Geologic composition of Antarctica
The
geology of Antarctica
covers the
geological
development of the continent through the
Archean
,
Proterozoic
and
Phanerozoic
eons
.
The geological study of
Antarctica
has been greatly hindered by the fact that nearly all of the continent is continuously covered with a thick layer of ice. However, techniques such as
remote sensing
have begun to reveal the structures beneath the ice.
Geologically, West Antarctica closely resembles the
Andes
of
South America
.
[1]
[
page needed
]
The
Antarctic Peninsula
was formed by uplift and
metamorphism
of sea-bed sediments during the late
Paleozoic
and the early
Mesozoic
eras. This sediment uplift was accompanied by
igneous
intrusions and
volcanism
. The most common rocks in West Antarctica are
andesite
and
rhyolite
volcanics formed during the Jurassic Period. There is also evidence of volcanic activity, even after the ice sheet had formed, in
Marie Byrd Land
and
Alexander Island
. The only anomalous area of West Antarctica is the Ellsworth Mountains region, where the
stratigraphy
is more similar to the eastern part of the continent.
The
West Antarctic Rift System
, a major active
rift valley
, lies between
West
and
East Antarctica
. Its major phase of rapid, broad extension occurred in Cretaceous time, and involved the action of both
normal and strike slip faults
within West Antarctica and contiguous
Zealandia
.
[2]
The rift is still active with slow movement of West Antarctica away from East Antarctica.
[3]
East Antarctica is geologically very old, dating from the
Precambrian
, with some rocks formed more than 3 billion years ago. It is composed of a
metamorphic
and
igneous
platform which is the basis of the
continental shield
. On top of this base are various more modern rocks, such as
sandstones
,
limestones
, coal and
shales
laid down during the Devonian and Jurassic periods to form the Transantarctic Mountains. In coastal areas such as
Shackleton Range
and
Victoria Land
some
faulting
has occurred.
More than 170 million years ago, Antarctica was part of the
supercontinent
Gondwana
. Over time Gondwana broke apart and Antarctica as we know it today was formed around 35 million years ago.
History of study
[
edit
]
The frozen continent of Antarctica was the last continent humanity set foot on. The first documented landings made below the
Antarctic Circle
took place in 1820, when Admiral
Fabian Gottlieb von Bellingshausen
and the crew of the
Vostok
and
Mirny
, as part of the
Russian Antarctic Expedition
, made land at
Peter I Island
and
Alexander Island
.
Various explorers launched expeditions into the south polar region to assess its economic potential. Consequently, scientific research was a rather marginalized endeavour. The first person to report a fossil in the Antarctic was American naturalist
James Eights
in 1829, who landed probably on
King George Island
and found a fossilized log measuring 2.5 ft (0.76 m) in length and 4 in (100 mm) in diameter. Eights left the fossil where he found it, rather than collecting and formally describing it.
The
Ross expedition
led by Captain
James Clark Ross
, from 1839 to 1842, discovered several Antarctic islands which are now known to be incredibly rich in fossils, most notably
Seymour Island
and
Cockburn Island
. Though he or his crew may have stumbled upon fossil material, they did not make note of it.
Much later, Captain
Carl Anton Larsen
and the crew of the
Jason
landed on Seymour Island over the summer of 1892 to 1893. He and his crew collected namely fossil shells, and Larsen's fossils (his crew traded theirs for tobacco) would eventually reach
University of Oslo
, and be formally described (a first for Antarctic fossils) by British paleontologists George Sharman and
Edwin Tulley Newton
in 1894. Larsen is most commonly accredited with being the first to collect an Antarctic fossil.
Sharman and Newton studied nine specimens, of which two are
conifer
wood fragments, and seven are seashells. Of the shells, they classified five into
Cucullaea donaldi
; one into either "
Cytherea
"
antarctica
,
Crassatella
, or
Donax
(now
Eurhomalea antarctica
); and one to
Natica
.
[8]
Though paleontological work continued thereafter, the scientific exploration of Antarctica would come to the forefront only after the
Antarctic Treaty System
was put into effect after 1961, establishing the continent as a nature preserve for solely scientific endeavours, barring all onland commercial activity. Antarctica's paleontology and geology have expanded since then, but studying them is fraught with danger from extreme weather, deep crevasses, and
avalanches
.
