The Geology of the Rockefeller Mountains, King Edward VII Land, Antarctica Author(s): F. Alton Wade Source: Proceedings of the American Philosophical Society, Vol. 89, No. 1, Reports on Scientific Results of the United States Antarctic Service Expedition, 1939-1941 (Apr. 30, 1945), pp. 67-77 Published by: American Philosophical Society Stable URL: http://www.jstor.org/stable/985315 Accessed: 03-03-2015 04:01 UTC

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This content downloaded from 169.229.32.36 on Tue, 03 Mar 2015 04:01:13 UTC All use subject to JSTOR Terms and Conditions THE GEOLOGY OF THE ROCKEFELLER MOUNTAINS, KING EDWARD VII LAND, ANTARCTICA

Major F. ALTON WADE, U. S. Army Senior Scientist, U. S. Antarctic Service

INTRODUCTION mapped from aerial photographs taken that IN spite of the fact that threeexpeditions had same season. had theirmain bases a littlemore than 100 miles DuringByrd Antarctic Expedition II, 1933-35, away from one group of mountains in King several partieswere in the vicinityof the Rocke- Edward VII Land, practically nothing was feller Mountains during the sledging season. known of the geology of that peninsula prior Mount Helen Washingtonwas exploredin part to 1940. by the party which was under the leadershipof The discoveryof King Edward VII Land was Paul A. Siple5 and of which the author was a made by Scott 1 in 1902 whileon his firstexpedi- member. This party, homeward-boundfrom a tion to the Antarcticregions. The low range of surveytrip in Marie Byrd Land, was unable to mountains,subsequently named the Alexandra remainlong enough to completea surveyof the Mountains (fig. 1), was sightedby him as were many peaks. Mount Nilsen was visitedand as- the bare rock exposures on Scott's Nunataks. cended by a three-manparty later that same Ice conditions prevented him from making a season, but no specimenswere collected. landing. The geologicalknowledge of King Edward VII The firstand only partyto visit the mountains Land was limited,therefore, to analyses of rocks discovered by Scott was led by Lieut. K. fromScott's Nunataks, the most northernpeaks on the peninsula,and to analyses of rocks from Prestrud2 in 1911. During the same season, when the leader of the expedition,Amundsen, Mount Helen Washington,the most southerly was making his trip to the Pole, Prestrudand peak, prior to the investigationsof the United two companions sledged eastward on to the ice States AntarcticService Expedition, 1939-1941. plateau covering the greater part of Edward The regionlies between two of the better-known Land and to Scott's Nunataks, which they and geologicallydifferent regions of Antarctica. ascended and where they collected a few rock The mountains of the Antarctic Horst which specimens. borderthe Ross Shelf Ice on the west and south had been explored The moresoutherly group of mountainson the by membersof several British expeditionsand of the two peninsula was discoveredby Admiral Byrd 3 on Byrd Expeditions. January27, 1929, while on his firstexploratory The westernportion of the Edsel Ford Mountains flightin Antarctica,and was subsequentlynamed in Marie Byrd Land, which lies to the east of by him forJohn D. Rockefeller,Jr. (figs.2, 3). King Edward VII Land, was exploredin 1934 by An attemptto explorethese mountains was made Siple and Wade,6and the plans forthe U. S. A. S. by Byrd's second-in-command,L. M. Gould, Expeditioncalled fora continuationof the work later in the same season. His survey was begun by them. prematurelyended afterhe had visited only one According to David,7 the geology of the peak, Mount Helen Washington,when disaster, Antarctic Horst region is as follows:, pre- resultingin the loss of a plane, overtook his Cambrian gneisses, schists, limestones, and party.4 The RockefellerMountains were first graywackes compose the basement complex. This is overlain by a great series of nearly 1 Scott, R. F. The voyage of the "Discovery" 1: 183. London, 1905. 5 Byrd, R. E., op. cit., 347. 2 Prestruid,K. Eastern sledge journey. In: Amundsen, 6Wade, F. A. Petrologicand structuralrelations of the R., The South Pole 2: 204-261. London, 1913. Edsel Ford Range, Marie Byrd Land, to other Antarctic 3 Byrd, R. E. Little America, 124-125. New York, mountains. Bull. Geol. Soc. America 48: 1387-1395, 1937. 1930. 7David, T. W. E. Antarctica and some of its problems. 4Byrd, R. E., op. cit., chap. 8. Geog. Jour. 43: 624-626, 1914.

