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

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=== 7.3 Late Langsettian (Lower ''A. modiolaris'' zone) ===
 
=== 7.3 Late Langsettian (Lower ''A. modiolaris'' zone) ===
  
Above the basal flooding surface, taken at the Tupton Coal, this zone is characterized by channel sandstones of low and high sinuosity, such as the Penistone Flags and the Parkgate Rock equivalents. It also contains significant intervals of finer-grained crevasse-splay and swamp and lake strata, with coals ([[:File:YGS_CHR_06_ASEQ_FIG06C.jpg|Figure 6C]]). This zone has been designated a TST; it is 70 m thick in well 44/22-1. Many important coals also occur in the uppermost part of the zone, the Parkgate–Piper, Deep Hard, Flockton and Joan, possibly representing flooding surfaces, although no marine bands have been recorded within it up to the MFS of the Vanderbeckei (Clay Cross) Marine Band.
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Above the basal flooding surface, taken at the Tupton Coal, this zone is characterized by channel sandstones of low and high sinuosity, such as the Penistone Flags and the Parkgate Rock equivalents. It also contains significant intervals of finer-grained crevasse-splay and swamp and lake strata, with coals ([[:File:YGS_CHR_06_ASEQ_FIG06C.jpg|Figure 6C]]). This zone has been designated a TST; it is 70m thick in well 44/22-1. Many important coals also occur in the uppermost part of the zone, the Parkgate–Piper, Deep Hard, Flockton and Joan, possibly representing flooding surfaces, although no marine
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bands have been recorded within it up to the MFS of the Vanderbeckei (Clay Cross) Marine Band.
  
 
This interval is characterized by common ''Lycospora ''spp., with reduced abundances of ''Crassispora kosankei ''and ''Laevigatosporites ''spp. ''Krauselisporites ''spp., ''Punctatisporites nitidus ''and ''P. limbatus ''are particularly prominent within this zone, which may be a direct response to the transgressive depositional regime. Several other spore groups also dominate lake clay-stones and associated coal swamps. For example, ''Schulzospora rara ''is a very distinctive form, which reaches its acme in the uppermost part of the Langsettian and then terminates within the Joan Coal and coeval equivalents at the Westphalian A/B boundary. In South Wales, this form is commonly observed associated with coals at three distinct horizons. In the 49 Quadrant it has been observed commonly at two distinct horizons. Farther north in Quadrant 44 and onshore UK it is only widely observed within the uppermost horizon (Joan Coal). Even farther north, towards Tyneside and the Scottish coalfields, this taxon is rare or absent (see [[:File:YGS_CHR_06_ASEQ_FIG_10.jpg|Figure 10]]). A possible interpretation of this distribution may be that ''S. rara ''was associated with coastal brackish swamps and that its decreasing frequency northwards records the brackish edge of marine incursion that progressively diminished up palaeoslope within this TST.
 
This interval is characterized by common ''Lycospora ''spp., with reduced abundances of ''Crassispora kosankei ''and ''Laevigatosporites ''spp. ''Krauselisporites ''spp., ''Punctatisporites nitidus ''and ''P. limbatus ''are particularly prominent within this zone, which may be a direct response to the transgressive depositional regime. Several other spore groups also dominate lake clay-stones and associated coal swamps. For example, ''Schulzospora rara ''is a very distinctive form, which reaches its acme in the uppermost part of the Langsettian and then terminates within the Joan Coal and coeval equivalents at the Westphalian A/B boundary. In South Wales, this form is commonly observed associated with coals at three distinct horizons. In the 49 Quadrant it has been observed commonly at two distinct horizons. Farther north in Quadrant 44 and onshore UK it is only widely observed within the uppermost horizon (Joan Coal). Even farther north, towards Tyneside and the Scottish coalfields, this taxon is rare or absent (see [[:File:YGS_CHR_06_ASEQ_FIG_10.jpg|Figure 10]]). A possible interpretation of this distribution may be that ''S. rara ''was associated with coastal brackish swamps and that its decreasing frequency northwards records the brackish edge of marine incursion that progressively diminished up palaeoslope within this TST.

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