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This programme examines in detail the variations in sea level which have occurred in both the recent and geologically distant past by looking for evidence in the sands, clays and limestones of the ...upper Jurassic along the Dorset coast.
Metadata describing this Open University video programme
Module code and title: S335, Surface and sedimentary processes: case studies in Earth sciences
Item code: S335; 08
First transmission date: 23-08-1980
Published: 1980
Rights Statement:
Restrictions on use:
Duration: 00:25:00
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Producer: Stuart Carter
Contributors: Edward Phillips; Chris Wilson
Publisher: BBC Open University
Keyword(s): Bencliff grit; Corallian; Cross bedding; Kimmeridge; Nothe clay; Oolite; Sea level
Footage description: Shots of the sea and the Dorset coast. Shots of a map of Dorset, of a graph showing the sea level curve, and of limestone specimens. Commentary by Edward Phillips introduces the programme. Shots of samples of stromatolites, oolites and of finely- laminated limestones. Commentary explains that these can be used to gain information on sea level in the geologically distant past. Shots of a graph showing the sea level curve. Chris Wilson, standing by the side of a cliff, looks at a section of oolite sediment overlying a series of finer grain sediments. In order to explain this deposition, underwater shots of the Bahama Grand Bank show a modern equivalent of this type of sedimentary assemblage. Chris Wilson has a closer look at the fine grained sediments underlying the oolite. Shots of thin sections of the sediment and close-ups of fossil burrows in the rock. Shots of the cliffs and animations are used by Chris Wilson to continue his examination of the oolite and finer grain sediments below, He interprets the deposition by applying Walther's Law of Faeces. Chris Wilson then looks at the composition of the Corallian beds pointing out, with the aid of an animation and shots of the cliffs, the series of cycles in which they were deposited. Wilson has a closer look at the second of the Corallian sedimentary cycles, pointing out the shell debris and some of the trace fossils. He explains that this evidence indicates open marine conditions at time of deposition. Wilson goes on to examine the top of the Nothe clay and the yellow sand sediment above it. He points out features such as cross-bedded doggers and fragments of wood which are contained in the doggers. Wilson explains that the evidence points to shallow, possibly estuarine conditions at the time of deposition and that the entire sequence indicates a progressive shallowing of conditions (drop in sea level). Wilson examines the evidence for a more abrupt change in sea levels between the top of the second Corallian cycle and the next cycle of deposition. Shots of the cliff, the junction between cycles, and fossil burrows. A series of animated diagrams sums up the sequences of sedimentary deposition and changes in a level over the Corallian cycles. Chris Wilson examines the Kimmeridge clay deposits which lie about 200 metres above the Corallian beds. Shots of the clays and shell fossil fauna. Wilson points out the layers of bituminous shale, oil shale and coccolithic limestone which are found among the clays. He explains what these tell about sea levels at time of deposition. Finally, he briefly compares the Kimmeridge clay distribution with that of the Corallian beds. Over shots of a sea shore and a globe showing continents and oceanic ridges, commentary by Edward Phillips discusses the various mechanisms by which sea level might have been changed in the geologic past.
Master spool number: HOU3296
Production number: FOUS050F
Videofinder number: 1388
Available to public: no