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 188: Line 188:
 
The acmes of arborescent lycopod spores (lycospores) of ''Lepidodendron''/''Lepidophloios ''forests in this HST is in keeping with a time of marine transgression and the formation of major areas of peat swamp. Other taxa that show temporary acmes within the zone include ''Cingulizonates loricatus, Radiizonates difformis, Camptotriletes bucculentus ''and ''Grumosisporites varioreticulatus. ''Influxes of inertinitic kerogen may be associated with structural changes in the Coal Measures flora and substrate associated with many intermittent and short-lived flooding events. Towards the top of the ''A. lenisulcata ''zone, pale amorphous organic matter appears, together with the persistent up-hole appearance of ''Laevigatosporites ''spp.
 
The acmes of arborescent lycopod spores (lycospores) of ''Lepidodendron''/''Lepidophloios ''forests in this HST is in keeping with a time of marine transgression and the formation of major areas of peat swamp. Other taxa that show temporary acmes within the zone include ''Cingulizonates loricatus, Radiizonates difformis, Camptotriletes bucculentus ''and ''Grumosisporites varioreticulatus. ''Influxes of inertinitic kerogen may be associated with structural changes in the Coal Measures flora and substrate associated with many intermittent and short-lived flooding events. Towards the top of the ''A. lenisulcata ''zone, pale amorphous organic matter appears, together with the persistent up-hole appearance of ''Laevigatosporites ''spp.
  
=== 7.2 Mid-Langsettian (''C. communis'' zone) ===
+
=== 7.2 Mid-Langsettian (C. communis zone) ===
  
In the East Midlands, the Burton Joyce Marine Band is taken as the base of the ''C. communis ''zone. Thick (up to 25 m) low-sinuosity channel sandstones occur towards the base of the zone, e.g. Grenoside Sandstone, Greenmoor Rock and Wingfield Flags, but the overall proportion of sandstone decreases upwards. The degree of downcutting and erosion above the Burton Joyce Marine Band is uncertain. A higher proportion of sandstone occurs in the zone, mostly high-sinuosity channel deposits (facies association A – channel-dominated coastal plain), in the offshore 44/22-1 ([[:File:YGS_CHR_06_ASEQ_FIG_06B.jpg|Figure 6B]]) than in the preceding ''A. lenisulcata ''zone, leading to the interpretation of ''C. communis ''zone as an LST. In 44/22-1 it is 236 m thick. Finer-grained, more argillaceous lithotypes with marine bands and coals become more common in the upper part of the zone (e.g. Kilburn Coal, Low Estheria Marine Band and Silkstone Coal). These may be associated with a diminishing rate of sea-level fall in the later stages of the LST, prior to the onset of renewed sea-level rise during the ensuing TST.
+
In the East Midlands, the Burton Joyce Marine Band is taken as the base of the ''C. communis ''zone. Thick (up to 25m) low-sinuosity channel sandstones occur towards the base of the zone, e.g. Grenoside Sandstone, Greenmoor Rock and Wingfield Flags, but the overall proportion of sandstone decreases upwards. The degree of downcutting and erosion above the Burton Joyce Marine Band is uncertain. A higher proportion of sandstone occurs in the zone, mostly high-sinuosity channel deposits (facies association A – channel-dominated coastal plain), in the offshore 44/22-1 ([[:File:YGS_CHR_06_ASEQ_FIG_06B.jpg|Figure 6B]]) than in the preceding ''A. lenisulcata ''zone, leading to the interpretation of ''C. communis ''zone as an LST. In 44/22-1 it is 236m thick. Finer-grained, more argillaceous lithotypes with marine bands and coals become more common in the upper part of the zone (e.g. Kilburn Coal, Low Estheria Marine Band and Silkstone Coal). These may be associated with a diminishing rate of sea-level fall in the later stages of the LST, prior to the onset of renewed sea-level rise during the ensuing TST.
  
 
The ''C. communis ''zone is characterized particularly by persistent and commonly marked local acmes of ''Crassispora kosankei''. This spore type is often particularly associated with coarser-grained sediments of an “alluvial swamp”, rather than a lycospore dominated peatswamp depositional environment. This form of swamp deposition may have characterized the interchannel areas during this time. Other important spore occurrences within this zone include ''Vestispora costata ''and ''V. tortuosa'', as well as the local development of ''Lophotriletes ''sp. A, together with the persistence of common ''Laevigatosporites ''spp.
 
The ''C. communis ''zone is characterized particularly by persistent and commonly marked local acmes of ''Crassispora kosankei''. This spore type is often particularly associated with coarser-grained sediments of an “alluvial swamp”, rather than a lycospore dominated peatswamp depositional environment. This form of swamp deposition may have characterized the interchannel areas during this time. Other important spore occurrences within this zone include ''Vestispora costata ''and ''V. tortuosa'', as well as the local development of ''Lophotriletes ''sp. A, together with the persistence of common ''Laevigatosporites ''spp.
  
The important Early Langsettian palynomorph marker ''Radiizonates aligerens ''became extinct within this zone, possibly reflecting the regional basinwide change to channel incision and major sandstone deposition of the following lowstand deposits, conditions that the donor plant could not tolerate. However, this palynomorph can occur in large numbers in the earlier parts of the zone and could be reworked into the overlying erosive HST and LST sandstones for more than 100 m above.
+
The important Early Langsettian palynomorph marker ''Radiizonates aligerens ''became extinct within this zone, possibly reflecting the regional basinwide change to channel incision and major sandstone deposition of the following lowstand deposits, conditions that the donor plant could not tolerate. However, this palynomorph can occur in large numbers in the earlier parts of the zone and could be reworked into the overlying erosive HST and LST sandstones for more than 100m above.
  
 
=== 7.3 Late Langsettian (Lower ''A. modiolaris'' zone) ===
 
=== 7.3 Late Langsettian (Lower ''A. modiolaris'' zone) ===

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: