Gharacteristicsofthe boundary between the Castile and SaladoFormations near the western edge of the Delaware Basin, southeasternNew Mexico by BethM. Madsenand 1mer B. Raup,U.S. Geological Survey, Box 25046, MS-939, Denver, C0 80225 Abstract 1050 posited in the DelawareBasin of southeast New Mexico and west Texasduring Late Per- Permian The contact between the Upper mian (Ochoan)time. In early investigations Castile and Salado Formations throughout and SaladoFormations were un- the Delaware Basin, southeastNew Mexico /-a(run,ouo the Castile differentiated, and the two formations were and west Texas,has been difficult to define EDDY / aou^r" because of facies chanqes from the basin called Castile by Richardson (1904).Cart- center to the western idge. Petrographic wright (1930)divided the sequenceinto the studies of core from a Phillips Petroleum i .,/ upper and lower parts of the Castileon the Company well, drilled in the westernDela- -r---| ,' . NEW MEXTCO basisof lithology and arealdistribution. Lang ware Basin, indicate that there are maior (1935) the name "Saladohalite" Perotf,um introduced mineralogical and textural differences be- ,/ rot company "n for the upper part of the sequence,and he and Salado Formations. / core hole'NM 3170'1 tween the Castile the term Castile for the lower part The Castile is primarilv laminated anhv- retained of the drite with calciteand dolomite.The Salado ( of the sequence.Lang placed the base DELAWARE BASIN Formation is also primarily anhydrite at the SaladoFormation at the base of potassium location of this corehole, but with abundant (polyhalite) mineralization. This proved to layers of magnesite.This magnesiteindi- be an unreliable marker becausethe zone of catesan increaseof magnesiumenrichment mineralization occupies different strati- in the basin brines, which later resulted in graphic positions in different areas. Lang the deposition of magnesium-rich potash (1939)then proposedthat the boundary be- deposits within the SaladoFormation else- TEXAS wliere in the basin. A breccia zone at the top of the Castile Formation shows evi- dence of massive recrystallization, which indicates a break in sedimentationand pos- 50 KILOMETEFS sible subaerial erosion. This breccia zone 0 30 MiL€S Alsoin this issue probably representsan unconformity along the western edge of the basin between the LowerCretaceous strata Castile and SaladoFormations, which has FIGURE 1-Index map showing location of the been recognizedby other workers. Phillips Petroleum Company core hole. Dashed undersouthern High Plains P.6 Iine shows the westem edge of the Delaware Basin. Mineralparagenesis, Introduction structure,and "ore-shoot" ern New Mexico. The core hole, NM 3170- The contact between the Upper Permian geometryat the U.S. Castile and Salado Formations in the center 1, was locatedin the SWt/+SWllqsec.21,T263, of the Delaware Basin of southeast New R25E,(Fig. 1). Coring beganat 108ft below Treasurymine P. 10 contin- Mexico and west Texas has been defined by the surfacein the SaladoFormation, HarryMcAdams State Park P.12 several authors on the basis of maior litho- ued through the CastileFormation, and ter- minated in the underlying Lamar Limestone Abstractsfrom 8th annualMineral logic differences between the two forma- p.17 tions. In the center of the basin, where the Member of the Bell Canyon Formation at a Symposium Salado contains numerous beds of halite and depth of 7,230ft. This core provides a rare Service/News p.20 significant potash deposits, the contact has opportunity to examine the Castile-Salado p.24 A Staffnotes been placed at the base of a prominent an- contact, which is not seen in outcrop. hydrite bed that overlies the thick laminated description of the upper part of the Castile anhydrite sequence of the Castile Formation. Formation, the lower part of the SaladoFor- Gomingsoon Toward the edge of the basin, however, both mation, and the contactbetween the two for- formations are primarily anhydrite, and the mations is presented. Textural and UpperDevonian-Lower Mississippian two contact between the two formations is not mineralogical differences between the conodontbiostratigraPhY formations indicate a significant change in obvious. This paper attempts to define the Scanningelectron microscope study of contact at the west edge of the basin on the the environments of deposition for the two basis of mineralogical and textural differ- formations. authigeniczeolites ences of the anhydrite beds in the two for- Geomorphicdevelopment of CitYof Previous investigations mations observed in one core hole. Rocks,Grant County In 1969 Phillips Petroleum Company drilled The Castileand SaladoFormations are part an exploratory hole for sulfur in southeast- of a marine evaporite sequencethat was de- tween the