Stratigraphy of Upper Silurian Cayugan Evaporites
Stratigraphy of Upper Silurian Cayugan Evaporites
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上志留统卡尤干蒸发岩地层学
DOI：
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发表时间：
1961
期刊：
影响因子：
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通讯作者：
L. Briggs
中科院分区：
文献类型：
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作者：
H. L. Alling;L. Briggs
卡尤干岩系的地层学与盆地边缘的经典术语和盆地中心的地下关系形成强烈对比。岩相和古生物相都有明确的定义和严格的限制，因此在盆地边缘碳酸盐相的几个露头很难定义一个适当的卡尤干地层框架。盆地岩石仅在纽约州和宾夕法尼亚州、马里兰州和弗吉尼亚州的阿巴拉契亚褶皱带中出露，这些岩石在很大程度上是卡尤根系列的非典型岩石。对卡尤干地层学术语的演变以及动物群的性质和分布的回顾表明了关于经典研究区域之间相关性的知识的省级性质。在纽约、宾夕法尼亚-马里兰、俄亥俄州、印第安纳州、威斯康星州和洛根-安大略使用不同的地层术语。在大多数地区，盆地边缘的术语不适用于盆地中心。此外，在报告的动物群中，在总共243个物种中，199个（82%）仅报告来自一个地点，225个（93%）报告来自一个或两个地点。为了解决其中的一些问题，建立了一个区域沉积框架，以便有一个参考标准，在这个参考标准内，可以对整个卡尤干沉积盆地进行地层分类和对比。沉积格架建立了盆地内和盆地间不连续露头、露头和地下、地下单元之间的一般地层关系。通过对蒸发岩类型分布、灰云岩关系、陆源碎屑岩及岩石单元厚度的区域岩相分析，阐明了该地区蒸发岩的岩性特征。卡尤干岩的沉积框架涉及密歇根和俄亥俄州盆地周围尼亚加拉礁台地的发展和生长，这阻止了公海和盆地之间的海洋盐水的自由交换，并对随后的蒸发岩沉积形成了最终的控制。在阿巴拉契亚盆地东部，纽约和北方宾夕法尼亚沉积了碳酸盐岩，而宾夕法尼亚南部和马里兰州的威尔斯克里克-托诺洛威海则沉积了开阔的海相石灰岩和页岩。南部开阔洋和北方蒸发岩盆地之间的海洋盐水流受到布卢姆斯堡-弗农三角洲复合体远端的限制，该复合体是由携带红色陆源碎屑的向西流溪流沉积到阿巴拉契亚盆地东部大陆架上的。
The stratigraphy of the Cayugan series strongly contrasts classical terminology of the basin margins with subsurface relationships of the basin centers. Both lithofacies and paleontological facies are sharply defined and narrowly restricted so that the few outcrops in the basin margin carbonate facies serve poorly to define a proper framework for Cayugan stratigraphy. Basinal rocks are exposed only in New York state and in the Appalachian fold-belt in Pennsylvania, Maryland, and Virginia where the rocks are largely atypical of the bulk of the Cayugan series. A review of the evolution of Cayugan stratigraphic terminology, and the nature and distribution of the faunas demonstrates the provincial nature of knowledge concerning correlation among the regions of classical study. A different stratigraphic terminology is used in New York, Pennsylvania-Maryland, Ohio, Indiana, Wisconsin, and Michigan-Ontario. In most regions the terminology of the basin margins is inappropriate for the basin centers. Moreover, in the faunas reported, out of a total of 243 species, 199 (82 per cent) are reported from only one locality, and 225 (93 per cent) are reported from one or two localities. To solve some of these problems a regional framework of sedimentation is established so that there can be a standard of reference within which stratigraphic classification and correlation over the entire Cayugan depositional basin can be made. The framework of sedimentation establishes general stratigraphic relations between disconnected outcrops, outcrop and subsurface, and subsurface units within and between basins. It is prescribed from regional lithofacies analyses of the distribution of evaporite rock types, limestone-dolomite relations, terrigenous detrital debris, and thicknesses of rock units. The sedimentary framework for Cayugan rocks involves the development and growth of Niagaran reef platforms around the Michigan and Ohio basins which prevented free interchange of oceanic brine between the open sea and the basin, and which formed the ultimate control on subsequent evaporite deposition. In the eastern part of the Appalachian basin evaporites were deposited in New York and northern Pennsylvania while open marine limestone and shale were being deposited in southern Pennsylvania and Maryland in the Wills Creek-Tonoloway sea. Oceanic brine flow between the southern open ocean and the northern evaporite basin was restricted by the distal end of the Bloomsburg-Vernon delta complex, deposited by westward flowing streams carrying red terrigenous debris onto the eastern shelf of the Appalachian basin.