Editing Introduction - St. Kilda: an illustrated account of the geology

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 9: Line 9:
  
 
The importance of St Kilda from cultural, regional and scientific points of view is now recognised and one of the fundamental requirements for making decisions about future developments affecting the islands is a source of reliable scientific data. To fulfill the geological aspect of this requirement, a team was formed in 1978 to produce a geological map and detailed report on the geology of the island group. Field mapping was carried out by the authors during the summers of 1978 and 1979 and sample collecting for laboratory analysis was shared with those contributing special chapters. The map contains its own summary of the geology and four itineraries to enable certain aspects of the geology to be seen in half or full day periods. The Report has been designed along modular lines and the list of contents shows that in general each major topic occupies a double page.
 
The importance of St Kilda from cultural, regional and scientific points of view is now recognised and one of the fundamental requirements for making decisions about future developments affecting the islands is a source of reliable scientific data. To fulfill the geological aspect of this requirement, a team was formed in 1978 to produce a geological map and detailed report on the geology of the island group. Field mapping was carried out by the authors during the summers of 1978 and 1979 and sample collecting for laboratory analysis was shared with those contributing special chapters. The map contains its own summary of the geology and four itineraries to enable certain aspects of the geology to be seen in half or full day periods. The Report has been designed along modular lines and the list of contents shows that in general each major topic occupies a double page.
 
== Geological history ==
 
 
{| Class="wikitable"
 
||'''''1'''''
 
||'''''Formation of early mafic complex'''''
 
|-
 
|A
 
|Initiation of magmatism in the vicinity of St Kilda, located at the intersection of lines of weakness in the Precambrian crust. Crystal accumulation from mafic magma to produce the Western Gabbro E''<sup>W</sup>''
 
|-
 
|B
 
|Intrusion of the Cambir Dolerite into solid but still hot E''<sup>W</sup>'' to form basic granulites and spinel-amphibole assemblages.
 
|-
 
|C
 
|Intrusion of dolerites and gabbros and disintegration of E''<sup>W</sup>'' with general uplift of these rocks during formation of the igneous breccia EK. Intrusion of basalts and explosion microbreccias at a high level (probably less than 5 km deep) accompanying surface volcanism. Hydrothermal activity during cooling and solidification of the EK breccia.
 
|-
 
|'''''2'''''
 
|'''''Formation of complex comprising a range of mafic rocks and major granitic components'''''
 
|-
 
|A
 
|Renewed surface volcanism followed by collapse of block of cold EK breccia into a basaltic magma chamber formed at a high level in the crust. Development of thick chilled zone round this block and formation of the Glen Bay Gabbro.
 
|-
 
|B
 
|Crushing of Glen Bay Gabbro followed by intrusion of Glen Bay Granite and then by porphyritic felsite dyke.
 
|-
 
|C
 
|Development of Mullach Sgar Complex involving at least four major intrusive phases each with felsic and mafic components. Intrusion of Glen Bay Dykes.
 
|-
 
|D
 
|Intrusion of Conachair Granite at a high level in the crust, with N or NNW fracturing of the Mullach Sgar Complex.
 
|-
 
|'''''3'''''
 
|'''''Uplift, loss of volatiles, minor intrusion and cooling'''''
 
|-
 
|A
 
|Consolidation of Conachair Granite followed by NW faulting and hydrothermal activity at temperatures between 260° and 100°C.
 
|-
 
|B
 
|Intrusion of dolerites and felsites as cone sheets and dykes; NE faulting.
 
|-
 
|C
 
|Zeolite-grade hydrothermal alteration accompanying final cooling of the St Kilda complex in reversed polarity geomagnetic field.
 
|-
 
|'''''4'''''
 
|'''''Erosion'''''
 
|-
 
|A
 
|Uplift and erosion during much of Tertiary time, with circumstantial evidence of some deposition.
 
|-
 
|B
 
|Erosion by glaciers and deposition of glacial and periglacial sediments; rise in sea level.
 
|}
 
  
 
==[[St. Kilda: an illustrated account of the geology#References|References]] ==
 
==[[St. Kilda: an illustrated account of the geology#References|References]] ==
 
{{EGwalks}}
 
{{EGwalks}}
 
[[Category: 2. Northern Highlands]]
 
[[Category: 2. Northern Highlands]]

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)

  [] · [[]] · [[|]] · {{}} · · “” ‘’ «» ‹› „“ ‚‘ · ~ | ° &nbsp; · ± × ÷ 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>

Templates used on this page: