Paleoenvironmental significance of siliceous sponge spicules from Sites 627 and 628, Little Bahama Bank, Ocean Drilling Program Leg 101

Abstract

Siliceous sponge spicules occur in deposits of Oligocene to Miocene age from Sites 627 and 628, north of Little Bahama Bank, Bahamas. Previous studies of siliceous sponge spicules recovered from Deep Sea Drilling Project sites were used to indicate paleobathymetry, evidence of redeposited shallow-water material, and general stratigraphic position. The most obvious and potentially valuable aspect of siliceous spicule distribution is that the two main groups, tetraxons and triaxons (hexactinellids), are formed by sponges most abundant in shallow (0-400m) and deeper (>400-1000m) waters, respectively. The predominance of tetraxonal spicules in samples from Sites 627 and 628 suggests origin from, as well as deposition in, relatively shallow waters. The presence of triaxonal (hexactinellid) spicules in samples from Site 627 and the Oligocene of Site 628 indicates slightly deeper conditions and/or less influx of periplatform material during deposition of those intervals. -from Author