High‐level peperitic sills in the English Lake District: Distinction from block lavas, and implications for borrowdale volcanic group stratigraphy
High‐level peperitic sills in the English Lake District: Distinction from block lavas, and implications for borrowdale volcanic group stratigraphy
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英国湖区的高位岩岩基岩：与块状熔岩的区别及其对借代尔火山群地层学的影响
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发表时间：
2007
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通讯作者：
R. Suthren
中科院分区：
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作者：
M. Branney;R. Suthren
区分这种岩床与块状熔岩的标准包括不整合和断层控制的几何形状、上部接触附近沉积物的泡沫化和均一化，以及上部接触处是否存在枕头或珍珠岩。因为窗台在野外并不总是表现出这些特征，所以应该证明板材的挤出原点，而不是假设。然而，区分并不总是可能的，在这种情况下，可以有效地应用非遗传术语表。
实地研究表明，Borrowdale火山群的很大一部分是由岩床组成的。因此，以前建立的岩石地层方案可能不能正确地指示岩浆事件的序列，并且在确定高级别侵入体的区域重要性之前，不可能进行局部定义的地层对比。
Criteria by which such sills can be distinguished from block lavas include discordance and fault-controlled geometry, vesiculation and homogenization of sediments adjacent to upper contacts, and the presence of pillows or peperites at upper contacts. Because sills do not always show these characteristics in the field, an extrusive origin for a sheet should be demonstrated and not assumed. However, it is not always possible to make the distinction, in which case the non-genetic term sheet can be usefully applied.
Field studies suggest that a substantial part of the Borrowdale Volcanic Group is composed of sills. Thus previously erected lithostratigraphic schemes may not correctly indicate the sequence of magmatic events, and the correlation of locally defined stratigraphies will not be possible until the regional importance of high-level intrusive bodies has been established.