Archean
[
edit
]
The
East Antarctic Shield
's oldest rocks include the Napier Complex, which outcrops in the
Napier Mountains
. These rocks are associated with the Napier
orogeny
and early stages of crustal formation (4000
Ma
) in the
Archean
. The
Vestfold Hills
granulites
are also Archaean.
[10]
[11]
Proterozoic
[
edit
]
The
Mawson craton
of
East Antarctica
and
Australia
preserves evidence of
tectonic
activity from the
Archean
through the
Mesoproterozoic
in the
Terre Adelie
,
King George V Land
and the
Miller Range
of the central
Transantarctic Mountains
.
[12]
The
Late Proterozoic
Rayner Complex outcrops in Enderby Land and western
Kemp Land
. The
Rauer Islands
terrane
, composed of the Rauer Group granulite gneisses, are Late Proterozoic (1106 Ma). Numerous
mafic
dykes
are present in the Vestfold Hills and Napier Complex, and were emplaced between about 1200 to 1400 Ma. Massive
charnockite
bodies are present in the East Antarctica complex Proterozoic mobile belts, indicating a
batholith
intruded the
supracrustal
basement
gneiss
around 1000 Ma. In the
Borg Massif
region of western
Dronning Maud Land
, Archaean granites are overlain by the Proterozoic Ritscherflya
Supergroup
. This supergroup is a sedimentary-volcanic sequence, in which the sedimentary Schumacherfjellet
Formation
and Hogfonna Formation are
intruded
by the
Grunehogna
and Kullen
mafic
sills
(838 Ma). The
basaltic
lavas
of the Straumsnutane Formation (821 Ma) is the uppermost unit within the supergroup. To the east of the Ritscherflya Supergroup, lies the Proterozoic
metamorphic
terrane
of H.U. Sverdrupfjella, which is composed of para- and
orthogneisses
. The
Sør Rondane Mountains
are underlain by Late Proterozoic metamorphic rocks of the Teltet-Vengen Group and the Nils Larsen Group gneisses, which are intruded by latest Proterozoic to Early
Paleozoic
plutonic rocks
and dykes. Eastern Queen Maud Land includes the Late Proterozoic Lutzow-Holm Complex of gneisses and granitic and
granodioritic
migmatic
rocks, and the Yamato-Belgica Complex of
syenite
intrusions and low-pressure type metamorphism. These complexes are west of the Archaean Napier and Proterozoic Rayner complexes in Enderby Land.
Precambrian
gneisses,
anorthosites
, charnockites, and
amphibolites
characterize the
Schirmacher Hills
and
Wohlthat Mountains
in central Queen Maud Land.
[10]
[11]
[13]
[14]
[15]
[16]
[17]
[18]
[19]
Deposition during the
Precambrian
occurred in deep marine
basins
along the Pacific margin of Gondwana, the location of the present-day
Transantarctic Mountains
. These basin depositions were mainly deep-sea
submarine fans
. Key
strata
include the
Turnpike Bluff
Formation
, the Beardmore Group, and the Skelton Group. The
Beardmore orogeny
occurred during the Late Proterozoic, and is recognized in the central Transantarctic Mountains, with Cambrian
limestones
unconformably overlying deformed strata. Associated igneous activity resulted in
batholiths
(620 Ma) and
pyroclastics
(633 Ma). These pyroclastics overlie
argillite
-graywacke sequences in Queen Maud Land, the
Horlick Mountains
, and the
Thiel Mountains
.
[11]
: 32, 43?44
Paleozoic
[
edit
]
A
carbonate platform
developed along the palaeo-Pacific margin of Gondwana during the
Cambrian
, depositing the
Shackleton Limestone
on top of the Late Proterzoic
argillaceous
turbidite
Goldie Formation. The
Ross orogeny
, during the early
Paleozoic
(Cambro-
Ordovician
),
folded
the Transantarctic Mountains along the margin of Gondwana, with associated metamorphism, and granitic batholith intrusions. Noted Cambrian-Ordovician outcrops include the Urfjell Group, Blaiklock Glacier Group, Heritage Group in the
Ellsworth Mountains
, Byrd Group, and the Skelton and Koettlitz groups.
Silurian
-
Devonian
rocks outcrop in the Transantarctic, Ellsworth and
Pensacola Mountains
, and include the Neptune Group, Horlick Formation, the Crashsite Quartzite, and the Taylor Group within the
Beacon Supergroup
.
