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1984 Depositional cycles and coral distribution, Mission Canyon and Charles Formations, Madison Group (Mississippian), Williston Basin, North Dakota Douglas L. Waters University of North Dakota
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Recommended Citation Waters, Douglas L., "Depositional cycles and coral distribution, Mission Canyon and Charles Formations, Madison Group (Mississippian), Williston Basin, North Dakota" (1984). Theses and Dissertations. 316. https://commons.und.edu/theses/316
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DEPOSITIONAL CYCLES AND CORAL DISTRIBUTION, MISSION
CANYON AND CHARLES FORMATIONS, MADISON GROUP
(MISSISSIPPIAN), WILLISTON BASIN, NORTH DAKOTA
by Douglas L. Waters
Bachelor of Science, St. Lawrence University, 19 79
A Thesis
Submitted to the Graduate Faculty
of the
University of North Dakota
in partial fulfillment of the requirements
for the degree of
Master of Science
Grand Forks, North Dakota
August 1984
L This thesis submitted by Douglas L. Waters in partial fulfillment of the requirements for the Degree of Master of Science from the Univer sity of North Dakota is hereby approved by the Faculty Advisory Commit tee under whom the work has been done.
This thesis meets the standards for appearance and conforms to the style and format requirements of the Graduate School of the University of North Dakota, and is hereby approved.
Dean of the Graduate School ..
ii l Permission
Title~___ ....;I)~e=p..:::.o-=-s-=-it::...:i:..;:;o..:.;n:c::a:..:l_C;:::;...<.y...a::c;.:.le~s....:a:::.:n..:::.d;:;.....;C:;...o:::.:r:...::a:..:l:....=I):...:i.=.s..:.:tr:..:ic::::b:..:u=-=-t.:.:io::..:n~,-=Mc:..:..:.i.:.s.::.s.:.:io:::.:n~--
Canyon and Charles Formations, Madison Group
(Mississippian), Williston Ba sin, North I)akota
I)epartment Geolo ----'"--'--...... ------I)egree___ ....;M~a:..::sc.:ct..:::.ec:...r ....:o:.::fc...=S.:::.c=..:ie::...:nc;:.,;c=-e=------
In presenting this thesis in partial fulfillment of the requirements for a graduate degree from the University of North I)akota, I agree that the Library of this University shall make it freely available for inspection. I further agree that permission for extensive copying for scholarly purposes may be granted by the professor who supervised my thesis work or, in his absence, by the Chairman of the Department or the I)ean of the Graduate School. It is under stood that any copying or publication or other use of this thesis or part thereof for financial gain shall not be allowed without my written permission. It is also understood that due recognition shall be given to me and the University of North I)akota in any scholarly use which may be made of any material in my thesis.
i .·
iii •. ;,•,<'le
TABLE OF CONTENTS 'i t
LIST OF ILLUSTRATIONS. Vi
ACKNOWLEDGMENTS ix
ABSTRACT .... xi
INTRODUCTION . 1
Mississippian Tectonic Setting of the Williston Basin Previous Work Lithostrat igraphy Depositional Environments Mississippian Coral Zoogeography and Biostratigraphy Purpose Methods and Material Studied
LITHOLOGY AND DEPOSITIONAL ENVIRONMENTS • 40
Grouping of Associated Rock Types into Suites and Subsuites Description of Lithologic Suites and Subsuites Depositional Environments and Subenvironments Depositional Cycles
CORAL FAUNA ...... 73
Analysis of Coral Fauna Coral Zonules Age Determinations of Madison Intervals Evaluation of Time Parallelism of Madison Marker-Defined Intervals Coral Provinces Use of Coral Zonules for Subsurface Exploration Suggestions for Future Work
;
~· iv ' L' CONCLUSIONS ...... 113 SYSTEMATIC PALEONTOLOGY . 119 r APPENDIX . . . . . 157 ~ f REFERENCES CITED 162
;
V < ·."'' '. '":~ ' ' '~i:t>-,.·'G~r~.··'':~.":·;, __ , :· ,· '
LIST OF ILLUSTRATIONS
Plate
1. Cross-section A-A' in the Madison Group of North Dakota ...... In Pocket
2. Cross-section B-B' in the Madison Group of North Dakota ...... In Pocket
3. Cross-section C-C' in the Madison Group of North Dakota ...... In Pocket
4. Rock Types from the Madison Group of North Dakota. . . . . 45
5. Rock Types from the Madison Group of North Dakota. . 4 7
6. Rock Types from the Madison Group of North Dakota. 49
7. Rock Types from the Madison Group of North Dakota. . 51
8. Corals from the Madison Group of North Dakota 148
9. Corals from the Madison Group of North Dakota . 150
10. Corals from the Madison Group of North Dakota 152
11. Corals from the Madison Group of North Dakota 154
12. Corals from the Madison Group of North Dakota 156
Figure
1. Plate Tectonic Model for the Western United States during Middle Mississippian Time ...... 3
2. Paleogeographic and Lithofacies Map of the United States during Middle Mississippian Time . , .... , .. 6
vi . 1.
3. Major Structures in the Williston Basin 8
4. Paleogeographic Map of Western United States and Canada during Madison Time ...... 12
5. Age Relationships of Madison and Madison Equivalent Strata ...... 14
6. Typical Gamma-Ray Response for Strata of the Madison Group in West-Central North Dakota . . . . . 23
7. Coral Provinces and Subprovinces of North America during Meramecian Time . . . . . 31
8. Location of Well Cores Used in this Study. 37
9. Lithologic Suites and Subsuites of Madison Strata . 43
10. Depositional Environments and Subenvironments of the Mission Canyon and Lower Charles...... 59
11. Depositional Model for the Mission Canyon and Lower Charles ...... 61
12. Depositional Cycles of the Mission Canyon and Lower Charles ...... 71
13. Occurrence and Abundance of Coral Taxa in NDGS Well No. 7207 ...... 77
14. Occurrence and Abundance of Coral Taxa in NDGS Well No. 6230 ...... 79
15. Occurrence and Abundance of Coral Taxa in NDGS Well No. sos ...... 81
16. Occurrence and Abundance of Coral Taxa in NDGS Well No. 511 ...... 83
17. Occurrence and Abundance of Coral Taxa in NDGS Well No. 480...... 85
18. Occurrence and Abundance of Coral Taxa in NDGS Well
No. 1350 . . . ' ...... 87 ;
vii J
19. Occurrence and Abundance of Coral Taxa in NDGS Well No. 527 ...... 89
20. Occurrence and Abundance of Coral Taxa in NDGS Well No . 60 7 • . • . • • • • • . • . • . . • • • . • . • . . 91
21. Occurrence and Abundance of Coral Taxa in NDGS Well No. 38 ...... •...... 93
22. Composite Ranges of Coral Taxa and Proposed Coral Zonules for the Mission Canyon and Lower Charles Formations ...... 97
•
Viii ACKNOWLEDGMENTS
I would like to thank Dr. F. D. Holland, Jr. for suggesting the problem and serving as chairman of my committee. Discussions with him concerning the subject matter were invaluable for the preparation of this thesis. Dr. Alan M. Cvancara and Dr. John R. Reid, who served as committee members, are to be thanked for their many helpful ideas and suggestions concerning the study. Mr. Sidney B. Anderson of the North
Dakota Geological Survey contributed much of his time and expertise with well log correlations.
I am deeply indebted to Dr. William J. Sando and his assistant,
Mr. Keith R. Moore, of the U.S. Geological Survey, Washington, D. C. , for preparation of coral thin sections and the photographs of them. I also appreciate the many hours that Dr. Sando spent with me discussing coral morphology and bio stratigraphy during my visit to the U.S. National
Museum in Washington, D.C. He has been an unending source of encouragement throughout this study.
Mr. Robert F. Lindsay of Gulf Oil Exploration and Production
Company helped in the initial phase of this study with rock descriptions and environmental inteq:~retations. Mr. James C. Pol and Mr. Paul K. • Mescher of ARCO Exploration Company are acknowledged for their keen
ix ,•
interest in the study and their many helpful suggestions. Mr. David M.
Petty of Tenneco Oil Exploration and Production Company is to be thanked for discussing many thought-provoking questions about Mississippian stratigraphy with me.
Tenneco Oil Exploration and Production Company and ARCO Explora tion Company are gratefully acknowledged for providing two separate grants to aid in the research presented here. The funds provided supplies and services for the preparation of the thesis.
The North Dakota Geological Survey is acknowledged for providing the use of its facilities and equipment during examination of the core.
Finally, I wish to express my appreciation to my wife, Susan, for her support and encouragement during my academic endeavors at the
University of North Dakota.
.,
X .•
ABSTRACT
The distribution of corals, other fossils, and rock types of the
Madison Group in the Williston Basin were studied in 29 cores (involving
over 6,200 feet of core) from the Bottineau, Tilston, Frobisher-Alida, and
Ratcliffe intervals in the western half of North Dakota. Occurrence of rock types, corals, and other fossils (brachiopods, bryozoans, red algae, and gastropods) of the Mission Canyon and lower Charles Formations were plotted in three cross-sections against the informal marker-defined
intervals (Tilston, Frobisher-Alida, and Ratcliffe), as identified from well logs. Distribution and abundance of corals in nine of the more
extensive cores were related to interpreted depositional environments.
Three regressive carbonate cycles, corresponding to the Tilston,
Frobisher-Alida, and Ratcliffe intervals, were recognized for the Mission
Canyon and lower Charles. Each depositional cycle was interpreted to
comprise five successive depositional environments (I, Supratidal-Intertidal;
II, Intertidal; III, Restricted Marine; N, Transitional; and V, Open-Marine) and six subenvironments. Each cycle begins with rocks representing an
open-marine environment (V), followed by rocks representing progressively
shallower environments (IV, III, and II) and culminating in rocks represent • ing a supratidal-intertidal environment (I) at the top of each cycle.
xi Ninety-two percent of the coral fauna is dominated by four genera.
Forty-five percent of the coral fauna consists of Vesiculophyllum, 18
percent of Sychoela sma, 17 percent of Amplexizaphrentis, and 12 percent
of Cyathaxonia. The remaining 8 percent of the coral fauna consists of
Syringopora, Siphonodendron, Stelechophyllum, Michelinia, Lophophyllum, and Amplexocarinia. This study is the first record of occurrence of
Stelechophyllum micrum and .£· banffense in the conterminous United
States. The occurrence of these two species in southwestern Alberta
indicates a connection between the Mississippian Alberta shelf and the
Madison depositional complex in North Dakota.
As the result of this study, four coral zonules are proposed for the
Williston Basin of North Dakota; in ascending order they are: the
Stelechophyllum micrum zonule, the Michelinia-Cyathaxonia zonule, the
Stelechophyllum banffen se zonule, and the Siphonodendron oculinum zon ule. Diagnostic z onule index corals were found in different lit ho log ie s representing several" depositional environments, and the zonules were
found to parallel the Madison markers which define the intervals. This
supports previous suggestions that the marker-defined intervals are time-parallel units in North Dakota. Moreover, the coral zonation can be
used in the central part of the basin beyond the limit of the defining log
markers.
Coral biostratigraphic data suggest that the Bottineau interval is
late Kinderhookian to early Osagean in age, the Tilston interval is middle ,;
Osagean, the Frobisher-Alida is late Osagean to early Meramecian, and
the Ratcliffe is early Meramecian ... Xll . '
INTRODUCTION
Mississippian Tectonic Setting of the Williston Ba sin
The model (Fig. 1) of the broad structural and tectonic framework that controlled Mississippian deposition in the western United States, as proposed by Poole (1974) and refined by Poole and Sandberg (1977), shows an east-dipping subduction zone below an island-arc system.
Eastward and adjacent to the island arc was an inner-arc basin. During increased plate motion and accelerated subduction, Devonian and older siliceous sediments of the inner-arc basin were obducted or thrust upon the outer continental shelf, creating the Antler, orogenic highland.
Below this deformed structural complex was a complementary west-dipping subduction zone of the North ~merican continental crust.
Compressive stresses related to these plate movements caused the continental crust directly eastward of the Antler highland to buckle downward, developing the Antler flysch trough of the foreland basin.
East of the foreland basin was the cratonic platform where shelf carbonates accumulated. In the southern portion of the foreland basin, during Osagean to early Meramecian time, a submarine rise separated .. the Antler flysch trough from a basin of slow sedimentation named the
1 • ..
2
Figure 1. Plate tectonic model for the western United States during middle Mississippian time. (Slightly modified from Poole and Sandberg, 1977.)
.. Kl!a1111111•1.mua111 irn11•, , , , n- I lftl- n, j , , , , --~!f !@! !!¥3- !Ill:: ,Trd: •rw: ;: as;;;,_ ··-w;tt,·:.;::r~..,;,v,a r%}"'-;"';4>.-.:~·_.ir,.,,, __ :· .. ':·:~ .... , r
t i!~. ,i'
w E rt FORELAND BASIN
2. I.
I. CRATONIC PLATFORM 5. INNER ARC BASIN 2. STARVED BASIN 6. ISLAND ARC 3. FLYSCH TROUGH 7. OUTER ARC BAS IN 4. ANTLER OROGENIC HIGHLANDS ~?:·~;~ -NORTH AMERICAN 1 '·'"·' CONTINENTAL CRUST
If '•i,-
.. 4 ! ! "Deseret starved basin" by Sandberg and Gutschick (1980) but discussed in a paper by Rose (1976). In the northern portion of the foreland basin
(north of the Deseret Basin), the flysch trough abutted directly against the cratonic platform, and the trough was supplied with sediment from both the Antler highland and the carbonate platform (Gutschick, 1983).
East of the cratonic platform was a positive, southwest extension of the
Canadian shield, the Transcontinental arch. Figure 2 shows the extent of the "Deseret starved basin" and other paleogeographic features during the middle Osagean. The Cordilleran miogeosyncline of Sando (197 6) is roughly comparable to the foreland basin mentioned in later studies.
The Williston Basin (Fig. 3) was an intracratonic basin that appears to have been both structurally and depositionally controlled during most of the Paleozoic and early Mesozoic. The outline of the
Williston Basin as defined by Laird (1965) was drawn, except for parts of the western boundary, at the zero elevation line on the top of the Dakota
Group. Approximately 134,000 square miles are circumscribed by this boundary. Connecting on the western side of the Williston Basin with the Cordilleran miogeosyncline is the central Montana or Big Snowy trough, an area of increased subsidence during the time of deposit ion of the Madison Group (Sloss, Dapples and Krumbein, 19 60; Smith and
Gilmour, 1979; Peterson, 1981; Maughan, 1984). This is the general
,· area of Figure 2 called th~ "Madison Shelf" by Gutschick and Sandberg
(1983). The central Montana trough divides the more stable portion of 5
Figure 2. Paleogeographic and lithofacies map of the conterminous United States during middle Mississippian time (from Gutschick and Sandberg, 1983, p. 84).
.. '·-~h·;;;-~· ~.-;,.,,7'«... ~~··;.~ = ·,:;..:.,..,·
:··-.. /<:> ,...... ~ •::·· ..... ( /0 l !/ NORTH AMERICAN CRATON :;.. •... ~ / - -:.. :- : :!"'!:" F ...:~ ,o/ ?: . II ( j / ·' '· \ i I <:;A• i i '> ..\. \ ·, '
cf u $ o" ~ /'f.
SEDIMENT TRANSPORT ~l'),~.I 1 I I l_'I, DIRECTION
••+ Inferred ...... --...... _.. Mean paleocurrent ···\, \ ~' : ... ~l \ 0 500 MILES \,1 \. I SOUTH AMERICA ~ ~ ~ \ . 0 500 KILOMETERS ...... :._.,,} 0/ ,oc:,.,,,,. ,<:>/ q;
·tir:
• ....-»J~,; ;,-s.,·:::.:J:;;::...:;:~.. ::~,.:~ .. :.... -;;.~·" .~.:: •, ...... _..,...._~.--_...... __<-.,.»---· ·----·~· ~- ...,. "'
7
Figure 3. Generalized diagram of major structures in the Williston Basin (outline of basin from Laird, 1956, p. 16; structures from Gerhard et al., 1982, p. 991, and Ballard, 1963, p. 2 and 34).
.- wfWoU Z\~ ::,, ':;,, O\i l\o. 1,cs:.- g. -r,\~ ~\ SASKATCHEWAN "f; MANITOBA
NORTH POPLAR IJESSON \ DAKOTA OOMX I TNTICLINE_ ) \ C>FOSTER HIGH SHEEP MT. +UTILE KNIFE SYNCLINE f ANTICLINE I BURL~H HIGH\ BILLINGS / ANTICLINE I qJUTSMAN HIGH SOUTH MONTANA DAKOTA
WYOMING 0 100 MILES l J
,. .. 9 the cratonic platform into two separate shelves, the Alberta shelf on the north and the Wyoming shelf to the south (Smith and Gilmour, 1979).
Major structures in the Williston Basin are the Nesson and Cedar Creek anticlines, the Poplar dome and the Sheep Mountain syncline. The
Ne sson anticline is located in northwestern North Dakota and is a major structural feature of importance to the oil industry. It trends north-south for 75 miles, plunging to the south, and is 15 miles wide (Sandberg,
1962). The Nessen anticline was intermittently active through much of the Paleozoic and subsequent time (Laird and Folsom, 1956; Sheldon and
Carter, 1979). The Nessen anticline may have provided a barrier that restricted marine environments to the east during deposition of the upper part of the Mission Canyon Limestone. The Cedar Creek anticline, another structure that is significant to the oil industry, is 12 5 miles long and trends northwest-southeast from northwest South Dakota to east-central Montana (Sandberg, 1962). The Cedar Creek anticline was intermittently active from the middle Devonian to the early Mesozoic
(Sandberg, 1962; Clement, 1976). It, too, may have affected deposition in the Williston Basin during Madison time (Sheldon and Carter, 1979;
Catt, 1982).
Gerhard et al. (1982) believed the origin of the Williston Basin was related to the movement of Precambrian basement rocks. They suggested .. that the structures in the basin, and the basin itself, may have resulted from renewed movement along the Precambrian Colorado-Wyoming 10 lineament and Fromberg zones during the Phanerozoic. A hinge line between the Precam~ian Churchill and Superior provinces may have influenced basin development during the Phanerozoic (Ballard, 19 63;
Laird, 1964; Gerhard et al., 1982). Other structural elements in western
North Dakota are the Billings, Little Knife, and Antelope anticlines. In the eastern part of the basin in North Dakota, the Burleigh, Foster, and
Stutsman highs are important structural features (Ballard, 19 63).
Previous Work
Lithostratigraphy
A brief discuss ion of the lithostratigraphy and type sections of the
Madison Group and correlative rocks is given below. It is not the purpose of this study to show all the Madison correlatives along the western interior of North America; therefore, particular areas were chosen where significant co_ral biostratigraphic work has been done and which have provided a background for comparison with coral faunas and lithologic relationships of the Miss ion Canyon and Charles Formations in the Williston Ba sin of North Dakota. Figure 4 shows the location of these areas in the Western Interior of the United States and Figure 5 shows their age relationships based on coral zones mentioned in this study.
The Madison was originally described by Peale (1893) from good .- exposures in southwest Montana and defined as a formation with its type 11 ::r \ \ :
Figure 4. Paleogeographic map of western United States and Canada during Madison time. Numbers refer to areas where significant stratigraphic and coral biostratigraphic work has been done (Fig. 5) in the Madison and Madison-equivalent strata (sources for paleogeographic map: Sando, 1977a, p. 15; Ziegler, 1969, p. 16; Stevens et al., 1979, p . CC 1 5; Guts chick , 19 8 3 , p . 8 4) .
.. ., 0,
0 200
(:PJ,;j - Land E2] Flysch Trough ~ Cratonic Platform m Antler Highlands .- B - Starved Basin 1: s"'.,~l - Inner Arc Basin 13
Figure 5. Age relationships of Madison and Madison-equivalent strata based on coral biostratigraphic units. Numbered columns refer to areas numbered on Figure 4.
.. 4. 6. WESTERN NORTHERN SW. ALBERTA NORTH DAKOTA I. 2. 3. 5. N.AMERICA ROCKlfS NELSON 1900 ( SUBSURFACE ) NORTH DAKOTA S. W. ALBERTA SOUTHWEST W.CENTRAL NORTHEAST NORTHERN ::,; (/) ARIZONA w w SANDO AND SANDO ET EMEND.M.OCOUEEN WATERS SUBSURFACE kEASTERN FACIES MONTANA WYOMING UTAH Ii; a: BAMBER, AL., 1969 AND BAMBER, (THIS STUDY ) SMITH, 1960 MACQUEEN ET AL., SANDO AND GUTSCHICK CRAWfOf() MTS SANDO, >- w 1972 ET AL.,1900 GUTSCHICK ET 1969 (/)
p/f-llum _,,,, D E 5'9frd>o-1 Sipl>ono- bo;11,1 ,,,,,,,.,,,,,,,
C >-- I-a: PRE-E B Ma.JNT ct. ,_ ~ - HEAD - Si,tlonodtfndron - - ~- - - - III POPLAR z slnuosum
-.
•. 15
section located on the Gallatin River at Logan, Montana. Collier and
Cathcart (1922) elevated the Madison to group status. Sloss and Hamblin
(1942, p. 313) mentioned that the type section for the Madison is on the
Gallatin River at Logan, but they did not precisely locate it nor did they give any indication that they collected a reference set of fossils.
Holland (1952, p. 1702, 1703) gave a precise location for the Madison type section and diagrammed a measured section for the lower part of the
Madison Group. He also listed fossils collected from the Lodgepole
Formation of the Madison. Sando and Dutro (1974) precisely located,
described the lithology and collected fossils from the type section of the
Madison and each of the formations of the group.
The Lodgepole Limestone was proposed by Collier and Cathcart
(1922) for rocks exposed on the flank of the Little Rocky Mountains in north-central Montana. The Lodgepole is 550 feet thick at its type
section, and consists of argillaceous, thin-bedded limestone with chert
nodules.
The Mission Canyon Limestone was also proposed by Collier and
Cathcart (1922) for rocks exposed on the flank of the Little Rocky
Mountains. The thickness of the Mission Canyon is given (Sando and
Dutro, 1974) as 861 feet at a reference section in the Little Belt
Mountains of north-central Montana. The formation consists of .. fine- to coarse-grained, fragmental, massive, limestone. 16
In the subsurface of North Dakota, the Madison Group is made up of three formations that are, in ascending order, the Lodgepole Lime stone, the Mission Canyon Limestone, and the Charles Formation. The
Lodgepole Limestone is 52 5 to 850 feet thick in the center of the Williston
Basin (Sandberg, 1962) and its lithology varies from dark, argillaceous, thin-bedded limestone in the center of the basin to light colored, skeletal and oolitic limestone toward the edges of the basin.
The Mission Canyon Limestone is 350 to 775 feet thick in the center of the Williston Ba sin (Sandberg, 19 62) and its lithology is extremely variable, ranging from dark, argillaceous skeletal lime stone to light, skeletal and oolitic limestone and, increasingly, to dolostone and anhydrite toward the top.
The Charles Formation was proposed by Seager (1942) for a series of beds lying between the Big Snowy Group and the Madison Group (as then understood) in the Arro Oil Company and California Company's
Charles No. 4 test well, in Garfield County, Montana. The Charles is
525 to 725 feet thick in the center of the Williston Basin (Sandberg, 1962) and is dominated by anhydrite, dolostone and salt but commonly possesses a basal, dark, argillaceous, skeletal limestone.
Rocks equivalent in age to the Madison in southwestern Alberta, from oldest to youngest, are the Banff, Pekisko, Shunda, and Turner .. Valley Formations and the lower part of the Mount Head Formation. The upper four formations make up the Rundle Group. In west-central 17
Wyoming the Madison is considered a formation because the Lodgepole and Mission Canyon Formations are not clearly recognized (Sando, 19 67).
