Alcyonarian spiculites as possible proxy climate archives: preliminary results

Abstract

Alcyonarian spiculite (KONISHI 1981) is a carbonate rock built by a few soft coral species, notably Sinularia minima VERSEVELDT 1971, Sinularia polydactyla (EHRENBERG 1834), Sinularia leptoclados (EHRENBERG 1834) (the latter two are common in the tropical Indo-Pacific) and possibly Lobophytum pauciflorum (EHRENBERG 1834) (PAULAY & BENAYAHU 1999). The corals excrete 1-3 mm long sclerites (also called spindles or spicules) of high Mg calcite from the base of the stalk which become cemented by marine cements as the coral grows upwards (Fig. 3, A, B). In the tropical Pacific Ocean pedestals up to 1.5 m high with living Sinularia colonies on top have been described in the literature and by eye witnesses (CAREY 1931, SCHUHMACHER 1997, R. KELLEY, written com. 2008). Spiculites were found in sediment cores as old as 7,500 years (KLEYPASS 1996, southern GBR). ACCORDI et al. (1989) reported Quaternary Alcyonarian spiculites from the coast of Somalia. The spicules (or sclerites) are cemented soon after deposition by several generations of aragonite and high-Mg calcite cements. X-ray analyses of sawn slabs of spiculite rock show that the spicules are arranged in layers and that density bands are present (Fig. 3, D). These bands may contain paleoclimate information enclosed in either cements or spicules or both, similar to hard corals