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.