by

LEE C. GERHARD, SIDNEY B. ANDERSON, JULIE A. LEFEVER, and CLARENCE G. CARLSON

GEOLOGICAL DEVELOPMENT, ORIGIN,

AND ENERGY MINERAL RESOURCES

OF THE WILLISTON BASIN,

NORTH DAKOTA

MISCELLANEOUS SERIES 63 Reprinted from

The American Association of Petroleum Geologists Bulletin No.8, v. 66 NORTH DAKOTA GEOLOGICAL SURVEY (AugllSt. 1982), p. 989-1020. 36 Figs., 1 Table.

Don L. Halvorson, State Geologist

The American Asso~iation of Petroleum Geologists Bulletin v. 66, No.8 (Auguu 1982), P. 989-1020, 36 Figs., I Table

Geological Development, Origin, and Energy Mineral Resources of Williston Basin, North Dakota}

LEE C. GERHARD,' SIDNEY B. ANDERSON,' JULIE A. LEFEVER,> and CLARENCE G. CARLSON'

ABSTRACT

The Williston basin of North Dakota, Montana, South Dakota, aud south-ceutral Canada (Manitoba and Sas­katchewan) is a major producer of oil and gas, lignite, and potash. Located on the western periphery of the Phauerozoic North American craton, the Williston basin has undergone only relatively mild tectonic distortion during Phanerozoic time. This distortion is largely re­lated to movement of Preca mbrian basement blocks.

Sedimentary rocks of cratonic sequences Sauk through Tejas are present in the basin. Sauk (Cambrian-Lower Ordovician), Tippecanoe (Ordovician-Silurian), and Kaskaskia (Devonian-Mississippian) sequence rocks are largely carhonate, as are the major oil- and gas­producing formations. Absaroka (Pennsylvanian­Triassic) and Zuni (Jurassic-Tertiary) rocks have more clastic content, but carbonates are locally important. Clastics of the Zuni sequence (Fort Vnion Group) contain abundant lignite. Tejas (Tertiary-Quaternary) sequence rocks are not significant in the production of minerals or energy, although glacial sediments cover much of the region.

Oil exploration and development in the Vnited States portion of the Williston basin since 1972 have given im­petus to restudy basin evolution and geologic controls for energy-resource locations. Consequently, oil production in North Dakota, for instance, has jumped from a nadir ofl9 million bbl in 1974 (compared to a previous zenith of 27 million in 1966) to 32 million hbl in 1979 and 40 million bbl in 1980. Geologic knowledge of carbonate reservoirs has expanded accordingly.

Depositional environments throughout Sauk, Tip­pecanoe, and Kaskaskia deposition were largely shallow marine. Subtidal and even basinal environments were developed in the basin center, but sabkha deposits were abundant near the basin periphery. Evidence of subaerial weathering was commonly preserved in structurally high areas and on the basin periphery, especially in upper Kaskaskia rocks. Some pinnacle reefs were developed in Kaskaskia deposition. morphologically similar to the Silurian pinnacle reefs of the Michigan basin.

Clastic sediments were transported into the southern

part of the basin during Absaroka sequence deposition, a product oferosion of Ancestral Rocky Mountain orogenic structures. Continental and shallow marine clastic sedi­ments were deposited during Zuni sedimentation until Cretaceous deeper marine environments were estab­lished. Laramide orogenesis to the west provided detritus that was deposited in Ouvial, deltaic, and marginal marine environments, regressing to the east. Major lig­nite deposits are part of this postorogenic regressive rock body.

Major structures in the basin, and the basin itself, may result from left-lateral shear along the Colorado­Wyoming and Fromberg zones during pre-Phanerozoic time. Deeper drilling in the basin has revealed several major structures and given indications of others. Most structures probably resulted from renewed movement or "tensing" of pre-Phaneroroic faults. Meteorite impact events have been suggested as the origin for one or more structures.

INTRODUCTION

Recent successful oil exploration and development in the Williston basin have clearly demonstrated the inadequacy of previous tectonic and sedimentologic models of the basin to predict occurrences of mineral and fuel resources. The United States portion of the basin has sustained oil develop­ment during the last half of the 1970s that is remarkable in its definition of previously unrecognized structures, discovery of new producing zones, and high success rates. The largest single segment of the basin is the North Dakota portion (Fig. I), which includes the deepest part of the basin and the thickest Phanerozoic section. The wildcat success rate in North Dakota has steadily increased from 250/, in 1977; 28% in 1978; 33% in 1979; to 36% through the first 6 months of 1980, whereas the recent national average was 15 to 18% for a similar period (Johnston, 1980; Fig. 2). Although South Dakota and Montana also sustain active programs, their success rates are lower; Montana has the second most suc­cessful active drilling program in the basin.

Oil and gas are not the only mineral and energy resources

@1982. The Amencan ASSOCiation of Petroleum Geologists All nghts reserved.

'Manuscnpt received, July 10, 1981, revised and accepted, Apn114, 1982. 2North Dakota Geological Survey. Present address Union Texas Petro­

leum Company, Denver, Colorado 3North Dakota Geological Survey, University Station, Grand Forks, North

Dakota 58202. 4North Dakota Geological Survey. Present address: OIl and Gas DiVISion,

North Dakota Industrial Commission, Bismarck. North DaKota. Many of our colleagues, students, and cooperating SCIentists have spent

extensive amounts of time discussing ideas. providing data. and redirect-

Ing our efforts. In particular. James H. Clement of Shell Oil Co.; Cooper Land, consultant; and Walter Moore of the University of North Dakota have been Instrumental in construction of our ideas and approach. Other col­leagues and students who have contributed to this summary are Randolph Burke. Diane Catt, Tom Heck, John Himebaugh. Peter Loeffler, Tom Obelenus, and Nancy Perrin. Support for some of the original studies of depositional systems and reservOIr geology came from the North Dakota Geological Survey, the Carbonate Studies Laboratory of the University of North Dakota, and from a grant by the U.S. Geological Survey (14-08· 0001-G-591). All of the support is gratefully acknowledged.

989

990 Williston Basin, North Dakota

of the basin. Lignite reserves are huge and are actively being explored and utilized. Rich potash resources are being mined in Saskatchewan and a mine has been announced for western Manitoba. In North Dakota and Montana, potash resources are potentially far more valuable than the lignite, but are not yet being mined. Halite is being mined near Williston, North Dakota, from depths of 8,000 ft (2.438 m) making it proba­bly the world's deepest salt production. The halite deposits are vast, being approximately 1,700 mi' (7,086 km').

Coincident with energy development, interest in water resources (for energy transportation) and the overall regional economic significance of the basin has led to an extensive study of basin geology, with numerous programs of investi­gation under way. Programs of the Nonh Dakota Geological Survey, the U.S. Geological Survey, Depanment of Energy, and several oil companies deserve particular note; much of the information in this summary is derived from these sources.

The Williston basin is a slightly irregular, round depression in the western distal Canadian shield. Structural trends within the basin reflect major directional changes in the structure of the Rocky Mountain belt (Fig. 2). Several writers have hypothesized a wrench-fault system for control of basin geometry and structure (Thomas, 1974: Brown, 1978), al­though those studies did not integrate sedimentary depo· sitional facies and porosity development infonnation.

Approximately 16,000 ft (4,875 m) of sedimentary rocks are present in the deepest part of the Williston basin, south­east of Watford City, Nonh Dakota. The deepest well in the

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FIG. I-Index map showing location of Williston basin in United States and Canada. Modified from Worsley and Fuzesy (1978).

basin penetrated Precambrian rock at l5,340 ft (4,676 m); the deepest oil production is from 14,343 ft (4,372 m) in the Ordovician Red River Formation (Mesa 1-13 Brandvik, Dunn County, Nonh Dakota).

Rocks deposited during all periods of Phanerozoic time are present in the basin (Fig. 3). Paleozoic rocks are mainly carbonates, followed by the dominantly clastic Mesozoic and Cenozoic rock sequence. Sloss's (1963) sequence concept is particularly useful in the study of these rocks. serving to "package" major transgressive cycles of continental scale with accompanying sediment deposition. For this reason, discussions of stratigraphic units and their significance to

deciphering the structural evolution of the Williston basin are organized by sequences.

Few regional studies of Williston basin rocks have been published. Several important contributions used extensively in this paper are the papers of Poner and Fuller (1959), Carlson and Anderson (1966), the various papers presented in the Geologic Atlas of the Rocky Mountains (Mallory, 1972 a, b), and Macauley et al (1964). Several unpuhlished works of oil company geologists are also used in this paper, especially those of lames Clement (personal commun., oral dis­cussions, 1975-80).

Several cycles of interpretive writing are evident in the literature about the Williston basin. Each proceeds from an equivalent cycle of mineral or fuel development activity. This cycling of activities is common to most petroleum provinces. The Williston basin is in its third cycle of oil development now and is rapidly increasing oil production. Most of the United States pan of the Williston basin is contained in Nonh Dakota; its statistics are impressive. After reaching a high of 27 million bbl of oil produced in 1966, production declined to 19.5 million bbJ in 1974. During the third cycle of develop­ment, production began to increase in ]975, reaching a new historic high of 32 million bbl in 1979, increasing to 40 million bbl for 1980. Concurrent with this cycle of develop­ment. research into oil and gas reservoir geology, regional depositional systems, and other aspects of basin analysis has been revived with applications of technology developed since the mid-1960s. Summary papers of this era are included in Estelle and Miller (1978) and in several publications of the Nonh Dakota Geological Survey (Bjorlie, 1979; Carroll, 1979: Bluemle et ai, 1980; Scott, 1981: Lerud, 1982). Various orally presented papers at national and regional society tech­nical programs also added ideas and data to the present exploration cycle.

The purpose of this paper is to summarize briefly the current knowledge of the geologic evolution and energy resources of the North Dakota ponion of the Williston basin. As in any summary paper, this effort is colored by the geolog­ical philosophies and biases of the writers .

TECTONIC SETTING

The Canadian shield extends under the Williston basin to the Cordilleran geosyncline. The Williston basin forms a large depression in the western edge of the shield, occupying much of North Dakota, nonhwestern South Dakota, the eastern quarter of Montana, a significant part of southern Saskatchewan, and a portion of southwestern Manitoba. This part of the craton is bordered on the south by the Sioux arch,

Lee C. Gerhard el al 991

on the southwest by the Black Hills uplift and Miles City Churchill provinces of the Canadian shield. Stratigraphic and arch, and on the west by the Bowdoin dome (Fig. 2). gravity studies suggest that this boundary is an important

Structural grain of the region appears to be related to the factor in Phanerozoic basin development. offset in the Rocky Mountain chain between the north­ Structural trends within the Williston basin reflect both the trending southern Rocky Mountain province and the north- and northwest-trending grain of the Rocky Mountain northwest-trending northern Rockies indicated by propri­ province. The Cedar Creek and Antelope anticlines are etary seismic data. The zone of offset in Wyoming and northwest-trending structures: the Poplar anticline is slightly Montana (centra] Rockies) is characterized by northwest divergent from the~ but is also generally northwest trending. structural grain of basin and range configuration. Regional The Nesson, Billings, and Little Knife anticlines are north­wrench faulting along the Cat Creek and Lake Basin zones trending structures. An additional northwest-trending struc­(Thomas, 1974) suggests to us that structural control of the ture, which is an extension of the Antelope anticline in the Williston basin is related to large-scale "tears" in the edge of southeast part of the basin, has been mapped in the course of the craton. preparation of this paper (Bismarck-Williston zone).

