| Popis: |
Ostracod assemblages from samples collected through the Turonian Stage of the Late Cretaceous from Dover, Kent, south-east England, consist of one hundred and three species group taxa. These are described and illustrated. This represents a significant increase in the knowledge of the Turonian fauna, since previous estimates of the number of species present during the Turonian are less than thirty. This improvement has been brought about by the selection of an appropriate processing method. Freeze-thaw processing is recommended for chalks and hardgrounds which comprise much of the Turonian Stage. The white spirit, solvent method is shown to be preferable for marls. Nineteen species and six subspecies are here described as new: Polycope lunaplena sp. nov, Cytherella truncatoides sp. nov., Cytherella vulna sp. nov., Cytherella weaveri sp. nov., Cytherelloidea granulosa parca ssp. nov., Cardobairdia longitecta sp. nov., Bairdoppilata turonica sp. nov., Pontocyprella robusta cometa ssp. nov., Pterygocythereis (Diogmopteron) carolinae sp. nov., Bythoceratina (Bythoceratina) saxa sp. nov., Bythoceratina (Bythoceratina) staringi conmacula ssp. nov., Monoceratina minangulata sp. nov., Patellacythere weaveris sp. nov., Schulerides langdonensis sp. nov., Karsteneis nodifera tabasca ssp. nov., Karsteneis oculocosta sp. nov., Karsteneis petasus petasus sp. et ssp. nov., Karsteneis petasus antecursor sp. et ssp. nov., Karsteneis praekarsteni sp. nov., Idiocythere carburnensis sp. nov., Isocythereis postelongata sp. nov., Mauritsina? paradordoniensis sp. nov., Rehacythereis stellatus sp. nov., Rehacythereis venticursus venticursus sp. et ssp. nov., Rehacythereis venticursus patbrowni sp. et ssp. nov., and one new name, Bythoceratina (Bythocertatina) antetumida nom. nov. is introduced for a secondary junior homonym. By comparison with faunas from Devon and the Czech Republic, the biostratigraphical analysis is shown to only have only local significance due to diachronism of Ostracoda. This diachronism is used to explore migration pathways which suggest that the origin of the Turonian ostracod fauna may have had more than one source. A model relating ostracod diversity inversely to sea-level is given for the Cenomanian to Santonian stages of the Late Cretaceous which suggests that the sea-level at Dover during the Turonian was greater than previously thought, given its marginal setting. |
