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

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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.''
  
=== 7.7 Late Bolsovian (''A. phillipsii'' zone) ===
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=== 7.7 Late Bolsovian (A. phillipsii zone) ===
  
A final marine flooding event, the Cambriense Marine Band, occurs at the base of this zone (Calver 1968, Flint et al. 1995, Guion et al. 1995). After this marine band was deposited, uplift and tectonic inversion prevented any further marine incursions (Leeder & Hardman 1990). Grey coal-bearing rocks become much reduced in volume, and redbed sedimentation was more widespread. The zone is interpreted as representing an LST, and is 143 m thick in 44/27-1. It is characterized by a relatively high proportion of sandstone, as base-level fall led to a significant increase in alluvial vigour, with incision and deposition of thick sheets of laterally and vertically linked low- and high-sinuosity channel sandstones up to 30 m thick (facies association A). On shore, widespread sandstones include the Ackworth, Wickersley and Ravenfield rocks. Subordinate claystones and siltstones and several thin, laterally impersistent coal seams are developed. Several such sandstone units are developed in 44/27-1, although in this well none exceed 20 m in thickness ([[:File:YGS_CHR_06_ASEQ_FIG_07D.jpg|Figure 7D]]). Finer-grained crevasse-splay, mouth bar and lake or swamp sedimentation in interchannel areas was comparatively shortlived. Coals developed within this zone are therefore liable to be of a poorer quality with a higher ash content. Interchannel areas were also prone to erosion by the stream avulsion.
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A final marine flooding event, the Cambriense Marine Band, occurs at the base of this zone (Calver 1968, Flint et al. 1995, Guion et al. 1995). After this marine band was deposited, uplift and tectonic inversion prevented any further marine incursions (Leeder & Hardman 1990). Grey coal-bearing rocks become much reduced in volume, and redbed sedimentation was more widespread. The zone is interpreted as representing an LST, and is 143m thick in 44/27-1. It is characterized by a relatively high proportion of sandstone, as base-level fall led to a significant increase in alluvial vigour, with incision and deposition of thick sheets of laterally and vertically linked low- and high-sinuosity channel sandstones up to 30m thick (facies association A). On shore, widespread sandstones include the Ackworth, Wickersley and Ravenfield rocks. Subordinate claystones and siltstones and several thin, laterally impersistent coal seams are developed. Several such sandstone units are developed in 44/27-1, although in this well none exceed 20m in thickness ([[:File:YGS_CHR_06_ASEQ_FIG_07D.jpg|Figure 7D]]). Finer-grained crevasse-splay, mouth bar and lake or swamp sedimentation in interchannel areas was comparatively shortlived. Coals developed within this zone are therefore liable to be of a poorer quality with a higher ash content. Interchannel areas were also prone to erosion by the stream avulsion.
  
 
The alluvial swamp spore ''Crassispora kosankei ''reaches its acme within this zone, reflecting a final period of major alluvial swamp deposition prior to the Late Westphalian climatic change. Lowstand sedimentation, with its reduced accommodation space had a profound effect on the palynofloras. ''Densosporites sphaerotriangularis, Vestispora costata, V. pseudoreticulata, Savitrisporites nux, Dictyotriletes falsus ''and ''Grumosisporites varioreticulatus, ''seen since the Early Westphalian, became extinct within this zone. New taxa appearing within the zone include ''Schopfites dimorphus ''and ''Vestispora laevigata ''(Van Adrichem Boorgaert & Kouwe 1993). Palynological assemblages from this zone commonly contain reworked Early Westphalian or Namurian taxa.
 
The alluvial swamp spore ''Crassispora kosankei ''reaches its acme within this zone, reflecting a final period of major alluvial swamp deposition prior to the Late Westphalian climatic change. Lowstand sedimentation, with its reduced accommodation space had a profound effect on the palynofloras. ''Densosporites sphaerotriangularis, Vestispora costata, V. pseudoreticulata, Savitrisporites nux, Dictyotriletes falsus ''and ''Grumosisporites varioreticulatus, ''seen since the Early Westphalian, became extinct within this zone. New taxa appearing within the zone include ''Schopfites dimorphus ''and ''Vestispora laevigata ''(Van Adrichem Boorgaert & Kouwe 1993). Palynological assemblages from this zone commonly contain reworked Early Westphalian or Namurian taxa.

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