(Table 1) Accelerator mass spectrometer 14C age measurements on bryozoans (Celleporaria sp.), ODP Hole 182-1131B

Bryozoan reef mounds are common features in the geological record, occurring within mid-ramp, slope paleoenvironments, especially in Paleozoic carbonate successions, but until now have not been recorded from the modern ocean. Recent scientific drilling in the Great Australian Bight (Ocean Drilling Program Leg 182) has confirmed the existence of shallow subsurface bryozoan reef mounds in modern water depths of 200-350 m. These structures have as much as 65 m of synoptic relief, and occur both as single mounds and as mound complexes. They are unlithified, have a floatstone texture, and are rich in delicate branching, encrusting and/or nodular-arborescent, flat-robust branching, fenestrate, and articulated zooidal bryozoan growth forms. The muddy matrix is composed of foraminifers, serpulids, fecal pellets, irregular bioclasts, sponge spicules, and calcareous nannofossils. The 14C accelerator mass spectrometry dates of 26.6-35.1 ka indicate that the most recent mounds, the tops of which are 7-10 m below the modern seafloor, flourished during the last glacial lowstand but perished during transgressive sea-level rise. This history reflects changing oceanographic current patterns; strong upwelling during lowstands, and reduced upwelling and lowered trophic resources during highstands. Large specimens of benthic foraminifers restricted to the mounds confirm overall mesotrophic growth conditions. The mounds are similar in geometry, scale, general composition, and paleoenvironments to older structures, but lack obvious microbial influence and extensive synsedimentary cementation. Such differences reflect either short-term local conditions or long-term temporal changes in ocean chemistry and biology.

苔藓虫礁丘（Bryozoan reef mounds）是地质记录中常见的地质体，产出于缓坡中部、斜坡古环境，尤其常见于古生代碳酸盐岩地层序列，但迄今尚未在现代海洋中被发现。近期在大澳大利亚湾开展的大洋钻探计划（Ocean Drilling Program）第182航次科学钻探，证实了现代水深200~350米的浅表层存在苔藓虫礁丘。这些礁丘最大可达65米的总地形起伏，既可作为孤立丘体产出，也可形成丘体复合体。它们均未固结成岩，具有漂浮灰岩结构（floatstone texture），富含多种生长形态的苔藓虫群体，包括纤细分枝型、包覆型、结节状树状型、扁平粗壮分枝型、网孔型（fenestrate）以及铰接型个员型生长形态。其泥质基质由有孔虫、龙介虫、粪粒、不规则生物碎屑、海绵骨针及钙质超微化石组成。经碳14加速器质谱法测年，结果为26.6~35.1 ka，表明这些最新形成的礁丘（其顶部位于现代海底以下7~10米处）在末次冰期低海平面期繁盛，但在海侵海平面上升过程中消亡。这一演化历史反映了海洋流场格局的变化：低海平面期存在强上升流，而高海平面期上升流减弱、营养资源供给降低。仅分布于礁丘的大型底栖有孔虫标本证实了其整体处于中营养生长环境。该类礁丘在几何形态、规模、总体组成及古环境背景上与古老礁丘结构相似，但未表现出明显的微生物作用及广泛的同沉积胶结作用。这类差异要么反映了短期的局部环境条件变化，要么代表了海洋化学与生物学的长期演化。