Editing A sequence-stratigraphy scheme of the Late Carboniferous, southern North Sea, Anglo-Dutch sector

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 29: Line 29:
 
== 1. Basin setting ==
 
== 1. Basin setting ==
  
The Coal Measures were deposited between 315 and 296 Ma within an equatorial belt that stretched from the Moscow–Donetz Basin to the eastern USA (Harland et al. 1982, Lippolt et al. 1984, Leeder 1988). This region formed a large, low-lying, shallow marine or lowland alluvial coastal plain to the north of the Variscan orogenic belt (Bambach et al. 1980). Coal seams are derived from peat accumulation that kept pace with conditions of slowly rising base level, allowing the mire to be sustained (Aitken 1994, Aitken & Flint 1994). The overall effect of slowly rising relative base level is to retard clastic supply as rivers aggrade and the increase in accommodation space moves landwards (Moore 1987, Anderson 1983). Large areas of high water table and limited introduction of clastic material provide ideal conditions for widespread ombrotrophic (rainwater-fed and dome shape) peatswamp development. These conditions persisted for long periods of time over large areas of the Coal Measures basin until terminated by a rise in sea level that led to flooding of the forest area, or until crevassing of alluvial channels introduced large quantities of clastic sediments. The encroachment and continental collision forming the Variscan orogeny were complete by the Stephanian and they terminated Coal Measures sedimentation.
+
The Coal Measures were deposited between 315 and 296Ma within an equatorial belt that stretched from the Moscow– Donetz Basin to the eastern USA (Harland et al. 1982, Lippolt et al. 1984, Leeder 1988). This region formed a large, low-lying, shallow marine or lowland alluvial coastal plain to the north of the Variscan orogenic belt (Bambach et al. 1980). Coal seams are derived from peat accumulation that kept pace with conditions of slowly rising base level, allowing the mire to be sustained (Aitken 1994, Aitken & Flint 1994). The overall effect of slowly rising relative base level is to retard clastic supply as rivers aggrade and the increase in accommodation space moves landwards (Moore 1987, Anderson 1983). Large areas of high water table and limited introduction of clastic material provide ideal conditions for widespread ombrotrophic (rainwater-fed and dome shape) peatswamp development. These conditions persisted for long periods of time over large areas of the Coal Measures basin until terminated by a rise in sea level that led to flooding of the forest area, or until crevassing of alluvial channels introduced large quantities of clastic sediments. The encroachment and continental collision forming the Variscan orogeny were complete by the Stephanian and they terminated Coal Measures sedimentation.
  
The main source of sediments into the basin during the Late Carboniferous was from the north (Leeder & Hardman 1990, Collinson et al. 1993, Guion et al. 1995, Morton et al. 2005). There is a gradation from proximal areas in the north to distal environments and palaeotopographically lower areas to the south. Wireline log profiles of wells across the southern North Sea show a northward regional coarsening trend and development of thicker and more numerous sandstones. Calver (1968) recognized lateral changes in facies belts within individual marine bands across the coalfields of the UK, which reflect the extent of marine incursion and associated salinity variations. However, for most of the Westphalian sequence, this north–south facies change occurred within freshwater environments, from upper coastal plain with low-sinuosity channels, through lower coastal plain with high-sinuosity channels, into a fluviolacustrine environment (Guion et al. 1995). Similar north–south aligned facies belts can be recognized in the southern North Sea gas basin (Quirk 1993).
+
The main source of sediments into the basin during the Late Carboniferous was from the north (Leeder & Hardman 1990, Collinson et al. 1993, Guion et al. 1995, Morton et al. 2005).
 +
 
 +
There is a gradation from proximal areas in the north to distal environments and palaeotopographically lower areas to the south. Wireline log profiles of wells across the southern North Sea show a northward regional coarsening trend and development of thicker and more numerous sandstones. Calver (1968) recognized lateral changes in facies belts within individual marine bands across the coalfields of the UK, which reflect the extent of marine incursion and associated salinity variations. However, for most of the Westphalian sequence, this north– south facies change occurred within freshwater environments, from upper coastal plain with low-sinuosity channels, through lower coastal plain with high-sinuosity channels, into a fluviolacustrine environment (Guion et al. 1995). Similar north–south aligned facies belts can be recognized in the southern North Sea gas basin (Quirk 1993).
  
 
The Wales–Brabant Island that formed the southwestern boundary of the Anglo-Dutch Southern North Sea Basin was an area of subdued topography throughout much of Westphalian time. It has been generally considered as being a limited source of detritus to the basin except in southerly areas (Kirk 1989, Besly 1990, Fraser & Gawthorpe 1990, Quirk 1993). However, Hallsworth & Chisholm (2000) and Morton et al. (2005) have presented evidence that sediment from this source was more widely dispersed from Late Duckmantian times onwards. Southerly derived detritus is also relatively abundant in The Netherlands (Collinson et al. 1993). Evidence for a major westerly source of detritus in the Westphalian has been found in northern England (Hallsworth & Chisholm 2000), but so far this is unknown off shore.
 
The Wales–Brabant Island that formed the southwestern boundary of the Anglo-Dutch Southern North Sea Basin was an area of subdued topography throughout much of Westphalian time. It has been generally considered as being a limited source of detritus to the basin except in southerly areas (Kirk 1989, Besly 1990, Fraser & Gawthorpe 1990, Quirk 1993). However, Hallsworth & Chisholm (2000) and Morton et al. (2005) have presented evidence that sediment from this source was more widely dispersed from Late Duckmantian times onwards. Southerly derived detritus is also relatively abundant in The Netherlands (Collinson et al. 1993). Evidence for a major westerly source of detritus in the Westphalian has been found in northern England (Hallsworth & Chisholm 2000), but so far this is unknown off shore.

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: