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The Mercia Mudstone Group is now divided into five formations recognised and mappable across its entire outcrop and subcrop. The formations are a mix of mudstones, siltstones, sandstones and halites. Historically this sequence of rocks has been subdivided in different ways with different names in each of the basinal areas in which it is found.
The oldest rocks exposed at or near the surface of Lincolnshire are the sandstones and mudstones of the early Triassic Sherwood Sandstone Group.Rocks from this and the overlying Mercia Mudstone and Penarth groups occur in the northwest of the county and along its western border but are generally concealed beneath a thick cover of recent deposits.
Mudstone on east beach of Lyme Regis, England. Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds.Mudstone is distinguished from shale by its lack of fissility.
Mudstones, shales, lutites, and argillites are common qualifiers, or umbrella terms; however, the term mudrock has increasingly become the terminology of choice by sedimentary geologists and authors. The term "mudrock" allows for further subdivisions of siltstone, claystone, mudstone, argilite and shale. For example, a siltstone would be made ...
The Penarth Group is a Rhaetian age lithostratigraphic group (a sequence of rock strata) which is widespread in Britain.It is named from the seaside town of Penarth near Cardiff in south Wales where strata of this age are exposed in coastal cliffs southwards to Lavernock Point.
On top of the Nether Alderley Sandstone lie the Mercia Mudstones which attain a thickness of 300 m, but these are only seen on the lower plains, it is in these beds that the halite lies. Mottling in the red blocky mudstone is of two main types,
Is dominated by mudstones with varying compositions and colors, divided into three main stratigraphic units: the lower beds, dark purple, marbled mudstones rich in carbonates. They contain calcitic replacements of small roots and show signs of pedogenic processes, including mud cracks and pseudobreccias.
Rocks originating in the Carboniferous Period underlie the uplands of eastern and north Lancashire. Listed in order of succession i.e. lowermost/oldest first, they comprise the various limestones, mudstones, siltstones and sandstones of the Bowland High Group and Trawden Limestone Group, Craven Group, Millstone Grit Group, Pennine Coal Measures Group and Warwickshire Group.