Two formations in the Crawford Mountains of northeastern Utah are equivalent to the Madison Group. They are, in ascending order, the
Lodgepole Limestone and the Brazer Dolomite. The Madison equivalent in northern Arizona is the Redwall Limestone.
Based on the lithologic resemblance to the Lodgepole and Mission
Canyon Formations as exposed in the Little Rocky Mountains of Montana and to the Charles Formation in the subsurface of eastern Montana,
Seager et al. (1942) introduced the Lodgepole, Mission Canyon and
Charles Formations into the subsurface of North Dakota. Petroleum geologists, recognizing the difficulties in correlating complex inter tonguing lithologies (Lodgepole, Miss ion Canyon, and Charles) of the
Madison in the subsurface of the Williston Basin, found it more con- venient to use intervals bounded by marker "horizons" identified on well logs. Such marker-defined intervals had the advantage of being independent of internal lithologic criteria that were used in preceding definitions of the Madison formations in the subsurface.
Thomas (1954) was one of the earliest subsurface workers to utilize something similar to marker-defined intervals in the Williston Basin.
Using electric and radioactive logs, he subdivided the Mission Canyon .. into five "members, " designated M. C. 1 to M. C. 5, in the north ea stern 18 portion of the Williston Basin. He interpreted these "members" as repre senting limestone cycles terminated by "persistent silt zones."
Porter (1955, p. 128) considered the thin elastic bands within a limestone-evaporite sequence that can be picked on mechanical logs to be time lines. He thought that these thin cla stic bands probably repre sented times of epeirogenetic fluctuation. He also suggested that the
Lodgepole, Mission Canyon, and Charles lithologies grade from one to the next laterally along these time lines as well as vertically within the entire Madison complex of southeastern Saskatchewan and southwestern
Manitoba.
As an outgrowth of the preceding studies, Fuller (195 6a) termed the main carbonate sequence of the Madison Group the "Madison Limestone" and distinguished it from the "'Charles' Evaporites" of the Madison
Group. He subdivided his II Madison Limestone" into a series of beds bounded (p. 13) "by 'marker' horizons, that is, by ... special 'features' of the electrical curves, which in the carbonate sequence are usually argillaceous seams. 11 The beds between these marker horizons were named from districts where they produce oil. These units and the
"marker horizons, 11 in ascending order, were the Lower Madison
Limestone bounded at the top by an unnamed "marker horizon," the
M. C. 1 Lime stone bounded at the top by the M. C. 2 "marker horizon," .- the Forget-Nottingham Limestone, bounded at the top by the Kisbey
Sandstone "marker horizon," the Hastings-Frobisher Beds, bounded at 19 the top by the Frobisher Evaporite "marker horizon," the Midale Beds, bounded at the top by the Midale Evaporite "marker horizon," and the
Ratcliffe Beds, bounded at the top by the Lower Salt of the "Charles"
Evaporite.
In 19 5 6, the Saskatchewan Geological Society Mississippian
Names and Correlations Co:nmittee met to standardize the subsurface terminology in the northeastern part of the Williston Bas in. They applied the name Souris Valley Beds to a sequence of rocks equivalent to the
Lodgepole Formation of Thomas (19 54) and the "Lower Madison Lime stone" of Fuller (1956a, p. 14). The Name Tilston Beds was applied to rocks equivalent to Thomas' (19 54) M. C. 1 and M. C. 2 members. The name Frobisher-Alida beds was introduced to embrace the M. C. 3,
M.C. 4, and M.C. 5 members of the Mission Canyon Formation of
Thomas (19 54) and the Forget-Nottingham Limestone, the Kisbey Sand stone, and the Hastings-Frobisher Beds of Fuller (1956a). The name
Midale Beds was retained from Fuller's (1956a) original definition. The name Ratcliffe Beds was applied to rocks above the Midale Beds and below a 100-foot-thick interval of anhydrite and mudstone which includes the "last" or lower "Charles" salt of the Nesson anticline area of North
Dakota. The name Poplar Beds was applied to rocks above the Ratcliffe
Beds and below the overlying Kibbey Limestone.
Fuller (1956b, p. 32) subdivided his "Charles" Evaporites into five .. evaporitic and dolomitic units. They were, in ascending order: the "Lower 20
Salt equivalent, Poplar B dolomite, Unnamed evaporite unit, Poplar A dolomite, and Upper Salt equivalent."
In a companion paper appearing in the same volume with Fuller
(1956b), Harrison and Flood (1956) subdivided the Charles in the northeastern portion of the Williston Basin into a series of eight marker-defined intervals. They regarded the marker-defined intervals as eight distinct "cyclothems" separated by eight anhydritic "marker" horizons. The relationship of Harrison and Flood's (1956) subdivisions of the Charles to that of Fuller's (1956b) subdivision is not clear.
Fuzesy (1960, p. 39) accepted Fuller's (1956b) subdivision of the
"Charles Evaporite s" but renamed them P 1 to PS (as contractions of
Poplar Beds) and claimed that these subdivisions could be traced on mechanical logs throughout their area of occurrence in Saskatchewan.
Smith {19 60) redefined, for subsurfa_ce work in North Dakota, some of the marker beds proposed by the Saskatchewan Geological Society
( 19 5 6). He redefined the boundaries of the Poplar, Ratcliffe, and
Frobisher-Alida Beds, dropped the name Midale Beds, and replaced the name Souris Valley Beds with the name Bottineau. He also dropped the use of the term "Beds" and, in its place, used the term "interval," recognizing that the stratigraphic code did not consider para-time-rock units as formal units. Redefinitions of these marker-defined intervals .. in the subsurface of North Dakota are discussed by Anderson et al.
(1960, p. 4-5) and Carlson and Anderson (1966, p. 3). 2 1
Harris et al. (19 66) developed their own system of marker-defined units for upper Mission Canyon strata in north-central North Dakota that has received much attention and use by the petroleum industry in several areas of North Dakota.
This study employs the informal subsurface Madison terminology of the North Dakota Geological Survey (Smith, 19 60; Anderson et al., 19 60;
Eastwood, 1961; Ballard, 1963; Carlson and Anderson, 1966) super imposed on formal Madison lithostratigraphic units (Lodgepole, Miss ion
Canyon, and Charles Formations). I agree with the Saskatchewan
Geological Society (1956) and Fuzesy (1960, p. 14) that the Mission
Canyon-Charles contact might be drawn at the top of the Frobisher-Alida interval because this interval often contains the lowest extensive evaporite unit in Saskatchewan and North Dakota. The Miss ion
Canyon-Lodgepole contact is placed at the top of the Bottineau interval.
Figure 6 shows the subsurface terminology used in this study and the inferred age relationships based on coral biostratigraphic data.
Several problems with informal subsurface intervals became apparent to me during this study. One problem is that in the center, of the Williston Ba sin, lower Madison interval (Tilston and Bottineau) boundaries cannot always be defined due to the absence of thin elastic units (marker horizons) that normally separate these intervals farther .. east. Carlson and Anderson (1966, p. 3 and 8) had also discovered this in their studies. Furthermore, the assertion (e.g. Porter, 1955; ..
22
\.
I 11 I I ',
Figure 6. Typical gamma-ray log response for strata of the Madison Group in west-central North Dakota, showing informal, marker-defined, interval boundaries, formal rock units, and age relationships based on coral biostratigraphic data of this study.
• NDGS NO. 607 KENNEDY F-32- 24 P SW/NE SEC 24,Tl49N.,R.93W DUNN COUNTY
I- I- a:0:: 0::a: KIBBEY FORMATION j
?- z 8500 Q I- < POPLAR f ::, (/) 0:: :NTE~~ ':!! 0 SENSITIVITY 0:: Le. CHANGE w (/) (/) w ...J ~,z 0:: a::~ < I u I u RATCUFFE INTERVAL 1:11 9000 ln >- en z0 I- - z (/) < en w u S£NSmv1r1 en 0:: z en bl Q 9500 en (/) ~I~ z (/) <.:> :E < 0 (/) (/) 0 a, z Q I- <( (/) IOO w :::;; BOTIINEAU 0:: ci: 0 INTERVAL w Le. (/) w ...J z 0 <( Cl.. w ><:: <.:> 0 a 0 0 I ...J Cl::w a z ;;:: .. z BAKKEN Cumming et al. , 19 59) that 11 marker horizons" are time planes, based solely on the evidence that they are thin, extensive, elastic units that interrupt carbonate-evaporite sequences, without substantiation by biostratigraphic data, raises a question serious enough to be considered a real problem. Depositional Environments I did not begin this project with a preconceived depositional model in mind; rather, interpretation of faunal and lithologic data during core and thin section analysis agreed with similar findings of other workers on the Mississ(ppian in the Williston Basin. Ideas on depositional environments developed by Edie (1958), Irwin (1965), Harris (1966), Lindsay and Roth (1982), and Elliott (1982) were those most applicable to this study. Edie (1958) described four major environments for formation of the Mission Canyon and lower Charles in southeastern Saskatchewan; they were, from offshore to onshore: (1) basin, (2) shelf and "bank" margin, (3) "bank," and (4) lagoon. He also further subdivided these major environments. The rock types he ascribed to the basin environment were represented by "dark brown-grey argillaceous limestones containing scattered white crinoid columnals, black bituminous shale partings and brownish grey chert." Rocks formed on the shelf and "bank" margin were .. composed of "cream-white fossiliferous-fragmental and chalky limestones 25 containing crinoids, bryozoans, brachiopods and zaphrentid corals." Rocks from his "bank" environment consisted of "cream-white precipitated lime stones including pi so lit ic, oolitic, pseudo-oolitic, and lithographic types. Fossils include abundant algae and few scattered gastropods. " The lagoon environment was said to be represented by "cream-white chalky argillaceous limestone containing ostracodes, earthy to sucrosic secondary dolomite and anhydrite. " Edie (1958) also made several perspicacious interpretations of the rock types he observed. He found (p. 340) the color of "shelf-type" limestone to be lighter than that of "basin-type" limestone because of better oxidation of the shelf carbonate rocks as contrasted with the presence of organic carbonaceous and disseminated iron sulphide material in "basin-type" sediments deposited in a reducing environment. Edie (p. 342) considered pisolites to be of algal origin, oolites to be chemically precipitated, and pseudo-oolites probably formed by a combination of these processes. He (p. 342) also recognized primary and secondary dolomite. He considered primary dolomite to form directly as an evaporite characterized by a cryptocrystalline habit and commonly intermixed and interbedded with anhydrite. He said that secondary dolomite possesses a sucrosic texture and intercrystalline porosity and commonly replaces skeletal material. .. Irwin (19 65) proposed three, broad, energy zones thought to occur in epeiric seas--zones X, Y, and Z. Zone X, a low-energy zone, was ,> 26 farthest offshore and extended for hundreds of miles. Zone Y was a high-energy zone where skeletal matter was winnowed and broken by wave and tidal action; it was tens of miles wide. Zone Z was a shallow, low-energy zone, tens to hundreds of miles wide. He described six sedimentation zones associated with the three energy zones. He became aware of the sedimentation zones during his studies of Mississippian sedimentation patterns in North Dakota and South Dakota. Energy zone X had one sedimentation zone, designated I. Energy zone Y had two sedimentation zones, II and III. Energy zone Z had three sedimenta tion zones, IV, V, and VI. Sedimentation zone I consisted of animal skeletal calcisiltite derived from adja9ent shoreward zones. Zone II was composed of skeletal calcarenite. Zone III consisted of oolites, pseudoolites, peloids, and bioclastic carbonate. Zone N was composed of chalky dolomite. Zone V consisted of evaporites. Zone VI was composed of algal mud stone, oolites and pelletoids, and represented a normally saline environment that had been freshened with river and rain water and produced abundant algal growth. Irwin claimed that three factors governed the width of the sedimentation zones: (1) climate, (2) barriers, and (3) slope of the sea floor. Harris et al. (19 65) presented a depositional model for the upper Mission Canyon strata (Frobisher-Alida) of North Dakota that was very similar to that of Edie (1958). Four environments were recognized: .- basin, shelf, bank, and lagoon. The basin environment was characterized 27 by formation of dark, argillaceous, fine-grained mud stone with rare fossils. The lithologies of the shelf environment consisted of light colored, fine- to coarse-grained, skeletal limestone with thin beds of oolitic and algal lime stone containing crinoids, bryozoans, and corals. The lithology of the bank environment was composed predominantly of light colored, oolitic-pisolitic-algal lime stone. The lithology of the lagoon environment was composed of anhydrite and evaporitic dolomite, with thin beds of oolitic limestone, shale, salt, and dolomitic lime stone. They reported that the environments in north-central North Dakota migrated with time to the southwest and that this indicated a regression of the sea to the southwest. They also discussed the distribution of marker beds in the upper Mission Canyon and suggested that the marker beds composed of terrigenous elastic material were deposited during abrupt, short-lived, transgressions of the sea. Lindsay and Roth (1982) regarded the Mission Canyon of the Williston Basin as a regressive-upward, shoaling complex in an epeiric sea that was later covered by an advancing sabkha. Five subtidal environments and one intertidal-supratidal complex were distinguished at the Little Knife field. Lindsay and Roth related their subtidal environ ments to Irwin's energy zones X, Y, and Z: (l) Low-energy, basin-marine environment represented by argillaceous, laminated, skeletal pelletal .. pack stone grading into skeletal mudstone/wacke stone corresponding to Irwin's energy zone X. (2) Open, shallow-marine environment 28 represented by mudstone and skeletal wackestone interbedded with skeletal packstone/grainstone corresponding to part of energy zone Y. (3) Transitional, open to restricted marine environment represented by burrowed skeletal wacke stone/dolowackestone and mudstone/dolomudstone corresponding to part of energy zone Y. (4) Restricted marine environment represented by mudstone and dolomudstone, part of Irwin's energy zone Z. (5) Marginal marine environment represented by skeletal wackestone and mud stone, part of energy zone Z. Lindsay and Roth (1982) mentioned that intertidal buildups composed of pisolitic-oolitic-peloidal-oncolitic and skeletal packstones capped lithologies of the subtidal marine environment. Immediately behind and r interfingering with the intertidal buildups they reported lagoonal rocks consisting of mudstone, algal laminated mudstone/dolomudstone, and anhydrite. There appears to be a slight discrepancy between the lithologies associated with Irwin's (19 65) original zone Y and those which were interpreted by Lindsay and Roth (1982). Irwin described oolites-pseudoolites and peloids in sedimentation zone III of energy zone Y, which seem most similar to the lithology of Lindsay and Roth's intertidal buildup accumulations which they placed in low-energy zone Z. Elliott (1982) examined the "Glenburn zone" of the Mission Canyon .. in the Haas field and distinguished two separate facies: a cyclic, coated-grain facies and a peloidal, intra elastic facies. The cyclic, 29 coated-grain lithofacies was reported to consist of skeletal wackestone and oolitic, pisolitic packstone/grainstone and was probably formed as a shoal. The peloidal, intraclastic lithofacies was said to consist of sparse skeletal wackestone/packstone, dolomite, and peloidal, interclastic packstone/grainstone with minor ooids and pisoids formed in a lagoon, sheltered behind the previously described pisolitic-oolitic shoal. Silty, patterned dolomite, considered by Elliott to represent marker beds, was said to have been deposited in these lagoons during maximum restriction or desiccation prior to sabkha evaporite deposition. Mississippian Coral Zoogeography and Biostratigraphy There have been several studies of Mississippian coral biogeography and zoogeography of North America: Hill (1948, 1957, 1973), Vasilyuk et al. (1970), Sando et al. (1975), and Fedorowski (1981). Three major North American coral provinces were distinguished by Hill (19 7 3): the : I 'l I Mississippi Valley province, the Western Cordilleran province, and the ! Nova Scotia province. Sando et al. (197 5), using similarity and endemism indices, renamed them the Southeastern, Western Interior, and Maritime provinces and included two other coral provinces, the Alaskan and the Pacific Coast provinces. In addition, Sando et al. (1975) subdivided the Western Interior province into the Southern, Central, and Northern subprovinces and.the Pacific Coast province into the Northern .· and Southern subprovinces (Fig. 7). Some of the coral provinces and .. 30 Figure 7. Coral provinces and subprovinces of North America during Meramecian time. Horizontal lines indicate land, stippled pattern indicates shallow-water, non-coralliferous rocks, and plus pattern indi cates occurrence of shallow-water coral-bearing rocks: NPC represents the Northern Pacific Coast subprovince, SPC represents the Southern Pacific Coast subprovince, CWI represents the Central Western Interior I ,i 1' subprovince, SWI represents the Southern Western Interior subprovince (from Sando et al., 1977, p. 181). •. CANADIAN SHIEL MARITIME PROVINCE 600"4fLES 1--,-li..,,.--..., LI -.JI eoC>KIL.OflCTERS • ____lllill ______...... ___ ...... _ _ _,_._ __ , 32 subprovinces appeared or disappeared during different times in the Mississippian. Coral provinces of Sando et al. (1975) provide a con venient way to compare coral assemblages of North Dakota to the various coral assemblages of the Western Interior province. The areas dis cussed in the lithostratigraphy section (Figs. 4 and 5) are all in the Southern Western Interior subprovince with the exception of southwestern Alberta, which is in the Central Western Interior subprovince. Mississippian coral zones for the Madison and correlative strata in the northern Cordilleran region were established by Sando (19 60a) and Sando and Dutro (19 60). Later studies by Mudge et al. (19 62), Dutro and Sando (19 63), and Sando (19 67a, 19 67b) led to a more complete zonation scheme for the northern Cordilleran region (Sando et al., 19 69, and Fig 5). Sando et al. (19 69) found that time relationships of their coral-brachiopod zones compared favorably to foraminiferal zones of Mamet and Skipp (1970) in Madison and Madison-equivalent strata. Faunal elements of coral-brachiopod zones of Sando et al. (1969) can be recognized over a broad region from Montana to northern Arizona. Ten colonial rugose coral zones were proposed by Nelson (19 60) 11 for southwestern Alberta. In a later study, Nelson (19 61) developed a 'I ' i:1 ,.;I' coral-brachiopod zonation for the entire western Canadian region. In :11' subsequent studies by Macqueen and Bamber (1967, 1968) and Macqueen .: et al. (1972), some of Nelson's zones were revised (Fig. 5). 33 In the Southwest Easton and Gutschick (1953) described a coral fauna and documented ranges of taxa from the Redwall Limestone of northern Arizona but did not propose a coral zonation scheme. In later studies of the Redwall Limestone, Sando (19 64, 19 69) proposed local coral zones and found the coral fauna of the Redwall to be very similar to the coral fauna of the northern Cordilleran region. Armstrong (19 62) had described a coral fauna from southeastern Arizona and southwestern New Mexico but Sando (19 69) considered this fauna to be more similar to corals of the Southeastern coral province than to corals of the Western 'I: Interior province. Several other coral faunas from Madison-equivalent strata in the r ,, Southwest have been studied--Stensaas and Langenheim (1960) in ·1'l ".I ·/ · east-central Nevada, Langenheim and Tischler (19 60) in ea stern I ·1·.'' California, and Easton (1958) in Sonora, Mexico--but none of these authors proposed coral zones. l I. Only three papers are concerned with coral biostratigraphy in the subsurface of the Williston Basin. Brindle (1960) illustrated and listed corals, brachiopods, and mollusks from well cores in southeastern Saskatchewan. Sando (19 60b) described and illustrated Madison corals I I from cores of three wells in eastern Montana. Sando (1978) continued ' his coral biostratigraphic research in the Williston Basin by incorporating .: corals from three more wells in eastern Montana and one well in North Dakota. In that study, he recognized several coral zones in the 34 subsurface and discussed temporal relationships of units within the Madison. Still, he included only the one well core from North Dakota with a meager coral fauna. Recently, Sando and Bamber (19 79; and, in press) have developed a new system of coral zonation that encompasses the entire Western Interior province. Their coral zones are designated by Roman numerals and are further subdivided into subzones as shown in Figure S. It may not be possible to recognize the subzones everywhere because they are characterized by fewer index taxa. Purpose In view of the fact that previous studies provided only limited information on the distribution of corals in relation to carbonate litho- facies in the Mission Canyon and Charles Formations in the subsurface of North Dakota, it _was decided to pursue detailed studies of these features. Thus, this study has the following five purposes. 1. Determine the distribution of corals in the Mission Canyon and Charles Formations from well cores from the Williston Basin of North Dakota. 2. Evaluate, insofar as possible, time parallelism of Madi son marker-defined intervals with coral biostratigraphic data. 3. Correlate Williston Basin coral-bearing rocks with pre .. viously established coral zones of the Western Interior. 35 4. Interpret depositional environments of the Mission Canyon and Charles Formations from lithologic and paleontologic data obtained from the well cores in North Dakota. 