S/TOC. The hydrogen index [HI], computed 

from S/TOC, correlates well with H/C [atomic] ratios of kerogen. HI vs Ol diagrams are used 

in classifying Types I, II, and III kerogen (Bordenave and others, 1993, p. 251). PI (table 2), 

the production index, is the 8,7(8,+ S2) ratio, which increases mainly due to cracking of the 

kerogen (Bordenave and others, 1993, p. 252). Values lower than 0.05 indicate immature 

kerogens; 0.6 or higher values indicate almost all hydrocarbons have formed (Bordenave and 

others, 1993, p. 252). The low values of both S, and S2 obtained for our samples (table 2) 

render the PI results suspect.

STRATIGRAPHIC DISCUSSION

Mesozoic rocks. Although thicknesses of post-Triassic rocks in the Hagenbarth drillhole 

were not readily comparable with those of the nearby Armstead anticline and Blacktail 

Mountains to the south (fig. 2 and table 3), no obvious thrust faulting was observed from the 

borehole data above 4,610 ft. The Cretaceous Frontier/Blackleaf contact is obscure. My pick 

(at about 2,350 ft) is based on a downward increase in abundance of volcaniclastic material, 

assigned to the Vaughan Member of the Blackleaf Formation, and a downward decrease in 

gray-green shale and siltstone, typical of the lower Frontier. The underlying Flood Member of 

the Blackleaf contains interbedded black shale, light-gray siltstone, and sandstone. The 

underlying Kootenai has a dip-corrected thickness of 394 ft, with the distinctive Pryor 

(Cloveriy) Conglomerate Member at the base (fig. 3). Jurassic rocks have a dip-corrected 

thickness of about 472 ft (table 1). Repetition of lithologies and log characteristics occurred 

in the Triassic interval, indicating that a thrust fault was probably encountered at a log depth 

of 4,610 ft. Average dip appears to increase from 17° NW to 19° NW at this depth (see 

explanation of table 1); 530 ft of section is repeated. The interval assigned to the Triassic 

(table 1) is estimated to have been originally slightly more than 840 ft thick, close to the 700- 

800 ft thickness given by Lowell (1949). On the surface, in the Blacktail Mountains to the 

south, the entire Triassic section is placed in the Dinwoody Formation (Pecora, 1981). 

However the Triassic sequence encountered in the Hagenbarth drillhole appears more like 

that observed south and east of Lima (Perry, 1986): an upper limestone (Thaynes), a thick 

middle sequence of brick-red shale, light-red calcareous siltstone and minor limestone 

(Woodside), and a lower gray-brown to medium- to dark- gray limestone (Dinwoody). 

Regionally the Triassic sequence thickens southward in outcrop, from 430 ft in the Blacktail 

Mountains to 1,315 ft in the Blacktail Road area in the Snowcrest Range (table 3). However, 

undivided Triassic rocks are also about 430 ft thick near Melrose north of the drillhole site 

(J.M. O'Neill, 1997, written communication). The dip-corrected Triassic thickness and likely 

presence of both Thaynes and Woodside Formations in the Hagenbarth drillhole appears

8
DEER LODGE COUN

W SILVER BOW COUNTY 5? ,? ! SS?S I......^ffffKffI ftW:

COUN

* i \ m%, i &, ^ . .... . -j-^^^. I J. " " '^" ' ' : £&£. -^ILm

Figure 2. Index map of a portion of southwestern Montana showing the location of the Hagenbarth 

drillhole and nearby localities: AA - Armstead anticline; Blk Mns - Blacktail Mountains. Highlands 

are shaded. Drillhole 1 is American Quasar 9-1 May-Federal; 2 is American Quasar Petroleum 29-1 

Rebish; 3 is North American Resources 3-8-4-5; 4 is North American Resources 7-23 State.
Table 3. Thickness Comparisons of Stratigraphic Units 

Stratigraphic columns 1

Age

Late Cretaceous 

Early Cretaceous

Cretac. & Jurassic

Jurassic, undiv.

Triassic, undiv.

Permian

Pennsylvanian

Mississippian

Devonian

Cambrian

Formation

Frontier

Blackleaf Fm. 

Kootenai Fm.

Kootenai+Morrison

Phosphoria Fm.

Quadrant Ss.

Conover Ranch 

Lombard 

Kibbey Ss.

