ANATOMY OF A PLEISTOCENE LAGOONAL STAGHORN REEF, SANTA MARTHA INNER BAY, CURAçAO (MIS 5e)

Santa Martha Bay is an inner bay on the leeward side of Curaçao, Netherlands Antilles, connected to the open sea by a narrow channel incised through Quaternary reef carbonates during lowstands. During the last interglacial (MIS 5e, 125ka) a luxuriant fringing reef developed as sea level rose 4 – 6 m above present sea level. Not only did this reef form a terrace surrounding the entire island, but it also developed within interior bays created by erosion of the basaltic core of Cretaceous age. A small island within Santa Martha inner bay provides an excellent exposure of the MIS 5e reef developed directly on the eroded igneous substratum to a thickness of about 6 m. Corals colonized the weathered basaltic substratum and are dominated by Acropora cervicornis, Montastraea nancyi, M. annularis, M. faveolata, Porites astreoides, Siderastrea siderea, Diploria spp., and others. Massive corals are preserved in growth position while A. cervicornis is fragmented but likely untransported. Some colonies of the organ-pipe M. nancyi extend at least 3 m from the base of the reef. Toward the landward side, the reef gives way to a burrowed calcarenitic facies that dips beneath the present bay. In vertical sequence there is a transition from basaltic substratum to a thin interval with reworked basaltic clasts then to subtidal corals, indicating rapid flooding. Further analysis of the coral growth rates of Montastraea during this warming period are being completed as well as isotopic analysis of articulated bivalves found abundantly throughout the vertical sequence. The significance of this site is the outstanding diversity of coral abundance and growth in a protected inner bay during an interglacial highstand and warming during which Caribbean sea surface temperatures (SST) have been estimated at 1.5^o C higher than present. Despite popular perceptions that corals cannot prosper during warming SST, Santa Martha Bay demonstrates high productivity and rich diversity of a reef that not only survived but also flourished in a wave-protected environment that included warming SST, probable ocean acidification, and sea level rise. Further study will analyze several other sites all of which demonstrate high abundance, diversity and growth during MIS 5e of the Pleistocene on the island of Curacao, N. A.