Abstract

This is the second of a series concerning the accretionary complex that is exposed on the island of Barbados and is thought to represent the Lesser Antilles fore-arc at its structural high. Two principle tectonostratigraphic elements are present in the Bissex Hill area: a basal complex composed of east-northeast–striking, generally steeply dipping, fault-bound packages of terrigenous sandstones and mudstones (mostly turbidites), hemipelagic rocks and mélange; that complex is overlain by the Bissex Hill nappe, composed of calcareous pelagic rocks, crystalline limestone and foraminiferal arenite. Also present in the basal complex are smaller fault-bound packages, termed “micropackets,” composed of brecciated basal complex lithologies. Basal complex faults are cut by the Bissex Hill nappe, except on the southern margin of the Bissex Hill nappe where mélange and hemipelagic lithologies apparently have been faulted over the nappe rocks. This youngest faulting may be driven by Holocene and older mélange diapirism.

Structural evolution of terrigenous and probably hemipelagic rocks in basal complex fault-packages is characterized by coaxial deformation about southwest-trending axes. Mélange packages possibly experienced greater strain as evidenced by girdled fold axes and axial planes and foliations of constant orientation. Packet-bounding faults probably developed during early folding and probably represent surfaces against which packet contents contracted. Micropackets are the result of motions after the assembly of major packets, and are formed through fault imbrication and (or) diapiric injection.

Rocks of the Bissex Hill nappe experienced folding first about a north-trending axis, followed by folding about a southwest-trending axis and gentle folding on the entire nappe about an east-northeast–trending axis.

Deformation in the basal complex is thought to have occurred by progressive accretion of sediment packets. The Bissex Hill nappe is thought to represent a fore-arc basin complex thrust over the accretionary complex. Quartzose sandstones present in the Bissex Hill nappe that probably had their source in the basal complex indicate that the accretionary complex probably shoaled by the Miocene.

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