Editing St Fergus (Annachie) - locality, Cainozoic of north-east Scotland

Jump to navigation Jump to search

Warning: You are not logged in. Your IP address will be publicly visible if you make any edits. If you log in or create an account, your edits will be attributed to your username, along with other benefits.

The edit can be undone. Please check the comparison below to verify that this is what you want to do, and then save the changes below to finish undoing the edit.

This page supports semantic in-text annotations (e.g. "[[Is specified as::World Heritage Site]]") to build structured and queryable content provided by Semantic MediaWiki. For a comprehensive description on how to use annotations or the #ask parser function, please have a look at the getting started, in-text annotation, or inline queries help pages.

Latest revision Your text
Line 2: Line 2:
 
__FORCETOC__
 
__FORCETOC__
 
= St Fergus =
 
= St Fergus =
[[File:P915377.png|left|thumbnail|Glacial and glaciofluvial features and the distribution of glacigenic deposits on Sheet 87E Peterhead. P915377.]]
+
[[File:P915377.png|thumbnail|P915377]]
[[File:P915347.png|thumbnail|Correlation of lithostratigraphical units in north-east Scotland. P915347.]]
+
[[File:P915314.png|thumbnail|P915314]]
Interest in the Quaternary deposits around St Fergus, 6 km north-west of Peterhead [[Media:P915377.png|(P915377)]], began in the mid-19th century following the discovery of an apparently in situ arctic marine fauna (Jamieson, 1858, 1906). It occurred in a stoneless grey clay exposed in a former brick pit close to present sea level near Annachie (NK 105 532) [[Media:P915314.png|(P915314)]]. Similar deposits were subsequently encountered in BGS boreholes drilled to the east of the village (McMillan and Aitken, 1981) and in site investigations and construction works at the gas terminal from 1980 onwards. The dominantly massive, very dark grey to dark greenish grey, calcareous silts containing shelly horizons were described and named as the St Fergus Silts by Hall and Jarvis (1989). The unit is named formally here as the [[Banffshire Coast Drift Group, Quaternary lithostratigraphy, Cainozoic of north-east Scotland#St Fergus Silt Formation|St Fergus Silt Formation]] of the Banffshire Coast Drift Group [[Media:P915347.png|(P915347)]]. Early geomorphological work in the area by Walton (1956) and Donner (1963) indicates the presence of raised beach deposits in the area to heights of up to about 30 m above OD, but the most prominent feature was reported at about 15 m OD.
+
[[File:P915347.png|thumbnail|P915347]]
 +
[[File:P915312.png|thumbnail|P915312]]
 +
[[File:P915288.png|thumbnail|P915288]]
 +
Interest in the Quaternary deposits around St Fergus, 6 km north-west of Peterhead (Map P915377), began in the mid-19th century following the discovery of an apparently in situ arctic marine fauna (Jamieson, 1858, 1906). It occurred in a stoneless grey clay exposed in a former brick pit close to present sea level near Annachie (NK 105 532) (P915314). Similar deposits were subsequently encountered in BGS boreholes drilled to the east of the village (McMillan and Aitken, 1981) and in site investigations and construction works at the gas terminal from 1980 onwards. The dominantly massive, very dark grey to dark greenish grey, calcareous silts containing shelly horizons were described and named as the St Fergus Silts by Hall and Jarvis (1989). The unit is named formally here as the St Fergus Silt Formation of the Banffshire Coast Drift Group (Chapter 8; P915347). Early geomorphological work in the area by Walton (1956) and Donner (1963) indicates the presence of raised beach deposits in the area to heights of up to about 30 m above OD, but the most prominent feature was reported at about 15 m OD.
  
[[File:P915312.png|left|thumbnail|Landforms and deposits in and adjacent to the Ugie catchment. P915312.]]
+
'''St Fergus Silt Formation '''occurs on sheets 87E Peterhead and 97 Fraserburgh where it is overlain mainly by alluvial deposits, including peat and lacustrine silt, which mark the site of a former freshwater loch (Anderson ''in ''Scott, 1890), and by blown sand (Glentworth and Muir, 1963). The formation probably extends to the north of the Loch of Strathbeg (P915312) where grey plastic clays have been recorded (Wilson, 1886). Dark grey sandy silts and clays are also widespread beneath terraced glaciofluvial sand and gravel deposits in the vicinity of Savoch (NK 047 588) and dark grey silts occur at 9 m above OD at Coralhill (NK 061 607). The southern boundary of the formation is obscured by thick surface peat and/or organic mud, but probably lies immediately south-east of St Fergus village. To the west, the St Fergus Silt Formation is bounded by a till slope and a Late-glacial raised beach at about 16 m OD, whereas to the east, the deposits locally form the backslope of the abandoned Postglacial (Flandrian) cliff (Figure A1.15).
[[File:P915314.png|thumbnail|Localities at St Fergus (after Peacock, 1999). P915314.]]
 