Ballard (]963) outlined a hinge line for the eastern part of Several smaller structures on the eastern shelf have been the Williston basin in central North Dakota (see also Laird, mapped by Ballard (1963); those in Foster and Stutsman 1964), which is the boundary between the Superior and Counties are probably important. The Cavalier high (Ander­

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___ ~_;;I;"_________ 1'-' MA~ToeAF------------------ ~SASKATCHEWAN NfwPORTE..",,,, ----rP/---------­~-<; ~ I~STRUCTURE

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FIG. 2-Major structures of Williston basin based on current subsurface structural mapping and geophysical interpreta­tions.

992 Williston Basin, North Dakota

-

tl SYSTEMS ~ ROCK UNITS

0..• PLEISTOCENEQUATERNARY •«

~

!" WHITE RIVER GOLDEN VALLEY

TERTIARY FORT UNION GROUP

HELL CREEK

FOX HILLS

PIERRE

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CRETACEOUS z ::;) N EAGLE

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MOWRY NEWCASTLE

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SPEARFISH "unrnfric:ted"

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CIl FR08ISHER 0 A~~~,c INT 2 TILSTON

c BOTTINEAU

" INTERVALCIl c CIl"c BAKKEN ~

THREE FORKS 5 BIRDBEAR

11 DUPEROW

~c!

SOURISDEVONIAN - - ­ RIVER

DMSON BAY ..~ PRAIRIE;;5..... .-. WINNIPEGOSIS2e

ASHERN

INTERLAKESILURIAN ~ Z C ------.ju STONEWALLIII A.

STONY NTN.A.

~ ORDOVICIAN REO RIVER

WINNIPEG GROUP

"CAMBR<rORD. DEADWOOD~ PRECAMBRIAN

FIG. 3-Generalized stratigraphic column of Williston basin.

993 Lee C. Gerhard ot al

son, 1974) is apparently a paleotopographic artifact of pre­Mesozoic drainage (Fig. 4).

Two other structural elements may be significant to basin interpretation: the Red Wing Creek structure and the New­porte structure (Fig. 2). Both of these structures are enig­matic. although the Red Wing Creek structure has been described as an astrobleme (Brennan et ai, 1975; Parson et al. 1975). The Newporte structure is interpreted to be a faulted block of early Paleozoic age in which oil has been trapped along unconformities within Cambrian and Ordovician sedimentary rocks; one well produced from Precambrian crystalline rocks (Clement and Mayhew, 1979). However, the structure may be of meteorite origin (Donofrio, 1981).

Indications of other tectonic elements or theoretical proj­ects of deformation have been published by several writers. Keams and Traut (1979) illustrated satellite imagery surface lineations which are northwest and northeast trending; al­though northwest-trending structures are known to be of significance in the basin, this is one of the few illustrations of the northeast trends that control much of the Mississippian

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structurally assisted stratigraphic oil traps in north-central North Dakota.

Several writers have attempted to establish a wrench· fault framework for the basin. Recently, Brown (1978) has used isopach variations in individual stratigraphic units to build a wrench-fault deformation fabric for the southern part of the basin. Earlier, Thomas (1974) built a regional theoretical model for wrench·fault tectonics in the Montana and North Dakota parts of the basin.

There is little question in our minds that sedimentation and structure of the basin are controlled by movement of base· ment blocks that were structurally defined in pre-Phanerozoic time. One of the earliest clear demonstrations of this is the work of Carlson (1960) showing Cambrian topographic relief on the Nesson anticline. Carroll (1979) illustrates the role of Precambrian topography in Red River porosity development.

The relative importance of wrench faulting, interprovince shearing, vertical-tensional defonnation, and continental boundary compression or tensional stress have not been evaluated for the tectonic framework of the basin. Studies of

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RIVER

FIG, 4-Pre-Mesozoic paleogeologic map of North Dakota. Modified from Carlson and Anderson (1966).

994 Williston Basin, North Dakota

depositional systems and mapping of structural changes through time are under way and should materially assist a tectonic interpretation of basin history.

STRATIGRAPHY

Sauk Sequence (Cambrian-Lower Ordovician)

Phanerozoic sedimentation was initiated in the Williston basin during latest Cambrian (Croix ian) time (Fig. 5), when the margin of the early craton was transgressed from the west by shallow marine water. In all probability. the entire basin sustained upper Sauk clastic sedimentation (Deadwood For­mation), The total thickness of Sauk sedimentary rocks in the basin probably does not exceed 1,000 ft (305 m). Isopach maps by Carlson (1960) and Lochman-Balk (1972) demon­strate that the prescnt basin was simply a large embayment on the western Cordilleran shelf and was not structurally well defined. Apparently, there was a northwest slope into the western Canadian miogeosyncline (Porter and Fuller, 1959).

Transgression occurred over a highly irregular surface on Precambrian crystalline rocks (Carlson, 1960) Present data indicate a hilly terrain with a few large topographic promi­nences, such as the Nesson anticline. Like most basal Sauk units, the Deadwood is largely clastic, including much re­worked, weathered Precambrian material. The middle of the Deadwood in western North Dakota contains appreciable limestone and limestone conglomerate, becoming more clastic as it thins eastward.

The only faunal studies of the Deadwood in North Dakota are studies (Carlson, 1960) of conodonts from the upper part of the Deadwood in the Nesson anticline area. The conodonts are probably of Early Ordovician age. Ross (957) also noted Early Ordovician fossils in cores from eastern Montana con­firming that the Deadwood is of Late Cambrian through Early Ordovician age where the thicker sections are preserved. A regional disconfonnity separates Winnipeg and Deadwood rocks.

Tippecanoe Sequence (Ordovician-Silurian)

A second cycle of transgression, sedimentation, and re­gression comprises the Middle Ordovician through Silurian rock record oflhe Williston basin. This cycle, the TIppecanoe sequence (Figs. 6, 7), marks the beginning of the Williston basin as a discrete structural depression with marine connec­tions to the southwest (Foster, 1972). Although the transgres­sive phase (Winnipeg Fonnation) is clastic, including a well-developed basal sand, the sequence is largely carbon­ate. Isopach studies of the sequence and its individual rock units suggest a southwesterly connection to the western geosyncline through the present central Rockies. Whether this is an artifact of late erosional events or not is unknown, Similarly, a marine connection existed across the Sioux arch to the eastern interior (Fuller, 1961, Fig. 21). Carroll (1979), in a study of tbe Red River Formation, clearly showed the influence of the Nesson anticline block, Billings anticline, the eastern North Dakota "highs," and several other struc-

LOWIIR QUlCIVICIAN

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FIG. 5-Stratigraphic column of Sauk sequence. Modified from Bluemle et al (1980).

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170 (50)

FIG. 6-Straligraphic column of Tippecanoe sequence. Modified from Bluemle et al (1980).

995 Lee C. Gerhard et al

tures. Isopachs of this fonnation are particularly important in studying basin evolution because they have been unaffected by later erosional events except aJong the basin margin.

Carbonate rocks ofthe Red River and Interlake Fonnations (Carroll, 1979; Roehl, 1967) were deposited under shallow marine and evaporite sabkha environments. Although the basin was well defined, there is little evidence of any particu­larly deep basal sedimentation. The Red River Formation contains shelf and lagoonal fabrics and biotas (Carroll, 1979), as well as sabkha evaporites and supratidal carbon­ales. Porosity development in the Red River is partly con­trolled by buried Precambrian hills or structures. D zone selective dolomitization of burrowed wackestones occur::; on the periphery of a buried "high" owing to density of dolomitlzing brines. Higher A, B, and C zone porosities are remnant after supratidal and/or sabkha dolomitization on the more crestal parts of highs (Table I, Fig. 8; Carroll, 1979; Carroll and Gerhard, 1979).

Sedimentation was continuous from the beginning of Red River deposition through the Silurian. Roehl (1967) carefully documented the analogy between Silurian Interlake Forma­tion fabrics, structures. and geometry and modem Bahamian tidal-flat features. Regression after Silurian deposition re­sulted in at least partial karst surface development.

Kaskaskia Sequence (Devonian-Mississippian)

Kaskaskia sequence rocks are perhaps the best known of the sequences because of their economic importance and because more subsurface data are available than for other groups. Thirteen studies of separate Kaskaskia rock units are either completed or in progress by North Dakota Geological Survey and University of North Dakota geologists

Limestones are the most characteristic lithology of the sequence. but two episodes of evaporite deposition inter­

,,le· ,D." ,~,­ ". TIPPECANOE ISOPACH

SASKATCHEWAN l, MANITOBAitT MOOIFIED FROM FOSTER AND GIBB,19721 _--­

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FIG. 7-Isopach map of TIppeeanoe sequence in Williston basin,

996 Williston Basin, North Dakota

FIG. 8-(a) Porosity zones in Red River Formation. A, B, and C zones have alternation of three lithologies: limestone, dolo­mite, and anhydrite in ascending order. D zone porosity is alternating limestone and dolomite. (b) Dolomitization model for A, B, and C zones by evaporation causing replacement of primary carbonate muds. (c) Dolomitization model D zone, showing brine percolating down dip through primary bur­rowed carbonate muds, but blocked by impervious organic carbonates from vertical movement. (d) Diagram showing how A, S, and C zone dolomite porosity occurs on top of buried structures. (e) Diagram showing D zone dolomite porosity occurring on flanks of buried structures. (0 Facies distribution during deposition of A, B, and C zones, showing supratidal dolomitization belt. (g) Facies distribution during deposition of D zone, showin~ pond and subtidal organic limestone deposited on top of lagoonal burrowed muds. All diagrams modified from Carroll (1979) and Carroll and Ger~

hard, (1979). (Figure continued on next page).

(b)

T2f RED RIVER

"AI.

SEQUENCE

"s"

SEQUENCE

"e"

SEQUENCE

"0 11

ZONE

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RED RIVER

EVAPORATION

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POROUS ZONE

POROUS ZONE

POROUS ZONE

ALTERNATING

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(c) ORGANIC

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997 Lee C. Gerhard et al

(e)

~

BURROWEO LIMESTONE

ORGANIC BURROWED

FIG. 8 (Conlinued).

rupled the carbonate deposition (Devonian Prairie and Mis­sissippian Charles: Fig. 9). Winnipegosis carbonates trans­gressed an eroded surface of earlier Paleozoic rocks, repre~

sented by red and gray shaly beds and carbonate breccias (Ashern). Winnipegosis sedimentation culminated in de­velopment of large stromatoporoid banks and pinnacle reefs before basin restriction increased salinity and induced Prairie evaporite deposition. Devonian seaways apparently opened northward, and isopachs of the basin indicate a northward tilt to structures (Fig. 10); the high point of the Nesson anticline shifts southward with the advent of Devonian sedimentation. The Dawson Bay and Souris River are not as well known as other units, but appear to mark an initial influx of clastics and supratidal carbonates over older deposits.

Water deepened again during the time of Dawson Bay deposition, Carbonate buildups rich in stromatoporoids ftourishedduring Duperow sedimentation (Hoganson, 1978). Birdbear (Nisku) rocks are marine carbonates with shallow­shelf faunas; farther north these rocks are reefal.

Red and green siltstones and shales cover Birdbear car­bonates, marking a hiatus in the middle of the Kaskaskia sequence. These clastics are in tum overlain by initial trans­gressive deposits of the upper Kaskaskia - the Bakken Shale (Upper Devonian to Lower Mississippian), a petroleum source rock and producer.

During the mid-Kaskaskia interval, a reorientation of sea· ways occurred, so that during Mississippian sedimentation

the Williston basin opened to the west through the Central Moncana trough (Bjorlie, 1979). Initial Mississippian Madi­son sedimentation (mid-Kaskaskia) was a mixture of near­shore lagoonal clastics and apparent crinoidal mudmounds (Waulsortian mounds) in central North Dakota and central Montana (Bjorlie, 1979).

Mississippian thicknesses, compared to Devonian in the basin, reflect the change of seaways, Activity in the Trans­continental arch may have been responsible for the Devonian northward tilt. The Mississippian seaway may be related to development of shear systems in central Montana, Crustal instability is suggested by angularity between successive rock units of Upper Devonian and Lower Mississippian age along the eastern basin margin.

Kinderhookian sedimentation in the Mid-Continent is characterized by oolitic shelf carbonates. The Lodgepole Fonnation in the Williston basin is no exception (Heck, 1978). Upper Lodgepole rocks are concentric facies with peripheral lagoonal beds and oolite banks, basinward pelletal grainstones, and basin flank and basinal organic muds,

Maximum transgression occurred near the end of Lodgepole or early in Mission Canyon deposition. Mission Canyon rocks are typically skeletal wackestones with shore­ward subaerial weathered fabrics and sabkha evaporites. Some marginal evaporites fanned coeval with the weathered fabrics and are important lateral seals for stratigraphic oil traps.

998 Williston Basin, North Dakota

The carbonate-evaporite rocks are regressive, with evapo­rites climbing westward in the section (Fig. 11). Subaerial weathering of the skeletal wackestones has produced a va­riety of pisolitic and fenestrate fabrics which tonn important oil reservoirs (Fig. 12; Gerhard et ai, 1978).

Evaporite deposition in the Charles Formation (salt) con­cluded Madison sedimentation. Sands, shales, and carbon­ates were deposited in alternating restricted and normal marine environments during Big Snowy deposition at the conclusion of the Kaskaskia sedimentary record. The extra basinal clastic sediments mark the influence of the Ancestral Rocky Mountain orogenic event west and south of the Williston basin.

Absaroka Sequence (Pennsylvanian-Triassic)

Regression during latest Mississippian time marked the end of the last major Paleozoic marine sedimentation phase. Orogenic events, including the Alleghenian, Ouachita, Ar­buckle, and Ancestral Rocky Mountain events, resulted in cratonic uplift in the northern plains and Rocky Mountain region. Absaroka sedimentation is characterized generally by interfingering of terrestrial clastic sediments with marginal marine and evaporite sediments (Fig. 13). Basal Absaroka rocks in the Williston basin are the Tyler Formation estuarine, bar, and marine sands and shales (Ziebarth, 1964; Grenda, 1978). Dense, microcrystalline carbonates and fine-grained red and brown clastics of the Amsden Fonnation suggest more restricted depositional conditions. Broom Creek rocks are more sandy and contain dense carbonates. suggesting prograding sands into a shallow marine b<isin. An uncon­formity at the top of the Broom Creek records a period of subaerial exposure and weathering during the Pennian. The remainder of Absaroka deposition includes hypersalinity in the center of the basin (Opeche Salt. Pine Salt) and fine­grained dominantly red to red-orange sediments deposited around the margins as well as across the rest of the b<isin.

Zuni Sequence (Jurassic-Tertiary)

Jurassic and Cretaceous sedimentary rocks in the Williston basin comprise a single large cycle of sedimentation (Fig. 14). Although an unconfonnity is present between the Ab­saroka and Zuni sequences, the lithologies on either side of the unconformity are similar. Evaporites (including salt), fine-grained red and brown clastics, and a few dense micro­crystalline carbonate beds comprise the lowest part of the Zuni cycle. These rocks are overlain by shallow marine

sedimentary rocks of the Rierdon and Swift Formations, which also contain glauconitic sands and oolitic carbonate bars.

The top of the Jurassic is marked by a subaerial regressive exposure surface. It was followed first by terrestrial deposi­tion of the lower lnyan Kara Formation, then by the marine transgressive phase of the upper Inyan Kara.

Progressive deepening of the Western Interior Cretaceous seaway provided for the deposition of the remainder of the Cretaceous marine section (Fig. 14). During deposition ofthe upper part of the Pierre Shale, increasing amounts of sand indicate regression of the Cretaceous sea strandline and the beginning of formation of the clastic wedge derived from erosion of the Laramide Rockies.

Further uplift, erosion, and volcanism in the Laramide Rockies provided extensive quantities of detritus to the Williston basin. In early Paleocene time, the last marine setting in North Dakota was the site of deposition of the Cannonball Formation. Later, Paleocene Fort Union sedi­ments covered and prograded over the Cannonball. Fluvial deltaic and paludal environments were characteristic of later Paleocene time during which extensive lignite deposits were formed. Cyclical in nature, these deposits are one part of the combined Powder River and Williston basin detrital aprons from the Rockies.

Younger Sedimentary Deposits (Terti31)'-Quaternary)

During the Tejas sequence (Tertiary-Quaternary), few in­durated stratigraphic units formed. Scattered limestone and shaly sandstones with volcanic ash form the tops of the Killdeer Mountains and have been correlated with White River (Oligocene) rocks of South Dakota (Fig. 15). Some indurated White River Formation is exposed in Bowman County, North Dakota, where a classical White River verte­brate fossil assemblage can be collected.

Pleistocene glacial sediments cover over three-quarters of North Dakota and a considerable part of the Montana portion of the Williston basin. They have been carefully mapped and studied for their ground-water potential by many writers. These glacial deposits are a major source of sand and gravel for the construction industry. Glacially derived soils support one of the most important agricultural economies of the country.

STRUCTURAL HISTORY

Until seismic and oil drilling exploration programs were initiated, the Williston basin was generally regarded as a

Thble 1. Characteristics of Dolomitization and Porosity Dpvelopment in Red River Formation*

A, B, and C Zones D Zone

Environmenl Sabkha SUbtidal and/or intertidal Fluid movement Evaporative pumping Seepage reflux ion Water Concentrated seawater with reduced ~alinity Mixed hypersaline and/or fresh water Dolomitization Subtidal. "at surface" Subsurface. interstitial

·Modificd from Carroll (I(P9).

999 Lee C. Gerhard et al

simple depressed saucer with two positive structures. the Cedar Creek and Nessan anticlines. This was obviously an oversimplified view based on limited data. The diagrammatic representation of current data and theory (Fig. 2) is also probably oversimplified. Before tracing the tectonic history of the basin by studying the two major anticlines, a brief survey of present structural elements and the depositional framework is necessary.

Phanerozoic sedimentation transgressed from the west across a weathered crystalline terrain, mostly of Churchill province rocks, but also across the Churchill-Superior boun­dary. Salt dissolution in the Prairie Fonnation in the north­central part of North Dakota appears to coincide closely with the approximate location of this boundary. This may suggest later movement along the juncture. No basin was present in the early part of the Paleozoic; only an indentation was present in the north part of the western cratonic shelf, al­though Precambrian blocks were protruding from the shelf floor (Carlson. 1960). Basin depression originated in the Ordovician (pre-TIppecanoe), with the main seaway connec­

tion apparently 10 the southwest (Fig. l6A). This early con­nection to the Cordilleran geosyncline was broken during the Devonian by uplift. Uplift tilted the Williston basin north­ward connecting it with the Elk Point basin sea (Fig. 16B).

Mississippian transgression coupled with subsidence of the Transcontinental arch system changed the seaway con­nection to the Cordilleran again. but due west through the Central Montana trough (Fig. l6C). This connection per­sisted during the Absaroka sequence, but with greatly re­duced circulation. Clastics spread into the basin from the south (Tyler), southeast. and northeast. Sioux arch sediments are hypothesized from the southeast. whereas drainage from the Canadian shelf has been demonstrated from the northeast (Fig. 16D).

Cedar Creek and Nesson Anticlines

Two major 'structures in the Williston basin, the Cedar Creek and Nesson anticlines, are oil productive and can be mapped from surface outcrops (although the Nesson is

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FIG. 9-Stratigrapbic section of Kaskaskia rocks. Modified from Bluemle e'al (1980).

I

-----

1000 Williston Basin, North Dakota

largely obscured by glacial cover). Because of the large amount of subsurface data available on these structures, their structural development can be documented (Figs. 17,18).

Nessan anticline history was initiated in the Precambrian. Lower Deadwood sediments were deposited around, but not over, the crystalline core of the present anticline. Upper Deadwood sediments are present where they onlap the top of the structure. Abrupt changes in thickness across the struc­ture indicate fault movement on the west flank of the Nessan. Renewed activity along the fault also affected Winnipeg deposition. Erosion between Deadwood and Winnipeg rocks formed the Sauk-TIppecanoe disconformity. Thinning of the post-Winnipeg·pre-Devonian section is due to renewed uplift without faulting.

Evidence of Ancestral Rocky Mountain orogenic move­ment in the Williston basin may be reflected by a second period of vertical fault movement which occurred in the

pre-Pennsylvanian, post-Mississippian Big Snowy interval. A mid-Permian event changed the stress regime. The former normal fault changes direction of motion, up on the west, rather than down on the west.

Laramide-related strain is evident during the Cretaceous, with a reversal of movement along the Nesson fault in the pre-Late Cretaceous. Since that time there is little evidence of major fault movement, although minor seismic activity con­tinues along the Nesson trend. Cretaceous rocks are folded across the structure and may also be faulted.

A comparison of structure in the basin, contoured on the top of the Silurian Interlake Formation (Fig. 18) and on the Cretaceous Mowry Formation (Fig. 19) shows asymmetry and steep dip on the west flank of the Nesson anticline as well as indications of the other major structures in the basin. Comparison with a map of structural elements (Fig. 2) shows that the Little Knife, Billings, and Antelope anticlines, and

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NORTH DAKOTA

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FIG. to-Isopach map of Kaskaskia sequence in WUliston basin, Modified in pari from Craig (1972) and Baars (1972),

1001 Lee C. Gerhard et al

the Bismarck·Williston trend can be seen in Silurian better than in Cretaceous rocks. There afe also suggestions of nonheast-trending anticlinal structures.