PROCEEDINGS OF THE AMERICAN PHILOSOPHICAL SOCIETY, VOL. 89, NO. 1, APRIL, 1945 67

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This content downloaded from 169.229.32.36 on Tue, 03 Mar 2015 04:01:13 UTC All use subject to JSTOR Terms and Conditions GEOLOGY OF THE ROCKEFELLER MOUNTAINS 69 flat-lyingPaleozoic and early Mesozoic sand- igneous intrusivesto be of the acidic type, high stones, arkoses, and shales. Near the close of in sodium and potassium,with the plagioclases the Mesozoic this region was subjected to a exhibitingnio zoning. From his investigations period of block-faulting. The Antarctic Horst in 1934 the author10 concluded that the sequence was formedat that time. A period of volcanic of events in the Edsel Ford Mountains was as activityaccompanied and followedthese tectonic follows: "deposition of a great series of arkosic disturbances and is even continuing today. sandstonesand shales on the pre-Cambrianbase- There is no evidence of Antarctandeanfolds in ment rocks,close foldingof this sedimentaryse- this region. The petrographicinvestigations of ries accompanied and followed by deep-seated Prior,8 Stewart,9 and others have shown the igneousintrusion of acidic magma,a long period of erosion,glaciation and the extrusionof olivine 8 Prior, G. T. Report on the rock-specimens[etc.]. NationalAntarctic Exped. 1901-1904,Nat. Hist. 1, Geol.: fourchites." The intrusivesdiffer from those to 101-140,1907. the west and south in that the plagioclases 9 Stewart,Duncan, Jr. A contributionto Antarctic petrography.Jour. Geol. 42: 550, 1934. 10 Wade,F. A., op. cit., 1391-1392.

Officialphotograph, U. S. AntarcticService FIG. 1. The AlexandraMountains, King EdwardVII Land; lookingsoutheastward along the northeastcoast ofthe peninsula.

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Officialphotograph, U. S. AntarcticService

FIG. 2. The southerngroup of the RockefellerMountains; looking southwestward. MounitTennant MountHelen Washington MountFranklin MountGould MountSchlossbach MountBreckenridge MountPaterson MountNilsen exhibit well-developed zoning, a characteristic FIELD OPERATIONS of Palmer Land whichlie some of the intrusives On February8, 1940,an exploratoryflight was miles to the east. 1500 made over Edward VII Land, at whichtime the and examined the Schetelig"1 investigated author was enabled to examine the regionas a by Prestrud from Scott's rocks brought back whole. Later the entirecoast line of the pen- 12 withthose Nunataks, and Stewart did likewise insula and the two mountainranges were photo- fromMount broughtback by Gould and Wade graphed fromthe air by Charles Shirley,C.P., Both were of the opinion Helen Washington. U.S.N., the officialWest Base photographer. Edward VII Land intrusiveshave that the King The picturesthus obtained were of great assist- AntarcticHorst. close affinitieswith those of the ance in layingplans forthe fieldprogram. of Mount From his rathercursory examination On November25, 1940, the party,comprising Helen Washingtonthe authorwas of the opinion two men and a singleteam of six dogs, leftWest that the intrusives exhibited there closely Base forKing Edward VI I Land. Dr. RussellG. east resembledthe ones he had examinedto the Frazier, expedition physician and surgeon,ac- in the Edsel Ford Mountains. companiedthe author. The plan was to proceed to the RockefellerMountains and there survey 11Schetelig, J. Reporton rock-specimenscollected on the peaks composing that group. With only Skrifter Roald Amundsen's South Pole expedition. seven weeks' time available forthis operation,it Vidensk.-Selsk.Kristiania 1915, Mat.-Naturv.Ki., no. 4: 1-32, 1915. would not be possible forthe party to extendits 12 Stewart,Duncan, Jr., op. cit. itineraryto includethe Alexandra Mountains,if

