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

古生物学中的一个基本问题涉及生物对地球历史上反复发生但在不同背景下发生的环境扰动的反应的一致性。这一研究项目的目的是记录新生代加勒比海珊瑚礁群落在两个快速生物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，大量珊瑚物种灭绝，在早中新世过渡期间，加勒比海消失了大片珊瑚礁，直到早更新世灭绝后才恢复。因此，珊瑚礁生态系统的区域发展与珊瑚物种多样性没有明显的相关性。这一悖论表明，这两次事件与交替的古海洋条件有关。一种模型提出在中新世早期从主要的底栖生物生产力转变为浮游生物生产力，然后在更新世转变回更少营养的条件。我们将通过对珊瑚礁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说。我们将沿着从北美墨西哥湾海岸延伸到迎风小岛的东西横断面来研究晚渐新世到中中新世珊瑚岩石的暴露。将制作大量新的珊瑚化石收藏品，以补充博物馆现有的收藏品，并将汇编一个新的物种水平出现情况数据库。该数据库将被添加到现有的新近纪晚期数据中，以确定北加勒比海物种出现和消失的速度。异养和光养/混合营养生物对近岸沉积物的相对贡献提供了一个与珊瑚多样性无关的古生产力的指标。这将使用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.