Snowcrest Range Grp

Mission Canyon Fm. 

Lodgepole Ls.

Three Forks

Jefferson Fm.

Pilgrim Dol. 

Park Shale 

Meagher Dol. 

Wolsey Shale 

Flathead Ss.

Total Cambrian

27-22 

Hagenbarth

2,039(?)

816(?) 

394

866

472

842

487

618

211 

416 

169

796

1,632(1,268) 

775

109

466

287 

116 

518 

155 

79

1,155

Armstead anticl. 

(Hildreth (1981)

-1,100

-100 

-450

-550

1,700 

1,100

94

550

98

-100 

95

293

Blacktail Range 

(Pecora, 1981)

1,080

430

358

725

88 

-696 

175

959

812 (850 Huh2) 

753 (990 Huh)

60

118

122 

92 

553 

61 

50

878

-1

3

-1

1. Thicknesses in feet

2. Alternative thicknesses from measured sections by Byrne (1985), Flanagan (1958), Gealy (1953), Huh (1968), M

and Scheedlo (1984).
GAMMA RAY LOG SONIC LOG

IN API UNITS , IN MICROSECONDS/FT 

0.0 150.0 140 4

IF*~ *-*,

 -iK

|r

 «?~

-i

"ST""'

""">

3UZ

310

320 

33CX 

340(

370C

BLACKLEAF FORMATION ^ 

VAUQHAN MEMBER "^^

~~^

FLOOD MEMBER "~=^, »* . _

"":!> _

KOOTENAI FORMATIOW;^

-i_. _

"^

:5pr

PRVOR CONGLOMERATE -^T""^ 

MEMBER *~~=^T,

CRETACEOUS "" ^

JURASSIC .^^fifL

MORRISON FORMATION ^

^

Figure 3. Lower Cretaceous and probable Cretaceous/Jurassic boundary section of BHC/GR log, 

American Quasar 27-22 Hagenbarth drillhole.

11
anomalous, based on both the above references and Peterson (1985, fig.15). Possibly, dips 

get very steep close to the thrust fault, so that my dip corrections may be insufficient; possibly 

smaller contraction faults exist near the larger thrust fault at 4,610 ft log depth. However, the 

dip-corrected thickness of Woodside(?) turned out the same both above and below the thrust, 

405 ft, suggesting that the total Triassic thickness in the area of the drillhole may indeed 

exceed 800 ft. Paull and others (1989) report the presence of Thaynes in their nearby 

incomplete Birch Creek section (SW 1/4, sec. 24, T. 5 S., R. 10 W.), where Moritz (1950) 

earlier reported a total Triassic thickness of 885 ft.

Upper Paleozoic rocks. The dip-corrected thickness of Permian (487 ft), Pennsylvanian 

(618 ft), and Mississippian strata (3,635 ft) in the Hagenbarth drillhole (table 1) is more 

consistent than that of the drilled Triassic sequence with reported thicknesses in the region 

(table 3). The Mississippian assignment of the Conover Ranch (formerly Amsden Formation) 

follows Wardlaw and Pecora (1985).

The Permian Phosphoria Formation is comprised of from top downward, 142 ft of 

Shedhom Sandstone Member, underlain by about 16 ft of the Tosi Chert Member. The 

underlying Retort Phosphatic Shale Member, is about 53 ft thick, and the Meade Peak, 23 ft 

farther downhole, is slightly less than 3 ft thick based on gamma ray signature on the 

BCS/GR-log. The Retort has excellent oil-source-rock potential to the south, in the Blacktail 

Mountains (Claypool and others, 1978). The basal Grandeur Member (36 ft thick, table 1) is 

predominately dolomite.

