by Allison Mattheis
I. Overview of Antarctic Geology
A. Total Area: about 5,000,000 square miles (Anderson 2).
B. Two distinct regions: Eastern and Western halves of continent.
1. Eastern Antarctica: continental shield region south of Africa and Australia, composed
elevated basement complex of gneisses, schists and other metamorphic rocks.
Intrusions of granitoids. This complex is covered by a series of clastic sedimentary
rocks that form a thick, mainly undeformed layer. This cover also includes dikes and
sills. (Anderson 1). Center of shield depressed due to massive ice sheet ("Antarctic
Geology." Location: centered on 90 degrees east longitude (Hill)
2. Western Antarctica: basement of intrusive and metamorphic rocks covered by deformed
clastic and volcanic rocks of Paleozoic, Mesozoic and Cenozoic ages. The Ellsworth
mountains are located in this region. (Anderson 1). Location: centered on 90 degrees
west longitude (Hill). Some active volcanic centers still exist ("Antarctic Geology").
-suspected plate boundary underneath West Antarctic Rift ("Antarctica- the
Dynamic...")
C. Transantarctic Mountains separate East and West- one of world's largest mountain ranges:
-15,000 foot maximum elevation (Hill).
-3500 km. long (Hambrey 140).
-formed during Paleozoic during Ross Orogeny (Hill).
-composed of sandstone, shale, limestone and coal (Hill).
1. Main mountain ranges of Transantarctic Mountains:
-Queen Maud mountains, Horlick mountains, Thiel mountains, Dufek Massif,
Whichaway Nunataks, Shackleton Range, Theron mountains.
D. 98% of continent permanently covered by ice and snow ("Antarctic Geology")
E. Commonly used dating methods for Antarctic rocks:
1. Paleontology data
2. K/A method- absolute age dating useful due to lack of accessible outcrops and
extensive ice cover (Angino and Turner 551). Jurassic lavas extend across
continent, can be dated (Windley 228).
II. Early tectonic activity
A. Precambrian: 552-553 ma: Vestfold and Bunger orogens (Angino and Turner 552)
B. Paleo-Pacific margin of East Antarctic craton: tectonic boundary represented by Transantarctic
mountains. Margin site of Proterozoic to Paleozoic orogenesis due to oblique subduction of
oceanic lithosphere beneath craton (Goodge, Walker and Hansen 37, 39).
III. Ross orogeny
A. Dominates Eastern half of Antarctica: evidence of effects on entire eastern periphery; but new
evidence suggests Ellsworth mountains in Western Ant. show folding and cleavage resulting
from the Ross orogeny (Goldstrand et al. 427).
B. begins in Neoproterozoic with rifting of Laurentia away from Gondwana, followed by
passive continental margin sedimentation (Hambrey 140).
1. single deformation event with several continuous phases during Late Cambrian and
Ordovician times (Storey et al. 686) OR
2. possibility of multiple, periodic deformations from Neoproterozoic to middle
Cambrian (Goodge, Walker and Hansen 39).
C. Mainly active in Paleozoic
1. traditionally referred to as product of tectonism in Late Cambrian and Early Ordovician
(Rowell, Rees and Evans 31). Resulted in compressional deformation and granitic
magmatism (Storey et al. 685).
2. two distinct period of tectonism: late Cambrian to early Ordovician, and late Ordovician
to early Silurian (Angino and Turner 552-553).
D. early Cambrian: beginning of major phase of folding, related to suturing of East and West
Gondwana (Rowell, Rees and Evans 31).
E. Ross orogeny synchronous with suturing of Gondwana supercontinent (Goodge, Walker
and Hansen 37).
F. Defined in Nimrod Glacier area by deformation of Shackleton Limestone (Goodge, Walker
and Hansen 39).
G. responsible for formation of basement of Transantarctic Mountains (Storey et al. 685).
1. difficult to correlate specific events, however, due to variations along length of
Transantarctic mountains; fault boundaries unspecific (Storey et al. 686).
H. Late Cambrian: change in depositional environment from carbonate platform sedimentation
to siliclastic sedimentation shown in formations within the Ellsworth mountains (Goldstrand
et al. 429).
I. Five orogenic belts formed during Ross orogeny:
1. Conradfjella through the Sor Rondane mountains to Lützow-Holmbukta
2. Mawson to Prydz Bay
3. Pingvin Island to Bunger Hills
4. Ainsworth Bay to Cape North
5. McMurdo Sound region
IV. Continental Drift and Antarctica
A. SWEAT (Southwest United States-East Antarctic) hypothesis: suggests that East Antarctica
and Laurentia were joined during late Precambrian (Storey et al. 685).
B. 100-105 ma.: Antarctica begins to separate from India; period of rapid sea-floor spreading until
80 ma. in Atlantic and Pacific oceans (proven by magnetic patterns) (Windley 161)
C. 85 ma.: separation of Antarctica and Australia begins at rate of only a few mm. per year
("Antarctic Geology")
D. 40 Ma.: formation of Antarctic ice sheet due global climate change caused by mountain uplift and
volcanism ("Antarctica- The Dynamic...").
E. 30 ma.: complete separation of Antarctica and Australia ("Antarctic Geology")
separation of Antarctica and South America
F. breakup of continents away from Antarctica important because this allowed for the development
of a circum-polar ocean current, which regulates sea temperature today (Windley 161).
Works Consulted
Windley, Brian F. The Evolving Continents. (2nd Edition). New York: John Wiley & Sons, 1984.