Please do not destroy or throw y this publication. If you have no further use for it, write to the Geological S ey at Washington and ask for a frank to return it DEPARTMENT OF THE I NTERIOR Hubert Work, Secretary U. S. GEOLOGICAL SURVE Y George Otis Smith, Director Bulletin 786- A 'J_'l;IE GEOLOGY OF THE INGOl\'IAR ANTICLINE TREASURE AND ROSEBUD COUNTIES : ..../1\"· ·r, ·~~ MONTANA A~:;~\V.; - '. '(;~:;.~ ""-. ', . '·_·-;,\ :2:?-.... , \Y\ V:> ,tleJQ\ .-\, BY t: fU.l. ,.... ;:;:; ~quaw n ~~O · .~ :jr. C. HEALD 066~ S3:1 .,. ( Pages 1- 37) Published October 18, 1926 ~i{r STEPHEN F. AUSTIN ST.~TE UNIVERSITY .55o.co u"'~~c, . ~o.le,~ ; WASHI NGTON GOVERNMENT PRIN'l"l!':G OFI•'ICE 1926 CONTENTS Page Introduction- ---------------------- ---- ------------- --- ------------- - 1 Field work------------ ----------- ---------------------- ---- --- - - 1 Acknowledgments-------- ------------------------------------ --- 1 Publications with a hearing on tlle Ingomar area___________ _______ 1 GeographY----- - ---------------- -------- ---------- ---- --------------- 2 Location - - -------- ----- ----------------------------------------- 2 RoadS------------------------------------------------------ ----- 3 Relief ------------- -------------------------- --- - --- ------------- · 4 I>rainage--- ---------- ------------------ ------------------ ------- 5 \Vater supplY- -------------- - - ----- ---- -- ------------------------ 5 Culture ---- ----------- ----- ----- - ------ ------ --- - - -------------- 6 Fuel ------ ---------- ---------------- - - ------- --- - --------- ------ 6 Stratigraphy-------___________________ -- ---_____ _____ ______ -------___ 6 Rocks exposed- ------------ ------------- ----- ----------------- --- 6 Bearpaw shale- -- --- -----~---------------------- - --- - - ------ 7 Judith Ri-rer fOrmation_________ _________ ________ __________ ___ 10 Upper member------------------ ----- --------------- - - --- 11 Lower memi.Jer___________ ___________ ______________ _______ 13 Possii.Jilities of oil in t11e formation______________ __ _______ 14 Rocks not exposed - -- -- - ------------------- - -- ---------- -- -~- ---- 14 Claggett shale----- -------- --- ----------- - ------------------- 16 Area covered on In ~oma r nnti<:line--- --- - ----- ------------ 16 Correlation----------------------------------------- - ---- 16 Character------- ------- ------------ -------- - ------------ 17 Origin------------------------ - - -------- ---------------- 17 Possible value ns ;;onn·c of oil--------------- - ------------ 18 Eagle sanclstone - ---------------------~ - --- - - --------- -- - --- - 18 Colorado sha~e and I>akota ( ?) sandstone _____ --- ------- ------ 19 Thiclmess and <:haracter of Colorado shale---------------- 20 Origin of Colorado >:hale------------------- --------- ------ 21 I>akota ( ?) sandstone and overlying sa1111y beds__________ __ 21 Kootenai and Morrison ( '! ) formations_________ __ __ __ _________ 23 Sundance or Ellis formation-------------- -------------------- 23 ·Triassic ( ?) rocks--- ----------- -- ----- -------------------- -- 2-! Permian ( ?) strata- - - ----------------- -- ---~ - - -- - --- -- - ----- 2-! Pennsylvanian strata - ------ --- - - ----- ---- ·- -----·--------- ---- 25 Madison limestone ----- ----- ------------·----- - --- ------------ 25 Igneous rocks - - ----- - - - ----- -------------- - - --- -------------------- - 26 Structure------ --------------------------- --------------------- ----- - 27 Position of the crest with depth------------ - --- ------------------ - 28 Faults--------- ------------------------------- - --- -------------- 29 Origin of anticline- --- ----------------- ----------- ---- - ----- ----- 30 Summary statemenL- - -- - ----- ---------- ----- - --------- ---------- 31 III IV CONTENTS Page Review of oil possibilities_______ __ ___ _________________________________ 31 Possible oil-yielding beds----- ------------------- - -------- - ---- -:-- 31 Types of oil -------------- ----- ------------------------- --------- 35 Drilling that has been done on the Ingomar anticline and other folds in this region ---------- ----- ----- ----- - ------- --- - ------------- 35 Possibilities of the region as a whole----- ------------------------ 36 ILLUSTRATIONS Page PLATE 1. Areal geologic map of the Ingomar anticline, Treasure and Rose- bud Counties, MonL---- ----- --- --- - - - ---- ----- - ---- - -- ---- 2 2. Upper beds of the Judith River formation----------------:----- 12 FIGURE 1. Index map showing location of Ingomar anticline, Treasure and Rosebud Counties, Mont_____ __ _______ __ ______________ 3 2. Detail of cross-bedding in the upper part of the Judith River formation --------------------- -------- - - - ------ - - - --- -- - 11 3. Idealized cross section across the Ingomar anticline, Mont____ 27 4. Possible relations between the surface fold and a fold lying in depth on the Ingomar anticline, 1\fonL--- -- ---------- -- 28 5. Sketch showing the general relations along a line drawn north- west through sees. 33 and 29, T. 9 N., R. 35 E., Mont________ 30 QONTRIBtJTIONS- TO EcoNOMIC GEOLOGY,_1926 . PART II. MINERAL FUELS THE 'GEOLOGY OF THE INGOMAR ANTICLINE, TREASURE . AND. ROSEBUD COUNTIES, MON~ANA . By K. c. HEALD_ INTRODUCTION Field w'ork.