The BCS/GR-log base of continuous sandstone in the Pennsylvanian Quadrant 

Sandstone occurs at 6,520 ft (based on abrupt increase downward to carbonate velocities at 

this depth). The interval 6,520-40 ft appears to be predominately dolomite; then lower 

interval travel times versus low gamma ray response strongly suggests that the basal 20 ft of 

Quadrant (6,540-6,560 ft) is again sandstone. Drill cuttings show considerable lag here 

(about 50 ft) with the mudlog base of the Quadrant about 6,610 ft. Dolomite predominates in 

the cuttings from 6,700 to 6,850 ft, described as silty to argillaceous, with red to dark-gray 

shale logged from about 6,600 to 6,750 ft, comprising 50% of the cuttings from 6,680-6,700 ft 

on the mudlog. Based primarily on the BCS/GR log, I interpret the interval 6,560-6,782 ft as 

Conover Ranch Formation (table 1), formerly the "Alaska Bench" of E. K. Maughan (oral 

communication, 1982). The interval from 6,782 to 7,245 ft is limestone dominated, with 

abundant interbedded shale indicated on the gamma ray-sonic log. The limestone is 

predominantly dark gray to tan, fine grained, and dolomitic in part, according to the mudlog. 

Velocities are generally higher in this interval than either directly above or below. The basal 

150 ft is virtually continuous limestone as in the basal Lombard Formation in the Snowcrest 

Range to the south. I classify this entire unit (6,782-7,245 ft) as Lombard Limestone.

At 7,300 ft the mudlog lags the gamma ray-sonic log by about 50 ft. The interval 

7,245-7,442 ft is predominantly orange siltstone with occasional sandstone and sandy 

dolostone of the Kibbey Formation as exposed in the Blacktail Mountains and Snowcrest 

Range (Pecora, 1981; Perry and others, 1988). The interval 6,560-7,442 ft comprises the 

Snowcrest Range Group of Wardlaw and Pecora (1985). My calculated thicknesses are 796 

ft for the group and 211 ft for the Conover Ranch, 416 ft for the Lombard, and 169 ft for the 

Kibbey (table 1). Based on the regional nature of this interval, tightly folded on the Armstead 

anticline, and imbricately thrusted in the Blacktail and Tendoy Mountains, it is unwise to trust 

these computed thicknesses. Additionally, the regional seismic section (Lopez and Schmidt, 

1985) requires a decollement in this interval, close to and above the Mission Canyon 

Formation, possibly at about 7,030 ft, based on comparison of the BCS/GR and other 

geophysical borehole logs.

12
The Mission Canyon may be partly repeated by thrusting, with a thrust fault 

encountered at about 7,788 ft repeating the upper 346 ft drilled interval of Mission Canyon 

(see footnote 2 to the explanation of table 1). According to descriptions of cuttings on the 

mudlog, the Mission Canyon is a medium- to dark-gray partly dolomitic micritic limestone 

which contains abundant calcite-filled fractures. Below 9,000 ft, fossil fragments are logged 

on the mudlog; I used the gamma ray log break at 9,158 as the top of the Lodgepole (table 1 

and fig. 4), but the upper member of the Lodgepole - the Woodhurst Member - is very 

fossiliferous on the Armstead anticline and in the Highland Mountains northeast of the 

drillsite. The contact may thus be higher than suggested by the gamma ray log. Below 9,500 

ft, the Lodgepole becomes predominantly very dark-gray, very fine-grained, and not visibly 

fossiliferous limestone, typical lithology of the Paine Member of the Lodgepole, as observed 

on the east flank of the Armstead anticline. At the base of the Paine Member of the 

Lodgepole, 9,970 ft by BCS/GR log response, the mudlog lags the gamma ray-sonic log by 

about 30 ft. Thus the reported depths of cuttings analyzed both for conodonts, TOC, and 

RockEval (table 2) are off BCS/GR log depth by this amount near the base of the 

Mississippian. The Cottonwood Canyon Member of the Lodgepole, the "Upper Bakken" 

equivalent of the oil and gas industry, is represented by an abrupt increase in natural gamma 

radiation from 9,970-9,973 ft on the BCS/GR log (fig.4). Total thickness of Mississippian 

rocks penetrated by the Hagenbarth drillhole is about 2,840 ft.

Lower Paleozoic rocks. The Devonian-Mississippian contact is placed at 9,973 ft. All three 

members of the directly underlying Devonian Three Forks Formation can be recognized by 

BCS/GR log response (fig.4), although the typical green shale of the Trident member was not 

recorded on the mudlog. The Three Forks appears to be about 147 ft thick in the 

Hagenbarth drillhole. The gamma ray intense black shale of unit 1 (lower Bakken) at the 

base of the Sappington Member is 15 ft thick (table 1 and fig. 4). The recorded TOC of 3.5 

to 7% from this Interval (table 2) may be low, due to uphole contamination of the cuttings 

analyzed. First appearance of tan to light-brown Logan Gulch dolostone in the cuttings at 

10,060 ft versus the BCS/GR log top at 10,030 ft, indicates that the mudlog tops are 30 ft low 

with respect to the BCS/GR log, the same lag found at the base of the Mississippian.

