Juxtaposed melanges: the result of polyphase tectonism in a forearc terrane
The Mona Complex (Late Precambrian) of Anglesey, North Wales, can be modeled as a disrupted forearc complex. There are two distinct melanges in this complex. The Gwna melange contains large scale olistostromal masses, disrupted sequences that preserve a ghost stratigraphy, local syn-depositional slump and slide deposits, and sequences of pillowed basalts and associated sediments. Deformation was gravity driven. This unit developed in a forearc on a previously passive continental margin. The Aethwy Schists is belt of metabasite blocks in a pelitic matrix. The belt is metamorphosed; metabasites show a glaucophanic assemblage superimposed on an actinolitic precursor assemblage. Structures in the blocks developed when the rocks were highly ductile; block margins are highly sheared and recrystallized. These contrasting melanges are juxtaposed in two ways. The Aethwy Schists were underplated to the overlying plate. They were uplifted into the forearc high and stratigraphically overlain by characteristic Gwna melanges. Secondly, these units were faulted together along the Berw fault, a structure located along the edge of the ancient forearc high. These melanges and their juxtaposition demonstrate that when subduction is prolonged or episodic or when a complex terrane is rejuvenated, melanges formed by contrasting mechanisms can be juxtaposed and should not be treated as a single chaotic body.
- Research Organization:
- Memphis State Univ., TN (USA)
- OSTI ID:
- 6594063
- Report Number(s):
- CONF-8510489-
- Journal Information:
- Geol. Soc. Am., Abstr. Programs; (United States), Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Vol. 17; ISSN GAAPB
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
580100 -- Geology & Hydrology-- (-1989)
580201* -- Geophysics-- Seismology & Tectonics-- (1980-1989)
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