KENORLAND was one of the earliest known supercontinents on
Swarms of volcanic dikes and their paleomagnetic orientation as well
as the existence of similar stratigraphic sequences permit this
reconstruction . The core of Kenorland, the Baltic/Fennoscandian
Shield , traces its origins back to over 3.1 Ga. The Yilgarn Craton
* 1 Formation * 2 Breakup or disassembly * 3 References * 4 Bibliography
Life timeline view • discuss • edit -4500 — – -4000 —
– -3500 — – -3000 — – -2500 — – -2000 — – -1500 —
– -1000 — – -500 — – 0 — _WATER _ Single-celled
life _PHOTOSYNTHESIS _ EUKARYOTES Multicellular
life LAND LIFE DINOSAURS MAMMALS FLOWERS ←
P r o t e r o z o i c
n Pongola Huronian
Cryogenian Andean Karoo Quaternary
Axis scale : millions of years .
Orange labels: known _ICE AGES_.
Also see: _
Kenorland was formed around 2.72 billion years ago (2.72 Ga) as a result of a series of accretion events and the formation of new continental crust.
The accretion events are recorded in the greenstone belts of the
BREAKUP OR DISASSEMBLY
Paleomagnetic studies show
Kenorland was in generally low latitudes
until tectonic magma -plume rifting began to occur between 2.48 Ga and
2.45 Ga. At 2.45 Ga the
Baltic Shield was over the equator and was
Laurentia (the Canadian Shield), and formed a unity with
both the Kola and
The geological time period surrounding the breakup of Kenorland is thought by many geologists to be the beginning of the transition point from the deep-mantle-plume method of continent formation in the Hadean to Early Archean (before the final formation of the Earth's inner core ) to the subsequent two-layer core-mantle plate tectonics convection theory. However, the findings of an earlier continent, Ur , and a supercontinent of around 3.1 Gya, Vaalbara , indicate this transition period may have occurred much earlier.
The Kola and
This implies that at 2.45 Gya there was no longer a supercontinent and by 2.515 Gya an ocean existed between the Kola and Karelia cratons. Also, there is speculation based on the rift margin spatial arrangements of Laurentia, that at some time during the breakup, the Slave and Superior cratons were not part of the supercontinent Kenorland, but, by then may have been two different Neoarchaean landmasses (supercratons) on opposite ends of a very large Kenorland. This is based on how drifting assemblies of various constituent pieces should flow reasonably together toward the amalgamation of the new subsequent continent. The Slave and Superior cratons now constitute the northwest and southeast portions of the Canadian Shield , respectively.
The breakup of Kenorland was contemporary with the Huronian glaciation which persisted for up to 60 million years. The banded iron formations (BIF) show their greatest extent at this period, thus indicating a massive increase in oxygen build-up from an estimated 0.1% of the atmosphere to 1%. The rise in oxygen levels caused the virtual disappearance of the greenhouse gas methane (oxidized into carbon dioxide and water).
The simultaneous breakup of
Kenorland generally increased continental
rainfall everywhere, thus increasing erosion and further reducing the
other greenhouse gas carbon dioxide. With the reduction in greenhouse
gases, and with solar output being less than 85% its current power,
this led to a runaway Snowball
* ^ _A_ _B_ Pesonen et al. 2003 , Abstract * ^ Halla 2005 , Introduction, p. 22 * ^ Mertanen 2004 , p. 190
* Arestova, N. A.; Lobach-Zhuchenko, S. B.; Chekulaev, V. P.;
Gus'kova, E. G. (2003). "Early Precambrian mafic rocks of the
Fennoscandian shield as a reflection of plume magmatism: Geochemical
types and formation stages" (PDF). _Russian Journal of Earth
Sciences_. 5 (3): 145–163. doi :10.2205/2003es000126 . Retrieved
March 12, 2016.
* Aspler, L. B.; Chiarenzilli, J. R.; Cousens, B. L.; Davis, W. J.;
McNicoll, V. J.; Rainbird, R. H. (1999). "Intracratonic basin
processes from breakup of
Kenorland to assembly of Laurentia: new
geochronology and models for Hurwitz Basin, Western Churchill
Province" (PDF). _Contributions to the Western Churchill NATMAP
Project; Canada-Nunavut Geoscience Office_. Retrieved March 12, 2016.
* Halla, J. (2005). "Neoarchean sanukitoids (2.74–2.70 Ga)". In
Halla, J.; Nironen, M.; Lauri, L. S.; Kurhila, M. I.; Käpyaho, A.;
Sorjonen-Ward, P.; Äikäs, O. _Eurogranites 2005:
Archean Granites and Related Rocks of the Finnish Precambrian_ (PDF).
University of Helsinki. Retrieved March 12, 2016.
* Mertanen, Satu (2004). _
Paleomagnetic Evidences for the Evolution
* v * t * e
Continents of the world
* HISTORICAL CONTINENTS
* _See also Regions of the world _ * _ Continental fragment _
* BOOK * CATEGORY
Links: ------ /wiki/Supercontinent /wiki/Earth /wiki/Archean