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

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Certain other taxa may not have been able to survive the demise of these very extensive and persistent settled swamp environments. This may have been associated with a decline in the rate of sea-level rise, and the sedimentation rate may have begun to exceed subsidence rates. Various taxa became extinct at the top of this zone, including ''Raistrickia fulva, ''abundant ''Dictyotriletes bireticulatus ''and ''Camptotriletes bucculentus.''
 
Certain other taxa may not have been able to survive the demise of these very extensive and persistent settled swamp environments. This may have been associated with a decline in the rate of sea-level rise, and the sedimentation rate may have begun to exceed subsidence rates. Various taxa became extinct at the top of this zone, including ''Raistrickia fulva, ''abundant ''Dictyotriletes bireticulatus ''and ''Camptotriletes bucculentus.''
  
=== 7.6 Early Bolsovian (U. ''similis-pulchra'' zone) ===
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=== 7.6 Early Bolsovian (U. similis-pulchra zone) ===
  
The widely recognizable Aegiranum Marine Band marks the MFS at the base of the zone, which is interpreted as a HST. The zone is 183 m thick in well 44/27-1. It is characterized by argillaceous lithologies, crevasse-splay and lake deposits, with intervening swamp or lake units. Several coals are present in the lower half of the zone, and marine bands (Edmondia, Main Estheria and Shafton) indicative of flooding events are recognizable higher up in the sequence. Some sandstone bodies, up to 15 m in thickness (facies association B), are locally present (e.g. above the Edmondia Marine Band), although none is evident in the reference well 44/27-1 ([[:File:YGS_CHR_06_ASEQ_FIG_07C.jpg|Figure 7C]]).
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The widely recognizable Aegiranum Marine Band marks the MFS at the base of the zone, which is interpreted as a HST. The zone is 183m thick in well 44/27-1. It is characterized by argillaceous lithologies, crevasse-splay and lake deposits, with intervening swamp or lake units. Several coals are present in the lower half of the zone, and marine bands (Edmondia, Main Estheria and Shafton) indicative of flooding events are recognizable higher up in the sequence. Some sandstone bodies, up to 15m in thickness (facies association B), are locally present (e.g. above the Edmondia Marine Band), although none is evident in the reference well 44/27-1 ([[:File:YGS_CHR_06_ASEQ_FIG_07C.jpg|Figure 7C]]).
  
 
Lycospores, indicative of peatswamp sedimentation, and the alluvial swamp spore ''Crassispora kosankei'', are consistently present throughout this zone. In contrast with the extinctions associated with Vanderbeckei marine incursion, noted above, several spore taxa continue into the ''U. similis-pulchra ''zone. However, the widespread Aegiranum Marine Band must have caused a major disturbance within the basin, severely limiting the area from which swamp taxa could later repopulate the basin. One taxon that became extinct at this horizon was ''Cingulizonates loricatus. ''Spore taxa appearing within this zone include ''Vestispora fenestrata, Torispora securis, Triquitrites bransonii ''and ''Punctatisporites granifer.''
 
Lycospores, indicative of peatswamp sedimentation, and the alluvial swamp spore ''Crassispora kosankei'', are consistently present throughout this zone. In contrast with the extinctions associated with Vanderbeckei marine incursion, noted above, several spore taxa continue into the ''U. similis-pulchra ''zone. However, the widespread Aegiranum Marine Band must have caused a major disturbance within the basin, severely limiting the area from which swamp taxa could later repopulate the basin. One taxon that became extinct at this horizon was ''Cingulizonates loricatus. ''Spore taxa appearing within this zone include ''Vestispora fenestrata, Torispora securis, Triquitrites bransonii ''and ''Punctatisporites granifer.''

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