. ·::_ .:·~~=-::· ~--~,. ~ . ~:.""";"::.~. '~~~.--. -. ...---- ... :.. ·:- - ..... -:.--.. -- ,-. · .... ................·ATOMIC EN.ERGY COMMISSION PLOWSHARE PROGRAM. .... •.r~' .,1;(-_lc"';_. ~~~~~-. :,.~~­ -.-~:..- -~ ~~-~-'-:.-~~- CARLSBAD. NEW MEXICO . DECEMBER 10-; 1961 o. RaWson' / c~ Boardman. I N .. Jaffe-Chazan LAWRENCE RADIATION LABORATORY. ISSU!I)t APRU. 20, 1965 ._.. .. •' - ., . '!-... ,--.~-7~- .... - ..- ..· , .. Cavity produced by the Gnome explosion and subsequent colla pse. 1·ote figure right-center of rubble for scale. Cavity is 70 feet high and mor than 150 feet across. Photograph by Lawrence Radiation Laboratory. I~ Geologic Studies r'"'~ Project Qnome I Eddy County, New Mexico By LEONARD M. GARB; J~. - . GEOLOGICAL SURVEY PROFESSIONAL PAPER 589 ... Prepared on behalf of the 1"""1 U.S. Atomic Energy Commission •! !""'!~ •' I UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1968 ,..,., I I L-~-~~---·~---------------------- UNITED STATES DEPARTMENT OF THE INTERIOR STEW ART_ L. UDALL, Secretary GEOLOGICAL SURVEY William T. Pecora, Director Librnry or Congress cntalog-card No. GS 68-186 ' : .J For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 CONTENTS Pap Page • ~ ~stract------------------------------------------- 1 Gnome area-Continued ~troduction. _----- __ - ____________________________ _ 1 Properties of the rocks-Continued Purpose of Project Gnome ______ ~ ___ " ___ : _______ _ 1 Minor elements in Salado Formation in the Gnome drift ____________________________ _ Historical summary of the project _______________ _ 2 13 Participation by the U.S. Geological Survey ______ _ 2 Muieralogy and petrography of the Salado For- Purpose of this report" _________________________ _ 3 mation near the device ::hamber ___________ _ 14 Acknowledgments ____ --_------ _________________ _ 3 Halite--------------------------------- 14 ~ Methods of study ______________________________ _ 3 Polyhalite___ - _ --------------- __ ------- 15 Anhydrite ____________________________ _ ~eology.------------------------------------------ 3 15 Regional setting ___ ---- _____________________ ---_ 3 Clastic material--- __ -- ________________ _ 15 Gnome area. _____ - ___ -- _- _______________ - ________ - 4 Effects of the nuclear explosion______________________ _ 16 Effect on the shaft _____________________________ _ ~ Stratigraphy at the site _________________________ _ 5 17 'Effe'ct at the main station _______________________ _ ~ Salado Formation. ______ ----- ___ ---_-- __ ---_ 5 17 The reentry drift. _____________________________ _ Rustler Formation _________________________ _ 7 17 8 Venting---------------------------------------- 17 Dewey Lake Redbeds----------------------- The cavity _____ ------ _________________________ : 17 ~ Gatuna Formation. ________________________ _ 8 1 Explosion-induced structure. ____________________ _ 18 illi Alluvial bolson deposits _____________________ _ 8 Structure in confined salt. __________________ _ 19 - St~cture.------------------------------------- 8 Structure in unconfined salt_________________ _ 19 ,., Geolo~)t of the preshot Gnome drift ______________ _ 9 New minerals formed. _____ ~---- ___ .... ____________ _ 21 1.1 Propertie_!l of the rocks _________________________ _ 11 Elements introduced ___________________________ _ 23 Physical properties. _____ ---________________ _ 11 Detailed description of rocks in the Gnome shaft______ _ 24 _, Changes in physical properties. ___________ - __ _ 13 References _______________________ -·- ______ -.• _______ _ 32 w ILLUSTRATIONS ~ I wJ Page i'LATE 1. :;\Iap and geologic sections of preshot underground workings, Project Gnome, Eddy County, New :\Iexico ___ In pocket 2. :Yiap and geologic sections of postshot underground workings, Project Gnome, Eddy County, New :Ylexico ___ In pocket ~ I \dWGURE 1. Location map of Project Gnome site, Eddy County, N. :..Iex_____________________________________________ 2 2. :Ylap showing extent of the Delaware basin in New Mexico and adjacent structural and geographic features____ 4 3. :\Iap showing location of shaft, ground zero, and U.S. Geological Survey test holes at Project Gnome site_____ 4 fMIIII 4 . Geologic sectiol1-between Carlsbad Caverns N atitmal 'Park>'tmd Projeet Gnome site_________________________ 5 .J 5. Geologic cross section between shaft and cavity, Project Gnome site______________________________________ 6 6. Photograph of units 12, 13, and 14 exposed in preshot drift______________________________________________ 10 7. Sketches of twinned polyhalite crystal forms·--------------------------------------------------------·- 15 ~ Photograph of steam-eroded potholes in unit 10 where shot vented into preshot drift________________________ 1R I 8. Iiiii 9. Map of underground workings and cavity_____________________________________________________________ 18 10. Geologic cross section of drilling alcove, showing thrust faults.