Ichnology of the Bridge Creek Limestone: Evidence for Temporal and Spatial Variations in Paleo-Oxygenation in the Western Interior Seaway
Ichnology of the Bridge Creek Limestone: Evidence for Temporal and Spatial Variations in Paleo-Oxygenation in the Western Interior Seaway
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桥溪石灰岩的技术：西部内海航道古氧化作用时空变化的证据
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发表时间：
1998
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影响因子：
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通讯作者：
C. Savrda
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作者：
C. Savrda
上白垩统（Cenomanian-Turonian）桥溪石灰岩的特征是在含氧沃茨中沉积的远洋石灰岩和泥灰岩的分米级交替。两个岩心中桥溪纹层岩和四个与氧有关的遗迹群落的垂直堆叠模式：美国地质调查局科罗拉多中东部的波特兰1号和阿莫科1号Rebecca K.从堪萨斯州西部的边界提供了一个记录的时间和空间的变化，在海底氧在西部内陆海道的远端近海部分。为波特兰岩心重建的古氧合历史反映：（1）整个桥溪段海底氧合呈下降趋势;（2）对应于石灰岩/泥灰岩页岩偶层的高振幅氧化还原旋回性;（3）泥灰岩页岩段内表现为频率较高、振幅较低的氧化还原旋回性。趋势（1）和（2）在Bounds核心中得到了很好的表达。然而，泥灰岩页岩间隔中的生物扰动层不太常见，较薄，遗迹群落等级较低，或完全不存在。这种模式表明，古氧化水平较低的边界的地方，至少在沉积周期的碎屑为主的阶段，并可能反映较高的生产力和氧气需求在盆地的东部。
The Upper Cretaceous (Cenomanian-Turonian) Bridge Creek Limestone is characterized by decimeter-scale alternation of pelagic limestones and marly shales that were deposited under variably oxygenated waters. Vertical stacking patterns of laminites and four oxygen-related ichnocoenoses in the Bridge Creek in two coresUSGS #1 Portland from east-central Colorado and Amoco #1 Rebecca K. Bounds from western Kansasprovide a record of both temporal and spatial changes in benthic oxygenation within the distal offshore parts of the Western Interior Seaway. Paleo-oxygenation histories reconstructed for the Portland core reflect: (1) a broad trend towards decreased benthic oxygenation through the entire Bridge Creek interval; (2) a high-amplitude redox cyclicity that corresponds to limestone/marly shale couplets; and (3) a higher-frequency, lower-amplitude redox cyclicity expressed within the marly shale intervals. Trends (1) and (2) are well expressed in the Bounds core. However, bioturbated horizons in marly shale intervals are less common, thinner, of lower ichnocoenosis rank, or absent altogether. This pattern indicates that paleo-oxygenation levels were lower at the Bounds locality, at least during clastic-dominated phases of depositional cycles, and may reflect higher productivity and oxygen demand in the eastern part of the basin.