Fragment of crust formed on one tectonic plate and accreted to another
In
geology
, a
terrane
(
;
[1]
[2]
in full, a
tectonostratigraphic
terrane
) is a
crust
fragment formed on a
tectonic plate
(or broken off from it) and
accreted
or "
sutured
" to crust lying on another plate. The crustal block or fragment preserves its distinctive geologic history, which is different from the surrounding areas?hence the term "exotic" terrane. The suture zone between a terrane and the crust it attaches to is usually identifiable as a
fault
. A sedimentary deposit that buries the contact of the terrane with adjacent rock is called an
overlap formation
. An igneous intrusion that has intruded and obscured the contact of a terrane with adjacent rock is called a
stitching pluton
.
The older usage of
terrane
described a series of related rock formations or an area with a preponderance of a particular rock or rock group.
Overview
[
edit
]
A tectonostratigraphic terrane is not necessarily an independent
microplate
in origin since it may not contain the full thickness of the
lithosphere
. It is a piece of
crust
that has been transported laterally, usually as part of a larger plate, and is relatively buoyant due to thickness or low density. When the plate of which it was a part
subducted
under another plate, the terrane failed to subduct, detached from its transporting plate, and accreted onto the overriding plate. Therefore, the terrane transferred from one plate to the other. Typically, accreting terranes are portions of
continental crust
which have
rifted
off another continental mass and been transported surrounded by oceanic crust, or they are old
island arcs
formed at some distant subduction zones.
A tectonostratigraphic terrane is a fault-bounded package of rocks of at least regional extent characterized by a geologic history that differs from that of neighboring terranes. The essential characteristic of these terranes is that the present spatial relations are incompatible with the inferred geologic histories. Where terranes that lie next to each other possess strata of the same age, it must be demonstrable that the geologic evolutions are different and incompatible. There must be an absence of intermediate
lithofacies
that could link the strata.
The concept of
tectonostratigraphic terrane
developed from studies in the 1970s of the complicated
Pacific Cordilleran
orogenic
margin of
North America
, a complex and diverse geological potpourri that was difficult to explain until the new science of plate tectonics illuminated the ability of crustal fragments to "drift" thousands of miles from their origin and fetch up, crumpled, against an exotic shore. Such terranes were dubbed "
accreted terranes
" by
geologists
.
It was soon determined that these exotic crustal slices had in fact originated as "suspect terranes" in regions at some considerable remove, frequently thousands of kilometers, from the
orogenic belt
where they had eventually ended up. It followed that the present orogenic belt was itself an accretionary collage, composed of numerous terranes derived from around the circum-
Pacific
region and now sutured together along major faults. These concepts were soon applied to other, older orogenic belts, e.g. the
Appalachian belt
of North America.... Support for the new hypothesis came not only from structural and lithological studies, but also from studies of faunal
biodiversity
and
palaeomagnetism
.
[3]
When terranes are composed of repeated accretionary events, and hence are composed of subunits with distinct history and structure, they may be called
superterranes
.
[4]
Tectonostratigraphic terranes
[
edit
]
Africa
Asia
Taiwan
Tibet
Australasia
Europe
Fennoscandia
North America
South America
References
[
edit
]
Citations
[
edit
]
- ^
"terrane"
.
Merriam-Webster.com Dictionary
. Retrieved
2022-10-27
.
- ^
"terrane"
.
Dictionary.com Unabridged
(Online). n.d
. Retrieved
2023-04-02
.
- ^
Carney, J. N. et al. (2000).
Precambrian Rocks of England and Wales
, (Geological Conservation Review Series, v. 20). UK: Joint Nature Conservation Committee.
ISBN
978-1861074874
.
- ^
"Terranes"
Archived
2004-12-12 at the
Wayback Machine
University of British Columbia
website
- ^
Schematic map of the Siberian craton showing boundaries of the craton and its terranes
- ^
a
b
c
d
e
f
g
Okaya, D.; Christensen, N.I.; Ross, Z.E.; Wu, F.T. (2016).
"Terrane?controlled crustal shear wave splitting in Taiwan"
.
Geophysical Research Letters
.
43
(2): 556?563.
Bibcode
:
2016GeoRL..43..556O
.
doi
:
10.1002/2015GL066446
.
- ^
a
b
c
d
e
f
Aitchison, J. C., Ali, J. R., and Davis, A. M. (2007) "When and where did India and Asia collide?"
Journal of Geophysical Research
, v.112, pp.1?19
- ^
a
b
c
d
e
f
g
h
Mortimer, N; Rattenbury, MS; King, PR; Bland, KJ; Barrell, DJA; Bache, F; Begg, JG; Campbell, HJ; Cox, SC; Crampton, JS; Edbrooke, SW; Forsyth, PJ; Johnston, MR; Jongens, R; Lee, JM; Leonard, GS; Raine, JI; Skinner, DNB; Timm, C; Townsend, DB; Tulloch, AJ; Turnbull, IM; Turnbull, RE (2014).
"High-level stratigraphic scheme for New Zealand rocks"
.
New Zealand Journal of Geology and Geophysics
.
57
(4): 402?419.
doi
:
10.1080/00288306.2014.946062
.
ISSN
0028-8306
.
- ^
Pharao, et al. (1996)
Tectonic map of Britain, Ireland & adjacent areas
UK:
British Geological Survey
- ^
a
b
c
d
Viola, G.; Henderson, I.H.C.; Bingen, B.; Hendriks, B.W.H. (2011).
"The Grenvillian?Sveconorwegian orogeny in Fennoscandia: Back-thrusting and extensional shearing along the 'Mylonite Zone'
"
.
Precambrian Research
.
189
(3?4): 368?88.
Bibcode
:
2011PreR..189..368V
.
doi
:
10.1016/j.precamres.2011.06.005
. Retrieved
22 August
2015
.
- ^
Cuthberta, S.J.; Carswellb, D.A.; Krogh-Ravnac, E.J.; Waind, A. (2000). "Eclogites and eclogites in the Western Gneiss Region, Norwegian Caledonides".
Lithos
.
52
(1?4): 165?195.
Bibcode
:
2000Litho..52..165C
.
doi
:
10.1016/s0024-4937(99)00090-0
.
- ^
a
b
c
Hild, Martha; Barr, Sandra (2015).
Geology of Nova Scotia
. Portugal Cove: Boulder Publications. p. 18.
ISBN
9781927099438
.
- ^
a
b
c
d
Miller, Brent (1997).
Geology, Geochronology, and Tectonic Significance of the Blair River Inlier, Northern Cape Breton Island, Nova Scotia
. Halifax: Dalhousie University. p. 260.
General bibliography
[
edit
]
- McPhee, John
(1981).
Basin and Range
. New York: Farrar, Straus and Giroux.
- McPhee, John
(1983).
In Suspect Terrain
. New York: Farrar, Straus and Giroux.
- McPhee, John
(1993).
Assembling California
. New York: Farrar, Straus and Giroux.
External links
[
edit
]
Look up
terrane
in Wiktionary, the free dictionary.