------------------------------------------- 19 11. Photographs showing thrust faults, lithification, and brecciation resulting from the Gnome explosion__________ 20 filii! 12. Geologic cross section through buttonhook reentry drift_________________________________________________ 21 ~ 13. Photomicrograph of preshot salt______________________________________________________________________ 21 14. Photomicrographs of intrusive breccia resulting from Gnome explosion____________________________________ 22 15. Photograph of hand specimen showing vein of intrusive breccia------------------------------------------- 23 ~ •' I v "'Il ~ 1111111 ! ~ -fi'IOIII VI CONTENTS TABLES I~J Pare TABLE I. Generalized stratigraphic section of rocks exposed in the Gnome shaft _____________________________________ _ 5 2. Detailed stratigraphic section of Salado Formation along drift from device chamber to shaft_ ________________ _ 9 3. Physical properties of rock samples from Gnome shaft_ _________________________________________________ _ 11 4. Physical properties of rock samples from Gnome shaft, as determined by static method _____________________ _ 12 5. Measured velocities and calculated elastic moduli for rock salt near the position of the Gnome explosion ______ _ 12 6. Physical properties of samples of halite from unit 10, Salado Formation. __________________________________ _ 13 7. Description and stratigraphic position of samples of Salado Formation analyzed by semiquantitative spectro- graphic methods--------------------------------------------------------------------------------- 13 8. Summary of semiquantitative spectrographic analyses of evaporite rocks (Salado Formation) from Gnome drift. 14 9. Approximate size and heavy-mineral composition of clastic material in units 11-13 of the Salado Formation in iJd Gnome drift------------------------------------~----------------------------------------------- 16 10. Semiquantitative spectrographic analysis of insoluble residue of vein material resulting from the Gnome explosion_ 23 fnlili' 1.w i ~ I l""l •I i GEOLOGIC STUDIES, PROJECT GNOME, EDDY COUNTY, NEW MEXICO By LEoNARD M. GARD, JR. ABSTRACT -halite, grades upward into pure halite, and ends with a clay­ bearing halite at the base of the n~rt higher polyhalite. For Project Gnome, part of the Plowshare Program to de­ Comparison of preshot and I)O"tshot velocities in the salt velop peaceful uses for nuclear energy, a nuclear device was near the shotpoint indicated that rock fracturing caused by the detonated December 10, 1961, underground in rock salt of the explosion was detectable trom changes in elastic moduli, but Permian Salado Formation SOU'the!l.St of Carlsbad, N. Mex. compaction was not. No change in density of the rock could The Gi!ological Survey's investigations on behalf of the U.S. be detected. Atomic Energy Commission provided basic geologic and geo­ The explosion formed a cavity nbout 70 feet high and mor~ - physical information needed to dt>:fl.ne preshot and postshot than 150 feet acl'o81l. Postshot mining exploration revealed geo­ geologic and hydrologic conditions at and near the site. Thts logically interesting phenomena that resulted from the explo­ report describes the geology Of the site, some physical and sion. Intrusive breccia veins associated with complex tbru3t chemical properties of the rocks, and the known effects of the faulting were formed adjacent to the cavtt;r. The breccia 1a , nuclear detonation on the rocks at the site. composed of blocks of granulated and plaatically deform4!d salt -~ Geologic strata at the Gnome site consist of e'"aporite and in a matrix at black melted salt. The black color of the matrix clastic rocks of the Salado and Rustler Formations and Dewey is. due to the presence of laurionite, galena, and carbon. These Lake Redbeds, all of Late Permian age, the unconformably materials, not present in tlle preshot rocks, were created by ;'1- -overlying Gatuna Formation of Pleistocene(?) age, and a the shot. Lead from near the device combined with water and t!over of alluvial and eolian sands. I.J All rocks, except where dis­ chlorine from salt to form laurionite and with sulfur from poly· torted by solution collapse, are nearly tlat lying. halite to form galena. The carbon probably was deriT"ed from 1""1 The evaporite deposits are easily dissolved and either are organic material present in the device chamber at shot time. 1 missing at the surface or only partially crop out in southeastern Lateral displacement of an instrument in a drill hole 100 feet ._. New Mexico; thus the sinking of n 1,200-foot shaft