The asymmetry and steep dip on the west flank of the Nesson probably reflect Laramide fault movement on that structure. Northwest-trending structures in Cretaceous rocks underscore the importance of this relatively unexplored struc­tural trend.

The Cedar Creek anticline in eastern Montana has a some­what similar history (Fig. 20; J H. Clement, 1975·80, per· sonal commun.). No data are available to establish a pre­Winnipeg or pre-Red River history. However, two periods of early fault movement on the west-bounding fault zone oc­curred: (1) pre-Middle Devonian and (2) Late Devonian­pre-Mississippian. Faulting then reversed direction during Late Mississippian (Chester) through Triassic time. At this point, a minor subsidiary fault in the Gas City area developed locally (J. H. Clement, personal commun.). No major fault displacement has been documented affecting Jurassic, Cre­taceous, and Tertiary strata (J. H. Clement, personal commun.).

Red Wing Creek Structure

One of the most controversial and interesting structures in the Wilhston basin is the Red Wing Creek SlrUClure, which produces oil from a greatly ex.aggerated thickness of Missis­sippian rocks. At the time of its discovery in 1972, this structure was a seismic anomaly that fit no pattern for Williston basin structures. Exhibits presented to the North Dakota Industrial Commission during the spacing hearing for the Red Wing Creek field interpreted this structure as an astroblcme. Succeeding publkations by Brennen et al (975) and Parson et al (1975) presented additional data supponing this hypothesis.

It appears that sedimentation across the structure followed normal patterns for the \\'illiston basin through Triassic (Spearfish) time. In the Jurassic, a major structural disruption of a very small area occurred (Fig. 2J), which has been interpreted by previously cited writers as a meteorite impact. This event was apparently pre-Piper Formation. since red sandstones anti siltstones fill a ring depression on the Spearfish and below the Piper, although in samples it is

West East

KIBBEY FORMATION

+ + + + + + .. ~ + + + + ~+ + + + + + + + + + + + + + + + + .......... +++ ++~++ ... + .. + ... ++++++++++++++++ + + + + + + + + -~ + + + + + + ~ ~ ;: ...... + + ..- T + +I:'t' ~ + + -+ -+ T + + .. .. .. _ ... + .. + + .. + + 'V J:::a + + + -'-R'" + + + + + + + + + -'- ..... ~

: : : :: :::~ .... + r?f!-...~ ~ 1f'J..T.~~Y~~ ... : : : : : : : : ::: :: : : ~ _-~::: +

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~o 0;;;:' HHHH.H" .... H.H

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FIG. It-Generalized cross section of Mississippian rocks in Williston basin showing relationship of facies and stratigraphic nomen­dature, Modir..d from Carlson and Anderson (1%6),

1002 Williston Basin, North Dakota

difficult to distinguish true "crater fill" from Spearfish For­mation clastics. The discovery well (True Oil 22-27 Bur­lington Northern) cut a very thick pay section in disturbed Mississippian rocks. Much of the picture of the Red Wing Creek structure is apparently based on seismic infonnation as well as interpretation of complex well logs and samples. Renewed movement on bounding faults is seen as high in this section as the Dakota sandstone.

The central part of the structure is an elevated block, surrounded by a ring depression. The geometry of the struc­tuce is clearly cryptovolcanic and it is difficult to argue against a hypothesis of meteorite impact origin for this com­plex structure. Bridges (1978) suggested a section of several faults which change orientation through time (concentricline) as an alternate hypothesis. Others have suggested that this structure could also result from deep-seated igneous activity (diatreme). Detailed analysis of samples may detennine the validity of the meteorite impact hypothesis.

Newporte Structure

In north-central North Dakota, the Shell 27X-9 Larson discovered oil in Deadwood Sandstone (Fig. 22; Clement and Mayhew, 1979). Continued development of this field demon­strated the complexities of the Williston basin as well as one of the rare oil wells producing from Precambrian crystalline rocks (Shell 14-34 Mott). Interpretative cross sections (Fig. 23) suggest that Deadwood Sandstone was deposited be­tween Precambrian hills in part, and that pre· Winnipeg (post-Sauk. pre-TIppecanoe interval) erosion and faulting created a small basin of detritus from Deadwood and Pre­cambrian rocks. Winnipeg sedimentation covered the struc­ture, but was in part cut by at least one growth fault.

An alternate hypothesis, presented by Donofrio (1981), suggests that the Newporte structure is possibly a meteorite impact feature.

ORIGIN OF WILLISTON BASIN

Since Middle Ordovician time, the Williston basin has subsided approximately 16,000 ft (4,875 m) without under­going severe orogenic deformation or severe peripheral tec­tonic distortion. Recent mapping of heat gradients in North Dakota (Harris et a!, 1981) suggests no abnormally high heat flow that would indicate any "mantle plume" or "hot spot" beneath the basin to account for its subsidence. Several papers have advanced wrench-fault systems to account for the generation of known structural elements in Montana and North Dakota, but none have championed a specific origin for the Williston basin.

The change in structural grain between the central and northern Rockies takes place at the approximate location of the Fromberg fault zone at the north end of the Big Hom uplift. This fault zone, of unknown age, trends parallel with the Colorado-Wyoming shear zone. Casual observation demonstrates a northeastward linearity of the Fromberg zone with portions of the Yellowstone River course, the north end of the Cedar Creek anticline, the Watford deep of the Williston basin, and a saddle in the Nesson anticline (Fig. 24). To the southwest, west of the Beartooth uplift, the same linearity defines the Snake River plain.

We hypothesize that both the Fromberg and the Colorado-Wyoming shear zones were formed by left-lateral shearing in the edge of the pre- Phanerozoic continental plate. This shearing displaced the present northern and southern Rocky Mountain blocks, catching the present central Rocky Mountain block (with the Black Hills and Big Horn uplifts therein) as a slice between the shears, resulting in left-lateral drag.

Initial shearing resulted in the formation of numerous basement-rooted faults within the central Rockies, Black Hills, and Williston basin. Since that time, it is questionable if any significant motion has occurred along the two major shear zones. However, evers orogenic episode with major influence on the North American plate would apply stress to the system and many of the associated faults show some Laramide displacement. We theorize that the shear system

A EPISOOE II :POROSITY DEVELDPMENT;

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SHALLDW MARINE

EPISODE Ill:

VADOSE PlSOLlTE (Caliche)

DOLOMITIZATION I ANHYDRITE ...J

FIG. 12-A. Generalized sections of map showing porosity development in Frobisher-Alida zone, Glenburn field, North Dakota. Episode II illustrates porosity development by fresh­water weathering and desiccation. Episode III indicates rela­tive position of several strandlines and depositional or diagenetic lithologies. Episode IV demonstrates formation of porosity through generation of vadose pisolite or caliche. B. Loferite shrinkage or desiccation voids overlain by subaerial laminated crust, in turn overlain by pisolitic lolerites. Thxota 1 Weber at 4,600 ft (1,406 m). Scale on photo is 3 em long,

(Figure B on next page).

1003 Lee C. Gerhard et al

and its dragged blocks have been repeatedly "tensed," with resultant vertical motion along basement planes of structural dis<:ontinuity This does. not preclude motion along the majur shears (e.g., Laramide displacement on the north end of the Big Horns along the Fromberg zone), but does not require it.

If this hypothesis is correct, the following conclusions can be drawn.

I. The central Rocky Mountains were a depressed block during Ordovician-Silurian (Tippecanoe) time, as demon­strated hy the marine connection between the Williston basin and the Cordilleran sea during Tippecanoe sedimentation (Fig. 16A). The northwest extension of this depression is a "graben-like" or depressed Williston basin block. The geometry of the shears and block mighI lead to an aulacogen

B

(Continued).

interpretation (Fig. 25), but we do not espouse that idea. An alternate idea is one of a large-scale "puB-apart basin" simi­lar to that proposed by Burchfiel and Stewart (966) for Death Valley, California (Fig. 25). However, the origin of the Williston basin as a structurally and asymmetrically de­pressed block formed at the Tippecanoe-Sauk sequence boundary as a northeast extension of the central Rocky Mountain block is attractive to us. This would be a com­plimentary distortion to the eastern North American Taconic orogenesis.

2. The Devonian movement of the Transcontinental arch, which we have previously suggested is responsible fur the opening of the Williston basin into the Elk Point basm on the north (Fig. 16B). would be geometrically controlled by the

PISOLITIC LOFERITES

- CRUST

>VOIDS

- - ----------- - --

1004 Williston Basin, North Dakota

presence of the Colorado- Wyoming shear zone. The source of the tectonic stress could be both eastern (Acadian) and perhaps western (Antler) deformation.

3. The geometries of central Rocky Mountain structures in Wyoming, the Black Hills, and the Williston basin all fit a left-lateral strain model in both general morphology and angular relations (Fig. 24).

4. The Mondak Mississippian field of the Williston basin is a very large (at least 100 million bbl) oil field, producing from fractured Mission Canyon Formation carbonates, without significant structural closure. The field and its "look alikes" lie on the homoclinal east-dipping flank of the Cedar Creek anticline. Although various schemes to explain this oil field have been advanced, such as underlying salt solution (Keams and Traut, 1979), none has been satisfactory. Application of the "tensing" theory advanced here might be a more satisfac­tory explanation for the reservoir fracturing here and in other fields.

Well-indurated Mississippian carbonates are bounded below by Bakken shales and silts, and above by evaporite, both structurally incompetent lithologies. Tensing of these rocks would produce no apparent distortion of the incompe­tent beds, but the competent carbonates would develop closely spaced jointing (fractures). This hypothesis could also account for fractures reported from the Little Knife Madison field, as well as others by analogy.

As basin studies advance, new structures, evidence of greater amounts of fault displacement, and suggestions of long histories of structural distortion of major structures are being documented. All of the newest structural data available to the writers appear to complement our hypothesis.

No major relationship between our model for the origin of the Central Rockies, Black Hills, and Williston basin and the development of the Wyoming-Montana overthrust belt is apparent. Certainly, deformation of that tectonic province exerted stress on our area of interest. There is considerable evidence of Laramide and post-Laramide defonnation in the Williston basin. In our opinion, however, the Laramide de­formation created the stress that once again "tensed" the Wyoming block and provided for the vertical uplift of many Laramide structures now present. The structural grain of these structures is still inherited from the Proterozoic left­lateral shear system we have hypothesized.

OIL AND GAS RESOURCES

Oil was discovered in the Williston basin in Montana on the Cedar Creek anticline (1936), in Manitoba (1950), and in North Dakota on the Nesson anticline (1951). More recently, several significant cycles ofexploration have been completed in North Dakota and another is in progress (Gerhard and Anderson, 1979, 1981). Annual production increased until 1966, then declined until 1974. It is now on an uptrend which, in 197,9, surpassed the previous high (Fig. 26).