'''St Fergus Silt Formation '''occurs on sheets 87E Peterhead and 97 Fraserburgh where it is overlain mainly by alluvial deposits, including peat and lacustrine silt, which mark the site of a former freshwater loch (Anderson ''in ''Scott, 1890), and by blown sand (Glentworth and Muir, 1963). The formation probably extends to the north of the Loch of Strathbeg [[Media:P915312.png|(P915312)]] where grey plastic clays have been recorded (Wilson, 1886). Dark grey sandy silts and clays are also widespread beneath terraced glaciofluvial sand and gravel deposits in the vicinity of Savoch (NK 047 588) and dark grey silts occur at 9 m above OD at Coralhill (NK 061 607). The southern boundary of the formation is obscured by thick surface peat and/or organic mud, but probably lies immediately south-east of St Fergus village. To the west, the St Fergus Silt Formation is bounded by a till slope and a Late-glacial raised beach at about 16 m OD, whereas to the east, the deposits locally form the backslope of the abandoned Postglacial (Flandrian) cliff [[Media:P915314.png|(P915314)]].
 
  
The dark grey silts, clays and fine-grained sands of the St Fergus Silt Formation form a generally coarsening upwards succession (Peacock, 1999) with a maximum reported thickness of about 16 m above (McMillan and Aitken, 1981). The surface level is generally 7 to 10 m, but locally up to 16 m above OD adjacent to a low ridge that borders the outcrop to the north of Annachie Bridge (NK 105 531) [[Media:P915314.png|(P915314)]] and extends towards Rattray Head. Exposures of faulted, tilted and deformed masses of bedded silt and sand in the ridge led Hall and Jarvis (1989) to interpret the feature as a (push) moraine formed by a re-advance of ice from the east or north-east. This conclusion is supported by borehole evidence that indicates that the St Fergus Silt Formation passes under, and is therefore mainly older than the moraine feature. If correct, the surface level of the formation in the vicinity of the ridge is likely to be anomalous due to proglacial glacitectonic disturbance. A cutting through the cliffline backing the Flandrian raised beach at Pittenheath (NK 104 554) also revealed faulted, tilted and sheared masses of bedded sand and black clay.
+
The dark grey silts, clays and fine-grained sands of the St Fergus Silt Formation form a generally coarsening upwards succession (Peacock, 1999) with a maximum reported thickness of about 16 m above (McMillan and Aitken, 1981). The surface level is generally 7 to 10 m, but locally up to 16 m above OD adjacent to a low ridge that borders the outcrop to the north of Annachie Bridge (NK 105 531) (Figure A1.15) and extends towards Rattray Head. Exposures of faulted, tilted and deformed masses of bedded silt and sand in the ridge led Hall and Jarvis (1989) to interpret the feature as a (push) moraine formed by a re-advance of ice from the east or north-east. This conclusion is supported by borehole evidence that indicates that the St Fergus Silt Formation passes under, and is therefore mainly older than the moraine feature. If correct, the surface level of the formation in the vicinity of the ridge is likely to be anomalous due to proglacial glacitectonic disturbance. A cutting through the cliffline backing the Flandrian raised beach at Pittenheath (NK 104 554) also revealed faulted, tilted and sheared masses of bedded sand and black clay.
  
 
Another low north-trending ridge is cut by the cliffline just to the north of St Fergus village (NK 097 522). In 1990, the ridge was observed to consist of planar and ripple bedded sand with thin beds of gravel and red diamicton and local ‘streaks’ of grey clay and clayey sand. The sequence is folded into a gentle anticline trending parallel to the ridge and is down-faulted to the east locally. The ridge is draped and flanked by reddish brown diamicton. The folding may either have been associated with the advance that formed the other ridge at St Fergus, or an earlier incursion of the ‘Logie-Buchan’ ice stream.
 
Another low north-trending ridge is cut by the cliffline just to the north of St Fergus village (NK 097 522). In 1990, the ridge was observed to consist of planar and ripple bedded sand with thin beds of gravel and red diamicton and local ‘streaks’ of grey clay and clayey sand. The sequence is folded into a gentle anticline trending parallel to the ridge and is down-faulted to the east locally. The ridge is draped and flanked by reddish brown diamicton. The folding may either have been associated with the advance that formed the other ridge at St Fergus, or an earlier incursion of the ‘Logie-Buchan’ ice stream.

Please note that all contributions to Earthwise may be edited, altered, or removed by other contributors. If you do not want your writing to be edited mercilessly, then do not submit it here.
You are also promising us that you wrote this yourself, or copied it from a public domain or similar free resource (see Earthwise:Copyrights for details). Do not submit copyrighted work without permission!

Cancel Editing help (opens in new window)

  [] · [[]] · [[|]] · {{}} · · “” ‘’ «» ‹› „“ ‚‘ · ~ | °   · ± × ÷ ² ³ ½ · §
[[Category:]] · [[:File:]] · <code></code> · <syntaxhighlight></syntaxhighlight> · <includeonly></includeonly> · <noinclude></noinclude> · #REDIRECT[[]] · <translate></translate> · <languages/> · ==References== · {{reflist}} · ==Footnote== · {{reflist|group=note}} · <ref group=note> · __notoc__ · {{DEFAULTSORT:}} <div class="someclass noprint"></div> {{clear}} <br>

Template used on this page: