Difference between revisions of "Category:Belemnite zonal scheme of Christensen (1995) for the Upper Campanian and Lower Maastrichtian of Norfolk"

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'''NB''': ''The species discussed below are based on a statistical analysis of measurements of morphological features. Therefore, recognition of the zones founded on these species cannot be readily made in the field from a visual  inspection of  the belemnite fauna.''
 
'''NB''': ''The species discussed below are based on a statistical analysis of measurements of morphological features. Therefore, recognition of the zones founded on these species cannot be readily made in the field from a visual  inspection of  the belemnite fauna.''
  
[[category:Biostratigraphy of the Chlak Group | 005]]
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[[category:Biostratigraphy of the Chalk Group | 005]]

Latest revision as of 11:38, 30 September 2013

Overview[edit]

Christensen (1995) recognised that many of the species concepts of Belemnitella in the Upper Campanian of Norfolk were poorly founded and difficult to apply, and noted that there was little widespread agreement about species concepts between researchers. To overcome these difficulties, Christensen (1995) undertook a detailed biometric analysis of Belemnitella populations in the Upper Campanian of Norfolk, and proposed several new species and a revised belemnite zonation for the succession. Christensen's (1995) approach is based on statistical analysis of measurements taken from numerous guards of Belemnitella, the results of which are then used to define species concepts. The stratigraphical ranges of the specimens belonging to these species are then used to define a biozonation. Many previously defined species of Belemnitella have been based on a qualitative assessment of external characteristics the value of which is questioned by Christensen (1995).

The bases of some of Christensen's (1995) zones and subzones are not precisely defined because of stratigraphical gaps in the Norfolk succession, and they are therefore regarded as informal concepts. The applicability of this zonation outside Norfolk has not been tested.

Descriptions of the Belemnitella zones of Christensen (1995) in the Upper Campanian and Lower Maastrichtian of Norfolk[edit]

The key features of the Upper Campanian Belemnitella zones recognised by Christensen (1995) in Norfolk are described from oldest to youngest. Alternatively, to find out information about a specific zone, select it from the correlation table (correlation of Upper Campanian Belemnitella zones recognised by Christensen (1995) in Norfolk with the standard macrofossil zonal scheme, brachiopod zonal scheme of Johansen & Surlyk (1990) and local lithostratigraphy).

NB: The species discussed below are based on a statistical analysis of measurements of morphological features. Therefore, recognition of the zones founded on these species cannot be readily made in the field from a visual inspection of the belemnite fauna.