Castile and Salado Formations dicate that deposition was in fairly deep water, in the center of the Delaware Basin repre- should be at the baseof a prominent anhv- well below wave base. Detailed studies by sentsthe filling of a deep basin with chemical drite marker bed, which hd hter named tlie Dean and Anderson (1978,1982)indicate thit sediments of progressively higher salinity. Fletcher Anhydrite Member of the Salado the salinity of the water in the Delaware Ba- The ratio of anhydrite to calcite(or dolomite) (Lang, 7942).The Fletcher,however, can not sin increased during the deposition of the in laminated beds of the Castile increases be traced throughout the basin and is not Castile Formation. This salinity increase is upward, and halite, which is sparsein the recognizableat the location of this Phillips indicated bv: 1) an increasein the amount of lower Castile,becomes plentiful toward the drill core. anhydrite in the anhydrite-calcite couplets top. The SaladoFormation represents a con- from the base upward, and 2) an increase tinuation of the generalincrease in salinity Geologic setting upward in the number of interbedded halite of brines in the basin; it is primarily halite The evaporitesof the Castileand Salado beds. with significant amounts of sylvite, carnal- Formations were depositedin a basin that The Salado Formation. which overlies the lite, and polyhalite and minor amounts of was initially quite deep. Regionalstudies by anhydrite. Udden (1924),Lang (1935),Adams g9!aj, The core hole described in this report was and King (1947)suggest that the water depth drilled along the western edge of the Dela- at the beginning of Castile deposition was ware Basinwhere the evaporitesare mostly about 500m. Anderson and Kirkland (1966) anhydrite, with somecalcite, dolomite, gyp- and Anderson et al. (1972)showed that very tile and Salado lithologies interfinger in the sum, and magnesite.Figure 2 showsthe lith- thin laminationsin the Castile,which are center of the basin. The work of Lowenstein ologies of the upper part of the Castile composedof distinct coupletsof anhydrite (1982) indicates that the Salado Formation Formation and the lower part of the Salado and calcite (occasionallywith minor dolo- was deposited from very saline brines, un- Formationin the Phillipscore hole. The brec- mite), can be identified and correlatedover der shallow water conditions, with occa- cia zone at the top of the CastileFormation wide areasthroughout the DelawareBasin. sional periods of desiccation. is also shown. Suchwell-preserved delicate laminations in- In summary, the Castile-Salado sequence Petrography Petrographicexamination of thin sections and polished core sections and scanning electron microscopestudies were made of severalsamples collected through the Castile Top ol core and SaladoFormations. Mineral identifica- tion was by x-ray diffraction.A description of the rocks from these studies follows. Salado Formaton Castrle Formallon New AAexnc@ GEOLOGY EXPLANATION . Scienceand Service volume 6 t\\\ 10, No. 1, February lggg \\\ Massrve anhydr le N\ \ \ Edrfor Deborah A Shaw Drafter: RebeccaTitus F\5I Lamrnaled anhydr le Published quarterly by l\\.,.- New Mexico Bureau of Mines and Mineral Resources a division of New Mqico Institute of Mining & Iehnology i-vT; Breccrated anhydrlte BOARD OF REGENTS rL! -al Ex Officio Carry Carruthers, Gooernorof Nru Mexico _l Magnes le Alan Morgan, Supqintendentof Publiclnstruction Appointed Gilbert L Cano, Ples ,1985 1989,Albuquerque Lenton Malry, SeclTreas ,1985-1997, Albuquuque Robert O Anderson, 1987-1993,Roswell "o Donald W Morris, 1983-1989,Los Alamos l Steve Torres, 1967-7997,Socorro New Mexico Institute of Mining & Technology 120 Pr*ident Laurence H Lattman l 400 New Mexico Bureau of Mines & Mineral Resources Director Frank E Kottlowski Depul! Director George S Austin 130- Subscriptions:Issued quarterly, February, May, August, NovembeU subscription price $6 O0/calendaryear Editorialmatter: Articles submitted for publication should 450 be in the editor's hands a ninimum of five (5) months 140.- before date of publication (February, May, August, or November) and should be no longer than 20 typewrit- ten, double-spacedpages All scientific papers will be reviewed by at least two people in the appropriate field of study Address inquiries to Deborah A Shaw, Editor 150: ol Nm MexicoGeolo6y, New Mexico Bureau of Mines & 500 Mineral Resources,Socorro, NM 87801 Publishedas publicdomain, therelore reproducible withouL pet Botlom of core at 1,230 ft mission requested FIGURE 3-Core sample of typical interlaminated Soutcecredit FIqUTE 2-Lithologic column of the upper part anhydrite and calcite of the Castile Formation Ciculqtion: 1,600 of the Phillips PetroleumCompany core hbte 1NU Lighter layers in