5. Relate the distribution of corals in these formations to the interpreted depositional environments. Methods and Material Studied Cores from more than 50 wells from North Dakota were examined for this study. Of these, 29 (Fig. 8) were described in foot-by-foot detail. These cores are permanently housed in the Wilson M. Laird Core and Sample Library of the North Dakota Geological Survey on the campus of the University of North Dakota. A total of 6,274 feet of Madison core included 917 feet of core from the Ratcliffe interval, 3,745 feet from the i I Frobisher-Alida interval, 909 feet from the Tilston interval, and 703 feet 1 ' I:r 1., from the Bottineau interval. The longest core described was 600 feet. ! 1 Nine cores from the Poplar interval of the Madison were examined but not described, because no corals were found from lithologies (salt, shale, anhydrite, and dolomudstone or mudstone) deemed to indicate an environment too inhospitable for them. Twenty-nine cores were prepared and described according to the following method: (1) Cores were cleaned with a scrubbing brush and • water in a 4-gallon galvanized tub. (2) Segments from most of the core 36 Figure 8. Location of wells from which cores were used in this study. Cores from NDGS Well Nos. 4683 and 5639 were not described but contained diagnostic coral taxa and thus were included on this loca tion map. Cross-sections A-A', B-B', and C-C' constructed from this core study are shown as Plates l, 2, and 3 (in pocket). • <( l . o .,• "'<( 0 0 "'0 . z X l a: 0z z.-- / / I \ I \ I \ / \ I / \ I \ \ / I \ / \ / I / \ \ \ \ / / ' ; \ / \ I I ... I u I C / ... ..;.u ii: • 38 were briefly etched in a 1-gallon bucket of 10 percent HCl acid to reveal texture and lithology. (3) If the surface of the core was rough or grooved from the coring operation, the surface was sanded with coarse emery paper mounted on a rubber disk in the chuck of a 1/4-inch electric drill or the core was slabbed to provide a better surface for examination. (4) Numbers and types of corals, miscellaneous faunal and floral elements (gastropods, bryozoans, ostracodes, brachiopods, and red \' ' algae), rock color, and lithology (using Dunham's, 1962, classification of carbonate rocks) were recorded for every foot of core examined. The best coral specimens (except where extremely abundant) were collected from the core for thin sections and illustration and to provide a set for descriptive taxonomic work. Small coral specimens were collected in core plugs by using a 1 1/2-inch diameter rotary plugging machine. Large coral specimens were collected using a slab saw or trim saw. A slab 1/2-inch thick was removed from selected cores to obtain a study set of the various lithologies. Approximately 150 thin sections were made from various rock types for petrographic analysis. Three cross-sections of the Ratcliffe, Frobisher-Alida, and Tilston intervals (Fig. 8, Sections A-A', B-B', and C-C'; and Pls. 1, 2, and 3) were constructed to illustrate and compare coral distribution, lithologic •· suites, informal subsurface intervals, formal rock units, and coral bio- stratigraphic units. The entire Bottineau interval was not included in 39 these cross-sections because of the scarcity of corals and the lack of extensive core in this interval. After the corals were identified and counted, abundances of coral taxa were plotted against stratigraphic position and interpreted deposi tional environments for the most continuous cores (Figs. 13-21). Most of the corals could be identified directly from the core, although polish- ing was commonly necessary to reveal diagnostic structures in the coral specimens. Thin sections of corals were rarely needed for coral taxa determinations; however, coral thin sections provide more morphologic detail and are better for illustrating structures than are polished slabs. Both polished slabs of corals and coral thin sections were illustrated (Pls. 8-12). The coral material is catalogued into the Paleontology Collection of the University of North Dakota. '1'" .: LITHOLOGY AND DEPOSITIONAL ENVIRONMENTS Grouping of Associated Rock Types into Suites and Subsuites Rock names used in this study employ Dunham's (1962) textural classes (mudstone, wackestone, packstone, and grainstone). Attached to these textural classes are modifiers from names of grain types (pisolites, oolites, pseudoolites, peloids, oncolites, algae, and lithoclasts) or fossil types (crinoids, brachiopods, ostracodes, gastropods, and foraminiferids). Occasionally the kind of fossil material is unrecognizable and the term skeletal is used. Bioturbation may be a major feature of the rock so this is indicated by the adjective burrowed. Hyphens separating grain or fossil types in rock names indicate that one, all, or any combination of fossil or grain types can occur in the various textural classes of Dunham (19 62). For example, the rock name "pisolitic-oolitic packstone or grainstone" can be several different rock types, such as pisolitic packstone, oolitic packstone, or pisolitic and oolitic packstone or any of these combinations of grain types in a grainstone. The order of abundance or dominance of grain types or fossil types decreases from left to right. In the rock name above, pisolites would be the more abundant grain type. The order of abundance 40 41 of occurrence of textural classes also decreases from left to right. In the rock name above, packstone would be the dominant textural class. Because of the varied lithologies {Pls. 4-7) it was found more convenient to group rock types into rock associations, here called lithologic suites and lithologic sub suites. Lithologic suites are not merely random groupings of rock types but represent rock associations of similar origin that can be distinguished from each other visually as well as stratigraphically. Five major lithologic suites designated with Roman numerals and six subsuites in three of these lithologic suites designated with letters (a) and {b) are recognized (Fig. 9). The lithologies most often observed are listed under each lithologic suite and subsuite in order of decreasing abundance. These lithologic suites and subsuites, along with corals and other fossils that were observed in cores, were plotted on three cross-sections (A-A', B-B', and C-C'; Pls. l, 2, and 3). Description of Lithologic Suites and Subsuites Lithologic suite I {Fig. 9) consists primarily of anhydrite, I dolomudstone and mudstone. The anhydrite may be massive, ii 1!,'ii !, Ii "chicken-wire," or layered (Pl. 4, fig. 1). Dolomudstone or mudstone I· may be layered or massive and in some places it is displaced by nodular anhydrite (Pl. 4, fig. 2) or i:s interlayered or laminated with anhydrite • (Pl. 4, fig. 4). Small porphyroblasts of anhydrite after gypsum may T'Mbk e 42 Figure 9. Lithologic suites and subsuites of Madison strata in the Williston Basin of North Dakota. Symbols are the same as those used in cross-sections A-A', B-B', and C-C' as shown on Plates l, 2, and 3 (in pocket). • ,• Lithologic Suites and Subsuites (I) Lithologic Suite I 1. Massive and chicken-wire anhydrite 2. Interlayered anhydrite and dolomudstone or mudstone 3. Nodular displacive anhydrite in dolomudstone 4. Dolomudstone with porphyroblasts of anhydrite 5. Mud stone or dolomudstone 6. Patterned dolostone 7. Algal laminated mudstone or dolomudstone --Some deposits may be burrowed, rare gastropods (II) Litholagic Suite II (a) Lithologic Subsu1te Ila 1. Peloidal-algal-oncolitic wackestone or mudstone 2. Ostracode-<,astropod and sparse skeletal wacke stone or mudstone 3. Mud stone or dolomudstone 4. Pisolitic-oolitic-peloidal wackestone or mudstone 5. Stromatolit!c limestone or dolostone Fossils: Gastropods and ostracodes (b) Lithologic Subsuite Hb l. Pisolitic-oolitlc-peloidal packstone or grainstone or wackestone 2. Peloidal-algal-oncolit!c-lithoclastic packstone or grainstone or wackestone 3. Foraminiferid-pseudoolitic and rounded skeletal pack- stone or grainstone 4. Stromatolitic lime stone or dolostone 5. Skeletal wackestone Fossils: Gastropods, ostracodes, foraminiferids, corals, crinoids and brachiopods Common texture: Fenestral fabric (III) Litholagic Suite III I. Burrowed dolomudstone or mudstone 2. Ostracode and sparse skeletal-peJoidal mudstone or wackestone 3. Mudstone 4. Minor nodular and displac1ve anhydrite II Fossils: Gastropods, foramimferids and rare corals (IV) Lithologic Suite IV (al Lithologic Subsuite Na I. Burrowed crinoid, brachiopod dolowackestone or wackestone 2. Burrowed mudstone or mudstone interlayered with skeletal wackestone or packstone or grainstone 3. Sparse skeletal wackestone Fossils: Foraminiferid s, gastropods. corals, red algae, bra ch iopod s and bryoz oan s (b) Lithologic Subsuite Nb 1. Crinoid, brachiopod-peloidal wackestone 2. Peloidal-oolitic wackestone or packstone alternating with skeletal wackestone or mudstone Fossils: Corals, red algae, brachiopods, bryozoans and gastropods (V) Lltholag ic Suite V (al Lithologic Subsuite Va 1. Crinoid, brachiopod wackestone 2. Mudstone with lenses of crinoid-brachiopod lj wackestone or packstone ii 3. Mudstone with random sparse skeletal debris :i Fossils: Crinoids. brachiopods. corals, fene strate H bryozoans, red algae, and gastropods ii (b) Lithologic Subsuite Vb 1. Skeletal pack stone and grain stone 2. Rounded skeletal (? pelotdal) pack stone or grain stone ,: interbedded with skeletal wackestone Fossils: Fenestrate bryozoans, cnno1ds, brachiopods and corals 44 EXPLANATION OF PLATE 4 Figure 1 Bedded, "chicken-wire" anhydrite, Suite I, Frobisher-Alida interval, NDGS Well No. 60 7 at 9,065 feet below KB. 2 Stromatolitic mud stone and displacive nodular anhydrite, Suite I, Ratcliffe interval, NDGS Well No. 7207 at 9,307 feet below KB. 3 Patterned mudstone, slightly dolomitic, Suite I, Frobisher- Alida interval, NDGS Well No. 60 7 at 9,269 feet below KB. 4 Algal laminated mudstone and anhydrite, Suite I, Ratcliffe interval, NDGS Well No. 60 7 at 8,968 feet below KB. ,i 1 2 4 46 EXPLANATION OF PLATE 5 Figure 1 Mud stone, slightly dolomitic, with porphyroblasts of anhydrite, Suite I, Frobisher-Alida interval, NDGS Well No. 44 55 at 9,304 feet be low KB . 2 Peloidal-algal-oncolitic wackestone, Subsuite IIa, Ratcliffe interval, NDGS Well No. 7207 at 9,348 feet below KB. 3 Peloidal-oncolitic and sparse skeletal wackestone, Sub suite IIa, Frobisher-Alida interval, NDGS Well No. 527 at 9,902 feet below KB. 4 Peloidal-lithoclastic packstone and grainstone, Subsuite IIb, Frobisher-Alida interval, NDGS Well No. 3944 at 3,865 feet 'I t below KB. .. 2 48 EXPLANATION OF PLATE 6 Figure 1 Oolitic wackestone and packstone, Subsuite IIb, Frobisher Alida interval, NDGS Well No. 607 at 9,229 feet below KB. 2 Pisolitic-oolitic pack stone and grain stone, Subsuite IIb, Frobisher-Alida interval, NDGS Well No. 607 at 9,113 feet below KB. 3 Burrowed, slightly dolomitic mud stone with gastropods, Suite III, Ratcliffe interval, NDGS Well No. 60 7 at 9,011 feet below KB. 4 Burrowed skeletal wackestone with Vesiculophyllum (top) and Syringopora (near bottom), Sub suite Na, Ratcliffe interval, NDGS Well No. 7207 at 9,380 feet below KB. .. 1 2 3 50 EXPLANATION OF PLATE 7 Figure 1 Skeletal and peloidal wackestone with Vesiculophyllum and red algae, Sub suite IVb, Frobisher-Alida interval, NDGS Well No. 607 at 9,305 feet below KB. 2 Skeletal wackestone, Subsuite Va, Frobisher-Alida interval, NDGS Well No. 7207 at 9,661 feet below KB. 3 Skeletal pack stone and grain stone, Sub suite Vb, Tilston interval, NDGS Well No. 6230 at 10,049 feet below KB. 4 Silicification of skeletal wackestone, Subsuite Va, Frobisher Alida interval, NDGS Well No. 7207 at 9,744 feet below KB. ,; 52 occur in the dolomudstone (Pl. 5, fig. 1). Algal laminated rnudstone and dolomudstone are recognized by their thin, irregular, discon- tinuous laminations (Pl. 4, figs. 2 and 4). Discrete beds of peloidal-algal-ostracode mudstone or wackestone may also occur in this suite but they are uncommon. Patterned dolostone with dissemi nated pyrite and elastic material is often observed near the base of this lithologic suite (Pl. 4, fig. 3). Burrows are uncommon. Gastropods are rare. In the eastern and southern portion of the study area, the Tilston interval is capped by lithologic suite I (NDGS Well Nos. 511 and 50 5 in section A-A' and NDGS Well Nos. 2 74, 939, and 38 in section C-C '). Lithologic suite I caps the Frobisher-Alida interval; there it has a much greater distributio:i. (occurs farther to the west) than it does in the pre ceding Tilston interval (NDGS Well Nos. 7207, 2 667, 4419, and 4455 in section A-A'; NDGS Well Nos. 13 50, 52 7, and 60 7 in section B-B'; and NDGS Well No. 3932 in section C-C'). Lithologic suite I in the Frobisher-Alida interval is also thicker in the ea st (NDGS Well Nos. 505 and 511 in section A-A'; NDGS Well No. 6254 in sectio:1 B-B'; and NDGS Well No. 38 in section C-C ') than it is in the Tilston interval. Lithologic suite I occurs low in the Ratcliffe interval (NDGS Well Nos. 7207, 4419, and 511 in section A-A'; NDGSWell Nos. 3235, 527, and 607 in section B-B': and NDGS Well No. 1024 in section C-C'). .. Lithologic suite II (Fig. 9) may be subdivided into two lithologic sub suites, Ila and IIb. In some instances the litholog ies from both -- 53 sub suites are so intimately associated that the subsuite cannot be differentiated; where this is the case the deposits are referred to merely as lithologic suite II. Lithologic subsuite IIa (Fig. 9) is dominated by peloidal-algal-oncolitic wackestone or mudstone (Pl. 5, figs. 2 and 3) and is often interbedded with sparse skeletal wackestone or mudstone. Occasionally pisolitic-oolitic-peloidal wackestone or mudstone and stromatolitic limestone or dolostone occur. This subsuite has a fauna composed solely of gastropods and ostracodes, animals known to be eurytopic. Sub suite Ha occurs in the middle of the Frobisher-Alida interval (NDGS Well No. 50 5 in section A-A' and NDGS Well No. 52 7 in section B-B') in the upper part of the Frobisher-Alida interval (NDGS Well Nos. 4692, 3932, and 1024 in section C-C') and in the Ratcliffe l'. interval (NDGS Well No. 7207 in section A-A' and NDGS Well No. 480 in section B-B'). Lithologic subsuite IIb (Fig. 9) has more coated grains and less J-. mud than sub suite !Ia. Subsuite IIb is composed primarily of pisolitic-oolitic-peloidal pack stone or grain stone or wacke stone (Pl. 6, figs. 1 and 2). Less common lithologies are: peloidal-algal-oncolitic-lithoclastic packstone or grainstone or wacke stone (Pl. 5, fig. 4), foraminiferid-pseudoolit ic and rounded .- skeletal pack stone or gra instone, stromatolitic limestone or dolostone, and skeletal wackestone. Gastropods are the most abundant fossils in 54 sub suite IIb and are commonly accompanied by ostracodes, foraminiferids, corals, fragmented crinoids and brachiopods. A fenestral fabric is commonly observed in the rocks. Lithologic suite IIb is present in the Tilston interval (NDGS Well No. 511 in section A-A'), in the lower part of the Frobisher-Alida interval (NDGS Well No, 62 54 in section B-B'), and in the upper part of Frobisher-Alida interval (NDGS Well Nos. 1024 and 2630 in section C-C' and NDGS Well No. 607 in section B-B'). Undifferentiated sedimentary rocks of lithologic suite II occur in rr li 1 .• ~-1· the Tilston, Frobisher-Alida, and Ratcliffe intervals (NDGS Well Nos. ii' .(' .;,·•·' : 7207, 2667, 4419, 4455, 7446, 7104, 6230, and 505 in section A-A'; NDGS Well Nos. 3235, 480, 1350, 527, and 607 in section B-B';and NDGS Well Nos. 5551, 524 7, 3944, 38, and 939 in section C-C '). Lithologic suite III (Fig. 9) is dominated by burrowed dolomudstone and mudstone (Pl. 6, fig. 3). Less common lithologies are ostracode, j .. ,,l, t.,·•. and sparse skeletal-peloidal mudstone or wackestone. Nodular, ' displacive anhydrite may be distributed randomly throughout these lithologies. Gastropods, foraminiferids, ostracodes, and rare corals are the only fossils in this lithologic suite. Lithologic suite III occurs in the Tilston, Frobisher-Alida, and Ratcliffe intervals and has a wide areal distribution (NDGS Well Nos. 2667, 5258, 4419, 4455, 7446, 7104, 6230, 505, and 511 in section A-A'; NDGS Well Nos. 480, 1350, .- 527, 607, and 6254 in section B-B';and NDGS Well Nos. 4692, 1024, 3510, 2630, 3932, 3944, and 38 in section C-C'). - 55 Lithologic suite DJ is subdivided into two lithologic subsuites, IVa and IVb. Lithologic subsuite IVa occurs more commonly than does IVb. Lithologic sub suite IVa (Fig. 9) is dominated by burrowed crinoid, brachiopod dolowackestone (Pl. 6, fig. 4). Mud stone or burrowed mudstone interbedded with skeletal wackestone or packstone or grainstone may also occur in this subsuite. Foraminiferids and gastro pods are common. Corals are more diverse and abundant in this subsuite /1.t' •!; ft' than in the preceding suites. Red algae, brachiopods, and bryozoans l;' J: l may also be present. Subsuite IVa occurs in the Tilston, Frobisher-Alida, and Ratcliffe intervals (NDGS Well Nos. 7207, 2 667, 5258, 4419, 4455, 7446, 6230, 505, and 511 in cross-section A-A'; NDGS Well Nos. 3235, 480, 1350, 527,607, and 1516insectionB-B';andNDGSWel1Nos. 4692, 1024, 3510, 2630, 3932, 3944, 38, and 274 in section C-C'). Lithologic subsuite IVb (Fig. 9), commonly consists of crinoid, brachiopod-peloidal wackestone (Pl. 7, fig. 1) but may also contain r peloidal-oolitic wackestone or packstone alternating with skeletal wackestone and mudstone. The most common fossils in this subsuite are corals and red algae. Brachiopods, bryozoans, and gastropods are less abundant. Subsuite IVb occurs in the Tilston interval (NDGS Well No. 2 7 4 in section C-C '), the Frobisher-Alida interval (NDGS Well Nos. • 480, 1350, 527, and 607 in section B-B'), and the Ratcliffe interval (NDGS We 11 No. 72 07 in section A-A'). 56 Lithologic suite V is subdivided into two lithologic subsuites Va and Vb. Lithologic subsuite Va occurs more often than does Vb. Lithologic subsuite Va (Fig. 9) consists primarily of crinoid, brachiopod wackestone (Pl. 7, fig. 2). Other rock types that commonly occur in this subsuite are mudstones with lenses of crinoid-brachiopod wackestone or packstone and mudstone with random sparse skeletal debris. Sub suite Va contains a diverse and abundant assemblage of fossils. Crinoid fragments and brachiopods are abundant. Corals are diverse and abundant. Fene strate bryozoans are common. Red algae and gastropods are less common. Subsuite Va occurs in the Tilston, ,J, Frobisher-Alida, and Ratcliffe intervals (NDGS Well Nos. 7207, 2 667, 4419, 4455, 6230, SOS, and 511 in section A-A'; NDGS Well Nos. 3235, 480, 1350, 527, and 607 in section B-B'; and NDGS Well Nos. 4692, 1024, 3510, and 38 in section C-C'). Lithologic subsuite Vb (Fig. 9) usually consists of coarse skeletal ~;'· i· packstone or grainstone (Pl. 7, fig. 3) but rounded skeletal (? peloidal) l packstone or grainstone interbedded with skeletal wackestone may also occur. Fossils are usually fragmented. Fenestrate bryozoans, crinoid fragments, and brachiopods are common. Corals are small and rare. Sub suite Vb occurs in the Tilston (NDGS Well Nos. 720 7 and 62 30 in section A-A' and NDGS Well No. 38 in section C-C') and in the .. Frobisher-Alida (NDGS Well No. 1024 in section C-C'). --·-'"-~---- 57 A major petrologic feature worth mentioning is massive silicifica tion of carbonate sediments (Pl. 7, fig. 4). Silicification appears to occur pervasively in lithologic suites III, IV, and V. It also appears to be stratigraphically controlled and occurs in the lower part of the Frobisher-Alida interval. The upper limit of s ilicification occurs at approximately the same stratigraphic interval (some 200 to 300 feet) below the top of the Frobisher-Alida interval (NDGS Well Nos. 7207, 62 30, and 50 5 in section A-A' and NDGS Well Nos. 13 50, 52 7, and 60 7 l~J! I -t .. 11·, in section B-B'). f l' Depositional Environments and Subenvironments Five major depositional environments and six subenvironments are interpreted from the five lithologic suites and six subsuites of the Mission Canyon and lower Charles in the Williston Basin of North Dakota (Fig. 10). A reconstruction of the depositional environments and subenviron 1. l , ments de scribed below is illustrated in Figure 11. !:. Lithologic suite I is interpreted as representing a supratidal-intertidal ~ environment dominated by a sabkha bordered by a broad tidal flat with scattered evaporitic ponds and lagoons. Massive anhydrite and "chicken-wire" anhydrite probably formed in the sabkha, while layered anhydrite, nodular anhydrite, and laminated anhydrite and dolomudstone or mud stone formed subaqueo1.:1sly in evaporitic ponds and lagoons. .. Patterned dolostone and dolomudstone with porphyroblasts of anhydrite I+ .. 58 Figure 10. Depositional environments and subenvironments of the Mission Canyon and lower Charles as interpreted from lithologic suites and subsuites shown in Figure 9. Symbols are the same as those used in cross-sections-A-A', B-B', and C-C' as shown on Plates l, 2, and 3 (in pocket). 'i: I '. '\' ,1 .. Lithologic Suites Depositional Environments and and Subsuites Subenvironment s I I. Supra tidal-Intertidal (Sabkha, tidal flats, evapo ritic ponds, and lagoons) II II. Intertidal IIa IIa. Lower-energy accumula- • • • • • • t ions (Tidal ponds , • • • • • • drowned tidal flats) IIb • • • • • • IIb. Higher-energy accumula- tions (Shoals and tidal •?t" i . ,LJ channels) '\' 'i III III. Subtidal Restricted Marine ~ ,, (Broad, shallow, low-angle 11 .r+ .,JI.:' ~ II shelf) lr IV IV. Subtidal Transitional Environ- ment ( !Va IVa. Restricted to open-marine IVb !Vb. Intertidal to open-marine i' f. /' •1 f, /, !, i ! V V. Subtidal Open-Marine !, Va Va. Low-energy (Gentle sloping shelf below wave base except during storms) Vb Vb. High-energy (Bottom in II contact with wave base, offshore shoals, sub- marine banks) ,· 60 Figure 11. Depositional model for the Mission Canyon and lower Charles showing inferred depositional sites of lithologic suites and sub suites for the Williston Basin of North Dakota. Roman numerals and letters refer to lithologic suites and interpreted depositional environments as shown in Figures 9 and 10. ,• 0 ·o-0 Q.) a. Q.) I C: uO - en ·--Q.) =o..:.<: u (..) C: 0 03 .2 Q.) Q.) cv a.> C ..:£ C: en o $2 -c en en -0 c: ::::, 0 .!:: E ·-uO.... 0 :!:: O'l 0 Q.) - .... -cc Sl 0 0 Et' -o ·a.~ Q.) en ·ti~. ' 3-0 u'o 0::::, ·-:=...x::en ::: E (.) ::::, .... -Oo cno 0 0.. II -0 '- 00 Q.) C ~Q.) 0 ·-.c 0C u- en 0 en - .... Q.) -0 .=: .0 ..:£ g_ ~ -u 0 O> -0 0 :.c ... ·o 3 ~ uO c- O 0 Cl) ·-0 .... '- C t~ ~ .0 0 -0 0 ..3C - Q.