Division of Resource Management, Petrified Forest National Park, Petrified Forest, Arizona, United States of America.
PLoS One. 2010 Feb 19;5(2):e9329. doi: 10.1371/journal.pone.0009329.
Recent revisions to the Sonsela Member of the Chinle Formation in Petrified Forest National Park have presented a three-part lithostratigraphic model based on unconventional correlations of sandstone beds. As a vertebrate faunal transition is recorded within this stratigraphic interval, these correlations, and the purported existence of a depositional hiatus (the Tr-4 unconformity) at about the same level, must be carefully re-examined.
METHODOLOGY/PRINCIPAL FINDINGS: Our investigations demonstrate the neglected necessity of walking out contacts and mapping when constructing lithostratigraphic models, and providing UTM coordinates and labeled photographs for all measured sections. We correct correlation errors within the Sonsela Member, demonstrate that there are multiple Flattops One sandstones, all of which are higher than the traditional Sonsela sandstone bed, that the Sonsela sandstone bed and Rainbow Forest Bed are equivalent, that the Rainbow Forest Bed is higher than the sandstones at the base of Blue Mesa and Agate Mesa, that strata formerly assigned to the Jim Camp Wash beds occur at two stratigraphic levels, and that there are multiple persistent silcrete horizons within the Sonsela Member.
CONCLUSIONS/SIGNIFICANCE: We present a revised five-part model for the Sonsela Member. The units from lowest to highest are: the Camp Butte beds, Lot's Wife beds, Jasper Forest bed (the Sonsela sandstone)/Rainbow Forest Bed, Jim Camp Wash beds, and Martha's Butte beds (including the Flattops One sandstones). Although there are numerous degradational/aggradational cycles within the Chinle Formation, a single unconformable horizon within or at the base of the Sonsela Member that can be traced across the entire western United States (the "Tr-4 unconformity") probably does not exist. The shift from relatively humid and poorly-drained to arid and well-drained climatic conditions began during deposition of the Sonsela Member (low in the Jim Camp Wash beds), well after the Carnian-Norian transition.
最近对石化林国家公园钦勒组的森萨拉成员进行了修订，提出了一个基于非常规砂岩床对比的三部分岩石地层模型。由于在这个地层间隔记录了脊椎动物动物群的过渡，因此必须仔细重新检查这些对比，以及在同一水平假定存在沉积间断（Tr-4 不整合面）。
方法/主要发现：我们的调查表明，在构建岩石地层模型时，忽略了走出去接触和测绘的必要性，以及为所有测量剖面提供 UTM 坐标和标记照片。我们纠正了森萨拉成员内部的对比错误，证明有多个弗拉特斯通一号砂岩，它们都高于传统的森萨拉砂岩床，森萨拉砂岩床和彩虹森林床是等同的，彩虹森林床高于蓝梅萨和玛瑙梅萨底部的砂岩，以前分配给吉姆营冲洗床的地层出现在两个地层水平，以及在森萨拉成员中有多个持久的硅化岩层。
结论/意义：我们提出了一个修订后的森萨拉成员的五个部分模型。从最低到最高的单元是：营地巴特床、洛特之妻床、碧玉森林床（森萨拉砂岩/彩虹森林床）、吉姆营冲洗床和玛莎巴特床（包括弗拉特斯通一号砂岩）。尽管钦勒组中有许多侵蚀/加积旋回，但在森萨拉成员内部或底部可能不存在可以追溯到整个美国西部的单一不整合面（“Tr-4 不整合面”）。从相对潮湿和排水不良到干旱和排水良好的气候条件的转变始于森萨拉成员（吉姆营冲洗床较低）的沉积过程中，远在卡尼安-诺利安过渡期之后。
