Magnetostratigraphyof a core lrom Raton Basin, NewMexico-implications forsynchroneity of CretaceouslTertiary boundary euents by MichaelA. Payne,EnRaton Formation may be up to 610 m various proposed Cretaceous-Tertiary 30.5-m(100.l-fQ-long core from the Raton (2,001ft) thick (Ash and Tidwell, L976) and boundaries have proven inconclusive. This Basinin New Mexicohas been obtained. contains the Cretaceous-Tertiary (K-T) situation is unfortunate given the extant pa- The core includesthe palynologicallyde- boundary. Fossilsare poorly representedwith leomagnetic/paleontologic documentation terminedCretaceous-Tertiarv boundarv and the exception of paleobotanicmaterials. Leaf available. However, Orth provided accessto aniridium abundanceanomily. The bound- (100.1-ft) ary is shownto lie in a normalpolarity zone, floras are known from the Trinidad Sand- the 30.5-m Raton core, drilled by asverified by hand samplescollected from stone, the Vermejo Formation, and the Raton Los Alamos Laboratorv, with a demon- the basin,thus placingin gravedoubt the Formation (Brown, 1943).Brown (7943,1962) strated iridium anomaly-at the palynologic validity of a synchronousworldwide ex- consideredthe lower 15m (49ft) of the Raton CretaceourTertiary boundary. Addition- tinction event. Formation, containing the problematic plant ally, samples were taken from surface ex- f.ossl Paleoasterinquirenda Knowlton, to be posures near the town of Raton at the Introduction Cretaceousin age and the upper part Paleo- Cretaceous-Tertiary boundary. Fig. 3 is a cene. Tschudy (1973)located the palynolog- generalized representation of the 30.5-m The Raton Basinis a large sedimentary and ical Cretaceous-Tertiarv boundarv at 81 m (100.1-ft)core showing dominant lithologies structural basin in northeast New Mexico and (266 ft) and 88 m (289 it; above the base of and paleomagnetic sampling intervals. southeastColorado 10,000 km, (3,861 mir) in the Raton Formation on the basis of core area (Fig. 1). More than 3,700 m (12,138ft) samples.Tschudy (in Orth and others, 1981) Experimental procedure of sedimentary rocks of Late Cretaceous- reestablishedthe palynological Cretaceous- Eocene age are present in the Raton Basin Cylindrical plug samples were obtained at Tertiary boundary in a newly drilled core and Wood, 1956;Baltz, 1965).The approximately 30-cm intervals from the Los flohnson "within a L m interval between a coal bed Upper Cretaceousand Paleocenerock units, Alamos core (Fig. 3). The well-consolidated centered at a depth of 255.7 m and a car- in ascending order, are the Trinidad Sand- siltstones were cored and sliced wet to 2.5 bonaceous shale at 256.7 m." This palyno- stone, the Vermejo Formation, the Raton cm (1 inch) cylinders. The friable shaleswere Iogical boundary occurs at the same Formation, and the Poison Canyon Forma- sliceddry to fit inside 1.7 x 2 x 2 mm plas- stratigraphic position as an iridium abun- tion; these rock units record the iinal regres- tic containers. Three additional oriented dance anomaly with concentrations of up to sion of the Cretaceousepeiric seaway from sampleswere collected in Raton Park on the 5,000ppt, and it is the first record of an iri- the Westem Interior of North America. west side of Raton, New Mexico. These sam- dium anomaly in continental sediments. ples were between 15 cm below and 57 cm We found it apparent that 1) anomalously above the palynological Cretaceous-Tertiary high concentrations of Ir at the Cretaceous- boundary and iridium abundancezone. Three Tertiary boundary, when combined with specimenswere taken from each sample. Ex- magnetic polarities, might have a far-reach- treme care was taken to maintain vertical up ing value for stratigraphic correlation of geo- for all specimens. graphically widely separated rock units and that 2) the concentrationsmight provide use- ]F ful data for resolving shatigraphic argu- ffi ments regarding the stratigraphy of the San A.F ol @lcrop ol uprrmGl Alsoin this issue: r€loc€ous ond lorer ond m'ddre Juan Basin at or adjacent to the