>- u -0 ...1/) 3 Q.) 0 ·o~ O 0..3 cu :: -0 ~ ·;:: 0 ::::, C 0 U3 CD o "O II .. ------·--·"·-----~-·---···--·-···-·---· 62 after gypsum are commonly associated with these subaqueous anhydrites. Kendall (1983, p. 151, 154, and 155; Figs. 9, 10, and 16) had a similar environmental interpretation for the "Frobisher Evaporite" of southeastern Saskatchewan. He considered layered and laminated anhydrites to form in evaporitic ponds and lagoons; and mosaic anhydrite ("chicken-wire" anhydrite) or massive anhydrite to form in sabkhas bordering evaporitic ponds and lagoons. Algal, laminated mudstones or dolomudstones with rare peloids and on co lites formed on the tidal flats and possibly in the L f; lagoons. Because of the very high salinities in these aqueous environ- men ts, the growth of preservable fossils (other than algae) was rare. ;, Only occasionally were waters fresh enough to support gastropods and o stra codes . Lithologic suite II seems to represent an intertidal environment, divided into two subenvironments. Subenvironment !Ia represents a low-energy, intertidal environment with tidal ponds and drowned tidal flats and IIb represents a higher energy, intertidal environment with shoals and tidal channels. Elliott (1982, p. 140) also differentiated two separate "facies" (a "cyclic, coated-grain facies and a peloidal, intraclastic facies") for deposits with rounded grains ill: the Mission Canyon of northwestern North Dakota as based on the microstructure of the grain types, packing of grains, and the amount of m~d content. He considered "oolitic/pisolitic .. packstone and grainstone" to be deposited across shoals and peloidal 63 and intraclastic wackestone and packstone to be deposited in lagoons behind these shoals. Although I agree with Elliott's interpretation that pisolitic-oolitic packstone and grainstone were likely deposited on shoals, peloidal and intraclastic wackestone were probably deposited in water bodies smaller than lagoons (such as tidal ponds and drowned tidal flats) whose existence was more ephemeral than lagoons as is suggested by the sporadic occurrence of such wackestones in the Mission Canyon and lower Charles of North Dakota. Within subenvironment !Ia, peloids and oncolites formed and algae grew in the tidal ponds and drowned tidal flats and were, on occasion, covered by evaporite deposition during times of hypersaline conditions. Occasionally, oolites and pisolites were swept in from the shoals (IIb) or were transported through tid:11 channels and deposited with sediments of lower energy wackestones and mud stones of tidal ponds and drowned tidal flats. Gastropods and ostracodes thrived in the waters of this subenvironment. Pisolites, oolites, and peloids of subenvironment IIb formed and accumulated in shoals and tidal channels in front of tidal ponds and tidal flats. This subenvironment was characterized by higher energy conditions and better marine circulation than existed in !Ia. Deposits of subenvironment IIb can be distinguished from those of !Ia, because .- they contain more coated grains, less mud, and often have a fenestral fabric. A greater diversity of organisms is associated with deposits of 64 subenvironment IIb; however, some of them are probably allochthonous. Numerous gastropods inhabited subenvironment IIb. Some corals were found in these deposits, primarily Vesiculophyllum and morphogroups B and C of Syringopora. Vesiculophyllum and Syringopora were commonly found relatively well preserved, indicating that they had not been transported. Other corals occurring less frequently in deposits of IIb are Amplexizaphrentis, Sychnoelasma, and Stelechophyllum micrum. Foraminiferids were also found in subenvironment IIb, but they may have :~W: I •\ct :I ·t been transported from environment III where they occurred abundantly. ·, Lithologic suite III represents a broad, shallow, low-angle shelf where marine circulation and energy were greatly reduced and thus could be considered a restricted marine environment. It is likely that the restriction of circulation was caused by the breadth and gentle slope of the bottom on this shelf. Dolomudstones and mudstones that are bio- turbated typify the lithology formed in this restricted marine environment. Lindsay and Roth {1982, p. 156) also interpreted dolomudstones and mudstones that have been extensively burrowed in the Mission Canyon of western North Dakota to represent a restricted marine environment. Peloidal and skeletal material were occasionally swept into this environ t '! ment from the intertidal environment (II) during storms. Nodular anhydrite grew displacively in these deposits during periods of hypersalinity. A .- sparse fauna consisting primarily of gastropods, ostracodes, and foraminiferids could endure these restricted marine conditions. The rare 65 occurrence of corals in deposits of environment III may indicate periods of less re strict ion. Vesiculophyllum and morphogroups B and C of Syringopora were usually the only corals that occurred in this environ ment; however, Sychnoelasma, Amplexizaphrentis, Stelechophyllum banffense, and Siphonodendron oculinum have also been observed in deposits of environment III. Lithologic suite IV represents a transitional environment between shallow, marine sedimentation (III and II) and "deeper," open-marine sedimentation (V). Two subenvironments are recognized. Subenviron- ment !Va represents a transitional environment between the restricted marine environment (III) and an open-marine environment (V). Lindsay and Roth (1982, p. 156) interpreted burrowed skeletal wackestone and dolomitic skeletal wackestone that succeed open-marine sedimentary rocks in the Mission Canyon of North Dakota to represent a transitional open- to restricted-marine environment. Subenvironment IVb represents a transitional environment between an intertidal environment (II) and an open-marine environment (V). The steepness of the shelf of environment III played a part in dictating which subenvironment of environment IV occurred. Where the shelf of environ- ment III was steep, depositional environment III was reduced or absent. In this case, coated grains and peloids were swept off the shoals or out .- of the channels of environment II, and they became mixed with the skeletal debris and lime mud common in the more open waters. This resulted in 66 peloidal-oolitic-skeletal wackestone or an interbedding of peloidal-oolitic wackestone with skeletal wackestone or mudstone. This "mixture" or interbedding of lithologies, otherwise more typical of environments II and V, was deposited in subenvironment !Vb. Vvhere there was a gentle slope in the area of environment III, formation of burrowed skeletal wackestones predominated and the subenvironment called !Va existed. Bioturbated skeletal wackestones and dolowackestones were the most common lithologies formed in subenvironment !Va. The subenviron ment appears to have been somewhat restricted, but rocks formed here contain a more diverse fauna and greater amounts of skeletal debris than those formed in environment III. Gastropods and foraminiferids are common in deposits of !Va. A diverse coral fauna .consisting of Ves iculophyllum, morphogroups A, B, C, and D of Syringopora, Sychnoelasma, Amplexizaphrentis, Cyathaxonia, Stelechophyllum banffense, Siphonodendron oculinum, Michelinia expansa, Lophophyllum, and Stelechophyllum micrum inhabited subenvironment !Va. Red algae, brachiopods, and bryozoans also inhabited subenvironment IVa. There were times when the environment became less restricted (perhaps the result of rising sea levels) and skeletal wackestone or packstone was deposited. Subenvironment IVb fluctuated between intertidal and open-marine sedimentation as indicated by a ~rinoid, brachiopod-peloidal wackestone ,· and a peloidal-oolitic wackestone or packstone interbedded with skeletal - -- --~~-----~~ 67 wackestone. Abundant fragmented red algae and corals in subenviron ment IVb indicate a subenvironment of higher energy and better marine circulation than for IVa. The corals in subenvironment IVb were primarily Vesiculophyllum and Sychnoela sma. The absence of other types of corals in this subenvironment indicates that IVb was a less favorable habitat for corals. Lithologic suite V was formed in an open-marine environment divided into two subenvironments. Subsuite Va represents low-energy I.' deposits formed below wave base on a gently sloping shelf and subsuite Vb represents a higher energy subenvironment where submarine banks and offshore shoals brought the bottom above the level of wave base. Crinoid-brachiopod wackestone is the dominate lithology formed in subenviro:-iment Va but mudstones with sparse skeletal debris were also formed in this subenvironment. Lindsay and Roth (1982, p. 155) considere.d skeletal wackestone and mudstone of the Mission Canyon of North Dakota to be deposited below wave base in a shallow, low-energy, open-marine setting. Subenvironment Va was usually below wave base except during storm activity. Storm deposits are recognized by lenses or layers of coarse skeletal debris (packstones and grainstones) surrounded by a lithology with greater mud content. This subenvironment favored a diverse fauna of fenestrate bryozoans, corals, and brachiopods. .. Subenvironment Va must have been the most hospitable subenvironment for corals as reflected by their higher diversity and greater abundance in 68 this subenvironment than in any other. The coral fauna consisted of Vesiculophyllum, Sychnoelasma, Amplexizaphrentis, Cyathaxonia, Stelechophyllum banffense, Siphonodendron oculinum, Michelinia expansa, Stelechophyllum micrum, morphogroups A, B, C, and D of Syringopora, Lophophyllum, and Amplexocarinia. The higher energy, open-marine subenvironment Vb consisted of submarine banks and offshore shoals. Deposits of this subenvironment are represented by extremely coarse skeletal grainstones and packstones 'i- whose fragments accumulated by storm, wave and possibly current activity. These accumulations must have been above wave base through out most of their existence. Lindsay and Roth {1982, p. 155) also con- sidered skeletal packstones and grainstones of the open-marine environ ment to be deposited when the bottom came within wave base. A diverse fauna s imiiar to that of Va was observed but the skeletal matter is so fragmented that it probably represents accumulations of non-living organic material. Only a few, immature individuals (found as well preserved specimens) of the coral genera Vesiculophyllum, Amplexizaphrentis, and Sychnoelasma could tolerate such a turbid environment. Depositional Cycles Three major regressive sequences or cycles, corresponding to the Tilston, Frobisher-Alida, and Ratcliffe intervals, are recognized in the .. Mission Canyon and lower Charles Formations. The three cycles 69 (indicated by Roman numerals in Figure 12) were found to display a similar sequence of rock associations or lithologic suites; these were interpreted as representing depositional environments becoming progres""' s ively shallower and eventually ending with intertidal to supratidal deposition. The onset of each cycle began with open-marine sediments tl (depositional environments Va or Vb) on top of supratidal-intertidal sediments (depositional environment I) of the previous cycle. Evidence for this abrupt change in depositional environments is observed, for example, near the contact of the Tilston interval with the Frobisher-Alida interval (NDGS Well Nos. 505 and S 11 in section A-A' and NDGS Well No. 38 in section C-C '). Similar evidence for abrupt change is also i observed near the contact of the Frobisher-Alida interval with the 1- > Ratcliffe interval; however, the change may be less abrupt with a thin unit from environment II or IV intervening between those deposited in environments I and V (NDGSWell Nos. 7207, 2667, 4419, and44SS in section A-A' and NDGS Well Nos. 1350 and 52 7 in section B-B'). In each cycle, deposits of progressively shallower depositional environ ments IV, III, and II occurred on top of deposits of environment V and the cycle eventually culminated with deposits from supratidal-intertidal conditions of environment I (NDGS Well Nos. 2 667, 4419, 50 5, and 511 in section A-A'; NDGS Well Nos. 1350, 52 7, 60 7, and 62 54 in section B-B'; and NDGS Well Nos. 3944 and 38 in section C-C'). 70 Figure 12. Depositional cycles of the Miss ion Canyon and lower Charles and marker-defined intervals in the Williston Basin of North Dakota. Roman numerals and symbols refer to lithologic suites and interpreted depositional environments as shown in Figures 9 and 10. .. CYCLE I CYCLE lI CYCLE m TILSlON INTERVAL FROBISHER-ALIDA INTERVAL RATCLIFFE INTERVAL •. .. . ·~); .+, ii·" .. • ~ .. -·== -u~ 1t • -7'1iiiT r· 7 '"')rj . In cycle I the supratidal-intertidal sediments (depositional environ ment I) capping the Tilston interval were thin and restricted to the east (NDGS Well Nos. 505 and 511 in section A-A') while more open marine sediments (IV and V) occurred in the west (NDGS Well Nos. 7207 and 6230 in section A-A'). In subsequent cycles (II and III) sediments of depositional environment I were thicker (NDGS Well No. 50 5 in section A-A'; NDGS Well Nos. 1350, 607, and 6254 in section B-B'; and NDGS Well No. 38 in section C-C') and extended farther to the west (NDGS Well Nos. 7207, 2 667, 4419, and 4455 in section A-A' and NDGS Well No. 3235 in section B-B') than they did in the Tilston cycle. This indicated that the overall retreat of the sea was westward toward the basin center. This evidence agrees with Wilson's (1975, p. 283) interpretation that during later Madison time the sea had undergone a major regress ion westward. .. L CORAL FAUNA Analysis of Coral Fauna Eleven species and four morphogroups of the following genera have been recognized in the Mission Canyon and Charles Formations of North Dakota: Sychnoelasma, Amplexizaphrentis, Amplexocarinia, Cyathaxonia, Lophophyllum, Vesiculophyllum, Siphonodendron, Stelechophyllum, '' Michelinia, and Syringopora. These genera can be broadly grouped into four categories: Nondissepimented, Solitary Rugosa Cyathaxonia Amplexocarinia Amplexizaphrent is Sychnoelasma Dissepimented, Solitary Rugosa Vesiculophyllum Lophophyllum Colonial Rugosa Siphonodendron Stelechophyllum 73 74 Tabula ta Michelinia Syringopora The following list gives the taxonomic hierarchy of the corals found, following the classification scheme of Hill (1981). Subclass Rugosa Order Sta urida Suborder Metriophyllina Family Cyathaxoniidae Genus Cyathaxonia Family Laccophyllidae Subfamily Ampexocariniinae Genus Amplexocarinia Suborder Stereolasmatina Family Hapsiphyllidae Subfamily Hapsiphyllinae Genus Amplexizaphrentis Family Zaphrentoididae Subfamily Zaphrentoidinae Genus Sychnoelasma Suborder Plerophyllina Family Lophophyllidae Genus Lophophyllum Suborder Caniniina Family Uraliniidae Genus Vesiculophyllum Suborder Lithostrotionina Family Lithostrotionidae Subfamily Lithostrotioninae .- Genus Siphonodendron Siphonodendron oculinum - 75 Subfamily Acrocyathinae Genus Stelechophyllum Stelechophyllum banffense Stelechophyllum micrum Subclass Tabulata Order Favosit ida Suborder Favositina Superfamily Favositicae Family Micheliniidae Subfamily Micheliniinae Genus Michelinia Michelinia expansa Order Auloporida Superfamily Syringoporicae Family Syringoporidae Genus Syringopora (Morphogroups A, B, C, and D) When numbers and types of corals were compared to stratigraphic position and depositional environments, as illustrated in Figures 13-21, several relationships were revealed. Ninety-two percent of the coral specimens belong to species of only four genera. Forty-five percent of the fauna consisted of Vesiculophyllum, 18 percent of Sychnoelasma, 17 percent of Amplexizaphrentis, and 12 percent of Cyathaxonia. The remaining 8 percent of the coral fauna was composed of specimens from Syringopora, Siphodendron, Stelechophyllum, Michelinia, Lophophyllum, and Amplexocarinia. Numbers of corals and the diversity of the coral j r fauna appear to be largely controlled by depth and restriction of water circulation. Coral abundance and diversity decrease eastward where .. environments became increasingly more restricted. Conversely, coral faunas are richer in the western part of the state where depositional •. 76 Figure 13. Occurrence and abundance of coral taxa in well core from NDGS Well No. 720 7 and the relationship of corals to depositional environments. While amount of core (from stratigraphic units at the left) is shown in 20-foot intervals, the column at the right represents by symbol the depositional environments interpreted from the lithologic suites as explained in Figures 9 and 10. Names of coral taxa are abbreviated at the top: Sc= Sychnoelasma, Az == Amplexizaphrentis, l'! Cy = Cyathaxonia, Ac = Amplexocarinia, Lo = Lophophyllum, :\ .' Vs= Vesiculophyllum, Si. o = Siphonodendron oculinum, St. b = 'j, 11; Stelechophyllum banffense, St. m = Stelechophyllum micrum, Mi. e == I.\ Michelinia expansa, Sr= Syringopora (Morphogroup A, B, C, or D). 'i I \ I A diagonally half-filled rectangle with a number in it represents the number of specimens in excess of 20 from that 20-foot interval. A partly I Iii I'.I filled rectangle represents, by the part filled, the proportion of 20 speci 'I I I, I mens from that 20-foot interval. Total numbers of specimens and per .I I centages of taxa are shown at the far right. i. 1:' ,· ii: :•.I:·'.·!l I I, i ! l .• ~:; !S ..... !ii- 100,...____ r--+--;---- ...... C " ;:,: - u~.. \!i!"'+mD!:o(Spfc;1""" ... ~5-36'11. Sc• 148-20'11. c, • 148-20'11, Ai• 109· 1'"' Sr9• 21 • !' St.A• 1'4· 2"4 Si o• II· 2'11...... g. '% SrC• C • ,!'Ii. Ac• 2 • .2'11, St.m•m I - .1, ~--c1s,,.;-. ~ -20 ...... "' ..':! 20 zo 20 20 20 20 20 20 20 20 ABlMDANC[ .. 78 Figure 14. Occurrence and abundance of coral taxa in well core from NDGS Well No. 6230 and the relationship of corals to depositional environments. Explanation of the numbers and symbols shown are the same as those for Figure 13. .. l' 11 Hsk,,.~-~~ .... ~~...... c.~ ··--;y,;·-.,,,,. NDGS NO. 6230 LIND NO. 2-13-20 SWINE SEC.13, T. 145 N.,R. 98 W. NONOISS£P1MENT£D RUGOSA DI SSE Pl MEN TED COLON I AL "'A MCKENZIE COUNTI RUGOSA RUGOSA •· BULATA OEP. (9,760'!!emrK8) 0 Sc Az Cy Lo Vs 51.b St.m Mi.e Sr. B ENV. tr a! ..J llr: l,J '~ ~ :::J Total Number of Specimens c( I llr: Vs = 206- 51% 1.&I Ai 106- 26% Sc 41 - 10% r iii Cy 20- 5% a: 0 -,~ Mi.e= 14 - 3% ;:: ff o:- Lo = 12 - 3°4 ;f SrB = 2 - 5% St.m= 2 - .5°4 -sz > o Z St.b = I - .3% _uCl) c( 404 Oz <( 0 ~-Cl) Cl) :i ~ = Number of Specimens L...illllllllll wer 20 f "'I I I --.I______. z~ I j I- 20 20 20 20 20 20 20 20 20 ABUNOAt-CE •. 80 Figure 15. Occurrence and abundance of coral taxa in well core from NDGS Well No. 505 and the relationship of corals to depositional environments. Explanation of the numbers and symbols shown are the JI l same as those in Figure 13. :,r .'. .. r,,:;;;;;-:.;;i;;'""'.~. NDGS NO. 505 DVORAK F32 6P SE/NE SEC. 6, T.141 N.,R.94 W. NONDISSEPIMENTED RUGOSA TABULATA DUNN COUNTY (8,796' Below KB) 0 Sc A z C Sr. B • Ii: f :;I '001 I I I I 1 ~ Total Nl.lllber of Specimens ~1 Vs = 42 - 35% -f- Az = 30- 25% f- - 4' IX O Sc = 27 - 23% If ~ ::i~ Cy = 17 - 14% - ~ 4'Ck: Sr.8 = 2 - 2% z 4' ~a ~u~ Mi.a= I- 1% ii5 z U) 12001 119 ~~~ I' I I I ~ ~ ::E Iii: If I ~h,681 . . . I I . I I · · I · ~ ( 9, 164'Below KB) feet 20 20 20 20 20 20 ABUNDANCE •. 82 Figure 16. Occurrence and abundance of coral taxa in well core from NDGS Well No. 511 and the relationship of corals to depositional environments. Explanation of the numbers and symbols shown are the same as those for Figure 13. ;J 1i! " 11·:I •)! Iii 11:.,. !!I ;j! I!,, i I t1; ;1 ,i: , 11 !I;'. II ,. 11It ii IP .- 1i:!,· ' i i I r1: .. ,. ...,_,.,.·~~,.,,~-Yl',t.lf.,<,~~~·~~.,.,,..,~~~-;_ ,,'_.,,..1"'.,..'.:;':"'>:~','""'~~P'!":~~~~~~; ~~~!YL}i~,i!4,..;&~!i.• r:!_ff.q;ljlJ4W'l$ 3d M_!f;l.;:ifjfl.~~:r. NOGS NO. 511 JACOBS NO. I F-14-24 P SW/SW 58:.24,T.I: ~w. -OISSEPIIIENTto RUGOSA t.U HETTINGER COU RUr.l'I A '-~:'------TABULATA CV. (7,615' II 0 Sc Az Cy Lo v, Sl.m Ml.I Sr.A Sr.B Sr.C ON. ;:-i ....~ ·. ~i ~··-· • • 4 ir ~1 I \ I \ J \ J J \ I\ J \ J \ J\ J 100 I I \ I \ I I \ I \ I \ I \ I \ 7 \ I I \ I \ I \ I \ I \ I \ I \ "I \ I \ V V V \ \ V \ \ I\ /, /\ /\ I' /, I\ I, I /, I \ \ I \ I \ I \ I \ I \ I \ I \ I \ ,~ \ \ I \ \ ..J I \ I \ I \ I \ I '\ 7 \ I \ Total Number of Specimena ~ I 0: I ' I \ :1 \ I \ I \ / l Vs • 42 - 40"4 I ' I ' 7 ' Az • 23 - 22 "4 ~;: Sc•21-20"4 ! 0: = _, '= Sr.B• 5- 5"4 !~~~ ' , , Sr.A• 4 - 4 % z ..J ' / '' , ' ' / " " oz -c Cy•4-4% Cl) 0 St.m• 2- 2% Oz- >- 0: X X X X X X X X X X [X -c -c ... Ml.t• 1- 1% :II u §1:w- ~ lo•l-1% GI Sr.C •_I_- I % ~f I IZiil I04 !!! :II I I ~ ~ ~1..-v, ~ :; I I F.: I.~.~..b.4 ! • -- z • I ·.·4 ~ ... • 4 en •bo, ..J I I j:: 4- ..·.·. • (8,IIO'llelow KB I 1111 20 20 20 20 20 20 20 20 20 20 ABUNDANCE ~·· ...... +~:;. 1 ;m·~,;:...-.;,...;.~·---· '""""'~m,.., ··~-~~::.•. ~::::-,.~:-"':o.,--,'---':='.?=..,-.--:.:!!.::.~-_::·;:::::::- -C, •. 84 I , II Figure 17. Occurrence and abundance of coral taxa in well core from NDGS Well No. 480 and the relationship of corals to depositional environments. Explanation of the numbers and symbols shown are the same as those for Figure 13. .- ; •·¢~J..• ~. -. .,1 ft; NDGS NO. 480 JENS KVAM N0.4 NE/SW SEC. 29,T.156N.,R. 95 W. TABULATA DEP. ~ WILLIAMS COU~TY ,,vvv.J.-. ,,uvv.J,.. E'filV, (8,466 Below KB l Si.o St.b Sr.A Sr. B Sr.c . ~~ -wif I U> IL ~~ Toltol Number of Specimens a: ...J Vs = 230 - 56 % 5~ Az = 90 - 22 % Sc=44-11% Si.o = 20 - 5 % Sr.B = II - 3 % St b = 5 - 1% Sr A= 4 - 1% Sr.c = 3 - .7 % Ac I .2% 408 ~ = Number of Specimens 1.....111111111 over 20 (8,749 1 Below KB) 283 feet 20 20 20 20 20 20 20 20 20 ABUNDANCE I 1'. :: \: Ii ! 86 Figure 18. Occurrence and abundance of coral taxa in well core from NDGS Well No. 1350 and the relationship of corals to depositional environments. Explanation of the numbers and symbols shown are the same as those for Figure 13. .. 9~<,~.,' NDGS NO. 1350 BRENNA LACEY UNIT NO. I NE/NE SEC. l,T.15 II. NONDISSEPIMENTED RUGOSA TABUlATA OEP. MCKENZIE COUN ENI/. (S.866''Below KB 0 Sc Az C lo Ill St. b Ml.e Sr. A Sr. B 100 • KJlol Number of Specinww Vs •92-50% Sc • 48-26% -' Cy • 30- 16% -I- ~ Az • 8 - 4% Ir Ir St.b• 2- 1% LIi - 0..."" I- Ir z Sr.A• 2 - I % Sr.B • I • .5% !. z 0 Mi.e • I • .5% >- ""0 z z lo • I • .5% 0 4' 185 Ill u 0 ~~ z l&J 4' ~ • Number of ::IE Q :J: U) !!! L.illllllll Sptcimens ow« 20 u,m i IE IL (9,~Bel 20 20 20 20 20 20 20 20 20 ABUNDANCE .. 