Early Ordovician Greenhouse to Late Ordovician Glacial Transition: Effect on the Cyclic Sedimentary Record, Kentucky-Virginia

9316057 Read This proposal request funds to study superior outcrops and the extensive core collections of Middle and Late Ordovician rocks in肯塔基州，以便我们可以将它们与早奥陶世地层进行比较，以寻找可能从早奥陶世温室时代的低振幅euclide变化到晚奥陶世冈瓦纳冰期期间可能发展的更高振幅euclide的地层学证据。 目前，我们有一个非常大的数据库，早奥陶世和中奥陶世岩石特征的温室条件，这将作为一个基础，比较年轻的单位。 我们建议逐层记录中晚奥陶世碳酸盐岩和页岩，这些碳酸盐岩和页岩似乎是在以风暴为主的斜坡上开发的，记录任何潮缘和浅水到深水的潮下带周期，它们的横向连续性程度，它们的堆叠模式以及与沉积序列和边界表面的关系。 我们还将检查周期的证据：1。长期气候变化; 2。短期出现的证据（包括古土壤、侵蚀面、稳定同位素剖面的负偏离和流星胶结作用）;如果冰川驱动的海平面振幅增加到晚奥陶世，所有这些可能会变得更加明显。 利用详细的区域旋回岩相剖面图，我们将确定沉积序列，并记录边界面与前陆盆地构造历史的关系和时间，包括外围凸起发育和沿着构造活动近缘的碎屑岩。 最后，我们将对旋回和沉积序列进行计算机模拟，以更好地约束构造作用、低频和高频地壳运动以及沉积物供给的作用。 定义温室的地层签名，全球冰川条件似乎持有的关键，未来更详细的全球气候细分的中生代比h的尝试。

9316057 Read This proposal request funds to study superb outcrops and the extensive core collections of Middle and Late Ordovician rocks in Kentucky so that we can compare them with the Early Ordovician strata, to search for the stratigraphic evidence of possible change from low amplitude eustasy of Early Ordovician greenhouse times to possible higher amplitude eustasy developed during Late Ordovician Gondwana glaciation. We presently have a very large data base on Early Ordovician and Middle Ordovician rocks characteristic of greenhouse conditions, that will serve as a basis for comparison with the younger units. We propose to log bed-by-bed the later Middle and Late Ordovician carbonates and shales which appear to have developed on storm-dominated ramps, documenting any peritidal and shallow to deeper water subtidal cycles, their degree of lateral continuity, their stacking patterns and relation to depositional sequences, and bounding surfaces. We will also examine the cycles for evidence of: 1. long term climate change and 2. evidence of short term emergence (including paleosols, erosion surfaces, negative departures of stable isotope profiles, and meteoric cementation); all these might become more pronounced if glacially driven sea level amplitudes increased into the Late Ordovician. Using detailed regional cross sections of cyclic lithofacies, we will define depositional sequences, and document the relationships and timing of bounding surfaces to the tectonic history of the foreland basin, including peripheral bulge development and prograding clastic rocks along the tectonically active proximal margin. Finally, we will computer model the cycles and the depositional sequences to better constrain the roles of tectonism, low- and high- frequency eustasy, and sediment supply. Defining the stratigraphic signature of greenhouse to global glacial conditions appears to hold the key for a future more detailed global climate subdivision of the Phanerozoic than h as been attempted.