Loch Doon And Carsphairn - an excursion - Revision history

Scotfot at 19:47, 6 November 2015

2015-11-06T19:47:51Z

← Older revision		Revision as of 20:47, 6 November 2015
Line 1:		Line 1:
	By J D Floyd and D J Fettes. Excursion 7. From: Stone, P (editor). 1996. Geology in south-west Scotland: an excursion guide. Keyworth, Nottingham: British Geological Survey.		By J D Floyd and D J Fettes. Excursion 7. From: Stone, P (editor). 1996. [[Geology in south-west Scotland: an excursion guide]]. Keyworth, Nottingham: British Geological Survey.

	== Loch Doon And Carsphairn: Ordovician turbidites, mineralisation and the Loch Doon Granite==		== Loch Doon And Carsphairn: Ordovician turbidites, mineralisation and the Loch Doon Granite==

JenniferFindlay1 at 08:44, 13 October 2015

2015-10-13T08:44:06Z

← Older revision		Revision as of 09:44, 13 October 2015
Line 22:		Line 22:

	=== Excursion ===		=== Excursion ===
	[[File:LochDoonCarsphairnExcursionMap.jpg\|~~400px~~\|thumbnail\|Locality map and outline geology for the Loch Doon-Carsphairn area.]]		[[File:LochDoonCarsphairnExcursionMap.jpg\|350px\|thumbnail\|Locality map and outline geology for the Loch Doon-Carsphairn area.]]

	==== 1 Loch Doon Dam: Marchburn Formation greywacke ====		==== 1 Loch Doon Dam: Marchburn Formation greywacke ====

JenniferFindlay1 at 11:23, 6 October 2015

2015-10-06T11:23:58Z

← Older revision		Revision as of 12:23, 6 October 2015
Line 25:		Line 25:

	==== 1 Loch Doon Dam: Marchburn Formation greywacke ====		==== 1 Loch Doon Dam: Marchburn Formation greywacke ====
	Park beside the tourist office/toilet block beside the dam at the north end of Loch Doon (NS 477 012). Walk south for about 600 m along the wave-washed western shore of the reservoir to examine excellent ''roches moutonnees ''with good examples of glacial striae gouged into well-polished rock surfaces. The latter reveal good sections through medium- to thick-bedded, coarse- grained greywackes and laminated siltstones of the Marchburn Formation. Beds strike between 060° and 090° and dip south at 60-80°. However, excellent graded bedding and other sedimentary structures in the greywackes clearly demonstrate that the succession youngs towards the north and that the beds are therefore overturned. This bedding attitude is common across much of the Northern Belt, especially in the area immediately south of the Southern Upland Fault.		[[File:P509338.jpg\|300px\|thumbnail\|left\|Loch Doon, Ayrshire/Kirkcudbrightshire border. Looking south-south-east from dam. Black Craig in centre with Coran of Portmark, then Boe, then Meaul, and then Carlins Cairn to the right. P509338]]Park beside the tourist office/toilet block beside the dam at the north end of Loch Doon (NS 477 012). Walk south for about 600 m along the wave-washed western shore of the reservoir to examine excellent ''roches moutonnees ''with good examples of glacial striae gouged into well-polished rock surfaces. The latter reveal good sections through medium- to thick-bedded, coarse- grained greywackes and laminated siltstones of the Marchburn Formation. Beds strike between 060° and 090° and dip south at 60-80°. However, excellent graded bedding and other sedimentary structures in the greywackes clearly demonstrate that the succession youngs towards the north and that the beds are therefore overturned. This bedding attitude is common across much of the Northern Belt, especially in the area immediately south of the Southern Upland Fault.