Cretaceous- p. Tertiary Uraniumindustry in NewMexico 45 boundary. Paleontologic/magneto- Bryozoanand crustaceanfrom stratigraphic data were interpreted to indi- p.52 cate that the FruitlandFormation Cretaceous-Tertiary boundary, Redefinitionof Zuni ".nit*€ based on the highest occurrence of din6- p,56 saurs/ occurs within the normal polarity zone Sandstone CoyoteCreek State Park p, 60 correlative with anomaly 29 (Butler and others, p.62 1977;Lindsay and others, 1978;Lindsay and Service/News others, 1981). Thus, dinosaur extinction in Gomingsoon the San ]uan Basin occurred later than ma- rine foraminiferal extinctions at Gubbio, It- BacaFormation glyptosaurine lizard aly, where extinctions occurred high in the Cephalopodaptychifrom Los Moyos FIGLJREl-Location map of study area showing Limestone strucfural boundaries, distribution of Cretaceous reversed magnetozone betwden anomalies and Tertiary rocks, and sampling localities for Ra- 29 and 30 (Alvarez and others, 1977). Five-yearcumulative index to Nenr ton core (LA-YCI) and exposures(RH-L,3, 4; aftet To date, our efforts to locate an iridium Mexico Geology fohnson and others, 1966). anomaly in the San |uan Basin at or near Results The samples from the Raton Basin core were generally very weakly magnetized. NRMs"were typically on the-ordeiof a few '). times 10-'O ^' (10-oA m Demagneti- zation to 20 mT usually decreasedthis by a factor of 2 to 5. In addition, the median de- structive field (MDF) for these samples was relatively low. MDFs were typically less than 20 mT with many of them being lessthan 10 mT. This lowness usually indicates that the primary magnetic carrier is magnetite, as- sumed to be detrital . Fig. 2 is a plot of the inclination of the magnetically cleaned spec- imens as a function of core depth; the mean inclination for eachsample is also plotted. A certain degree of scatter in the paleomag- netic data is apparent. Therefore, a set of criteria was developed after the one men- tioned by Lerbekmo and others (1979). Be- cause the inclination to be expected for a = Cretaceous-Paleocenesample collected from - ^-^ the Raton Basin is about 60', and the incli- a 5fu nations measured for normal-polarity San o |uan Basin sampleswere on the order of 30'- 50" (Lindsay, Butler, and others, 1981),the I range of possible inclinations was divided into three segments: - 90" to - 30' (re- versed), -30o to +30'(indeterminate), and + 30'to * 90"(normal). A samplewas deemed to be of reversed (R) polarity if one or more of its specimenswere reversedand none were normal; or if two were reversed and one were normal; or if there were one specimenin each of the three segments.A samplewas deemed to be indeterminate (I) if all three specimens were indeterminate; or if two were indeter- minate and one were normal; or if two were

. lnlensity > lO-4Am-l o tntensify < lo-4Am-l New A4exnco x Meon of three specimens GEOLOGY o Scioncoand Sorvico Volume 5, No. 3, August 1983 published quarterly by -9O-8O -60 -40 -?O O +20 +4O +60 .80 +90 New Mexico Bureau ofMines and Mineral Resources a division of New Mexico Institute of Mining & Technology Incl inotto n FIGURE 2-Inclination of magnetization for specimens from Raton Basin core as a function of core BOARD OF REGENTS depth. The palynological Cretaceous-Tertiary boundary and iridium abundance zone occurs at 839 Ex Officio a 1; Toney Anaya, Covenor of Ne|| Mexico (Orth and others, 1981).Solid dots represent samples with intensities Breater than L0 A m open Leonard DeLayo, Szperintendenl of Public Inslruction dots represent samples with intensities less than 10 a Am 1. The mean of three specimens yielding Appointed sample inclination is represented by an x. Judy Royd, Prcs., l9?7-1987, Ia Ctuces Willim G. Abbon, Secty/Ireas., 196l-1985, Hobbs Donald W Moris, 1983-1989, /-or Al@os Roben Ir€ Silchez, 1983-1989, Albuqwrque Steve Tores, 1967-1985, Socorro A few of the cylindrical samples were in- microprocessorwas used to make the mag- itially measured on a Schonstedt SSM-I netization measurements.Demagnetiza- New