Mantelliceras dixoni Zone: Difference between revisions
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| Brachiopoda: | | Brachiopoda: || ''Orbirhynchia mantelliana'' | ||
|- | |- | ||
| Bivalvia: | | Bivalvia: || ''Inoceramus virgatus'' | ||
|- | |- | ||
| Ammonoidea: ''Acompsoceras'' spp. | | Ammonoidea: ||''Acompsoceras'' spp. | ||
|- | |- | ||
| ||''Hyphoplites'' spp. | | ||''Hyphoplites'' spp. | ||
|- | |||
| ||''Mantelliceras dixoni'' | | ||''Mantelliceras dixoni'' | ||
|- | |||
| ||''M. saxbii'' | | ||''M. saxbii'' | ||
|- | |||
| ||''M''. spp. | |||
|- | |||
| ||''Mesoturrilites'' spp. | |||
|} | |||
'''Faunal abundance & preservation''': Some fauna present as acmes (''O. mantelliana'', ''I.'' ''virgatus''), and ''M. dixoni'' is locally abundant in a hard limestone bed (see: Bio-markers). | '''Faunal abundance & preservation''': Some fauna present as acmes (''O. mantelliana'', ''I.'' ''virgatus''), and ''M. dixoni'' is locally abundant in a hard limestone bed (see: Bio-markers). | ||
'''Bio-markers''': An acme of ''Inoceramus virgatus'' occurs slightly below the middle of the Zone, immediately overlain by an acme of ''M. dixoni'' in a hard limestone band ('M3' of Gale, 1989, also known as the Dixoni Limestone). Locally (eg. Leighton Buzzard district) the Dixoni Limestone is also characterised by common ''I. virgatus''. Just above the Dixoni Limestone, at about the middle of the ''M. dixoni'' Zone, there is an acme of ''Orbirhynchia'' ''mantelliana'', representing the lowest of three widely occurring acmes of this brachiopod in the Cenomanian (Gale, 1989, 1995; Robaszynski ''et al''., 1998). | '''Bio-markers''': An acme of ''Inoceramus virgatus'' occurs slightly below the middle of the Zone, immediately overlain by an acme of ''M. dixoni'' in a hard limestone band ('M3' of Gale, 1989, also known as the Dixoni Limestone). Locally (eg. Leighton Buzzard district) the Dixoni Limestone is also characterised by common ''I. virgatus''. Just above the Dixoni Limestone, at about the middle of the ''M. dixoni'' Zone, there is an acme of ''Orbirhynchia'' ''mantelliana'', representing the lowest of three widely occurring acmes of this brachiopod in the Cenomanian (Gale, 1989, 1995; Robaszynski ''et al''., 1998). | ||
'''Subzones''': None formally recognised in the UK. Gale (1995) recognised three faunal assemblages, successively comprising: (a) common ''M. dixoni'' and ''M. saxbii'', with acme of ''Inoceramus virgatus''; (b) diverse turrilitids, including ''Mesoturrilites'' spp.; (c) diverse ''Mantelliceras'' and rarer ''Acompsoceras'' and ''Hyphoplites''. | '''Subzones''': None formally recognised in the UK. Gale (1995) recognised three faunal assemblages, successively comprising: (a) common ''M. dixoni'' and ''M. saxbii'', with acme of ''Inoceramus virgatus''; (b) diverse turrilitids, including ''Mesoturrilites'' spp.; (c) diverse ''Mantelliceras'' and rarer ''Acompsoceras'' and ''Hyphoplites''. | ||
'''Age''': Early Cenomanian | '''Age''': Early Cenomanian | ||
[[category:Standard zonation | 005]] | [[category:Standard zonation | 005]] | ||
Latest revision as of 12:36, 26 September 2013
Base: The base of the M. dixoni Zone is immediately below the first occurrence of the index species (Gale, 1995).
Top: The top of the M. dixoni Zone is immediately below the first occurrence of the ammonite Cunningtoniceras inerme (Gale, 1995).
Range of index species: The index species is restricted to the lower part of the M. dixoni Zone (Robaszynski et al., 1998).
Key Fauna:
| Brachiopoda: | Orbirhynchia mantelliana |
| Bivalvia: | Inoceramus virgatus |
| Ammonoidea: | Acompsoceras spp. |
| Hyphoplites spp. | |
| Mantelliceras dixoni | |
| M. saxbii | |
| M. spp. | |
| Mesoturrilites spp. |
Faunal abundance & preservation: Some fauna present as acmes (O. mantelliana, I. virgatus), and M. dixoni is locally abundant in a hard limestone bed (see: Bio-markers).
Bio-markers: An acme of Inoceramus virgatus occurs slightly below the middle of the Zone, immediately overlain by an acme of M. dixoni in a hard limestone band ('M3' of Gale, 1989, also known as the Dixoni Limestone). Locally (eg. Leighton Buzzard district) the Dixoni Limestone is also characterised by common I. virgatus. Just above the Dixoni Limestone, at about the middle of the M. dixoni Zone, there is an acme of Orbirhynchia mantelliana, representing the lowest of three widely occurring acmes of this brachiopod in the Cenomanian (Gale, 1989, 1995; Robaszynski et al., 1998).
Subzones: None formally recognised in the UK. Gale (1995) recognised three faunal assemblages, successively comprising: (a) common M. dixoni and M. saxbii, with acme of Inoceramus virgatus; (b) diverse turrilitids, including Mesoturrilites spp.; (c) diverse Mantelliceras and rarer Acompsoceras and Hyphoplites.
Age: Early Cenomanian