	==== 2 Loch Doon Castle: granite/greywacke contact ====		==== 2 Loch Doon Castle: granite/greywacke contact ====

Scotfot: /* 7 Liggat Bridge, Carsphairn: greywackes and dykes */

2015-03-30T19:55:43Z

7 Liggat Bridge, Carsphairn: greywackes and dykes

← Older revision		Revision as of 20:55, 30 March 2015
Line 80:		Line 80:

	About 200 m downstream from the bridge, medium- and thick-bedded greywackes of the andesite-rich Portpatrick Formation are exposed in the bed of the river close to the north bank, though the contact with the Glenwhargen Formation cannot be seen at this locality. Beds here strike 060° and dip south at 70°'' ''though a paucity of way-up evidence precludes determination of younging direction. Abundant evidence from other parts of the Southern Uplands shows that the Portpatrick and Glenwhargen formations are interbedded.		About 200 m downstream from the bridge, medium- and thick-bedded greywackes of the andesite-rich Portpatrick Formation are exposed in the bed of the river close to the north bank, though the contact with the Glenwhargen Formation cannot be seen at this locality. Beds here strike 060° and dip south at 70°'' ''though a paucity of way-up evidence precludes determination of younging direction. Abundant evidence from other parts of the Southern Uplands shows that the Portpatrick and Glenwhargen formations are interbedded.
			<References/>
			{{EGwalks}}
			[[Category:6. The South of Scotland]]

Scotfot: /* 3 Woodhead Lead Mines: lead and zinc mineralization */

2015-03-30T19:54:17Z

3 Woodhead Lead Mines: lead and zinc mineralization

← Older revision		Revision as of 20:54, 30 March 2015
Line 57:		Line 57:

	There are two main veins, named Woodhead and Garryhorn, both of which trend about 150°, hade NE at 62° and probably follow part of the extensive NW trending plexus of faults which delineates the valley of the Glenkens between New Galloway and Loch Doon. The vein infill consists mainly of broken country rock (greywacke of the Kirkcolm Formation) with strings and patches of calcite, dolomite and quartz in addition to the ore minerals. There is little sign of the halo of pervasive hydrothermal alteration of the country rock which forms such a notable feature at Leadhills/ Wanlockhead. Good samples of ore minerals (particularly galena) and vein breccia can still be found on the various spoil dumps throughout the site. '''The locations of several shafts are now marked by circular '''dry-stone dyke enclosures and should be treated with caution.		There are two main veins, named Woodhead and Garryhorn, both of which trend about 150°, hade NE at 62° and probably follow part of the extensive NW trending plexus of faults which delineates the valley of the Glenkens between New Galloway and Loch Doon. The vein infill consists mainly of broken country rock (greywacke of the Kirkcolm Formation) with strings and patches of calcite, dolomite and quartz in addition to the ore minerals. There is little sign of the halo of pervasive hydrothermal alteration of the country rock which forms such a notable feature at Leadhills/ Wanlockhead. Good samples of ore minerals (particularly galena) and vein breccia can still be found on the various spoil dumps throughout the site. '''The locations of several shafts are now marked by circular '''dry-stone dyke enclosures and should be treated with caution.
			[[File:P521389.jpg\|300px\|thumbnail\|left\|Rock specimen of greywacke. Woodhead Mines, Carsphairn, Kirkcudbrightshire, Scotland. 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. P521389.]]

	In a small quarry at the north end of the site, beside an infilled shaft or collapsed stope, thick greywacke beds strike 090° and dip north at 85°. Gently pitching flute casts visible on the bases of several greywacke beds indicate currents from the NE and prove that the succession youngs northwards. The west wall of the quarry is defined by a slickensided fault plane, trending 150° and hading NE at 55°. This is probably a continuation, or a subparallel branch, of the fault which controls the Woodhead Vein. A vertical breccia vein trending 170° can also be seen on the north side of the quarry.		In a small quarry at the north end of the site, beside an infilled shaft or collapsed stope, thick greywacke beds strike 090° and dip north at 85°. Gently pitching flute casts visible on the bases of several greywacke beds indicate currents from the NE and prove that the succession youngs northwards. The west wall of the quarry is defined by a slickensided fault plane, trending 150° and hading NE at 55°. This is probably a continuation, or a subparallel branch, of the fault which controls the Woodhead Vein. A vertical breccia vein trending 170° can also be seen on the north side of the quarry.

