| P number: | P521389 |
|---|---|
| Caption: | Rock specimen of greywacke. Woodhead Mines, Carsphairn, Kirkcudbrightshire, Scotland. |
| Description: | The rock is a fine to medium-grained muddy sandstone, with a grey colour. British Geological Survey Petrology Collection sample number EMC3644. Greywacke is a widely-used term for a poorly-sorted sandstone which commonly has a muddy matrix cement containing angular fragments of variable grain size. These clasts are commonly lithic in origin, that is they are derived from rock fragments. Many greywackes were deposited in deep water situations by turbidity currents, and are termed turbidites. They show a range of characteristic sedimentary structures, but are typified by their poorly sorted nature. The greywacke is Ordovician in age. Most of the Southern Upland Northern Belt is made up of greywackes with finer-grained interbeds. It is thought that the deposition of greywackes was the result of submarine turbidity currents which carried large quantities of rocks on the steep margins of continental shelf. There seems to have been a gradual deepening of water from the shallow water deposits near Girvan to the massive deposits of greywackes to the fine deeper water graptolitic shales with radiolarian cherts near Moffat. |
| Date taken: | Sun Dec 01 00:00:00 GMT 2002 |
| Photographer: | McTaggart, F.I. |
| Associate: | T.S. Bain |
| Copyright statement: | NERC |
| Additional information: | EMC3644 |
| Orientation: | Landscape |
| Size: | 306.00 KB; 1000 x 812 pixels; 85 x 69 mm (print at 300 DPI); 265 x 215 mm (screen at 96 DPI); |
| Average Rating: | Not yet rated |
| Categories: | Unsorted Images |
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