5 edition of Geology on Your Doorstep found in the catalog.
|Statement||Geological Society of London|
|Publishers||Geological Society of London|
|LC Classifications||April 1996|
|The Physical Object|
|Pagination||xvi, 124 p. :|
|Number of Pages||88|
nodata File Size: 2MB.
Because of subsequent erosion each terrace occurs as patchy remnants. England, Scotland and even Scandinavia. It is a shallow sea deposit at the base, but upper parts were deposited by rivers flowing eastwards across the area.
It is divided into Lower, Middle and Upper parts by two layers 5-10 ft thick, which are harder than most of the remainder. The sea in which it accumulated was much deeper and clearer, with almost no mud from the land. Interglacial deposits were mainly formed in small lakes or streams, and are therefore even more localised in occurrence.
It is a very hard material, which has has been used as building stone, mainly for facing external walls of churches and houses throughout the county. After deposition of the Reading Beds there was a further cycle of uplift, tilting, erosion and then subsidence of the land beneath the sea. An interesting hard rock material sometimes found in the Reading Beds is Hertfordshire Puddingstone see examples and posters relating to this on the stall.
1about 100 million years old. Southward overflow from the lake formed a new course, which developed into the present Thames valley through Middlesex Geology on Your Doorstep central London.
The Gault Clay is composed mainly of fine mud brought into the Upper Cretaceous sea from surrounding land areas by rivers. Examples of Reading Beds outliers occur in northern parts of St. In contrast, the Chalk is composed almost entirely of calcium carbonate accumulated by microscopic marine organisms, especially planktonic algae.
In south-eastern Hertfordshire the Chalk is about 680 ft thick.
The Upper Chalk thickens south-eastwards from about 90 ft on the Chiltern crest near Tring to a maximum of 280 ft beneath south-east Hertfordshire Fig.
Its upper layers contain a few layers of flint nodules, which are composed of pure microcrystalline silica, probably derived from sponges and radiolaria living in the Chalk sea.
Albans, its valley patterns and soil types are all determined by the geological history of the area.