The Lias Group at Staithes

 

The Lias is a period of Geological time towards the end of the Early Jurassic, that is from around 195,000,000 years ago until 180,000,000 years ago. Not yesterday then! This was a period of the geological history of the United Kingdom when the area of what is now Yorkshire, and a great deal more, was alternately a shallow sea, lagoon or dried out delta baking under a very hot tropical environment. The corresponding deposited rocks are of the sedimentary type ranging from sandstones, shales and mudstones and were laid down in distinct layers.

 

Rocks in 'Layers'

Sedimentary layers in the rocks of the cliffs at Penny Nab in Staithes

Sedimentary layers in the rocks of the cliffs at Penny Nab in Staithes

Image by dated: July, 2004

 

Penny Nab

The horizontal structure of the stratigraphy of the Lias sediments in the cliffs between Penny Nab and Staithes Harbour. Around the corner behind the photographer the sediments follow an easterly dip.

It is thought that "Lias" is derived from local dialect or spelling of the word "layer", this however could be mere coincidence. One thing is for sure, as can be seen from the picture above, that the sediments of this period are preserved in very distinct layers.

 

 

The Jurassic Period

Period Sub Period Stage Millions of Years
From To

Jurassic

Late Jurassic

Volgian

142

150

Kimmeridgian

150

154

Oxfordian

154

159.4

Middle Jurassic

Callovian

159.4

165

Bathonian

165

170

Bajorcian

170

177

Aalenian

177

180.1

Early Jurassic

Toarcian

180.1

187

Pliensbachian

187

194.5

Sinemurian

194.5

201

Hettangian

201

205.7

 

Over the whole of the Untied Kingdom the Lias itself is also sub divided into three distinct zones or early, middle and late however not all the stratum (layers) are found at all locations. Here at Staithes is no exception elements of the Middle Lias are difficult to detect, if indeed they are present here at all.

 

Lithostratigraphical subdivisions of the Lias Group

Group Stage Formation Member

LIAS

 

Toarcian

Blea Wyke

Yellow Sandstone

Grey Sandstone

Whitby Mudstone

Fox Cliff Sandstone

Peak Mudstone

Alum Shale

Mulgrave Shale

Grey Shale

Pliensbachian

Cleveland Ironstone

Kettleness

Penny Nab

Staithes Sandstone
Late Redcar Mudstone

Ironstone Shale

Pyritous Shale

 

We will trace, in later pages, the Whitby Mudstones from the top of Boulby Cliff and Old Nab down to the Staithes Sandstone at Penny Nab. Staithes itself is located in the middle of the Staithes Sandstone layer, hence the name.

Geological Section at Staithes

Geological section profile at Staithes, North Yorkshire

Geological section profile at Staithes, North Yorkshire

Image by dated: 1998