Lexicon of Antarctic Stratigraphic Names: Introduced by Members of United States Expeditions (1972)

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2 . Definit ion "The southwes tern port ion of the is land is composed of coarse -grained biotite diorite . " 3 . Type sect ion a. Locat ion Southwes tern part of S tonington Is land , Antarct ic Peninsula b. Lithology Biotite diorite with zoned ol igoclase and andes ine , both of which have albite and peric line twinning . Taylor Formation 1 . Firs t publ ished use Wade , F . A . , V. L. Yeats , J . R. Evere tt , D . W. Greenlee , K. E . LaPrade , and J . C . Shenk. Geology of the central portion of the Queen Maud Range , Transantarct ic Mountains : Science 150 , p . 1808- 1809 , 1965 . 2 . Definit ion "The second sequence crops out along both s idea of Shackleton Glacier. It is a thick unit comprised of quartz ite , conglomerates , calcareous quartz ites , and marbles . The type locality is Taylor Nunatak , lat itude 84° 55 1 S , longitude 176° W ; the format ion is here named the Taylor . " (Wade et al , 1808 ) . 3 . Type section a . Location Taylor Nunatak , Queen Maud Range , on eastern margin of Shackleton Glacier b . Lithology Quartz ites , arkos ic quartz ites , hornfels and marbles . Regionally metamorphosed no h igher than greenschis t facies . c . Relat ion to other units Overlain by Beacon sequence - 113 -

Taylor Glaciat ion depos its 1 . First published use Pewe, T . L. MUltiple glaciat ion in the McMUrdo Sound region , Ant­ arc t ica- pa progress repor t : Jour . Geol . 6 8 , p . 498· 514 , 1 96 0 . 2 . Definit ion "The next recognized glacial advance in the McMUrdo Sound region is here named the Taylor Glaciat ion from the widespread depos its on the floor and lover s lopes of Taylor Dry Valley. " ( PeW, 506 ) 3 . Type sect ion a . Location Taylor Dry Valley , Victoria Land b . Lithology Light -colored and composed mainly of granite , marble , and gne i s s , with some dolerite cobbles . The Koettlitz Glacier drift is rich in dark , volcanic rocks , especially kenyte . Vent i facts well Jeveloped . c . Relat ion to other units Pos t•MCMUrdo Glaci at ion Pre-Fryxell Glaciat ion d . Synonyms or closely re lated names See Second Glaciation depos i ts Taylor Glacier diabase 1. First published use Hamilton , w. Diabase sheets differentiated by liquid fractionation, Taylor Glacier region , South Victoria Land : Antarctic Geology , Proc . Capetown Sympos ium, 1963 , John Wiley and Sons , p. 442 -454 , 1964 . 2 . Definition "The diabase occurs as thick sills with inclined segments and as thin steep dykes . Sills are most ly 300 to 1500 ft . (90 to 460 m) thiCk, but many of the steep dykes are only a few feet thick . Most intruaions lie within the Beacon sandstone . • • • (Hamilton, 443) - 114 -

3 . Type sect ion a. Locat ion Taylor Glacier region , Victoria Land b . Thickness 300 - 1500 feet c . Lithology Dark gray aphanitic basalt at edges grading through fine and mediu.-grained diabase to green-gray gabbro with granophyre inters titial ; pigeonite , hypers thene , plagioclase ; liquid fractionat ion enriched upper parts of gabbro in s ilica , ferric iron , alkalis and t itania d . Relat ion to other units Intrudes Beacon Sandstone and older rocks Terra Cotta Mountain Member (of Beacon Group ) 1 . Firat published use Zeller , E . J. , E . B . Angino an6 �. D •. Turner . Basal Sedimentary Section at Windy Gully , Taylor Glacier , Vict01ia Land , Antarctica : GSA Bull . 72 , p . 781·5 , 196 1 . 2 . Definition "Above this break in lithology , there is 110 feet of alternat ing sandstone and shale beds of different color and thickness , here des ignated the Terra Cotta Mountain member . " (Zeller , 196 1) 3 . Type sect ion a. Locat ion North Flank of Terra Cotta MOuntain , Upper Taylor Valley, Vi ctoria Land b . Thickness 110 feet c. Litho logy Interbedded sandstones and dark fiss ile shales - 115 -

