HOW SYNCHRONOUS ARE NEOGENE MARINE PLANKTON EVENTS

Citation
C. Spencercervato et al., HOW SYNCHRONOUS ARE NEOGENE MARINE PLANKTON EVENTS, Paleoceanography, 9(5), 1994, pp. 739-763
Citations number
73
Categorie Soggetti
Paleontology,Oceanografhy,Geology
Journal title
ISSN journal
08838305
Volume
9
Issue
5
Year of publication
1994
Pages
739 - 763
Database
ISI
SICI code
0883-8305(1994)9:5<739:HSANMP>2.0.ZU;2-B
Abstract
We analyzed the synchrony and diachrony of commonly used Neogene biost ratigraphic events from data published in the Initial Reports of the D eep Sea Drilling Project (DSDP) and in the Proceedings of the Ocean Dr illing Program (ODP). On the basis of the combined biostratigraphic an d magnetostratigraphic evidence, new Neogene age models were construct ed for 35 globally distributed DSDP and ODP holes. Biostratigraphic ev ents from the four major plankton groups (calcareous nannofossils, dia toms, planktonic foraminifera, and radiolarians) were compiled from DS DP and ODP reports. After the elimination of possible sources of error such as stratigraphic hiatuses and reworking of specimens, 124 biostr atigraphic events that occurred in at least four holes were analyzed i n detail: for each event a biochronologic age estimate was derived by projection of the depth of the event onto the line of correlation of e ach hole, and from these a global mean age for each event was calculat ed, together with its standard deviation. Average standard deviations for event ages by fossil group are: calcareous nannofossil first appea rance datums (FADs): 0.57 m.y. (21 events), calcareous nannofossil las t appearance datums (LADs): 0.60 m.y. (25 events), diatom FADs: 0.57 m .y. (7 events), diatom LADs: 0.85 m.y. (14 events), planktonic foramin ifera FADs: 0.88 m.y. (22 events), foraminifera LADs: 0.68 m.y. (16 ev ents), radiolarian FADs: 0.30 m.y. (9 events), radiolarian LADs: 0.31 m.y. (10 events). Since the average sample spacing in the sites used f or this analysis is only 0.185 m.y., we have examined the data for tru e patterns of diachrony and for other biases. Diachrony is more freque nt among cosmopolitan than among endemic taxa, thus there is a general trade-off between the obtainable age precision and the geographic ext ent of a bioevent. Precision of age calibrations also decreases with i ncreasing age. Although some of these features may be due to investiga tor bias, they appear in part to be real phenomena, and thus could als o provide opportunities for further exploration of important paleobiol ogical processes, such as change in environmental gradients through ti me, evolutionary adaptation of species populations and migration due t o water mass changes.