This content downloaded from 169.229.32.36 on Tue, 03 Mar 2015 04:01:13 UTC All use subject to JSTOR Terms and Conditions GEOLOGY OF THE ROCKEFELLER MOUNTAINS 71 dog-teamtransportation were relied upon alone. PHYSIOGRAPHY It was planned, therefore,that the Beechcraft The exposed portion of the Rockefeller plane should be flownto the Rockefellersduring Mountains occupies an area approximately20 the timewhen the partywas in that region,pick milessquare. As comparedwith such Antarctic up the author and transporthim to the heartof ranges as the Queen Maud or the Edsel Ford, the Alexandras, where he could hastily survey they are not a particularly impressive sight. those peaks in a few days' time and then be re- The black and pink peaks of the southerngroup turnedto complete the work in the Rockefeller (fig. 2) protrudethrough the ice sheet and ex- Mountains. Unfortunately,this phase of the tend above the irregularice surfacefor varying programhad to be abandoned because of unfore- heightsnot exceedingseveral hundredsof feet. seen circumstances,and the surveywas confined Their crestsare elevated between1500 and 2000 entirelyto the RockefellerMountains. feet above sea-level. Nine distinct mountains The party arrived at the firstpeak, Mount and severalknolls and ridgescompose this group. Tennant, on December 10. During the next 18 The northerngroup, composed of four separate days 13 peaks were visited, examined, and mountains(fig. 3), is more deeply buried in the surveyed. The triangul'ationnetwork was estab- ice sheet. The central peak, Mount Margaret lished for us by R. G. Fitzsimmons and the Wade, is the highestone in the Rockefellers,and seismicstation party that was occupyingMount on the wholepeninsula it is second in heightonly Franklinduring the summer. to Mount La Gorce in the AlexandraMountains. The returntrip to West Base was begun on General observationsfrom the air and a study December 30, and the party arrived there on of photographsof the peninsulaindicate that the January7, 1941. centralportion of the peninsulawas a centerof

Officialphotograph, U. S. AntarcticService FIG. 3. The northerngroup of the RockefellerMountains; looking northwestward. MountIrene Frazier MountJackling MountMargaret Wade MountShideler

This content downloaded from 169.229.32.36 on Tue, 03 Mar 2015 04:01:13 UTC All use subject to JSTOR Terms and Conditions 72 F. ALTON WADE ice accumulation during the early part of the of a long, extensive period of erosion during glacial period,and that the thickerportion of the which the capping material has been removed. local sheet now unitedwith the largerone to the Apparently,the igneousrocks were able to resist south is located there. It appears to thin out the erosive processes more than the overlying somewhatin all directionsaway fromthe central metamorphosedsediments, and today the ma- portion. This explains why the high peaks of jorityof the erosionremnants are of the former the northerngroup are less exposed than those material. It is believed that this strippingwas of the moresoutherly group. largelyaccomplished prior to the presentglacial In general, the portions of the mountains period,but that the presentforms are due to the which protrudethrough the ice sheet are largely glacial erosionthat followed. exposed (figs.4, 9). Some of the horizontalor Wind and frostaction are playingthe leading roles in the erosion that is taking place in the exposed outcroppingsand thinlycovered rocks today. During the summermonths melt-water can be observed on those rocks subjected to direct sunlight. The water apparently works into all cracks and joint planes, particularly along the faces of the large feldsparcrystals of the intrusives. The wedgingaction that follows whenthe waterfreezes causes disintegration,and beds of unconsolidatedrock debris up to 6 inches thickare collectedin flat protectedplaces (fig.5). The greaterpart of this debris is composed of large, uneroded feldspar crystals. The finer Photoby Wade materialhas probablybeen transportedaway by FIG. 4. The granitecrest of MountIrene Frazier. the winds. This is substantiated by the fact that one may observe large quantities of fine gently sloping surfaces are covered with snow rock material on the snow surface at varying and ice, but many good outcrops are available distances fromthe exposed peaks (fig.6), some- forthe geologistto study. The valleys between times as much as a mile away fromthe nearest peaks, some of which are widely separated, are exposure. filledwith glacier ice, and consequentlyinter- Frost action on the metamorphosedsediments polationof structurebetween known points must generallyresults in the slopes beingcovered with oftenbe placed in the categoryof vague specu- a layer of angular blocks of varying sizes, lation. Petrographicallythe peaks may be placed in two groups. The majority of the peaks are composedof acidic intrusivesand a small central group of metamorphosedsediments. They can be easily differentiatedin the field,since those of the firstgroup always appear pink to red in color from a distance and those of the latter groupdark gray to black.

EROSIONAL FEATURES The presenttopographic features have resulted fromice and wind erosion. Insufficientdata are available for a complete interpretationof the historyof the region,but a few facts point to what must be certain truths. The extreme Photoby Wade coarseness of the texture of the granitic rocks would indicate with a FIG. 5. The pittedsurface of MountShideler. Beds of deep-seated intrusion, loose feldsparcrystals several inches thick have thick layer of insulatingrock formationsabove. accumulatedon the floorsof erosiontroughs such as That these intrusivesare exposed today is proof thisone.

