Contradictory Trends in the History of Cenzoic Corals and Coral Reefs: Oceanographic Change and Biotic Response

[909485]杰克逊古生物学的一个基本问题涉及生物对地球历史上在不同背景下反复发生的环境扰动的反应的一致性。本研究项目的目的是记录新生代加勒比珊瑚礁群落在两个生物快速变化时期对古海洋条件变化的反应。在早中新世和早更新世期间，大量的珊瑚物种灭绝，在早中新世过渡期间，大量的珊瑚礁从加勒比海消失，直到早更新世灭绝之后才恢复。因此，构造珊瑚礁生态系统的区域发展与珊瑚物种多样性明显不相关。这一矛盾表明，这两个时期与交替的古海洋条件有关。一种模型提出在中新世早期从占优势的底栖生物生产力向浮游生物生产力的转变，然后在更新世期间回到更少营养的条件。我们将通过对珊瑚礁-珊瑚多样性变化模式的严格记录和对沉积物生物成分的区域分析来探索这一假设。晚渐新世至中中新世含珊瑚岩的暴露将沿着从北美海湾海岸延伸到迎风岛屿的东西样带进行研究。我们将收集大量新的珊瑚化石，以补充博物馆现有的藏品，并将编制一个新的物种数量数据库。该数据库将加入现有的晚新近纪数据，以确定北加勒比地区物种出现和消失的比率。异养和光养/混合营养生物对近岸沉积物的相对贡献为独立于珊瑚多样性的古生产力提供了一个替代指标。这将使用来自每个研究地点的岩性样本进行评估。

9909485JacksonA fundamental question in paleontology concerns the consistency of biotic responses to environmental perturbations that occur repeatedly but in different contexts in earth history. The aim of this research project is to document the response of Cenozoic Caribbean reef coral communities to changes in paleoceanographic conditions during two episodes of rapid biotic change. Large numbers of coral species became extinct during both the Early Miocene and Early Pleistocene, and extensive reef tracts disappeared from the Caribbean during the Early Miocene transition and did not return until after the Early Pleistocene extinction. Therefore, the regional development of constructional coral reef ecosystems is apparently not correlated with coral species diversity. This paradox suggests that these two episodes were associated with alternating paleoceanographic conditions. One model proposes a switch from predominant benthic to planktonic productivity during the Early Miocene followed by a switch back to more oligotrophic conditions during the Pleistocene. We will explore this hypothesis through rigorous documentation of the changing patterns of reef-coral diversity and by regional analysis of the biotic component of sediments.Exposures of Late Oligocene to Middle Miocene coral bearing rocks will be examined along an east-west transect extending from the gulf coast of North America to the windward isles. Large new collections of fossil corals will be made to supplement existing museum collections and a new database of species level occurrences will be compiled. This database will be added to the existing Late Neogene data to determine rates of species appearance and disappearance in the Northern Caribbean. The relative contribution of heterotrophic and phototrophic/mixotrophic organisms to near shore sediments provide a proxy for paleoproductivity that is independent of coral diversity. This will be evaluated using lithological samples from each of the study sites.