88 i ~ 1! 'r t. lt I i Figure 19. Occurrence and abundance of coral taxa in well core from NDGS Well No. 52 7 and the relationship of corals to depositional environments. Explanation of the numbers and symbols shown are the same as those for Figure 13. .· NOGS NO. 527 ROUGH CREEK UNIT NO. I NW/NE SEC.13 l6W. NONOISSEPIMENTOl ~SSEPIMENTE~ COLONIAL RUGOSA RUGOSA RUGOSA TABULATA DEP. MC KENZIE COi ENV. Sc Az Cy Vs Si.o St.b Mi.e Sr. A Sr. B Sr. c (9,683 - - 0 Ii: ~ if ~ -..J ~ a: rz ~ I I--=- ....ii. ... >-- ... - -- a 100 ~ - ac ~ >-- ~ +::"= Cl,- ~ ~~, = - .::...:.. Tolol Number of Specimens -...... Vs : 79 - 56% Q: ..... AJ. • 21- 15% ..!...!. - :. 200 rT"1 Cy • 20- 14% :r - SrB• 7- 5% ct z -N:. ~~ ... . Sc•G-4% zz .... Sr.c= 3- 2% ~~ ... St b • 2 - I% lt! Si.o : I - .7% ci z ct 0 :;t8 Mi.e : I - .7 % .:E- > ~ en Q: Sr.A:...... l...:. .7% en .... ~ 141 .:tz"' I ~ 300 I ~ :J ~ ct 1\---/ I I\ ; \. / I\ ;i\ / I\ / I\ I i'\ / I\ / I\ / ....Q: '\;I :r ·v en V V vv V V \/ V a, ~ /\ /\ /\ /\ /\ /\ /\ /\ l\ /\ IL V X "°° ~- I (10,107 fNI ~ Bl """ 20 20 20 20 20 20 20 20 20 20 ABUNDANCE •. 90 Figure 20. Occurrence and abundance of coral taxa in well core from NDGS Well No. 607 and the relationship of corals to depositional environments. Explanation of the numbers and symbols shown are the same as those for Figure 13. ,, 'it' ; t J l .- ------'""~--,,,.?,.< .,_-..,v;,~~ ,;;~· ..l1l,: NDGS N0.6D7 KENNEDY F - 32 -24P NONOISSEPIMEHTED RUGOSA DISSEPIMENTED 149N.,R.93W. RUGOSA TABULATA DEP. ENV. ~,:~cN~T. Sc At Cy Lo V1 Ml.I Sr. A Sr. B (8,927 Below KB 0 Sr.c Sr. D _j Ir - [><:::_ S><:. ><.. ~- >< ~ ~ ~ ><: ::::< C><'~.. :I ~.·.. , iS ~ -~G~ 100 I I ~ ~~ 4 fi.. :.r. ~.·, Total Nurroe< of Specimens .... el ·. •, Vs • 165 - 42% ....• I Sc • 111 - 28% 200 .... ·.•, Cy • 48 - 12 % .. At • 34 - 9 % •···· 5'8• 16 - 4% a.•·.·.·. Sr.A• 5 • I% a.ii•, La•5-1% - ·.·! Sr.D • 3 - .7% 5'.C • 2 • .5% -I- i~ \: Mie • I - .3% z I>: 0 ~ § 500 518 I ~ (9,44 i'Bolow kBl IHI 20 20 20 20 20 20 ABUNDANCE 1 .. iii iiii r=- ·t t575 ...... T ·· mce±rr id lirf.... •. -- ittf#)I...J ..---··111111:v 'a ..'"·11111?111·11, ______.._, <---- ...... ------_,_ ..... i I i t 92 f ! ';: I I I l' \ ! Figure 21. Occurrence and abundance of coral taxa in well core from NDGS Well No. 38 and the relationship of corals to depositional environments. Explanation of the numbers and symbols shown are the same as those for Figure 13. .. NDGS NO. 38 BLANCHE THOM PSON NO. I NON01SSEPIME1'TEO SW/SE SEC.31,T. 160N.,R82W. RUGO~A Dl~!~~D"-.._ ~~~tL _/ TABULATA ~P. NTY BOTTINEAU COU Sc Az Lo v, St.m Mi.t Sr. B ENV. (4,071' Below KB) 0 ,'f'} r; l'J -I- ~·~ a: ~' ! --- ...J 100 I ~~,.. ..., ~ RI'•"- -I- a: i--- f W; ~ - ' "" ...J 400 ~ w~ I- = ~ ::= ~ I- I I >== "'...J ~ I I :3i::: - ~~ >< - • • -~ • a I I ...... - I = 555 §§ (4,626 ' Btfow KBl ftet I 1 20 20 20iii 20 20 20 20 ABUNDANCE .- 94 environments N and V predominated. In response to the overall, regressive sequence in the Mission Canyon, diversity and numbers of corals decrease vertically, as well, except in the west where more open marine conditions prevailed. The lower Charles Formation (Ratcliffe interval) contains a sparse coral fauna; and by the time of deposition of the upper Charles (Poplar interval), the environment was too inhospitable for the existence of corals. Environments in which the Lodgepole Formation (Bottineau interval) was deposited appear to have been less favorable for corals than environ ments of the Miss ion Canyon. Evidence for this is based on a small number of specimens observed in cores (NDGS Well Nos. 607, 274, 38, and 2172) from the Bottineau interval. These specimens belong to the genera Vesiculophyllum, Cyathaxonia, Amplexocarinia, and Amplexi zaphrentis. Vesiculophyllum and morphogroups B and C of Syringopora seem to have had a broader environmental tolerance than other coral taxa occurring in depositional environments II through V (Figs. 13-21); this may have resulted in their longer geologic ranges. Sychnoelasma and Amplexi zaphrentis were slightly more sensitive to marine conditions as shown by their less frequent occurrence in depositional environments II and III .- (Figs. 13-21). Michelinia expansa, Cyathaxonia, Amplexocarinia, Lophophyllum and morphogroups A and D of Syringopora were confined 95 to depositional environments N and V and did not extend into shallower marine environments (Figs. 13-21). Stelechophyllum banffense and Siphonodendron oculinum occurred in slightly shallower marine environ ments (III) but occurred more frequently in more open-marine environ ments (IV and V). Stelechophyllum micrum had a broad environmental tolerance and occurred in depositional environments II, N, and V (Figs. 13, 14, 16, and 21) . Most of the coral fauna showed a greater abundance in more open-marine environments (N and V); this is especially apparent with the coral taxa Ves iculophyllum, Sychnoelasma, and Amplexizaphrentis (Figs. 13-21). Coral diversity also seemed to ' increase in more open-marine environments (IV and V). Greater i abundance and diversity of corals in more open-marine environments l (N and V) indicated that this type of environment was most conducive to coral growth. Coral Zonules After the distribution of the coral fauna was plotted and analyzed in relation to stratigraphic position (Pls. 1-3), a composite range chart was constructed for the Madison coral taxa of the Williston Basin in North Dakota (Fig. 22). The ranges do not represent the total regional range of any particular taxon but, instead, show local ranges observed within North Dakota. These ranges are believed to be fairly accurate for .· North Dakota; but, because core coverage was incomplete at some levels ii_,, ! II i I. I' i t 96 ii I' Ii I I Figure 22. Composite ranges of coral taxa and proposed coral zonules defined by ranges of diagnostic taxa within the Mission Canyon Formation and the lower part of the Charles Formation in the North Dakota part of the Williston Basin. When these local zonules and the ranges of locally non-diagnostic corals are compared with the scheme (Sando and Bamber, 1979) of interregional zonation, the age relationships of Madison marker-defined intervals can be inferred, as given here. i ' '1 : : ! : j I : ·' ''i 1-·"'i:. I 11 ( ! .. -,.···--~.·~·~~""'II":·~~~?'"'.'·":~;~~~~'~"~·~~!/$' MISSISSIPPIAN SYSTEM KINDERHOOK I AN SERIES .... 0SAGEAN SERIES MERAMECIAN SERIES ( PART) MADISON GROUP LODGEPOLE FORMATION I MISSION CANYON FORMATION I CHARLES ( PART) BOTTINEAU INTERVAL ITII...SlOO INTERVAL I FROBISHER- ALIDA INTERVAL !RATCLIFFE INTERVAL I SltJ/echophy/11.111 lllichslinio - Cyofhoxonio Sl b Siphonodendron OCtJlinum zonu le I micrum ronu/11 zonu/11 zonultl : ~ I i I Siphonodflf1dron oc11/in11m I ll' i I SIBIBchopl/ylt.!_m bonffBnSB g I "- I MichBlinia BXpansa ~ I ...<: Cyalhaxonia I I 'S- i St!t.cllopl,yl/um 'micrum ft I I I ~ :, I Syc/moBlasmo I ~ 'g I AmplBXirophrBnlls I I I i Vt1siscu/ophyllum I b' SJ ingopoio I I ~' I Amplexocor/nla il' I .,:, I ~ I lopl,ophyllum I I I •. 98 (Bottineau and upper Ratcliffe intervals), it is conceivable that ranges of some coral taxa might be extended. Four coral zonules are proposed for the Williston Basin of North Dakota (Figs. 5 and 22). Although the North American Stratigraphic Code (North American Commission on Stratigraphic Nomenclature, 1983) does not recognize local biostratigraphic units called zonule s, their use in this study seems useful and appropriate for correlation purposes within such a restricted area as the North Dakota part of the Williston Basin. The usage of the biostratigraphic unit called a zonule in this study follows the definition of Gary et al. (1972, p. 805) as "a locally recognizable biostratigraphic unit such as in a sedimentary basin or similarly restricted area of sedimentation." The four coral zonules proposed are (in ascending order) the Stelechophyllum micrum zonule, the Michelinia-Cyathaxonia zonule, the Stelechophyllum banffense zonule, and the Siphonodendron oculinum zonule. This local zonation scheme was developed for a number of different reasons: (1) Ranges of some of the coral taxa are not as exten sive as those recognized on a regional level. (2) Some of the coral taxa that define the coral-zone boundaries of Sando et al. (1969) and Sando and Bamber (1979) are not present in the Williston Basin of North Dakota. (3) The biostratigraphic units are smaller than the regional coral zones recognized by Sando et al. (1969) and Sando and Bamber (1979) and thus might be more useful in evaluating marker-defined intervals. (4) 99 Stelechophyllum micrum, a diagnostic coral taxon, has not been recorded previously in the United States. (5) Stelechophyllum banffense, another diagnostic coral taxon, had not been reported definitely (Sando, 1983, p. 13) in the conterminous United States prior to the current study. The Stelechophyllum micrum zonule is the lowest coral biostrati graphic unit recognized in this study. The upper boundary of the zonule is defined by the highest occurrence of Stelechophyllum micrum. The lower boundary is not as well defined and is tentatively placed at the Tilston-Bottineau contact. This biostratigraphic unit probably correlates with the Lithostrotionella micra zone of southwestern Alberta proposed by Nelson (19 60, Fig. S); however, the unit is considered a zonule here because it is not known to have the regional extent of the zonation scheme developed by Sando and Bamber (in press). The next succeeding biostratigraphic unit above the Stelechophyllum micrum zonule is the Michelinia-Cyathaxonia zonule. The upper boundary is defined by the highest occurrence of Michelinia or Cyathaxonia, whichever is higher stratigraphically. Cyathaxonia and Michelinia apparently had slightly different tolerances to certain conditions within the marine environment; and, as a result, their upper ranges do not always coincide. The lower boundary of this zonule is defined by the highest occurrence of Stelechophyllum micrum. However, .. this does not imply that the lower boundary of the Michelinia-Cyathaxonia zonule represents the lowest occurrence of Cyathaxonia or Michelinia. ___ ...... ______.. __ _,______ 100 In fact, Cyathaxonia was observed to occur in the Bottineau interval whereas Michelinia is found at least as low as the base of the Stelechophyllum micrum zonule. The Stelechophyllum banffense zonule overlies the Michelinia-Cyathaxonia zonule. Stelechophyllum banffense is an excellent biostratigraphic marker because it has a very short strati graphic range (15-20 feet) and frequently occurs in cores from wells west of the Nesson anticline. The upper boundary of the zonule is placed at the highest occurrence of Stelechophyllum banffense. The lower boundary is placed at the top of the Michelinia-Cyathaxonia zonule. The Siphonodendron oculinum zonule is the highest biostratigraphic unit considered here. The upper boundary of this zonule is placed at the highest occurrence of Siphonodendron oculinum. The lower boundary is defined as the top of the Stelechophyllum banffense zonule. During the time of deposition of the lower Mission Canyon, marine conditions were less restricted than later, and coral bio stratigraphic units can be recognized farther to the ea st and south. The Stelechophyllum micrum zonule extends as far east as Bottineau County (NDGS Well No. 38), where submarine banks developed, in depositional environment Vb, and as far south as Hettinger County (NDGS No. 511), where intertidal shoals developed, in depositional environment IIb. In the west (NDGS .. Well Nos. 7207 and 6230), Stelechophyllum micrum occurred in the ~ f open-marine conditions of depositional environments IV and V. ! __...__. , -. ____ .. ... ,..... __ . _____ .... ______--- 101 Cyathaxonia and Michelinia, which define the upper boundary of the Michelinia-Cyathaxonia zonule, were confined to more open-marine conditions (depositional environments N and V). These environments extended into the area of Bottineau County (NDGS Well No. 38) and into Hettinger County (NDGS Well No. S 11). In the eastern part of the study area during the time of deposition of the upper Mission Canyon and lower Charles, the environments tended to be governed by shallower water and more restricted circulation; only the most environmentally tolerant coral taxa such as Vesiculophyllum, morphogroups B and C of Syringopora, Sychnoelasma, and Amplexi zaphrentis could survive. The more environmentally sensitive corals, such as Stelechophyllum banffense and Siphonodendron oculinum, which are used to define the upper two zonule s, could not tolerate such conditions. Stelechophyllum banffense appears to be confined to an area west of the Ne sson anticline in Golden Valley, Billings, Dunn, McKenzie, and Williams Counties. East of this area, environments were too unfavorable for Stelechophyllum banffense to survive. Siphonodendron oculinum has an area of distribution similar to that of Stelechophyllum ,. ' banffense; and Siphonodendron oculinum is confined to an area west of the Nesson anticline in Divide, Williams, McKenzie, and Billings Counties. However, Siphonodendron oculinum appears to be slightly .- more restricted in its occurrence to the north and west than Stelecho- phyllum banffense. This slightly reduced area of distribution of .• 102 Siphonodendron oculinum is in response to the continued regression of the sea to the west during the time of deposition of the upper Mission Canyon and lower Charles. From the distribution of Stelechophyllum banffense and Siphonoden dron oculinum it appears that the Nesson anticline, or some paleotopo graphic ridge following the same trend, provided a barrier that caused restriction of marine conditions to the east by the time of the deposition of the upper part of the Mission Canyon. The effect of this suggested barrier was not as prevalent during lower and middle Mission Canyon time as shown by the greater areal distribution of Cyathaxonia, Michelinia expansa, and Stelechophyllum micrum. The top of the Michelinia-Cyathaxonia zonule seems to mark the onset of increased restriction of the sea. Age Determinations of Madison Intervals As defined regionally by Sando et al. (19 69) and Sando and Bamber (19 79), the Osagean-Meramecian boundary is generally placed at the lowest occurrence of Siphonodendron oculinum. In the Williston Basin of North Dakota, the lowest occurrence of.§.. oculinum was usually observed in the upper part of the Frobisher-Alida (Fig. 22). In NDGS Well No. 4419 the first occurrence of§.. oculinum occurred within four feet of the highest occurrence of Stelecbophyllum banffense. Because the strati .- graphic position of the last occurrence of§.. banffense seemed to be at a 103 more consistent level than the lowest occurrence of Siphonodendron oculinum (Pls. 1, 2, and 3) and the last occurrence and first occurrence, respectively, of the taxa seemed to be nearly contiguous, the Osagean-Meramecian boundary was placed at the last occurrence of Stelechophyllum banffense. This placement of the boundary is reasonable since the regional range of.§_. banffense was reported by Sando (1983) to be lower to middle Vi sean. The Kinderhookian-Osagean boundary is more difficult to place in this study due to incomplete core coverage and poor coral fauna of the Bottineau interval in the Williston Basin of North Dakota. Moreover, there is general uncertainty on a regional scale on the placement of the Kinderhookian-Osagean boundary. However, the Kinderhookian-Osagean boundary in the United States is generally placed (Sando and Bamber, in press) at the lowest occurrence of Stelechophyllum microstylum (not found in this study), Michelinia expansa, and, in most instances, the first appearances of Sychnoelasma and Vesiculophyllum. In North Dakota the lowest occurrence of Vesiculophyllum and Amplexi zaphrentis was well below that of the other taxa. Therefore, in this study the Kinderhookian-Osagean boundary was questionably placed at the lowest occurrence of Vesiculophyllum and Amplexizaphrentis found in the upper part of the Bottineau interval (Fig. 22) in NDGS Well Nos. 274 and 38. ,· Only a few specimens from two genera, Amplexocarinia and Cyathaxonia, were found at the base of the Bottineau interval (or base 1:_·' 104 of the Lodgepole Formation and Madison Group) in NDGS Well No. 60 7. Both of these genera commonly occur together in subzone Ib of Sando and Bamber (in press) in very similar lithology (Paine member of the Lodgepole Formation in Montana), it seemed likely that the base of the Bottineau interval in North Dakota corresponds to subzone Ib and is late Kinderhookian in age (Fig. 5). The top of the Bottineau occurs just below the lowest observed occurrence of Stelechophyllum micrum in NDGS Well Nos. 38, 7207, 6230, and 511 indicating a lower Osagean age for the top of the Bottineau. From this information, the Bottineau interval in North Dakota can be considered to be of late Kinderhookian and early Osagean age. The Stelechophyllum micrum Zone (Nelson, 19 60, p. 111) in south western Alberta was reported (Macqueen et al., 1972, p. 18) to contain foraminiferids of Zone 8 (Mamet and Skipp, 1970) considered (e.g. Sando and Bamber, in press) to be middle Osagean in age. The range of Stelechophyllum micrum in North Dakota occurs within the Tilston inter val; and, therefore, an age of middle Osagean for the Tilston interval, as determined in this study, seems to fit with the interregional coral and foraminiferal zonation. The Frobisher-Alida interval contains an Osagean coral fauna characterized by Michelinia expansa and Cyathaxonia below the lowest .. occurrence of the phaceloid lithostrotionoid coral Siphonodendron oculinum. Because the worldwide distribution of phaceloid 105 lithostrotionoid corals usually make their first appearance in the Meramecian (William J. Sando, verbal communication, 1984) and the lowest occurrence of Siphonodendron oculinum is commonly taken as the base of the Meramecian in North America (Sando et al., 1969, p. E-7 and E-21; Sando and Bamber, in press), it seems likely that the lower part of the Frobisher-Alida interval is late Osagean in age and the upper· part of the Frobisher-Alida interval is early Meramecian in age. The continued occurrence of Siphonodendron oculinum into the lower half of the Ratcliffe indicates an early Meramecian age for the Ratcliffe interval in the Williston Basin of North Dakota. Evaluation of Time Parallelism of Madison Marker-Defined Intervals The top of the Stelechophyllum banffense zonule is drawn at the last occurrence of Stelechophyllum banffense. Cores from six wells in cross-section A-A' (Pl. 1) contained Stelechophyllum banffense (NDGS Well Nos. 5258, 4419, 4455, 7446, 7104, and 6230). This species has a very short range, usually not more than 15-2 0 feet, and, therefore, is an excellent paleontologic marker. The stratigraphic position of Stelechophyllum banffense in these six cores is remarkably constant, occurring within 20 feet of the position of a well-defined gamma-ray deflection known (David M. Petty, verbal communication, 1983) as the .. "Fryburg Marker." 106 The top of the Stelechophyllum banffense zonule, even though in different lithologies (from depositional environments III and IV), parallels the Frobisher-Alida top; this suggests that the top of the interval is essentially a time plane. Stelechophyllum banffense was found in three cores from wells along cross-section B-B' (Pl. 2), NDGS Well Nos. 480, 1350, and 527. Specimens of Stelechophyllum banffense occur at approximately the same stratigraphic level in all these cores, even though in different lithologie s (from depositional environments N and V). Similar to the situation in cross-section A-A', the occurrence of Stelechophyllum banffense as shown in cross-section B-B', parallels the top of the Frobisher-Alida interval. The base of the Siphonodendron oculinum zonule, which is stratigraphically contiguous with the top of the Stelechophyllum banffense zonule, occurs in NDGS Well No. 1024 (Pl. 3, cross-section C-C') at the same stratigraphic position in the Frobisher-Alida interval as in the other cross-sections. The top of the Michelinia-Cyathaxonia zonule is drawn at the highest occurrence of Michelinia expansa or Cyathaxonia, whichever is higher stratigraphically. Michelinia expansa and Cyathaxonia occur in four cores from wells along cross-section A-A' (NDGS Well Nos. 7207, 6230, 505, and 511). The highest occurrence of either Michelinia expansa or Cyathaxonia (and hence the top of the Michelinia-Cyathaxonia .. zonule) occurs at approximately the same stratigraphic position in different lithologies (from depositional environments IV and V) within the 107 Frobisher-Alida interval. This last occurrence of Michelinia expansa and Cyathaxonia is 50-60 feet below the occurrence of Stelechophyllum banffense and provides further indication that the marker-defined intervals are time-parallel. The top of the Michelinia-Cyathaxonia zonule along cross-section B-B' (NDGS Well Nos. 13 50, 52 7, and 60 7) has a very consistent stratigraphic position in different lithologies (from deposi tional environments IV and V), within the Frobisher-Alida interval and, as in cross-section A-A', it occurs 50-60 feet below the Stelechophyllum banffen se zonule. The top of the Stelechophyllum micrum zonule is drawn at the highest occurrence of Stelechophyllum micrum. This species occurs in the Tilston interval in cores from three wells (NDGS We 11 Nos. 72 0 7, 6230, and S 11; cross-section A-A') in dramatically different lithologies formed in very different depositional environments (viz. , II, IV, and V); and the highest occurrence of Stelechophyllum micrum (and hence the top of the zonule) parallels the top of the Tilston interval. It seems from the coral biostratigraphic data plotted on the three cross-sections that the four coral zonules have consistent stratigraphic positions within the Madison marker-defined intervals and that their boundaries, across various lithologies, parallel these marker-defined intervals. Assuming that the zonule boundaries represent time planes and with this documentation that they parallel the "marker horizons" or .. tops of marker-defined intervals, it seems reasonable that the 108 marker-defined intervals in the Madison of the Williston Basin of North Dakota are time-parallel. Coral Provinces This study records the first occurrence of Stelechophyllum micrum in the United States and the first definite occurrence of Stelechophyllum banffense in the conterminous United States. The occurrence of both of these species in southwestern Alberta indicates a connection between the Rundle depositional complex of Alberta and the upper Madison depositional complex of North Dakota. A shallow-water shelf may have existed during the late Osagean along the outer margin of the cratonic platform (Fig. 4) from Alberta to North Dakota and may have provided an optimum environment for the growth of Stelechophyllum micrum and Stelechophyllum banffense. Off shore from this shallow-water part of the shelf, slightly deeper, marine waters may have been responsible for a less favorable environment for these species. This slightly deeper marine setting is envisioned for most of Montana, during the middle and late Osagean, where both of these species are absent. The boundary between the Central We stem Interior coral sub province of southwestern Alberta and the Southern Western Interior coral subprovince of western United States was drawn (Fig. 7) at the position of the international boundary (Sando et al., 1977, p. 179-181, 183). .