This content downloaded from 169.229.32.36 on Tue, 03 Mar 2015 04:01:13 UTC All use subject to JSTOR Terms and Conditions GEOLOGY OF THE ROCKEFELLER MOUNTAINS 73 generallydepending on the spacing of the joints The igneous rocks seem to have been more in the affectedrock (fig.7). susceptible to wind erosion than have the metamorphics. Most of the exposures of the formerexhibit a pitted surface (figs.5, 8), and the slopes and verticalsurfaces from a distance appear to be " pock-marked" (fig.9). On closer inspectionthe pock-markstake on the appear- ance of potholes (figs. 10, 11, 12). They are generallywell roundedand may varyin size from 4.,~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~,minute ones to some 4 to 5 feetin diamater. It is believedthat theseare formedby the eddying which makes use of the ice r~~~~~~~~~~~~~~~~~~~~~~~~~~~i~~~~~~~~~~~0action of the wind crystals and rock fragmentsthat it carries as abrasives. In many of these holes small collec- tionsof rock fragments and rockflour were noted. Photoby Wade FIG. 6. Rock particles that have been wind-borne to STRUCTURAL INTERPRETATIONS their restingplace on the snow surface some distance The greater part of the exposed portionsof fromMount Margaret Wade. the RockefellerMountains is highlyacidic, in- trusive,igneous rock which appears to surround a remnantof the pre-existingmetamorphosed sediments. The latter are exposed at Mount Nilsen,Mount Breckenridge,West Nilsen Ridge, and Mount Franklin. The sediments were apparently folded and metamorphosedprior to the intrusionof the graniticbatholith. The originalmetamorphism was probably of the dynamothermaltype pro- duced duringorogenic deformation that resulted in fold mountains. Metamorphismwas con- tinued and intensifiedthrough contact when Photoby Wade the batholithwas intruded. FIG. 7. Frost action has caused the disintegrationof the The fold axes have a northwest-southeast exposed rock at Mount Franklin into angular blocks trendand the beds in the area examineddip from of many sizes. 250 to 450 to the southwest. The granite-schist contact was observed in one place only, Mount Franklin. There the intrusivediscordantly cuts the sediments. The contact is sharplydefined, and there has been little apparent assimilation of the intrudedrock by the granite. Although no other contacts were observed, it would appear from the flow-structurepattern, where apparent in the granite,that for the most part the intrusivefollowed the pre-existingstructural trends(map 1). The structural features of the Edsel Ford Mountains to the east are very similarto those of the RockefellerMountains. In the former " the general structural pattern is a series of northwest-trending,broad, open folds." 13 Photoby Wade FIG. 8. Differential erosion of the coarse granite has 13 Passel,C. F. Sedimentaryrocks of the Southern Edsel resulted in a rough,pitted surface. Mount Margaret Ford Ranges,Marie Byrd Land, Antarctica. Proc.Amer. Wade. Philos.Soc. 89: 123-131,1945.

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this rock. With the same exceptionsthis also may be said for Mount Paterson,Mount Helen Washington,Mount Gould, Mount Schlossbach, Mount Tennant, Mount Navy, and Mount Franklin (in part) in the southerngroup. The texture of the rock varies considerablyfrom place to place. It is medium-grainednear the contact at Mount Franklin,fairly coarse at the otherpeaks in the southerngroup, and extremely coarse-grainedin the northerngroup of peaks. In places, particularly at Mount Margaret Photoby Wade Wade, it has the appearance of a porphyrywith FIG. 9. Mount MargaretWade. The "pock-marked" lath-shaped phenocrystsof perthite up to 4 surfaceis a resultof wind erosion. inches in length enclosed in a coarse-grained groundmass (fig.13). In places there are finer,uniformly grained portionsof the granite which are as much as 20 feet in diameter. The compositionof the finer portion is similar to that of the more coarse-grainedexcept that it lacks, or contains only a small percentageof, perthite,and the percentagesof the other constituentfeldspars are increasedaccordingly. The transitionfrom coarse to fineis zonal and is accomplishedin a zone never more than 4 inches wide (fig. 14). This transitionis not always complete,as single, well-scatteredcrystals of perthiteup to 2 inches long may be observed occasionally throughout Photoby Wade the finer-grainedgranite (fig. 15). FIG. 10. Wind-formedpotholes on the nearlyvertical The quartz is of the smokyvariety-bleached faceof MountMargaret Wade. on the weatheredsurface, but black beneath the weatheredzone. At firstglance a freshspeci- men of the rock has the appearance of a diorite because of the natural tendency to identify wronglythe black quartz as one of the biopyra- bole family. The feldspars present in the intrusive are orthoclase,perthite, microcline, and plagioclase. In general the percentageof potash feldspars exceeds that of the plagioclase. The latter are generally zoned; the central portion has the compositionof oligoclase to andesine, and the outer borders are albite. The compositionof the unzoned plagioclases is that of oligoclase. One specimen of the main rock of Mount Photoby Wade Schlossbach,taken froma borderzone adjacent FIG. 1. Large,deep, well-rounded, wind-formed potholes. to a quartz-filledfissure, was morebasic and the MountShideler. plagioclase was found to be labradorite. The largerfeldspar crystals are perthite. PETROGRAPHY The micas.-Primary muscoviteis presentin The principal intrusive of the Rockefeller the granitefrom the specimenscollected in the Mountains is, forthe most part, a leucogranitic northerngroup of peaks, but does not show up type rock. Except fora fewdikes and segrega- in the thin sections of the specimensfrom the tions,the northerngroup is entirelycomposed of southerngroup. Sericite is present in all thin

