Mid-Pleistocene Extinction of Deep-Sea Ostracoda?
Degree GrantorUniversity of Canterbury
Degree NameMaster of Science
A global extinction event has been documented in protozoan foraminifera in the late Pliocene to Pleistocene. The timing of the extinction event varied depending on location, however for Ocean Drilling Project Site 1125, disappearances occurred between 2.5 and 0.57 Ma, with the major decline approximately 1.1 Ma. In order to determine if this event affected benthic organisms other than protozoans, this study was undertaken to determine how podocopid ostracods (Crustacea) recovered Ocean Drilling Program Site 1125 responded. The present study was hindered by the small number of valves recovered; the fact that a large proportion of taxa found were undescribed and new to science; and the current state of taxonomic scheme that is under significant revision. These factors meant that a comprehensive comparison could not be achieved. Despite this, counts of ostracod valves and assessments of diversity from this study reveal a significant increase in both parameters from approximately 900-600 ka. Three possible causes were investigated to account for this increase, sediment type and sample size; affects of taphonomy, mainly dissolution; or an actual biotic 'event'. Statistical analyses showed that although sample size did have some effect, it was not the sole reason for the increase in ostracod numbers. Dissolution had an expected affect on the percentage of juveniles but no correlations were found with other sample characteristics. Sedimentation rate was investigated but this also proved unrelated. Therefore, it is suggested that the increase in total ostracod valves and diversity which occurs between 900 and 600 ka was in fact a natural, biotic 'event'. This preliminary evidence suggests that an oceanographic event that has negatively impacted on the foraminifers has had the reverse affect on the ostracod assemblage, in the sense that both population size and diversity increase during that time.