The Devon Karst Research Society.

The Society's Homepages for the
CATTEDOWN BONE CAVES,
Cattedown, Plymouth, Devon, England, U.K.

Text and images throughout the Cattedown Pages is by B. Lewarne, Honorary Science Officer.
Copyright ©2003 The Devon Karst Research Society, Cattedown Bone Caves pages all original text and images.
Updated on 28 May 2004.


REDMAN'S FISSURE COMPLEX.
Cattedown Quarry, ChevronTexaco Ltd. Plymouth Oil Terminal, No. 3. Site.

INTRODUCTION :
This interesting area, named after a Shell-Mex / BP employee, who was the Oil Terminal's Manager during the 1960's and early 1970's, is located within the ChevronTexaco Ltd. Plymouth Oil Terninal No. 3 Site, to the immediate rear of the Cattedown Reindeer Rift Cave. The two striking aspects of this area are the structural geological features within the overhanging quarry face and the karst development directly associated with the structural geology.
The images below illustrate some of the characteristics of the area.


Image C3s-RFC01. Indicates some of the infilled karstic cavities on the old quarry face.
The narrow vertically orientated fissures to the right of the standing figure are indicated again below in Image C3s-RFC02.
(Photo :  B. Lewarne, 11 Jan. 1999.)


Image C3s-RFC02. The narrow vertically-orientated fissure in Image C3s-RFC01. at the top of this page is here seen again connecting with the surface. The cave infill material has originated from the surface.
Also indicated are phreatic tubes, the beginning stage of most karst solution cavities. Also of great importance is the fact that the quarry face is also, for the most part, co-incidentally a cave wall, reaching
from the base to the surface in many places.
(Photo :  B. Lewarne, 11 Jan. 1999.)


Image C3s-RFC03. In the centre of the view is the RFC- East 6 Fissure.
Some of the fissures clearly indicate several stages of general karst development.
(Photo :  B. Lewarne, 11 Jan. 1999.)

The RFC- East 6 Fissure started as a very small diameter phreatic tube, which widened in diameter until the water came under the influence of gravity in the vadose stage and started to cut the base of the phreatic tube vertically downwards. After sedimentation occurred within the vadose trench and stream water flow stopped, the dripping of lime-rich percolation water deposited stalagmite on top of  the sediments, creating a "false floor" scenario. This effectively sealed the sediments into place within the fissure system, preserving whatever fossil evidence they contain. At a later stage, even more sediments were then deposited on top of the stalagmite floor, (not clearly seen in the photograph). A substantial void or air space exists above the final layer of deposits. A visual inspection of both the surface of the top sediment layer above the obvious stalagmite floor and of the stalagmite floor itself indicates that they both slope downwards into the void and into the body of the rock away from the camera. In other words, the sediments originated from within the section of east-west orientated cave passage of which the quarry face is itself the cave's south wall.

Image C3s-RFC04. Some of the fissures are filled with a limestone breccia / earth matrix,
clearly not derived as stream-laid sediments but as talus debris falling in from the surface
and also derived from the breakdown of the internal walls of the fissure itself.
The trowel forms a scale.
(Photo :  B. Lewarne, 11 Jan. 1999.)
The full extent of this area will be presented here in due course. The area is a wonderful natural treasure trove of the fossil record, containing large quantities of unexcavated cave material. The Society intends that the area generally remains unexcavated until a detailed programme of stratigraphic work on the cave sediments is proposed. The cave sediment sections will be cleaned up and will be available for passive observation.

SEDIMENTOLOGY :
As of May 2005, the Geography Department of Oxford Brookes University will be taking initial trial samples of sediments from cave and fissures across the Cattedown Quarry areas for detailed analysis. On 27 May 2005,  the RFC- East 6 Fissure (pictured in Image C3s-RFC03. above) was the subject of detailed sediment sampling.
As part of the Cattedown Bone Caves Heritage Site Project, there will soon be a separate Webpage dedicated to the Sedimentology and Stratigraphy of the cave sediments and fissure infillings of the Cattedown Caves.


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