Mexico lnstitute of Mining & Technology Pr5idql ...... LaurenceH.Lattman spinner magnetometer interfaced with a tions were performed using a Schonstedt New Mexico Bureau ofMines & Mineral Resources North Star microcomputer. The specimens GSD-5 tumbling specimenAF demagnetizer. Director . .. FrankE.Kottlowski Geor8,e S. Austitr were demagnetized in 5-mT (milliteslas- At least one specimen from each sample was Deputt Direclot Subscriptiod: lssued quarterly, February, May, August' measurementof magnetic intensity) steps fully stepwise demagnetized in 10 mT steps November; subscription price $6.00/yr. using a home-built alternating-field demag- to at least 40 mT. The natural remanent mag- Editoriol motter Contributions of possible material for netizer.The weaknessof the magnetization netization (NRM) and the magnetization re- consideration in future issues of NMC are welcome. Articles submitted fot publication should be in the ed- precluded demagnetizing beyond 15 mT or, maining after at least one demagnetization itor's hands a minimum of five (5) months before date in some cases,20 mT. Most of the measure- (usually 20 mT) were measured for each of of pub[cation (Februaty, May, August, or Novenber). Address inquiries to Marla D. Adkins-Heljeson, editor of ments and further demagnetizations of the the remaining specimens.Fisher statistics New Mexico Aeobgy, New Mexico Bureau of Mines & specimensinitially measured at New Mexico were then applied to the three specimens Mincral Resources. Socorro. NM 87801 Institute of MiningandTechnology were made from each sample to obtain sample mean di- Published os public domoin, therefore reproducible without at the PaleomagneticsLaboratory at the Uni- rections. Because declinations were arbi- perm ision. Sour@ credi I reques led. Cirulation: l,4N versity of Arizona. An ScT two-axis cry- trary, the declination for each specimen was Prirrer. University ofNew Mexico Printing Plant ogenic magnetometer interfaced with a first converted to zero.

August 1983 NewMexico Geology bv Orth and others (1981)at 839. Not only Tertiary boundary magnetozone may yield : aia tne core data give good, reliable, and pollen.data to support or refute this line of 6 normal inclinations in this interval, but the reasomnS. o?h three hand from Raton Park, New Lerbekmoand others (1979)established that UA samples Mexico yielded well-defined positive incli- Cretaceousdinosaurs in the Red Deer Valley :f I Qfr- e,3 nations, Measured inclinations after clean- of Alberta became extinct within a reversed ft;= ,,,=-;H ing were +73.6o, + 49.0", and + 61.2' (mean polarity zone correlated with the reversed 2&= H[ !a= FEE= of +61.3");+32.9", +39.5", and +67.0'(mean zone between anomalies 29 and 30. This di- gHs5s 3E; =dfr Z of +46.4");and +87.3', -2.0", and +26.5" nosaur extinction was followed within a few -8OO- (meanof +35.0) for the samples25 cm be- meters by a major palynofloral change. Pos- low, 10 cm below, and 75 cm above the paly- sibly terminal Cretaceousextinctions began nological boundary, respectively. Although earlier in the north than in the south where, these samples were oriented in the field on as in the Raton and San fuan Basins, a major a horizontal plane, declinations were lost in palynofloral change does not occur prior to the slicing processas a result of the attempt magnetic anomaly 29. Thus, if the base of 2A (r to maximize specimen volumes. anomaly 29 is accepted as the worldwide 1 We offer the following tentative zonation CretaceourTertiary boundary as suggested t- I assignmentsbased upon palynologicaldata by Lerbekmo and others (1979),or if the Cre- E lrJ and lengths of polarity zones. Our favored taceous-Tertiary boundary is placed some- F interpretation is that the upper normal is what lower, within the 29-30 reversed polarity I zone, the palynofloral change seen in the -830 - anomaly 28, the one between 835 and 852 is anomaly 29, and the one between 865 and Raton Basin and the extinction of the dino- 898 is anomaly 30. The small normal in the saurs