The Jefferson Formation, 466 ft thick in the Hagenbarth drillhole, is primarily light- to 

medium- and dark-gray dolostone, microcrystalline to finely crystalline, with traces of 

anhydrite. Medium-gray shale in this interval of the mudlog may represent cavings.

The top of the Cambrian was encountered at a depth of about 10,618 ft and is marked 

by transition to dark gray-brown laminated dolostone. The uppermost Cambrian unit, about 

287 feet thick In the Hagenbarth drillhole, is assigned to the Pilgrim Dolomite (after Lowell, 

1965, p.1; Pecora, 1981, p.19), although Sandberg (1997, written communication) identified 

this as Red Lion Formation at an outcrop 12 miles to the northeast. Lag in cuttings vs. 

BCS/GR log depths is only about 10 ft at the Pilgrim/Park Shale contact. The Park Shale, 

described as green to gray green and slightly silty on the mudlog, has a calculated thickness 

of 116 ft. The underlying Meagher Dolomite, about 518 ft thick, consists of predominantly 

dark-brown to dark gray-brown medium-crystalline to microcrystalline dolostone.

The BCS/GR log top of the Wolsey Shale occurs at a depth of 11,587 ft. Here, there 

is little if any sample lag as indicated by the mudlog top of the Wolsey at about 11,580 ft. 

The Wolsey is described as a green waxy to silty shale with interbedded light- to mediumgreen sandy siltstone. The Wolsey is calculated to be about 155 ft thick. The underlying 

Flathead Sandstone is 79(?) ft thick with a sharp base on the BCS/GR log at 11,833 ft. 

Beneath the Flathead is an approximately 72-ft-thick interval logged as quartzitic sandstone, 

white to pink, very fine to coarse grained, the base of which appears to be at about 11,909 ft 

on the BCS/GR log. The mudlog places the base of this sandstone at 11,960 ft. This interval

13
GAMMA RAY LOG SONIC LOG

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Figure 4. Lower Mississippian and Upper Devonian sections of BHC/GR log, 

American Quasar 27-22 Hagenbarth drillhole.

14
is interpreted as possibly a pocket of or near wedge edge of Proterozoic Belt sandstone. 

Beneath this sandstone the mudlog lists "granite/schist", undoubtedly high-grade 

metamorphic rocks. Pearson (1996) found 722 ft of possibly equivalent Middle Proterozoic 

Belt Supergroup, primarily "ferruginous, argillaceous, micaceous, feldspathic quartzite; red 

and green sandy and silty argillite; and thick-bedded coarse-grained to very coarse-grained 

feldspathic quartzite" in core from a shallow drillhole in the Argenta mining district about 20 

km northwest of Dillon, Montana.

THERMAL MATURATION AND HYDROCARBON POTENTIAL

Thermal maturity indicators obtained from Lower Mississippian and Upper Devonian 

cuttings from the Hagenbarth drillhole include conodont CAI, vitrinite reflectance, TAI, and 

Rock-Eval pyrolysis results. Conodont elements and fragments of elements were obtained 

from cuttings from the intervals 9,820-50, 9,950-60 and 9,990-10,000 ft; all three intervals 

indicate a CAI of 3 (C.A. Sandberg, 1997, written communication), postmature with respect to 

oil (fig. 5, Perry and others, 1983). Cuttings from the interval with the highest reported TOG, 

10,000-10,100 ft, yielded ordered vitrinite reflectance values ranging from 1.72 to 2.82; the 

median reflectance of the 57 ordered reflectance values obtained was 2.39; the mean 

reflectance was 2.36 with a standard deviation of 0.24 (Mark J. Pawlewicz, written 

communication, 1981), indicating late postmaturity with respect to oil (fig. 5, Perry and 

others, 1983), a slightly higher thermal maturity than indicated by the conodont CAI. Cuttings 

from the same interval were processed for kerogen color and TAI by A.M. Love. The dark 

brown kerogen color and TAI of 4 obtained, are consistent with the vitrinite results. Tmax 

results from Rock-Eval pyrolysis (in boldface for higher than 1 % TOG samples, table 2) 

reported by J.L. Clayton (written communication, 1981) also indicate late postmaturity with 

respect to oil. Low S2 results (table 2) indicate no or very low hydrocarbon generating 

capacity.