Scotfot at 19:48, 30 March 2015

2015-03-30T19:48:18Z

← Older revision		Revision as of 20:48, 30 March 2015
Line 1:		Line 1:
	By J D Floyd and D J Fettes. Excursion 6. From: Stone, P (editor). 1996. Geology in south-west Scotland: an excursion guide. Keyworth, Nottingham: British Geological Survey.		By J D Floyd and D J Fettes. Excursion 7. From: Stone, P (editor). 1996. Geology in south-west Scotland: an excursion guide. Keyworth, Nottingham: British Geological Survey.

	== Loch Doon And Carsphairn: Ordovician turbidites, mineralisation and the Loch Doon Granite==		== Loch Doon And Carsphairn: Ordovician turbidites, mineralisation and the Loch Doon Granite==

Scotfot: /* 3 Woodhead Lead Mines: lead and zinc mineralization */

2015-03-30T19:47:55Z

3 Woodhead Lead Mines: lead and zinc mineralization

← Older revision		Revision as of 20:47, 30 March 2015
Line 43:		Line 43:

	==== 3 Woodhead Lead Mines: lead and zinc mineralization ====		==== 3 Woodhead Lead Mines: lead and zinc mineralization ====
	[[File:P509352.jpg\|300px\|thumbnail\|Trench flue and base of ruined chimney, Woodhead Lead Mine, Carsphairn. ]]		[[File:P509352.jpg\|300px\|thumbnail\|Trench flue and base of ruined chimney, Woodhead Lead Mine, Carsphairn. P509352. ]]
	Health and safety note: As with any former mining area, there may be hidden dangers involved from the presence of old shafts, adits, unsafe buildings etc. and special care is required, especially for younger (and elderly) participants. Visitors should also be aware '''of the insidious risk of heavy-metal poisoning (lead, zinc, copper etc.) both from mineral specimens and from the widespread contamination on the site. Precautions should therefore be taken with hygiene, especially during the consumption of packed lunches etc., both on site and afterwards.'''		Health and safety note: As with any former mining area, there may be hidden dangers involved from the presence of old shafts, adits, unsafe buildings etc. and special care is required, especially for younger (and elderly) participants. Visitors should also be aware '''of the insidious risk of heavy-metal poisoning (lead, zinc, copper etc.) both from mineral specimens and from the widespread contamination on the site. Precautions should therefore be taken with hygiene, especially during the consumption of packed lunches etc., both on site and afterwards.'''

Scotfot at 19:47, 30 March 2015

2015-03-30T19:47:00Z

← Older revision		Revision as of 20:47, 30 March 2015
Line 8:		Line 8:

	=== Main points of interest ===		=== Main points of interest ===


	Contact between the Loch Doon Granite and surrounding greywackes; lead-zinc mineralisation and abandoned lead mines; haematite vein; Ordovician greywacke, conglomerate, black shale and chert; porphyrite (porphyritic microdiorite) dykes.		Contact between the Loch Doon Granite and surrounding greywackes; lead-zinc mineralisation and abandoned lead mines; haematite vein; Ordovician greywacke, conglomerate, black shale and chert; porphyrite (porphyritic microdiorite) dykes.
Line 17:		Line 16:

	=== Introduction ===		=== Introduction ===


	This excursion examines the contact between the Loch Doon Granite and the surrounding greywackes (Figure 29) at Locality 2. Localities 1, 4, 5 and 7 deal with the Ordovician sedimentary succession and associated minor intrusions in the Carsphairn area. The general tectonostratigraphical relationships of the sedimentary formations are illustrated in Figure 2 (Leadhills Group). The lead mines at Woodhead (Locality 3) and the haematite vein at Coran of Portmark (Locality 6) are of interest both to mineral collectors and to students of industrial archaeology.		This excursion examines the contact between the Loch Doon Granite and the surrounding greywackes (Figure 29) at Locality 2. Localities 1, 4, 5 and 7 deal with the Ordovician sedimentary succession and associated minor intrusions in the Carsphairn area. The general tectonostratigraphical relationships of the sedimentary formations are illustrated in Figure 2 (Leadhills Group). The lead mines at Woodhead (Locality 3) and the haematite vein at Coran of Portmark (Locality 6) are of interest both to mineral collectors and to students of industrial archaeology.
Line 41:		Line 39:

	The numerous ruins of brick buildings beside the road along the loch, and the concrete blocks in the loch itself, are the remains of a seaplane base which was established at Loch Doon during the First World War. Some curious embankments on the east shore at the head of the loch were also part of this project, which swallowed up large amounts of money and caused great controversy at the time.		The numerous ruins of brick buildings beside the road along the loch, and the concrete blocks in the loch itself, are the remains of a seaplane base which was established at Loch Doon during the First World War. Some curious embankments on the east shore at the head of the loch were also part of this project, which swallowed up large amounts of money and caused great controversy at the time.


	Loch Doon Castle itself originally stood on an adjacent small island in the loch, the top of which can still be seen when the water is low. During the 1930s, when the water level in the loch was raised as part of the hydroelectric scheme, the castle was dismantled stone by stone and re-erected at its present site.		Loch Doon Castle itself originally stood on an adjacent small island in the loch, the top of which can still be seen when the water is low. During the 1930s, when the water level in the loch was raised as part of the hydroelectric scheme, the castle was dismantled stone by stone and re-erected at its present site.

	==== 3 Woodhead Lead Mines: lead and zinc mineralization ====		==== 3 Woodhead Lead Mines: lead and zinc mineralization ====
			[[File:P509352.jpg\|300px\|thumbnail\|Trench flue and base of ruined chimney, Woodhead Lead Mine, Carsphairn. ]]
	Health and safety note: As with any former mining area, there may be hidden dangers involved from the presence of old shafts, adits, unsafe buildings etc. and special care is required, especially for younger (and elderly) participants. Visitors should also be aware '''of the insidious risk of heavy-metal poisoning (lead, zinc, copper etc.) both from mineral specimens and from the widespread contamination on the site. Precautions should therefore be taken with hygiene, especially during the consumption of packed lunches etc., both on site and afterwards.'''		Health and safety note: As with any former mining area, there may be hidden dangers involved from the presence of old shafts, adits, unsafe buildings etc. and special care is required, especially for younger (and elderly) participants. Visitors should also be aware '''of the insidious risk of heavy-metal poisoning (lead, zinc, copper etc.) both from mineral specimens and from the widespread contamination on the site. Precautions should therefore be taken with hygiene, especially during the consumption of packed lunches etc., both on site and afterwards.'''

Scotfot at 19:36, 30 March 2015

2015-03-30T19:36:36Z

← Older revision		Revision as of 20:36, 30 March 2015
Line 24:		Line 24:

	=== Excursion ===		=== Excursion ===
	[[File:LochDoonCarsphairnExcursionMap.jpg\|~~300px~~\|thumbnail\|Locality map and outline geology for the Loch Doon-Carsphairn area.]]		[[File:LochDoonCarsphairnExcursionMap.jpg\|400px\|thumbnail\|Locality map and outline geology for the Loch Doon-Carsphairn area.]]

	==== 1 Loch Doon Dam: Marchburn Formation greywacke ====		==== 1 Loch Doon Dam: Marchburn Formation greywacke ====

Scotfot: /* Excursion */

2015-03-30T19:36:14Z

Excursion

← Older revision		Revision as of 20:36, 30 March 2015
Line 24:		Line 24:

	=== Excursion ===		=== Excursion ===
			[[File:LochDoonCarsphairnExcursionMap.jpg\|300px\|thumbnail\|Locality map and outline geology for the Loch Doon-Carsphairn area.]]

	==== 1 Loch Doon Dam: Marchburn Formation greywacke ====		==== 1 Loch Doon Dam: Marchburn Formation greywacke ====