in the San ]uan Basin are Paleocene interval 856 and 858 can be correlated to the events. Extinction was not a synchronous -84O- short normals found by Lerbekmo and others worldwide event and catastrophic events at (L979).From this interpretation, the average or near the Cretaceous-Tertiaryboundary as ZJ sedimentation rate between the base of indicated by iridium abundance anomalies anomaly 28 and the base of anomaly 30 (a (Alvarez and others, 1980)did not result in _850_ total of about 2,130 cm) is 6 mm/1,000yrs the extinction of dinosaurs and Cretaceous when correlatedto the Ness and others (1980) floras everywhere. time scale. The uniformity of the average ACKNOWLEDGUTNTS-wewish to thank Carl sedimentation rate for each polarity zone is Orth for providing us accessto the Los Ala- -86O- a remarkable.The rate is 0.5 cm (.20 in), 0.66 mos core and showing us the location of the f cm (.26in), 0.56cm (.22in), and 0.55cm (.22 palynological boundary and iridium abun- o UJ in) per L,000 yrs for the reversed zone be- dance anomaly in Raton Park. We wish to () tween anomalies 28 and 29, anomaly 29, the thank Robert Butler and Everett Lindsav, F reversedzone betweenanomalies 29 and30, University of Arizona, for providing acceis UJ and anomaly 30, respectively.An alternative to facilities under their charge and for E () explanation, though less favored, is that the thoughtful discussions.The views expressed core is entirely within anomaly 29 and would in this paper are our own. ?,r) therefore have a minimum averagesedimen- yrs. In any case, tation rate of 3.8 cm/1.,000 References the average sedimentation rate is indicated Arthur, M. A., Fischer, A. G., Lowrie, W., -890- to be very low. Nvarez,W., . Napoleone, G., PremoliSilva, I., and Roggenthen, W. M., 7977,Upper Cretaceous-Paleocenemagnetic stra- tigraphy of Gubbio, Italy-V. Type section for the Late a Conclusions Cretaceous-Paleocenegeomagnetic reversal time scale: -9OO- . Our results demonstrate that the Creta- GeologicalSociety of America, Bull., v 88, p. 383J89. ceous-Tertiary palynological boundary and Alvatez, L. W., Alvarez, W., Asaro, F., and Michel, H. E Coot V, 1980,Exhaterrestrial cause for the Cretaceous-Ter- an iridium anomaly in the Raton Basin occur tiary extinction: Science,v. 208, p. 1,095-1,108. ffi Snote within a normal polarity zone. Based upon Ash, S. R., and Tidwell, W. D.,1976, Upper Cretaceous the palynology, this normal polarity zone can and Paleocenefloras of the Raton Basin, Colorado and L:::l 5rltslone best be correlated with magnetic anomaly 29 New Mexico: New Mexico Geological Society, Guide- FIGURE3--Generalized lithologic column of Ra- (Ness book 2Tth field conference, p. 197-203. and others, 1980;Lowrie and others, Baltz,E.H.,1965, Stratigraphy and history of Raton Basin tonBasin core with locationof paleomagneticsam- 1981).The result of this placement is a dia- Mexico: ples and favored interpretationfor polarity and notes on San Luis Basin, Colorado-New chronousCretaceous-Tertiarv boundarv with American Association of Petroleum Geologists, Bull., zonation.Black is normal,white is reversed. respectto terrestrial and marine extinitions. v. 49, no. 11.,p.2,M1.-2,075. Brown, W., 1943, Cretaceous-Tertiary boundary in the Anomalously high concentrations of iridium Denver Basin,Colorado: Geological Society of America, normal and one were reversed.A sample was undoubtedly occur within this normal po- Bull.,v.54, p.55-85. deemed to be normal (N) if all three speci- larity. A number of possibilities exist to ex- -,1962, Paleoceneflora of the Rocky Mountains and mens were normal or if two were normal and iridium Great Plains: U.S. Geological Survey, Prof. Paper 375, plain this result: 1) more than one p. one were indeterminate. This schemeis biased anomaly zone exists or 2) the Raton iridium 119 Butler, R. F., Lindsay, E. H., Jacobs,L. L., and Johnson, in favor of reversed polarities becauseit as- occurrence is the product of other concen- N. M., 7977,MagnetostratiSraphy of the Cretaceous- sumes that