- Results of this study show that the coral fauna of North Dakota is very .. 109 similar to that of southwestern Alberta; therefore, the boundary separating the South Western Interior subprovince from the Central Western Interior I coral subprovince might be shifted southward to include North Dakota in the Central We stern Interior coral subprovince. Use of Coral Zones for Subsurface Exploration Although Madison, marker-defined intervals are quite easily recognized in the eastern part of the Williston Basin of North Dakota, this is not the case in the western part of the basin where the Bottineau, Tilston, and Frobisher-Alida interval boundaries are very hard, if not impossible, to identify (Carlson and Anderson, 1966, p. 3-4; Himebaugh, 1979, p. 3). The Ratcliffe and Poplar intervals, however, are still easily recognized in the western portion of the basin. The most obvious reason that the lower intervals cannot be traced clearly into the we stern portion of the basin is that the "normal" lithologies producing the log responses of the boundary markers in the east do not always exist in the western part of the basin. Both Elliott (1982, p. 138) and I noted that the lithologies producing the log responses of the markers consist of very fine elastic material disseminated in anhydritic-dolomudstone or mud stone or of thin shale partings and that these lithologies always seem to be associated with other lithologies of shallow-water environments (patterned dolomites and peloidal-algal-oncolitic wackestones). This .. fine elastic material may have been eroded from the craton to the east, 110 during the culmination of each regressive cycle, to be deposited a short distance offshore; it probably did not extend beyond the intertidal environment. Shallower marine environments did not extend as far west during lower Madison time and, as a result, the marker lithologies are not present to the west in North Dakota. During late Madison time, the shallow-marine environments and associated marker lithologies extended farther to the west. Thus a problem arises when one tries to carry the lower Madison intervals beyond the limit of the defining log markers in the western part of the state. One approach would be to assume uniform thickness for Madison intervals and make interval-boundary picks in the west, accordingly. However, this is not a valid approach because thicknesses of carbonate sequences can vary greatly. The best approach to correla tion in the western area is with biostratigraphic data. The coral zonules proposed in this study provide an accurate and easy method of correlation beyond the limit of the defining log markers. For example, in NDGS Well No. 7207 the Tilston interval is difficult to pick on the gamma-ray log curve (Pl. 1, cross-section A-A'). The occurrence of Stelechophyllum micrum in this core (which in other cores in the eastern part of the study area has been shown to occur exclusively in the Tilston interval) allows for a more certain stratigraphic placement for the Tilston interval in .. NDGS Well No. 7207. The occurrence of Stelechophyllum micrum in this core provides direct age correlations to cores in the east (NDGS Well • 111 Nos. 6230, 511, and 38) where different lithologies from depositional environments II and N occur. Thus, a paleogeographic map could also be constructed for the western half of North Dakota, during the time of the Stelechophyllum micrum zonule, showing intertidal deposits in the east and more open-marine deposits in the west. A less complete paleogeographic map would result if one used the upper Tilston marker horizon as a time datum, because it seldom carries into the more open-marine depositional environments in the basin center. The occurrence of the Michelinia-Cyathaxonia zonule in cores from wells in the west (NDGS Well Nos. 7207, 6230, 1350, and 52 7) and from the east (NDGS Well Nos. 505, 511, and 607) can be correlated within lower Mission Canyon strata where gamma-ray deflections on logs are indistinct and not useful for correlation purposes. Suggestions for Future Work Coral biostratigraphic work needs to be continued in the Saskatchewan, Manitoba, and Montana portions of the Williston Basin ,, to determine if the coral zonules developed in this study of North Dakota ,. ' i strata can be extended into these other areas. Biostratigraphic studies !··1··'" ,.i ' of foraminiferids in the Mississippian of the Williston Basin might be useful in delineating foraminiferal zones in the more shoreward deposi tional environments (intertidal-r.estricted marine). Age relationships of .- Madison intervals as determined by corals in the study might be tested ______..... __ ...... ------·-·----··· 112 with the ages determined by conodonts or by foraminiferids. A combined zonation scheme utilizing both corals and foraminiferids may lead to fine ~,, biostratigraphic zones with broader application in the Williston Basin. Biostratigraphic studies of brachiopods in the Bottineau interval in the Williston Basin of North Dakota might be meaningful as brachiopods are the most abundant fossils in the Bottineau interval. A petrologic and biostratigraphic study of core at or near the boundary between the Madison Group and Big Snowy Group in the Williston Basin is needed to settle the ongoing controversy over whether the contact between the Madison Group and Big Snowy Group is conformable or unconformable. A study of the marker horizons producing the gamma-ray deflections of the Madison intervals of the Williston Basin is needed. The primary concerns of the study should be mineralogic composition and distribution of the marker horizons. .. ------~-·----- i I CONCLUSIONS 1) Examination of cores from the Madison Group of 29 wells in the Williston Basin of North Dakota revealed a coral fauna, of relatively low diversity, which comprises eleven species and four morphogroups of the following genera: Cyathaxonia, Amplexocarinia, Amplexizaphrentis, Sychnoelasma, Vesiculophyllum, Lophophyllum, Siphonodendron, Stelechophyllum, Michelinia, and Syringopora. 2) Ninety-two percent of the coral specimens belong to species of four genera. Forty-five percent of the coral fauna consists of Vesiculophyllum, 18 percent of Sychnoelasma, 17 percent of Amplexizaphrentis, and 12 percent of Cyathaxonia; the remaining 8 percent of the coral fauna con sists of Syringopora ,- Siphonodendron, Stelechophyllum, Michelinia, Lophophyllum, and Amplexocarinia. 3) Four coral zonules are proposed for the Williston Basin of North Dakota; in ascending order they are: the Stelechophyllum micrum zonule, the Michelinia :-Cyathaxonia zonule, the Stelechophyllum banffense zonule, and the Siphonodendron oculinum zonule. Zonule boundaries are defined by ranges of these diagnostic zonule taxa. .- 113 114 4) Diagnostic zonule index corals were found in different lithologie s reflecting several depositional environments, and the zonules were found to parallel log markers within Madison marker-defined intervals as well as interval boundaries. This supports previous suggestions that the marker-defined intervals are para-time-rock units in North Dakota. 5) Five lithologic suites {I-V) and two lithologic subsuites in each of three of these suites were recognized in the Miss ion Canyon and lower Charles Formations in the Williston Basin of North Dakota. These 1 ithologic suites and subsuites are interpreted to represent the following depositional environments and subenvironments: (I) Supratidal-Intertidal environment with sabkha, tidal flat and evaporitic ponds, and lagoons; (II) Intertidal environment which can, in some instances, be differenti- ated into one of two subenvironments--IIa, low-energy accumulations of tidal ponds, drowned tidal flats, and possibly lagoons, or IIb, higher-energy accumulations of shoals and tidal channels; (III) Restricted marine environment; (IV) Transitional zone differentiated into two sub- environments--IVa, a transitional zone between the restricted marine environment and an open-marine environment, or IVb, a transitional zone between the intertidal environment and an open-marine environment; and (V) Open-marine environment differentiated into two subenvironment s--Va, low-energy open-marine environment, and Vb, higher energy open-marine .. environment representing off shore shoals or submarine banks. 115 6) Three, regressive, carbonate cycles are recognized; these correspond to the Tilston, Frobisher-Alida, and Ratcliffe intervals. Each cycle shows a similar sequence of lithology beginning at the base of a cycle with rocks deposited under open-marine conditions (V) and followed by rocks deposited in progressively shallower marine environments (IV, III, and II), culminating at the top of a cycle with rocks deposited in intertidal or supratidal environments (II and I). 7) Massive silicification of carbonate sediments was restricted to lithologic suites V, IV, and III of cycles I and II below the Michelinia-Cyathaxonia zonule (i.e. , the lower part of the Frobisher-Alida interval). 8) Coral distribution and abundance were compared to depositional environments and several relationships were observed. Coral abundance and diversity are closely controlled by depth and restriction of water circulation. Coral abundance and diversity decrease eastward, where environments become increasingly more restricted, and upward. Vesiculophyllum and morphogroups B and C of Syringopora were more tolerant of inhospitable marine conditions (represented by lithologic suites II and III deposited in intertidal to restricted marine environ ments) than other coral taxa, and this may account for their longer I ,• geologic ranges. Sychnoelasma and Amplexizaphrentis were slightly more sensitive to marine conditions but also occurred in these 116 environments. Michelinia expansa, Cyathaxonia, Amplexocarinia, and Lophophyllum are confined to lithologic suites N and V representing more open-marine conditions. Stelechophyllum banffense and Siphonodendron oculinum occurred in slightly shallower marine environ ments III and IV but also occurred in more open-marine conditions (V). Stelechophyllum micrum had a broad environmental tolerance and occurs in lithologic suites II, N, and V (representing intertidal to open-marine depositional environments). Most genera of the coral fauna are more abundant in rocks reflecting more open-marine conditions (IV and V) indicating that these environments were most conducive to coral growth. 9) The lower zonules, the Stelechophyllum micrum zonule and the Michelinia-Cyathaxonia zonule, extended farther to the ea st and south than the succeeding Stelechophyllum banffense and Siphonodendron oculinum zonules. These later, zonule-index taxa migrated westward and northward during the regression of the Madison sea and are confined to an area west of the Nesson Anticline. The Nesson Anticline, or a paleotopographic ridge following the same trend, may have provided a barrier that reduced the coral faunas in the east during later Madison time. The top of the, Michelinia-Cyathaxonia zonule marks the beg inning of this change in coral distribution. 10) This study forms the first record of the occurrence of Stelechophyllum •' micrum in the United States and the first definite occurrence of ------,----~--'" 117 Stelechophyllum banffense in the conterminous United States. Both of these species occur in southwestern Alberta. A shallow-water shelf may have connected the Rundle depositional complex in southwestern Alberta with the Madison depositional complex in North Dakota. The absence of these corals in Montana may be due to slightly deeper marine conditions there. The Central We stern Interior coral subprovince of Sando et al. (1975) might be extended from its previous confinement north of the international boundary to include North Dakota in the Central Western Interior subprovince. ! 11) Coral biostratigraphic data indicate that the Bottineau interval is late Kinderhookian to early Osagean in age. The Tilston interval is middle Osagean in age. The lower part of the Frobisher-Alida interval I J,f is late Osagean in age, and the upper part of the Frobisher-Alida is early Meramecian in age. The Ratcliffe interval is also early Meramecian in age. The Osagean-Meramecian boundary in the Williston Basin of North Dakota is placed at the highest occurrence of Stelechophyllurn banffense. The Kinderhookian-Osagean boundary is questionably placed at the lowest occurrence of Vesiculophyllum and Amplexizaphrentis. 12) Lower Madison marker-defined intervals are difficult, if not impossible, to separate on purely physical evidence in western North •' 118 Dakota. In this area the gamma-ray deflections on logs of this part of the column are indistinct and unsuitable for correlation purposes. But in western North Dakota the Stelechophyllum micrum zonule and the Michelinia-Cyathaxonia zonule in the position of the lower Mission t Canyon can be recognized and utilized for correlation purposes. f i 13) In summary, easily identifiable corals have been found to be powerful tools for correlation of Madison strata beyond the we stern I limits of log, marker horizons. The corals can be used to date Madison strata and they also add biostratigraphic documentation to the concept that Madison marker-defined intervals parallel time planes. >' SYSTEMATIC PALEONTOLOGY Phylum Coelenterata Fry and Leukart, 184 7 Subphylum Cnidaria Hatschek, 1888 Class Anthozoa Ehrenberg, 1834 Subclass Rugosa Milne-Edwards and Haime, 1850 Order Staurida Verrill, 18 65 Suborder Metriophyllina Spasskiy, 19 65 Family Cyathaxoniidae Milne-Edwards and Haime, 1850 Genus Cyathaxonia Michelin, 184 7 Cyathocarinia Soshkina, 1928, p. 376. ~species. -- Cyathaxonia cornu Milne-Edwards and Haime, 1850. Diagnosis. -- Small, ceratoid to cylindrical rugose corals. Cylindrical columella developed independently of major septa but in contact with them. Minor septa long, contratingent, inserted between major septa. Tabulae declined abaxially. No dissepiments. Septa may be tubercu lated. (From Sando and Bamber, in press; and Hill, 1981, p. F 18 6.) I 119 1 ------·--·-·-·-----·-·=-··· 120 Discussion. -- Sando (19 77b) emended the genus to include tuberculated forms referred to Cyathocarinia Soshk ina, 192 8. In the same paper he was the first to document coiling in the protocoralla of some specimens of Cyathaxonia tantilla. He interpreted the coiling to be evidence for a pseudoplanktic mode of life, at least in the brephic stage, and suggested attachment to floating algae. He attributed the wide geographic distribu- tion and occurrence of this species in unfavorable environments as a result of this pseudoplanktic habit. Sando (19 60b, p. 168; 19 78, Plate 1) reported only a small number of specimens of Cyathaxonia from the Madison, and these were primarily from the Lodgepole Limestone. In the present study, Cyathaxonia was found to be a major constituent of the coral fauna. Cyathaxonia sp. Pl. 8, figs. 1-4 Although the Williston Basin specimens seem to compare favorably (in size and number of septa) with Cyathaxonia tantilla (Miller) des cribed by Sando (19 77b, p. 55), tuberculated septa were not always observed. Without an ontogenetic study of these specimens I hesitate to assign them to C. tantilla. Specimens of Cyathaxonia in the Williston Basin of North Dakota are 3 to 4. 5 mm in diameter. A longitudinal section of one specimen measured 10 mm in length and was ceratoid. Specimens with a diameter 121 between 3. 5 mm and 4. 5 mm possess 34 to 3 6 septa. Septa are usually tuberculated. Major septa are in contact with columella. Occurrence. -- Only a few specimens of Cyathaxonia sp. were observed in the Bottineau interval in NDGS Well No. 607, at 10,495 to 10,503 ? feet below KB, and NDGS Well No. 2172, at 10,125 feet below KB. Cyathaxonia sp. is abundant in the lower Mission Canyon (Tilston and lower Frobisher-Alida intervals). At least 12 percent of the total number of specimens from North Dakota belong to this genus. Family Laccophyllidae Grabau, 1928 Subfamily Amplexocariniinae Soshkina, 1928 Genus Amplexocarinia Soshkina, 1928 Amplexicarinia Lang, Smith and Thomas, 1940, p. 16. 1Y.P..§. species. -- Amplexocarinia mural is Soshkina, 192 8. Diagnosis. -- Small, ceratoid to cylindrical rugose corals having wide a ulos formed by downturned edges of axial tabulae. Major septa short, touching aulos. Minor septa absent or poorly developed. Within aulos, tabulae horizontal; outside aulos, tabulae sloping downward to periphery. Dissepiments usually absent but present in some species. (From Sando and Bamber, in press.) 122 Discussion. -- Sando and Bamber (in press) considered Amplexocarinia a rare coral with a short stratigraphic range restricted to coral zones IB, IC, and IIA, a time equivalent to the deposition of the lower Lodgepole Formation in Montana. Sando (19 60b, p. 166) found Amplexocarinia only in the Lodgepole in the Williston Basin of Montana. The current study records a higher stratigraphic occurrence of Amplexocarinia; three speci mens were found in the upper Mission Canyon (upper half of the Frobisher-Alida). Amplexocarinia sp. P1. 8 , fig s . 5 - 7 Specimens of Amplexocarinia in the Williston Basin were few and poorly preserved for discrimination of species. No named species of Amplexocarinia have been described from the Mississippian of the Western Interior province (Sando and Bamber, in press). A total of six specimens of Amplexocarinia were found during this study; five specimens that could be measured range from 2. 5 mm to 7. 0 mm in diameter. Specimens with a diameter between 4 mm and 7 mm possess 18 septa. The septa are radially arranged, short, and are axially confluent with a well-developed aulos. Minor septa and dis- sepiments are absent. 123 Occurrence. -- Three specimens were from the lower Bottineau interval in NDGS Well No. 607 at 10,495 to 10,500 feet below KB, and three specimens were from the upper Mission Canyon (upper Frobisher-Alida) in NDGS Well Nos. 480 and 7207, McKenzie and Williams Counties, North Dakota. Suborder Stereolasmatina Hill, 1981 Family Hapsiphyllidae Grabau, 192 8 Subfamily Hapsiphyllinae Grabau, 192 8 Genus Amplexizaphrentis Vaughan, 190 6 Zaphrentites Hudson, 1941, p. 309. Triplophyllites Easton, 1944, p. 35. . ".,•. Enniskillenia Kabakovich, 1962, p. 323. i' IY£.g_ species. -- Zaphrentis curvulence Thompson, 1881. Diagnosis. -- Small, ceratoid or trochoid rugose corals with large cardinal fossula bounded peripherally by lateral septa and axially by wall formed of fused ends of rhopaloid septa from counter quadrants; cardinal fossula usually on concave side, typically expanded adaxially, but may be parallel-sided or axially constricted. Alar pseudofossulae commonly well developed. Septa! plan normally pinnate but in later growth stages septa may be withdrawn from axis and take on radial plan. 124 Minor septa absent or poorly developed. Cardinal septum long in early stages, shortened later. Tabulae arched or flattened axially descending steeply toward periphery. No dis sepiments. (From Sando and Bamber, in press.) Discussion. -- Sando and Bamber (in press) discussed the common occurrence of Amplexizaphrentis throughout the Mississippian of the Western Interior province. Amplexizaphrentis has a similar long range in the Williston Basin of North Dakota. At least 17 percent of the coral fauna consists of specimens of Amplexizaphrentis. Amplexizaphrentis sp. Pl. 8 , fig s • 8 - 10 Because the nominal species of Amplexizaphrentis in the Western Interior province are in need of re study (Sando and Bamber, in press), it seemed inappropriate to make a specific assignment to specimens from the Williston Basin. Typical specimens of Amplexizaphrentis in this study have 15 septa at a diameter of 3 mm, 16 to 20 septa at a diameter between 4 mm and 6 mm and 2 6 to 2 7 septa at a diameter between 7 mm and 9 mm. A "key-hole"-shaped cardinal fossula and alar pseudofossulae are well developed in specimens 3 mm in diameter (probably representing immature specimens) and remain prominent throughout ontogeny of this form. The . ; { 12 5 cardinal septa is long in early growth stages and becomes progressively shorter during ontogeny. Other major septa are pinnate. Minor septa are absent. Occurrence. -- Only a few specimens of Amplexizaphrentis sp. were observed in the upper part of the Bottineau interval in NDGS Well No. 38 at S, 04 S feet below KB and in NDGS Well No. 2 7 4 at 3, 102 feet below KB and 3,305 feet below KB. Amplexizaphrentis sp. is quite common in the Tilston and Frobisher-Alida intervals, and in the lower half of the Ratcliffe interval. Family Zaphrentoididae Schindewolf, 1938 Subfamily Zaphrentoidinae Schindewolf, 1938 Genus Sychnoelasma Lang, Smith and Thomas, 1940 Homalophyllites Easton, 1944, p. 42. ~species. -- Verneuilia urbanowitschi Stuckenberg, 1895. Diagnosis. -- Ceratoid-trochoid, rugose corals with slit-shaped or parallel-sided cardinal fossula on convex side of corallum. Major septa long, radially arranged, fused adaxially to form axial stereozone. Minor septa long, fused with major septa abaxially forming peripheral stereo zone. Tabulae arched upwards. No dissepiments. (From Sando and Bamber, in press.) --·, ,-.---...... __..,------.~---··"----···:- k,. ,, ;i' !