d. Relation to other units It overlies Windy Gully Member and underlies a buff fine ­ grained sandstone member des ignated Al . e . Evidence for age Through analogy to Beacon Group in other areas , a Devonian­ Triasa ic age is ass igned t o the entire group here . Terra Firma Volcanics 1 . Firat published use Nichola , R. L . Bedrock geology of Marguerite Bay area , Palmer Peninsula , ADtarct ica : Ronne Ant . �ea . Exped . T�ch . Rept . 13 , Office of Naval Research , Washington , D . C . , 60 pp . , 1955 . 2 . Definition "The largest of the Terra Firma I slands is composed mainly of fela itic volcanics . MOat of these volcanics are either black porphyriea or crystal tuffs , although pyroclastic breccias containing angular fragments of granite , grani te gneiss , aplite , gabbro , felsite and other rocks are present . " (Nichola , 53 ) 3 . Type section a. Location Terra Firma Is lands , Antarctic Peninsula b. Thickness About 2000 feet c. Lithology Andesite or andes ite porphyry with andeaine pbenocryata and microlitea in a fine-grained matrtx of chlorite , epidote , and calcite . 5% each of dacite , basalt , and rhyolite . Trevea , S . B . Volcanic rocks from Rosa Island , Marguerite Bay and Mt . Weaver areas , Antarctica : Proc . of Sym. on Pac•Ant . Sci . , Tokyo , p . 136 -149 , 1967 . - 116 -

Thiel MOuntains granite 1 . First published use Ford , A . B . ; Aaron , J. � Bedrock geology of the Thiel MOuntains , Antarctica : S cience 137 , p . 751·7 52 , 1962 . 2 . Definition "A s tock of med ium-grained biot ite granite , intrus ive into the quartz monzonite porphyry , is well exposed on a large nuuat&k on the ice escarpment . Near the contact the quartz and potass ium feldspar of the porphyry have been thoroughly recrystallized and ha· re a grano­ b lastic texture . " (Ford & Aaron , 752) 3. Type section a. Locat ion Thiel MOuntains , about 90° W , 85° 20 1 s . b . Relation to other units Intrudes Thiel MOuntains quartz monzonite porph�r c . Evidence for age Lead-alpha ages of z ircons indicate : s 86 ° 50 1 w s 89 ° 2 5 1 w Calculated age (m. y. ) 470 ± so 560 ± 60 Ford , A. B. Cordierite -bearing hypersthene•quartz -t"Dnzonite•porphyry in the Thiel MOuntains and its regional impc•rtance : Antarctic Geology : Proc. Capetown Sympos ium 1963 , John Wiley & Sons ; p . 429 -441 , 1964. Thiel MOuntains quartz monzonite porphyry 1. First published use Ford , A. B . ; Aaron , J. M. Bedrock geology of the Thie 1 •·ountains , Antarctica : Science 137 , P • 751 -7 52 , 1962 . 2 . Definition "Medium-grained quartz monzonite porphyry is the most widespread rock. The mass has a miniuum dimens ion of 20 miles north -£ outh and 15 miles east -west . On fresh surfaces the rock appears almost even - 117 -

grained , but where weathered the alterat ion products on feldspars make the s trongly porphyritic , nonseriate texture evident . " (Ford & Aaron , 7 51- 7 52) 3 . Type sec tion a. Locat ion Thiel MOuntains , 90° W , 85 ° 20 ' S b . Lithology Medium-grained , dark gray , granit i c-appearing rock shows angul ar feldspar in a very fine-grained matrix . Porphyritic (40-70% phenocrys ts ) texture ; pheoncrysts of plagioclase , quartz are dominant in a quartz and alkali feldspar matrix . Potass ium feldspar , hypers thene and cordiorite phenocrysts also present . c . Relat ion to other units Intruded by Thiel MOuntains granite d. Evidence for age Lead-alpha ages of z ircon concentrates are 580 ± 60 m. y . and 620 ± 70 m. y. for the porphyry and suggest an orogenic e vent in late Precambrian or early Cambrian time . Evidence of recrys tal lizat ion includes 1) hornfels ic groundmass texture , 2 ) cord iorite appearing to replace feldspar , 3 ) poikilob las tic rims on K·fe ldspar phenocrysts , 4) alteration rims of biotite and chlorite around hypers thene . Because these features are more common in the vicinity of biot ite granite contacts , they are probably effects of thermal metamorph ism related to the intrus ion . Therefore , z ircon ages reported may reflect the age of the younger intrus ions rather than crys tallizat ion of the porphyry. Ford , A . B. , H . A . Hubbard , T . W . S tern . Lead-alpha ages of z ircon in quartz monzonite porphyry , Thiel Mountains , Antarct ica -- a preliminary report : USGS Prof Paper 450-E , p . 105 -107 , 196 3 . New lead -alpha age of 670 ± 5 0 m. y. from z ircon Aaron , J. M. ; Ford , A . B . Isotope determinat ions in the Th iel Mountains , Antarctica : GSA Spec Paper 76, p . l , 1963 . - 118 - - - - -.1