Shallow water foraminifera of ODP Hole 133-821A@en

Reworked shallow-water foraminifers that settled on the upper slope of the central Great Barrier Reef at Site 821 (water depth, 212.6 m) were used as indicators of the paleoclimatic and paleoenvironmental conditions that have controlled the Pleistocene evolution of the adjacent platform. Throughout the 400-m-thick sequence drilled, the nature, composition, and distribution of the shallow-water foraminiferal assemblages studied indicate that (1) all the species recorded are at present living in diverse tropical, reef-related areas of the Indo-Pacific and Atlantic provinces; (2) the composition of the microfaunal taphocoenoses is almost identical between the different stratigraphic intervals studied and the modern Great Barrier Reef environments; (3) inner-neritic, tropical environments have continued to develop since the middle Pleistocene; (4) high- to moderate-energy platform edges occurred repeatedly throughout Pleistocene time. These factors may suggest that, since the beginning of the Pleistocene, several reef-like tracts have grown successively on the central area of the northeastern Australian shelf edge. These tracts probably had a sufficiently evolved morphological zonation to act as shelters for foraminiferal biocoenoses of high species diversity.以采自大堡礁（Great Barrier Reef）中部821站位（水深212.6 m）上斜坡沉积物中的再沉积浅水有孔虫（shallow-water foraminifers）作为指示物，用以反演控制毗邻台地更新世演化的古气候与古环境条件。本次对该站位钻探获得的400米厚沉积序列展开分析，所研究的浅水有孔虫组合的特征、组成与分布模式表明：（1）本次记录的所有物种目前均栖息于印度-太平洋与大西洋生物地理大区的各类热带礁体相关海域；（2）不同地层间隔中的微体化石埋藏群（microfaunal taphocoenoses）组成，与现代大堡礁的沉积环境特征几乎完全一致；（3）自更新世中期以来，热带内陆架环境持续发育；（4）更新世时期反复出现中-高能台地边缘环境。上述研究结果表明，自更新世伊始，澳大利亚东北陆架边缘的中部区域曾先后发育多处类礁体带。这类礁体带大概率具备足够成熟的地貌分带结构，可作为高物种多样性有孔虫生物群（biocoenoses）的栖息庇护场所。