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Photoby Frazier Photoby Wade FIG. 12. The wind-erodedsurface of Mount Shideler. FIG. 15. The porphyriticphase of the graniteat Mount Jackling. The fewlarge phenocrysts are perthite.

sections. Biotite is the only essential mafic constituentpresent. The amount varies from a fractionof 1 per cent to 10 per cent. Zircon crystalswith their pleochroichalos are always presentin the biotite. The biotite is generally alteredin part to chlorite. Accessoryconstituents.-Fluorite is a common accessory in the southernpart of the batholith and absent in the northernpart. Magnetite, apatite, and zirconare generallypresent. It is noteworthythat no intermediate,basic, or ultrabasicigneous rocks have been noted in this region. Even the few dikes which are Photoby Wade present are acidic in composition. The af6re- mentioned specimen from FIG. 13. The is Mount Schlossbach granite extremely coarse-grained at is the Mount Margaret Wade. Some of the only exception. Its approximatecompo- perthite sition is: crystalsare over 3 inches long. hornblende,45 per cent; biotite, 21 per cent; labradorite,23 per cent; and quartz, 8 per cent. The dike rocks are in general similar in mineralogicalcomposition to the main intrusive. The oligoclase content is greaterand the other leuco constituentsare less common. * Mount Breckenridgeis located near the ig- neous contact. It is for the most part com- posed of schists which have been intruded by dikes of leucograniticrock similar in composition to the main intrusiveand by pegmatite dikes (fig.16). The pegmatiteis composedprincipally of perthite and quartz. Scattered irregularly throughthe dikes are well-formedgarnets (an- dradite) which vary in size frommicroscopic to Photoby Wade a few 2 inch in diameter. FIG. 14. The zonal contact between the coarse-grained The mineralogicalcompositions of the igneous and the porphyriticphases of the granite at Mount rocks are listed in table 1. Only rough quanti- jackling. tative mineralogicalanalyses have been made of

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I~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Photoby Frazier FIG. 16. Mount Breckenridge.The darkschists which principally compose this mountain have been intrudedby a seriesof garnetiferous pegmatite dikes. The latterare easilydiscerned in theillustration. theserocks, and the classificationnames assigned The igneous rocks of the RockefellerMoun- to them are only tentative. The results of a tains are high in sodium and potassiumcontent more thorough petrographicanalysis appears and extremelylow in maficconstituents. elsewherein this publicationin a reportby Dr. A thoroughstudy of the metamorphicrocks Duncan Stewart,Jr. has not yet been attempted. They are for the TABLE 1

