Early Mesozoic Reef Evolution and Recoveries from Mass Extinctions

9614501 Stanley该项目的主要重点和目标是研究北美西部移位地体中三叠纪和侏罗纪珊瑚礁的演化以及珊瑚礁动物群的演化。第二个目标是关于保留的动物和陆地动物在特提斯珊瑚礁恢复中的可能作用。珊瑚、海绵和问题珊瑚是主要的珊瑚礁生物，它们是在大灭绝之后进化而来的，现在在特提斯群岛得到了广泛的认可。科迪勒拉的大多数礁体沉积已被地体形成和增生的动力构造过程所破坏。然而，新的研究发现了十几个保存完好的关键遗址，可以进行详细的研究。这个为期三年的项目将集中研究这些地点的动物群。被研究的陆地动物出现在火山序列中，这些火山序列被解释为在地理上远离特提斯的古代火山岛。对特提斯群岛中生代早期礁石动物群的广泛研究未能证实保留类群的存在。然而，美洲的情况尚未得到充分审查。该项目结合了对北美西部中生代早期遗址的实地、实验室和博物馆研究，并与特提斯珊瑚礁进行了比较，以评估地层中珊瑚礁分类群在珊瑚礁进化中发挥重要作用的观点。记录具有重要生物地层学意义的微化石，特别是牙形刺，是该项目的重要组成部分。本课题将由一名博士后助理研究，他将从珊瑚礁遗址中检索和研究牙形刺和其他微化石，并利用所得的生物地层学数据来提高定年和时间地层比较与特提斯的准确性。加拿大野外地质学家对珊瑚礁化石的初步收集显示，珊瑚礁动物群中可能含有二叠纪和三叠纪遗留的分类群——在影响该地区的毁灭性大灭绝之后，以前认为在特提斯灭绝的属和物种。除了证实了“拉撒路效应”之外，这些仅局限于西太平洋地体的发现，暗示了地体作为二叠纪和三叠纪特提斯珊瑚礁分类群优先生存的避难所的想法。火山岛作为避难所的想法在文献中根深蒂固，但它主要是推测性的，在很大程度上没有坚实的领域和分类基础。因此，该项目寻求收集新的数据，这些数据与现有的大量特提斯数据库相结合，为评估特提斯以外珊瑚礁生态系统的生存和恢复提供了具体的基础。来自火山地体的早中生代礁动物群可能包含特提斯中没有的古生物记录。从特定的地层对三叠纪和侏罗纪珊瑚礁动物群进行细致的分类和实地研究，结合对特提斯和非特提斯分类群的年龄和古地理分布的图解，将对证实或驳斥这一观点具有重要意义。由此产生的新数据肯定会扩大对特提斯以外珊瑚礁进化的认识，为与特提斯动物群的比较提供更强有力的基础。

9614501 Stanley The principal focus and goal of this project is to study the evolution of Triassic and Jurassic reefs and the evolution of reef faunas in displaced terranes of western North America. A secondary goal concerns holdover faunas and possible roles of terrane faunas in reef recoveries in the Tethys. Corals, sponges and problematica are the principal reef organisms which evolved after major mass extinctions now widely recognized in the Tethys. Most reef deposits of the Cordillera have been destroyed by dynamic tectonic processes of terrane formation and accretion. However new research has uncovered a dozen key sites where preservation is sufficient to permit detailed study. This three-year project will concentrate on faunas from these sites. The terrane faunas to be investigated occur in volcanic sequences interpreted to have been ancient volcanic islands geographically remote from the Tethys. Extensive studies of early Mesozoic reef faunas of the Tethys have failed to confirm the presence of holdover taxa. However the situation in the Americas has not been fully examined. The project combines field, laboratory and museum studies of early Mesozoic sites in western North America and comparisons with Tethyan reefs to assess the idea that reef taxa in terranes played an important role in reef evolution. Documentation of biostratigraphically important microfossils, particularly conodonts, is an important element of the project. This topic will be investigated with a post-doctoral research associate who will retrieve and study conodonts and other microfossils from reef sites and use the resulting biostratigraphic data to improve the accuracy of dating and time-stratigraphic comparisons with the Tethys. Preliminary collections of reef fossils made by field geologists in Canada have revealed reef faunas containing possible Permian and Triassic holdover taxa--genera and species previously thought extinct in the Tethys following the devastating mass extinctions affecting th at region. In addition to confirming the "Lazarus effect", these discoveries, confined exclusively to western Pacific terranes, hint at the idea that terranes functioned as refuges for preferential survival of Permian and Triassic Tethyan reef taxa. The idea of volcanic islands as refuges is firmly implanted in the literature, but it is mostly speculative and largely without solid field and taxonomic base. This project therefore seeks to gather new data which, when combined with a voluminous Tethyan database now available, offers a concrete basis to assess ideas of survival and the recoveries of reef ecosystems outside the Tethys. It is possible that early Mesozoic reef faunas from volcanic terranes contain a paleontoligical record not represented in the Tethys. Careful taxonomic and field study of Triassic and Jurassic reef faunas from specific horizons, combined with graphic plotting of age and paleogeographic distributions of Tethyan and non-Tethyan taxa, will be important in confirming or refuting the idea. The resulting new data is certain to expand knowledge of reef evolution outside the Tethys, adding a stronger basis for comparisons with Tethyan faunas.