Although the initial discovery was from Silurian rocks, the early development of the Nesson anticline was primarily from Madison reservoirs. The peak discovery period was 1952-53. Development along this 75-mi (120 km) trend was nearly complete by 1960, with producing capacity exceeding the available market. Production was limited then by prora­tioning until November of 1965 when natural decline of these reservoirs equaled the market demand. The only significant deeper zones developed along the Nesson trend during that time were the Duperow and Interlake pools in Beaver Lodge and Antelope fields and the Sanish pool in Antelope.

Widespread wildcatting around the state in 1954 had a notable lack of success except for small discoveries in Bot­tineau County. The Jack of success slowed exploration until 1957-58 when the Burke-Bottineau stratigraphic trap play met with success. The increasing production during 1958-61 (Fig. 26) largely reflects development of these pools. Produc­tion from this area was marketed first by rail and then. in 1963, via the Portal Pipeline to refineries in Minnesota and Wisconsin. The slight increase in wildcats in 1964 reflects the expanded market provided by the pipeline (Fig. 27).

In 1960. discovery of the Cedar Creek pool extended Red River production along the Cedar Creek anticline into North Dakota. The Bowman County Red River play extended pro­duction in this area to small "highs" along the eastern flank of the structure in (he period from 1967 to the mid-1970s.

Tyler sand reservoirs which were discovered at Rocky Ridge in 1957 and Fryburg in 1959 became important de­velopments in the mid-1960s in the Stark and Billings County areas. Peak production in 1966 at the Medora field and in 1967 at Dickinson field helped offset declines in the older producing areas.

The decline in production from 1966 to 1974 represents the

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FIG. 13-Stratigraphic section of Absaroka sequence rocks.

1005 Lee C. Gerhard at al

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FIG.l4-Stratigraphic section of Zuni sequence rocks.

1006 Williston Basin, North Dakota

failure of new discoveries to replace the natural decline of the major producing areas. The normal pattern is discovery, followed by development leading to peak production (l to 3 years) and then gradual decline. Secondary recovery methods usually alter this pattern. Water injection for pres­sure maintenance was installed in many of the Madison reservoirs along the Nessan trend, but was relatively unsuc­cessful. Similar programs in the Newburg-Spearfish, Madi­son reservoir in 1967 and in the Tyler sandstone reservoirs of Dickinson field in 1973 and Medora field in 1970 increased production levels above the initial development peaks in those fields. However, these successful programs could not offset the natural decline of the major producing areas.

The trend of lower exploratory acti vity of the 1960s gener­ally followed the national trend. The upsurge of wildcatting in 1968 has been referred to as the "Muddy sand" play. It followed development of the Bell Creek field in Montana, but no similar occurrences were found in North Dakota and exploration activity again decreased.

However, two events, occurring close together, signifi­cantly changed Williston basin production history. The Red Wing Creek field was discovered in McKenzie County, North Dakota, and OPEC placed production controls (embargoes) and price increases on production by member nations.

The Red Wing Creek discovery excited basin oil operators because of the relatively high productivity of the wells and because of the anomalously thick pay section. Because no one really understood the nature of the Red Wing Creek structure at the time, industry's only possible response was to gain leaseholds in the area. The leasing activity set off by the Red Wing Creek discovery set the stage for further develop­ment. The now common 5-year-term leases of western North Dakota tended to increase exploratory activity as compared to IO-year leases. The lease play, coupled with the sudden availability of venture capital, caused exploratory drilling to begin to increase in 1975 and 1976, partly in response to the lease expiration dates.

OPEC made the first substantial increase in oil prices, so exploration could be a profitable venture. Prior to the in­crease, many companies found that exploration risk money had a better return in a regular bank savings account than in

H I I,ooceneI ;; I ~ I a: ~ I ~ I PleIstocene

o I I ~

~

I Plio",...I

~ '1-----1 ~ I ...-... locrne Ill: I ~ I .

0li«ocrne

nAHt:

actual wildcat drilling. The price increases created risk capi· tal, and thus exploratory drilling was enhanced.

It is interesting to note that exploration and production have followed technology. Initial production was from Nes­son anticline seismic prospects. Amerada Petroleum Corp. drilled a string of successes 75 mi (120 km) long without a dry hole. As interpretation of basin geometry progressed, !>tratigraphic/structural traps were defined along the northeast basin flank. Later, in Bowman County, North Dakota, seis­mic surveys successfully defined small Red River structural "highs." Stratigraphic plays and long-shot deeper drilling sporadically generated interest until the well-known unusual seismic configuration at Red Wing Creek became productive.

Assessment of future production involves an evaluation of source rocks as well as reservoir capi1bilities. Geochemical studies have classified Williston basin oils into three types. Based on carbonate isotope studies it hi1s been postulated that the source rocks for most of the oil are the Winnipeg shale for type I, the Bakken Formation for type II, and the Tyler shale for type III (Williams, 1974). Dow (1974, Fig. 2, p. 1258) further estimated reserve volumes as: type I, 600 million bbl: type II, 10 billion bbl; and type III, 300 million bbl. He estimated that 50% of type I, 30% of type II, and lesser quantities of type III oil had been discovered at that time.

The writers, and others who have studied the rock sections in the basin, would agree that the Winnipeg, Bakken, and Tyler represent the most concentrated source of organic mate­rials; however, we believe that many producing zones con­tain sufficient organic material to have been the source them­selves. Specifically, the Red River, Birdbear, Duperow, Win­nipegosis, and Madison have sufficient indigenous organic material to provide large quantities of liquid hydrocarbons. If so, there is much more oil to be found in the Williston basin.

If new pool discoveries are compared to preceding curves, the significance of the present development boom becomes obvious (Fig. 28). High levels of wildcat activity have had a corresponding peak of new pool discoveries. except during the 1954 east side and 1968 "Muddy" Sandstone wildcat programs. The number of new pool discoveries per wildcat drilled has risen dramatically in the last 4 years. This increase in success is attributed to (1) the use ofCDP seismic methods,

,'" .. -'-:-.,w.....·- . G••v•.~~.: ';" •. ' 0:' \ /.~.~.-,

~"MEu r<JRM"TI<J~S •.~~~. ~ ':.:~ WEST CENTR"L ["ST 111',0 RIVER V"LLE! ~~,,:::I

~~ir:i~IVER (;.ovoJ .':." ~ _.~ ::).:;>..~ COI.EHARBOR FALCONER ~~,~r;1'I" 'II."', of ,~•• ;.'~ .".

WYL]}' St<:>n•.. '.. '

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ll'lwn..ou. ",.m.d ... d u",nam.d unol.,

,(I,nnam ..d I ",II

(llnnamed Iln,l)

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., .~ '0....,; to ~

/ Guv.1

...... c" ,

~~.~ . ....c '~"?'~~_7:::-''''''' -'­"':-"_.--~

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FIG. IS-Stratigraphic section of Tejas sequence rocks and sediments.

SO(IS)

1000(300)

300(90)

400(120)

lS<l(4S l

1007 Lee C. Gerhard et al

(2) better reservoir geology, and (3) completely revised test­ province. During L970 there was an average of 20 active ing and completion techniques. drilling locations in the entire United States portion, whereas

Dramatic expansion of producing areas has occurred dur­ during 1980 there was an average of ]50 active drilling ing the present cycle, including new producing counties, new locations. pay zones, and new producing depths. The maps of North Current activity is centered in we~tem North Dakota and Dakota producing fields in 1970 (Fig. 29) and 1980 (Fig. 30) the bordering Montana counties. Significant new discoveries illustrate the resurgence of the Williston basin as a major oil have been the Little Knife Madison in 1977 (109 wells, 125

r-~.I'-'00 lQlIII,l[$ ,,

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ROCK TYPES

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~ limUfon.

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,

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I

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~ Dolomite

f=;,:..:-.:::,:,] 50ndy Siltstone

t:.;:~:i;~l Sandstone

o

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, ! i " tOo 2Cll ~oo KILOMETEl'IS

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FIG. 16-SequentiaJ maps showing marine communication directions during times indicated for Williston basin. A. Tippecanoe sequence, showing connection with Cordilleran miogeosyncline on southwest and eastern interior on southeast across Transcontinen­ta. arch. Modified from Foster O(72). B. Lower Kaskaskia sequence communication to Elk Point basin in Canada. Modified from Clark and Stern (968). C. Upper Kaskaskia. showing communication of Cordilleran miogeosyncline through Montana trough. Dark spots at entrance and along edges of Montana trough represent bank development. Some bank development is also h)'pothesized within basin. Modified from Bjorlie and Anderson (1978). D. Absaroka sequence, showing flood of clastics from southwesl as well as from drainages to 11Ortheas1 and east. Sediment flow probably occurred from farther southeast also. Modified from Mallory (1972a, b) and Rascoe and Baars (1972),

1008 Williston Basin, North Dakota

million bbl reserve), the Mondak Madison in 1977 (112 wells, > 100 million bbl reserve), and the Billings Nose area where there are Madison reservoirs and Duperow wells that have recorded initial potentials over 2,000 bbl/day and a few with potentials over 3,000 bbl/day (158 wells, 100 million bbl reserve).

Another significant recent development is exploration of deeper zones along the Nessan trend.

Shallow gas plays are in their infancy in the basin. but are in process. Air drilling is necessary for adequate testing of Pierre (Judith River and Eagle sands), "Muddy," Inyan Kara, and Niobrara rocks, but these rigs are uncommon in the basin, and surface holes can be a problem with air drilling. Little testing has been done on the southeast extension of the Antelope anticline, an area that industry has only recently begun to delineate as a major potential hydrocarbon area. Stratigraphic traps around the Cedar Creek, Nesson, and Poplar anticlines are mostly untested, as is much of the eastern and western basin flanks.

The northwest shelf, west of the Nessan anticline, holds promise and has been tested mostly on the Montana side of the basin. Many prospects remain to be drilled.

In 1970, the total bonuses paid for the year for state leases

was $294,000. In 1978, the annual total was near $20,000,000. In 1980, for the last quarter sale only, over $30,000,000 was paid.

The future for oil and gas production in the Williston basin looks bright for the next few years. New rigs moving in, major exploratory programs under way, and high lease prices all support a continuation of the present exploratory boom, with several years of developmental drilling needed after exploratory drilling decreases.

Financial impacts on the state of North Dakota from the oil business are very significant. For the 1980s, oil~ and gas­generated revenues will be the most significant single source of income lO the state government.

OTHER MINERAL AND ENERGY RESOURCES

The Williston basin contains two major resources besides hydrocarbons, although present production of either does not begin to compare with the value of the hydrocarbon resource. Lignite is actively mined and is a significant energy and revenue producer in North Dakota. Potash resources are not yet being mined, but serve as a damper on potash prices in the world market. especially on Canadian resources.

