Paralic sedimentology of the Mussentuchit Member coastal plain, Cedar Mountain Formation, central Utah, U.S.A.
Paralic sedimentology of the Mussentuchit Member coastal plain, Cedar Mountain Formation, central Utah, U.S.A.
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DOI：
10.2110/jsr.2021.028
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发表时间：
2022-06
影响因子：
2
通讯作者：
Ryan T. Tucker;C. Suarez;P. Makovicky;Lindsay E. Zanno
中科院分区：
文献类型：
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作者：
Ryan T. Tucker;C. Suarez;P. Makovicky;Lindsay E. Zanno
尽管对含化石的Mussentuchit成员（犹他州最上层雪松山组）富含火山碎屑的沉积物的深入研究已经提供了一个精细的年代地层框架，但古环境解释仍然是神秘的。为了解决这个问题，我们对美国犹他州中部Emery南部暴露的Mussentuchit成员露头进行了相分析和建筑重建。与之前的解释（河流、湖泊）相反，我们发现了一套广泛的相，表明沉积发生在近岸沉积中心的陆地部分，受远端冲积系统和近端海岸系统的影响。我们得出结论，Mussentuchit段是一个悬浮沉降粉粒的汇，大部分经历了成土蚀变，类似于法属圭亚那的现代沿海平原（Wang et al. 2002; Anthony et al. 2010, 2014）。然而，这个向陆的斜流沉积中心在时间上并不均匀。沉积学证据表明，受基准面变化（高地下水位、沉积物中水长时间滞留）、古土壤类型变化、δ18O变重变轻以及相对湿度（ε）明显变化的影响，景观改变正在进行；常见于沿海地区)。如果将上述数据与最近的年龄数据相结合，我们解释Mussentuchit成员与东部邻近的西部内陆航道的s.b.4 Greenhorn回归（Thatcher石灰岩）相关。作为一个向陆的近流沉积中心，Mussentuchit可能对基准面条件敏感，以响应正在进行的构造过程推动前深东部，并且在Cenomanian-Turonian热极大期之前，较低的古co2水平加上全球海平面的小幅下降（短暂冰期）。总之，我们的研究结果不仅加强了中西部内陆海道的联系，而且同时得出了与北美中部塞诺曼尼亚时期近同时期的海陆沉积中心的新联系。
Although intensified work on the volcaniclastic-rich sediments of the fossil-bearing Mussentuchit Member (uppermost Cedar Mountain Formation, Utah) has provided a refined chronostratigraphic framework, paleoenvironmental interpretations remain cryptic. To resolve this, we performed facies analysis and architectural reconstruction on exposed Mussentuchit Member outcrops south of Emery, central Utah, USA. Contrary to previous interpretations (fluvial, lacustrine), we identified a broad suite of facies that indicate that deposition occurred on the landward part of a paralic depocenter, influenced by both distal alluvial and proximal coastal systems. We conclude that the Mussentuchit Member was a sink for suspension-settling fines with most undergoing pedogenic alteration, analogous to the modern coastal plain of French Guiana (Wang et al. 2002; Anthony et al. 2010, 2014). However, this landward paralic depocenter was not uniform through time. Sedimentological evidence indicates landscape modification was ongoing, influenced by an altered base-level (high groundwater table, long residency of water in sediments, shifts in paleosol types, heavier to lighter δ18O, and distinct shifts in relative humidity (ε); common in coastal settings). If the above data is coupled with recent age data, we interpret that the Mussentuchit Member correlates to the S.B. 4 Greenhorn Regression (Thatcher Limestone) of the adjacent Western Interior Seaway to the east. As a landward paralic depocenter, the Mussentuchit would have been sensitive to base-level conditions in response to ongoing tectonic processes pushing the foredeep east, and lower paleo-CO2 levels coupled with a minor global sea-level fall (brief glacial phase) just before to the Cenomanian–Turonian Thermal Maximum. Altogether, our results not only strengthen linkages in the central Western Interior Seaway, but simultaneously results in novel linkages to near-coeval paralic depocenters across mid-Cenomanian North America.