MINERALOGICAL COMPOSITION OF THE IGNEOUS ROCKS FROM THE ROCKEFELLER MOUNTAINS

SPECIMEN MINERAL 286 292 224 223 301 296 288 291 373 219 218A 218B 206 355 24 236 325 326 201 205A 21 22 327 343 351

Quartz...... x x x x x x x x x x x x x x x x x x x x x x x x x Orthoclase ...... x x x x - x x x - x x x x x x x x x x x x x x x Perthite...... x x x x x x x x x x x x x x - x x x x x x Microcline ...... - x xx x x _ - - x? Plagioclase ...... x x x x x x x x x x x x x x x x x x x* x x x x x Muscovite ...... - - x x x - x Biotite chlorite.... x x x x x x x x x x x x x x x x x x x x x x x x Hornblende ...... _ x Magnetite ...... x x - x x x x_ _ Limonite...... - x _ Fluorite ...... - x _- - xx x x - x xx Apatite ...... x x x x x x - x? ? ?? x? Topaz...... x Zircon ...... x x x x x x x x x x x x x x - x x x x x x x Garnet ...... - Sericite ...... - x x x x - x x x x x x x x x x x x x x x x x x x Kaolin ...... - x x - - x x x x x x x x x x x _ x x x x x Serpentine ...... - x x x = present in thin section. * Labradorite. 286. Monzotonalite. MountNavy. 355. Leucoadamellite. MountHelen Washington. 292. Monzogranite.Mount Navy. 24. Monzogranite.Mount Helen Washington. 224. Leucogranodiorite.Mount Jackling. 236. Adamellite. MountTennant. 223. Orthoalaskite.Mount Jackling. 325. Quartzgranodiorite. Mount Schlossbach. 301. Leucomonzogranite.Mount Irene Frazier. 326. Leucogranodiorite.Mount Schlossbach. 296. Leucoadamellite. MountTennant. 201. Orthoalaskite.Mount Schlossbach. 288. Leucomonzotonalite.Mount Gould. 205A. Mela-quartz-gabbro.Mount Schlossbach. 291. Leucogranodiorite.Mount Gould. 21. Leucomonzotonalite.Dike rock. MountHelen 373. Monzogranite.Mount Paterson. Washington. 219. Leuco-sodaclaseadamellite. MountMargaret 22. Leucogranodiorite.Dike rock. MountHelen Wade. Washington. 218A. Alaskite. MountShideler. 327. Leucogranite. Dike rock. MountFranklin. 218B. Leucogranite. MountShideler. 343. Alaskite. Dike rock. MountFranklin. 206. Monzogranite.Mount Schlossbach. 351. Leucomonzotonalite.Dike rock. Mount Franklin.

This content downloaded from 169.229.32.36 on Tue, 03 Mar 2015 04:01:13 UTC All use subject to JSTOR Terms and Conditions GEOLOGY OF THE ROCKEFELLER MOUNTAINS 77 most part gneisses, schists, and phyllites. and those of King Edward VII Land is also very Quartz, feldspar,and biotite are the dominant striking. The author has visited and studied minerals. The results of a preliminaryexami- both localities and believes them to be closely nation of the thin sections appear to indicate related. that these rocks are closely related to the meta- morphosedsediments of the Edsel Ford Moun- CONCLUSIONS tains in Marie Byrd Land. From his study The RockefellerMountains are composed of of the thin sections of the specimens of the a seriesof metamorphosedsediments which have latter rocks, Stewart"' concludes: "The meta- been intruded by a granitic batholith. The morphictypes fromthe Edsel Ford Ranges are intrusiveis high in sodium and potassium and quite differentmineralogically from the meta- low in mafic constituents. The plagioclase morphicbasement rocks of certain other parts feldsparsgenerally show a well-developedzoning. of the Continentand must be consideredof an Structurallyand petrographicallythey resemble age other than pre-Cambrian." As yet no the Edsel Ford Mountains and could well be fossilshave been foundin any of the rocks from consideredpart of the same geologicalunit. No either Marie Byrd Land or King Edward VII true relationshipis indicated between this unit Land, and the geological age of none of the and any of the previouslydescribed Antarctic formationshas been fixed. localities. The slowly accumulatingdata seem From Schetelig's15 descriptionsof the rocks to indicate more and more that King Edward collected at Scott's Nunataks, it would appear VII Land and Marie Byrd Land togethershould that the granitesare definitelyrelated to those be considered a separate petrographic and of the RockefellerMountains. The similarity structuralprovince. between the rocks of the Edsel Ford Mountains ACKNOWLEDGMENTS 14Stewart, Duncan, Jr. Notes on some Marie Byrd Land rocks. Am. Mineralogist26: 47, 1941. The author is indebted to Dr. R. G. Frazier 15 Schetelig, J. Report on rock-specimenscollected on Roald Amundsen's South Pole expedition. Skrifter for his able assistance in the field and to Mr. Vidensk.-Selsk.Kristiania 1915, Mat.-Naturv. Kl., no. 4: WillardF. Brinkerfor his assistancein analyzing 1-32, 1915. the specimens.

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