[11]
: 32?33, 44?47
[20]
[21]
During the
Late Paleozoic icehouse
, Antarctica was positioned over the
South Pole
while connected with the rest of
Pangea
. Antarctica underwent submergence and glaciation, and up to 375 m of
Carboniferous
and
Permian
glaciogenic rocks were deposited. This includes the Pagoda Formation within the Victoria Group of the Beacon Supergroup, a
diamictite
, sandstone and
shale
, within the Transantarctic Mountains.
[11]
: 46
[22]
During the
Cambrian
period, Gondwana had a mild climate. West Antarctica was partially in the northern hemisphere, and during this period large amounts of
sandstones
,
limestones
and
shales
were deposited. East Antarctica was at the equator, where sea-floor
invertebrates
and
trilobites
flourished in the tropical seas. By the start of the Devonian period (416 Ma) Gondwana was in more southern latitudes and the climate was cooler, though fossils of land plants are known from this time.
Sand
and
silts
were laid down in what is now the
Ellsworth
,
Horlick
and
Pensacola Mountains
.
Glaciation
began at the end of the Devonian period (360 Ma) as Gondwana became centered on the
South Pole
and the climate cooled, though flora remained. During the Permian period the plant life became dominated by fern-like plants such as
Glossopteris
, which grew in swamps. Over time these swamps became deposits of coal in the Transantarctic Mountains. Towards the end of the Permian period continued warming led to a dry, hot climate over much of Gondwana.
[1]
[
page needed
]
Mesozoic
[
edit
]
Pangea began to break up during the
Triassic
, while Gondwana moved northward taking Antarctica way from the South pole region. Subduction continued along the Pacific margin, and Triassic strata was deposited along the Transantarctic Mountains and the Antarctic Peninsula, including the Trinity Peninsula Group, the Legoupil Formation, and continued deposition of the Victoria Group within the Beacon Supergroup.
[11]
: 48?51
Gondwana rifting in the
Middle Jurassic
resulted in voluminous
tholeiitic magmtic activity
throughout the Transantarctic Mountains and the Antarctic Peninsula. By the
Late Jurassic
, the peninsula was a narrow magmatic arc, with
back-arc basins
and
fore-arc basins
, and represented by the Antarctic Peninsula Volcanic Group, and this activity continued into the
Early Cretaceous
. Antarctica was separated from Australia by the Early Cretaceous (125 Ma), and from New Zealand by the Late Cretaceous (72 Ma).
[11]
: 33?35, 43, 49?57
Cenozoic
[
edit
]
Antarctica was separated from South America at the
Drake Passage
by the
Miocene
, becoming isolated geologically and thermal isolation resulted in a colder climate while the continent was centered at the South Pole. Large ice sheets were present by the Middle-
Late Eocene
[11]
: 43, 54?57, 226
See also
[
edit
]
References
[
edit
]
- ^
a
b
Stonehouse, B., ed. (June 2002).
Encyclopedia of Antarctica and the Southern Oceans
. John Wiley & Sons.
ISBN
978-0-471-98665-2
.
- ^
Siddoway, 2008
- ^
Granot, 2013
- ^
Sharman, G.;
Newton, E. T.
(1895).
"Note on some Fossils from Seymour Island, in the Antarctic Regions, obtained by Dr Donald"
.
Transactions of the Royal Society of Edinburgh
.
37
(4): 707?709.
doi
:
10.1017/s0080456800032798
.
S2CID
130334778
.
- ^
a
b
Kuehner, S.M.; Green, D.H. (1991). Thomson, M.R.A.; Crame, J.A.; Thomson, J.W. (eds.).
Crustal development: the craton, in Geological Evolution of Antarctica
. Cambridge: Cambridge University Press. pp. 1?2.
ISBN
978-0-521-37266-4
.
- ^
a
b
c
d
e
f
g
h
Anderson, John (2010).
Antarctic Marine Geology
. Cambridge: Cambridge University Press. pp. 30?32.
ISBN
978-0-521-13168-1
.
- ^
Fitzsimmons, 2003
- ^
Young, D.N.; Ellis, D.J. (1991). Thomson, M.R.A.; Crame, J.A.; Thomson, J.W. (eds.).
The intrusive Mawson charnockites: evidence of a compressional plate margin setting of the Proterozoic mobile belt of East Antarctica, in Geological Evolution of Antarctica
. Cambridge: Cambridge University Press. pp. 25?31.
