Editing Carboniferous (Namurian and Westphalian) of the Cliviger Valley, Todmorden - an excursion

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 25: Line 25:
 
== Geological background ==
 
== Geological background ==
  
The Cliviger Valley straddles the Yorkshire/Lancashire border and at its head it marks the watershed of the drainage basins of these counties. It is also one of the most spectacular examples of a glacially over-deepened valley in the central Pennines. The incision of a glacial '''meltwater channel''' down the valley has caused the tributary streams to be left 'hanging' and these are currently actively cutting down into the bedrock, producing the numerous natural exposures of Carboniferous rocks that are the focus of this excursion.
+
The Cliviger Valley straddles the Yorkshire/Lancashire border and at its head it marks the watershed of the drainage basins of these counties. It is also one of the most spectacular examples of a glacially over-deepened valley in the central Pennines. The incision of a glacial meltwater channel down the valley has caused the tributary streams to be left 'hanging' and these are currently actively cutting down into the bedrock, producing the numerous natural exposures of Carboniferous rocks that are the focus of this excursion.
  
The rocks belong to the Namurian Series (usually called the Millstone Grit) and the Westphalian Series (or Coal Measures). Both series are characterized by a repetitive association of rock types caused by the repeated advance of sandy deltas into a deep water basin that occupied this part of the world in the late Carboniferous. These cycles ofsedimentation have been called '''cyclothems'''. They consist ideally of sediments that gradually coarsen upwards from shales through siltstones to sandstones. They are commonly capped by coals in the Coal Measures, though it should be noted that coals also occur in the Millstone Grit, and that their distinction from the Coal Measures is therefore somewhat arbitrary. As will be seen on the excursion, cyclothems are rarely ideally developed and the actual succession commonly consists of shale-siltstone sequences that are sharply overlain by sandstones which can vary greatly in thickness.
+
The rocks belong to the Namurian Series (usually called the Millstone Grit) and the Westphalian Series (or Coal Measures). Both series are characterized by a repetitive association of rock types caused by the repeated advance of sandy deltas into a deep water basin that occupied this part of the world in the late Carboniferous. These cycles ofsedimentation have been called cyclothems. They consist ideally of sediments that gradually coarsen upwards from shales through siltstones to sandstones. They are commonly capped by coals in the Coal Measures, though it should be noted that coals also occur in the Millstone Grit, and that their distinction from the Coal Measures is therefore somewhat arbitrary. As will be seen on the excursion, cyclothems are rarely ideally developed and the actual succession commonly consists of shale-siltstone sequences that are sharply overlain by sandstones which can vary greatly in thickness.
  
The shales at the bases of the cyclothems often contain a marine fauna which includes '''bivalves''' and '''goniatites'''. As the goniatites evolved very rapidly, each marine band usually contains a unique and diagnostic species that therefore facilitates their correlation.
+
The shales at the bases of the cyclothems often contain a marine fauna which includes bivalves and goniatites. As the goniatites evolved very rapidly, each marine band usually contains a unique and diagnostic species that therefore facilitates their correlation.
  
There is a fascinating local history of mineral extraction along the line of the Cliviger Valley '''Fault'''. Evidence for lead mining dates back to the early 17th century when most of the activity was centred around Thieveley Farm. Though little evidence remains, there are clues to the mining such as old drifts and spoil heaps (e.g. in the vicinity of Dean Scout, [SD 870 278]), where '''galena''' and '''baryte''' can still be collected if you are lucky. Iron also used to be extracted by the early Sheffield ironmasters from the Coal Measures of Riddle Scout where the shales contain common '''siderite concretions'''.
+
There is a fascinating local history of mineral extraction along the line of the Cliviger Valley Fault. Evidence for lead mining dates back to the early 17th century when most of the activity was centred around Thieveley Farm. Though little evidence remains, there are clues to the mining such as old drifts and spoil heaps (e.g. in the vicinity of Dean Scout, [SD 870 278]), where galena and baryte can still be collected if you are lucky. Iron also used to be extracted by the early Sheffield ironmasters from the Coal Measures of Riddle Scout where the shales contain common siderite concretions.
  
 
== Excursion details ==
 
== Excursion details ==

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>