-The data presented in this report are based on field wor~ by K. C. Heald and W. W. Rubey in October, 1922. Division of . ~apping by -the two observers is indicated on the sinaU diagram· - op.~ l?ri!t~. J •... 'rhe.observers worked singly, determining locations and -altitudes by triangulation. Outcrops. of certain beds were traced continuously, so far as this was possible.1 Geologic structure was de­ ter{!lined by means of numerous observations of altitude on beds of known stratigraphic position, supplemented by dip and strike ob-. '·servations, which; -wherever tb,e. method seemed justified; were made by ·determining relative po'sition and altitude of three points on s~n­ . gle beds with outcrops 10 feet or more in extent. Where maximum dips could not be certainly observed components of the dips were ·.". te~t.ded .and u'sed in determining the structure. · · Acknowledgments.-The writer takes pleasure in acknowledging his indebtedness to the Absaroka Oil & Development Co. fgr infor..: mation furnished through the company's chief geologist, Mr.· A.. A. Ha:m.tp.er, and to Mr. Darwin Harbicht, of Ingomar, whose knowledge .. regarding conditions in the Ingomar region greatly facilitated and - expeditea the geologic work. -·.Publications .with._ a · bea.tring on the Ingomar area.-The only public~tions dealing specifically ~ith the Ingomar area are a short notice issued to the press August 1, 1921, by the United States Ge9logica1 Survey giviiig' the results obtained' in a brief examina­ tion of the Ingomar anticline made in June, 1921, by W. T. Thorn, jr., and C. E. Dobbin, of the Geological Survey; and University oj Montana Bulletin 4, by C. H. Clapp, Arthur Bevan, and. G. S. Lambert, dealing with the geology and oil and gas prospects of cen- 1 The relative stratigraphic position of these beds is indicated on Plate 1 by arbitrarily chosen numbers, No. 1 Indicating the lowest bed, and so on. 1 2 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1~, PAR~ II tral and eastern Montana,· publish~d in June; 1921. The press not~ce was accompanied by the only map showing the geologic structure of the anticline which has, to the wri~r's knowledge, been published. Neither of the papers mentioned describes in detail the stratigraphy of the area. C. F. Bowen, in ·Bulletin 621 of the United States Ge()legical Survey; p~blished in 1916, and also in Professional Paper 125; gave details of stratigraphy observed in the Porcupine dome, a few miles to the east. · Certain stratigraphic details mentioned in Geo­ logical Survey Bulletin 611, "Guidebook of the western United States, Part A," published in 1915, also relate to this region. The descriptions of the Judith River formation and discussions dealing with its character and correlation ~~y with advantage .be read by any geologist who contemplates work in this area, both because the observed details may be of help to him and because he is more likely in turn to observe something that will be a contribution to knowledge regarding the Judith River formation if he -is thoroughly acquainted. with previous ideas regarding its character, correlation, source, and conditions of deposition. Among works of this nature are those cited below : Hatcher, J. B., Relative age of the ;Lance Creek beds of Converse County.' Wyo., the Judith River beds of Montana, and the Belly River beds of Cana-da: Am. Geologist, vol. 31, p. 369, 1903. Stanton, T. W., and Hatcher, J. B., The stratigraphic position of the Judith River beds and their correlation with the Belly Ri>er beds: Science, new ser., vol. 18, p. 212, 1903. Stanton, T. W., and Hatcher, J. B., Geology and paleontology of the Judith River Beds: U. S. Geol. Survey Bull. 257, 1905. Peale, .A. C., On the stratigraphic position and age of the Judith RiYer.. formation: Jour. Geology, vol. 20, pp. 350-649, 640-652, 738-J57, 551-557, ()52-669, 741-761, 1912. Bowen, •c. F., Possibilities of oil in the Porcupine dome, Mont.: U. S. Geol. Survey Bull. 621, pp. 61-70, 1916. Bowen, C. F., Gradntion from continental to. marine conditions of deposi­ tion in central Montana during the Eagle and Judith River epochs: U. S. Geol. Survey Prof. Paper 125, pp. 11-21, 1919. · Hancock, E. '1'., Geology and oil and gas prospects of the Huntley field, Mont.: U. S. Geol. Survey Bull. 711, pp. 10&--148, 1920. GEOGRAPHY Location.-The