geology of hereforshire

Geology of Herefordshire

Herefordshire has a rich history of geological time stretching 500 million years or more.

Herefordshire Geological Succession

Geological Time

Geological time is divided into eons, eras, periods, epochs and ages, with eons representing the largest stretches of time (500 million years or more). Each eon is subdivided into eras, which in turn are divided into periods etc… This nomenclature ends with ‘ages’, which represent the smallest increments of geological time, on the order of a few hundred thousand years.

Rocks of similar age can grouped together and placed into a geological succession, where they lie in between rock units of greater and lesser age. As geology varies across distances, these geological successions are only relevant to a specific geographical area. Geologists can get some idea of what processes were taking place in Herefordshire over millions of years, by looking at what types of rocks were forming at different times in the geological succession. The most useful subdivisions of geological time are periods, epochs and ages, as rocks dated to these resolutions can give both general and detailed information on the ancient environment.

In this geological succession, periods and epochs are used to describe the older geological succession (Precambrian – Jurassic) that is seen in Herefordshire. The most recent geological period (the Quaternary) is described in terms of period and age, as the detail preserved within these young rocks and sediments allows for more detailed interpretation.

Period

Epoch

Stratigraphic Unit

Quaternary

Holocene

Mass Movement Deposits

Alluvial Fans and related Deposits

Devensian

Herefordshire Formation

Cradley Valley Formation

Ham Green Member

Wye Valley Terrace

First Terrace

Lugg Valley Terrace

Marden Member

Teme Valley Terrace

First Terrace

Ipswichian

Second Terrace

Moreton-on-Lugg

Second Terrace

Wolstonian

Third Terrace

Kingsfield Member

Third Terrace

Fourth Terrace

Sutton Walls Member

Fourth Terrace

Colwall Member

Hoxian

Cradley Silt Member

Anglian

Risbury Formation

Starpit Formation

Portway Member

Franklands Gate Member

Stoke Prior Member

Stoke Lacy Member

Newton Farm Member

Kyre Brook

Member

Whitehouse Member

Coddington Member

Humber Formation

Mathon Formation

TIME GAP

Period

Epoch

Stratigraphic Unit

Permian

Bartestree Dolerite Intrusion

Warwickshire Group

Haffield Formation

Carboniferous

Westphalian

Trenchard Formation

Pennine Coal Measures Group

Upper Coal Measures

Middle Coal Measures

Lower Coal Measures

Cornbrook Sandstone Formation

Carboniferous Limestone Supergroup

Pembroke Limestone Group

Cromhall Sandstone Formation

Llanelly Formation

Gully Oolite

Black Rock Limestone Formation

Avon Group

Devonian

Upper Old Red Sandstone

Tintern Sandstone Formation

Quartz Conglomerate Formation

Lower Old Red Sandstone

Breconian Group

Brownstones Formation

Senni Formation

Dittonian Group

St Maughans Formation/Hackley Limestone

Sandy Haven Formation

Townsend Tuffs Beds

Silurian

Pridoli

Downton Group

Raglan Mudstone Formation/ Bishop’s Frome Limestone

Ledbury Formation

Temeside Mudstone Formation

Downton Castle Sandstone Formation

Ludlow Bone Bed

Ludlow

Cefn Einion Formation

Knucklas Castle Formation

Bailey Hill Formation

Upper Ludlow Shales Group

Whitcliffe Formation/Whitcliffe Flag Member

Leintwardine Formation/ Mocktree Shale Member

Aymestry Limestone Formation

Lower Ludlow Shales Group

Bringewood Formation

Elton Formation

Wenlock

Much Wenlock Limestone Formation

Coalbrookdale Formation

Woolhope Limestone Formation

Llandovery

May Hill Sandstone Group

Haugh Wood Formation

Wyche Formation/Yartleton Formation

Cowleigh Park Formation/Huntley Hill Formation

Folly Sandstone Formation

Letton Sandstone Formation

Ordovician

Tremadoc

Habberley Shale Formation

Shineton Shale Formation

Bronsil Shale Formation

Ordovician Intrusives

Cambrian

Merioneth

White-Leaved Oak Shale Formation

Hollybush Sandstone Formation

Malvern Quartzite Formation

Precambrian

Warren House Formation

Malverns Complex

Brampton Formation

Reproduced with the permission of the British Geological Survey © NERC. All Rights Reserved. Based upon information in the BGS Lexicon and the BGS memoir ‘Geology of the country between Hereford and Leominster, 1:50,000 scale sheet 198‘, with the permission of the British Geological Survey

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