Staca Fada Formation - close up 1
Staca Fada Formation - close up 2
Staca Fada - view south
Staca Fada - view west
Meall Dubh
Meall Dubh from Meall Dubh
Raffin cottages after the rain
Clachtoll old settlement with lazy beds
Handa Island - view SSW over Tràigh Shourie panor…
Handa Island - shower and Stoer peninsula
Handa Island - geo at Traigh na h-Airigh 2
Handa Island - geo at Traigh na h-Airigh
Handa Island - shower over Glas Leac and Stoer Pen…
Raffin shore seaweed 1
Raffin shore seaweed 2 - Bladder wrack
Raffin shore seaweed 3
Raffin shore seaweed 4 - close-up of Bladder wrack
Raffin shore seaweed 5
Raffin shore sheep tracks?
Rubha Fitheacaig: Lewisian gneiss and Scourie dyke
Clashnessie Bay and Quinag
Butterfly orchid on the Culkein roadside
Bay of Culkein and natural sea arch
Old Man of Stoer 1
Old Man of Stoer 2
Point of Stoer cotton grass and Quinag 1
Point of Stoer cotton grass
Point of Stoer cotton grass and Quinag 2
Point of Stoer cloudscape
Point of Stoer cotton grass and Handa Island
Old Man of Stoer from Point of Stoer
Stoer cloudscape south from Sidhean Mòr
Loch Cùl Fraioch and the Torridonian mountains fro…
Quinag from Stoer peninsula
Stac Fada Formation - possible cooling joints? 1
Stac Fada Formation
Bay of Stoer and Stac Fada
Bay of Stoer - north west
Bay of Stoer - bands of colour
Bay of Stoer - south west view
Clachtoll lochan with water lilies 2
A' Clach Thuill south from Airn na Mòine 2
A' Clach Thuill south from Airn na Mòine 1
Gneiss erratic on Bay of Stoer Formation at Sgèir…
Sgèir na Tràghad bedding planes and sea
Sgèir na Tràghad panorama
Gneiss erratic on Bay of Stoer Formation at Sgèir…
Bay of Stoer Formation bedding plane
Sgèir na Tràghad 2
Sgèir na Tràghad 1
Bay of Stoer view NNW panorama x2 vertical exagger…
Clachtoll lochan with water lilies
Broch An Dùn south side 2
Broch An Dùn south side
Bay of Stoer from Clachtoll broch An Dùn
Bay of Stoer NNW panorama
View north to Stac Fada from Clachtoll broch An Dù…
Broch An Dùn north side 2
Broch An Dùn north side 3
Broch An Dùn north side 1
Gneiss erratic on Stoer Group at Druim na Claise 1
Gneiss erratic field on Stoer Group at Druim na Cl…
Bog Asphodel at Druim na Claise
Gneiss erratic on Stoer Group at Druim na Claise 3
Gneiss erratic on Stoer Group at Druim na Claise 2
Assynt mountains from Raffin shore 2
Assynt mountains from Raffin shore 2
Suliven over Balchladich Bay 2
Assynt mountains over Raffin shore
Cotton grass by Raffin shore
Assynt mountains from Raffin shore
Suliven over Balchladich Bay
Balchladich Bay, Stoer peninsula, Sutherland
Landscape with clouds
Stoer Head lighthouse
Suilven from Sìdhean Mòr
Sunny Culkein
Loch Cùl Fraioch and the Torridonian mountains
Old Man of Stoer
Old Man from Point of Stoer
Stoer cloudscape
1/250 • f/11.0 • 38.0 mm • ISO 200 •
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Stac Fada Formation - possible cooling joints? 2
Stac Fada at the northern end of the Bay of Stoer, north west Scotland, is the type locality for the Stac Fada Formation, recently interpreted as a meteorite impact debris horizon, comparable with suevite from the much younger (Miocene, 15 Ma) Ries meteorite impact event in south Germany. The Stac Fada Formation lies within the Bay of Stoer Formation, mostly fluviatile sandstones and siltstones (Mesoproterozoic, c. 1200 Ma).
The Stac Fada Formation is about 12 metres thick at this location. The photo shows a part of the middle section and consists of a poorly bedded arkosic sand matrix within which there are dark green chloritised clasts and fragments which represent formerly molten debris blasted into the air from the original impact. There is a network of polygonal cracks visible on this 'bedding' surface and I theorise that these may be cooling joints formed as the presumably hot ejecta deposit cooled and contracted. (I have seen no reference to this particular feature in the literature).
The site of the meteorite impact is now correlated with a well-defined, roughly circular, low-gravity anomaly some 50 km to the east, near the village of Lairg, although any impact crater is now buried beneath younger rocks. SEE UPDATE BELOW.
For more details see:
Simms, M. J., 2015. The Stac Fada impact ejecta deposit and the Lairg Gravity Low: evidence for a buried Precambrian impact crater in Scotland?, Proceedings of the Geologists Association, 126 (2015), 742 - 761.
UPDATE June 2019:
Latest research based on detailed field observations, geochemical and geomagnetic work now seems to indicate that the impact site is located in the present day Minch, about 15 - 20 km WNW of Enard Bay. See:
Amor, K. et al, 2019. The Mesoproterozoic Stac Fada proximal ejecta blanket, NW Scotland: constraints on crater location from field observations, anisotropy of magnetic susceptibility, petrography and geochemistry. Journal of the Geological Society 176/4 (2019).
dx.doi.org/10.1144/jgs2018-093
The Stac Fada Formation is about 12 metres thick at this location. The photo shows a part of the middle section and consists of a poorly bedded arkosic sand matrix within which there are dark green chloritised clasts and fragments which represent formerly molten debris blasted into the air from the original impact. There is a network of polygonal cracks visible on this 'bedding' surface and I theorise that these may be cooling joints formed as the presumably hot ejecta deposit cooled and contracted. (I have seen no reference to this particular feature in the literature).
The site of the meteorite impact is now correlated with a well-defined, roughly circular, low-gravity anomaly some 50 km to the east, near the village of Lairg, although any impact crater is now buried beneath younger rocks. SEE UPDATE BELOW.
For more details see:
Simms, M. J., 2015. The Stac Fada impact ejecta deposit and the Lairg Gravity Low: evidence for a buried Precambrian impact crater in Scotland?, Proceedings of the Geologists Association, 126 (2015), 742 - 761.
UPDATE June 2019:
Latest research based on detailed field observations, geochemical and geomagnetic work now seems to indicate that the impact site is located in the present day Minch, about 15 - 20 km WNW of Enard Bay. See:
Amor, K. et al, 2019. The Mesoproterozoic Stac Fada proximal ejecta blanket, NW Scotland: constraints on crater location from field observations, anisotropy of magnetic susceptibility, petrography and geochemistry. Journal of the Geological Society 176/4 (2019).
dx.doi.org/10.1144/jgs2018-093
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