overprinting is predominantly of trating mechanisms (not an extraterrestrial Tertiary boundary in the San Juan Basin, New Mexico: a viscous nature acquired in the present impact). Nature, v. 267,p.318-i23. Brunhes normal-polarity zone. Johnson,R. B., and Wood, C. H., Jr.,1955,Stratigraphy Theseresults tend to confirm the data from of Upper Cretaceousand Tertiary rocks of Raton Basin, Fig. 3 gives our interpretation of the mag- the San fuan Basin. The Raton Cretaceour Coloiado and New Mexico: American Association of netic polarity zonation of the Raton core us- Tertiarv boundarv and the San Tuan Basin PetuoleumGeologists, Bull., v. 40, no. 4, p. 707-721. ing the above set of criteria. The interval magneio/paleontdlogic Cretaceous-Tertiary Johnson, R. B., Dixon, G. H., and Wanek, A. 4., 1966, between 835 and 852 is without Late Cretaceousand Tertiary statigraphy of the Raton doubt nor- boundarv both clearlv seem to occur within Basin of New Mexico and Colorado: New Mexico Geo- mal. This includes the palynological bound- normal fohrity zon6s. Additional palyno- logical Society, Guidebook 17th field conference, p. 88- ary and iridium abundance anomaly found logical work on the San juan Cretaceour 98. l=F

Nat: Mexico Geology August 19E3 43 Lerbekmo,I F, Evans,M E, and Baadsgaard,H, 1.979, Magnetostratigraphy, biostratigraphy, and geochron- ology of Cretaceous-Tertiaryboundary sediments,Red Galleryof GeologY Deer Valley: Nature, v. 279, p 26-30 Lindsay,E H,Jacobs,L. L, Butler,R F,1978,Biostra- tigraphy and magnetostratigraphyof Paleoceneterres- trial deposits, San Juan Basin, New Meico: Geology, v 6, p 425-429. Lindsay,E H , Butler,R. F., and Johnson,N. M, 1981, Magnetic polarity zonation and biostratigraphy o{ Late Cretaceousmd Paleocenecontinental deposits, Sm Juan Basin, New Mexico: American Journal of Science, v 281..p 390-435 Lowrie, W., and Alvarez, W, 1981,One hundred million yearsof geomagneticpolarity history: Geology, v 9, p 392-397 Ness, Gordon, Levi, Shaul, and Couch, Richard, 1980, Marine magnetic anomaly timescalesfor the Cenozoic and Late Cretaceous-a precis, critique, and synthesis: Reviews of Geophysics and SpacePhysics, v. 18, no. 4, p 753-770. Ortlr C I , Gilmore, J S., Knight, f. D., Pillmore, C. L , Tschudy, R H, and Fassett, I E., 7981, An iridium abundance anomaly at the palynological Cretaceous- Tertiary boundary in northern New Mexico: Science, v.274, p 7,341.-1.,U3. Pillmore, C L ,1976, Commercial coal beds of the Raton coal field, Colfa County, New Mexico: New Mexico GeologicalSociety, Guidebook 27th field conference,p

Tschudy, R. H , 7973,The Gasbuggy core-a palynolog- ical appraisal, ln Cretaceousand Tertiary rocks of the southem Colorado Plateau,James E. Fassett(ed.): Four Photoby GlennR Osburn Corners GeologicalSociety, p.131.-1.43 ! stable,perhaps a result of our presently dry cli- e414eevV41eVe4@1qu1 mate. Comparison with photographs nearly 100 yrs old (NMBMMR photo collection)shows vir- Geographicnames iually no changes,and if the abovelegends are image rnust have existed at U.S.Board on GeographicNames to be believed, the that. Chaves Canyon-canyon, 5.6 km (3.5 mi) long, least 200 yrs before is a magnificently dis- heads in the Sierra Blanca at 33"29'20' N., enon sometime in the distant Past. Magdalena Peak itself Miocene-age (14-m.y.-old) 105'50'55"W., trends northwest to join Sanders Just who that first observer may have been sected and exposed has removed roughly Canyon at the head of ChavesDraw, 1.1 km (0.7 we'll probably never know-few legends or writ- volcanic dome. Erosion rhyolite volcano, ex- mi) northeast of Chaves Mountain and 14 5 km ings regarding the event from either the Indians three-fourths of this old the left (south) shoulder (9 mi) south-southwest of Carizozo; Lincoln or Spanish seem to have survived. Nor do we posing the vent area on Lady the mountain. During the last stages of the County, New Mexico; sec.22, T. 9 S , R 10 E., know {or sure who named the feature "Our of vent was plugged by intrusive New Mexico principal meridian; 