In deep water: a crinoid–brachiopod association in the Upper Oligocene of Antigua, West Indies

Abstract

Extant brachiopods and stalked crinoids are found together in the deeper waters of the Caribbean Sea. Analogous brachiopod/crinoid associations have been reported from diverse palaeoenvironments in the Neogene of the region. Studied examples include the Pleistocene of Jamaica (deeper water fore reef), and the Miocene of Jamaica (island slope chalks), Barbados (accretionary prism) and Carriacou (turbiditic siliciclastic shelf). Comparison with analogous modern environments indicates deposition in 150+m water depth. This association has now been extended back into the Late Oligocene. Crinoids and brachiopods both occur in the Antigua Formation of Antigua; both occur high in the formation, implying deeper water in this retrograde succession. They have received little attention from systematists, although the brachiopods Cistellarcula dubia Cooper and Tichosina foresti Cooper have previously been described from the Antigua Formation; to these, we add Cistellarcula sp., Argyrotheca sp. and Tichosina sp. At Half Moon Bay in southeast Antigua, high in the Antigua Formation, we have found columnals of isocrinid crinoids (cf. Isocrinus sp.) associated with rare brachiopods (Terebratulina sp.) in island slope deposits. These taxa provide independent evidence for the deeper water aspect of this part of the Antigua Formation, in beds that also yield large, thin-walled fossil sponges.