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The constant circulation of material in the forearc region (accretionary prism, forearc basin and trench) generates a mixture of igneous, metamorphic and sedimentary sequences. In general, there is an increase in metamorphic grade from trench to arc where highest grade (blueschist to eclogite) is structurally uplifted (in the prisms) compared ...
The trough itself is a forearc basin, which is a depression that develops in front of an island arc system. [2] The subducting plate releases fluids and sediments, which accumulate in the forearc basin. These sediments can be uplifted and incorporated into the island arc, contributing to its growth.
An older assumption that backstops of accretionary wedges dip back toward the arc, and that accreted material is emplaced below such backstops, is contradicted by observations from many active forearcs that indicate (1) backthrusting is common, (2) forearc basins are nearly ubiquitous associates of accretionary wedges, and (3) forearc basement ...
Weber Deep differs from other deep sea points in that Weber Deep is not a deep sea trench, but is a forearc basin, a deep abyssal plain. The slab detachment is at the east end of the deep. Weber Deep is the 16th deepest point in the Earth's oceans and seas. [1]
Forearc, active arc, and back arc are expressed differently on either side of these boundaries (see figure below). The forearc is that part of the arc system between the trench and the magmatic front of the arc and includes uplifted sectors of the forearc situated near the magmatic front, sometimes called the ‘frontal arc’.
The Cook Inlet Basin is a northeast-trending collisional forearc basin that stretches from the Gulf of Alaska into South central Alaska, just east of the Matanuska Valley. It is located in the arc-trench gap between the Alaska-Aleutian Range batholith and contains roughly 80,000 cubic miles of sedimentary rocks. [1]
The eastern boundary of the forearc basin was a volcanic arc, a chain of ancient volcanoes located where the Sierra Nevada is today. Batholiths and metamorphosed volcanic rocks in the Sierra Nevada are the geologic record of this volcanic arc.
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