ISBN
978-0-521-37266-4
.
- ^
Krynauw, J.R.; Watters, B.R.; Hunter, D.R.; Wilson, A.H. (1991). Thomson, M.R.A.; Crame, J.A.; Thomson, J.W. (eds.).
A review of the field relations, petrology and geochemistry of the Borgmassivet intrusions in the Grunehogna province, western Dronning Maud Land, Antarctica, in Geological Evolution of Antarctica
. Cambridge: Cambridge University Press. pp. 33?39.
ISBN
978-0-521-37266-4
.
- ^
Groenewald, P.B.; Hunter, D.R. (1991). Thomson, M.R.A.; Crame, J.A.; Thomson, J.W. (eds.).
Granulites of northern H.U. Sverdrupfjella, western Dronning Maud Land: metamorphic history from garnet-pyroxene assemblages, coronas and hydration reactions, in Geological Evolution of Antarctica
. Cambridge: Cambridge University Press. pp. 61?66.
ISBN
978-0-521-37266-4
.
- ^
Shiraishi, K.; Asami, M.; Ishizuka, H.; Kojima, H.; Kojima, S.; Osanai, Y.; Sakiyama, T.; Takahashi, Y.; Yamazaki, M.; Yoshikura, S. (1991). Thomson, M.R.A.; Crame, J.A.; Thomson, J.W. (eds.).
Geology and metamorphism of the Sør Rondane Mountains, East Antarctica, in Geological Evolution of Antarctica
. Cambridge: Cambridge University Press. pp. 77?82.
ISBN
978-0-521-37266-4
.
- ^
Hiroi, Y.; Shiraishi, K.; Motoyoshi, Y. (1991). Thomson, M.R.A.; Crame, J.A.; Thomson, J.W. (eds.).
Late Proterozoic paired metamorphic complexes in East Antarctica, with special reference to the tectonic significance of ultramafic rocks: the craton, in Geological Evolution of Antarctica
. Cambridge: Cambridge University Press. pp. 83?87.
ISBN
978-0-521-37266-4
.
- ^
Kaul, M.K.; Singh, R.K.; Srivastava, D.; Jayaram, S.; Mukerji, S. (1991). Thomson, M.R.A.; Crame, J.A.; Thomson, J.W. (eds.).
Petrographic and structural characterisitcs of a part of the East Antarctic craton, Queen Maud Land, Antarctica, in Geological Evolution of Antarctica
. Cambridge: Cambridge University Press. pp. 89?94.
ISBN
978-0-521-37266-4
.
- ^
Harley, S.L. (1991). Thomson, M.R.A.; Crame, J.A.; Thomson, J.W. (eds.).
Metamorphic evolution of granulites from the Rauer Group, East Antarctica: evidence for decompression following Proterozoic collision, in Geological Evolution of Antarctica
. Cambridge: Cambridge University Press. pp. 99?105.
ISBN
978-0-521-37266-4
.
- ^
Roland, N.W. (1991). Thomson, M.R.A.; Crame, J.A.; Thomson, J.W. (eds.).
The boundary of the East Antarctic craton on the Pacific margin, in Geological Evolution of Antarctica
. Cambridge: Cambridge University Press. pp. 161?165.
ISBN
978-0-521-37266-4
.
- ^
Rowell, A.J.; Rees, M.N. (1991). Thomson, M.R.A.; Crame, J.A.; Thomson, J.W. (eds.).
Setting and significance of the Shackleton Limestone, central Transantarctic Mountains, in Geological Evolution of Antarctica
. Cambridge: Cambridge University Press. pp. 171?175.
ISBN
978-0-521-37266-4
.
- ^
Miller, J.M.G.; Waugh, B.J. (1991). Thomson, M.R.A.; Crame, J.A.; Thomson, J.W. (eds.).
Permo-Carboniferous glacial sedimentation in the central Transantarctic Mountains and its palaeotectonic implications (Extended abstract), in Geological Evolution of Antarctica
. Cambridge: Cambridge University Press. pp. 205?208.
ISBN
978-0-521-37266-4
.
Works cited
[
edit
]
- Fitzsimmons, I.C.W (2003). "Proterozoic Basement Provinces of Southern and Southwestern Australia, and Their Correlation with Antarctica". In Masaru Yoshida, M.; B. F. Windley; S. Dasgupta (eds.).
