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The first and major part of the programme is titled Zone Fossils and the speaker is Dr. Dennis Jackson, Senior Lecturer in the Department of Earth Sciences at the Open University. The second part,... is titled Mapwork: Unconformities; overstep and overlap and the speaker is Dr Chris Wilson, also Senior Lecturer in Earth Sciences at the Open University. Dr. Jackson examines the beds for fossils in the cliffs along the Dorset coast near Charmouth. He shows how fossils, particularly ammonites, can be collected in the field and used to zone the strata in which they occur. Many fossils are found but only certain ones are useful as zone fossils. Specimens collected in the field are described and identified in a bit more detail in the studio. Ammonites are compared with present day Nautilus seen in underwater film to show why this group makes such good zone fossils. Another section, a few miles away, is examined and the litholigy and fossil content recorded. The two cliff sections are compared to show the local limits of the Amaltheus Stokesi Zone. Dr. Jackson concludes by saying that though the beds or rock stratigraphic units are limited in extent on the other hand the fossil zones or time stratigraphic units are world wide. With the aid of a block model Dr. Wilson explains the difference between the terms overstep and overlap which are used in describing unconformities. He also shows that the basal conglomerate cuts across the time planes, and is therefore diachronous.
Metadata describing this Open University video programme
Item code: S23-; 05
First transmission date: 18-03-1972
Published: 1972
Rights Statement:
Restrictions on use:
Duration: 00:24:06
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Producer: Peter Clarke
Contributors: David Jackson; Chris Wilson
Publisher: BBC Open University
Keyword(s): Amaltheus stokesi zone; Ammonites; Cliffs; Dorset; Lithology; Nautilus; Overstep; Rock stratigraphic unit; Strata; Zone fossils
Footage description: Programme is in two parts. Part 1. Title: Zone fossils. Dennis Jackson on the beach near Charmouth, Dorset. He cuts a piece of rock from the base of the cliffs and shows a fossil ammonite. Jackson explains their value for stratigraphic examinations. He then moves to another part of the cliffs and examines index fossils found there. Jackson collects several of these fossils for examination in the studio. Jackson in the studio with his collection of fossils. He examines each in turn and explains why, of his sample, only the ammonites are good zone fossils. Jackson uses an ammonite specimen to explain how these fossils are identified accurately. Jackson with the shell of a present day Nautilus. The shell is cut in two to expose the floatation gas chambers inside. Jackson points out the main features. Film shots of a live Nautilus swimming in the sea. Film shots of mussels on the sea botton. Commentary by Jackson explains why bottom dwellers do not make good zone fossils. He then sums up the qualities of ammonites which make them good zone fossils. Jackson uses an enlarged photograph of the cliffs at Charmouth to explain how the Jurassic period is zoned by an examination of fossils. He compares this section with a photograph of another section of cliffs a few miles away. Jackson on location at the section shown in the photograph. He examines the lithology records the fossil content. Jackson compares the two cliff faces to show the local limits of the Ajnaltheus stokesi zone. Jackson shows a geological diagram of the two sections showing the zone. Part 2 Title: Mapwork: unconformities, overstep and and overlap. Chris Wilson uses a geological block; model to explain the differences between overlap and overstep. He also shows that the basal conglomerate cuts across the time planes and is therefore diachronous.
Master spool number: 6HT/70379
Production number: 00521_2154
Videofinder number: 1712
Available to public: no