Gastvortrag

Prof. Bridget Wade (ECORD Distinguished Lecturer,De­partment of Earth Sci­ences, Uni­versity Col­lege Lon­don)

De­term­in­ing past ocean­o­graphic change of­ten in­volves or­ganic or in­or­ganic geo­chem­ical prox­ies, however, there is a wealth of in­form­a­tion avail­able from ex­amin­ing al­ter­a­tions in the as­semblages of mar­ine bi­ota. Mi­cro­scopic fossils (fo­raminifera, nan­no­fossil, di­at­oms, ra­diolari­ans) are abund­ant in deep sea sed­i­ments and can provide a re­cord of pa­leocean­o­graphic change. Mar­ine cores from the In­ter­na­tional Ocean Dis­cov­ery Pro­gram and its pre­de­cessors al­lows ex­am­in­a­tion of how dif­fer­ent groups re­spon­ded through time, and in par­tic­u­lar their re­ac­tion at cli­matic per­turb­a­tions. Changes in the mar­ine bi­ota may in­volve the ex­tinc­tion of spe­cies or groups of spe­cies that can tell us about al­ter­a­tions in their hab­itat. It can also com­prise the en­hanced abund­ance of a par­tic­u­lar spe­cies, or a group, for a short in­ter­val of time (acme events). The dwarf­ing of or­gan­isms is in­creas­ingly be­com­ing re­cog­nised as a re­sponse to en­vir­on­mental stress, however, I will show sev­eral in­ter­vals in the Ceno­zoic where a spe­cies be­came much lar­ger for a short in­ter­val of time. Dif­fer­ent plank­ton groups re­spond in dif­fer­ent ways. For ex­ample, a ma­jor turnover in both cal­careous (plank­tonic fo­raminifera) and sili­ceous (ra­diolari­ans) zo­oplank­ton oc­curred at the middle/?late Eo­cene bound­ary about 38 Ma. New ana­lysis of the nan­no­fossil as­semblages in­dic­ates a re­l­at­ively muted re­sponse, and demon­strates the con­trast­ing sens­it­iv­ity to en­vir­on­mental change in these plank­ton groups. This talk fo­cuses on Ceno­zoic ocean drilling re­cords where the mar­ine mi­cro­fossils re­spond in some­times mys­ter­i­ous ways, with par­tic­u­lar fo­cus on the Eo­cene, Oli­go­cene and Mio­cene.