·, l\ i ,ii ,. <. },., 12 6 Discussion. -- Sychnoelasma is a common coral in the Mission Canyon Formation and lowermost Charles Formation of North Dakota, comprising 18 percent of the total Madison coral fauna. Sando and Bamber (in press) also found this genus to be one of the most common corals in the Mississippian of the Western Interior province, primarily restricted to coral Zone II. They also mentioned that it occurs in lithofacies deposited in either shallow or deep water. A broad environmental tolerance was also observed for Sychnoelasma in North Dakota, for it occurs with Vesiculophyllum and Syringopora in rocks representing shallow water environments and also with the same genera in rocks representing somewhat deeper water environments. Sychnoelasma sp. Pl. 8, figs. 11-13 A considerable amount of variation in shape of the fossula, development of the axial stereozone and arrangement and shape of the septa was observed in specimens of Sychnoelasma from the Williston Basin of North Dakota. Specimens with a diameter of 6 mm possess 2 6 to 2 7 major septa. Specimens with a diameter between 8 mm and 16 mm possess 29 to 45 major septa. Sychnoelasma usually possesses a parallel-sided fossula but a slight flaring or tapering of the fossula adaxially was noted in some specimens. Different degrees of dilation of major septa in some specimens produced variations in the size and 12 7 shape of the axial stereozone. In some specimens the ends of the major septa swirl slightly at the axis of the corallum. Minor septa are 1/4 to 1/5 as long as major septa and are fused with them to form the peripheral ,,~ stereozone. r In spite of the morphologic differences noted, no consistent pattern that could be construed as species differences was observed; although it is possible that several species are embraced herein, it is more expedient to recognize only a single variable group. Occurrence. -- Several specimens of Sychnoelasma sp. were found at the top of the Bottineau interval near the Bottineau-Tilston contact in NDGS Well No. 6230. Sychnoelasma sp. is rather common in rocks formed in more open-marine environments in the Tilston and Frobisher-Alida inter vals; lower half of the Ratcliffe interval. Suborder Plerophyllina Sokolov, 19 60 Family Lophophyllidae Grabau, 1928 Genus Lophophyllum Milne-Edwards and Haime, 1850 ~species. -- Lophophyllum konincki Milne-Edwards and Haime, 1850. Diagnosis. -- Trochoid, rugose corals with prominent cardinal fossula on convex side of corallum. Columella simple, styliform. Major septa long, extending, or not, to columella with pinnate to radial plan. Minor -_j_ -······------;-...... ~p•J0-4l ·.~ '' 128 septa short. Tabulae arched upward adaxially. Dissepiments absent or poorly developed in mature stage only. (From Sando and Bamber, in press.) Discussion. -- Although the type species of Lophophyllum is in need of further study (Sando and Bamber, in press), specimens in this study are here assigned to this genus pending a complete generic revision. Lophophyllum sp. Pl. 8, figs. 14-16 Because of the taxonomic uncertainty of Lophophyllum and the probability that several species of this genus in the Western Interior province are synonyms (Sando and Bamber, in press), it seemed impracticable to assign the Williston Basin specimens to a particular species of Lophophyllum. Specimens in the Williston Basin have 24 major septa at a diameter of 6 mm, 33 major septa at a diameter of 10 mm and 43 major septa at a diameter of 14 mm. The cardinal fossula is positioned to one side of the plane of bilateral symmetry. Specimens possess a blade-like columella which has its long axis variably oriented within the corallum. Major septa of several specimens appear to swirl toward the columella (Pl. 8, figs. 14 and 16), and are usually· in contact with it. Minor septa are short. Dissepiments are incomplete or absent. r 129 I•· Occurrence. -- Only a few specimens of Lophophyllum sp. were found in f; J lithologies representing more open-marine depositional environments in t f the lower part of the Mission Canyon Formation (Tilston interval and ti:' J' ' lower part of the Frobisher-Alida interval). Suborder Caniniina Wang, 19 50 Family Uraliniidae Dobrolyubova, 19 62 Genus Vesiculophyllum Easton, 1944 Kakwiphyllum Sutherland, 19 54, p. 3 65. ~species. -- Chonophyllum sedaliense White, 1880. Diagnosis. -- Large, cylindrical, rugose corals with numerous major septa that closely approach axis but may be short leaving open area in axial region. Bilateral, palmate, or radial septa! plan. Cardinal septum long or short, that may or may not be in a fossula. Counter septum usually short. Septa ordinarily dilated, confined to axial reg ion in later growth stages. Minor septa absent or short and impersistent. Dissepi mentarium broad, lonsdaleoid; inner zone of regular dissepiments present. Numerous incomplete tabulae steeply inclined adaxially, or bowl-shaped, f}. gradational with dissepiments. (From Sando and Bamber, in press.) ~ I Discussion. -- Sando (1969, p. 301) observed some specimens of j .. .f Vesiculophyllum to have septa that withdraw from the center of the 130 corallum, and he referred to these forms as enygmophylloid variants because of their close morphologic similarity to the genus Enygmophyllum. Vesiculophyllum sp. p 1. 8 / fig S , 17 -19; p 1. 9 I fig S, 1-3 Extreme ontogenetic and individual variation of specimens referred to the genus Vesiculophyllum cause great difficulty in discrimination of species, to the extent that the number of species in the Western Interior province is poorly known (Sando and Bamber, in press). Specimens from the Williston Basin also show extreme morphologic variation and thus were assigned to Vesiculophyllum sp. realizing that several species might be present. Vesiculophyllum is the most abundant coral in the Madison of North Dakota and it makes up 45 percent of the total coral fauna. It ranges throughout most of the Madison in North Dakota and it had a broad environmental tolerance spanning the intertidal to open-marine depositional environments. Vesiculophyllum is the largest Mississippian solitary rugosan in the Williston Ba sin of North Dakota. Specimens have 41 to 52 major septa at a diameter between 12 mm and 30 mm, and 52 to 63 major septa at a diameter between 30 mm and 44 mm. The largest specimen (Pl. 8, figs. 18 and 19) measured 63 mm and possesses 8 7 major septa. Several specimens measured 50 to 130· mm in length and the coralla are cylindrical to slightly ceratoid. Maj or septa are dilated adaxially and some 131 specimens have major septa that withdraw from the axis of the corallum (Pl. 8, fig. 17, enygmophylloid variant). Minor septa were not observed. A cardinal fossula was observed in several specimens with a shortened cardinal septum. The outer zone of dissepiments (considered structurally weak by Sando, 1960b, p. 180) of most specimens has been eroded away. The tabulae of most specimens are incomplete and steeply inclined toward the axis of the corallum (Pl. 9, fig. 3) although in several specimens the tabulae are flattened or somewhat horizontal. Occurrence. -- Only a few specimens of Vesiculophyllum sp. were found in the Bottineau interval in NDGS Well No. 38 at 5,035 to 5,036 feet below KB and in NDGS Well No. 274 at 3,143 feet below KB. Vesiculo phyllum sp. is widespread in the Tilston, Frobisher-Alida, and Ratcliffe intervals. Suborder Lithostrotionina Spasskiy and Kachanov, 1971 Family Lithostrotionidae d' Orbigny, 1852 Subfamily Lithostrotioninae d' Orbigny, 1852 Genus Siphonodendron McCoy, 1849 Cystidendron Schindewolf, 192 7, p. 149. ~species. -- Siphonodendron aggregatum McCoy, 1851. Diagnosis. -- Phaceloid, columella simple, styliform. Major septa commonly long, may extend to the columella. Minor septa short. r ~-, -.,...... --.~--~-··--·----- _._,' ...... ,. __ 132 Tabulae large, tent-shaped, commonly supplemented by outer, smaller, nearly horizontal tabulae. Dissepimentarium regular, continuous, wide in larger species but narrow and discontinuous in small species. (From Sando and Bamber, in press.) Discussion. -- The genus Diphyphyllum is very similar to Siphono dendron with the except ion of having flat tabulae and being noncolumel late. The validity of Diphyphyllum as a distinct genus has been questioned by several workers (Sando and Bamber, in press). Siphonodendron oculinum (Sando, 19 63) Pl. 9, figs. 4-11 Lithostrotion (Siphonodendron) sp. Sando, 1960b, p. 183, pl. 19, figs. 7-12. Lithostrotion (Siphonodendron) oculinum Sando, 1963, p. 1075, p 1. 14 S , fig s . 1 - S . Diagnosis. -- Phaceloid coralla, corallites small, 4 to 6 mm in diameter, possessing 20 to 25 major septa that extend 1/3 to 1/2 radius of the corallite; minor septa present, 1/2 as long as major septa. Columella usually continuous but may be impersistent. Tabulae tent-shaped, strongly deflected near periphery of tabularium; where columella not well developed, tabulae flattened.· Single row of dissepiments present. (Slightly modified and abbreviated, from Sando, 19 63.) f f j_ ------···-- 133 Discussion. -- Several colonies of Siphonodendron oculinum in the Williston Basin of North Dakota had both siphonodendroid and diphyphyl loid corallites in the same corallum; however, s iphonodendroid corallites tended to predominate. Sando (1969b, p. 183; 1963, p. 1075) reported this in his studies as well. Corallites were 4. 5 to 5. 5 mm in diameter with average diameter 5 mm. Corallites that have a diameter of 5 mm possess 19 to 20 major septa and are 1/2 the radius. Minor septa are 1/2 as long as major septa. Columella is bladelike and is impersistent in some corallites. The tabulae are tent-shaped and strongly deflected toward the periphery. In some cases the tabulae are so strongly deflected toward the periphery that they rest upon the underlying tabula. Where this occurs a short horizontal accessory tabula is present and extends from the deflected edge of the tabula to the periphery of the corallite. Occurrence. -- Siphonodendron oculinum, a Meramecian coral, is relatively rare in North Dakota. It is restricted to an area west of the Nesson Anticline in lithologies of more open-marine conditions. Siphonodendron oculinum occurs in the upper half of the Frobisher-Alida interval and lower half of the Ratcliffe interval and forms the basis of a coral zonule. 134 Subfamily Acrocyathinae Hill, 1981 Genus Stelechophyllum Tolmachev, 1933 LithostrotionellaYabeandHayasak:a. Hayasak:a, 1936, p. 61, 62, 64, 65, 67, 68 [part]. Stelechophyllum Tolmachev. Sando, 198 3, p. 9 (see for further synonomy). ~species. -- Stylophyllum venuk:ofi Tolmachev, 1924. Diagnosis. -- Cerioid rugosan, major septa thin, ordinarily extending across tabularium to columella but discontinuous or absent in dissepi mentarium. Minor septa poorly developed or absent. Col umella usually simple axial rod or plate that may be derived from one or more major septa. Tabularium consisting of axial series of tent-shaped, complete tabulae resting one upon the other and a weak: peripheral series of horizontal or inclined concave-upward tabellae. Dissepimentarium lonsdaleoid. (From Sando and Bamber, in press.) Discussion. -- The genus Thysanophyllum is very similar to Stelecho r phyllum but the former lacks a columella or has a poorly developed and impersistent columella and flat or sagging tabulae. The taxonomic validity of Thysanophyllum is uncertain at this time (Sando and Bamber, in press). j ,-.-, --" ,..., ______--- ·------...... ,,, ... J#~ 135 Stelechophyllum banffense (Warren, 192 7) Pl. 10, figs . 1-6 Lithostrotion banffense Warren, 192 7, p. 4 6, pl. 3, figs. 5, 6, pl. 5. Stelechophyllum banffense (Warren). Sando, 198 3, p. 13 (see for further synonomy), pl. 3; pl. 4, figs. l, 2. Diagnosis. -- Corallite diameter 6 to 13 mm, with 19 to 2 6 major septa, variable in length, rarely joining columella or extending into dissepi mentarium. Minor septa very small, poorly developed, or absent. Columella present or poorly developed. Dissepimentarium lonsdaleoid, composed of one to six rows of inflated and variably sized dissepiments; more than one row of dissepiments usually present. Axial tabulae tent-shaped; tabulae strongly deflected downward toward periphery; where columella is poorly developed tabulae are flattened. Peripheral tabellae present or poorly developed. (Slightly modified from Sando, 1983.) Discussion. -- Several colonies of Stelechophyllum banffense in the Williston Bas in of North Dakota had both stelechophylloid and thysano phylloid corallites but stelechophylloid corallite s always seemed to predominate. Corallite diameters were between 6 and 12 mm with an average corallite diameter of 10 m,m. Specimens with a corallite diameter of 10 mm possess 20 to 24 major septa. Major septa rarely - .-.,~ 13 6 extend to the columella. Minor septa are short, poorly developed or absent. The columella is styliform and may be impersistent. In some specimens the columella is entirely absent (Pl. 10, fig. 3). Axial tabulae are tent-shaped. Peripheral tabellae are poorly to well developed. When present, they are slightly concave to straight and deflected downward from the shoulder of the tabulae to the periphery of the corallite. The dissepimentarium is composed of 2 to 5 rows of small to large, inflated dis sepiments. Stelechophyllum banffense is a zonule index coral that can be distinguished from Stelechophyllum micrum, a lower zonule index coral, by its larger sized corallite s (S. banffense has an average corallite diameter of 10 mm, as opposed to.§.. micrum, which has a corallite diameter between 3 and 4 mm), greater number of major septa (§... banffense has 20 to 24 major septa,.§.. micrum has 15 to 16 major septa), and poorly developed or lack of minor septa (minor septa of S. micrum are usually well developed). Stelechophyllum banffense is quite rare and this study records the first definite occurrence of this species in the conterminous United States. The type material of.§.. banffense (Warren) was believed (Nelson, 19 60, p. 119) to have been derived from the lower Mount Head Formation of early Meramecian age. I have placed the boundary of the Meramecian and Osagean in the Willisto::1 Basin at the last occurrence of Stelechophyllum banffense because it appeared to be contiguous with the I A 137 first occurrence of Siphonodendron oculinum (which is regionally where the boundary is placed, Sando et al., 1969; Sando and Bamber, in press) but had a much more consistent stratigraphic position than Siphonodendron oculinum. Armstrong (19 70a, 19 70b, 19 7 5) studied_§_. banffense in Ala ska where it ranges throughout most of the Meramecian. Occurrence. -- Stelechophyllum banffense has a very short stratigraphic range in North Dakota (15-20 feet) and is an excellent biostratigraphic marker. The occurrence of Stelechophyllum banffense in the Mission Canyon of the Williston Basin represents the earliest recorded occurrence of this species in North America. In North Dakota, _§_. banffense is restricted to an area west of the Nesson Anticline and is found in rocks indicative of restricted- to open-marine conditions (III to V). It occurs in the upper half of the Frobisher-Alida interval exclusively, where it forms the basis of the thin_§_. banffense zonule. Occurrences not shown on cross-sections are in NDGS Well No. 4 683 (Golden Valley County), 9,191 feet below KB and in NDGS Well No. 5639 (Dunn County), 9,453 to 9 , 4 7 3 feet below KB. I J 1 I I f .. 138 Stelechophyllum micrum (Kelly, 1942) Pl. 11 , fig s . 1-5 Lithostrotionella micra Kelly, 1942, p. 357, pl. 50, fig. 7. Stelechophyllum micrum (Kelly). Sando, 1983, p. 13 (see for further synonomy). Diagnosis. -- Corallite diameter 2 to 6 mm with 10 to 15 major septa that extend from columella toward dissepimentarium but usually not through it. Minor septa small, poorly developed. Columella commonly well developed. Dis sepimentarium composed of 1 to 2 rows of inflated dissepiments. Axial tabulae tent-shaped. Peripheral tabellae poorly developed. (Slightly modified from Sando, 1983.) Discussion. -- Only five colonies were collected from four wells in this study. Specimens (Pl. 11, fig. 2) in the more open-marine lithologies were smaller (with corallite diameters of 3 to 4 mm), silicified and not as well preserved as the specimen in the shallower intertidal lithology (Pl. 11, figs. l, 3, and 5). Specimens with a corallite diameter of 3 to 4 mm possess 13 major septa. A specimen with a corallite diameter of 5 mm possesses 15 to 16 major septa. Major septa extend from the columella to the dissepimentarium. Minor septa are usually present and are 1/2 to 1/3 as long as· major septa. The columella is usually well developed but may be impersistent. Axial tabulae are tent-shaped, :f' --- I 139 but peripheral tabellae were not observed. Specimens have two rows of inflated dissepiments. l 1 I Stelechophyllum micrum (defines a relatively thin coral zonule in l l . the Tilston interval) differs from Stelechophyllum banffense (defines a . ' thin coral zonule in the upper part of the Frobisher-Alida interval) by t. being smaller having fewer major septa and better developed minor septa. In addition the major septa of_§_. micrum are usually in contact with the columella. This study first records the occurrence of Stelechophyllum micrum in the United States. _§_. micrum has a short stratigraphic range in the Williston Basin of North Dakota but has a broad environmental tolerance; it occurs in peloidal-pseudoolitic packstone or grainstone of the inter- tidal environment (II) and skeletal wacke stone of the somewhat deeper open-marine environment (IV and V). _§_. micrum has been reported from the lower Shunda and upper Pekisko Formations of the Rocky Mountains of southern British Columbia and Alberta (Bamber, 19 66, p. 14) and the Tilston interval of southeastern Saskatchewan (Brindle, 19 60, p. 43). Occurrence. -- Stelechophyllum micrum occurs exclusively in th-e lower J, ~ i' half of the Tilston interval, where it defines the lowest coral zonule ~( } 1 (_§_. micrum zonule) de scribed in this study. I. t I j t J _J r I 140 Subclass Tabulata Milne-Edwards and Haime, 1850 Order Favositida Wedekind, 1937 Suborder Favositina Wedekind, 1937 Superfamily Favositicae Dana, 1847 Family Micheliniidae Waag en and Wentzel, 188 6 Subfamily Micheliniinae Waagen and Wentzel, 1886 Genus Michelinia de Koninck, 1841 Conopoterium Winchell, 18 65, p. 110. ~species. -- Calamopora tennuiseptata Phillips, 183 6. Diagnosis. -- Cerioid tabulate corals of variable corallum shape. Walls pierced by mural pores. Septal spines or ridges present. Tabulae numerous, incomplete, convex. (From Sando and Bamber, in press.) Discussion. -- Some coral students (Lang etal., 1940, p. 85, 103; Easton, 1944, p. 55) treat Michelinia as a junior subjective synonym of Pleurodictyum, whereas others (Nelson, 1962, p. 955; Sando, 1969, p. 311; Hill, 1981, p. 561, 565) consider them as distinct genera. I 1 i agree with the later authors that Michelinia and Pleurodictyum are J { distinct; the major differences between the two genera are the complete i 1 ness of tabulae (Michelinia ~as incomplete tabulae and Pleurodictyum i has complete tabulae) and the shape of the corallum (Michelinia .. '; ' j ------..... -·...... ------'t-'r; ". s 141 commonly has a conical corallum whereas Pleurodictyum has a discoidal corallum). Michelinia expansa (Vvhite, 1880) P 1. 11 , figs . 6-10 Michilinia expansa White, 1880, p. 158, pl. 39, fig. 2a, b [advanced printing]; 1883, p. 158, pl. 39, fig. 2a, b. Pleurodictyum expansum (White) Easton, 1944, p. 55, pl. 13, fig. 9, pl. 17, fig2;EastonandGutschick, 1953, p. 24, pl. I, fig. 6; Nelson, 1962, p. 955, pl. 137, figs. 1-6, t. - figs. la, b, 2a-c. Michelinia expansa (Vvhite) Bowsher, 19 61, pl. 109, fig. 4; Sando, 1969, p. 311, pl. 39, figs. 1-3. Diagnosis. -- Disco~dal to conical coralla; corallites quadragular, pentagonal, hexagonal, or septagonal; most commonly hexagonal; corallite diameter 6 to 12 mm, averaging 7 mm. Tabulae numerous, usually incomplete, flat, sagging, or convex, small and convex along peripheral part of corallite. (Modified from Sando, 1969, p. 311.) Discussion. -- Coralla of Michelinia expansa in the Williston Basin of North Dakota are conical to broadly conical (Pl. 11, fig. 10), and are 30 mm to 98 mm in length from the apex of the corallum to the upper surface of the corallum. Corallite s are usually hexagonal or septagonal J f r • ~ t $ r! 142 and are 5 to 12 mm in diameter. Average corallite diameters are 6 to 7 mm. Tabulae are incomplete and convex along the periphery of the corallite and infundibular in the center of the corallite. Specimens identifed as Michelinia expansa from the Williston Basin of North Dakota were considered to be the same species as the specimen figured and assigned to Michelinia expansa by Bowsher (1961, pl. 109, fig. 4). The presence of this species in older Mississippian rocks (late Kinderhookian to early Osagean in age) of the Southeastern Coral Province indicates that this species had a long geologic range and wide geographic distribution. The stratigraphic range of M. expansa in North Dakota is very similar to the regional range of the species as recognized by Sando and Bamber (in press); however, it may be slightly more abundant strati graphically higher in the section in the Williston Basin than regionally i l l in correlative rock units. i i Occurrence. -- M. expansa occurs with Cyathaxonia in rocks represent I ing more open marine conditions (IV and V) in the Tilston and lower half of the Frobisher-Alida interval. 1 • 143 II Order Auloporida Sokolov, 1947 I Superfamily Syringoporicae de Fromentel, 18 61 I i I Family Syringoporidae de Fromentel, 18 61 i Genus Syringopora Goldfuss, 182 6 Harmodites Fischer von Waldheim, 1828, p. 19. I.Y.P.g_ species. -- Syringopora ramulosa Milne-Edwards and Haime, 1850. Diagnosis. -- Phaceloid tabulates with corallites connected by randomly arranged tubules. Tabulae central or subcentral; corallites nearly same size within single colony; corallites 1.1 to 4. 