NESSON ANTICUNE

PRE - MIOOLE MISSISSIPPIAN

MID·P(RMIAN

W MINNEKAliTA. BASE SPEARFISH

i:;:::::~::::~:~:~~~~~~~I~~n~~~~~~~~~JI~~~~~~~~i~ii;~?~[~I~~~~~~~~ 'I:I~"'~

ItI

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w 8ASE TYLER E

>OOd

)'~)~~)~~j)~~~~j,~~jj~~Ij-IOjIII~)'~~~j~~~jIr~'jljl~~~lj~~lll~~-i-~ttI]~~U

PRE -UPPER CRETACEOUS W TOP MOWlrY E

"::: :::_:_::_=:::::=:::::_:::::.::_::_~; .::{_::::::::::::::::::?=:=:=;=::_:::-:_::=:::-::-=~:~:-:K:~! ::::_:_:::::::::::1 0

E

!!.-~--~~ii~----:~;!:-:~-~:--~::~:~-::~!~:_~:_·~~i;~: 1000 - 200'"

,m I

FIG. 17-Diagrammatic cross sections of Nesson anticline showing structural development. Note apparent reversal of fault move­ment during mid-Permian. Some of pre-Upper Cretaceous movement may be related to salt solution.

1009 Lee C. Gerhard et al

Deposition of Prairie Fonnation evaporites, after restric­tion of circulation in the Elk Point basin of Devonian time, created a very large resource of salt and potash in the Williston basin (Figs. 9, 16, 31, 32). Within the Prairie salt section of North Dakota and Montana. three potash units occur: the Esterhazy, Belle Plaine, and Mountrail Members (Anderson and Swinehart, 1979). At the present time, potash is being mined by both conventional underground and solu­tion methods in southern Canada. Approximately 50 billion tons (45 billion Mg) of potash lie south of the international border in North Dakota, with additional resources in Montana.

During the mid-1970s increasing world market prices coupled with both export taxes on Canadian potash and action by Canadian government to take control of the Cana· dian potash mines created a flurry of leasing and pre-mining activity in North Dakota and Montana. Since the depth to minable potash in the United States portion of the basin precludes conventional mining techniques, solution mining was planned for North Dakota. A price stabilization occurred with renewed exploration and plans for development in 1976. As production from the New Mexico deposits wanes, the Williston basin deposits will serve to prevent any world potash cartel from major price increases. Our 50 billion tons (45 billion Mg) of resources insure the domestic supply of this critical mineral.

Lignite is a major energy resource in the North Dakota part

SILURIAN STRUCTURE MAP

of the basin (Fig. 33). Lignite occurs as part of the Cenozoic rock suite derived from erosion of the Laramide Rocky Mountains. These rocks, generally called the Fort Union Group, are mostly of terrestrial origin, although the Cannon­ball Formation, in the lower part of the Fort Union, is the youngest marine stratigraphic unit in this area (Fig. 34). Mining is now exclusively by surface techniques, but earlier in the history of North Dakota underground workings were common (now a source of major environmental concern as they collapse).

Because this lignite has low-sulfur but high-water content. most of it is utilized close to the mining site for electrical generation (Fig. 35). Despite the national need for additional energy resources, severe restriction on leasing of reserved federal coal and stiff reclamation policies have held down production increases. StiH, production in North Dakota has doubled in the last 5 years as new electrical generation plants have gone on stream (Fig. 36). The 20 billion ton (i8 billion Mg) reserves and 350 billion ton (318 billion Mg) resources specify that the lignites will be major energy sources for decades.

SUMMARY

Geological analysis of the Williston basin has benefited from expansion of the subsurface data base by renewed oil exploration, application of computer techniques to dat~ han­

o to 20 30 40 50 MILES I I" I "I' , o C203040~ KILOMETERS

FIG. 18-Structure map of top of Silurian Interlake Formation showing geometry of Williston basin in North Dakota. 1. Billings anticline; 2, Little Knife IDticline; 3, Bismarck-Williston trendj 4, Nesson anticline; 5, Antelope anticline.

1010 Williston Basin, North Dakota

~

00

'"

o 10 20 10 40 50 MILESI ' , , , , , ii' i

o () 20 ~<4050 KILOMETERS

FIG. 19-5tructure map of top of Mowry Formation (Cretaceous). Compare Figure 18. Closely spaced contours on west side of Nes­son anticline suggest post-Mowry faulting on that structure. Bismarck-Williston trend also appears to be well developed as is Billings anticline. I.ittJe Knife anticline does not appear to be so well defined at this horizon.

CEDAR CREEK ANTICLINE

POST-SILURIAN PRE-MIDDLE DEVONIAN LATE MISSISSIPPIAN EARLY PENNSYLVANiAN w

LATE DEVONIAN PRE-MISSISSIPPIAN NNS,(~"A"'Ill,N TOP AMSD!:N

• E _8~(, SNOwY _ a eAsE MISS:SS,PPIAN

~ MADISON 1000'

t DEY NIANm~1:fffi!fe;g;sm~~'~~i#if~QOO ~ '- J ~ cS ~~U~'¢N:-' ' ."

I' INNI EG-":. _ _ _ 3000'2000

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TOP MINNEO<AHTA [' - - ~ PE.RMI,lN

- - __ T~~~~~\\J:E~~M~A~ ~ ,1000'BIG SN(jINY 1000

_ BIG SNOW'

I ;::=,.-"'J t~M"'"" ~ EVON'A~y ~ ~ M:lDI50N~EVONIA:-.I A 3000'

~DEVO,"'IMj·~ DEVDNI:lN ....• 2000'~~II;lililiilii~~~;i!-~lBI'i';C";"I<'I'I'I'CJ 7" I T~ I 0

\','IN~"PcG " j / J I J , :< J :< 1'.

I WINNIP~G1

Contour Int.rva I 200 f.et

STRUCTURE MAP

o I MILE

FIG. 20-Diagrammatic cross SC(:tions across Cedar Cref:k anticline at Gas City field. Modified from Clement (1976). Minor second fault generated locally in Gas City area during Late Mississippian-Early Pennsylvanian episode was concurrent with minor reversal of movement on principal west fauU zone.

1011 Lee C. Gerhard et al

dling, and detailed environmental and diagenetic analysis of cores and cuttings. The study of these new data indicates a much more structurally complex basin than heretofore was realized.

Basin evolution in Phanerozoic time begins with Sauk (Late Cambrian) transgression across a rough Precambrian topographic surface. but without definition of the basin. Tippecanoe sequence rocks show the initial depression of the Williston basin with seaway connections west and southwest to the Cordjlleran rniogeosync1ine and a probable connection to the Mid-Continem as well.

During the Kaskaskia sequence, movement along the Transcontinental arch tfend tilted the Williston basin north­ward, creating a marine connection on the north into the Elk Point basin dur1ng the Devonian, while shutting off the earlier Cordilleran and Mid-Continent marine connection of the TIppecanoe sequence. During the later part of the Kas­kaskia sequence (Mississippian), the nOithem connection was cut off and the Williston basin reconnected to the Cordi­lleran sea through the Central Montana trough.

Pennsylvanian structural disturbance in the southern Rock­ies (Ancestral Rocky Mountains) disrupted sedimentation patterns of primarily carbonate-dominant lithologies in the basin. Beginning with the Absaroka sequence, clastic sedimentary facies predominate in the Williston basin with interspersed evaporites and a few carbonates.

A full marine setting was established during the Creta­ceous as part of the Western Interior seaway. Regression

TRUE OIL

accompanying uplift of the Laramide Rockies provided paludal and fluvial environments that trapped much sediment moving eastward from the Rockies in Paleocene time and assisted in the formation uf t:x.tensive lignite deposits.

The basin appears to be the result of drag along two left-lateral shear system.s. These shear systems formed a depressed block which now encompasses the central Rocky Mountains and southern Williston basin. Tensing of this block during plate-wide orogenic stress created the vertical structure seen today.

Substantial quantities of lignite, potash, and petroleum are present in the Williston basin. Lignite mining for electrical generation is a major industry, but potash resources are not yet being mined.

Oil and gas produdioll is rapidly expanding in the basin, as several new structural trends have been mapped in recent years. A very high success rate in exploration drilling has doubled oil production in the last 4 years. Continued in­creases in oil production are forecast for the next few years. Several of the structural trends now heing mapped have not been substantially explored, and shallow gas potentials have been largely ignored.

REFERENCES CITED

Anderson, S. B., 1974. Pre-Mesozoic paleogeographic map of Nonh Dakota: North Dakota Geol. Survey Mise. Map 17.

--- and R. P. Swinehart, 1979, Potash salts in the Williston basin.

-~ooo

·4000

-!>ooo

'6000

-moo

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M,. 2 2 • 27 8yrtill9loll ftarttlen. (SE NW SIIetlOll 271

TO 13,710 Rllld Riy,~A <> • ••• -Q­ .' ~RIM--+--RIN6 DEPR£SSION II CENTRAL UPLIFT I RINt; OEPR£SSION-,+RIM_

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. ::==SPEARF'ISH

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_'L.ASlCA IENCHI __ TYLER-HEATH

OTTER

I!' = "'BEY I CHARLES

I , ' . =MIDALE',..I ~:i:iiL MISSION CANYON I ,~.~,~.~.

LODGEPOLE

FIG. 21-Cross section through Red Wing Creek struclure. McKenzie County, North Dakota, demonstrating meteorite-impad hypothesis for origin of this structure. True Oil 22-27 Burlington Northern discovery well was drilled on top of central uplift. Modi­fied from Exhibit 6, case 1152, North Dakota Industrial Commission, submitted by Union Oil Co. of California.

1012

R 81 W GAM"A

.AY SONIC T,.4 N

..0 RIVER

T 163 WINNIP£G N

PRECAMBRIAN

j KllOM£TER

TO 9490

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Williston Basin, North Dakota

A SHELL

LARSON 2~X-9

SEC 9 T11l'N RaN lPf ]1 BOPO

10... .."

GAR'1~

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WINNIPEG

DEADWOOD

-<

i FlWD (80"11, ~2)

REC 5 8GCO a .,

TD '736

B c STRUCTURE SHELL

TOP WINNIPEG MOTT 14-34 SEC ]4 TlIIN A1I7.

FIG. 22-Newporte field structure map and lithologic sections. A. Shell Lanon 23 X~9. sbowing producing interval in Deadwood Formation. B. Structure of top of Winnipeg Formation in Newporte field. C. Shell Mott 14..34, showing produdng toten-als in Pre­cambrian Bnd at Winnipeg Precambrian cootset. Modified from Clement and Mayhew (1979).

~~

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"--­ ""

\ 0° r ( " ~-"oo \ \ I., j) -­ ~....

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1013

-7000

Lee C. Gerhard el al

CONCE PTUA L CROSS SECTIONS

NEWPORTE FIE LO

A A'• .'SHELL $I'I[LL SHELL SHELL SHELL MaTT 14·30( MOTT 32X-3 W'SOAHl. 23-10 LA.flSON 2SX-9 MOTT 14·S.

