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Miocene cold seeps faunas and carbonates from Barbados
In: Cahiers de Biologie Marine. Station Biologique de Roscoff: Paris. ISSN 0007-9723; e-ISSN 2262-3094, meer
Ook verschenen in:(1998). Proceedings of the First International Symposium on Deep-Sea Hydrothermal Vent Biology: Funchal, Madeira, Portugal 20-24 October 1997. Cahiers de Biologie Marine, 39(3-4). Station Biologique de Roscoff: Roscoff. 219-392 pp., meer
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| Abstract |
Barbados represents a subaerial exposure of the crestal zone of the Barbados accretionary prism, on the eastern margin of the Caribbean tectonic plate (Olu, et al., 1997). Erosion of the Pleistocene reef cap in NE Barbados exposes two Eocene-Miocene aged structural units: the accretionary Basal Complex, and the overlying pelagic Oceanic Series oozes. These units are everywhere in fault contact and overlap in depositional ages. Westward (arcward) migration of the western margin of the accretionary prism caused contraction and uplift of the outer Grenada Foreare Basin strata, emplacing the Oceanics as allochthonous backthrust nappes overriding the crest of the accretionary complex (Torrini, et al., 1985; Speed, 1990). These two units are separated by a major tectonic unit, the sub-Oceanic fault cone (SOFZ of Torrini, et al., 1985), a detachment surface along which fluid migration from dewatering of the accretionary prism appears to have been concentrated (Torrini, et al., 1990). The SOFZ is a laterally continuous zone 3-20 m thick, the central zone of which was apparently the 'surface' of greatest displacement. Fluid migration and authigenic, methane-derived carbonate precipitation within the SOFZ were apparently genetically related to the emplacement of the Oceanic nappes and the late intraprism contraction. Fluid migration was syn- to early post-faulting (early Miocene), with authigenic carbonates locally cross-cutting and replacing foliated fault zone rocks (Torrini, et al., 1990). The authigenic carbonates have yielded fossil cold seep faunas and carbonate chimneys. The material examined from Bath Cliffs, consists of both in situ specimens and eroded beach cobbles, whereas at Windy Hill, Belleplaine and Morgan Lewis the carbonates occur as ex situ clitter, either as 'remaine' horizons from long-eroded fault zones previously existing at higher structural levels, or eroded from buried fault zones. Specimens have also been collected at Coconut Grove, from the Joe's River mdlange, a sandy, organic-rich mudstone containing large angular exotic blocks. This extensive mAlange is believed to be a massive diapiric structure, intruded into surrounding strata post-nappe emplacement (Speed, 1990). |
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