0 mm in diameter with frequency of 2 to 18 per square centimeter. Septal spines short, sporadically developed. Wall structure lamellar. (Modified from Nelson, 1977, p. 550.) Discussion. -- Sando (1984) recognized seven morphogroups (A to G) in the genus Syringopora. Some of these morphogroups had been pre l viously assigned to different species by various authors and the taxonomy j l 'I is not yet entirely settled. This study adopts the morphogroup concept ' used by Sando (1984). Four of the morphogroups (A to D) occur in the l 1i Williston Basin of North Dakota. ! II •. I J i l ; • ' ...... - j 144 1 ,,§ Syringopora sp. Pl. 12, figs. 1-5 Morphologically, Williston Basin specimens of Syringopora morpho groups A to Dare identical to each other with the exception of having different corallite diameters and different frequency of corallites per square centimeter. Thus it is possible that these morphogroups are one species although they might prove to be ecophenotypes or yet separate species. The morphogroups differentiated by the mean corallite diameter and the mean frequency of corallites per square centimeter are: Morpho group A, diameter 1.1 to 1.8 mm, frequency 8 to 18/cm2; morphogroup B, i ¥ ' diameter 1. 9 to 2. 6 mm, frequency 3 to 14/cm 2; morphogroup C, diameter l 2 .7 to 3.3 mm, frequency 3 to 10/cm2 ; and morphogroup D, diameter l 3. S+ mm, frequency 2 to 14/cm 2 . Coralla are phaceloid to dendroid but they are primarily dendroid (Pl. 12, fig. 3). Corallites are the same size within a single colony. Visceral cavity is axial or subaxial but primarily axial (e.g. Pl. 12, fig. 4). Tabulae are infundibular. Septa! spines are extremely short or absent. Occurrence. -- Syringopora sp. of morphogroup B is the most numerous syringoporoid in the Williston Basin, followed by specimens from morpho groups C, A, and D, in order of decreasing abundance. Specimens of morphogroups B and C range notably higher stratigraphically than do ------·----~--,..-'""!_f.,_H..,£.,•. l 145 specimens from morphogroup A, and slightly higher than representatives ~' of morphogroup D. Individuals of morphogroups A and D also seem to have been more sensitive to marine conditions, as they occur primarily in rocks representing environments IV and V. Morphogroups B and C, on the other hand, had a greater environmental tolerance and occur in rocks that formed in environments II through V. Specimens of Syringopora morphogroup B and of Ves iculophyllum were the only corals to inhabit some of the shallower marine environments. Syringopora (taken as a group of variable forms) is evenly distributed through the Tilston interval, Frobisher-Alida interval and lower half of the Ratcliffe interval, and comprise approximately 4. 5 percent of the total Madison coral fauna. 146 EXPLANATION OF PLATE 8 Figure 1-4 Cyathaxonia sp. l, transverse section, thin section, UND 4200., x 3, Frobisher-Alida interval, NDGS Well No. 720 7 at 9, 691 feet below KB. 2, transverse section, polished core plug, UND 4201., x 4, Frobisher-Alida interval, NDGS Well No. 7207 at 9,735 feet below KB. 3, transverse section, polished core plug, UND 4202., x 4, Frobisher-Alida interval., NDGS Well No. 60 7 at 9,414 feet below KB. 4, transverse section, thin section, UND 4203. , x 4, Frobisher-Alida interval., NDGS Well No. 7207 at 9,756 feet below KB. 5-7 Amplexocarinia sp. S, transverse section, polished slab, UND 4204., x 5.6, Bottineau interval, NDGS Well No. 607 at 10,498 feet below KB. 6, transverse section, thin section, UND 4205., x 4, Frobisher-Alida interval, NDGS Well No. 7207 at 9,586 feet below KB. 7, transverse section, polished core plug, UND 420 6., x 2. 3, Bottineau interval, NDGS Well No. 607 at 10,500 feet below KB. 8-10 Amplexizaphrentis sp. 8, transverse section, thin section, UND 4207., x 3, Frobisher-Alida interval, NDGS Well No. 480 at 8,731 feet below KB. 9, transverse section, polished core 1 piece, UND 420 8. , x 2. S, Ratcliffe interval, NDGS Well No. 2667 at 9,485 feet below KB. 10, transverse section, polished I core plug, UND 4209. , x 4, Frobisher-Alida, NDGS Well No. i 7207 at 9,549 feet below KB. 11-13 Sychnoela sma sp. 11, transverse section, polished core plug, UND 4210., x 2. 8, Ratcliffe interval., NDGS Well No. 2 667 at 9,483 feet below KB. 12, transverse section, thin section, UND 4211., x 3, Frobisher-Alida interval, NDGS Well No. 7207 at 9,526 feet below KB. 13, transverse section, thin section, UND 4212., x 3, Tilston interval, NDGSWell No. 511 at 8,093 feet below KB. 14-16 Lophophyllum sp. 14, transverse section, polished core plug, UND 4213., x 3, Frobisher-Alida interval, NDGS Well No. 1350 at 9,210 feet below KB. 15, transverse section, thin section, UND 4214., x 3, Tilston interval, NDGS Well No. 6230 at 10,102 feet below KB. 16, transverse section, polished core slab, UNb 4215., x 2, Frobisher-Alida interval, NDGS Well No. 607 at 9,378 feet below KB. 147 17-19 Vesiculophyllum sp. 17, transverse section, polished core slab, UND 4216., x l, Ratcliffe interval, NDGS Well No. 7207 at 9,366 feet below KB. 18, transverse section, thin section, UND 4217., x 1, Frobisher-Alida interval, NDGS Well No. 1024 at 7,155 to 7,214 feet below KB. 19, longitudinal section, thin section, UND 4217., x l, same specimen as figure 18. i,, l· ; I ' ' I.! ·Ii. i ' 1 2 •4 0 5 6 7 8 10 11 13 14 15 16 17 t8 19 149 EXPLANATION OF PLATE 9 Figure 1-3 Vesiculophyllum sp. l, transverse section, polished slab, UND 4218. , x 2, Frobisher-Alida interval, NDGS Well No. 60 7 at 9,290 feet below KB. 2, transverse section, thin section, UND 4219., x 2, Frobisher-Alida interval, NDGS Well No. 480 at 8,691 feet below KB. 3, longitudinal section, thin section, UND 4219., x 2, same specimen as figure 2. 4-11 Siphonodendron oculinum (Sando). 4, longitudinal section, thin section, UND 422 0., x 2, Ratcliffe interval, NDGS Well No. 4455 at 9,252 feet below KB. 5, longitudinal section, thin sec tion, UND 4221., x 2, Frobisher-Alida interval, NDGS Well No. 7207 at 9,520 feet below KB. 6, longitudinal section, thin section, UND 4222., x 2, Ratcliffe interval, NDGS Well No. 7207 at 9,394 feet below KB. 7, longitudinal and transverse sections, thiri section, UND 4223., x 2, Ratcliffe interval, NDGS Well No. 2 667 at 9,469 feet below KB. 8, transverse sect ions, thin section, UND 42 2 4. , x 2 , Ratcliffe interval, NDGS Well No. 4455 at 9,251 feet below KB. 9, transverse sections, thin section, UND 4220., x 2, Ratcliffe interval, NDGS Well No. 44 55 at 9,252 feet below KB. 10, longitudinal and transverse sections, thin section, UND 4220., x 2, Ratcliffe interval, NDGS Well No. 4455 at 9,252 feet below KB. 11, trans verse sections, polished core slab, UND 4224., scale as indi cated, Ratcliffe interval, NDGS Well No. 4455 at 9,251 feet below KB. I; ·1 1 2 4 5 6 8 7 9 10 ,, 151 i EXPLANATION OF PLATE 10 Figure 1-6 Stelechophyllum banffense (Warren). l, longitudinal sections, thin section, UND 422 5., x 2, Frobisher-Alida interval, NDGS Well No. 480 at 8, 733 feet below KB. 2, longitudinal section, thin section, UND 4226., x 2, Frobisher-Alida interval, NDGS Well No. 52 58 at 9,330 feet below KB. 3, transverse sections, !' thin section, UND 422 7., x 2, Frobisher-Alida interval, NDGS Well No. 7446 at 9,359 feet below KB. 4, transverse sections, thin section, UND 422 5. , x 2, Frobisher-Alida interval, NDGS Well No. 480 at 8,733 feet below KB. 5, transverse sections, thin section, UND 4226., x 2, Frobisher-Alida interval, NDGS Well No. 52 58 at 9,330 feet below KB. 6, transverse sections, core piece, UND 422 6., x 2, Frobisher-Alida interval, NDGS Well No. 5258 at 9,330 feet below KB. 153 EXPLANATION OF PLATE 11 Figure 1-5 Stelechophyllum micrum (Kelly). 1, transverse sections, thin section, UND 422 8., x 2, Tilston interval, NDGS Well No. S 11 at 8,034 feet below KB. 2, transverse sections, thin section, UND 422 9. , x 2, Tilston interval, NDGS Well No. 62 30 at " 10,135 feet below KB. 3, transverse sections, thin section, u·, i UND 422 8., x 2, Tilston interval, NDGS Well No. S 11 at p 8,034 feet below KB. 4, transverse sections, polished core piece, UND 42 30. , x 2, Tilston interval, NDGS Well No. 3 8 at 4,597 feet below KB. 5, longitudinal sections, thin section, UND 422 8. , x 2, Tilston interval, NDGS Well No. 511 at 8,034 feet below KB. 6-10 Michelinia expansa (White). 6, longitudinal sections, thin section, UND 42 31., x l, Frobisher-Alida interval, NDGS Well No. 62 30 at 9,888 feet below KB. 7, transverse sections, thin section, UND 42 32., x 1, Tilston interval, NDGS Well No. 62 30 at 10, 173 feet below KB. 8, transverse sect ions, polished core slab, UND 42 33. , x 2, Frobisher-Alida, NDGS Well No. 7207 at 9,678 feet below KB. 9, transverse sections, polished core piece, UND 42 34., x 2, Tilston interval, NDGS Well No. 38 at 4,578 feet below KB. 10, longitudinal sections, polished core slab, U ND 42 3 5. , x 2 , Fro bi sher-Alida interval, NDG S Well No. 7207 at 9,683 feet below KB. 10 - 155 EXPLANATION OF PLATE 12 Figure 1-5 Syringopora sp. l, morphogroup B, longitudinal sections, thin section, UND 42 3 6. , x 2, Frobisher-Alida interval, NDGS Well No. 607 at 9,359 feet below KB. 2, morphogroup C, transverse sections, thin section, UND 4237., x 2, Frobisher-Alida inter val, NDGS Well No. 52 7 at 9,951 feet below KB. 3, morpho group D, corallum, core, UND 42 38., x 1/2, Frobisher-Alida interval, NDGSWell No. 4692 at 6,401 feet below KB. 4, mor phogroup D, transverse sections, thin section, UND 4239., x 2, Ratcliffe interval, NDGS Well No. 32 3 5 at 9,125 feet below KB. 5, morphogroup D, longitudinal section, UND 4239., x 2, same specimen as figure 4. iii iii ,.( , I Ij I I I i . li i i 1' I ! 'I APPENDIX NAME AND LOCATION OF WELLS FROM WHICH CORES WERE STUDIED I .. - -- VvELLS U .St:U lN THIS STUDY NDGS Well No. Well Name - Operator Location County 38 California Oil Co. - Blanche Thompson No. 1 SW/SE sec. 31, Bottineau T . 1 60 N . , R. 8 1 W. 274 Phillips Petr. Co. - Olivia Saude No. 1 NW/SE sec. 19, Pierce T. 158 N., R. 74 W. 480 Amerada Petr. Co. - Jens Kvam No. 4 NE/SW sec. 29, Williams T. 156 N., R. 95 W. ,__. Ul 505 Socony Vacuum Oil Co. - Dvorak F 32 6P SE/NE sec. 6, Dunn (X) T. 141 N., R. 94 W. 511 Socony Vacuum Oil Co. - Jacobs No. 1 SW/SW sec. 24, Hettinger F-14-24P T. 134 N. , R. 9 6 W. 527 California Oil Co. - Rough Creek Unit No. 1 NW/NE sec. 13 McKenzie T. 148 N., R. 98 W. 607 Mobile Oil Co. - Kennedy F-32-2 4P SW/NE sec. 24, Dunn T. 149 N., R. 93 W. 939 Lion Oil Co. - Einar Madsen No. 1 SE/NW sec. 27, Bottineau T . 1 63 N. , R. 7 7 W. 1024 Phillips Petr. Co. - Braathen No. 1 NE/NW sec. 29, Divide T . 1 62 N. , R. 9 5 W. ·- -- J------ NDGS Well No. Well Name - Operator Location County 1350 Amerada Petr. Corp. - Brenna - Lacey NE/NE sec. 1 , McKenzie Unit No. 1 T. 152 N . , R. 9 5 W. 1516 Herman Hanson Oil Syndicate - Samuelson SE/SW sec. 32 , McLean No. 1 T. 146 N., R. 82 W. 2172* Amerada Petr. Corp. - D. A. Nelson, Jr. , SW/SW sec. 5, McKenzie No. 1 T. 152 N., R. 94 W. 2 630 Sun Oil Co. - A. Bloom No. 3 NE/SE sec. 3, Burke T . 1 62 N . , R. 9 2 W. I-' (.11 2 667 Texaco Oil Co. - Gov't. Mary Pace #1 SW/NW sec. 14, McKenzie 1.a T. 146 N., R. 101 W. 3235 Sun Oil Co. - State Lease No. I NW/NW sec. 16 Williams T. 156 N., R. 101 W. 3510 Pan. Amer. Petr. Corp. - Calma Dove No. 1 SW/NW sec. 12, Burke T. 161N., R. 94W. i 3932 U.S. Smelting, Ref., & Mining Co. - SW/NW sec. 29, Burke Radenz "A" No. 1 T. 163 N., R. 89 W. 3944 Chandler & Associates Inc. - Hallof No. 1 NE/SW sec. 21, Bottineau T. 163 N. , R. 82 W. 4419 Shell Oil Co. & N. P. Rwy. Co. - Gov 't. SE/SE sec. 14, Billings #44-14 T. 144 N., R. 102 W. f-- ------,,, ·---..... ~ .... -...... _.....__.. ..,.______"~---~-.,~.--- . .,,,,, ·--·---~"-'-"' _.,..,., ·~··,'~"'-~ ~,~ ..t,.,""'-""···...,,,..,,·.~t.\.,..,_,, "-'c'·""-~'""· NDGS Well No. Well Name - Operator Location County 4455 Shell OU Co. - Gov't. #4lx-18 NE/NE sec. 18, Billings T. 143 N., R. 101 W. 4 683* Mule Creek Oil Co. - State - Martin #1-4416 SE/SE sec. 16, Golden Valley T. 139 N., R. 103 W. 4692 Cardinal Petr. Co. - Orrin Lien No. 1-3417 SW/SE sec. 17, Divide T. 1 63 N. , R. 9 5 W. 5247 Chandler & Associates Inc. - Crooks No. 15-25 SW/SE sec. 25, Renville T. 162 N. , R. 84 W. f--' 5258 0) Tiger Oil Co. - Roughrider Federal No. 3-32 SW/NE sec. 32, McKenzie 0 T. 145 N., R. 101 W. 5551 Kissinger Petr. Corp. - Knutson No. 14-1 SE/SW sec. l, Renville T . 163 N . , R. 8 7 W. 5639* Adobe Oil & Gas Corp. - Signalness No. A-1 SE/SE sec. 16, Dunn T. 148 N., R. 96W. 6230 Gulf Energy & Minerals Co. - Lind No. 2-13-2D SW/NE sec. 13, McKenzie T. 145N., R. 98W. 6254 Tom F. Marsh Co. - Clark No. 1 NW/SW sec. 10, Burleigh T. 140 N. , R. 7 6 W. 7104 W. H. Hunt Trust Estate - Rodakowski No. 1 SE/SW sec. 3, Billings T. 142 N., R. 100 W. {. • ·.,...... _~,• M·-••H~c-s,••~ ··---~----.---..,.. ____,~------·---, ...... ~.. ~--~, ,,, .·---- -·-···--···--~---,--. __ ...... ___ ,·-·-- ··-·· ___, ""'··-~~--- ... ~-~~,---~-·-_J NDGS Well No. Well No. - Operator Location County 720 7 Shell Oil Co. - Shell USA 42-2 8-43 SE/NE sec. 28, McKenzie T. 148 N. , R. 104 W. 7446 Tenneco Oil Co. - David USA #1-35 SE/NE sec. 35, Billings T. 142 N., R. 101 W. *Wells not on cross-sect ion. ...... 0) L "' i -~--,,------..... __..... __,..,., _____ ,_____ ....,, -· ·<·-·----· - ., __ _ I T-,,-.,,,.,., vb,.'"''":,-,~'1' ..,.,.,.,,_ ...... :.;.,.·,-, ·------ REFERENCES CITED i I; ! i l l I 1 I .. I I ,-._,™ e1 , 11 --... J Anderson, S. B., Hansen, D. E., and Eastwood, W. P., 1960, Sub surface studies, in Oil fields in the Burke County area, North Dakota: North Dakota Geological Survey Report of Investigations no. 3 6 , p. 1-2 S . Anderson, S. B., and Nelson, L. 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H., 19 60, Revised nomenclature for the Williston Basin: American Association of Petroieum Geologists Bulletin, v. 44, no. 6, p. 959-960. 173 3oshkina, E. D., 192 8, Nizhnepermskie (artinskie) korally zapadnogo sklona severngo urala: Moskov. 0-va, Ispyt. Prir. (Geology), Byull., v. 6, pt. 3/4, p. 337-393. 3tensaas, L. J., and Langenheim, R. L., Jr., 19 60, Rugose corals from the Lower Mississippian Joana Limestone of Nevada: Journal of Paleontology, v. 34, no. l, p. 179-188. ;te·vens, C.H., Dunne, G. L., and Randall, R. G., 1979, California, in The Mississippian and Pennsylvanian (Carboniferous) Systems in the United States: U.S. Geological Survey Professional Paper 1110-M-DD, p. CC10-CC26. :utherland, P. K., 19 54, New genera of Carboniferous tetra corals from western Canada: Geological Magazine, v. 91, no. 5, p. 361-371. , homas, G. E., 1954, The Mississippian of the northeastern Williston Basin: Canadian Mining and Metallurgical Bulletin, v. 503, p. 136-142. 'asilyuk, N. P., Kachanov, Y. E. I., and Pyzh'hanov, I. V., 1970, Paleobiogeographical review of Carboniferous and Permian coelenterates, in Kaljo, D. L., ed., Principles of distribution and sequence of Paleozoic corals i11 tne U.S. S. R.: Moscow Academy of Science, v. 3, Moscow, U.S.S.R., p. 45-60. rarren, P. S., 192 7, Banff area, Alberta: Canada Geological Survey Memoir 153, 94 p. 'hite, C. A., 1883, Contributions to invertebrate paleontology no. 8, fossils from the Carboniferous rocks of the Interior States: U.S. Geological and Geographical Survey of the Territories (Hayden), Twelfth Annual Report, pt. l, p. 155-171. ·uson, J. L., 19 7 5, Carbonate facies in geologic history: New York, Springer-Verlag. egler, P. A. , 19 69, The development of sedimentary bas ins in western and arctic Canada: Alberta Society of Petroleum Geologists, Calgary, Alberta , 8 5 p. . . Plate 3 C • --·-N DGS NO .2630 -~-~16'---"MU;l~es,_ ___ NOGS NO. ____~l''-M"-"'i le~s ____~ D. L. Waters ( 1984) NDGS N0.4692------'-9-~M~il~esc______NDGS NO. I024 11 Miles NDGS NO. 351 o-~---~''--"""'ile~s~- 3932 ORRIN LIEN NO.! - 3417 BRAATHEN NO./ CALMA DOVE NO. I A.1>LOOM NO, 3 RANOENZ "A" NO I SW/ NW SEC. 12, T.161 N., R.94 W NE/SE SEC 3,T.1621't,R.92W SW/ NW SEC 29, T.163N, R.89 W. DIVIDESW/SE COUNTYSEC. 17,T.!63N.,R 95W. NE/ NW SEC. 29, T. 162 N., R. 95 W OIV1DE COUNTY BURKE COUNTY BURKE COUNTY BURKE COUNTY NDGS NO. 55511•---~2~l~M~;~,,~s---~--" KNUTSON NO. 14- \ SE/SW SEC I ,T.163N.,R.87W cl~-----'2£2_M~1~le~s ____ _ SYSTEM ES I - • NDGS NO. 38------'-"'---'M~;~le~s______J RENVILLE COUNTY RATCLIFFE TOP RATCLIFFE TOP BLANCHE THOMPSON NO t PLATE 3. CROSS - SECTION C- C' IN THE SW/SE SEC. 31, T.160 N, R.81 W NDGS NO 5247----"'"~~M~;~le~s---- BOTTINEAU COUNTY MADISON GROUP OF NORTH DAKOTA CROOKS N0.15-25 SW/SE SEC 25,T.162N.,R.84W. RENVILLE COUNTY ? 6100 4600 NOGS NO. 3944 ,s HALLOF NO. I Gamma Roy--,, 6900 <_ NE /SW SEC. 21,T.163 N., R.62 W. ---= BOTTINEAU COUNTY Gomm,~ Gamma Ray:;;, C Gamma Ray_.:, 3900 4200 ~ ~ _J c-:,oo fROB!SHER-ALIOA TOP 0:: '- <( 4700 I D GS NO. 939-•---~3~4c__~M~il~esc_____ .J FROBISHER - ALI DA TOP 1 u E!NAR MADSEN NO. I ------1------_J SE/ SW SEC. 27, T.163 N .,R 77 W. NDGS NO. 274 ~ 4000 BOTTINEAU COUNTY OLIVIA SAUDE NO. I [:3C{······· .~)/{ NW /SE. SEc.·t9, T.158"N., R:74-w. ~~ I { :::~:: •G PIERCE COUNTY 4300 t G ::::::• 3000 uw FROBISHER-ALIDA TOP 'oar v, ..... ·. W6 T ...... ~N ... I 6300 -- ••••••• I ...... Sr.D ... ·.· <( I B -: .: •: 4800 TILSTON TOP n:: I C v, Sl.o v, A, I w T T I I -! • 8, ~ I I I I ' I Sf l I I s, 8 I I I I 3800 4100 I I -'- I .. Sr.B I ~ • 8, I 4400 I' '-'- €E Az l Si.o sr.:...B B,Br,F 3100 .,, f I T T I ' I I I I I G 18, I I I (L I I l, I • a, T.,oo I I I ' :::::, z ' I 7200 I : Sc v, 0 '; I I 'I 0 - I I G I I •R I I • 8, 0::: + J. 3900 I l BOTT!Nhu TOP J. B;Br,F 1: • 8, 4200 I (9 ~ I I 1 SP • 8, z I I -- ~ t I I • 8, I - l I I (f) ' I I "'T z I I I I I ~ __ _!_ __ __ I __ Mi.e Sr.A fTopMi.-Cyzonule) v, (f) <( 1 I -- ' i ± I ____ I_r_r: ______T I u I I' I 5'8 ~ I T I I 3300 I I I I I I I z I I 0 6700 I I ~ (/) I I I- I I (/) 0:: I I I I I :::?:: I I 0: Limestone I I I Surve~ 7-. - I I e:I I I - I I I I I w .L' z z I I ' <( 0 I I N I I w I I I tI I (.!) ' I <( I I I I I I (/) I I I I I 0 I I I I I I I I I I I I ~r I I eB,Br I I I I I I .L' • B,Br I + I •B,Br EXPLANATION I I I ' '' MUI I l I LITHOLOGIC SUITES* CORAL OCCURRENCES I T I I I I a..'4itt. I A h•t "-'· d Presenl thro"g"·"t -~ n , ... rie,uvovmu stoneormudstorie I- "'""' I I J_ occurrence T I ' - - Single I I I I (a) Pe lloidal - algal· oncolit1c -lithoc!ost!c I _N"ot present I I I ., [ill JI wockestone or mudstone I I I' LP I ood % I .L (b) Pisolitic -oolitic - pseudoolitic-pelloldol- At: ~ Amp/11xocarinlo ' I I lithoclostic wockestOM or pocks1Qn11 or Ar : Alrf,/6)graupl! A, B C and D) I I minor onhydnle M/1 ~ MichlJlmlo 8Xp(JflilO ' ' l lo , LtJpt,ophylhJm (o} Burrowed skeletal wockestone or Cy ~ Cyof/JaXl)fl/q N dolowocxesfone S/o ~ Sip/lOfK)def/dn)I) oculinum I e (b) Ske!eto: woc~eslone intedayered with Sib Sf8/oc/Joplyll11m txmfl6n» l Slm 11 SMl«:h<>{:llyllum micrvm pello1dal wocKestor.e OTHER fllSSI LS V lo) Skeletol wockeMor.e or mud!lone • v Single occurrence • (bl Skel01JI prJckestone or grrJinslone % - Presen! thfouohout 8 , Br~ozoon, Sr • 8mchfopod11 Io or b I lilhologic sub,;u1tes, wh€re difh,renliole4 G " GQGI rr;pod!l R 'fiOO ol?oc F • F'O!'am,nilieridt Or--50~100 MILES Plate 2 D. L. Waters ( 1984) B NOGS NO. 3235-----~3~5-"'M~it~esc______NDGS NO. 480------~2~1 _cM~il~es'------NDGS NO. 1350------~'ocO_ _,M,,i,..;le,_,------NDGS NO. 527'------=-28"-"'M"ile,.esc______NDGS NO. 607'------~6~7-~M~ile~,'------NDGS NO. 1516----~5~3'-~M~il"'es'----~ N DGS N0.6 B' 254 STATE NO.! JENS KVAM NO. 4 BRENNA-LACEY UNIT NO.! ROUGH CREEK UNIT NO. I KENNEDY F-32-24P SAMUELSON NO.! CLARK NO. I NW/ NW SEC. 16, T. 156 N., R. tOI W. NE/SW SEC. 29, T. 156 N., R. 95 W. NE/NE SEC. I, T !52 N.,R 95 W. NW I NE SEC. !3, T.148 N., R. 98 W. SW/ NE SEC. 24, T.149 N., R. 93 W. SE/SW SEC. 32,T.146 N., R. 82 W. NW/ SW SEC. 10, T 140 N ., R. 76 w. WILLlAMS COUNTY WILLIAMS COUNTY MCKENZIE COUNTY MCKENZIE COUNTY DUNN COUNTY MCLEAN COUNTY BURLEIGH COUNTY SYSTEM RATCLIFFE TOP RATCLIFFE TOP RATCLIFFE TOP 8300 Gamma Ray Gamma Roy 9600 5700 3700 8900 FROBISHER -ALIDA TOP 8400 9700 5800 ~ 3800 a:: ___ .f..Toprf·Cyzonule)1 __ Mi.e_ I ----- : I z I I I I + ls,s, ? (TopSt.bzonule) _...2_ -'- I I I I I -I as,R 1 Br,R 9500 {> EXPLANATION LITHOLOGIC SUITES* CORAL OCCURRENCES I - Present throughout I Anhydrite, do!omudstone or mudstone - - Single occurrence {al Pe l!oidal • algo!-oncolitic-lithoclastic I - Not present "" 1I wackestone or mudstone l { Ac " Amp/exocorinio and 10300 (b) Pisolitic-oo!it!c-pseudoolitic-pelloidol- Ar =- Arrplexizophrenlis > lith?Clostic wackestone or packstone or Sc = Sychnoelosma ~ gramstone Vs =- Vesiculop/Jyllum ?------~----r----B_O_TT_t_N_E_AU_T_O_P______, NORTH DAKOTA Sr =Sydnqoporo (morphogroupsA,B,C,and O) • m B~rrowed do!~mudstone or mudstone and Mi.e =- MidJellnk; exponso 9600 minor anhydrite lo ::- Lophophyllum (a} Burrowed skeletal wackestone or Cy "Cyat/Jaxonlo ~ Til dolowackestone Sio = Siphonodendron ocu/inum 5,. (bl Skeletal wockestone interloyered with St.b ~ Stelechop//yllum bonffen~ ,:> pelloidal wackestone Sl.m= S/e/echophy!lum micrum OTHER FOSSILS (a) Skeletal wockestone or mudslone • - Single occurrence • V . 9500 (b) Skeletal pockestone or groinstone Present throughout BOTTINEAU TOP I - 8 ~ Bryozoo ns 10400 Sr = Broch iopods la orb I Uthoiogic subsuites,where differentiated G = Gastropods R =Redalgae -,-,- - Upper limit of silicification F = Forominiferids ~·~---, * Explained more ful!y in text 9700 0 50 100 MILES Plate I D. L. Waters ( 1984) A 23 Miles NDGS No. 7207 ------~~=~------NIJGS NO. 2667-~---~~c"e'~----~-9 MI NDGS NO 52581-~-----'--==------NDGS3 Miles N0.4419------~==------NDGS7 Mils NC 4_455------''O'--'Meis'"''------NDGS NO. 7446--~ --7~eMailces~------riDGS NO. 7104>--->2<0~Msisl•ss ____ NDGS NO 6230>------'3<2--'""'1 SHELL USA 42-28-43 =------45 Miles,. A' GOV'T.- MARY PACE NO. I ROIJGHRIDER FEDERAL NO. 3-32 SHELL-N.P-GOV'T NO 44-14 GOV'T. N0.41x-18 TENr.Eco DAVID NO I 35 --- NDGS NO. 505 ----~-NDGS NO. 511 RODAKOWSKI NO. LIND NO. 2-13-2D SE/NE SEC. 28, T.148 N., R. 104 W. DVORAK F32 SP SW/ NW SEC. 14, T 146 N., R 10 I W SW/ NE S~C.32, T. 145 N., R.101 W SE/SE SEC. 14 , T.144 N., A.102 W. NE/NE SEC. 18, T. 143 N., R.10 I W SE/ NE SEC 35, T. 142 r.., R.. 101 W F-14-24P JACOBS NO. I MC KENZIE COUNTY SE /SW SEC. 3,T. !42 N. ,R.100 W SW/ NE SEC 13 ,T. 145 N_, R. 98 W. MCKENZIE COUNTY MCKENZIE COONTY BILLINGS COUNTY BIL.LINGS COUNTY BiLLINGS COUNTY SE/NE SEC 6,T 141 N ,R 94W SW/SW SEC.24,T 134N.,R.96W BILLINGS COUNTY MC KENZ!E COUNTY DUNN COUNTY HETTINGER COUNTY SYSTEM ES 9200 RATCLIFFE WP ______.:~=---f------"'cAT 0c0L010FF0E~T~OP - ~~~~~~c;--~~-1--~~~~~~~~-~~~cc:-~----1~~~~-C _L----"·~~-+--~- RATCLIFFE TOP------~~ Gomma Roy ( = l; 9300- 9100 I 9400-i 7600 9100 90~ 8600-· .},, 9500 ,' Vs Si.o Sr:B ~ l ~ o::: --:-:~~()_l~l~-Tc-- :::: .... Sr.a , ' ' 9100 T ~ (/) I ' ( I 94 ! i 9 9500 : w v, I __J I I Gomm, Roy 0 T 0::: Gomma Roy ' I' I Gommo Roy~ - ' ' - X ' XIX 1- J_ -- X - X -X - X z I __ __ ' _Cy!Top~llCy' zonule~~6' ____ _ r- ' _L' 1 1-- I I I I Sr.8 0 z I N ' I I I I I I T ~ :-x- I TILSTON TOP 1 I 1 1 : < ' I I -' * Explained more fully in text