Proterozoic East Gondwana: Supercontinent Assembly and Breakup
. Geological Society of London. pp. 93?130.
- Siddoway, Christine (2008). "Tectonics of the West Antarctic rift system: New light on the history and dynamics of distributed intracontinental extension". In Cooper, A.K.; Barrett, P.J.; Stagg, H.; Storey, B.; Stump, E.; Wise, W.; et al. (eds.).
Antarctica: A Keystone in a Changing World, Proceedings of the 10th International Symposium on Antarctic Earth Sciences
. Washington DC: National Academy of Sciences. pp. 91?114.
- Granot, R. (2013).
"Revised Eocene-Oligocene kinematics for the West Antarctic rift system"
.
Geophysical Research Letters
.
40
(2). American Geophysical Uniot: 279?284.
Bibcode
:
2013GeoRL..40..279G
.
doi
:
10.1029/2012GL054181
.
S2CID
39685708
.
- Stilwell, J.; Long, J. A. (2012).
Frozen in Time: Prehistoric Life in Antarctica
. CSIRO Publishing.
ISBN
978-0-643-09635-6
.
Further reading
[
edit
]
- Elliot, David H (1975).
"Tectonics of Antarctica: A Review"
(PDF)
.
American Journal of Science
. 275-A: 45?106
. Retrieved
2018-05-22
.
- Jacobs, Joachim; Bauer, Wilfried; Schmidt, Rainer (2004).
"Magnetic Susceptibilities of the different Tectono-Stratigraphic Terranes of Heimefrontfjella, Western Dronning Maud Land, East Antarctica"
(PDF)
.
Polarforschung
.
72
: 41?48
. Retrieved
2018-05-23
.
- Laird, M.G.; Mansergh, G.D.; Chappell, J.M.A. (1971).
"Geology of the Central Nimrod Glacier area, Antarctica"
.
New Zealand Journal of Geology and Geophysics
.
17
(3): 427?468.
Bibcode
:
1971NZJGG..14..427L
.
doi
:
10.1080/00288306.1971.10421939
. Retrieved
2018-05-22
.
- Myrow, Paul M.; Pope, Michael C.; Goodge, John W.; Fischer, Woodward; Palmer, Alison R. (2002).
"Depositional history of pre-Devonian strata and timing of Ross orogenic tectonism in the central Transantarctic Mountains, Antarctica"
(PDF)
.
GSA Bulletin
.
114
(9): 1070?1088.
doi
:
10.1130/0016-7606(2002)114<1070:DHOPDS>2.0.CO;2
.
S2CID
17130391
. Archived from
the original
(PDF)
on 2018-05-23
. Retrieved
2018-05-22
.
- Palmer, A.R.; Rowell, A.J. (1995).
"Early Cambrian trilobites from the Shackleton Limestone of the Central Mountains"
.
Journal of Paleontology Memoir
.
69
: 1?28.
doi
:
10.1017/S0022336000061424
.
S2CID
182206675
. Retrieved
2018-05-22
.
- Skovsted, Christian B.; Betts, Marissa J.; Topper, Timothy P.; Brock, Glenn A. (2015).
"The early Cambrian tommotiid genus
Dailyatia
from South Australia"
.
AAP Memoir
.
48
: 1?117
. Retrieved
2018-05-22
.
- Stump, Edmund; Gootee, Brian; Talarico, Franco (2006).
Tectonic Model for Development of the Byrd Glacier Discontinuity and Surrounding Regions of the Transantarctic Mountains during the Neoproterozoic ? Early Paleozoic
(PDF)
. Springer, Berlin, Heidelberg, New York. pp. 45?54
. Retrieved
2018-05-22
.
External links
[
edit
]
Maps
[
edit
]
- Geological map of Antarctica ? by Scientific Committee on Antarctic Research GeoMAP Action Group
- Geological map 1:25,000 - Heimefrontfjella / Dronning Maud Land Antarctica - Hanssonhorna (2008) - by Bauer, W; Jacobs, J.; Schmidt, R., RWTH Aachen University
- Geological map 1:25,000 - Heimefrontfjella / Dronning Maud Land Antarctica - Northern XU-Fjella (2008) - by Schmidt, R; Jacobs, J.; Bauer, W., Universitat Bremen
- Geological map 1:50,000 - Ford Ranges, western Marie Byrd Land (2016) - by Siddoway, C., scar.org
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