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~~'i;;.j-~:~~ -/~~1'~':0~~:-:~_~~,;~:Tti~~ '.l,,''t,-''L,'t''''r T.L~,·,:Jrr:-__·~j R£D:-t-," '~I· .

..' ,;;.', ~~j:;-:~(-; :,r. >I ,'/ T'''l' ,r~ -~: ,~.;'VER,~ .\l~-, _... r~~: ~:~" , l.' J I. ,t ': r', 'r, 1"

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~~~;;t,LJ

v , MILE, ,-_-;::======:::;-_~IM'L[

1.,LOllEn" , "'LOlllET£~

FIG. 23--Cross seetions across Newporte field. See Figure 22 for lines of section. Modified from Clement and Mayhew (1979).

__ J\ \-.......,...--.. /J_m-r;;(.',~:;

'1,

''?", ,"";?I ~ tl""

'-'·11"" .. /,

/ //'1, 1,'1."~·' \//";\ TY

) /': I

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>

lo'::: o#ft '

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---'-"- \- . ­__ ,

u 100 200 300 K,\O....lt'. __ ~ ~1OO.1I."".'", , /

FIG. 24-Diagram showing relationship of Fromberg-Colorado-Wyoming shear zones to structural features of Rocky Mountains and Williston basin.

-1

1014 Williston Basin, North Dakota

stratigraphic column: North Dakota Oeol. Survey.

Baars. D. L., 1972, Devonian System, III Geologic alias of the Rocky U.S.A.: Nonh Dakota Geo!. Survey Rept. lnv. 68, \9 p.

Brennan. R. L.. B. L. Peterson. and H. 1. Smith. 1975, The origin of Red

Mountain regIOn, U.S.A.: Rocky Mountain Assoc. Geologists, p. Wing Creek structure: McKenzie County, North Dakota: Wyoming 90-100 Oeo!. Assoc. Earth Sci. Bull., v. 8.41 p.

Ballard, F V. 1963, Structural and stratigraphic relationships in the upper Bridges, L. W. D .• 1978. Red Wing Creek field, North Dakota; a concen­Paleozoic rocks of eastern Nonh Dakota: Nonh Dakota Geo!. Survey triciine of structural origin. in The economic geology of the Williston Bull. 40, 42 P basin: Williston Basin SYOlpo~ium. Montana Oeol. Soc., p. 315-326.

BJorlic, P. E. 1979. The Carrington Shale facies (Mississippian) and its Brown. D. L., 1978. Wrench-style deformational patterns associated with relationship to the Scallion subinterval in central Nonh Dakota: North a meriodional Slres.~ aXIs recognized in Paleozoic rocks in parts of DakOla Geol. Survey Rept. rnv. 67,46 P Montana. South Dakota, and Wyoming, in The economic geology of

~--and S. B. Anderson, 1978, Stratigraphy and depositional setting of the Williston basin: Williston Basin Symposium. Montana Oeol. Soc., the Carrington Shale facies (Mississippian) of the Williston basin. in p. 17-35 The economic geology of the Williston basin: Williston Basin Sym­ BurchfieJ. B. C. and J. H. Stewart, 1966. "Pull-apart" origin of the posium, MontanaOeol. Soc., p. 165-177. central segment of Death Valley, California: Oeo!. Soc. America

Bluemlc. J. P., S. B. Anderson, and C. O. Carlson, 1980, North Dakota Bull., v. 77, p. 439-442 .

A .. -:}~.._..._... _....- ... ::::: "" Belt At. '",.. ..:.:....:. "\,Super:group ""'l:~ y'" Pt. of Williston Bosin "::, ........ ~T~ )0­

.:.:....::. )-..L'" ..? ..L?.... ,J.,).::·.Y ,

::-.t:. Central Montano Embayment

.j:~·!:k~ " .•::':':';':'f.::.•':'.i. .a."" Uinta Mountain Group

//j2@;ifj;'~:~~:uar Group PuhrumP':~:::·.::::'::''''' to'"

GrouP,:.-f.::·:.:.::;:: .. ." ::••:.:.....::......:.:: .( T "" of ApaChe Group

TREND OF UPPER PRECAMBRIAN AND LOWER CAMBRIAN ROCKS

o lQO 3QO MILES ....~/;!>:. { EZJ Ii. , o 100 100 KILOM£T£ ItS

CENTRAL ROCKY MOUNTAINS

k:::::;:J AREA OF TE NS ION B

N

FIG. 25-A. Aulacogen origin for ,",,'illiston basin. Basin is shown as possible extension of Central Montana embayment dUring Pre­cambrian time. Modified from Stewart (1972). B. Pull-apart origin for Williston basin. Basin was placed under tension due to move­ment along major shear zones causing grabenlike downdropped blocks. Modified from Burchfiel and Stewart (1%6).

1015 Lee C. Gerhard et al

50.000

40.000 Ul ...J W a: a: « tD

30,000

o o Q

20.000

10,000

40,338

INESSON-MADISON I J l RED WING OPECMADiSON STRATIGRAPHIC CREEK

BOTTINEAU-BURl<E COUNTIES

ORIGINAL DISCOVERY

23,273

I LITTLE KNIFE,

MONOAK

N ~ • ~ ~ ~ ~ ~ 0 _ N ~ .. ~ ~ ~ CDO\O-N"". "'~""Q)cno ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ w ~ ~ w ~ ~ cQ w ~ ................ .... t-- .... .... .... CD ~ ~ ~

YEARS

FIG. 26-Annual oil production in North Dakota, 1951·80 (in 1,000 bbl). See text for discussion of events on graph.

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YE.4RS

nG. 27-Graph showing number of wildcat wells, 1951 FJG. 28--Graph showing number of new pool discoveries. through 1980. 1951 to 1980. The 1980 number is 55 discoveries.

-----

1016 Williston Basin, North Dakota

.!II'_ ..1'0°"'" .I ~,!~:"

WILLIAMS

Me KENZIE

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• 8~T~~"E:~U .,. . .' II ~

~

Me HENRY! U WAR 0 •

•

MC~E:AN

G R A NT

0 ~ _

100 IIIILES,

FIG, 29-Producing fields in North Dakota, 1970,

• u

•• •

EMMONS

SHERIDAN'

MCHENRY

+ ~

o,,

", WAR 0

MCLEAN

,~~,-. ' ...... .-.T~E. •. "

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HETTINGER

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•

:

,"

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o

~

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If' "

Carlson. C. G., 1960, Stratigraphy of the Winnipeg and Deadwood For­mations in North Dakota: North Dakota Geol. Survey Bull. 35, 145 p .

--- and S. B. Anderson. 1966. Sedimentary and tectonic history of North Dakota part of Williston basin: AAPG Bull., v. 49. p. 1833­1846.

Carroll, W. K.. 1979. Depositional environments and paragenetic porosity controls. opper Red River Formation, North Dakota: North Dakota Geol. Survey Rept. Inv. 66, 51 p.

--- and L. C. Gerhard. 1979. Dolomitization in upper Red River Formation (Upper Ordovician). North Dakota (abs.): AAPG Bull., v. 63, p. 430.

Clark, T. H., and C. W. Stern, 1968. Geologic evolution of North America: New York, Ronald Press. 570 p .

Clemen!, J. H., 1976, Geologic history~key to accumulation al Cedar Creek Cabs.); AAPG BUll., v. 60, p. 2067·2068

---. and T. E. Mayhew, 1979, Newpone discovery opens new pay: Oil and Gas Jour.. v. 77, no. 27. p. 165-172.

Craig. L. C., 1972. Mississippian System, in Geologic atlas of the Rocky Mountain region, U.S.A.: Rocky Mountain Assoc. Geologists, p. HXl-III .

Donofrio, R. R.• 1981, Jmpact craters; implications for basement hyd­rocarbon production: Jour. Petroleum Geology, v. 3. no. 3, p. 279­302.

Dow. W. G., 1974, Application of oil correlation and source-rock data to exploration in Williston basin: AAPG Bull.. v. 58, p. 1253-1262.

Estelle, D.• and R. Miller, eds., 1978, Economic geology of the Williston basin: Williston Basin Symposium, Montana Geo!. Soc .. 447 p_

Foster, N. H .• 1972, Ordovician System, in Geologic atlas of the Rocky Mountain region. U.S.A.: Rocky Mountain Assoc. Geologists, p. 76-86.

Fuller, J. G. C. M., 1961, Ordovician and contiguous formations in North Dakota, South Dakota, and Montana: AAPG Bull., v. 45, p. 1334­1363.

~

u ~

~

•

EM MO "IS

SHERIDAN

Me HENRY w A II 0

MCLEAN

ETTINGE R

-fe-poll! Butit'

A DAM S

~ DU-'

~ s" TAR K

~ B a,..W t:I ..A N

o ~o ,

100 IlILU I

A- New field

* Apparent

dis

new

coveries for

discovery

1980

FIG. 3D-Producing fields in North Dakota, 1980. Note large number of new fields in western North Dakota south and west of Nes~

son anticline.

Lee C. Gerhard et af 1017

Gerhard, L. C" and S. B. Anderson. 1979. Oil exploration and develop­ Groenewold. G. H., 1979, Active and proposed lignite mines and related ment in North Dakota Williston basin: North Dakota Oeo!. Sun'ey consuming facilities in western ~orth Dakota: North Dakota Geo!. Misc. Series57.19p. Survey Misc. Map 20.

--- --- 1981. Oil exploration and development in the North Harris, K_ L., et al. llJ&l, An evaluation of hydrothermal resources of Dakota Williston basin; 1980 update: \forth Dakota GeoL Survey North Dakota; phase II final technical report: Univ. North Dakota Misc. Series 59. 19p. Engineering E"perimem Stalion l:IulL MI-05-EES-02.

-------and j. Berg. 1978, Mission Canyon porosity development. Heck, T., 1978, Depositional environments of Ihe Botlineau interval Glenburn field. North Dakota, Williston Basin, in The economic (Lodgepole) in North Dakota, in The Economic geology of the geology of the Williston basin: Williston Basin Sympo<;.ium, Montana Williston basin: WiIli!i.ton Basin Symposium. Montana Geol. Soc_. P Geol Soc" p. 177-189 191-203.

Grenda. J. C, 1978. Paleozoology of oil well cores from the Tyler Hoganson, 1. W.• 197M. Microfacies analysis and depositional environ­Formation (Pennsylvanian) in North Dakola, U.S.A., in The eco­ ments of the Dupcrow Formation (Frasnian) in the North Dakota part nomic geology of the Williston basin: Williston Basin Symposium. of the Williston basin. in The economic geology of the Williston basin: Montana Geol. Soc., p. 249-263. Williston Basin Symposium, Monlana Geol. Soc., p_ 131-144.

PRAIRIE SALT ISOPACH

~-- --,r __ I

~\' ~ , --. SASKATCHE~_", " " -,_ _ W~N'ill"", '--"'" -- MANITOBA-k:f

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:',,,.