Unfortunately, no Permian cuttings were acquired for source rock analysis. Samples 

of the Retort (nos. 9-10, Claypool and others, 1978, table 2) from sec. 23, T. 9 S., R. 9 W., in 

the Blacktail Mountains to the south, ranged from 11.9% to 13.3% organic carbon and 

contained 16.8 to 18.9 parts/thousand extractable bitumen, excellent oil source rocks. A 

sample from the Pioneer Mountains to the west (no. 12, Claypool and others, 1978, table 2, 

sec. 3, T. 6 S., R. 11 W.), contained only 0.5% organic carbon and was supermature with 

respect to liquid hydrocarbon generation. By extrapolation, the Phosphoria in the 

Hagenbarth drillhole may also be supermature, but likely generated liquid hydrocarbons 

during Cretaceous maximum burial and high heat flow associated with magmatic activity.

CONCLUSIONS

The Hagenbarth drillhole appears to have encountered about 72 ft of Middle 

Proterozoic Belt quartzite beneath the basal Phanerozoic Flathead Sandstone; no Belt rocks 

are present on the Armstead anticline or Blacktail Mountains (fig. 2). Pearson (1996) shows 

that Belt rocks thicken rapidly to the north and west of the Hagenbarth drillhole. The 

encounter in the drillhole is the farthest southeast that Middle Proterozoic rocks have been 

reported.

The Hagenbarth drillhole provides critical data on the thickness and character of 

Paleozoic rocks north of Dillon. Cambrian strata are thicker than to the south and west (table 

3) in agreement with Peterson (1985). Ordovician through Middle Devonian strata are 

absent, also in agreement with Peterson (1985). Upper Devonian through lowermost 

Mississippian Bakkan-equivalent strata contain as much as 7% organic carbon and are 

supermature with respect to liquid hydrocarbons. The Lower Mississippian Madison Group is 

probably slightly more than 2,400 ft thick, apparently somewhat thinner than on the Armstead

15
anticline, but thicker than to the southeast (fig. 2; table 3). The presence of Upper Paleozoic 

Snowcrest Range Group (SRG) at this latitude is in agreement with Peterson (1985). The 

Kibbey Formation at the base of the SRG is a distinctive orange siltstone, about 170 ft thick 

in the drillhole, not significantly different than reported by Pecora (1981) in the Blacktail 

Mountains. The Pennsylvania Quadrant Sandstone is more than 600 ft thick and represents 

a potential hydrocarbon reservoir rock. The overlying Phosphoria Formation is about 487 ft 

thick, considerably thicker than the approximately 100 ft shown by Peterson (1985, fig. 14). 

The Phosphoria contains two black shale members, the Retort about 53 ft thick and the 

underlying Meade Peak, slightly less than 3 ft thick based on gamma ray signature.

About 842 ft of Triassic and 456 ft of Jurassic rocks are present in the Hagenbarth 

drillhole. The Triassic sequence is similar to that farther south as discussed above, such that 

Thaynes, Woodside, and Dinwoodie Formations are all three present. Thickness 

encountered is similar to that measured by Moritz (1950), nearby, but very different than 

estimated or measured by others as discussed at length above. The Jurassic sequence 

encountered consists of about 264 ft of Ellis Group and 192 ft of overlying Morrison 

Formation. If correct, this aggregate thickness of 456 ft of Jurassic rocks, far in excess of the 

less than 100 ft reported by Peterson (1985, fig. 16), requires rethinking the presence, 

location or size of his Jurassic 'Boulder high'. The overlying Lower Cretaceous sequence is 

subdivided into the Kootenai Formation, about 394 ft thick, and overlying Blackleaf 

Formation, about 816 ft thick, as discussed above. More than 2,000 ft of Upper Cretaceous 

Frontier Formation are present in the Hagenbarth drillhole; this siliciclastic formation extends 

nearly to the surface. Only 265 ft of Quaternary valley fill is present at the drill site. The 

broad Quaternary valley here is not underlain by Tertiary rocks.

16
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19