Lower Palaeozoic lithostratigraphical classification in the English Lake District

Abstract

In the English Lake District lithostratigraphical classification has not kept pace with either the international and national codes or the code of the Geological Society (Holland cr ul. 1978). Probelms arise, firstly, from acceptance by several of those working in the area, of terms used in by-gone days, such as 'Borrowdale Volcanic Series', and secondly, and more importantly, because individuals have specialized on certain parts of the sequence (the Skiddaw Slates, the Coniston Limestone, etc.), and have erected classifications for these rocks without reference to other parts of the succession. These classifications are examined and modified in such a way that the lithostratigraphical subdivisions are consistent for the whole of the Lower Palaeozoic sequence of the Lake District, and also relate to the international code as it is applied in other regions. The basic Lake District stratigraphical terminology of the last century is, however, retained in all its essentials.

Lithostratigraphy of the Windermere Supergroup, Northern England

“…It is equivalent to Norman's (1961) Stennerley Mudstone (cf his miscorrelation with the Coldwell Formation, subsequently followed by Moseley 1984).…”

“…There seems no reason to follow Marr's unhelpful association of Lower, Middle and Upper Coldwell Beds, which have no sedimentological affiliation, nor to adopt Moseley's (1984) proposal of uniting them in a single formation (his Coldwell Formation). We revert to Aveline and Hughes' original usage of the term Coldwell (Beds) to refer to the calcareous siltstones of late WenlocWearly Ludlow age.…”

“…A more or less abrupt change in lithofacies and biofacies occurs near the top of the Hirnantian, and rocks of extruordinarius age or older (Rickards 1978;1988) Moseley 1984). The history of nomenclature of this part of the sequence (Figure 4) is discussed in detail by McNamara (1979) and Lawrence et al (1986).…”

“…The history of nomenclature of this part of the sequence (Figure 4) is discussed in detail by McNamara (1979) and Lawrence et al (1986). We have adopted the basic units defined by McNamara (1979), but have reduced them in rank to members (Moseley 1984) and renamed the White Limestone and Rhyolitic Ash. We divide the Ordovician sequence in the main Lake District outcrop into six formations, grouped into four depositional packages bounded by the erosional or non-depositional breaks deduced by McNamara (1979).…”