",'-,'•• \ , ,'" I' ,',... \'" II' O, .........\ <'c:b ,I"' I'I '",,''=".~ 0 I' ... - ." \' ' ' ,,,-. .,IJ>' .' _ ~,,__ I ,r.,J

"I ,::;~,l '.: 1lOU I ,,~ 'l;:; ", ' ,I , I

"'"'V I ,,~ , ~-,' I-b\...... ,,...,.,,' 9:~ 't · ", ~ I I I}& , ' " ' , l.lU ... I __ ,------" c( / ' " .,,~ -' I I

\ '_. '" :\ \ ,,0 / //~\ oJ • 1\ \ " f ,."

1 "r' '­......... " I \ \ '... "0' ,' ­.............. ,, ,,' I ",g... ' ... _ .. ' 0 '

,..... ... - ,'1;' I , 'VO ---.',' I

N '., ..... 0>' I I ......... ~ " '......... ", ",,0l ....... ... .... - , .. ""

I..~'" ----,... " ..." ,_ ... " te.'Y·',i,....... ".....~~ ... ,," 0'<­'0 0 10 20 30 ~ MU.ES 0' ..... -- .. "'; ,,~t

I It, I , , " I DI"on\O 10 0 '0 20 30 40 KILOMETERS

CONTOUR INTERVAL 100ft MONTANA I NORTH DAKOTA

FIG. 31-lsopach map of Prairie salt in Montana and North Dakota, showing limit of Prairie salt. Modified from Anderson and Swinehart (1979)_

w E DANIELS l:Ol.t1lTY

MONTANA ' &OTTINEA..., COUNTY, "IORTtt [W(()TA

hl~ Plo;n, _ ..' . "._ _ __ lrail Mtlllber \ Top of Ptairil

.... ~::,·~.T .~cc..""" ~.;::;? ...... MoM'" I~m."~

- ~mber EIlerhot1 »,"'h, IJ'l!PY~_-&IL _....

.--'"""-­S'li l .--/----....

filS.! ;,!.--.--.-­Do'''''' Top 01 !~~ P,a r>e FOl",ol,on "

" 200 Fft' I

'--- ­'0 "I,'"

OJ()~TH Dhor ... IOTAe I<£S(I""C[:"> 50illU,O.. '0"15

FIG. 32-Cross section from Daniels County, Montana, through Bottineau County, North Dakota, showing potash beds within Prai­rie Formation. Shaded zones are potash bearing. Modified from Anderson and Swinehart (1979).

1018 Williston Basin, North Dakota

f----­ -

I-- ­ _ c_ __ AN-l, __ A_ D A "" ~---- '~w'-'o'j""!" I . ~_ -­ ---I , • Ii'

7'iY' -'>"/!7' rf~::~ ­ I WILLISTON!?)'"

W;~ l;r·· ~ BASIN !i>-."J)./ I. \~,1,J "\

~- . "'~~., ~ ~". I )'v~1'~ 14.. 111/'I p f# \?i", , ­ -!'D~A i./:.,.1 'Y

J ' - - - _~RTH pAt<OTA,

WYOM,.G __ lI''lii...:t.7 < 'Of,. I!'" "- 'll.'" ~ ­ _.J <·,-·.HI, /'> \ ~\"" ~ i ••':g-ti' ~~,. j;l, (;~ I \~? ~ ~ ~' Y-Jw.u/~ ! ­ _ _ _ ~OUTH DAKOTA

I j

"v' Bo~ndQry oj - ­I gn Ie beor,n <;oal C3no

<l depos'h

N t S,,,ppab1e

I J

co'; •

I,gn. Ie don"epoS'ls

o 50I ! Iqo Miles

FIG. 3.l-Map showing distribution of strippable coal depos­its in Williston and Powder River basins of North Dakota, Montana, and Wyoming. Modified from USGS Miscellaneous Map MF·540 (\974).

Kearns, J. R.. ana 1. D. Tl<tut, 1979, MISSISSlppl:ln di"coverie~ revi\'c the Willt~ton ba"in: Worlu all. \. HHI, no. 6, p. 52-57.

John~ton, R. R., 1980, North American drilling activity in 1979: AAPG Bulf., v. 64, p. 11~5-r.nO

Laird, W. M., 1964, Re~ume (Jf the ~tratigraphy and structure of N(Jrth Dakola: 3d Inlcrnal, Williston BaSin Syrnpmium, p. 39-49.

Lerud, J., 1982, Lexicon of stratigraphic names of North Dakota: ~orth

Dakota Oeo!. Survey Rep\. Inv. 71. l3Y p. Lochman-Balk, C , 1972, Cambrian Sy~tem, if! Geologic atla~ of the

Rocky Mountain region, U.S. A.: Rocky Mountain A~soc. Geologists, p 60-76

Macauley, G" et aI, 1964, Chapter 7, Carboniferous in geologic history of weslern Canada: Alberta Soc. Petroleum Geologist~, p. 89-102

Mallory, W. M 1972<1. Pennsylvanian arkose and the Ances(ral Rocky \1ountain~, in Geolo):':!c atlas of the Rocky Mountain region, U.S.A.: Rocky Mountain A~~oc. Geo1ogisl~, p. 131-IJ3.

--- 1972b, Regional ~ynthesis, ill GeologiC atlas of lhe Rocky Moumain Region, U.S.A.: Ko..:ky Moumain A~SUl; Gc:ulogists, p. 1J1-J2g

PanoI1, E. S., G. W. Henderson, and L J Conti, ]975, Red Wing Creek field------\.:tJ~mio..: impaCi sHucturc (abs,): AAPG Bul!., v. 59, p. 2197

PoTter, J. W. and J. G. C. M. Fuller. 1959. Lower PaleozoiL' rocks of northern Williston basm and adjacent areas: AAPG Bull., v. 4.1, p. 124-190

Rascoe, 8., and D. L. Baars. 1972, Permian System, in Geologic atla~ of the Rocky Mountain region, U.S.A,' Rocky Mountain Assoc Geologl~l, p. 143·166.

Roehl, P., 1967, Carbonate facies, Williswn basin and Bahamas: AAPG Bull., v. 51, p. 1979·2033.

Ross. R. J., Jr., 1957, Ordovician fossils from wells in the Williston basin, ea~lern Montana: U.S, Gco!. Survcy Bull. 1021-M, P 439-510.

Scott. M. W., 19SI, Annotated bibliography of the geology of North Dakota, 1960-1979: North Dakuta Geol. Survey Misc. Series 60. 287 p

f'.:·~··~~1 CANNONBALL

_LUDLOW

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Al

4815••~ ••- ••• --o- • ....................TC

50305029

..;,;,;;,;.: .•..~ ....... ,;",;.::;.;:;----.

:....

7094

6090

F"';:;l ~~~~lr~~\RBEUE~TE E========l SLOPE

A

.--_-_-_-_-_-_-t-_-_-_-_~_-_-_-_-_-_~_-

-:-:-:-:-:-:; -:-:-:-?-:: ==: - ------~-~-----~----------- - ­ - ­

- - ­ - - - ­ - ­ - - ------------------------­ -----------------------­ - -

r,c:.::.~.::~~»~::~;{;;.;.:~:}}t'< , ~

------ ­----~-- -----~ - ­ - ----------------------­

:~~?~~~kffr}::.:~ Ii;IIrtJ ;.~. !~""i.':;":., ... ~: :.:....L' ~,. . tJ

BILLION TONSRESOURCES 350 RESERVES 20 BILLION TONS

FIG. 34-Diagrammatic cros.\ section of Paleocene rocks in western North Dakota showing relationship of lignite beds and stratia graphic units. Numbers at vertical dark lines refer to North Dakota Geological Survey drill·hole control.

1019 Lee C. Gerhard et al

.. '=' ~

3o

" ,~

= .~"'t) ~ ~

~

~-" -'2...,

~ ~,

~

1lD =

~ ,,1 =:?~<::::7«' -c:.::"

-~

® Known slriPflQblt lignite deposits

~ Area of known, but less well ?i5 defined lignite deposi~

=:j Llmil olllonite-beor...o stratD

• ExislinQ ''9'1It. "I"P m,ne o Proposed lIOnlte striP mine

~ EIUstioQ electric poww okJnt

& Proposed electnc power plonI

.ci. ~ cool OGSlif,coOOn~. II 0ItMr fOC~il1 uftIllino lignite

/l---, {J) = ,N c::::::7 ~

V"'-J ~

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HG. 35-Map showing strippabte lignite deposits and development areas of lignite in North Dakota. Note heavy concentration of active or proposed usage of lignite northwest of Bismarck. Modified and redrawn from Groenewold (1979).

COAL PRODUCTION l> X>­

14,279,. '0­

" " 11.,

"

.'~ o ,

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~- ~

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)­

)­ ~r~ 7056

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~~

).00 '2522 2~'" ~

2557 ~ 2,520 2,520 '2 758

,­,­

960 I 196 962 I '963 I 196 l'il65 I 1966 I 1967 I 1968 I 1969 1 1970 I 19'71 I 1972 I 19731 1974 I 197!1 1 1976 I '977 I '~'8 I U79

FISCAL YEARS

FIG. 36--Graph showing production of coal (lignite) in North Dakota 1960·79. Note steady increase ill production from 1966 to 1974 with jump in 1976 and additional increases following. The increases in 1976-79 apparently reflect increasing demand for electrical generation replacing other sources of energy.

1020 Williston Basin, North Dakota

Slo~~. L. L . 1963, Sequence;; in the cratOnic intenor of North America Geol. Soc. America Bull., v. 74, p. 93-114

Stewart, J. H., 1972, Initial deposits in the Cordilleran geosyncline: evidence of a late Precambrian (850 m.y.) continental separation: Geol. Soc. America Bull., v. 83, p. 1345-1360.

Thomas. G. E., 1974, Lineament-block tectonics; Williston-Blood Creek Basin: AAPG Bull., v. 58. p. 1305-1322.

U.S. Geological Survey, 1974, Stripping coal deposits of the Northern Greal Plains, Montana, Wyoming, North Dakota, and South Dakota: U.S. Geol. Survey Misc. Fields Sludie;; Map MF-590.

Warner. L. A., 1978, The Colorado lineament: a middle Precambrian wrench fault system: Ceol. Soc Amenca Bull., v, 89, p. 161-171.

Williams. J. A .. 1974. Characterilation of oil type:. in the Williston basin: AAPG Bull.. v. 58. p. 1243-1252.

Worsley, N., and A. Fuzesy, 1978, The potash-bearing members of fhe Devonian Prairie evaponte of southeaslern Saskatchewan south of the mining area, In Economic geology of the WillJ~ton basin: Williston Basin Symposium. Montana GeoJ. Soc., p. 153-165.

Ziebarth. H. c.. 1964. The Tyler Formation of southwestern North DakOla: 3d Infernal. Williston Basin Symposium, p. 119-126.