33'30'55' N., Magdalena."According to researchconducted by eruption, the the rugged nonlay- 105'53',35',W. the W.P.A. (Works ProgressAdministration) rhy-olite which now forms during the 1930's, the feature was discovered ered areathere. The prominent ledge to the right ChavesDraw-ravine, 72.9km (8 mi) long, heads and named over three centuries ago (circa 1630) (north) of the vent just below "oluur\ady"is well- in the Sierra Blanca at the iunction of Chaves by a group of Spanish explorers who had, sep- indurated, pyroclastic material from an early vi- Canyon and SandersCanyon at 33'30'55"N., aiated themselvei from the main expedition body' olent stage of the eruPtion. The upper third of 105"53'35"W., trends northwest to Willow Draw They were so impressed by the image that they the mountain above this ledge consists of Mag- 11.3 km (7 mi) southwest of Carizozo; Lincoln named the mountain "La Sierra de Maria Mag- dalenaPeak rhyolitic lavas. Theselavas piled up County, New Mexico; sec.26, T. 8 S., R. 9 E., dalena" in memory of Mary Magdalene who above the vent and flowed several miles to the New Mexico principal meridian; 33'35'22" N., "spent her last days in penanceand prayer on a south where they form many of the intermedi- L05"58'47"W.; not: SandersCanyon. mbuntain" in Spain (W.P.A. Collection, 1938). ate-heighthills just west of the main Magdalena Severallegends about the effect of the figure ridge. Danny Bobrow (New Mexico Institute of Diamond Peak-peak, elevation 2,577 m (8,453 do exist, however. The earliest legend dates at Mining & Technology M.S. candidate) has re- ft), in the Sierra Blanca 3.5 km (2.2 mi) west of least to the late Spanish or early Mexican occu- cently mapped Magdalena Peak in detail and is Church Mountain and 12 km (7.5 mi) southeast pation period during which a of travelers curently doing a detailed chemical study of this of Canizozo; Lincoln County, New Mexico; sec. Party was surrounded by a band of Apaches. Death and similar rhyolitic lavas in the SocorreMag- 70,T. 9 S., R. 11 E., New Mexico principal me- was imminent when suddenlv it is said, the im- dalena area. This study should be completed in ridian; 33'32'50'N., 105"47'48"W 1983. Goat Canyon----canyon,3.2 km (2 mi) long, heads on the northwest slope of Church Mountain in the SierraBlanca at tg"ZS'ZZ"N., f 05'46'11"W. References trends north to open out 11.3km (7 mi) south- Allen,R. S ,1916,editor, "The MogollonMines": sev- east of Carrizozo; Lincoln County, New Mexico; enthannual edition, Silver City, 48 pp sec.26, T. 8 S., R. 11 E., New Mexico principal and depredations spanning a century in time' Jones,F. A.,1904, "New MexicoMines and Minerals": Fe,New Mexico,349 pp., meridian; 33"35'02'N., 105'46'12'W.,not: Pine Both Geronimo and Victorio were said to have World'sFair Edition, Santa appendix. particularly avoided it. The east side oI Mag- plusbiographical Canyon. NewMexico Bureau of Minesand MineralTechnology, dalenaPeak became known as "a place of refuge Spring-spring, 0.81 km (0.5 mi) north of Photocollection, I E. Smithphoto, circa 1890. ]akes and the savageIndian would forego his bloody Mexico place names: Cottonwood Creek and 16km (10mi) southwest Pearce,T. M.,1965, editor, New deeds under the shadow of the holy mount" Albuquerque, University of New Mexico Press, 187 of Canizozo; Lincoln County, New Mexico; sec (fones,1904, p. 119). PP. I0, T. 9 S., R. 9 8., New Mexico principal me- Geologically "Our Lady Magdalena" is a talus W. P. A. Collection, 1938,County history file, Magda- ridian; 33'32'05'N., 105"59'50"W.; not:Nickeles slopecomposed of looseangular blocks of rhyo- lena:New Mexico StateRecords Center and Archives, Spring litii lava partially held in p6ce and enhancedin SantaFe. -Dave Love outline by various shrubs. Despite one's intui- -Robert Euelethand GlennR. Osburn,New MexicoBureau NMBMMRCorrespondent tive feeling that such a rock slope should be un- of Minesand Mineral Resources stable,this particular feature has been amazingly @1e\@ieeleeVVVl

August 1983 Nao MexicoGeology