Wilson cycle

Wilson cycle
Fabirichter · CC BY-SA 4.0 · source
Name	Wilson cycle
Type	Geological cycle
First proposed	1960s
Proposer	John Tuzo Wilson
Related	Plate tectonics, Supercontinent cycle, Ocean basin

Wilson cycle

The Wilson cycle describes the sequence of opening and closing of ocean basins driven by plate motions, mantle dynamics, and continental interactions. It links episodes of rifting, seafloor spreading, subduction, and continental collision, integrating observations from paleogeography, stratigraphy, and geophysics. The concept connects the behavior of oceanic and continental plates from the scale of the Atlantic Ocean to the assembly of supercontinents such as Pangaea and Rodinia.

Introduction

The concept was proposed in the context of debates involving figures like John Tuzo Wilson, Harry Hess, Alfred Wegener, and W. Jason Morgan, and it draws on data from regions including the Atlantic Ocean, Indian Ocean, and Pacific Ocean. It synthesizes evidence from institutions such as the US Geological Survey, British Geological Survey, and universities like Harvard University and McGill University. The theory is central to interpretations by researchers at organizations including the Geological Society of America and the Royal Society. Key field areas include the East African Rift, the Iapetus Ocean realm, and the Tethys Ocean margins.

Stages of the Wilson cycle

Descriptions of the cycle often break it into stages recognized in case studies of basins like the North Atlantic Ocean and the South China Sea:

- Continental rifting and breakup as documented in studies of the East African Rift and the breakup of Gondwana. - Formation of narrow proto-oceans, exemplified by closure histories of the Iapetus Ocean and the Rheic Ocean. - Seafloor spreading creating mature ocean basins such as the Atlantic Ocean during the dispersal of Pangaea. - Subduction initiation at passive margins or intra-oceanic settings, recorded in the evolution of the Pacific Ocean margins and the Andes. - Ocean closure and continental collision seen in the formation of the Himalaya from India–Eurasia convergence and the assembly of Pangaea. - Post-collisional orogenic collapse and intracontinental rifting that preludes the next cycle, as in the Basin and Range Province and the breakup of Pannotia.

Seminal examples span timescales from the Paleogene opening of the South Atlantic to Neoproterozoic events associated with Rodinia.

Geological mechanisms and processes

Mechanisms invoked include mantle convection patterns studied at institutions like the Woods Hole Oceanographic Institution and the Scripps Institution of Oceanography, plume–plate interactions associated with the Deccan Traps and Siberian Traps, and slab pull forces documented in subduction zones off Japan and Chile. Processes involve lithospheric stretching, magmatism observed in provinces such as the Karoo Basin and the Canadian Shield, and metamorphism recorded in orogens like the Caledonides and the Alps. Geophysical tools from agencies like NASA and observatories such as the Lamont–Doherty Earth Observatory provide seismic tomography and gravity data that reveal mantle anomalies beneath regions including the African Superswell and Iceland.

Tectonic drivers include ridge push at spreading centers like the Mid-Atlantic Ridge, slab rollback in regions such as the Western Pacific, and continental rheology influenced by crustal composition in shields like the Fennoscandian Shield.

Evidence and examples

Evidence comes from seismic profiles across margins such as the Norwegian Continental Shelf and sedimentary records in basins like the Gulf of Mexico and the Permian Basin. Paleomagnetic reconstructions by groups at Columbia University and University of Cambridge track plate motions that closed oceans like the Tethys Ocean and opened oceans like the South Pacific. Geochronology using techniques developed at facilities like the Smithsonian Institution and the USGS National Center date magmatic suites in provinces such as the Sierra Nevada batholith and the Zagros metamorphic belts. Examples include the evolution of the Atlantic Ocean from Mesozoic rifting, the closure of the Iapetus Ocean forming the Caledonian Orogeny, and the complex subduction history around the Caribbean Plate.

Case studies from the Tasman Sea, the Red Sea, and the Gulf of Aden illustrate rift-to-drift transitions, while the collision between India and Eurasia exemplifies terminal collision and orogeny.

Implications for plate tectonics and supercontinent cycles

The cycle underpins models of supercontinent assembly and dispersal including Pangaea and Rodinia, informing hypotheses proposed at meetings of the International Union of Geological Sciences and publications in journals like those of the Geological Society of London. It affects interpretations of global sea level changes recorded in the Permian and Cretaceous strata, influences mantle convection models discussed at the American Geophysical Union meetings, and constrains paleoclimate reconstructions tied to Permian-Triassic and Cretaceous-Paleogene intervals. The framework guides exploration strategies by companies and agencies such as Chevron, BP, and national geological surveys in targeting hydrocarbon basins in regions including the North Sea and the Caspian Basin.

Historical development and proponents

Origins trace to debates in the mid-20th century involving John Tuzo Wilson, who synthesized ideas from Alfred Wegener and proponents of seafloor spreading like Harry Hess and Fred Vine. Later proponents and contributors include W. Jason Morgan, Kearey, K. C. Condie, S. M. Clarke, and researchers at institutions such as Stanford University, Oxford University, and Princeton University. Conferences at venues like the Royal Geographical Society and symposia of the American Association of Petroleum Geologists advanced the concept, with critical fieldwork from expeditions organized by the Challenger Society and the International Ocean Discovery Program.

Category:Geology